1、hilatiam1 fbmvwd This stand kan publishedj irr aecardanm with a dercisimi taken1 by CENYTC E9 t adopt, without alterationr Intm- nationaiEfamiardi ISQ 694 Armaturen (8Va4vw Sfarrdards Cmmittee). The MN Csdscorrespomdfimgto the: Internatiomal Stmdardsrefer classificatian Deszripto-rtx Val Fertigryngp
2、sprfung: umdd! Prfung, der FurjhktianamerKm0 mdi is identical to the CEN members are bao Spain! SwedLn! Switzerland and Wnitd Mimgdom. IS0 Stad sWi under prjlre. Further demils are given in 62 1. 4.4- Ndge for acceptance aSi mt grmm than: that afi water; - steam, ak-or any atkr suimblegirs The trap1
3、 shall be essmtially vented a- ain wtrem resting with a iiquid. Far all traps, the: ItNdraulici sM# tes* sbll b ped vinth- steam, and crorrdbnsata shall he irainodhced intermittently. Opercrtiirwrel checks, 8c ci%scrib Fertigungsprfung und Prfung der Funktionsmerkmale (IS0 6948 : 1981 ) European Sta
4、ndard EN 26 948 : 1991 has the status of a DIN Standard. A comma is used as the decimal marker: National foreword This standard has been published in accordance with a decision taken by CEN/TC 69 to adopt, without alteration, Inter- national Standard IS0 6948 (prepared by ISOTC 153) as a European St
5、andard. The responsible German body involved in the preparation of this standard was the Nofmenausschu Armaturen (Valves Standards Committee). The DIN Standards corresponding to the International Standards referred to in clause 2 of the EN are as follows: international Standard DIN Standard IS0 6553
6、 DIN IS0 6553 IS0 6704 DIN EN 26 704 Standard referred to (and not included in References) DIN EN 26 704 Automatic steam traps; classification International Patent Classification F 16 T 1 /O0 F 17 D 3/14 GO1 M3/00 G O1 N 17/00 EN comprises 5 pages. Beurb Verlag GmbH, Berlin, has the exclusive right
7、o sale for German Standards (DIN-Normen). DIN EN 26948 Engl. Price group 5 Sales No. 1105 06.93 EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 26948 September 1991 UDC 621.646.9.057.6 : 621.186.6 :620.1 Descriptors: Valves and fittings, traps, drainage, water vapour, steam, automatic equipment
8、, tests, performance tests, perfor- mance evaluation. English version Au tom at ic steam traps Production and performance characteristic tests (IS0 6948 : 1981) Purgeurs automatiques de vapeur deau; essais de production et essais des carac- tristiques de fonctionnement (IS0 6948 : 1981 ) Kondensatab
9、leiter; Fertigungsprfung und Prfung der Funktionsmerkmale (IS0 6948 : 1981) This European Standard was approved by CEN on 1991 -09-30 and. is identical to the IS0 Standard as referred to. CEN members are bound to comply with the CENICENELEC Internal Regulations which stipulate the conditions for giv
10、ing 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 GEN member. This European Standard exists in three official vers
11、ions (English, French, German). A ver- sion 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 offi- cial versions. CEN members are the national standards bodies of Austria, Belgi
12、um, 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 Stass
13、art 36, B-1050 Brussels 0 1991. Copyright reserved to all CEN members. Ref. No. EN 26948:1991 E Page 2 EN 26 948 : 1991 Foreword On the proposal of CEN/TC 69, CEN/BT decided to submit International Standard IS0 6948 : 1981 to Formal Vote. The result was positive. In accordance with the CENICENELEC I
14、nternal Regulations, 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. Automatic steam traps; productio
15、n and performance characteristic tests Endorsement notice The text of the International Standard IS0 6948:1981 was approved by CEN as a European Standard without any modification. Page 3 EN 26 948 : 1991 1 This International Standard specifies tests applicable to automatic steam traps. These tests,
16、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 to be performed relative to each one of
17、these two categories and describes briefly the corresponding test methods. Scope and field of application 2 References IS0 6552, Automatic steam traps - Terminology. IS0 6553, Automatic steam traps - Marking. IS0 6704, Automatic steam traps - Ciassification. 3 Definitions 3.1 production tests : Thos
18、e 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
19、 determine 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 w
20、ith 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 discharge condensate and close satisfactorily. Further details
21、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 give the purchaser at least five days notice of the date whe
22、n 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 of the derivation of each characteristic is given below;
23、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. 5.2 Maximum operating pressure (PMO) The steam trap shall
24、 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 which allows correct functioning. 5.4 Air venting capabili
25、ty The steam trap shall be tested to determine its ability to discharge air. Page 4 EN 26 948 : 1991 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.
26、6 Condensate capacity (OH or QC) 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. 6 Test methods 6.1 Shell testing The test flu
27、id, 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. NOTE - Various statutory authori
28、ties require 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
29、 or otherwise 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
30、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 assembled trap with the ends closed. For all traps, the hydraulic she
31、ll test shall be performed at a pressure 1,5 times the maximum allowable pressure at M 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 using liquid at a pressure equal to 1,5 times the maximum allowable pre
32、ssure at 20 OC or using gas at a pressure (gauge pressure) of 6 bar (0.6 Mpai. 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 Nominal trap sire Minimum t
33、est 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 condensate, the steam trap shall open (the time taken will vary as a funct
34、ion 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. 6.3 Determination of minimum operating pressure Operational checks,
35、 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 test pressure at which correct operation is observed. 6.4 Determination of maximum operating pressure The max
36、imum 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 shall open and close correctly throughout the test. 6.5 Determination o
37、f 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 of the steam trap. Whilst maintaining a reference pressure at the s
38、team 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 correct operation is still observed. Page 5 EN 26 948 : 1991 6.6 Ai
39、r 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 operating pressures, the temperature inside the trap being recorded. 6.7 Determinat
40、ion 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 allowed to cool slowly at the steam traps inlet. The temperature of the condensate, m
41、easured at the steam traps inlet, at which the device opens, is the operating temperature. 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 an
42、d condensate temperature. The test shall 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. The operating temperatures are the temperatures of the con- densate, measured at the inlet to the trap, at which the trap passes its specified capacities.
