1、 THE ENGINEERING EQUIPMENT AND MATERIALS USERS ASSOCIATION Guide to the Isolation of Pressure Relieving Devices PUBLICATION 184 Edition 2 Released by IHS. Not for resale THE ENGINEERING EQUIPMENT AND MATERIALS USERS ASSOCIATION Guide to the Isolation of Pressure Relieving Devices PUBLICATION 184 Edi
2、tion 2 Copyright 2009 The Engineering Equipment and Materials Users Association. A company limited by guarantee. Registered in England. Company number 477838. ISBN 0 85931 170 8 Imprint reference 05-2009 Registered and Trading Address 10-12 Lovat Lane London EC3R 8DN Telephone: +44 (0)20 7621 0011 F
3、ax: +44 (0)20 7621 0022 E-mail: saleseemua.org Website: www.eemua.org EEMUA Publication 184 - Guide to the Isolation of Pressure Relieving Devices EEMUA ii ENGINEERING EQUIPMENT AND MATERIALS USERS ASSOCIATION The Engineering Equipment and Materials Users Association, more commonly known as EEMUA, i
4、s a European non-profit membership Association helping companies that own or operate industrial facilities - the users of engineering equipment and materials. EEMUA aims to improve the safety, environmental and operating performance of industrial facilities in the most cost-effective way, thereby de
5、monstrating and pursuing leadership in asset management. EEMUA Members pursue these aims through collaboration for mutual benefit, sharing engineering experiences and expertise and by promoting their distinct interests as the users of engineering products. Specifically, the aims of EEMUA Member comp
6、anies are achieved by: providing the organisation within which networking, information sharing and collaboration on non-competitive technical matters can take place; influencing the way written regulations are interpreted and applied in practice; presenting and promoting Members views, and encouragi
7、ng the application of good, sound engineering practices; developing user guides, specifications, training and competency schemes; facilitating Members participation in national and international standards making; influencing relevant national and European legislation and regulations. Formed in 1949
8、as the Engineering Equipment Users Association, and re-named in 1983 (as a result of taking over the materials association, OCMA), EEMUA has for more than fifty years given companies that own and operate process plants, power stations and other significant industrial facilities, a collaborative voic
9、e in addressing technical and engineering related issues that impact on good integrity management and asset management practices. The Association is open to companies of all sizes that meet its engineering user criteria. Further details of current Members of EEMUA is available on the Associations we
10、bsite, www.eemua.org. EEMUA activities often lead to the production of publications. These are prepared for Members use and are often offered for sale as well. A list of EEMUA publications for sale is given at the end of this Publication. The full list is also on the Associations website, including
11、details of on-line shopping facilities. To enquire about corporate Membership, write to enquirieseemua.org or call +44 (0)20 7621 0011. EEMUA Publication 184 - Guide to the Isolation of Pressure Relieving Devices EEMUA iiiABOUT THIS PUBLICATION Legal Aspects All rights, title and interest in this Pu
12、blication shall belong to EEMUA. All rights are reserved. No part of this Publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means: electronic, mechanical, photocopying, recording or other, without the express prior written agreement of the EEMUA Execut
13、ive Director. Infringement of copyright is illegal and also reduces the Associations income thereby jeopardising its ability to fund the production of future publications. It has been assumed in the preparation of this Publication that: the user will ensure selection of those parts of its contents a
14、ppropriate to the intended application; and that such selection and application will be correctly carried out by appropriately qualified and competent persons for whose guidance this Publication has been prepared. EEMUA and the individual members of the Work Group that prepared this EEMUA Publicatio
15、n do not, and indeed cannot, make any representation or give any warranty or guarantee in connection with material contained herein. EEMUA and the individual members of the Work Group that prepared this EEMUA Publication expressly disclaim any liability or responsibility for damage or loss resulting
16、 from the use or reliance on this Publication. Any recommendations contained herein are based on the most authoritative information available at the time of writing and on current good engineering practice, but it is essential for the user to take account of pertinent subsequent developments and/or
17、legislation. Any person who encounters an inaccuracy or ambiguity when making use of this Publication is asked to notify EEMUA without delay so that the matter may be investigated and appropriate action taken. Consultation and Feedback EEMUA encourages constructive comments on this Publication from
18、both Members of the Association and others. Comments should be sent on the standard feedback form, a copy of which is provided towards the end of this Publication. An electronic version of the feedback form is available from EEMUA - e-mail your request for a copy to enquirieseemua.org, telephone you
19、r request to +44 (0)20 7621 0011, or download the form from the EEMUA website at www.eemua.org. Submit comments by e-mail (preferred) or post. Comments will be considered by the relevant EEMUA Technical Committee and may be incorporated in future editions of this Publication. New editions will be pu
20、blicised on the EEMUA website. EEMUA Publication 184 - Guide to the Isolation of Pressure Relieving Devices EEMUA iv EEMUA Publication 184 - Guide to the Isolation of Pressure Relieving Devices EEMUA vTable of Contents Foreword 1 1. Introduction and Scope .3 2. Philosophy 5 3. Legislation and Standa
21、rds .7 3.1 Legislation 7 3.2 Standards . 7 4. Single Relief Devices .9 4.1 General 9 4.2 Thermal Relief . 9 4.3 Parallel Process Streams . 9 4.4 Toxic and Corrosive Services . 9 4.5 Isolation of Source of Excessive Pressure 12 5. Duplicated Relief Devices 13 5.1 Relief capacity requirements 13 5.2 T
22、oxic and Corrosive Services . 13 5.4 Pilot Operated Safety Valves 13 5.4 Multiple Relieving Devices . 14 6. Types of Mechanical Locking System . 15 6.1 General 15 6.2 Tagging or Car Sealing 15 6.3 Padlock and Chain/Locking Plate 15 6.4 Three-way Valves 15 6.5 Full Interlocking System . 16 7. Control
23、 Procedures 19 8. Selection and Installation 21 8.1 Valve Type and Selection 21 8.2 Pressure Drop . 21 8.3 Access 22 8.4 Installation . 22 8.5 Venting and Draining 22 8.6 Spectacle Blinds 22 8.7 Materials 22 8.8 Identification . 22 9. References and Bibliography . 23 9.1 Standards . 23 9.2 Other Pub
24、lications 24 Table of Figures Figure 1 Use of key interlock in relief of blocked-in liquid filled system . 10 Figure 2 Typical methods of isolating relief devices from common discharge header . 11 Figure 3 Isolation of source of excessive pressure . 12 Figure 4 System having multiple relieving devic
25、es with changeover facility 14 Figure 5 Mechanical interlock for quarter-turn valves . 17 Figure 6 Example of mechanical interlock frame . 18 EEMUA Publication 184 - Guide to the Isolation of Pressure Relieving Devices EEMUA vi EEMUA Publication 184 - Guide to the Isolation of Pressure Relieving Dev
26、ices EEMUA 1 Foreword In order to permit their removal and replacement without plant shutdown, pressure relieving devices may need to be isolated from the equipment they protect. The installation of isolating valves around protective devices is, however, potentially hazardous as it introduces the ri
27、sk of a system being left unprotected against over-pressure due to the relief path to atmosphere or to the relief system being inadvertently closed off. Existing standards offer little or no detailed guidance in this area. The EEMUA Pressure Relieving Safety Systems Technical Committee has developed
28、 this guide from the experience and practices of its member companies in the petroleum, chemical and power industries. The document expands on the guidance given in API RP 520 Part II. Revisions to Second Edition This second edition revises and updates the original 1996 edition. The changes made cla
29、rify and add important points to the existing text and update the references. In addition, the figures have been moved into the text. Units This document employs SI units, but additionally uses Imperial units where appropriate to common usage. EEMUA Publication 184 - Guide to the Isolation of Pressu
30、re Relieving Devices EEMUA 2 EEMUA Publication 184 - Guide to the Isolation of Pressure Relieving Devices EEMUA 3 1. Introduction and Scope This document sets out guidance for the installation and operation of isolating valves which allow the removal of relief devices from operating plant. It draws
31、on the experience and different practices of EEMUA members to identify the key points which should be considered in the design and management of such isolation systems. The term isolation valve/device may be interpreted to include spectacle blinds/ slip plates where these are used instead of valves
32、for the isolation of relief devices. The term relief/relieving device normally refers to a safety/relief valve, bursting disc or other mechanical relieving device. Important: None of the comments or recommendations made in this guide removes from the designer and/or user the responsibility of ensuri
33、ng that the relief device installation is safe and that it complies with the applicable national and industry standards and regulatory requirements. Note on terminology: The terms relief valve, safety valve and safety relief valve are widely used in industry and have specific meanings in US standard
34、s; however, only safety valve is defined in ISO standards (see API RP 520 Part I and ISO 4126). No distinction is made between these terms in this guide. EEMUA Publication 184 - Guide to the Isolation of Pressure Relieving Devices EEMUA 4 EEMUA Publication 184 - Guide to the Isolation of Pressure Re
35、lieving Devices EEMUA 5 2. Philosophy Inspection and maintenance of pressure relieving devices are often required at more frequent intervals than are plant shutdowns for other routine maintenance. Therefore the means to remove pressure relieving devices without affecting plant operation is desirable
36、 in many cases. This may necessitate the installation of one or more additional relieving devices together with provision for their isolation. Such isolation, however, introduces the possibility of a vessel or system being inadvertently closed off from its relieving device during normal operation, w
37、ith the consequential risk of the equipment being subjected to excessive pressure. Isolation should therefore be installed only where essential and where the risks have been thoroughly evaluated (further information can be found in the British Health they should also take account of any special prov
38、isions within the standard. While many national standards concerning pressure vessels or systems do not preclude the use of isolating valves around relief devices, certain standards currently prohibit such installations (e.g. EN 12952 for water-tube boilers and EN 12953 for shell type boilers). Wher
39、e allowed, the installation of valves to enable relief devices to be isolated from an operating pressure system will require the designer or user to ensure that sufficient* relief capacity for the system is available at all times during which the system is at risk. This may necessitate the installat
40、ion of additional devices and the implementation of procedures over and above those which would otherwise have been required, to ensure the system is adequately protected at all times. The guidance given in this document assumes that the applicable standard does not disallow the use of isolating val
41、ves. * Note: When less than full relief capacity would be available during the period of isolation, risk assessment techniques should be used to justify the level of available relief capacity considered to be sufficient. EEMUA Publication 184 - Guide to the Isolation of Pressure Relieving Devices EE
42、MUA 8 EEMUA Publication 184 - Guide to the Isolation of Pressure Relieving Devices EEMUA 9 4. Single Relief Devices 4.1 General Isolation of a single relief device to permit its removal and immediate replacement during normal operations means that the pressurised system will be temporarily unprotect
43、ed during the time it takes to remove/replace the device. The risks from all foreseeable upset conditions - such as external fire, process upset, thermal expansion, etc. - that might occur during the temporary absence of relieving capacity should be carefully evaluated before such isolation is insta
44、lled. There are particular hazards associated with the isolation of single relief devices. Arrangements for such isolation should always be supported by suitable control procedures (see Chapter 7). 4.2 Thermal Relief Where relief is required of liquid trapped within a vessel or between isolating val
45、ves in a piping system, it may be necessary to ensure removal and replacement of the thermal relief device whilst maintaining the system on line. A key interlock system between one of the plant isolation valves and the relief system isolation device (see Figure 1) may be used to ensure that an unacc
46、eptable pressure rise due to locked-in fluid cannot occur. Alternatively, isolation of thermal relief devices may be justified through risk assessment, taking into account the historical frequency of a relief event, the actual dead time during which isolation of the relief device occurs and the like
47、ly consequences of an overpressure incident. 4.3 Parallel Process Streams Where parallel process streams are in use and single relief devices discharge into a common header, it may be necessary to isolate the relief devices from the common discharge header to allow for maintenance activities whilst
48、keeping the remainder of the discharge system on line (see Figure 2). A tagging or padlock-and-chain system for the isolating valve in the downstream pipework may be used to ensure that the isolating valve is never left in the closed position whilst the particular process stream is in use. This is d
49、iscussed in more detail in Chapter 6. 4.4 Toxic and Corrosive Services The installation of isolation devices upstream or on both sides of single pressure relieving devices may be justified in toxic and/or corrosive service for the purpose of protecting personnel engaged in removal/replacement of the relieving devices when the plant is not operational but not gas free. Normal safety precautions necessary for the removal of items of equipment from systems containing toxic/ corrosive fluids would also need to be observed. EEMUA P
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