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1、 Reference number ISO 4126-1:2004(E) ISO 2004 INTERNATIONAL STANDARD ISO 4126-1 Second edition 2004-02-15 Safety devices for protection against excessive pressure Part 1: Safety valves Dispostifs de scurit pour protection contre les pressions excessives Partie 1: Soupapes de sret ISO 4126-1:2004(E)
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5、04 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 address below or ISOs member body in the cou
6、ntry 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 2004 All rights reserved ISO 4126-1:2004(E) ISO 2004 All rights reserved iii Foreword ISO (the Internatio
7、nal 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 interested in a subject for which a technical committee has been
8、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 Electrotechnical Commission (IEC) on all matters of electrotechnical standar
9、dization. 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 the technical committees are circulated to the member bodies for v
10、oting. 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 rights. ISO shall not be held responsible for identifying any or all s
11、uch patent rights. ISO 4126-1 was prepared by the European Committee for Standardization (CEN) in collaboration with Technical Committee ISO/TC 185, Safety devices for protection against excessive pressure, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreeme
12、nt). Throughout the text of this document, read “.this European Standard.“ to mean “.this International Standard.“. This second edition cancels and replaces the first edition (ISO 4126-1:1991), which has been technically revised. ISO 4126 consists of the following parts, under the general title Safe
13、ty devices for protection against 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, s
14、election and installation of bursting disc safety devices Part 7: Common data For the purposes of this part of ISO 4126, the CEN annex regarding fulfilment of European Council Directives has been removed. ISO 4126-1:2004(E) iv ISO 2004 All rights reserved Contents Page 1Scope 1 2Normative references
15、 1 3Terms and definitions2 4Symbols and units.5 5Design.5 5.1General5 5.2End connections6 5.3Minimum requirements for springs8 5.4Materials8 6Production testing .8 6.1Purpose.8 6.2General8 6.3Hydrostatic testing 9 6.4Pneumatic testing10 6.5Adjustment of cold differential test pressure.11 6.6Seat lea
16、kage test11 7Type testing11 7.1General11 7.2Tests to determine operating characteristics.12 7.3Tests to determine flow characteristics 14 7.4Determination of the coefficient of discharge 15 7.5Certification of coefficient of discharge16 8Determination of safety valve performance16 8.1Determination o
17、f coefficient of discharge.16 8.2Critical and subcritical flow16 8.3Discharge capacity at critical flow.16 8.4Discharge capacity for any gas at subcritical flow 17 8.5Discharge capacity for non-flashing liquid as the test medium in the turbulent zone where the Reynolds number Re is equal to or great
18、er than 80 00017 9Sizing of safety valves.17 9.1General17 9.2Valves for gas or vapour relief .18 9.3Calculation of capacity18 10Marking and sealing 19 10.1Marking on the shell of a safety valve .19 10.2Marking on an identification plate19 10.3Sealing of a safety valve .19 Annex A (informative) Examp
19、les of sizing calculations for various fluids20 A.1Capacity calculations for gaseous media at critical flow (see 9.3.3.1) 20 A.2Capacity calculations for gaseous media at subcritical flow (see 9.3.3.2)22 A.3Capacity calculations for liquids (see 9.3.4).24 Foreword .v ISO 4126-1:2004(E) ISO 2004 All
20、rights reserved v Foreword This document (EN ISO 4126-1:2004) has been prepared by Technical Committee CEN/TC 69 “Industrial valves”, the secretariat of which is held by AFNOR, in collaboration with Technical Committee ISO/TC 185 “Safety devices for protection against excessive pressure”. This Europ
21、ean Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by August 2004, and conflicting national standards shall be withdrawn at the latest by August 2004. This document has been prepared under a mandate given to CEN
22、by the European Commission and the European Free Trade Association, and supports essential requirements of EU Directive. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium,
23、 Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and the United Kingdom. This standard for safety devices for protection against excessive pressure consists of seven pa
24、rts of which this is Part 1. The various parts are: 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 : Applicatio
25、n, selection and installation of bursting disc safety devices Part 7 : Common data Part 7 contains data that is common to more than one of the parts of this standard to avoid unnecessary repetition. 1 Scope This part of this European Standard specifies general requirements for safety valves irrespec
26、tive of the fluid for which they are designed. It is applicable to safety valves having a flow diameter of 6 mm and above which are for use at set pressures of 0,1 bar gauge and above. No limitation is placed on temperature. This is a product standard and is not concerned with applications for safet
27、y valves. 2 Normative references This European Standard incorporates by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to
28、 or revisions of any of these publications apply to this European Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies (including amendments). EN 1092-1, Flanges and their joints Circular flanges for pipes, v
29、alves, fittings and accessories PN designated Part 1: Steel flanges. EN 1092-2, Flanges and their joints Circular flanges for pipes, valves, fittings and accessories PN designated Part 2: Cast iron flanges. EN 1092-3, Flanges and their joints Circular flanges for pipes, valves, fittings and accessor
30、ies PN designated Part 3: Copper alloy flanges. prEN 1759-1, Flanges and their joints - Circular flanges for pipes, valves, fittings and accessories, Class designated - Part 1: Steel flanges NPS 1/2 to 24. EN 12516-3, Valves Shell design strength Part 3: Experimental method. EN 12627, Industrial Val
31、ves Butt welding ends for steel valves. EN 12760, Valves Socket welding ends for steel valves. EN ISO 6708, Pipework components Definition and selection of DN (nominal size) (ISO 6708:1995). ISO 7-1, Pipe threads where pressure-tight joints are made on the threads Part 1: Dimensions, tolerances and
32、designation. ANSI B1.20.1, NPT threads. ISO 4126-1:2004(E) ISO 2004 All rights reserved 1 3 Terms and definitions For the purposes of this European Standard, the following terms and definitions apply. 3.1 safety valve valve which automatically, without the assistance of any energy other than that of
33、 the fluid concerned, discharges a quantity of the fluid so as to prevent a predetermined safe pressure being exceeded, and which is designed to re-close and prevent further flow of fluid after normal pressure conditions of service have been restored NOTEThe valve can be characterised either by pop
34、action (rapid opening) or by opening in proportion (not necessarily linear) to the increase in pressure over the set pressure. 3.1.1 types of safety valve 3.1.1.1 direct loaded safety valve safety valve in which the loading due to the fluid pressure underneath the valve disc is opposed only by a dir
35、ect mechanical loading device such as a weight, lever and weight, or a spring 3.1.1.2 assisted safety valve safety valve which, by means of a powered assistance mechanism, may additionally be lifted at a pressure lower than the set pressure and will, even in the event of failure of the assistance me
36、chanism, comply with all the requirements for safety valves given in this standard 3.1.1.3 supplementary loaded safety valve safety valve which has, until the pressure at the inlet to the safety valve reaches the set pressure, an additional force which increases the sealing force NOTE 1This addition
37、al force (supplementary load), which may be provided by means of an extraneous power source, is reliably released when the pressure at the inlet of the safety valve reaches the set pressure. The amount of supplementary loading is so arranged that if such supplementary loading is not released, the sa
38、fety valve will attain its certified discharge capacity at a pressure not greater than 1,1 times the maximum allowable pressure of the equipment to be protected. NOTE 2Other types of supplementary loaded safety devices are dealt with in Part 5 of this standard. 3.1.1.4 pilot operated safety valve sa
39、fety valve, the operation of which is initiated and controlled by the fluid discharged from a pilot valve which is itself a direct loaded safety valve subject to the requirement of this standard NOTEOther types of pilot operated safety valves with flowing, non-flowing and modulating pilots are in Pa
40、rt 4 of this standard. 3.2 pressure pressure unit used in this standard is the bar (1 bar = 105 Pa), quoted as gauge (relative to atmospheric pressure) or absolute as appropriate ISO 4126-1:2004(E) 2 ISO 2004 All rights reserved 3.2.1 set pressure predetermined pressure at which a safety valve under
41、 operating conditions commences to open NOTEIt is the gauge pressure measured at the valve inlet at which the pressure forces tending to open the valve for the specific service conditions are in equilibrium with the forces retaining the valve disc on its seat. 3.2.2 maximum allowable pressure, PS ma
42、ximum pressure for which the equipment is designed as specified by the manufacturer 3.2.3 overpressure pressure increase over the set pressure, at which the safety valve attains the lift specified by the manufacturer, usually expressed as a percentage of the set pressure NOTEThis is the overpressure
43、 used to certify the safety valve. 3.2.4 reseating pressure value of the inlet static pressure at which the disc re-establishes contact with the seat or at which the lift becomes zero 3.2.5 cold differential test pressure inlet static pressure at which a safety valve is set to commence to open on th
44、e test bench NOTEThis test pressure includes corrections for service conditions, e.g. back pressure and/or temperature. 3.2.6 relieving pressure pressure used for the sizing of a safety valve which is greater than or equal to the set pressure plus overpressure 3.2.7 built-up back pressure pressure e
45、xisting at the outlet of a safety valve caused by flow through the valve and the discharge system 3.2.8 superimposed back pressure pressure existing at the outlet of a safety valve at the time when the device is required to operate NOTEIt is the result of pressure in the discharge system from other
46、sources. 3.2.9 balanced bellows bellows device which minimises the effect of superimposed back pressure on the set pressure of a safety valve 3.2.10 blowdown difference between set and reseating pressures, normally stated as a percentage of set pressure except for pressures of less than 3 bar when t
47、he blowdown is expressed in bar 3.3 lift actual travel of the valve disc away from the closed position ISO 4126-1:2004(E) ISO 2004 All rights reserved 3 3.4 flow area minimum cross-sectional flow area (but not the curtain area) between inlet and seat which is used to calculate the theoretical flow c
48、apacity, with no deduction for any obstruction NOTEThe symbol is A. 3.5 flow diameter diameter corresponding to the flow area 3.6 discharge capacity 3.6.1 theoretical discharge capacity calculated capacity expressed in mass or volumetric units of a theoretically perfect nozzle having a cross-section
49、al flow area equal to the flow area of a safety valve 3.6.2 coefficient of discharge value of actual flowing capacity (from tests) divided by the theoretical flowing capacity (from calculation) 3.6.3 certified (discharge) capacity that portion of the measured capacity permitted to be used as a basis for the application of a safety valve NOTEIt may, for example, equal the : a) measured capacity times the derating factor ; or b) theoretical capacity times the coefficient of discharge times the dera