1、BRITISH STANDARD BS EN 26948:1991 ISO 6948:1981 Specification for Production and performance characteristic tests for automatic steam traps The European Standard EN 26948:1991 has the status of a British StandardBSEN26948:1991 This British Standard was published under the authorityofthe Standards Bo
2、ardand comes into effect on 29 November 1991 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference PSE/7 Draft for comment 79/80385 DC ISBN 0 580 20220 8 Cooperating organizations The European Committee for Standardization (CEN), under whose supervision th
3、is European Standard was prepared, comprises the national standards organizations of the following countries. Austria Oesterreichisches Normungsinstitut Belgium Institut belge de normalisation Denmark Dansk Standardiseringsraad Finland Suomen Standardisoimisliito, r.y. France Association franaise de
4、 normalisation Germany Deutsches Institut fr Normung e.V. Greece Hellenic Organization for Standardization Iceland Technological Institute of Iceland Ireland National Standards Authority of Ireland Italy Ente Nazionale Italiano di Unificazione Luxembourg Inspection du Travail et des Mines Netherland
5、s Nederlands Normalisatie-instituut Norway Norges Standardiseringsforbund Portugal Instituto Portugus da Qualidade Spain Asociacin Espaola de Normalizacin y Certificacin Sweden Standardiseringskommissionen i Sverige Switzerland Association suisse de normalisation United Kingdom British Standards Ins
6、titution Amendments issued since publication Amd. No. Date CommentsBSEN26948:1991 BSI 10-1999 i Contents Page Cooperating organizations Inside front cover National foreword ii Foreword 2 Text of EN 26948 3 National appendix NA (informative) Inside back cover National appendix NB (informative) Inside
7、 back coverBSEN26948:1991 ii BSI 10-1999 National foreword This British Standard has been prepared under the direction of the Piping Systems Components Standards Policy Committee. It is the English language version of EN26948:1991 “Automatic steam traps Production and performance characteristic test
8、s” published by the European Committee for Standardization (CEN). It supersedes BS6025:1982 which is withdrawn. EN26948:1991 is identical with ISO6948:1981 published by the International Organization for Standardization (ISO). A textual error exists in ISO6948 and in EN26948. This error has been rep
9、orted to the Central Secretariat of CEN and the following amendment has been proposed. In6.7 delete paragraph2and insert the following at the end of the clause. “The determination shall be carried out at different pressures within the operating range of the steam trap.” A British Standard does not p
10、urport 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 cover, an inside fron
11、t cover, pages i and ii, theEN title page, pages 2 to 6, 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.EUROPEAN STANDARD NORME EUROPENNE EURO
12、PISCHE NORM EN 26948:1991 October 1991 UDC 621.646.9.057.6:621.186.6:6:620.1 Descriptors: Valves and fittings, traps: drainage, water vapour, steam, automatic equipment, tests, performance tests, performance evaluation English version Automatic steam traps Production and performance characteristic t
13、ests (ISO 6948:1980) Purgeurs automatiques de vapeur deau Essais de production et essais des caractristiques de fonctionnement (ISO6948:1980) Kondensatableiter Fertigungsprfung und Prfung der Funktionsmerkmale (ISO6948:1980) This European Standard was approved by CEN on30September1991and is identica
14、l to the ISO standard as referred to. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such n
15、ational standards may be obtained on application to the Central Secretariat or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and
16、 notified to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United K
17、ingdom. CEN European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels CEN 1991 Copyright reserved to all CEN members Ref. No. EN 26948:1991 EEN26948:1991 BSI 10-1999 2 Foreword On the proposal of the
18、Technical Committee CEN/TC69 “Industrial Valves” CEN BT decided by resolution C67/1990 to submit the International Standard ISO 6948:1981: Automatic steam traps Production and performance characteristic tests to Formal Vote. This European Standard EN26948 was approved by CEN on2July1991. According t
19、o the Common CEN/CENELEC Rules, the following countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. Contents Page Forewor
20、d 2 1 Scope and field of application 3 2 References 3 3 Definitions 3 4 Production tests 3 5 Performance characteristic tests 3 6 Test methods 4 Table Minimum durations for shell tests 4EN26948:1991 BSI 10-1999 3 1 Scope and field of application This International Standard specifies tests applicable
21、 to automatic steam traps. These tests, which are hereafter referred to as production tests and performance characteristic tests, may be conducted to ensure the correct functioning of a steam trap or to evaluate the performance of a particular design. This International Standard specifies the tests
22、to be performed relative to each one of these two categories and describes briefly the corresponding test methods. 2 References ISO 6552, Automatic steam traps Terminology. ISO 6553, Automatic steam traps Marking. ISO 6704, Automatic steam traps Classification. 3 Definitions 3.1 production tests tho
23、se tests carried out by the manufacturer to confirm that each automatic steam trap functions correctly. These tests may be witnessed by the purchaser or his representative; in this case, these tests are referred to as acceptance tests 3.2 performance characteristic tests those tests carried out to d
24、etermine the operational characteristics of a particular design of steam trap 4 Production tests 4.1 Product inspection Samples of the finished traps shall be visually examined and dimensionally checked to ensure that the traps correspond to the stated specification and are marked in accordance with
25、 ISO6553. 4.2 Shell testing Each steam trap shall be tested to confirm the integrity of its shell under pressure. Further details are given in6.1. 4.3 Operational check Sample steam traps shall be tested to ensure that they open to discharge condensate and close satisfactorily. Further details are g
26、iven in6.2. This test does not apply to the labyrinth (or orifice) steam traps (seeISO6704). 4.4 Notice for acceptance tests If the purchaser wishes to witness the tests, this shall be specified in the order. If the manufacturer shall give the purchaser at least five days notice of the date when the
27、 tests will be performed. 5 Performance characteristic tests A manufacturer may describe the operations of a particular type of steam trap by referring to one or more of the following performance characteristic tests. A brief explanation of the derivation of each characteristic is given below; furth
28、er details on the appropriate test methods are specified in clause6. 5.1 Minimum operating pressure The steam trap shall be tested to determine the minimum pressure (atmospheric or above) at which correct opening and closing will occur. 5.2 Maximum operating pressure (PMO) The steam trap shall be te
29、sted to determine the maximum pressure at which correct opening and closing will occur. 5.3 Maximum operating back pressure (PMOB) The steam trap shall be tested to determine the maximum pressure permissible at the outlet of the device which allows correct functioning. 5.4 Air venting capability The
30、 steam trap shall be tested to determine its ability to discharge air. 5.5 Operating temperature (TO) The steam trap shall be tested to determine the temperature at which the device operates and in particular the temperature at which it passes its specified capacity. 5.6 Condensate capacity (QH or Q
31、C) The steam trap shall be flow tested to determine its condensate capacity throughout its operating pressure range. 5.7 Live steam loss The steam trap shall be tested to determine the amount of live steam lost via the trap.EN26948:1991 4 BSI 10-1999 6 Test methods 6.1 Shell testing The test fluid,
32、the choice of which is left to the discretion of the manufacturer, shall be either: water, which may contain a corrosion inhibitor, kerosene or any other suitable liquid having a viscosity not greater than that of water; steam, air or any other suitable gas. NOTEVarious statutory authorities require
33、 specific approval of test procedures where the test is conducted using steam, air or other gas. Any internal trim which will not withstand the test pressure may be removed before the test. The trap shall be essentially vented of air when testing with a liquid. Traps shall not be painted or otherwis
34、e coated with materials capable of sealing against leakage before the shell pressure tests are completed. Chemical corrosion protection treatments and internal linings are permitted. If pressure tests in the presence of a representative of the purchaser are specified, painted traps from stock may be
35、 re-tested without removal of paint. Test equipment shall not subject the trap to externally applied stresses which may affect the results of the tests. The shell test shall be performed by applying pressure inside the assembled trap with the ends closed. For all traps, the hydraulic shell test shal
36、l be performed at a pressure1,5times the maximum allowable pressure at20 C. For traps with a nominal diameter less than or equal to DN50in the pressure range up to PN50, the shell test may be carried out either using liquid at a pressure equal to1,5times the maximum allowable pressure at20 C or usin
37、g gas at a pressure (gauge pressure) of6bar (0,6Mpa). Visually detectable leakage through the pressure retaining walls is not acceptable. Test durations shall not be less than those specified in the Table. Table Minimum durations for shell tests 6.2 Operational check The steam trap shall be fed with
38、 steam, and condensate shall be introduced intermittently. When only steam is present, the steam trap shall close; on the introduction of condensate, the steam trap shall open (the time taken will vary as a function of the steam trap type); when the condensate has been discharged, the steam trap sha
39、ll again close. The test is complete when at least one complete cycle has been performed. Certain types of trap may be tested with air or water. 6.3 Determination of minimum operating pressure Operational checks, as described in6.2, shall be carried out whilst successively reducing the test pressure
40、 until the steam trap fails to open and close correctly. The minimum operating pressure is the lowest test pressure at which correct operation is observed. 6.4 Determination of maximum operating pressure The maximum operating pressure of the steam trap may be verified by carrying out operational che
41、cks, as described in6.2, whilst successively increasing the test pressure up to the steam traps maximum operating pressure. The steam trap shall open and close correctly throughout the test. 6.5 Determination of maximum operating back pressure Operational checks, as described in6.2, shall be carried
42、 out with the outlet from the steam trap connected to a vessel in which the pressure can be raised, independent of the test pressure upstream of the steam trap. Whilst maintaining a reference pressure at the steam traps inlet, the pressure at its outlet is to be raised successively until the steam t
43、rap fails to open and close correctly. The maximum operating back pressure is the highest pressure applied to the steam traps outlet at which correct operation is still observed. Nominal trap size DN Minimum test duration s DN u 50 15 65 u DN u 200 60 250 u DN 180EN26948:1991 BSI 10-1999 5 6.6 Air v
44、enting capability test Air shall be introduced at a specified temperature into the trap or upstream piping. The air venting capability shall be checked by an air flow measurement carried out at minimum and maximum operating pressures, the temperature inside the trap being recorded. 6.7 Determination
45、 of operating temperature Steam shall be fed into the steam trap to effect closure. Condensate, at saturated steam temperature, shall then be introduced and, unless the steam trap opens immediately, shall be allowed to cool slowly at the steam traps inlet. The temperature of the condensate, measured
46、 at the steam traps inlet, at which the device opens, is the operating temperature. The operating temperatures are the temperatures of the condensate, measured at the inlet to the trap, at which the trap passes its specified capacities. 6.8 Condensate capacity test The capacity of the steam trap sha
47、ll be determined by measuring the amount of condensate that is discharged from the device under specified conditions of pressure differential and condensate temperature. The test shall be carried out with condensate at different temperatures and at different pressures within the steam traps operatin
48、g range to be specified in a forthcoming International Standard. 6.9 Determination of live steam loss Several methods may be used to determine the amount of live steam lost, if any, by the steam trap in accordance with a forthcoming International Standard.6 blankBSEN26948:1991 BSI 10-1999 National a
49、ppendix NA (informative) The United Kingdom participation in the preparation of this European Standard was entrusted by the Piping Systems Components Standards Policy Committee (PSE/-) to Technical Committee PSE/7, upon which the following bodies were represented: Amalgamated Engineering Union Association of Bronze and Brass Founders Association of Building Component Manufacturers British Chemical Engineering Contractors Association British Foundry Association British Gas plc British Maritime Technology British Plumbing Fittin
