1、BRITISH STANDARD BS EN 27841:1991 ISO 7841:1988 Methods for Determination of steam loss of automatic steam traps The European Standard EN 27841:1991 has the status of a British StandardBSEN27841:1991 This British Standard was published under the authority ofthe Standards Board and comesinto effect o
2、n 29 November 1991 BSI 11-1999 The following BSI references relate to the work on this standard: Committee reference PSE/7 Draft for comment 85/73145 DC ISBN 0 580 20221 6 Cooperating organizations The European Committee for Standardization (CEN), under whose supervision this European Standard was p
3、repared, 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 normalisation Germany Deu
4、tsches 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 Netherlands Nederlands Normalisatie-
5、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 Institution Amendments issued
6、 since publication Amd. No. Date CommentsBSEN27841:1991 BSI 11-1999 i Contents Page Cooperating organizations Inside front cover National foreword ii Foreword 2 Text of EN 27841 3 National appendix NA (informative) Inside back cover National appendix NB (informative) Inside back coverBSEN27841:1991
7、ii BSI 11-1999 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 EN 27841:1991 “Automatic steam traps Determination of steam loss Test methods” published by the European Com
8、mittee for Standardization (CEN). It supersedes BS 6027:1990 which is withdrawn. EN 27841:1991 is identical with ISO 7841:1988 published by the International Organization for Standardization (ISO). A British Standard does not purport to include all the necessary provisions of a contract. Users of Br
9、itish 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 front cover, pages i and ii, theEN title page, pages 2 to 14, an inside back
10、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 EUROPISCHE NORM EN 27841:1991 October 1991 UDC 621.646.9.057:621.186.1:620.1
11、 Descriptors: Industrial valves, traps: drainage, water vapour, steam, tests, measurements, head losses English version Automatic steam traps Determination of steam loss Test methods (ISO 7841:1988) Purgeurs automatiques de vapeur d eau Dtermination de la perte de vapeur Mthodes d essai (ISO 7841:19
12、88) Kondensatableiter Bestimmung des Dampfverlustes Prfverfahren (ISO 7841:1988) This European Standard was approved by CEN on 30 September 1991 and is identical to the ISO standard as referred to. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditio
13、ns for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member. This European Standard exists in three off
14、icial 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 notified to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria,
15、 Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CEN European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de
16、 Stassart 36, B-1050 Brussels CEN 1991 Copyright reserved to all CEN members Ref. No. EN 27841:1991 EEN27841:1991 BSI 11-1999 2 Foreword On the proposal of the Technical Committee CEN/TC69 “Industrial Valves” CEN BT has decided by resolution C67/1990 to submit the International Standard. ISO 7841:19
17、88: Automatic steam traps Determination of steam loss Test methods to Formal Vote. This European Standard was adopted by CEN on 5 August 1991. According to the Common CEN/CENELEC Rules, the following countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland, France,
18、 Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. Endorsement The text of the International Standard ISO7481:1988 was approved by CEN as a European Standard without any modifications. Contents Page Foreword 2 1 Scope
19、and field of application 3 2 References 3 3 Test arrangements 3 4 Test method A 3 5 Test method B 8 6 Bibliography 13 Figure 1 Test arrangement for steam loss tests with test method A 4 Figure 2 Test arrangement for steam loss tests with test method B 9EN27841:1991 BSI 11-1999 3 1 Scope and field of
20、 application This International Standard specifies two test methods to determine the steam loss of automatic steam traps to ISO6552. The object of these tests is to determine the amount of live steam, if any, that is lost through the steam trap. They are, therefore, tests to evaluate the ability of
21、the traps to shut against steam during successive operations. There is no measurement of the total heat energy lost by the trap. Such total heat loss would include radiation and convection components which can be established separately. 2 References ISO 651, Solid-stem calorimeter thermometers. ISO
22、652, Enclosed-scale calorimeter thermometers. ISO 653, Long solid-stem thermometers for precision use. ISO 4185, Measurement of liquid flow in closed conduits Weighing method. ISO 6552, Automatic steam traps Definition of technical terms. 3 Test arrangements The test arrangements for steam loss dete
23、rmination are shown inFigure 1 andFigure 2. The minimum water capacity of the calorimeter tank (seeFigure 1) shall be 0,02m 3 . It is most important that the condensate drainage device be fully capable of maintaining a dry line to the heat exchanger. The test device shall be located sufficiently bel
24、ow the heat exchanger to prevent condensate backing up into the heat exchanger, should the test device only operate infrequently. All piping and equipment (including the heat exchanger) shall be insulated to a value of to reduce thermal losses to a minimum. The instruments used for the measurements
25、shall comply with International Standards, if such standards exist, e.g. ISO651, ISO652, ISO653 for temperature measurements; ISO4185 for flow measurements. The condensate removal device shall not be modified in any way from its commercial form. 4 Test method AEN 27841:1991 4 BSI 11-1999 1)Operating
26、 at steam temperature. Figure 1 Test arrangement for steam loss tests with test method AEN27841:1991 BSI 11-1999 5 The test may be carried out at a pressure corresponding to the maximum working pressure of the trap, the test pressure not exceeding 32 bar 1)with saturated steam (238 C). Load testing
27、shall be carried out at1% of the maximum capacity of the trap at the corresponding test pressure with a minimum of 5kg/h. 4.1 Procedure 4.1.1 No-load condition Start with all valves closed and tanks empty. 4.1.1.1 Open valves 1, 2 and 3 to permit the drain and test devices to operate at test pressur
28、e p s . 4.1.1.2 During warm-up, weigh and record the mass of the empty calorimeter tank m t,and record the steam pressure p sand steam temperature s . 4.1.1.3 Fill the calorimeter tank with sufficient water (about half-full) to result in a test run of practical duration. The initial water temperatur
29、e 1should be at least 8 C below ambient temperature a . Record the water temperature 1and mass of water plus tank m 1 . 4.1.1.4 When thermal equilibrium is reached, simultaneously and rapidly close valve 3, open valve 4, and start the timing interval. The use of a three-way valve is recommended to f
30、acilitate rapid closing and opening. 4.1.1.5 Stir the water in the tank as necessary to ensure a uniform water temperature. 4.1.1.6 When the temperature of the water in the tank is as many degrees above ambient as the initial temperature was below, rapidly close valve 4 and open valve 3 simultaneous
31、ly, record the elapsed time, the final water temperature 2and the mass of water plus tank m 2 . 4.1.1.7 Before the measurement, trial runs should be carried out to ensure that the test conditions have stabilized and that the pressure, temperature, initial amount of water in the calorimeter tank and
32、load conditions are those required. When testing condensate removal devices, an error calculation is made from three consecutive tests to determine the accuracy of the test result. The error calculation is based on the instrumentation used and described in this International Standard; or the average
33、 result from three consecutive tests shall agree within 10% or 500g/h, whichever is the greater. If this cannot be obtained, check the system for integrity and increase the calorimeter tank capacity. 4.1.2 Load condition Start with all valves closed and both tanks empty. 4.1.2.1 Open valves 1, 2 and
34、 3 to permit the drain and test devices to operate at test pressure p s . 4.1.2.2 During warm-up, weigh and record the mass of the empty calorimeter tank m t , and record the steam pressure p sand steam temperature s . 4.1.2.3 Open valves 5 and 6 to allow a flow of cooling water through the heat exc
35、hanger, to create the desired condensate load on the test device. After the system has come to equilibrium, this load. can be determined by closing valve 6 and opening valve 7, to permit a known amount of water to be collected in a given time. Record the temperature of water entering and leaving the
36、 heat exchanger, Eand L , the initial and final mass of exchanger water plus tank, m 3and m 4 , and the time %t, in seconds, of run on the Data Sheet in4.3. The approximate condensate load, in kilograms per hour, on the trap may then be calculated using the formula where h fgsis the specific enthalp
37、y of the evaporation at steam inlet conditions, in joules per kilogram. 4.1.2.4 If the load on the trap as determined in4.1.2.3 is as desired, proceed to4.1.2.5. If it is not as desired, adjust valve 5 accordingly and repeat the procedure in4.1.2.3 until the desired load is obtained. 1) 1 bar = 10 5
38、PaEN27841:1991 6 BSI 11-1999 4.1.2.5 Fill the calorimeter tank with sufficient water (about half-full) to result in a test run of practical duration. The initial water temperature 1should be at least 8 C below ambient temperature a . Record the water temperature 1and mass of water plus tank m 1 . 4.
39、1.2.6 When thermal equilibrium is reached, simultaneously and rapidly close valve 3, and open valve 4, and start the timing interval. The use of a three-way valve is recommended to facilitate rapid closing and opening. 4.1.2.7 Stir the water in the calorimeter tank as necessary to ensure a uniform w
40、ater temperature. 4.1.2.8 When the temperature of the water in the calorimeter tank is as many degrees above ambient as the initial temperature was below, rapidly close valve 4 and open valve 3 simultaneously, record the elapsed time, the final water temperature 2and the mass of water plus tank m 2
41、. 4.1.2.9 Before the measurement, trial runs should be carried out to ensure that the test conditions have stabilized and that the pressure, temperature, initial amount of water in the calorimeter tank and load conditions are those required. When testing condensate removal devices, an error calculat
42、ion is made from three consecutive tests to determine the accuracy of the test result. The error calculation is based on the instrumentation used and described in this International Standard; or the average result from three consecutive tests shall agree within 10% or 500g/h, whichever is the greate
43、r. If this cannot be obtained, check the system for integrity and increase the calorimeter tank capacity. 4.2 Expression of results 4.2.1 Correction of measured variables The values of observed variables shall be corrected in accordance with instrument calibrations and, if necessary, converted to th
44、e proper units required for calculations. 4.2.2 Use of formula symbols The symbols used in this International Standard are the ones normally associated with engineering practice in this field. In a few cases, the same symbol has different meanings in different parts of this International Standard ac
45、cording to its application. In order to avoid confusion, each formula has been provided with its own list of definitions of symbols and units. 4.2.3 Computation formula where q ms is the steam loss, in kilograms per hour; m i is the initial mass of water in the calorimeter, in kilograms; m f is the
46、final mass of water and condensate in the calorimeter, in kilograms; m 1 is the mass of calorimeter plus water, at the start, in kilograms; m 2 is the mass of calorimeter plus water, at the finish, in kilograms; m t is the mass of calorimeter tank, in kilograms; h f1 is the initial specific enthalpy
47、 of water in the calorimeter, in joules per kilogram; h f2 is the final specific enthalpy of the condensate and water in the calorimeter, in joules per kilogram; h fs is the specific enthalpy of the liquid at steam inlet conditions, in joules per kilogram; h fgs is the specific enthalpy of the evapo
48、ration at steam inlet conditions, in joules per kilogram; c p is the specific heat of the calorimeter material, in joules per kilogram kelvin; 1 is the initial water temperature in the calorimeter tank, in degrees Celsius; 2 is the water temperature in the calorimeter tank, in degrees Celsius; %t is
49、 the time interval, in seconds.EN27841:1991 BSI 11-1999 7 4.3 Data sheetEN27841:1991 8 BSI 11-1999 5 Test method BEN 27841:1991 BSI 11-1999 9 1)The separating tank should be kept hot by a heated jacket or an insulating system. 2)Operating at steam temperature. Figure 2 Test arrangement for stream loss tests with test method BEN27841:1991 10 BSI 11-1999 The test may be carried out at a pressure corresponding to the maximum working pressure of the trap, the test pressure not exceeding
