1、Flame Arresters for Vents of Tanks Storing Petroleum ProductsAPI RECOMMENDED PRACTICE 2210THIRD EDITION, MAY 2000REAFFIRMED, MARCH 2015Flame Arresters for Vents of Tanks Storing Petroleum ProductsDownstream SegmentAPI RECOMMENDED PRACTICE 2210THIRD EDITION, MAY 2000REAFFIRMED, MARCH 2015SPECIAL NOTE
2、SAPI publications necessarily address problems of a general nature. With respect to partic-ular circumstances, local, state, and federal laws and regulations should be reviewed.API is not undertaking to meet the duties of employers, manufacturers, or suppliers towarn and properly train and equip the
3、ir employees, and others exposed, concerning healthand safety risks and precautions, nor undertaking their obligations under local, state, or fed-eral laws.Information concerning safety and health risks and proper precautions with respect to par-ticular materials and conditions should be obtained fr
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5、atent. Neither should anything contained in the publication be con-strued as insuring anyone against liability for infringement of letters patent.Generally, API recommended practices are reviewed and revised, reafrmed, or with-drawn at least every ve years. Sometimes a one-time extension of up to tw
6、o years will beadded to this review cycle. This publication will no longer be in effect ve years after itspublication date as an operative API recommended practice or, where an extension has beengranted, upon republication. Status of the publication can be ascertained from the APIDownstream Segment
7、telephone (202) 682-8000. A catalog of API publications and mate-rials is published annually and updated quarterly by API, 1220 L Street, N.W., Washington,D.C. 20005.This document was produced under API standardization procedures that ensure appropri-ate notication and participation in the developme
8、ntal process and is designated as an APIstandard. Questions concerning the interpretation of the content of this recommended prac-tice or comments and questions concerning the procedures under which this standard wasdeveloped should be directed in writing to the director of the Downstream Segment, A
9、meri-can Petroleum Institute, 1220 L Street, N.W., Washington, D.C. 20005. Requests for permis-sion to reproduce or translate all or any part of the material published herein should also beaddressed to the general manager.API recommended practices are published to facilitate the broad availability o
10、f proven,sound engineering and operating practices. These recommended practices are not intendedto obviate the need for applying sound engineering judgment regarding when and wherethese standards should be utilized. The formulation and publication of API recommendedpractices is not intended in any w
11、ay to inhibit anyone from using any other practices.Any manufacturer marking equipment or materials in conformance with the markingrequirements of an API recommended practice is solely responsible for complying with allthe applicable requirements of that recommended practice. API does not represent,
12、 warrant,or guarantee that such products do in fact conform to the applicable API standard.All rights reserved. No part of this work may be reproduced, stored in a retrieval system, or transmitted by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written perm
13、ission from the publisher. Contact the Publisher, API Publishing Services, 1220 L Street, N.W., Washington, D.C. 20005.Copyright 2000 American Petroleum InstituteFOREWORDThis publication is intended to provide guidelines for evaluating the need for the use ofame arresters on the vents of tanks stori
14、ng petroleum products.API publications may be used by anyone desiring to do so. Every effort has been made bythe Institute to assure the accuracy and reliability of the data contained in them; however, theInstitute makes no representation, warranty, or guarantee in connection with this publicationan
15、d hereby expressly disclaims any liability or responsibility for loss or damage resultingfrom its use or for the violation of any federal, state, or municipal regulation with which thispublication may conict.Suggested revisions are invited and should be submitted to the director of the DownstreamSeg
16、ment, American Petroleum Institute, 1220 L Street, N.W., Washington, D.C. 20005.iiiCONTENTSPage1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 SCOPE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17、 . . . . . . . . . . . . . . . . . . . . . . . . . . 23 BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 FLAME ARRESTERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 P
18、RESSURE-VACUUM VALVES AS A SUBSTITUTE FOR FLAME ARRESTERS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 SUMMARY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19、 37 CONCLUSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4v1Flame Arresters for Vents of Tanks StoringPetroleum Products1 Introduction1.1In addition to connections for liquid entry and with-drawal, every atmospheric xed-roof tank
20、requires a vent thatallows escape or entry of air and/or vapors to avoid develop-ment of pressure or vacuum conditions sufcient to damagethe tank during liquid transfer or changes in ambient condi-tions. This publication discusses the benets and detrimentsassociated with the use of ame arresters on
21、these vents.1.1.1The provisions of this publication are intended foruse when designing new facilities or when considering majorexpansions. It is not intended that the recommendations inthis publication be applied retroactively to existing facilities.This publication also can be used as guidance when
22、 there is aneed or desire to review existing facilities.1.2NFPA 30, Flammable and Combustible LiquidsCode,lists requirements for tank vents in which ammable andcombustible liquids are stored. API Standard 2000, VentingAtmospheric and Low-Pressure StorageTanks, and NFPA 30cover the size and venting c
23、apacity to accommodate normaland emergency conditions of the tanks. Devices that are nor-mally closed, except when operating under pressure or vac-uum conditions, are often called pressure-vacuum valves.Such valves are normally required for ammable liquids (seeNFPA 30). Additional information on ven
24、ts and pressure-vac-uum valves can be found in API Standard 620, Design andConstruction of Large, Welded Low-Pressure Storage Tanks,and API Standard 650, Welded Steel Tanks for Oil Storage.Under certain circumstances, ame arresters listed by theUnderwriters Laboratories or approved by the FactoryMut
25、ual Engineering and Research Corporation are used inconjunction with, or in lieu of, a pressure-vacuum valve. Thepublications cited are considered standards for good practice,and may be incorporated in mandatory codes or ordinances insome jurisdictions.1.3The most recent edition or revision of each
26、of the fol-lowing standards, codes, and publications are referenced inthis Publication as useful sources of additional informationsupplementary to the text. Additional information may beavailable from the cited Internet World Wide Web sites.APIwww.api.orgStd 620Design and Construction of Large, Weld
27、edLow-Pressure Storage TanksStd 650Welded Steel Tanks for Oil StorageStd 2000Venting Atmospheric and Low-PressureStorage TanksPubl 2028Flame Arresters in Piping SystemsRP12NRecommended Practice for the Operation,Maintenance and Testing of Firebox FlameArrestersAIChE1(CCPS)www.aiche.org/docs/ccpsGuid
28、elines for Engineering Design for Process SafetyFMApproval GuideA Guide to Equipment, Materials the use of this combination in the ensuing years has con-rmed this report.4 Flame Arresters4.1The term ame arrester describes a device or form ofconstruction that will allow free passage of a gas or gaseo
29、usmixture but will interrupt or prevent the passage of ame. Itprevents the transmission of ame through a ammable gas/air mixture by quenching the ame on the high surface areaprovided by an array of small passages through which theame must pass. The emerging gases are cooled enough toprevent ignition
30、 on the protected side. Effective and reliablearresting devices are designed for many specic situations.The metal screen in the coal miners Davy safety lamp andthe tiny passages in the sintered metal powder device in acombustible gas indicator are examples of ame-arrestingdevices.4.2Arresters have b
31、een made incorporating wire screens,small metal tubes, drilled holes, or passages between inter-leaved corrugated and at sheets of metal for use on tanksstoring gasoline and similar ammable liquids. Such deviceshave been tested and listed as acceptable by the UnderwritersLaboratories or approved by
32、the Factory Mutual InsuranceCompany. The listing is based on tests made with mixtures ofhydrocarbon vapor and air of maximum explosiveness, withprescribed limitations on the manner of installation. Forexample, a pipe extension on the atmospheric side of thearrester that is longer than the extension
33、used in the test inval-idates the listing (see Underwriters Laboratories Gas and OilEquipment Directoryand the Factory Mutual ApprovalGuide). For other vapors or gases and for installations that donot conform to the arrangement described in the listing, thereis no assurance that the arrester will be
34、 effective.4.3Problems in the application and maintenance of tankame arresters occur from a number of causes such as:1. The tank vapor must pass through the arresters narrowpassages causing a friction loss that may reduce the owcapacity below that of an open pipe or a vent pipe with apressure-vacuum
35、 valve of comparable size. Thus, thepressure drop must be considered when a ame arrester isselected.2. Narrow passages can clog with dust, scale, polymers orairborne debris. A rigorous maintenance program is nec-essary to avoid vent plugging and the possibility ofpressure or vacuum-related damage to
36、 the tank roof.3. The water bottoms of certain petroleum tanks producehigh-humidity in the vapor space. Ice can accumulate andclog the arrester in freezing weather and jeopardize thetank. External environmental icing conditions can alsocause arrester plugging. To remedy an icing situation, thearrest
37、er must be heated or removed. Since removal wouldnullify the protection for which the arrester was installed,heat tracing may be required.4. The need for periodic inspecting and cleaning affordopportunities for errors in reassembly, possibly makingthe arrester incapable of stopping ame.5. A listed a
38、me arrester is not reliable indenitely, evenin perfect conditions. Although the mixture of hydrocar-FLAMEARRESTERSFORVENTSOFTANKSSTORINGPETROLEUMPRODUCTS3bon vapor and air employed in the UnderwritersLaboratories tests is the mixture most likely to ashthrough a narrow passage, evidence exists that a
39、 richermixture could burn at the inlet of the ame arrester andproduce heat damage which may render the device inca-pable of preventing ame propagation. UL 525 includesan Endurance Burn Testand aContinuous Flame Testtotest ashback potential. Arresters categorized as Type I aretested using the Enduran
40、ce Burn Testwhich requires a reto burn from the ame arresters exit for at least two hoursafter which time ashback should not occur. Type IIarresters are designed to resist ashback in the UL 525Continuous Flame Testwhich requires a ame to burnfrom the exit of the ame arrester during ten minute inter-
41、vals for at least one hour.6. Flame arrester maintenance requires safe access toavoid placing personnel at risk and to facilitate efciency.4.4The above limitations are recognized in NFPA 30 (seeparagraph 23.5.7) and in the paragraphs introducing theproducts in the Underwriters Laboratory Gas and Oil
42、Equip-ment Directory and the Factory Mutual ApprovalGuide.5 Pressure-Vacuum Valves As a Substitute For Flame Arresters5.1NFPA 30 and OSHA 1910.106(b)(2)(iv)(f) recognizethat a pressure-vacuum valve is an acceptable alternative to aame arrester under certain circumstances. This recognitionis based on
43、 tests started in 1920, supplemented by many yearsof experience.5.2Even in mixtures of maximum ammability, ame can-not pass back through an opening if the efux velocityexceeds a critical value. Tests by the Bureau of Mines andothers made with mixtures of gasoline components and airowing through open
44、ings typical of tank vents have demon-strated that this critical velocity is approximately 10 feet persecond. In a valve set to close when the upstream pressurefalls below approximately 3/4inch of water, the velocity ofow across the pallet-seat area exceeds twice this criticalvelocity. The ame propa
45、gation cannot overcome the gasow to pass from the low-pressure to the high-pressure side.In these tests, ame was snuffed out when the valve closed asthe upstream pressure was deliberately reduced to test andconrm this condition. Chapter 13 of the AIChE CCPS book,Guidelines for Engineering Design for
46、 Process Safety, dis-cusses ame arresters and cites test work done which sub-stantiates velocity ame stopping.5.3Tests have also shown that under some circumstancesa long-burning ame at the valve outlet could damage thevalve sufciently to interfere with its closing. Under suchcircumstances, ashback
47、may occur when the ow rate fallsbelow the critical velocity, if a ammable mixture existsinside the tank. 6 Summary6.1The desire to protect a tank vent from ashback is basedon the theoreticalpotential for a simultaneous occurrence ofan ignition source in the vicinity of the vent and the releasefrom t
48、he vent of a mixture capable of transmitting ame.6.2Ignition sources such as open ames usually are, andcertainly can be, excluded from the vicinity of tank vents.Falling embers, unless actually aming, are not an ignitionsource for petroleum vapors. Lightning is a potential ignitionsource, as demonst
49、rated by the occasional ignition of ventstacks that release vapor continuously. However, such stacksare usually taller and thus a much more attractive target forlightning than a tank vent.6.3The availability of a mixture capable of producingashback must be considered. Stocks stored at temperaturesbelow their ash points do not produce ignitable mixtures inthe vapor space. Crude oil and gasoline generally producemixtures too rich to transmit ame. Expelled vapor, if ignited,will burn as a torch unt
