1、BS ISO4126-9:2008ICS 13.240; 23.060.40NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDSafety devices forprotection againstexcessive pressurePart 9: Application and installation ofsafety devices excluding stand-alonebursting disc safety devicesThis British Standa
2、rdwas published under theauthority of the StandardsPolicy and StrategyCommittee on 31 October2008 BSI 2008ISBN 978 0 580 55250 2Amendments/corrigenda issued since publicationDate CommentsBS ISO 4126-9:2008National forewordThis British Standard is the UK implementation of ISO 4126-9:2008.The UK parti
3、cipation in its preparation was entrusted to TechnicalCommittee PVE/12, Safety devices.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisionsof a contract. Users are responsible for it
4、s correct application.Compliance with a British Standard cannot confer immunityfrom legal obligations.BS ISO 4126-9:2008Reference numberISO 4126-9:2008(E)ISO 2008INTERNATIONAL STANDARD ISO4126-9First edition2008-04-15Safety devices for protection against excessive pressure Part 9: Application and in
5、stallation of safety devices excluding stand-alone bursting disc safety devices Dispositifs de scurit pour protection contre les pressions excessives Partie 9: Application et installation des dispositifs de scurit autres que les dispositifs disque de rupture installs seuls BS ISO 4126-9:2008ISO 4126
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9、low. COPYRIGHT PROTECTED DOCUMENT ISO 2008 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the addr
10、ess below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2008 All rights reservedBS ISO 4126-9:2008ISO 4126-9:2008(E) ISO
11、2008 All rights reserved iiiContents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references . 1 3 Terms and definitions. 1 4 Risk consideration 3 5 Pressure limitation 4 5.1 General. 4 5.2 Setting of safety devices 5 6 Inlet line . 6 7 Outlet line 6 8 Installation . 8 8.1 General. 8 8.2
12、Installation of safety valves or the main valve of a CSPRS or a POSV. 8 8.3 Installation of safety valves and bursting disc safety devices in series or parallel 9 8.4 Isolation of safety devices . 10 9 Lifting device. 11 Annex A (informative) Safety device applications 12 Annex B (informative) Sizin
13、g of multiple safety devices 15 Annex C (informative) Sizing of inlet lines. 17 Annex D (informative) Calculation of built-up back pressure 22 Annex E (informative) Calculation of reaction forces. 29 Annex F (informative) Calculation of noise level 30 Bibliography . 31 BS ISO 4126-9:2008ISO 4126-9:2
14、008(E) iv ISO 2008 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body
15、 interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotec
16、hnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by
17、the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent righ
18、ts. ISO shall not be held responsible for identifying any or all such patent rights. ISO 4126-9 was prepared by Technical Committee ISO/TC 185, Safety devices for protection against excessive pressure. ISO 4126 consists of the following parts, under the general title Safety devices for protection ag
19、ainst excessive pressure: Part 1: Safety valves Part 2: Bursting disc safety devices Part 3: Safety valves and bursting disc safety devices in combination Part 4: Pilot-operated safety valves Part 5: Controlled safety pressure relief systems (CSPRS) Part 6: Application, selection and installation of
20、 bursting disc safety devices Part 7: Common data Part 9: Application and installation of safety devices excluding stand-alone bursting disc safety devices Part 10: Sizing of safety valves and connected inlet and outlet lines for gas/liquid two-phase flow BS ISO 4126-9:2008ISO 4126-9:2008(E) ISO 200
21、8 All rights reserved vIntroduction A safety device or system is the final element to protect pressure equipment from exceeding its allowable limits. Regulating and/or monitoring devices are not ultimate safety devices in the meaning of this International Standard. They become active in advance of a
22、n ultimate safety device (see Figure 1). It is important to consider not only the pressure-relieving device but also the whole of the equipment protected, so as not to reduce the relieving capacity or adversely affect the proper operation of the pressure-relieving devices, in order to ensure that th
23、e relieving pressure is not exceeded. The value of the relieving pressure is 1,x times the maximum allowable pressure, PS, where x is defined by a directive or national regulation. Operating problems can occur in pressure relief because of the selection of an inappropriate device or because a correc
24、tly selected device is adversely affected by improper handling, wrong installation or lack of maintenance. In some cases, it can be necessary to determine the basic details of the equipment protected so as to ensure that the maximum relieving pressure is not exceeded. NOTE 1 There can be requirement
25、s in a number of regulations to be respected and it is the responsibility of the user of this part of ISO 4126 to ensure compliance with these requirements. This part of ISO 4126 is also intended to draw attention to subjects that are not within its scope, but which are relevant to safety devices. N
26、OTE 2 To cover the essential requirements of the various regulations, a safety device needs to incorporate a whole range of products. Many of these products are covered by International Standards, but there are others that will either never be standardized or that will not be standardized within the
27、 foreseeable future. Where standards have already been produced, where work is known to be proceeding or where there is the intention of producing an applicable standard, reference is made to the standard concerned. Where there is no standard to which to refer, this part of ISO 4126 merely specifies
28、 the essential requirements of the device. BS ISO 4126-9:2008ISO 4126-9:2008(E) vi ISO 2008 All rights reservedKey X time Y pressure 1 reaction of regulating control system 2 reaction of monitoring system 3 reaction of safety system 4 normal operating range PSmaximum allowable pressure PS,accummaxim
29、um allowable accumulated pressure (PS 1,x) aNo continuous operation in this zone. Figure 1 Diagram of typical system relationship BS ISO 4126-9:2008INTERNATIONAL STANDARD ISO 4126-9:2008(E) ISO 2008 All rights reserved 1Safety devices for protection against excessive pressure Part 9: Application and
30、 installation of safety devices excluding stand-alone bursting disc safety devices 1 Scope This part of ISO 4126 covers the application and installations of safety devices such as safety valves, safety valves and bursting disc safety devices in combination, pilot-operated safety valves and controlle
31、d safety pressure-relief systems for the protection of pressure equipment. ISO 4126-6 covers the selection, application and installation of bursting disc safety devices. This part of ISO 4126 describes the normative requirements for applications and installations of safety devices to protect static
32、pressure equipment. The information contained in this part of ISO 4126 assumes single-phase flow of the fluid discharged from the safety device. ISO 4126-10 provides guidance specific to two-phase flow conditions. Equipment connected together in a system by piping of adequate capacity, which is free
33、 from potential blockages and does not contain any valve that can isolate any part, can be considered to be a safety system for the application of pressure relief. This part of ISO 4126 does not deal with other safety devices, such as safety related monitoring, control and regulation devices and oth
34、er limiting devices allowed by some national regulations. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (inc
35、luding any amendments) applies. ISO 4126-6, Safety devices for protection against excessive pressure Part 6: Application, selection and installation of bursting disc safety devices 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 safety device
36、 device that serves as the ultimate protection to ensure that the maximum allowable accumulated pressure is not exceeded EXAMPLE Safety valves, bursting disc safety devices, etc. BS ISO 4126-9:2008ISO 4126-9:2008(E) 2 ISO 2008 All rights reserved3.2 safety system system including the safety devices
37、and the interconnections between the equipment to be protected and any discharge connection to the nearest location of a safe disposal place NOTE This location can either be an atmospheric outlet or the connection into a safe collecting system or flare. 3.3 fail-safe status such that the pressure eq
38、uipment remains in a safe condition in case of failure of any safety system component or energy source 3.4 self-diagnosis regular and automatic determination that all chosen components of a safety system are capable of functioning as required 3.5 redundancy provision of more than one device or syste
39、m such that the necessary function will still be provided in case of failure of one or more of these devices 3.6 independence ability to function as required without interference from other equipment 3.7 hazard potential source of harm NOTE 1 The term “hazard” can be qualified in order to define its
40、 origin or the nature of the expected harm (see ISO/IEC Guide 51). NOTE 2 Harm is the physical injury or damage to the health of people, or damage to property or to the environment. 3.8 risk combination of the probability of occurrence of harm and the severity of that harm NOTE See ISO/IEC Guide 51.
41、 3.9 risk analysis use of available information to identify hazards and to estimate the risk NOTE See ISO/IEC Guide 51. 3.10 risk evaluation judgement on the basis of risk analysis as to whether a tolerable risk has been achieved NOTE See ISO/IEC Guide 51. 3.11 risk assessment overall process of ris
42、k analysis and risk evaluation NOTE See ISO/IEC Guide 51. BS ISO 4126-9:2008ISO 4126-9:2008(E) ISO 2008 All rights reserved 33.12 reliability ability to perform a required function under specified conditions and for a given period of time without failing 3.13 pressure limiter device which ensures th
43、at the permitted maximum allowable pressure is not exceeded during continuous operation NOTE It activates the means for correction, or provides for shutdown or shutdown and lockout. 3.14 safety freedom from unacceptable risk NOTE See ISO/IEC Guide 51. 3.15 maximum allowable pressure PSmaximum pressu
44、re for which the equipment is designed, as specified by the manufacturer 3.16 maximum/minimum allowable temperature TSmaximum/minimum temperatures for which the equipment is designed, as specified by the manufacturer 3.17 accumulated pressure pressure in the equipment to be protected which can excee
45、d maximum allowable pressure for a short duration during the operation of safety devices 3.18 maximum allowable accumulated pressure PS,accummaximum allowable value of the accumulated pressure in the equipment being protected which is fixed by national codes, regulations or directives 4 Risk conside
46、ration 4.1 All service conditions shall be considered when selecting the most appropriate safety concept, in order to ensure safe operation of the pressure equipment. This requires a realistic assessment of risk by means of risk analysis and risk evaluation. 4.2 Risk analysis involves, for example:
47、a) determination of the boundaries of the pressure equipment, including: 1) maximum quantity of fluid to be discharged, 2) intended use, 3) reasonably foreseeable misuse, 4) influences of sizing and flow of the safety device on operational reliability and performance of the safety system; b) identif
48、ication of potential hazards and estimation of the risk. BS ISO 4126-9:2008ISO 4126-9:2008(E) 4 ISO 2008 All rights reserved4.3 In particular, the risk analysis shall take in consideration the following: a) equipment connected together by piping of adequate capacity, which is free from potential blo
49、ckages and does not contain any valve that can isolate any part, may be considered as a system of pressurized components for the application of pressure relief; b) where a component failure during operation is foreseen and would cause the pressure of fluid in the vessel to exceed the maximum allowable pressure, this failure shall be considered when evaluating the total capacity of the safety device(s); c) vessels that are to operate completely filled with liquid and can be isolated shall be equipped with a safety
