1、CEN EN*2b748 93 I 3404589 0039754 7 EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 26948 : 1991 October 1991 UDC 621.646.9.057.6 : 621.186.6 : 6 : 620.1 Descriptors: Valves and fittings, traps : dixinage, water vapour, steam, automatic equipment, tests, performance tests, performance evaluatio
2、n English version Automatic steam traps - Production and performance characteristic tests (IS0 6948 : 1980) Purgeurs automatiques de vapeur deau - Essais de production et essais des caractristiques de fonctionnement (IS0 6948 : 1980) Kondensatableiter - Fertigungsprfung und Prfung der Funktionsmerkm
3、ale (IS0 6948 : 1980) This European Standard was approved by CEN on 30 September 1991 and is identical to the IS0 standard as referred to. CEN members are bound to comply with the CENKENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a nationa
4、l 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 official versions (English, French, German). A version in any o
5、ther 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, Belgium, Denmark, Finland, France, Germany, Greece, Iceland
6、, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CEN European Committee for StandarCiization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B- 1050 Brussels O CEN 1991 Copyright reserve
7、d to all CEN members Ref. No. EN 26948 : 1991 E CEN EN*Zb948 93 = 3404589 0039755 9 = Page 2 EN 26948 : 1991 Foreword On the proposal of the Technical Committee CEN/TC 69 Industrial Valves CEN BT decided by resolution C67/1990 to submit the Inteiriational Standard IS0 6948 : 1981 : Automatic steam t
8、raps - Production and performance characteiistic tests to Formal Vote. This European Standard EN 26948 was approved by CEN on 2 July 1991. According to the Common CENKENELEC Rules, the following countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland, Rance, Germa
9、ny, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CEN EN*2694B 91 W 3404589 O019756 O M Page 3 EN 26948 : 1991 Automatic steam traps - Production and performance characteristics tests 1 Scope and field of application This I
10、nternational Standard specifies tests applicable 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.
11、This International Standard specifies the tests to be performed relative to each one of these two categories and describes briefly the corresponding test methods. 2 References IS0 6552, Automatic steam traps - Terminology. IS0 6553, Automatic steam traps - Marking. IS0 6704, Automatic steam traps -
12、Classification. 3 Definitions 3.1 production tests : Those 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 perf
13、ormance characteristic tests : Those tests carried out to determine the operational Characteristics of a particular design of steam trap. 4 Production testa 4.1 Product inspection Samples of the finished traps shall be visually examined and dimensionally checked to ensure that the traps correspond t
14、o the stated specification and are marked in accordance with IS0 6553. 4.2 Shell testing Each steam trap shall be tested to confirm the integrity of its shell under pressure. Further details are given in 6.1. 4.3 Operational check Sample steam traps shall be tested to ensure that they open to discha
15、rge condensate and close satisfactorily. Further details are given in 6.2. This test does not apply to the labyrinth (or orifice) steam traps (see IS0 6704). 4.4 Notice for acceptance tests If the purchaser wishes to witness the tests, this shall be specified in the order. The manufacturer shall giv
16、e the purchaser at least five days notice of the date when the 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
17、of the derivation of each characteristic is given below; further details on the appropriate test methods are specified in clause 6. 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.
18、5.2 Maximum operating pressure (PMO) The steam trap shall be tested 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 w
19、hich allows correct functioning. 5.4 Air venting capability The steam trap shall be tested to determine its ability to discharge air. CEN EN*Zb948 Page 4 EN 26948 : 1991 5.5 Operating temperature (TO) The steam trap shall be tested to determine the temperature at which the device operates and in par
20、ticular the temperature at which it passes its specified capacity. 5.6 Condensate capacity (OH or OC) 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 s
21、team lost via the trap. 6 Test methods 6.1 Shelf testing The test fluid, 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 iiquid having a viscosity not greater than that of water: - s
22、team, air or any other suitable gas. NOTE - Various statutory authorities require specific approval of test procedures where the test is conducted usins steam, air or other gas. Any inrernal trim which will not withstand the test pressure may be removed before the test. The trap shall be essentially
23、 vented of air when testing with a liquid. Traps shall not be painted or otherwise coated with materials capable of sealing against leakage before the shell pressure !ests are completed. Chemical corrosion protection treatments and internal linings are permitted. If pressure tests in the presence of
24、 a representative of the purchaser are specified, painted traps from stock may be 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
25、assembled trap with the ends closed. For all traps, the hydraulic shell test shall be performed at a pressure 1,5 times the maximum allowable pressure at 20 OC. For traps with a nominal diameter less than or equal to DN 50 in the pressure range up to PN 50, the shell test may be carried out either u
26、sing liquid at a pressure equal to 1,5 times the maximum allowable pressure at 20 C or using gas at a pressure (gauge pressure) of 6 bar (0.6 Mpa). Visually detectable leakage through the pressure retaining walls is not acceptable. Test durations shall not be less than those specified in the table.
27、Table - Minimum durations for shell tests Nominal trap size Minimum test duration 65 DN 200 250 DN 180 6.2 Operational check The steam trap shall be fed with steam, and condensate shall be introduced intermittently. When only steam is present, the steam trap shall close; on the introduction of conde
28、nsate, 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 shall 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
29、 6.3 Determination of minimum operating pressure Operational checks, as described in 6.2, shall be carried out whilst successively reducing the test pressure until the steam trap fails to open and close correctly. The minimum operating pressure is the lowest lest pressure at which correct operation
30、is observed. 6.4 Determination of maximum operating pressure The maximum operating pressure of the steam trap may be verified by carrying out operational checks, as described in 6.2, whilst successively increasing the test pressure up to the steam traps maximum operating pressure. The steam trap sha
31、ll open and close correctly throughout the test. 6.5 Determination of maximum operating back pressure Operational checks, as described in 6.2, shall be carried 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
32、 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 trap fails to open and close correctly. The maximum operating back pressure is the highest pressure applied to the steam traps outlet at which
33、 correct operation is still observed. CEN EN*Zb4 - 8 3 4 O458 9- 0019758 - 4 6.6 Air venting 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
34、operating pressures, the temperature inside the trap being recorded. 6.7 Determination of operating temperature Steam shall be fed into the steam trap to effect closure. Con- densate, at saturated steam temperature, shall then be in- troduced and, unless the steam trap opens immediately, shall be al
35、lowed to cool slowly at the steam traps inlet. The temperature of the condensate, measured at the steam traps inlet, at which the device opens, is the operating temperature. The operating temperatures are the temperatures of the con- densate, measured at the inlet to the trap, at which the trap pass
36、es its specified capacities. Page 5 EN 26948: 1991 6.8 Condensate capacity test The capacity of the steam trap shall be determined by measur- ing the amount of condensate that is discharged from the device under specified conditions of pressure differential and condensate temperature. The test shall
37、 be carried out with condensate at different temperatures and at different pressures within the steam traps operating 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.
