BSI 21/30441324 DC:2021 Edition
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BS ISO/IEC 80079-49. Flame arresters – Part 49. Performance requirements, test methods and limits for use
| Published By | Publication Date | Number of Pages |
| BSI | 2021 | 65 |
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| 3 | 31M/162/CD COMMITTEE DRAFT (CD) Project number: ISO/IEC 80079-49 ED1 Date of circulation: Closing date for comments: 2021-07-16 2021-10-08 Supersedes documents: 31M/155/NP, 31M/158/RVN IEC SC 31M : Non-electrical equipment and protective systems for explosive atmospheres Secretariat: Secretary: Germany Mrs Anke Sachtleben Of interest to the following committees: Proposed horizontal standard: TC 31 Other TC/SCs are requested to indicate their interest, if any, in this CD to the secretary. Functions concerned: EMC Environment Quality assurance Safety This document is still under study and subject to change. It should not be used for reference purposes. Recipients of this document are invited to submit, with their comments, notification of any relevant patent rights of which they are aware and to provide supporting documentation. Title: Flame arresters — Performance requirements, test methods and limits for use Note from TC/SC officers: HORIZONTAL_STD FUNCTION_EMC FUNCTION_ENV FUNCTION_QUA FUNCTION_SAFETY |
| 4 | CONTENTS FOREWORD 5 INTRODUCTION 7 1 Scope 8 2 Normative references 8 3 Terms and definitions 8 4 Abbreviated terms and symbols 12 5 Hazards and flame arrester classifications 13 5.1 Flame transmission classification: deflagration, stable and unstable detonation 13 5.2 Flame transmission classification: stabilized burning 14 5.3 Index of tests 14 6 General requirements 15 6.1 Measuring instruments 15 6.2 Flow measurement (air) 15 6.3 Flame transmission test 16 6.3.1 General 16 6.3.2 Test mixtures 16 7 Specific requirements for static flame arresters 18 7.1 Construction requirements for prototype arresters 18 7.2 Design series 18 7.3 Flame transmission test 19 7.3.1 General 19 7.3.2 Deflagration test 19 7.3.3 Detonation test 23 7.3.4 Short time burning test 28 7.3.5 Endurance burning test 31 7.3.6 In-line flame arrester 32 7.3.7 Pre-volume flame arrester 33 7.3.8 Detonation flame arrester 33 7.3.9 Short time burn flame arresters 33 8 Specific requirements for liquid product detonation flame arresters 34 8.1 Liquid seals 34 8.2 Foot valves 34 8.3 Flame transmission test 35 9 Specific requirements for dynamic flame arresters (high velocity vent valves) 36 9.1 General 36 9.2 Flame transmission tests 37 9.2.1 Low flow flame transmission test 37 9.2.2 Flame transmission test by opening and closing 38 9.2.3 Deflagration test 39 9.2.4 Endurance burning test 39 10 Specific requirements for hydraulic flame arresters 40 10.1 Equipment 40 10.2 Flame transmission test 40 10.2.1 General 40 |
| 5 | 10.2.2 Short time burning test 40 10.2.3 Deflagration test 40 10.2.4 Detonation test 41 11 Test of flame arresters installed on or within gas conveying equipment 43 11.1 General 43 11.2 Flame transmission test 43 11.2.1 General 43 11.2.2 Test procedure for gas conveying equipment with inlet pressure > 600 hPa 45 11.2.3 Test procedure for gas conveying equipment with inlet pressure ≤ 600 hPa 46 12 Instructions 46 13 Marking 47 13.1 Location 47 13.2 Flame arrester housing 47 13.2.1 General information 47 13.2.2 Warning markings 48 13.2.3 Examples of marking 49 13.3 Flame arrester element 49 14 Manufacturing and production 49 14.1 Construction 49 14.2 Housing 50 14.3 Joints 50 14.4 Pressure test 50 14.5 Leak test 50 Annex A (normative) Flow measurement 51 A.1 General 51 A.2 In-line flame arresters 51 A.3 End-of-line flame arrester 52 A.3.1 General 52 A.3.2 Special flow measurement for dynamic flame arresters 52 A.4 Undamped oscillation tests of dynamic flame arrester (High velocity vent valves) 53 Annex B (informative) Information for selecting flame arresters 55 Annex C (informative) Best practice 56 Annex D (informative) Evaluation of test results 57 Annex E (normative) Application 58 E.1 General 58 E.2 Limits for use for static flame arresters 58 E.2.1 In-line flame arrester 58 E.2.2 Pre-volume flame arrester 59 E.2.3 Detonation flame arrester 59 E.2.4 Short time burn flame arrester 59 E.3 Limits for use for liquid detonation flame arresters 60 E.4 Limits for use for dynamic flame arresters (high velocity vent valves) 60 E.5 Limits for use for hydraulic flame arresters 60 Bibliography 63 |
| 6 | Figure 1 – Test apparatus for end-of-line flame arrester for deflagration test 20 Figure 2 – Test apparatus for in-line flame arrester for deflagration test 21 Figure 3 – Test apparatus for pre-volume flame arrester for deflagration test 22 Figure 4 – Test apparatus for detonation flame arrester for detonation without restriction 24 Figure 5 – Test apparatus for detonation flame arrester for detonation with restriction 26 Figure 6 – Test apparatus for short time burning test 29 Figure 7 – Test apparatus for endurance burning test 31 Figure 8 – Liquid product detonation flame arrester 34 Figure 9 – End-of-line flame arrester incorporating a non-return valve (foot valve) 35 Figure 10 – Test apparatus for liquid product detonation flame arresters 36 Figure 11 – Test apparatus for determining the non-hammering conditions for dynamic flame arresters 38 Figure 12 – Test apparatus for hydraulic flame arresters 42 Figure 13 – Test apparatus for the flame transmission test of flame arresters installed on or within gas conveying equipment 44 Figure 14 – Example of marking plate, burn rating “a” 49 Figure 15 – Example of marking plate, burn rating “b” 49 Figure A.1 – Test apparatus for recording the pressure drop/flow rate curve for in-line flame arresters 52 Figure A.2 – Test apparatus for recording the pressure drop/flow rate curve for end-of-line flame arresters with or without integrated pressure and/or vacuum valve 53 Figure A.3 – Test apparatus for determining the non-oscillating conditions for dynamic flame arresters 54 Figure D.1 – Decision process for stable detonation arrester (DET3 and DET4) 57 Figure D.2 – Decision process for unstable detonation arrester (DET1 and DET2) 57 Figure E.1 – Test apparatus for hydraulic flame arresters 62 Table 1 – Flame arrester classification for deflagration, stable and unstable detonation 14 Table 2 – Summary of tests to be conducted 14 Table 3 – Specification of gas-air mixtures for deflagration and detonation tests 17 Table 4 – Specification of gas-air mixtures for short time burning tests and burning tests of dynamic flame arresters 17 Table 5 – Specification of gas-air or vapour-air mixtures for endurance burning tests of static flame arresters 17 Table 6 – Design series 19 Table 7 – Ratio pmd/pTB 25 Table 8 – Number of the individual tests and test parameters for the flame transmission test of flame arresters installed on or within gas conveying equipment with inlet pressures > 600 hPa 45 Table 9 – Number of the individual tests and test parameters for the flame transmission test of flame arresters installed on or within gas conveying equipment with inlet pressures ≤ 600 hPa 46 Table B.1 – Information for selecting flame arresters 55 |
| 7 | INTERNATIONAL ELECTROTECHNICAL COMMISSION ____________ FLAME ARRESTERS — PERFORMANCE REQUIREMENTS, TEST METHODS AND LIMITS FOR USE FOREWORD 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with may participate in this preparatory work. International, governmental and non-governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for Standardization (ISO) in accordance with conditions determined by agreement between the two organizations. 2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international consensus of opinion on the relevant subjects since each technical committee has representation from all interested IEC National Committees. 3) IEC Publications have the form of recommendations for international use and are accepted by IEC National Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any misinterpretation by any end user. 4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications transparently to the maximum extent possible in their national and regional publications. Any divergence between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter. 5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any services carried out by independent certification bodies. 6) All users should ensure that they have the latest edition of this publication. 7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and members of its technical committees and IEC National Committees for any personal injury, property damage or other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC Publications. 8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is indispensable for the correct application of this publication. 9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent rights. IEC shall not be held responsible for identifying any or all such patent rights. International Standard ISO 80079-49 has been prepared by IEC sub-committee 31M: Non-electrical equipment and protective systems for explosive atmospheres. This edition cancels and replaces ISO 16852:2016, which has been technically revised. This edition includes the following significant technical changes with respect to the previous edition: a) adaptation of the relevant IEC TC 31 requirements on standards; b) addition of a definition for stable detonation shock wave; c) clarification of the conditions and requirements for flame arresters whose intended operating conditions are outside the atmospheric conditions in clauses 7.3.4 and 7.3.5; d) clarification of the requirements on the information for use in clause 12.1 indent f concerning the burn time; |
| 8 | e) addition of a permission to the construction requirements both in clause 7.1 and 13.1 to substitute visual inspection by performing a flow test; f) addition of a flow chart for the evaluation of test results as Annex D. |
| 9 | INTRODUCTION Flame arresters are safety devices fitted to openings of enclosures or to pipe work and are intended to allow flow but prevent flame transmission. They have widely been used for decades in the chemical and oil industry, and a variety of national standards is available. This International Standard was prepared by an international group of experts, whose aim was to establish an international basis by harmonizing and incorporating recent national developments and standards as far as reasonable. This International Standard addresses manufacturers (performance requirements) and test institutes (test methods), as well as customers (limits for use). Only relatively general performance requirements are specified and these are kept to a strict minimum. Experience has shown that excessively specific requirements in this field often create unjustified restrictions and prevent innovative solutions. The hazard identification of common applications found in industry leads to the specification of the test methods. These test methods reflect standard practical situations and, as such, form the heart of this International Standard because they also allow classification of the various types of flame arresters and then determination of the limits of use. A considerable number of test methods and test conditions had to be taken into account for two main reasons. a) Different types of flame arresters are covered with respect to the operating principle (static, hydraulic, liquid, dynamic) and each type clearly needs its specific test set-up and test procedure. b) It is necessary to adapt flame arresters to the special conditions of application (gas, installation) because of the conflicting demands of high flame quenching capability and low pressure loss; this situation is completely different from the otherwise similar principle of protection by flameproof enclosure (of electrical equipment), where the importance of process gas flow through gaps is negligible; importance being placed on the flame quenching effect of the gap. Consequently, in this International Standard, the testing and classification related to the gas groups and the installation conditions have been subdivided more than is usually the case. In particular, explosion group IIA is subdivided into sub-groups IIA1 and IIA, explosion group IIB is subdivided into sub-groups IIB1, IIB2, IIB3 and IIB, and the type “detonation arrester” is divided into four sub-types, which take into account specific installation situations. The test conditions lead to the limits for use which are most important for the customer. This International Standard specifies this safety relevant information and its dissemination through the manufacturer’s written instructions for use and the marking of the flame arresters. The limits for use are also a link to more general (operational) safety considerations and regulations, which remain the responsibility of national or corporate authorities. Annex B and Annex C offer some guidance in this field. |
| 10 | EXPLOSIVE ATMOSPHERES – PART 49: FLAME ARRESTERS — PERFORMANCE REQUIREMENTS, TEST METHODS AND LIMITS FOR USE 1 Scope This International Standard specifies the requirements for flame arresters that prevent flame transmission when explosive gas-air or vapour-air mixtures are present. It establishes uniform principles for the classification, basic construction and information for use, including the marking of flame arresters, and specifies test methods to verify the safety requirements and determine safe limits of use. This International Standard is valid for pressures ranging from 80 kPa to 160 kPa and temperatures ranging from −20 °C to +150 °C. NOTE 1 For flame arresters with operational conditions inside the scope, but outside atmospheric conditions, see Annex E. NOTE 2 In designing and testing flame arresters for operation under conditions other than those specified above, this International Standard can be used as a guide. However, additional testing related specifically to the intended conditions of use is advisable. This is particularly important when high temperatures and pressures are applied. The test mixtures might need to be modified in these cases. This International Standard is not applicable to the following: external safety-related measurement and control equipment that might be required to keep the operational conditions within the established safe limits; NOTE 3 Integrated measurement and control equipment, such as integrated temperature and flame sensors as well as parts which, for example, intentionally melt (retaining pin), burn away (weather hoods) or bend (bimetallic strips), is within the scope of this International Standard. flame arresters used for explosive mixtures of vapours and gases, which tend to self-decompose (e.g. acetylene) or which are chemically unstable; flame arresters used for carbon disulphide, due to its special properties; flame arresters whose intended use is for mixtures other than gas-air or vapour-air mixtures (e.g. higher oxygen-nitrogen ratio, chlorine as oxidant, etc.); flame arrester test procedures for reciprocating internal combustion engines NOTE 4 This includes the design requirements but excludes as installed testing; fast acting valves, extinguishing systems and other explosion isolating systems. 2 Normative references The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO/IEC 80079201, Explosive atmospheres — Part 201: Material characteristics for gas and vapour classification — Test methods and data IEC 60079–0, Explosive atmospheres — Part 0: Equipment – General requirements IEC 60079–1, Explosive atmospheres — Part 1: Equipment protection by flameproof enclosures “d” |
| 11 | 3 Terms and definitions For the purposes of this document, the terms and definitions given in IEC 60079-0 and the following apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: IEC Electropedia: available at http://www.electropedia.org/ ISO Online browsing platform: available at http://www.iso.org/obp flame arrester device fitted to the opening of an enclosure, or to the connecting pipe work of a system of enclosures, and whose intended function is to allow flow but prevent the transmission of flame housing portion of a flame arrester (3.1) whose principal function is to provide a suitable enclosure for the flame arrester element (3.3) and allow mechanical connections to other systems flame arrester element portion of a flame arrester (3.1) whose principal function is to prevent flame transmission stabilized burning steady burning of a flame stabilized at, or close to, the flame arrester element (3.3) short time burning stabilized burning (3.4) for a specified time endurance burning stabilized burning (3.4) for an unlimited time explosion abrupt oxidation or decomposition reaction producing an increase in temperature, pressure, or both simultaneously [SOURCE: ISO 84211:1987, 1.13] deflagration explosion (3.7) propagating at subsonic velocity [SOURCE: ISO 84211:1987, 1.11] detonation explosion (3.7) propagating at supersonic velocity and characterized by a shock wave [SOURCE: ISO 84211:1987, 1.12] page_11 |
| 12 | stable detonation detonation (3.9) progressing through a confined system without significant variation of velocity and pressure characteristics Note 1 to entry: For the atmospheric conditions, test mixtures and test procedures of this International Standard, typical velocities range between 1 600 m/s and 2 200 m/s. unstable detonation detonation (3.9) during the transition of a combustion process from a deflagration (3.8) into a stable detonation (3.10) Note 1 to entry: The transition occurs in a limited spatial zone, where the velocity of the combustion wave is not constant and where the explosion pressure is significantly higher than in a stable detonation. The position of this transition zone depends, amongst other factors, on pipe diameter, pipe configuration, test gas and explosion group. Note 2 to entry: An unstable detonation presents a higher level of hazard than a stable detonation due to higher flame speeds and pressures. 3.12 Characteristic safety data of explosive mixtures 3.12.1 maximum experimental safe gap MESG maximum gap of a joint of 25 mm in width which prevents any transmission of an explosion during tests made according to ISO/IEC 80079201 3.12.2 explosion group Ex.G ranking of flammable gas-air mixtures with respect to the MESG Note 1 to entry: See Table 3, columns 1 and 2. 3.13 bi-directional flame arrester flame arrester (3.1) that prevents flame transmission from both sides 3.14 deflagration flame arrester DEF flame arrester (3.1) designed to prevent the transmission of a deflagration (3.8) Note 1 to entry: It can be an end-of-line flame arrester (3.21) or an in-line flame arrester (3.22). 3.15 detonation flame arrester DET flame arrester (3.1) designed to prevent the transmission of a detonation Note 1 to entry: It can be an end-of-line flame arrester (3.21) or an in-line flame arrester (3.22), and can be used for both stable detonations (3.10) and unstable detonations (3.11). 3.16 endurance flame arrester flame arrester (3.1) that prevents flame transmission during and after endurance burning (3.6) 3.17 static flame arrester flame arrester (3.1) designed to prevent flame transmission by quenching gaps page_12 |
| 13 | 3.17.1 measurable type flame arrester (3.1) where the quenching gaps of the flame arrester element (3.3) can be technically drawn, measured and controlled 3.17.2 non-measurable type flame arrester (3.1) where the quenching gaps of the flame arrester element (3.3) cannot be technically drawn, measured or controlled EXAMPLE Random structures such as knitted mesh, sintered materials and gravel beds. 3.18 dynamic flame arrester high velocity vent valve deflagration proof (see 3.14) pressure relief valve designed always to have efflux velocities that prevent the flame propagation against the flow direction Note 1 to entry: It can be endurance burn proof (see 3.16). 3.19 liquid product detonation flame arrester flame arrester (3.1) in which the liquid product is used to form a liquid seal as a flame arrester medium, in order to prevent flame transmission of a detonation Note 1 to entry: There are two types of liquid product detonation flame arrester for use in liquid product lines: liquid seals and foot valves. 3.19.1 liquid seal flame arrester flame arrester (3.1) designed to use the liquid product to form a barrier to flame transmission 3.19.2 foot valve flame arrester flame arrester (3.1) designed to use the liquid product combined with a non-return valve to form a barrier to flame transmission 3.20 hydraulic flame arrester flame arrester (3.1) designed to break the flow of an explosive mixture into discrete bubbles in a water column, thus preventing flame transmission 3.21 end-of-line flame arrester flame arrester (3.1) that is fitted with one pipe connection only 3.22 in-line flame arrester flame arrester (3.1) that is fitted with two pipe connections, one on each side of the flame arrester 3.23 pre-volume flame arrester VDEF flame arrester (3.1) that, after ignition by an internal ignition source, prevents flame transmission from inside an explosion-pressure-resistant containment (e.g. a vessel or closed pipe work) to the outside, or into the connecting pipe work Note 1 to entry: Explosion-pressure resistance is a property of vessels and equipment designed to withstand the expected explosion pressure without becoming permanently deformed. page_13 |
| 14 | 3.24 integrated temperature sensor temperature sensor integrated into the flame arrester, as specified by the manufacturer of the flame arrester, in order to provide a signal suitable to activate counter measures 4 Abbreviated terms and symbols A0 free area of a static flame arrester element Ap nominal cross sectional area of the flame arrester connection At cross sectional area on the unprotected side of the flame arrester element Au effective open area of the flame arrester element on the protected side pipe diameter DM minimum diameter of the pipe on the protected side of a dynamic flame arrester LM maximum length without undamped oscillations Lm pipe length upstream of the dynamic flame arrester used in flame transmission test Lp pipe length on the protected side Lr pipe length between flame arrester and restriction Lu pipe length on the unprotected side, maximum allowable run-up length for installation L1, L2, L3, L4 pipe lengths in the flow test pmd time average value of the detonation pressure in the time interval of 200 μs after arrival of the detonation shock wave pmu maximum time average value of the transient pressure of an unstable detonation over a time interval of 200 μs pt pressure in the pressure test pT pressure in the flow test of an end-of-line flame arrester pTB pressure before ignition p0 maximum operational pressure p pressure drop in the flow test of an in-line flame arrester pE maximum pressure for the endurance burning test of dynamic flame arresters pm pressure which cause the maximum temperature at endurance burning test RA ratio of the effective open area of the flame arrester element to pipe cross sectional area RU ratio of the free volume of the flame arrester element to the whole volume tBT burning time page_14 |
| 15 | tPpeak time at which the peak pressure correlating to the leading shock front is achieved in the test TTB temperature of the flame arrester before ignition T0 maximum operational temperature of the flame arrester vmax maximum flow velocity during the volume flow-pressure drop measurement (flow test) vmin minimum flow velocity during the volume flow-pressure drop measurement (flow test) volume flow rate critical volume flow rate flow rate at closing point of dynamic flame arresters minimum volume flow rate for endurance burning on dynamic flame arresters maximum volume flow rate for endurance burning on dynamic flame arresters maximum volume flow rate for dynamic flame arresters at the set pressure volume flow rate leading to maximum temperature minimum volume in the protected tank safe volume flow rate safe volume flow rate including a safety margin maximum volume flow rate leading to flame transmission ZRmin minimum water seal immersion depth at rest above the outlet openings of the immersion tubes ZR immersion depth at rest, corresponding to ZRmin plus the manufacturer’s recommended safety margin Z0min minimum operational water seal immersion depth when the mixture flow displaces the water from the immersion tubes, where Z0min > ZRmin Z0 operational immersion depth, corresponding to Z0min plus the manufacturer’s recommended safety margin All pressure values are absolute pressures. NOTE Symbols in the figures for the flame arrester are in line with ISO 146177. 5 Hazards and flame arrester classifications 5.1 Flame transmission classification: deflagration, stable and unstable detonation The ignition of an explosive mixture will initiate a deflagration. A flame arrester covering only this hazard is classified as a deflagration flame arrester. MTBlankEqn page_15 |
| 16 | NOTE 1 A deflagration when confined in a pipe will usually accelerate, and can undergo transition through an unstable to a stable detonation provided sufficient pipe length is available. This pipe length will vary depending upon the initial conditions of the mixture and the pipe work configuration. A flame arrester tested in accordance with 7.3.3.2 or 7.3.3.3 is classified as a stable detonation flame arrester and is suitable for deflagrations and stable detonations. NOTE 2 Unstable detonations are a specific hazard requiring higher performance flame arresters than for stable detonations. A flame arrester tested in accordance with 7.3.3.4 or 7.3.3.5 is classified as an unstable detonation flame arrester and is suitable for deflagrations, stable detonations and unstable detonations. The specific hazards covered by this International Standard, the classification and the testing required for the appropriate flame arrester are listed in Table 1. Table 1 – Flame arrester classification for deflagration, stable and unstable detonation Application Flame arrester classification a) unconfined deflagration into an enclosure or vessel end-of-line deflagration b) confined deflagration propagating along a pipe into connecting pipe work in-line deflagration c) deflagration confined by an enclosure or pipe work to the outside atmosphere or into connecting apparatus pre-volume deflagration d) stable detonation propagating along a pipe into connecting pipe work in-line stable detonation e) unstable detonation propagating along a pipe into connecting pipe work in-line unstable detonation f) stable detonation at the end of a pipe propagating into an enclosure or vessel end-of-line stable detonation 5.2 Flame transmission classification: stabilized burning Stabilized burning after ignition creates additional hazards in applications where there could be a continuous flow of the explosive mixture towards the unprotected side of the flame arrester. The following situations shall be taken into account: if the flow of the explosive mixture can be stopped within a specific time that is between 1 min and 30 min, flame arresters which, when tested in accordance with 7.3.4, prevent flame transmission during that period of stabilized burning are suitable for that hazard, and they are classified as safe against short time burning; NOTE Bypassing, sufficient diluting or inerting are measures equivalent to stopping the flow. if the flow of the explosive mixture cannot be stopped or, for operational reasons, is not intended to be stopped within 30 min, flame arresters which, when tested in accordance with 7.3.5, prevent flame transmission for this type of stabilized burning are suitable for that hazard, and they are classified as safe against endurance burning. 5.3 Index of tests Flame arresters shall be tested to the specific explosion group of the explosive gas-air or vapour-air mixture (see Table 3, columns 1 and 2). The tests to be conducted are given in Table 2. page_16 |
| 17 | Table 2 – Summary of tests to be conducted Type of flame arrester Flame transmission test Burning test Flow test End-of-line deflagration flame arrester (DEF) short time burn proof 7.3.2.1 7.3.4 A.3 endurance burn proof 7.3.5 No stabilised burn rating — In-line deflagration flame arrester (DEF) short time burn proof 7.3.2.2 7.3.4 A.2 endurance burn proof 7.3.5 No stabilised burn rating — Pre-volume flame arrester (VDEF) No stabilised burn rating 7.3.2.3 — A.2 or A.3 Stable detonation flame arrester without restriction (DET4) short time burn proof 7.3.3.2 7.3.4 A.2 endurance burn proof 7.3.5 No stabilised burn rating — Stable detonation flame arrester with restriction (DET3) short time burn proof 7.3.3.3 7.3.4 A.2 endurance burn proof 7.3.5 No stabilised burn rating — Unstable detonation flame arrester without restriction (DET2) short time burn proof 7.3.3.4 7.3.4 A.2 endurance burn proof 7.3.5 No stabilised burn rating — Unstable detonation flame arrester with restriction (DET1) short time burn proof 7.3.3.5 7.3.4 A.2 endurance burn proof 7.3.5 No stabilised burn rating — Liquid product detonation flame arrester (DET4) No stabilised burn rating 8.3 — — Dynamic flame arrester (high velocity vent valve) (DEF) deflagration proof 9.2.1, 9.2.2 and 9.2.3 — A.3.2 and A.4 endurance burn proof 9.2.4 Hydraulic flame arrester (DET4) Short time burn proof 10.2.3, 10.2.4 10.2.2 — 6 General requirements 6.1 Measuring instruments Appropriate metrological traceable calibrated measuring instruments shall be used for the tests. NOTE It is advisable that the uncertainty of measurement in the tests be such that it can be shown that all the required test parameter limits are met. 6.2 Flow measurement (air) The pressure drop across the flame arrester shall be tested before and after flame transmission tests at a volume flow that is suitable for identifying any alteration (deformation) of the flame arrester, particularly of the flame arrester element. After flame transmission testing, the pressure drop shall not differ by more than 20 % from the value measured at the same flow rate before that testing. After short time burn test and after endurance burn test, no additional flow measurement is required. |
| 18 | The flow capacity of in-line flame arresters shall be recorded in accordance with A.2 in a type test. The flow capacity of end-of-line flame arresters shall be recorded in accordance with A.3 in a type test. The flow capacity of end-of-line flame arresters directly combined with or integrated into pressure and/or vacuum valves shall be recorded in accordance with A.3 in a type test. Pressure and/or vacuum valves manufactured for different pressure settings shall be tested at the lowest and the highest set pressure and for intermediate set pressures ≤ 1 kPa apart. The flow capacity of dynamic flame arresters shall be recorded in accordance with A.3 in a type test. In addition, all dynamic flame arresters shall be tested for undamped oscillations in accordance with A.4 in a type test. 6.3 Flame transmission test 6.3.1 General All flame arresters shall be type tested against flame transmission. There shall be no permanent visible deformation of the housing. The tests shall be specific for the basic types of operation (as defined in 3.17, 3.18, 3.19 and 3.20) and shall be carried out in accordance with Clauses 7, 8, 9 or 10. One flame arrester shall be used throughout all deflagration or detonation flame transmission tests. No replacement parts or modifications shall be made to the flame arrester during these tests. Short time and endurance burning tests shall be carried out in the orientation to be used in service. Bi-directional flame arresters shall only be tested from one side if the protected and unprotected sides are identical. All flame transmission tests shall be carried out with gas-air mixtures at ambient temperatures. If operational temperature is higher than 60 °C, tests shall be carried out at the max. operational temperature or higher, with only the flame arrester being heated to the required temperature, TTB ≤ 150 °C. Gas-air or vapour-air mixtures shall be as specified in 6.3.2. For the purposes of this International Standard, explosion group IIC covers hydrogen and other gas-air or vapour-air mixtures with MESG less than 0,5 mm, and group IIB is divided into four sub-groups: IIB1, IIB2, IIB3 and IIB. Explosion group IIA is divided into two sub-groups: IIA1 and IIA. This International Standard covers deflagration and detonation tests for groups IIA, IIB1, IIB2, IIB3, IIB and IIC. Group IIA1 shall only be used for the testing of deflagration flame arresters. The limiting MESG values, which define the explosion groups IIA1, IIA, IIB1, IIB2, IIB3, IIB and IIC, are shown in Table 2. A flame arrester for a particular explosion group is suitable for explosive mixtures of another group having a greater MESG. 6.3.2 Test mixtures Table 3, Table 4 and Table 5 specify the mixtures for deflagration and detonation tests, short time burning and endurance burning tests. page_18 |
| 19 | Gas-air mixtures for testing shall be established with a concentration measuring instrument or a MESG test apparatus. Table 3 – Specification of gas-air mixtures for deflagration and detonation tests Range of application (marking) Requirements for test mixture Explosion group MESG of mixture mm Gas type Gas purity by volume % Gas in air by volumea % Safe gap of gas-air mixture mm IIA1 ≥ 1,14 Methane ≥ 98 8,4 ± 0,2 1,16 ± 0,02 IIAb > 0,90 Propane ≥ 95 4,2 ± 0,2 0,94 ± 0,02 IIB1b ≥ 0,85 Ethylene ≥ 98 5,2 ± 0,2 0,83 ± 0,02 IIB2b ≥ 0,75 5,7 ± 0,2 0,73 ± 0,02 IIB3b ≥ 0,65 6,6 ± 0,3 0,67 ± 0,02 IIBb ≥ 0,50 Hydrogen ≥ 99 45,0 ± 0,5 0,48 ± 0,02 IIC < 0,50 Hydrogen ≥ 99 28,5 ± 2,0 0,31 ± 0,02 NOTE The ranking in columns 1 and 2 is not comparable with the ranking in IEC 60079–1. a When the test gas mixture is measured by the safe gap of the gas-air mixture, the mixture shall be in the lower half of the specified gap range. If the test gas mixture is measured by the percentage of gas in air by volume, then for IIA1, IIA, IIB3 and IIC, the mixture shall be within the specified percentage volume range. For IIB1 and IIB2, the mixture shall be in the upper half side of the specified percentage volume range. For IIB, the mixture shall be on the lower half side of the specified percentage volume range. All the stated limit deviations relate to the uncertainty of the measuring equipment. b With small diameters, it may be difficult to generate stable detonations. Tests may be carried out using a gas-air mixture of a lower safe gap. Table 4 – Specification of gas-air mixtures for short time burning tests and burning tests of dynamic flame arresters Range of application (marking) Explosion group Requirements for test mixture Gas type Gas purity by volume % Gas in air by volumea % IIA1 Methane ≥ 98 9,5 ± 0,2 IIA Propane ≥ 95 4,2 ± 0,2 IIB1 Ethylene ≥ 98 6,6 ± 0,3 IIB2 IIB3 IIB IIC Hydrogen ≥ 99 28,5 ± 2,0 a Testing of dynamic flame arresters may require a variation in mixture composition. Table 5 – Specification of gas-air or vapour-air mixtures for endurance burning tests of static flame arresters Range of application (marking) Explosion groupa Requirements for test mixture Gas or liquid Purity by volume % Gas vapour in air by volume % IIA1 Methane ≥ 98 9,5 ± 0,2 page_19 |
| 20 | IIA Hexane ≥ 70 2,1 ± 0,1 IIB1 Ethylene ≥ 98 6,6 ± 0,3 IIB2 IIB3 IIB IIC Hydrogen ≥ 99 28,5 ± 2,0 a The combustion reactions of pure hydrocarbons are different to non-pure hydrocarbons (alcohols, amines, acids, ketones, aldehydes, etc.), therefore the range of applications is limited to pure hydrocarbons (compounds containing only carbon and hydrogen). 7 Specific requirements for static flame arresters 7.1 Construction requirements for prototype arresters Static flame arresters shall consist of a flame arrester element and a housing. For flame arrester elements with quenching gaps, the dimensions and tolerances shall be indicated (for example, gap length and width of gap). For crimped ribbon flame arrester elements used for the test, the gaps shall not fall below the upper tolerance limits over 90 % of the entire surface. The measurement of the gaps shall be done at a representative number of sample points. As an alternative to visual inspection, equivalent performance may be demonstrated by performing a flow test according to Annex A and comparing the results with a reference pressure drop curve provided by the manufacturer. The pressure drops shall not differ by more than 5 % at any place of the curve. NOTE The intention of this requirement is to cover the worst case scenario. 7.2 Design series Static flame arresters of similar design, except endurance burning and pre-volume flame arresters, may be grouped in a design series. The design series shall comply with the following: a) one drawing shall cover all nominal sizes in a design series and all parts shall be listed and dimensioned; b) the flame arrester elements shall have identical features of construction, specifically the quenching gaps. The length of the flame-quenching path may increase with the diameter, in which case all intermediate sizes in between tested sizes shall have the same flame-quenching path length as the larger tested size. Additional requirements for in-line flame arresters are the following: a design series is limited to a maximum of four consecutive nominal sizes according to Table 6, even if the intermediate sizes are not included in the design series; for every nominal size in a design series (maximum four), the ratio, RA, as calculated in Formula (1), shall not deviate by more than ±10 % from the ratio of the largest nominal size of the four members: page_20 page_21 |
| 21 | (1) Concentric and eccentric shaped housings form different design series. Table 6 – Design series Nominal size of connection mm Design series 10 to 15 20 to 25 32 to 40 50 65 80 100 125 150 200 250 300 350 400 450 500 600 700 800 900 1 000 7.3 Flame transmission test 7.3.1 General For non-measurable types of flame arresters, evidence shall be available to prove that the production flame arrester elements are equivalent in design, manufacture and construction to the test sample. The test pressure shall be at least 10 % higher than the maximum operational pressure, p0, of the flame arrester. Flame arresters with pressure and/or vacuum valve(s) integrated on the protected side shall have the valve secured in the fully open position, or the pressure and/or vacuum valve pallets shall be taken out during the test. Flame arresters with pressure and/or vacuum valve(s) integrated on the unprotected side shall have the valve pallets installed and blocked open to provide a gap of (2,5 ± 0,5) mm during each test. In line flame arresters directly combined with separate pressure and/or vacuum valves shall be tested according to the procedure in 7.3.2.2 with Lu = 10 × D and at the intended maximum relieving pressure of the system. NOTE These end-of-line venting systems could be classified as follows: a) as end-of-line deflagration arresters, in accordance with 7.3.2.1; b) as end-of-line deflagration arresters, in accordance with 7.3.2.1, and with a short time burning test, in accordance with 7.3.4; c) as end-of-line deflagration arresters, in accordance with 7.3.2.1, and with an endurance burning test, in accordance with 7.3.5. The temperatures (mixture, pipe, flame arrester) during testing shall be given in the test report. 7.3.2 Deflagration test 7.3.2.1 End-of-line flame arrester The test apparatus is as shown in Figure 1. Distances shall be measured from the top of the complete flame arrester. For end-of-line flame arresters with non-measurable elements, it might be necessary to pressurize the plastic bag (see 14.1). In this case, the mixture outlet (item 6 in Figure 1) needs to be fitted with a shut-off valve. page_22 |
| 22 | Assemble the flame arrester with all ancillary equipment, including weather cowls or other covers, and enclose it in a plastic bag. Fill the apparatus, fully inflating the bag with a mixture as specified in 6.3.2. Disconnect the mixture supply and ignite. The ignition source shall be a spark plug or a chemical igniter (maximum energy 1 kJ). Carry out two tests for each ignition point so that a total of six tests will result. Flame transmission shall be indicated by the flame detector on the protected side. No flame transmission shall occur in any of the tests. If the largest and smallest nominal sizes of a design series are satisfactorily tested, intermediate sizes may be considered acceptable without testing. Dimensions in metres / Key 1 ignition sources 2 plastic bag (Ø ≥ 1,2 m; length ≥ 2,5 m; foil thickness ≥ 0,05 mm) 3 end-of-line flame arrester 4 explosion-pressure-resistant containment (vessel or closed pipe work) 5 mixture inlet with shut-off valve 6 mixture outlet with shut-off valve 7 bursting diaphragm 8 flame detector for indication Figure 1 – Test apparatus for end-of-line flame arrester for deflagration test 7.3.2.2 In-line flame arrester The test apparatus is shown in Figure 2. The ignition source shall be a spark plug fitted in the centre of the blind flange. The pipe diameter, D, shall have the same size as the flame arrester connection. The pipe length, Lu, shall be not less than 10 × D and not greater than 50 × D for hydrocarbon-air mixtures (IIA1, IIA, IIB1, IIB2 and IIB3) and not greater than 30 × D for hydrogen-air mixtures (IIB and IIC). The pipe length, Lp, shall be 50 × D for hydrocarbon-air mixtures (IIA1, IIA, IIB1, IIB2 and IIB3) and 30 × D for hydrogen-air mixtures (IIB and IIC). page_23 |
| 23 | NOTE 1 It is advisable that the pipe length, Lu, be given by the manufacturer. In case of successful testing, Lu will be the maximum allowable run-up length for practical installations (see 14.2.1). It is possible in larger pipe sizes to approach the transition from a deflagration to a detonation when testing at raised pTB and Lu = 50 × D. If a deflagration to detonation transition is indicated, then testing with lower Lu is appropriate. The flame velocity shall be measured by two flame detectors fitted to the pipe on the unprotected side, in accordance with Figure 2. The distance b between the two flame detectors shall be in accordance with Figure 2. The pressure shall be recorded by a pressure recording system (limiting frequency ≥ 100 kHz) fitted to the pipe on the unprotected side, at a distance a in accordance with Figure 2. / Key 1 blind flange with ignition source 2 mixture inlet 3 unprotected pipe (length, Lu; diameter, D) 4 flame detectors for recording 5 in-line deflagration flame arrester 6 pressure transducer for recording 7 flame detector for indication 8 protected pipe (length, Lp; diameter, D) 9 mixture outlet 10 blind flange or other closure a ≤ 2 × D (±10 %, max. ± 50 mm), but a ≤ 250 mm 5 × D ≥ b ≥ 3 × D Figure 2 – Test apparatus for in-line flame arrester for deflagration test Fill the apparatus with a test mixture as specified in 6.3.2 and pressurize to pTB when pTB ≥ p0 (where p0 is the maximum operational pressure requested by the manufacturer or user). In six consecutive tests, no flame transmission shall occur. A flame transmission is indicated by the flame detector on the protected side. The flame velocities, maximum explosion pressures and pipe length (Lu) in each test shall be given in the test report. If the largest and smallest nominal size of a design series are satisfactorily tested, the two intermediate nominal sizes in accordance with 7.2 may be considered acceptable without testing. Each size larger than 1 000 mm shall be tested. page_24 |
| 24 | 7.3.2.3 Pre-volume flame arrester The test apparatus is shown in Figure 3. For pre-volume flame arresters with non-measurable elements, it might be necessary to pressurize the plastic bag (end-of-line application, see 14.1). In this case, the mixture outlet (item 6 in Figure 3) needs to be fitted with a shut-off valve. Pre-volume flame arresters shall be tested using the original configuration or equivalent full-scale model configuration. Pre-volume applications using end-of-line types shall be enclosed in a plastic bag, as shown in Figure 3. Pre-volume applications using in-line types shall be connected to the actual pipe work or equipment on the protected side, or to pipe work simulating the actual length, diameter and volume. Flame transmission shall be indicated by the following: a) for end-of-line types, by the ignition of the mixture in the plastic bag (2); a flame detector is optional; b) for in-line types, by the flame detector (7). / Key 1 ignition sources 2 plastic bag (Ø ≥ 1,2 m; length ≥ 2,5 m; foil thickness ≥ 0,05 mm) 3 end-of-line flame arrester 4 in-line flame arrester 5 explosion-pressure-resistant containment (vessel or closed pipe work) 6 mixture outlet with shut-off valve 7 flame detector for indication 8 original or simulated pipe work with mixture outlet and shut-off valve 9 bursting diaphragm 10 pressure transducer for recording 11 mixture inlet with shut-off valve Figure 3 – Test apparatus for pre-volume flame arrester for deflagration test |
| 25 | If the enclosure has more than one outlet, all flame arresters shall be used and tested simultaneously. Fill the enclosure and the plastic bag or pipe with a mixture as specified in 6.3.2. Disconnect the mixture supply and ignite separately at three positions inside the enclosure: one as close as possible to the flame arrester, one at the most likely position of an ignition source and one as far away from the flame arrester as possible. Carry out two tests for each position resulting in a total of six tests. No flame transmission shall occur in any of the tests. All types and sizes shall be tested. 7.3.3 Detonation test 7.3.3.1 General If the largest and smallest nominal sizes of a design series are satisfactorily tested for detonations, the two intermediate nominal sizes in accordance with 7.2 shall be considered acceptable without testing. Each nominal size larger than 1 000 mm shall be tested. Detonation flame arresters tested for unstable detonations with restriction (see 7.3.3.5) are classified as Type 1. Detonation flame arresters tested for unstable detonations without restriction (see 7.3.3.4) are classified as Type 2. Detonation flame arresters tested for stable detonations with restriction (see 7.3.3.3) are classified as Type 3. 7.3.3.2 Detonation flame arresters tested for stable detonations without restriction (see 7.3.3.2) are classified as Type 4.Stable detonation without restriction The test apparatus is shown in Figure 4. The pipe diameter, D, shall have the same size as the flame arrester connection. The pipe on the unprotected side shall have a length, Lu, sufficient to develop a stable detonation and shall have a blind flange or an explosion-pressure-resistant containment (vessel or closed pipe work) fitted with an ignition source. The pipe may also contain a flame accelerator to reduce the pipe length for stable detonation conditions. The pipe on the protected side shall have a length, Lp, of 10 × D, but not less than 3 m. The blind flange or other closure shall resist the shock pressures during testing. For measuring flame velocities and detonation pressures, four flame detectors and a pressure transducer (limiting frequency ≥ 100 kHz) shall be fitted to the pipe on the unprotected side. The position of the flame detectors and the pressure transducer shall be in accordance with Figure 4. One flame detector shall be fitted to the pipe on the protected side to indicate flame transmission. The apparatus shall be filled with a test mixture as specified in 6.3.2, and at a pressure of, pTB, when pTB ≥ p0. Under these conditions, five tests shall be carried out. page_25 |
| 26 | In each test, the flame velocities from the two pairs of flame detectors (see Figure 4) shall be constant, i.e. the difference between the two flame velocities shall not exceed 10 % of the lower value. The velocities shall be ≥ 1 600 m/s for hydrocarbon-air mixtures (IIA, IIB1, IIB2 and IIB3) and ≥ 1 900 m/s for hydrogen-air mixtures (IIB and IIC). The pressure time record shall indicate a stable detonation shock wave. / Key 1 mixture inlet 2 explosion-pressure-resistant containment (vessel or closed pipe work) or blind flange 3 ignition source 4 unprotected pipe (length, Lu; diameter, D) 5 flame detectors for recording of the flame velocity measurement 6 pressure transducer for recording 7 detonation flame arrester 8 flame detector for indication 9 protected pipe (length, Lp; diameter, D) 10 blind flange or other closure 11 mixture outlet a = (200 ± 50) mm b ≥ 3 × D, but b ≥ 100 mm c ≥ 500 mm Figure 4 – Test apparatus for detonation flame arrester for detonation without restriction Until the arrival of a stable detonation shock wave, the pressure (see item 6 in Figure 4) shall remain constant at pTB. If not, a longer pipe or turbulence promoting equipment may be used. The average value pmd of the detonation pressure shall be calculated from the area integral below the pressure-time trace, starting at the maximum pressure peak and covering a time interval of 200 µs. The average value pmd shall be calculated according to Formula (2): page_26 |
| 27 | (2) The ratio pmd/pTB, with regard to mixture and pipe size, shall correspond to the values given in Table 7 with a maximum deviation of ±20 %. NOTE When pmd/pTB exceeds the quoted values of Table 7 by more than 20 % and flame transmission occurs, the detonation might still be overdriven and it is advisable that a longer pipe or turbulence promoting equipment be used. Table 7 – Ratio pmd/pTB Explosion group Ratio pmd/pTB for pipe diameter, D mm D ≤ 80a 80 < D ≤ 150 150 < D < 1 000 D ≥ 1 000 IIA 10 12 14 16 IIB1 9 11 13 14 IIB2 9 11 13 15 IIB3 10 12 14 16 IIB 8 10 10 12 IIC 8 8 8 8 a If for pipe diameters ≤ 80 mm the quoted pressure ratio is not achieved, tests shall be carried out using a gas-air mixture of a lower safe gap to qualify the arrester as a detonation flame arrester. In addition, deflagration tests shall be carried out where the basic test set-up shall be in accordance with Figure 4, with Lp = 50 × D, as follows: a) five deflagration tests with – Lu/D = 50 for IIA, IIB1, IIB2 and IIB3, or – Lu/D = 30 for IIB and IIC. The ignition source for these deflagration tests shall be a spark plug fitted in the centre of the blind flange. For these deflagration tests, flame velocity measurement is not required. The initial pressure, deflagration and stable detonation pressure, the values of pmd/pTB and also any flame velocities recorded during the tests shall be reported. A stable detonation flame arrester (Type 4) shall prevent flame transmission in any of these stable detonation and deflagration tests. 7.3.3.3 Stable detonation with restriction The test apparatus is shown in Figure 5. The pipe diameter, D, shall have the same size as the flame arrester connection. The pipe on the unprotected side shall have a length, Lu, sufficient to develop a stable detonation and shall have a blind flange or an explosion-pressure-resistant containment (vessel or closed pipe work) fitted with an ignition source. The pipe may also contain a flame accelerator to reduce the pipe length for stable detonation conditions. page_27 |
| 28 | A restriction shall be fitted at Lr/D = 4. The pipe on the protected side shall have a length, Lp, of 14 × D but not less than 3 m after the restriction. The restriction shall consist of a blind flange with a central bore. The central bore shall have 2,5 % of the cross sectional area of the pipe. The closed pipe end and the restriction shall resist the shock pressures during testing. For measuring flame velocities and detonation pressures, four flame detectors and a pressure transducer (limiting frequency ≥ 100 kHz) shall be fitted to the pipe on the unprotected side. The position of the flame detectors and the pressure transducer shall be in accordance with Figure 5. / Key 1 mixture inlet 2 explosion-pressure-resistant containment (vessel or closed pipe work) or blind flange 3 ignition source 4 unprotected pipe (length, Lu; diameter, D) 5 flame detectors for recording the flame velocity 6 pressure transducer for recording 7 detonation flame arrester 8 flame detector for indication 9 protected pipe (length, Lp; diameter, D) 10 blind flange or other closure 11 mixture outlet 12 restriction (Lr = 4 × D) a = (200 ± 50) mm b ≥ 3 × D, but b ≥ 100 mm c ≥ 500 mm Figure 5 – Test apparatus for detonation flame arrester for detonation with restriction One flame detector shall be fitted to the pipe on the protected side to indicate flame transmission. The apparatus shall be filled with a test mixture as specified in 6.3.2, and at a pressure of pTB when pTB ≥ p0. Under these conditions, five tests shall be carried out. In each test, the flame velocities from the two pairs of flame detectors (see Figure 5) shall be constant, i.e. the difference between the two flame velocities shall not exceed 10 % of the lower value. page_28 |
| 29 | The velocities shall be ≥ 1 600 m/s for hydrocarbon-air mixtures (IIA, IIB1, IIB2 and IIB3) and ≥ 1 900 m/s for hydrogen-air mixtures (IIB and IIC). The pressure time record shall indicate a stable detonation shock wave. Until the arrival of a stable detonation shock wave, the pressure (see item 6 in Figure 5) shall remain constant at pTB. If not, a longer pipe or turbulence promoting equipment may be used. The average value, pmd, of the detonation pressure shall be calculated from the area integral below the pressure-time trace, starting at the maximum pressure peak and covering a time interval of 200 µs. The ratio pmd/pTB, with regard to mixture and pipe size shall correspond to the values given in Table 7, with a maximum deviation of ±20 %. NOTE When pmd/pTB exceeds the quoted values of Table 7 by more than 20 % and flame transmission occurs, the detonation might still be overdriven and it is advisable that a longer pipe or turbulence promoting equipment be used. In addition, deflagration tests shall be carried out, where the basic test set-up shall be in accordance with Figure 5, with Lr = 4 × D and Lp = 54 × D, as follows: a) five deflagration tests with Lu/D = 5, and b) five deflagration tests with – Lu/D = 50 for IIA, IIB1, IIB2 and IIB3, or – Lu/D = 30 for IIB and IIC. The ignition source for these deflagration tests shall be a spark plug fitted in the centre of the blind flange. For these deflagration tests, flame velocity measurement is not required. The initial pressure, deflagration and stable detonation pressure, the values of pmd/pTB and also any flame velocities recorded during the tests shall be reported. A stable detonation flame arrester (Type 3) shall prevent flame transmission in any of these stable detonation and deflagration tests. 7.3.3.4 Unstable detonation without restriction The test apparatus is shown in Figure 4. The pipe diameter, D, shall have the same size as the flame arrester connection. The pipe on the unprotected side shall have a length, Lu, sufficient to develop an unstable detonation and shall have a blind flange or an explosion-pressure-resistant containment (vessel or closed pipe work) fitted with an ignition source. The ignition source may be mounted to the wall of the unprotected pipe. The pipe may also contain a flame accelerator to reduce the pipe length for unstable detonation conditions. The pipe length and configuration on the unprotected side and the location of the ignition source shall, after ignition, produce an unstable detonation at the detonation flame arrester. The pipe on the protected side shall have a length, Lp, of 10 × D, and not less than 3 m. The blind flange or other closure shall resist the shock pressures during testing. Four flame detectors and a pressure transducer shall be fitted to the pipe on the unprotected side to record flame velocities and pressures respectively. One flame detector shall not be more than 200 mm from the flame arrester connection. One flame detector shall be fitted to the pipe on the protected side to indicate flame transmission. page_29 |
| 30 | For the purposes of this International Standard, a characteristic of an unstable detonation is pmu of not less than 2,5 × pmd for pipe diameters <100 mm, and 3 × pmd for pipe diameters ≥ 100 mm. Values of pmd shall be taken from Table 7 with regard to pTB. The unprotected side pipe length and configuration for these tests can be found by varying the distance between the ignition source and the flame arrester until the recorded flame velocities reach a maximum (above those of stable detonations). The distribution of more than four flame detectors along the pipe will make it easier to find the transition point. Direct initiation, e.g. by solid detonators, or long accelerator sections should be avoided. The apparatus shall be filled with a test mixture as specified in 6.3.2, at a pressure, pTB, when pTB ≥ p0. Under these conditions, five tests shall be carried out. In addition, deflagration tests shall be carried out, where the basic test set-up shall be in accordance with Figure 4, with Lp = 50 × D, as follows: Five deflagration tests with Lu/D = 50 for IIA, IIB1, IIB2 and IIB3, or Lu/D = 30 for IIB and IIC. The ignition source for these deflagration tests shall be a spark plug fitted in the centre of the blind flange. For these deflagration tests, flame velocity measurement is not required. The initial pressure, deflagration and unstable detonation pressures, the values of pmd/pTB and also any flame velocities shall be reported. An unstable detonation flame arrester (Type 2) shall prevent flame transmission in any of these deflagration and unstable detonation tests. 7.3.3.5 Unstable detonation with restriction The test apparatus is shown in Figure 5. The pipe on the protected side shall have a length, Lp, of 54 × D. A restriction shall be fitted at Lr/D = 4. The restriction shall consist of a blind flange with a central bore. The central bore shall have 2,5 % of the cross sectional area of the pipe. The closed pipe end and the restriction shall resist the shock pressures during testing. The test procedure for unstable detonation testing as well as the characteristic of an unstable detonation shall be in accordance with 7.3.3.4. In addition, additional deflagration tests shall be carried out completely in accordance with 7.3.3.3. An unstable detonation flame arrester (Type 1) shall prevent flame transmission in any of these deflagration and unstable detonation tests. 7.3.4 Short time burning test The test apparatus is shown in Figure 6 for an in-line and end-of-line flame arrester. page_30 page_31 |
| 31 | / Key 1 explosion-pressure-resistant containment (vessel or closed pipe work) 2 in-line flame arrester 3 end-of-line flame arrester 4 outlet pipe 5 temperature sensor for recording for tests only 6 pilot flame 7 mixture inlet 8 integrated temperature sensor for alarm 9 flame detector for indication 10 bursting diaphragm 11 pressure transducer for recording (only necessary for tBT > 1 min) 12 valve (only necessary for tBT > 1 min) Figure 6 – Test apparatus for short time burning test For flame arresters whose intended operating conditions are outside the atmospheric conditions defined in 3.25, the test of inline flame arresters shall be carried out with the test pressure equal or greater than the intended maximum operation pressure and test gas temperature equal or greater than the intended maximum operating temperature. The test of inline flame arresters with tBT = 1 min may be carried out under atmospheric conditions. A flow meter shall be used to measure the mixture flow rates. The flame arrester shall be fitted with a temperature sensor for the test only. This sensor shall be mounted close to the surface of the flame arrester element on the protected side close to the centre of the cross sectional area of the flow. The tests shall be carried out using a test mixture as specified in Table 4. First, the critical flow rate, , shall be calculated from the open area, A0, of the surface of the flame arrester element on the unprotected side and from the size and number of apertures per unit area. Assuming a uniform velocity of 75 % of a burning velocity, vl, of the mixture across this area, calculate a critical flow rate, , according to Formula (3): (3) |
| 32 | where vl = 0,5 m/s for IIA1 and IIA; vl = 0,8 m/s for IIB1, IIB2, IIB3 and IIB; vl = 3 m/s for IIC. For non-measurable flame arrester elements, the critical flow rate, , may be obtained by using the same principle. The free area, A0, of the flame arrester element surface can be estimated according to Formula (4): (4) The tests shall be carried out with a continuously operated pilot flame or spark. Ignite the mixture until the flame has stabilized on the surface of the flame arrester element. After flame stabilization, continue burning for the burning time, tBT, specified by the manufacturer (1 min ≤ tBT ≤ 30 min ). Record the temperature indicated by the test temperature sensor after that time and stop the flow. No flame transmission shall occur during the tests or when the flow is stopped. Carry out this test procedure with flow rates , and . In each of these tests, the flame arrester shall be at ambient temperature at the beginning. If results in the highest temperature reading of the three tests, then . If not, carry out two further tests with flow rates 50 % and 150 % of the flow rate which gave the highest reading in the first three tests. will be the flow rate that results in the highest temperature reading in all five tests. When determining the flow rate , flame arrester elements may be replaced between the tests. If the flame arrester elements have been replaced, a final test shall be carried out with the flow rate , using the original flame arrester element, without modification, that was used for the deflagration and/or detonation test. In any of the tests, the integrated temperature sensor(s) (8) shall produce a signal that may be used to activate counter measures within a burning time of 50 % of the manufacturer’s specified burning time, tBT, where ≤ 15 min. When using an integrated temperature measuring system, it shall record a temperature rise not less than 60 K after a burning time of not more than . A flame transmission is indicated by the flame detector (9). No flame transmission shall occur during the tests or when the flow is stopped. The burn time without flash back shall be recorded as the burning time, tBT, expressed in minutes. If the largest and smallest nominal sizes of a design series are satisfactorily tested, the intermediate nominal sizes may be considered acceptable without testing, but these flame arresters shall be marked with the shortest burning time, tBT, found in the experimental tests. Each size of in-line flame arresters greater than 1 000 mm shall be tested. page_32 |
| 33 | 7.3.5 Endurance burning test The test apparatus is shown in Figure 7 for an in-line and end-of-line flame arrester. For flame arresters whose intended operating conditions are outside the atmospheric conditions defined in 3.25, the test of inline flame arresters shall be carried out with the test pressure equal or greater than the intended maximum operation pressure and test gas temperature equal or greater than the intended maximum operating temperature. A flow meter shall be used to measure the mixture flow rate. The flame arrester shall be fitted with two temperature sensors for the test only. One temperature sensor (6) shall be mounted on the protected side. The location of this temperature sensor shall be left to the discretion of the test laboratory. Another temperature sensor (9) shall be fitted to the unprotected side to detect the stabilized flame (start of burning load). The tests shall be carried out using a mixture as specified in Table 5. / Key 1 outlet pipe 2 in-line flame arrester 3 end-of-line flame arrester 4 explosion-pressure-resistant containment (vessel or closed pipe work) 5 mixture inlet 6 temperature sensor for recording for tests only 7 pilot flame or spark igniter 8 flame detector for indication 9 test temperature sensor for alarm to detect stabilized flame 10 bursting diaphragm 11 pressure transducer for recording 12 valve Figure 7 – Test apparatus for endurance burning test First, the critical flow rate, , shall be calculated from the open area, A0, of the surface of the flame arrester element on the unprotected side and from the size and number of apertures per unit area. Assuming a uniform velocity of 75 % of a burning velocity, vl, of the mixture across this area, calculate a critical flow rate, , according to Formula (3) in 7.3.4. page_33 |
| 34 | For non-measurable flame arrester elements, the critical flow rate, , may be obtained by using the same principle. The free area, A0, of the flame arrester element surface can be estimated according to Formula (4) in 7.3.4. The tests shall be carried out with a continuously operated pilot flame or spark. Ignite the mixture until the flame has stabilized on the surface of the flame arrester element. Carry out the following preliminary testing for critical flow rates. After flame stabilization, continue burning until the protected side temperature sensor indicates a temperature rise of 20 K and then stop the flow. Record the time from stabilization of the flame to the 20 K temperature increase. Carry out this test procedure with flow rates , and . In each of these tests, the flame arrester shall be at ambient temperature at the start. If results in the shortest time to 20 K temperature increase, then . If not, carry out two further tests with flow rates 50 % and 150 % of the flow rate which gave the shortest time in the first three tests. will be the flow rate that results in the shortest time in all five tests. When determining the flow rate , flame arrester elements may be replaced between the tests. The endurance burn test shall be carried out with the flow rate , using the original flame arrester element, without modification, that was used for the deflagration and/or detonation test. Maintain the mixture composition and the flow rate (±5 %) until a stable temperature is established at the temperature sensor on the protected side. The temperature on the protected side shall be stable within ±5 K over 10 min. The flow of the mixture shall be stopped when a stable temperature is established, but not before 2 h of burning. The flame detector (8) shall indicate any flame transmission. No flame transmission shall occur during the tests or when the flow is stopped. All types and nominal sizes shall be tested. Modifications that do not change the flame arrester element and are part of the housing to which the flame arrester element is fitted do not require retesting, e.g. flame arresters with integrated pressure and/or vacuum valves. 7.3.6 In-line flame arrester 7.3.6.1 General For an in-line flame arrester, the pipe diameter on the protected side shall be no less than the pipe diameter on the unprotected side. For an in-line flame arrester, the pipe diameter on the unprotected side shall be no greater than the flame arrester connection. page_34 |
| 35 | 7.3.6.2 In-line deflagration flame arrester The use of in-line deflagration flame arresters tested in accordance with 7.3.2.2 shall be limited to the following conditions: a) the ratio of pipe length (between the potential ignition source and the flame arrester) and pipe diameter shall not exceed the tested ratio, Lu/D; b) at least 10 % of the cross sectional area of the pipe shall be open at the ignition source; c) pipe branches and valves on the unprotected side shall be installed as close as possible to the in-line deflagration flame arrester. 7.3.7 Pre-volume flame arrester The use of pre-volume flame arresters shall be limited to enclosures, contents and pipe work on the unprotected side as used or simulated in the test. 7.3.8 Detonation flame arrester Detonation flame arresters may be used for open and closed pipe work on the unprotected side. Detonation flame arresters tested at pTB are suitable for operational pressures p0 ≤ pTB in the same or smaller pipe size when the application is limited to mixtures with an MESG equal to or greater than that tested. NOTE An unstable detonation presents a higher level of hazard than a stable detonation (see 3.11). Unstable detonation flame arresters (Type 1 and Type 2) are designed and tested for stopping deflagrations and stable and unstable detonations. Stable detonation flame arresters (Type 3 and Type 4) are designed and tested for stopping deflagrations and stable detonations. 7.3.9 Short time burn flame arresters If there are operating conditions which can lead to a stabilized burning at the flame arrester element, additional safety measures are required. Depending on the operating conditions, the devices shall be equipped with temperature sensors on one or two sides which initiate measures for the elimination of the stabilized burning (for example, emergency functions like switching-off the system, inerting or similar) and this within the half of the time for which the device is short-time burn proof (0,5 × tBT). When tBT is exceeded during a short-time burning situation, then the flame arresting safety cannot be assured. When operating with only one temperature sensor, the installation side (identification on side to be protected) has to be respected. Temperature sensors shall meet the flame arrester manufacturer’s specification, they shall be installed in the flame arrester according to the flame arrester manufacturer´s instructions. Temperature sensors shall be integrated into the control system so that safety measures to stop the stabilized burning are initiated. Prior to putting the devices with safety system into operation, the switching temperature shall be adjusted so that the admissible time period for the activating of the emergency measures will be observed. page_36 |
| 36 | 8 Specific requirements for liquid product detonation flame arresters 8.1 Liquid seals A flame arrester consisting of a liquid seal formed by the liquid product may be an end-of-line flame arrester [see Figure 8 a)] or an in-line flame arrester [see Figure 8 b)]. The housings for liquid seals suitable for emptying operations shall incorporate a safety device that prevents loss of the sealing liquid. a) End-of-line flame arrester b) In-line flame arrester Key 1 housing 2 overflow pipe/outlet pipe 3 immersion pipe 4 immersion depth 5 filling height Figure 8 – Liquid product detonation flame arrester 8.2 Foot valves There shall be an end-of-line flame arrester incorporating a non-return valve (foot valve) in an immersion cup, providing an immersion depth of not less than that specified by the manufacturer. A screen or perforated plate shall protect the valve seat from solid particles (see Figure 9). |
| 37 | / Key 1 valve housing 2 valve disc 3 immersion cup 4 perforated plate or screen 5 immersion depth Figure 9 – End-of-line flame arrester incorporating a non-return valve (foot valve) 8.3 Flame transmission test Liquid product detonation flame arresters shall be tested under atmospheric conditions for detonations only. The flame arrester shall be filled either with the liquid to be used in operation, or alternatively with gasoline having a boiling range from 100 °C to 140 °C. These liquids may also be used in tests for group IIB mixtures. The filling height shall be recorded (see Figure 8 and Figure 9). In-line and end-of-line flame arresters shall be tested in accordance with the test procedure given in 7.3.3.2 and, if necessary, in accordance with 7.3.3.4, but using the test apparatus shown in Figure 10. On the basis of the operational conditions for these flame arresters, only three stable detonation tests shall be carried out. The flame arrester test shall be carried out in the orientation required in service. The foot valve shall be opened for the test to present a gap at least equal to or greater than the opening in the screen or perforated plate used to protect the valve seat from solid particles. page_37 |
| 38 | / Key 1 mixture inlet 2 explosion-pressure-resistant containment (vessel or closed pipe work) 3 ignition source 4 unprotected pipe (length, Lu; diameter, D) with bypass 5 flame detectors for recording the flame velocity measurement 6 pressure transducer for recording 7 liquid product detonation flame arrester 8 plastic bag (Ø ≥ 1,2 m; length ≥ 2,5 m; foil thickness ≥ 0,05 mm) 9 mixture outlet (bypass) a = (200 ± 50) mm b ≥ 3 × D, but b ≥ 100 mm c ≥ 500 mm Figure 10 – Test apparatus for liquid product detonation flame arresters 9 Specific requirements for dynamic flame arresters (high velocity vent valves) 9.1 General Dynamic flame arresters shall be tested for flame transmission (see 9.2). All types and sizes shall be tested. Testing shall be carried out at the lowest setting and closing pressure intended for approval. NOTE The minimum efflux velocity is typically 30 m/s. The set pressure, closing pressure and flow rate at closing point, , of the dynamic flame arrester shall be specified. Dynamic flame arresters with more than one nozzle shall have each nozzle tested for flame transmission. During the flame transmission tests, the dynamic flame arrester shall be combined as one flame arrester. Other openings (e.g. drain plug) should be tested in accordance with their operation principle. The tests shall be carried out with the same test sample without adjustments and without replacement of components. page_38 |
| 39 | For endurance burn proof dynamic flame arresters, the test order has to start with endurance burning according to 9.2.4. For the tests described in 9.2, the completion of the undamped oscillation test in accordance with A.4 is required to provide LM, DM, and VM. 9.2 Flame transmission tests 9.2.1 Low flow flame transmission test The test apparatus is shown in Figure 11. The pipe length and the pipe diameter between the explosion-pressure-resistant containment and the dynamic flame arrester shall be LM and DM and the volume of the explosion-pressure-resistant containment shall be VM (given in A.4). A smaller volume than VM may be used providing that it does not increase the risk of flame transmission. NOTE 1 If the valve displays undamped oscillation (hammering) according to A.4, it is an indication that the volume used is too small. A temperature sensor for testing shall be attached to the dynamic flame arrester as close as possible to the stabilized flame (e.g. at the valve seat). Ignition shall be maintained by a permanent pilot flame. The pilot flame shall be positioned as close as possible to the mixture outlet to atmosphere, but far enough away from the mixture outlet to avoid heating, or influencing the correct operation of, the dynamic flame arrester. The pilot flame shall burn propane and provide a stabilized pilot flame. A gas-air mixture as specified in Table 4 shall be fed into the explosion-pressure-resistant containment. The flow rate into the explosion-pressure-resistant containment shall be increased in four steps. The step width depends on the dynamic flame arrester characteristic, as follows: for a dynamic flame arrester with , the step width shall be with a starting point of ; for a dynamic flame arrester with , the step width shall be 20 % of the flow rate of the fully open dynamic flame arrester. The starting point shall be 10 % of the flow rate of the fully open dynamic flame arrester. The duration of each test step shall be chosen depending on the dynamic flame arrester action, as specified below. a) If at some point during the sequence of tests the dynamic flame arrester remains in the open position while steadily relieving, the test shall be stopped (e.g. by a shut-off valve), thereby forcing the dynamic flame arrester to close. b) If the dynamic flame arrester varies periodically between the closed and open position associated with a varying pressure in the containment, the test duration shall be a minimum of 5 min or 50 open/closed cycles and shall furthermore cover a minimum of five closing actions before the next flow rate step is adjusted. If the flow rate readings vary due to the opening and closing cycles [see case b) above], the appropriate averaged flow rate shall be used. This procedure shall be carried out with the dynamic flame arrester in the upright position. The tests shall be repeated with the dynamic flame arrester inclined (10 ± 1)° to the vertical orientation, unless the use is limited to fixed vertical applications without changing of inclination during operation. NOTE 2 Testing in the inclined position is intended to simulate motion of the dynamic flame arrester, e.g. on marine vessels. page_39 page_40 |
| 40 | No flame transmission shall occur during these tests. / Key 1 flame 2 dynamic flame arrester 3 explosion-pressure-resistant containment 4 mixture inlet 5 bursting diaphragm 6 temperature sensor for recording (for tests only) 7 pilot flame 8 flame detector for indication 9 flow meter for recording 10 shut-off valve 11 pressure sensor for recording DM diameter of the pipe on the protected side determined in accordance with A.4 Lm pipe length upstream of the dynamic flame arrester determined in accordance with A.4 VM volume of the explosion-pressure-resistant containment Figure 11 – Test apparatus for determining the non-hammering conditions for dynamic flame arresters 9.2.2 Flame transmission test by opening and closing The test apparatus is shown in Figure 11. The pipe length and the pipe diameter between the explosion-pressure-resistant containment and the dynamic flame arrester shall be LM and DM and the volume of the explosion-pressure-resistant containment shall be VM (given in A.4). A smaller volume than VM may be used providing that it does not increase the risk of flame transmission. NOTE 1 If the valve displays undamped oscillation (hammering) according to A.4, it is an indication that the volume used is too small. A temperature sensor for testing shall be attached to the dynamic flame arrester as close as possible to the stabilized flame (e.g. at the valve seat). Ignition shall be maintained by a permanent pilot flame. The pilot flame shall be positioned as close as possible to the mixture outlet to atmosphere, but far enough away from the mixture outlet to avoid heating, or influencing the correct operation of, the dynamic flame arrester. The pilot flame shall burn propane and provide a stabilized pilot flame. page_41 |
| 41 | The dynamic flame arrester shall be subjected to 50 open/closed cycles, using a gas-/air-mixture as specified in Table 4. During the 50 cycles the mixture shall be ignited by a pilot flame close to the outlet. This test can be disregarded if 50 open/closed cycles have been observed during the low flow flame transmission tests. This procedure shall be carried out with the dynamic flame arrester in the upright position. The tests shall be repeated with the dynamic flame arrester inclined (10 ± 1)° to the vertical orientation, unless the use is limited to fixed vertical applications without changing of inclination during operation. NOTE 2 Testing in the inclined position is intended to simulate motion of the dynamic flame arrester, e.g. on marine vessels. No flame transmission shall occur during the test. 9.2.3 Deflagration test Deflagration tests shall be carried out according to 7.3.2.1. 9.2.4 Endurance burning test The test apparatus is shown in Figure 11. The pipe length, Lm, between the explosion-pressure-resistant containment and the dynamic flame arrester shall not exceed LM. A temperature sensor for testing shall be attached to the dynamic flame arrester as close as possible to the stabilized flame (e.g. at the valve seat). Ignition shall be maintained by a permanent pilot flame. The pilot flame shall be positioned as close as possible to the mixture outlet to atmosphere, but far enough away from the mixture outlet to avoid heating or influencing the correct operation of, the dynamic flame arrester. The pilot flame shall burn propane and provide a stabilized pilot flame. Using a gas-air mixture as specified in Table 4, the pressure in the explosion-pressure-resistant containment shall be increased to force the dynamic flame arrester open and then shall be maintained at 10 % above the established closing pressure. The corresponding flow rate, , shall be recorded. If no stabilized burning is possible under these conditions, the mixture shall be gradually enriched until the flame is stabilized. Without changing that mixture composition, the flow shall be increased in increments of 20 % of , and after each increment, the flow shall be maintained until the temperature rise is less than 10 K/min, but for a minimum of 5 min. When the temperature starts to decrease, the flow rate is the maximum flow rate that shall be used in this test. The flow rate shall then be reduced in increments of 10 % of and after each step shall be maintained until the temperature change is less than 10 K/min, but for a minimum of 5 min. Flow rates for which the corresponding temperature has been recorded need not be repeated, and tests need not be made at flow rates below . Upon completion, the flow rate yielding the highest temperature shall be recorded as and the burning at that rate shall be continued until the change of temperature indicated by the test temperature sensor does not exceed ±5 K in 10 min. For enriched mixtures, the concentration shall be gradually reduced as far as possible towards the initial value (see Table 4) keeping the flame stabilized. The flow shall be stopped and no flame transmission shall occur. page_42 |
| 42 | 10 Specific requirements for hydraulic flame arresters 10.1 Equipment Hydraulic flame arresters are in-line flame arresters. An example is shown schematically in Figure 12. They consist of a mixture inlet (3), a container (1) with a water seal (12), one or more immersion pipe(s) (2) and a mixture outlet (16). The design and construction shall ensure that the immersion depth is always constant within ±5 mm. Hydraulic flame arresters shall include the following features: a) a level indicator with an optical display (4) for the immersion depth at rest (ZR) and the operational immersion depth (Z0); b) automatic equipment (5) to maintain the water level above the minimum operational immersion depth (Z0min); c) a temperature sensor (8) for the water seal; d) an integrated temperature sensor (7) above the water seal (12) to indicate a stabilized flame. 10.2 Flame transmission test 10.2.1 General Hydraulic flame arresters shall be tested for short time burning, deflagration and stable detonation in succession. Before ignition, mixtures shall be at ambient conditions on the unprotected side. Each test shall be carried out with the minimum immersion depth at rest (ZRmin) which corresponds with the minimum operational immersion depth (Z0min) specified by the manufacturer. The flow rate of the mixture shall be recorded with a sensor (9) at the inlet, and flame transmission shall be detected with a flame detector (18) in the inlet pipe. 10.2.2 Short time burning test The test apparatus is as shown in Figure 12, with the mixture outlet pipe (6) removed if necessary. The ignition source (14) shall be positioned (100 ± 20) mm above the water seal (12). The test shall be carried out for not less than 5 min with a water seal temperature ≥ 10 °C, at which time the temperature shall remain ≤ 30 °C. The safe volume flow rate shall be determined for the minimum immersion depth at rest (ZRmin) respectively at the minimum operational immersion depth (Z0min) at which no flame transmission occurs. Four tests shall be carried out with . No flame transmission shall occur in any of the tests. 10.2.3 Deflagration test The test apparatus is as shown in Figure 12, with the mixture outlet pipe (6) in place and equipped with two flame detectors (18) in a straight part of the pipe close to the mixture outlet (16) (see also Figure 2). The maximum diameter, D, of the mixture outlet pipe (6) shall be used for all tests for which the hydraulic flame arrester is acceptable. The ignition source (13) shall be positioned at the open end of the mixture outlet pipe (6). Tests shall be carried out by using a test mixture as specified in 6.3.2. page_43 |
| 43 | The deflagration test shall be carried out at the minimum immersion depth at rest (ZRmin) which corresponds with the minimum operational immersion depth (Z0min) with the mixture flow rate at as determined in 10.2.2. The test shall be carried out with the following lengths of mixture outlet pipe (6): Lu = 50 × D; Lu = 100 × D. Carry out three tests on each length. If flame transmission takes place, the flow shall be reduced to a level where no flame transmission occurs. This reduced flow shall then be recorded as . 10.2.4 Detonation test The test apparatus is as shown in Figure 12, with the mixture outlet pipe (6) in place and equipped with four flame detectors (15) in the straight part of the pipe close to the outlet (16) (see also Figure 4). All tests shall be carried out with the mixture outlet pipe (6) with the maximum diameter, D, for which the hydraulic flame arrester shall be used. The mixture outlet pipe (6) shall have a blind flange equipped with an ignition source (13). The mixture outlet pipe (6) shall have sufficient length to develop a stable detonation (see 7.3.3.2 for further details). Tests shall be carried out by using a test mixture as specified in 6.3.2. Carry out three detonation tests with the mixture at rest and with the minimum immersion depth at rest (ZRmin), for which the hydraulic flame arrester is acceptable. No flame transmission shall occur in any of the tests. page_44 |
| 44 | / Key 1 container for the hydraulic flame arrester medium 2 gas or vapour mixture immersion pipe(s) 3 gas or vapour mixture inlet 4 water seal level indicator with an optical display 5 automatic water seal level control 6 mixture outlet pipe (length, L; diameter, D) 7 temperature sensor for alarm to indicate a stabilized flame above the water seal 8 water seal temperature sensor 9 mixture volume flow sensor 10 direction of mixture flow 11 direction of flame propagation 12 water seal 13 ignition source for flame transmission tests 14 ignition source for stabilized burning tests 15 flame detector for recording flame velocity 16 mixture outlet 17 filling height 18 flame detector to indicate flame transmission a = (25 ± 3) mm Figure 12 – Test apparatus for hydraulic flame arresters |
| 45 | 11 Test of flame arresters installed on or within gas conveying equipment 11.1 General The gas conveying equipment described below is intended for the transport of mixtures of air and combustible gases, vapours or mists. These mixtures to be transported are situated in the working chamber inside the gas conveying equipment. These gas conveying equipment have pipe connections on the suction/inlet side and pressure/outlet side. Flame arresters for the protection of the pipework connected to the gas conveying equipment, which are integrated or mounted on the inlet and outlet side of the gas conveying equipment shall be tested, together with the gas conveying equipment, for safety against flame transmission through the flame arrester in the case of explosions in the gas conveying equipment inside. The results of the tests with ambient temperatures ≤60 °C at the flame arresters apply to temperatures from −20 °C up to +60 °C at the flame arrester elements. If, during operation of the gas conveying equipment, temperatures of more than 60 °C arise at the flame arrester element, additional tests shall be carried out with the correspondingly warmed flame arresters. No flame transmission through the flame arrester into the connecting pipes shall occur at the flame arresters in any of the tests to be carried out. 11.2 Flame transmission test 11.2.1 General The instructions for the tests of the gas conveying equipment are specified depending on the respective rated inlet pressure according to 11.2.2 and 11.2.3. The test apparatus is shown in Figure 13. page_45 |
| 46 | / Key 1 gas conveying equipment 2 flame arrester inlet side, size of flange connection Ø1 3 flame arrester outlet side, size of flange connection Ø2 4 test pipe flame arrester inlet side – throttle valve (Ø: D1, length: L1), D1 ≤ Ø1 5 test pipe flame arrester outlet side – throttle valve (Ø: D2, length: L2), D2 ≤ Ø2 6 throttle valve 7 mixture inlet 8 mixture outlet 9 pressure sensor (static); in addition as an option: pressure sensor (dynamic), flame detector and temperature sensor 10 pressure sensor (dynamic) 11 flame detector 12 temperature sensor on the flame arrester surface facing the test pipe 13 alternative ignition points close to the moved parts of the equipment Figure 13 – Test apparatus for the flame transmission test of flame arresters installed on or within gas conveying equipment The diameter of the test pipe parts (D1, D2) installed between the flame arresters and the throttle valves shall not be larger than the size of flange connection of the respective flame arrester. Reductions or enlargements of the diameters of the test pipe parts may be carried out only after a length of 10 × D1 downstream of the flame arrester on the inlet side and 10 × D2 downstream of the flame arrester on the outlet side. The nominal size of the throttle valve shall be the same or smaller than the diameter of the pipe (D1 or D2). Mixture inlets and outlets in the test pipe shall be arranged to be close to the throttle valve. page_46 |
| 47 | The ignition source shall be placed as near as possible to the mechanically moved parts of the equipment on the inlet side or on the outlet side. The tests shall be carried out with a gas/air-test mixture as specified in Table 3. The test apparatus with a closed throttle valve shall be purged with the test mixture until the mixture concentration at the outlet corresponds to the specifications of Table 3, and then isolated from the gas filling system. 11.2.2 Test procedure for gas conveying equipment with inlet pressure > 600 hPa After sufficiently purging the test apparatus with the test mixture, the specified parameters in Table 8: operating state of the equipment, position of the throttle valve, and test mixture pressure in the test apparatus shall be adjusted for the respective test. 12 tests shall be carried out with working equipment (see Table 8). The mixture temperature and the equipment shall be warmed up that the temperature profile up to a steady-state temperature (60 °C or the maximum allowed temperature given by the manufacture at the inlet as a general rule). The maximum gas temperature shall be measured at the mixture outlet. Six tests shall be carried out with switched-off equipment (see Table 8). The equipment and the test mixture shall be at ambient temperature when the test mixture is ignited. Table 8 – Number of the individual tests and test parameters for the flame transmission test of flame arresters installed on or within gas conveying equipment with inlet pressures > 600 hPa Test parameters Operating state Mixture pressure Ignition point Position of the throttle valve Number of tests Rotating at max. speed Max. inlet pressure Inlet side Open 3 Max. outlet pressure Approx. 80 % closeda 3 Max. inlet pressure Outlet side Open 3 Max. outlet pressure Approx. 80 % closeda 3 Stationary Max. inlet pressure Inlet side closed 3 Outlet side closed 3 a Valve closed so far (approx. 80 %) so that the maximum outlet pressure is achieved in the equipment, but a sufficient air flow is remaining to avoid overheating of the equipment. In addition, the flame arrester on the inlet side shall be subjected to a short time burning flame transmission test according to 7.3.4 with connected pipe. The external surface temperature shall be taken into account when specifying the temperature class of the equipment. page_47 |
| 48 | 11.2.3 Test procedure for gas conveying equipment with inlet pressure ≤ 600 hPa After sufficiently purging the test apparatus with the test mixture, the specified parameters in Table 9: operating state of the gas con veying equipment, position of the throttle valve and test mixture pressure in the test apparatus shall be adjusted for the respective test. Tests shall be carried out at the maximum operational temperatures at the flame arrester element according to Table 9. Table 9 – Number of the individual tests and test parameters for the flame transmission test of flame arresters installed on or within gas conveying equipment with inlet pressures ≤ 600 hPa Test parameters Operating state Mixture pressure Ignition point Position of thethrottle valve Number of tests Temperature at the flame arresters: Ambient temperature (≤ 60 °C) Rotation at max. speed Max. outlet pressure Inlet side Open 3 Outlet side Closed 5 Open 3 Stationary Max. inlet pressure Inlet side Closed 5 Outlet side Closed 3 In addition, if temperature at the flame arresters at outlet: > 60 °C Rotation at max. speed Max. outlet pressure Outlet side Closed 6 Stationary Max. inlet pressure Inlet side Closed 3 Outlet side Closed 3 In addition, if temperature at the flame arrester at inlet: > 60 °C Rotation at max. speed Max. outlet pressure Inlet side Open 3 Stationary Max. inlet pressure Inlet side Closed 6 Outlet side Closed 3 In addition, the flame arrester on the inlet side shall be subjected to a short time burning flame transmission test according to 7.3.4 with connected pipe. The external surface temperature shall be taken into account when specifying the temperature class of the equipment. 12 Instructions The instructions prepared by the manufacturer shall include the following particulars as a minimum: a) a recapitulation of the information with which the equipment is marked, except for the serial number (see Clause 11), together with any appropriate additional information to facilitate maintenance (for example, address of the importer, repairer, etc.). This shall include specifically points b) – g);; page_48 |
| 49 | b) information concerning the classification of the flame arrester as outlined in Clause 5; c) all details of the operational requirements, including the specific limits in accordance with Annex E, as appropriate; the maximum operational temperature and pressure shall be given; d) static flame arresters classified as safe for endurance burning shall include a warning that safe use is limited to pure hydrocarbons, and that extension to other chemicals may require testing with these specific chemicals; e) short time burning flame arresters and hydraulic flame arresters shall include a warning that additional external safety equipment is required; all data that are necessary to characterize the integrated temperature sensor used for the stabilized burning test shall be documented; if the user equips the flame arrester with any other temperature sensor, this sensor shall fulfil these requirements as a minimum; f) the burn time (and, if this burn time was determined under conditions outside the atmospheric conditions defined in 3.25, the pressure and temperature under which it was determined); g) the allowed installation direction of the flame arrester with regard to flow direction and protected side; h) general instructions for safety, i.e. – putting into service; – use; – assembling and dismantling; – maintenance (including cleaning instructions and the procedure to be followed after deflagration, detonation or stabilized burning conditions have taken place); – installation (including full description of the connections of the flame arrester); – adjustment; – where necessary, training instructions; – where applicable, Specific Conditions of Use that require additional protective means by the installers or users; i) – a list of the standards, including the issue date, with which the equipment is declared to comply. The certificate can be used to satisfy this requirement. 13 Marking 13.1 Location The equipment shall be legibly marked on the flame arrester housing and the marking shall be visible, from the exterior, prior to the installation of the equipment. NOTE 1 The marking is intended to be in a location that is likely to be visible after installation. Where the element is a removable part, the element shall additionally be marked according to 13.3, which can be useful during installation and maintenance by helping to avoid confusion with similar equipment. 13.2 Flame arrester housing 13.2.1 General information The flame arrester housing shall be marked with the following information: a) the name and address of the manufacturer or its registered trade mark; b) the manufacturer’s type identification or series designation; c) the serial number; page_49 |
| 50 | d) the year of construction [if not incorporated in point c)]; e) the name or mark of the certificate issuer and the certificate reference in the following form: the last two figures of the year of the certificate followed by a “.” followed by a unique four character reference for the certificate in that year; NOTE 1 For some regional third-party certification, the separating character “.” is often replaced by another separating designator such as “ATEX”. f) If Specific Conditions of Use apply, the symbol “X” shall be placed after the certificate reference described in d) above. The use of a warning marking giving appropriate instructions can be used as an alternative to the requirement for the “X” marking. NOTE 2 It is the intent that the requirements of the Specific Conditions of Use, e.g. mounting position or corrosion resistance, are passed to the user together with any other relevant information in the instructions for use. g) the number of this International Standard,; h) set pressure and/or set vacuum for flame arresters with integrated pressure and/or vacuum valve, or for dynamic flame arresters; i) protected side (directional types only); j) maximum flow rate (hydraulic flame arresters); k) explosion group; l) any additional marking if required by the applicable industrial safety standards for the construction of the equipment. Manufacturers and users shall ensure that any marking is legible and labels and attachment devices are durable and resistant to environmental corrosion under operating conditions. 13.2.2 Warning markings Flame arresters shall have a warning marking sign with the following information: a) Warning; b) flame arresters have installation and application limits; c) type designation in accordance with this International Standard; d) for deflagration flame arresters, the sign “DEF” and the ratio Lu/D; for end-of-line flame arresters, Lu/D is not applicable (“n/a”); e) for detonation flame arresters, the sign “DET” in combination with the type number: – “1” – tested for unstable detonation with restriction; – “2” – tested for unstable detonation without restriction; – “3” – tested for stable detonation with restriction; – “4” – tested for stable detonation without restriction; f) pre-volume flame arresters , the sign “VDEF” and the relevant limits (i.e. pressure, temperature and volume) according to the test report, see E.2.2; g) for burn rating, the sign “BC” plus the classification “a”, “b” or “c” (as specified below), together with the burn time tBT (in min) for class “b”, i.e.: – “a” – endurance burn (no time limit); – “b” – short time burn according to 7.3.4; – “c” – no burn time; NOTE 1 When a flame arrester has been tested against short-time burning, this will be marked with “Burning Class: b” and “Burning Time: tBT = …” (irrespective of the fact if the temperature sensors are installed or not) because this is a tested property of the safety system. h) explosion group; i) maximum operational temperature T0 (in °C); j) maximum operational pressure p0 (absolute pressure) (in MPa). page_50 |
| 51 | NOTE 2 For end-of-line flame arresters, the maximum operational pressure is not applicable. 13.2.3 Examples of marking Examples of marking plates are shown in Figure 14 and Figure 15 below. Figure 14 shows an example of a marking plate for an end-of-line deflagration arrester safe for burn classification “a” for explosion group (Ex. Gp) IIA, for an operational temperature, T0, of 60 °C./Figure 14 – Example of marking plate, burn rating “a” Figure 15 shows an example of a marking plate for a detonation arrester of Type 2, for explosion group (Ex. Gp) IIB3, for a burn classification “b” of 15 min, an operational temperature, T0, of 120 °C and a maximum operational pressure, p0, of 0,16 MPa. NOTE 1 bar = 0,1 MPa. / Figure 15 – Example of marking plate, burn rating “b” 13.3 Flame arrester element The flame arrester element shall be marked with the above, or, if there is limited space, as a minimum with the following information: a) the name or registered trade mark of the manufacturer; b) the certificate number; c) the serial number or identification code (this can be abbreviated or omitted if the certificate reference allows identification of the specific type); d) the protected side (directional flame arrester elements only). Compliance with item e) in 13.2.1.1 shall not be stated unless all appropriate requirements of this International Standard are met. Manufacturers and users shall ensure that any marking is legible and labels and attachment devices are durable and resistant to environmental corrosion under operating conditions. 14 Manufacturing and production 14.1 Construction No factor of the production flame arresters (type, characteristic, position etc.) defined within the technical documentation referenced in the test report may be modified unless otherwise permitted by the issuer of the test report. page_51 |
| 52 | For technical reasons, the gap dimensions of crimped ribbon flame arrester elements may be less than the lower tolerance limits in the inner and outer areas of the flame arrester element. The total affected area shall not exceed 10 % of the total surface area. As an alternative to visual inspection, equivalent performance may be demonstrated by performing a flow test according to Annex A and comparing the results with a reference pressure drop curve. The pressure drop of the production type shall be higher than the pressure drop of the prototype. Light metal alloys shall not contain more than 6 % magnesium. Coatings of components which may be exposed to flames during operation shall not be damaged in a way that makes flame transmission possible. Evidence shall be available that manufacture is controlled within tolerances to ensure reproducibility. 14.2 Housing Thread gaps, which shall prevent flame transmission, shall be in accordance with the constructional requirements of IEC 600791. 14.3 Joints All joints shall be constructed and sealed in such a way that flame cannot bypass the flame arrester element, and flame is prevented from propagating to the outside of the flame arrester. 14.4 Pressure test Pressure testing of in-line and end-of-line detonation flame arresters shall be carried out at each flame arrester at a pressure of not less than 10 × p0, and of all in-line deflagration flame arresters at not less than 1,1 × 106 Pa for not less than 3 min. All in-line deflagration and detonation flame arresters and end-of-line detonation flame arresters of welded construction need only be type tested, where documentary evidence is provided that the weld procedure and welder qualification satisfy the requirements of the design method employed. Flame arresters with any subsequent alteration to the design, affecting its strength, shall be retested. Cast components may be pressure tested individually prior to assembly of the complete unit. No permanent deformation shall occur during the tests. End-of-line deflagration flame arresters need not be pressure tested. 14.5 Leak test Each flame arrester shall be leak tested with air at 1,1 × p0, with a minimum of 150 kPa absolute for not less than 3 min. No leak shall occur. End-of-line deflagration flame arresters need not be leak tested. |
| 53 | Annex A (normative)Flow measurement A.1 General The pipes, as well as the connections between the pipes and the flame arrester, shall be smooth and without obstructions causing additional turbulence. The nominal size, D, of the test pipes (L1, L2, L3 and L4) shall be the same size as the flame arrester or dynamic flame arrester connection. All pressure measuring points shall be arranged normal to the pipe axis and shall not influence the flow. The test medium shall be air at ambient conditions. Ambient pressure and temperature shall be recorded to convert flow rate to normal conditions. A mass flow meter may be used to obtain a flow rate/pressure drop curve with a minimum of 10 suitably spaced readings from stationary flow conditions. Separate flame arresters and pressure and/or vacuum valves that are combined and used together shall be flow tested together as a single unit. A.2 In-line flame arresters The test apparatus is shown in Figure A.1. The test pipes shall have the following lengths: L1 ≥ 10 × D; L2 = 2 × D; L3 ≥ 10 × D; L4 = 2 × D. The flow rate shall be increased in suitable steps up to the maximum requested by the manufacturer or user. The pressure drop for each step shall be recorded (see item 4 in Figure A.1). The pressure or vacuum side of the blower may be used for in-line flame arresters. |
| 54 | / Key 1 blower or fan 2 flow detector for recording 3 in-line flame arrester 4 pressure sensor for recording L1, L2, L3, L4 length of apparatus pipes Figure A.1 – Test apparatus for recording the pressure drop/flow rate curve for in-line flame arresters A.3 End-of-line flame arrester A.3.1 General The test apparatus is shown in Figure A.2. The diameter of the tank (3) shall be sufficient to allow a mean flow velocity of less than 0,5 m/s in the tank. All tank pressure data (pT) shall be recorded under these conditions. The test pipe shall have a length L1 ≤ 10 × D (see Figure A.2). If reduction pipes are used, they shall not cause additional turbulence or restriction to flow. The flow rate shall be increased in suitable steps up to the maximum requested by the manufacturer. The pressure drop, pT, for each step shall be recorded (see item 4 in Figure A.2). End-of-line flame arresters combined with, or integrated into, pressure and/or vacuum valves (see Figure A.2) shall have the flow rate/pressure drop curve start at the set pressure (opening pressure) with increases in suitable steps up to the maximum flow rate requested by the manufacturer. Vacuum valves shall have the direction of flow reversed. A.3.2 Special flow measurement for dynamic flame arresters Flow measurements for dynamic flame arresters shall be made using the lowest possible setting for the specific model without changing its characteristics, as defined in 9.2. The flow measurement shall consist of three phases: phase 1 (opening phase): the capacity from shut to fully open; phase 2 (working area): the capacity from fully open and upward; phase 3 (closing phase): the capacity from fully open to shut. page_53 |
| 55 | The flow measurement for phase 1 is carried out to establish pressure surges and/or pressure reductions. The flow rate to be used for this purpose is determined as the flow at which the dynamic flame arrester is fully open. Ten equally spaced measurements (10 % of the flow rate, 20 % of the flow rate, etc.) shall be recorded in the interval from shut to fully open. If the dynamic flame arrester features a system that makes it change its dynamic characteristics from modulating to full lifting, 10 additional and equally spaced measurements shall be made at this point within a span of 10 % to each side. The flow measurement for phase 2 is carried out to establish the pressure increase from when the dynamic flame arrester is fully open and upward. The capacity shall be measured at the pressure at which the dynamic flame arrester is fully open, and at five or more increments of 10 % above this pressure. The flow measurement for phase 3 is carried out to establish the blow-down value of the dynamic flame arrester. The flow rate to be used is the least capacity at which the dynamic flame arrester remains fully open. The pressure shall then be recorded for 10 equally spaced capacities between this flow and when the dynamic flame arrester is shut. A flow chart shall be drawn based on the above measurements. / Key 1 blower or fan 2 flow detector for recording 3 explosion-pressure-resistant containment 4 pressure sensor for recording 5 end-of-line flame arrester L1 length of connecting pipe pT pressure in the flow test of an end-of-line flame arrester Figure A.2 – Test apparatus for recording the pressure drop/flow rate curve for end-of-line flame arresters with or without integrated pressure and/or vacuum valve A.4 Undamped oscillation tests of dynamic flame arrester (High velocity vent valves) Dynamic flame arresters shall be tested in order to determine the maximum pipe length, LM, that does not lead to undamped oscillations. The test apparatus is shown in Figure A.3. The test set-up shall incorporate a valve disc location monitor (e.g. video camera, position meter) to trace the position of the valve disc during the test runs. The initial pipe length, L2, (Figure A.3), the volume, VM, and the pipe diameter, DM, shall comply with the specifications by the manufacturer. page_54 |
| 56 | DM, VM and LM are also basic parameters for the flame transmission test (9.2) and the resulting limits for use (9.3). For valves which (due to their characteristics) may perform periodic open/close cycles at certain flow rates, it is recommended to comply with the following condition: The tank volume, VM, should be large enough to ensure that tank volume has no effect on oscillations in any of the tests. For any dynamic flame arrester type, the following tests shall be carried out at the lowest setting intended for approval. The flow rate into the containment shall be increased in 10 steps. The span and step width of the 10 flow rates shall be chosen depending on the valve characteristic, as specified below. For valves with , the lowest flow rate shall be and the highest shall be (step width ). For valves with the lowest flow rate shall be 10 % of the rate at which the valve is fully open. This value shall also be taken as step width. At each flow rate, an opening of the valve shall be awaited (if initially closed) and the flow shall then be maintained for additional 3 min. If the disc location monitor indicates periodic contact with seat or upper stop with a frequency of more than 0,5 Hz (undamped oscillation), the pipe length (L2) shall be shortened until this frequency value is not exceeded or the contacting ceases. That length shall be recorded as LM. / Key 1 blower or fan 2 flow detector for recording 3 containment 4 pressure sensor for recording 5 dynamic flame arrester 6 pressure sensor L2 length of vent pipe Figure A.3 – Test apparatus for determining the non-oscillating conditions for dynamic flame arresters page_55 |
| 57 | Annex B (informative)Information for selecting flame arresters To help manufacturers and users decide which flame arrester is the most suitable for their application, the information outlined in Table B.1 should be considered. Table B.1 – Information for selecting flame arresters Characteristic Aspect to be considered 1. Service Provide a brief description of the intended use for the flame arrester. 2. Analysis of gases or vapours Provide full details of flammable and non-flammable components, which will allow the correct flame arrester design, explosion group and choice of materials to be made. 3. Molecular weight or density of gas or vapour This will allow an equivalent air flow rate to be calculated for pressure drop determination. 4. Flow rate This should be in volumetric terms, or sufficient information should be provided to allow a volumetric flow rate to be calculated. For storage tank applications, the inbreathing and outbreathing requirements should be given, or sufficient information on the tank type, pressure resistance shape, dimensions, fill and empty rates should be provided to enable these parameters to be calculated. 5. Temperature ranges For both design and operating conditions, the maximum and minimum temperatures will allow the correct element and mechanical design of the flame arrester housing to be made. 6. Pressure ranges For both design and operating conditions, the maximum and minimum pressures will allow the correct flame arrester element and mechanical design of the flame arrester housing to be made. The maximum pressure at which an explosive mixture can ignite in the process should be highlighted if this is different to the normal operating pressure. For storage tank applications, the pressure and vacuum requirements should be given. 7. Allowable pressure drop This will enable the correct flame arrester configuration to be provided and is determined from the volumetric flow rate. 8. Type Specify in-line, end-of-line, pre-volume, short time or endurance burning safe and stable/unstable detonation, as required. For in-line types, details of the piping between the flame arrester and possible source of ignition should be supplied in the form of a dimensioned sketch or isometric drawing. 9. Orientation State the intended orientation of the flame arrester. 10. Pipe size The nominal size of the connecting pipe work should be stated. 11. Connection type Provide details of the flanged or screwed connections. 12. Housing material State the preferred material of construction; this may be checked by the manufacturer from an evaluation of the mixture composition and operating conditions. 13. Element material State the preferred material of construction; this may be checked by the manufacturer from an evaluation of the mixture composition and operating conditions. 14. Construction Care should be taken when using materials, such as aluminium or plastics, which can cause incentive sparking or electrostatic charging. 15. Documentation State documentation requirements. 16. Regulations Applicable corporate and/or statutory regulations should be identified. page_57 page_58 |
| 58 | Annex C (informative)Best practice Manufacturers and users should be aware of the aspects listed below. a) Flame velocities and pressures of explosive mixtures can be enhanced by upstream turbulence, which can be caused by bends, valves or any change of cross section in the pipe. For in-line deflagration flame arresters, the pipelines on the unprotected side, i.e. the pipeline between ignition source and position of the flame arrester, should be as straight as possible without obstructions. b) Dynamic flame arresters are sensitive to turbulence and pressure drop caused by obstructions and longer pipelines on the protected side between the tank and the dynamic flame arrester. This might cause “hammering” or undamped oscillations. c) Flame arresters or/and flame arrester parts should be included in an existing equipotential bonding arrangement, if necessary. d) Flame arresters should not be positioned near hot equipment unless certified for the elevated temperature, as heat transfer to the flame arrester will reduce its performance and may cause it to fail. Therefore, in addition, the distance between neighbouring endurance burning end-of-line flame arresters should be more than five times the maximum diameter of the flame arrester. e) Continuous monitoring of pressure drop is advised if the process is known to contain particulates or substances which may block the element and over-pressurize the system. f) Shut-off devices should be fully open during normal operation. g) The suitability of a flame arrester should be checked if the process conditions or the pipe work configuration has been changed. h) Separate flow testing of flame arresters and pressure and/or vacuum valves used as combined but separate devices is not covered by this International Standard. i) The use of MESG as an unequivocal measure of flame arrester effectiveness has not been validated for all gas mixtures. MESG is also a function of p0. If there is any doubt as to the properties of any specific gas or combination of gases, further specialist advice should be sought (see Bibliography). j) Possible catalytic reaction can be avoided by properly choosing the material of the flame arrester. k) Flame arresters should be installed in accordance with the manufacturer’s operation manual and should be maintained regularly, depending on the existing operation conditions. If it is detected that a flash back (deflagration or detonation) or a stabilized burning has occurred at the device, the complete device needs to be checked. l) Flame arresters may be used in combination with additional protection measures. The overall safety of the combined installation shall be assessed, taking account of any hazardous area classification (zones) and of the likelihood of possible ignition sources. m) High stresses can be exerted on the fixing points of the flame arrester and on the unprotected side of the piping especially in the case of a detonation (high pressure shock wave); stresses between the flame arrester and the adjoining pipe work shall be limited to acceptable levels by appropriate installation, selection of material and construction. page_59 |
| 59 | Annex D (informative)Evaluation of test results / Figure D.1 – Decision process for stable detonation arrester (DET3 and DET4) / Figure D.2 – Decision process for unstable detonation arrester (DET1 and DET2) |
| 60 | Annex E (normative)Application E.1 General The general limits for use are as indicated below. a) The operational temperature, T0, shall be limited as follows: – −20 °C ≤ T0 ≤ 60 °C when testing is at atmospheric conditions (TTB ≤ 60 °C); – T0 ≤ TTB where TTB ≤ 150 °C (see 6.3.1, paragraph 4). b) The operational pressure p0 shall be limited as follows: 1) for flame arresters with measurable element: – end-of-line flame arresters with or without pressure and/or vacuum valve on the protected side: (0,8 × 105 Pa) ≤ p0 ≤ (1,1 × 105 Pa) when testing is at atmospheric pressure (pTB approximately 105 Pa); – in-line flame arresters: p0 ≤ pTB where pTB ≤ 1,6 × 105 Pa; 2) for flame arresters with non-measurable element: p0 ≤ 0,9 × pTB where pTB ≤ 1,6 × 105 Pa. Use shall be limited to gas-air mixtures with an MESG equal to or greater than that tested. All parts of the flame arrester shall resist the expected mechanical, thermal and chemical loads for the intended use. Where stabilized burning is considered as an additional hazard, flame arresters for short time burning shall be fitted with one or more integrated temperature sensors, taking into account the intended orientation of the flame arrester. The protected and unprotected side of a flame arrester may be modified to allow connection to smaller pipe sizes without further testing. The connection on the protected side shall not be smaller than the connection on the unprotected side. Materials for flame arresters shall be suitable for the intended use (e.g. temperature range, chemical properties of the gases and vapours). Type 1 detonation flame arresters are also suitable for use as Type 2, Type 3 and Type 4 without additional testing. Type 2 detonation flame arresters are also suitable for use as Type 4 without additional testing. Type 3 detonation flame arresters are also suitable for use as Type 4 without additional testing. E.2 Limits for use for static flame arresters E.2.1 In-line flame arrester E.2.1.1 General For an in-line flame arrester, the pipe diameter on the protected side shall be no less than the pipe diameter on the unprotected side |
| 61 | For an in-line flame arrester, the pipe diameter on the unprotected side shall be no greater than the flame arrester connection No instrument, tubing or other device whatsoever shall circumvent the flame arrester in such a manner to allow a flame path to exist around the flame element of the arrester. E.2.1.2 In-line deflagration flame arrester The use of in-line deflagration flame arresters tested in accordance with 7.3.2.2 shall be limited to the following conditions: a) the ratio of pipe length (between the potential ignition source and the flame arrester) and pipe diameter shall not exceed the tested ratio, Lu/D; b) at least 10 % of the cross sectional area of the pipe shall be open at the ignition source; c) pipe branches and valves on the unprotected side shall be installed as close as possible to the in-line deflagration flame arrester. E.2.2 Pre-volume flame arrester The use of pre-volume flame arresters shall be limited to enclosures, contents and pipe work on the unprotected side as used or simulated in the test. E.2.3 Detonation flame arrester Detonation flame arresters may be used for open and closed pipe work on the unprotected side. Detonation flame arresters tested at pTB are suitable for operational pressures p0 ≤ pTB in the same or smaller pipe size when the application is limited to mixtures with an MESG equal to or greater than that tested. NOTE An unstable detonation presents a higher level of hazard than a stable detonation (see 3.11). Unstable detonation flame arresters (Type 1 and Type 2) are designed and tested for stopping deflagrations and stable and unstable detonations. Stable detonation flame arresters (Type 3 and Type 4) are designed and tested for stopping deflagrations and stable detonations. E.2.4 Short time burn flame arrester If there are operating conditions which can lead to a stabilized burning at the flame arrester element, additional safety measures are required. Depending on the operating conditions, the devices shall be equipped with temperature sensors on one or two sides which initiate measures for the elimination of the stabilized burning (for example, emergency functions like switching-off the system, inerting or similar) and this within the half of the time for which the device is short-time burn proof (0,5 × tBT). When tBT is exceeded during a short-time burning situation, then the flame arresting safety cannot be assured. When operating with only one temperature sensor, the installation side (identification on side to be protected) has to be respected. Temperature sensors shall meet the flame arrester manufacturer’s specification, they shall be installed in the flame arrester according to the flame arrester manufacturer´s instructions. Temperature sensors shall be integrated into the control system so that safety measures to stop the stabilized burning are initiated. Prior to putting the devices with safety system into operation, the switching temperature shall be adjusted so that the admissible time period for the activating of the emergency measures will be observed. |
| 62 | E.3 Limits for use for liquid detonation flame arresters If a liquid product detonation flame arrester is satisfactorily tested for detonations, it may be considered acceptable for deflagrations without further testing. The operation pressure for the product-air mixture shall be limited to the test pressure. NOTE The operation pressure for the liquid flow is not limited by flame arresting requirements. Liquid product detonation flame arresters suitable for emptying operations shall have the flow rate restricted so that the pressure drop of the safety device that prevents loss of sealing liquid does not exceed the static pressure given by the immersion depth (see 8.1). For filling operations, there are no such limitations. E.4 Limits for use for dynamic flame arresters (high velocity vent valves) The use of a dynamic flame arrester shall be limited to ambient temperatures. The diameter of the connection of the dynamic flame arrester shall be at least DM, while the minimum gaseous volume (ullage space) available at any time in the protected tank shall not be less than VM. The equivalent pipe length on the protected side shall for pipe connection DM not exceed LM, as determined in A.4 and as successfully tested in 9.2.1. NOTE Equivalent pipe length is the length of straight pipe that would cause the same pressure drop under equivalent flow condition as the configuration including restrictions, e.g. bends, reducers. Calculation methods are given in e.g. Perry’s chemical engineer’s handbook. [11] E.5 Limits for use for hydraulic flame arresters The use of a hydraulic flame arrester shall be limited to the following conditions: a) the flow rate does not exceed the safe value, b) the operational immersion depth is kept above the tested minimum value, Z0min; c) the mixture on the unprotected side is at ambient temperature and pressure. Failure of any of the features listed under points a) to d) in 10.1 shall operate an alarm and stop the gas flow. If any temperature recorded in accordance with points c) and/or d) in 10.1 exceeds or falls below the specified limits, or if the minimum operational immersion depth Z0min falls below the specified level, or if the volume flow exceeds , the flow shall be stopped within 30 s. If for operational reasons the mixture flow cannot be stopped, it shall be inerted. The immersion depth at rest, ZR, and the operational immersion depth, Z0, shall not be less than the manufacturer’s recommended safety margin and greater than the minimum water seal immersion depth at rest, ZRmin, and the minimum operational water seal immersion depth, Z0min, at which the maximum volume flow, , has been established. The operational immersion depth, Z0, shall be maintained by automatic control of the water supply (see item (5) in Figure E.1) to ensure that the minimum operational immersion depth, Z0min, is not reached. |
| 63 | / |
| 64 | Key 1 container for the hydraulic flame arrester medium 2 gas or vapour mixture immersion pipe(s) 3 gas or vapour mixture inlet 4 water seal level indicator with an optical display 5 automatic water seal level control 6 mixture outlet pipe (length, L; diameter, D) 7 temperature sensor for alarm to indicate a stabilized flame above the water seal 8 water seal temperature sensor 9 mixture volume flow sensor 10 direction of mixture flow 11 direction of flame propagation 12 water seal 13 ignition source for flame transmission tests 14 ignition source for stabilized burning tests 15 flame detector for recording flame velocity 16 mixture outlet 17 filling height 18 flame detector to indicate flame transmission a = (25 ± 3) mm Figure E.1 – Test apparatus for hydraulic flame arresters |
| 65 | Bibliography [1] ISO 35111, Process measurement control functions and instrumentation — Symbolic representation — Part 1: Basic requirements [2] ISO 84211:1987, Fire protection — Vocabulary — Part 1: General terms and phenomena of fire [3] ISO 146177, Graphical symbols for diagrams — Part 7: Basic mechanical components [4] IEC 600794, Electrical apparatus for explosive gas atmospheres — Part 4: Method of test for ignition temperature [5] IEC ISO/IEC 80079-20-1:2017, Explosive atmospheres — Part 20-1: Material characteristics for gas and vapour classification — Test methods and data [6] IMO MSC/Circ. 677 Revised standards for the design, testing and locating of devices to prevent the passage of flame into cargo tanks in tankers [7] Brandes E., Redeker T. “Maximum experimental safe gap of binary and ternary mixtures” in The fourth international symposium on hazards, prevention and mitigation of industrial explosions, IV ISHPMIE October 2002, pp. 207-213, ISBN 2-86883-616-X [8] Brandes, E., März; G., Redeker, T. Normspaltweiten von Mehr-Brennstoffkomponenten-Gemischen in Abhängigkeit der Brennstoffzusammensetzung, Braunschweig, June 1997, ISBN 3-89429-994-0 [9] NFPA 69, Standard on Explosion Prevention Systems, 2014 edition, NFPA, 1 Batterymarch Park, Quincy, MA 02169-7471 USA [10] NFPA 497, Recommended practice for the classification of flammable liquids, gases or vapours and of hazardous (classified) locations for electrical installations in chemical process areas, 2012 edition, NFPA, 1 Batterymarch Park, Quincy, MA 02169-7471 USA [11] [Perry R.H., Green D.W. Perry’s chemical engineer’s handbook. Ninth Edition, 2019 |
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