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1、BRITISH STANDARD BS 1123-1: 1987 Safety valves, gauges and fusible plugs for compressed air or inert gas installations Part 1: Code of practice for installation UDC 621.51/.54:531.787+536.522.2+621.646.28 Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 06:11:08 GMT+00:00 2006, Uncontrolled Co
2、py, (c) BSI BS 1123-1:1987 This British Standard, having been prepared under the direction of the Pressure Vessel Standards Committee, was published under the authority of the Board of BSI and comes into effect on 27 February 1987 BSI 02-1999 First published July 1943 First revision February 1950 Se
3、cond revision July 1961 Third revision October 1976 Fourth revision, as Part 1, February 1987 The following BSI references relate to the work on this standard: Committee reference PVE/12 Draft for comment 85/71476 DC ISBN 0 580 15682 6 Committees responsible for this British Standard The preparation
4、 of this British Standard was entrusted by the Pressure Vessel Standards Committee (PVE/-) to Technical Committee PVE/12, upon which the following bodies were represented: Associated Offices Technical Committee Association of Shell Boilermakers British Compressed Air Society British Compressed Gases
5、 Association British Valve Manufacturers Association Ltd Combustion Engineering Association Electricity Supply Industry in England and Wales Energy Industries Council Engineering Equipment and Materials Users Association GAMBICA (BEAMA Ltd) Health and Safety Executive Institution of Mechanical Engin
6、eers Lloyds Register of Shipping Spring Research and Manufacturers Association Transmission and Distribution Association (BEAMA Ltd) Water Tube Boilermakers Association The following body was also represented in the drafting of the standard, through subcommittees and panels: Liquefied Petroleum Gas
7、Industry Technical Association (UK) Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 06:11:08 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 1123-1:1987 BSI 02-1999i Contents Page Committees responsibleInside front cover Foreword
8、ii Section 1. General 1Scope1 2Definitions1 Section 2. Fittings excluding safety valves 3Pressure gauges2 4Fusible plugs2 Section 3. Installation and maintenance of safety valves 5General recommendations3 6Set pressure3 7Mountings3 8Discharge pipework3 9Easing gear3 10Maintenance3 Section 4. Useful
9、information on safety valves complying with BS 6759-2 11Certified discharge capacity4 12Tolerances4 Publications referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 06:11:08 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 1123-1:1987 ii BSI 02-1999 Foreword This Part of
10、 BS 1123 has been prepared under the direction of the Pressure Vessel Standards Committee and is a revision of BS 1123:1976. The decision to align the requirements of safety valves with those of ISO 4126 “Safety valves, general requirements”, published by the International Organization for Standardi
11、zation, has resulted in a change of format of this revision compared with that adopted for the 1976 edition. This Part of BS 1123 is a code of practice which complements BS 6759-2. It deals with the installation of safety valves, pressure gauges and fusible plugs. Part 2 of BS 1123 has been created
12、by amendment to the requirements of the 1976 edition of BS 1123; it retains details for safety valves only. BS 1123-2 is declared obsolescent and will be withdrawn in December 1987. Its retention is to give manufacturers a period of grace in which to align their products with BS 6759-2. A British St
13、andard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cove
14、r, an inside front cover, pages i and ii, pages 1 to 4, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun
15、, na, Fri Nov 24 06:11:08 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 1123-1:1987 BSI 02-19991 Section 1. General 1 Scope This code of practice recommends good practice for the installation of safety valves, pressure gauges and fusible plugs used with air receivers and compressed air or inert gas
16、installations. It refers to safety valves in accordance with BS 6759-2 and BS 1123-2. NOTEThe titles of the standards publications referred to in this code are listed on the inside back cover. 2 Definitions For the purposes of this code the following definitions apply. 2.1 blowdown of a safety valve
17、 the difference between the set pressure and the re-seating pressure, normally stated as a percentage of set pressure except for very low set pressure when the blowdown is then expressed in bar 2.2 certified discharge capacity that portion of the measured capacity permitted to be used as a basis for
18、 the application of a safety valve NOTEThe certified discharge capacity is derived from one of the following: a) measured flow rate derating factor; b) theoretical flow rate coefficient of discharge derating factor; c) theoretical flow rate derated coefficient of discharge. 2.3 commencement of lift
19、initial lift such as would cause the first indication of movement on a linear transducer or equivalent NOTEProvision of such instrument facility only applies to valves under operating characteristics tests. 2.4 direct loaded safety valve a safety valve in which the loading due to the fluid pressure
20、underneath the valve disk is opposed only by direct mechanical loading such as a weight, a lever and weight or a spring 2.5 fusible plug a device containing material which melts at a predetermined temperature 2.6 gauge an indicating device, e.g. for pressure 2.7 overpressure of a safety valve a pres
21、sure increase above the set pressure of a safety valve, usually expressed as a percentage of set pressure 2.8 safety valve a valve that automatically, without the assistance of any energy other than that of the fluid concerned, discharges a certified quantity of the fluid so as to prevent a predeter
22、mined safe pressure being exceeded, and that is designed to reclose and prevent further flow of fluid after normal pressure conditions of service have been restored 2.9 set pressure the predetermined pressure at which a safety valve under operating conditions should commence to lift. It is the gauge
23、 pressure measured at the valve inlet at which the pressure forces tending to open the valve for the specified service conditions are in equilibrium with the forces retaining the valve disk on its seat Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 06:11:08 GMT+00:00 2006, Uncontrolled Copy,
24、 (c) BSI BS 1123-1:1987 2 BSI 02-1999 Section 2. Fittings excluding safety valves 3 Pressure gauges 3.1 General Pressure gauges should be in accordance with BS 1780 for industrial gauges. 3.2 Selection and installation of a pressure gauge For the selection and installation of pressure gauges the gui
25、dance, recommendations and precautions contained in BS 1780 should be followed. NOTEIt is recommended that all pressurized systems be fitted with a pressure indicating device. Attention is drawn to statutory requirements relating to the fitting of pressure indicating devices. 4 Fusible plugs 4.1 Gen
26、eral A fusible plug consists of a holder with a central passage closed by fusible metal. The outlet should be provided with a diffuser cap capable of arresting and containing the ejected metal. The holder inlet connection should be threaded not less than R3/8 (see BS 21). A fusible plug may be fitte
27、d adjacent to each compressor to help to safeguard the installation and/or provide audible indication of excessively high temperature in the installation. Such fusible plugs should be fitted between the compressor and the after-cooler (if any), or between the compressor and the receiver. They should
28、 be fitted as close to the compressor outlet as practicable. All fusible plugs should be situated so that the discharge from the plug will not cause injury to any persons. 4.2 Material The non-fusible portions of the plug should be of copper alloy. The fusible metal should be chosen to have a meltin
29、g point to suit the application. 4.3 Marking An indication of the melting temperature should be permanently marked on the fusible plug. Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 06:11:08 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 1123-1:1987 BSI 02-19993 Section 3. Installation and m
30、aintenance of safety valves 5 General recommendations NOTEAttention is drawn to statutory requirements relating to the fitting of safety valves. Safety valves should be in accordance with BS 6759-2 or BS 1123-2, as appropriate. Safety valves of the direct loaded spring operated type are preferred. T
31、he total capacity of the safety valve or valves fitted to any receiver or system of receivers should be sufficient to discharge the maximum quantity of fluid that can be generated or supplied, thus preventing the pressure exceeding that permitted by the application standard. Receivers connected toge
32、ther in a system by piping of adequate capacity, which does not contain any valve that can isolate any receiver, may be considered as a system of receivers for the application of pressure relief. Consideration should be given to the possibility of fire. It may be necessary to accommodate any extra d
33、ischarge and to make arrangements to reduce the pressure to allow for reduced strength of the system at elevated temperature. To prevent undesirable operation of the safety valve, there should be a margin between the maximum operating pressure of the system and the lowest pressure at which the safet
34、y valve(s) is set to lift. A suitable margin is 10 % of the working pressure or 0.6 bar, whichever is the greater. 6 Set pressure The installer should ensure that the safety valve is that specified for the application, that it is marked with the correct set pressure and that the device protecting th
35、e set pressure adjustment is intact. If the set pressure of a safety valve is changed, the new set pressure should be marked on the valve and the original marking deleted. The device protecting the set pressure adjustment should be replaced. The permitted range of adjustment should be in accordance
36、with the manufacturers recommendations. 7 Mountings Safety valves should be mounted directly on connections used for no other purpose, except for connections that do not interfere with the proper functioning of the safety valve, e.g. pressure gauges or thermocouples. The cross- sectional area of eac
37、h connection should be at least equal to the bore of the inlet of the safety valve or, where two or more safety valves are mounted on the same connection, at least equal to the sum of the areas of the bores of all the valve inlets. Where direct mounting is not practical, a length of connecting pipin
38、g may be used but in no case should the pressure-drop between the safety valve and the receiver it protects exceed 3 % of the set pressure of the safety valve. The safety valve(s) should be mounted with the spindle in the vertically upward position. If it is desired to mount the valve in any other p
39、osition, the requirement should be agreed with the manufacturer. 8 Discharge pipework Any discharge piping from safety valves should be as short as possible and should have a bore at least equal to the bore of the safety valve outlet. Discharge piping should be adequately supported and arranged so t
40、hat the discharge does not cause injury or damage. The purchaser should inform the safety valve manufacturer of any imposed back pressure on the discharge side of the valve. The manufacturer should confirm the suitability of the valve for the back pressure specified and provide the capacity correcti
41、on factor to be applied when appropriate. 9 Easing gear Safety valves should be arranged such that when they are under a pressure of not less than 75 % of the set pressure, the mechanical load on the valve disk can be eased by means of suitable gear. The omission of easing gear is sometimes permissi
42、ble by arrangement with the appropriate authority. 10 Maintenance To ensure satisfactory performance, safety valves should be regularly serviced and maintained in accordance with the manufacturers instructions. Attention is drawn to the fact that particular applications may result in the build up of
43、 deposits which could affect the operation of the valve. Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 06:11:08 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 1123-1:1987 4 BSI 02-1999 Section 4. Useful information on safety valves complying with BS 6759-2 11 Certified discharge capacity Saf
44、ety valves achieve their certified discharge capacity at an overpressure not exceeding the greater of 0.3 bar or 10 % of set pressure. 12 Tolerances 12.1 Set pressure The permitted tolerances on set pressure are: 12.2 Blowdown 12.2.1 The permitted tolerance on blowdown for valves with adjustable blo
45、wdown is: a) minimum: 2.5 % of set pressure; b) maximum: 7 % of set pressure except for safety valves having: 1) flow diameter less than 15 mm, when the maximum limit is 10 % of set pressure; 2) values of set pressure less than 3 bar when the maximum limit is 0.3 bar. 12.2.2 The permitted tolerance
46、on blowdown for valves with non-adjustable blowdown is: maximum: 10 % of set pressure or 0.3 bar, whichever is the greater. (a) for set pressure below 5 bar: 0.14 bar; (b) for 5 bar up to 20 bar: 3 %; (c) for 20 bar up to 100 bar: 2 %; (d) for 100 bar and above: 1.5 %. Licensed Copy: sheffieldun she
47、ffieldun, na, Fri Nov 24 06:11:08 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 1123-1:1987 BSI 02-1999 Publications referred to BS 21, Specification for pipe threads for tubes and fittings where pressure-tight joints are made on the threads (metric dimensions). BS 1123, Safety valves, gauges and fu
48、sible plugs for compressed air or inert gas installations. BS 1123-2, Specification for safety valves (obsolescent). BS 1780, Specification for bourdon tube pressure and vacuum gauges. BS 6759, Safety valves. BS 6759-2, Specification for safety valves for compressed air or inert gases. ISO 4126, Saf
49、ety valves, general requirements1). 1) Referred to in the foreword only. Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 06:11:08 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BSI 389 Chiswick High Road London W4 4AL | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BSI British Standards Institution BSI is the independent national body responsible for pr