ASME PTC 39-2005 pdf free download.Steam Traps.
This Code covers steam traps which are devices used for removing condensate and noncondensibles from steam systems.
1-2 OBJECT
The purpose of this Code is to specify and define the practice of conducting tests of steam traps to determine:
(a) steam kiss, under specified conditions, This test procedure does not account for convection and radiation losses. These can be determined separately.
(b) condensate discharge capacity. for specified con• ditions of saturated and sttbconled condensate and back pressure.
(c) air and nonconden,sible gas removal capacity, under specified conditions.
1-3 UNCERTAINTY ANALYSIS
This Code includes the methods and examples to determine the uncertainty of the tests performed in accordance with it. This Committee prefers to define the test instrumentation and limit the allowable data fluctuations. This is equivalent to putting an upper limit on the allowable post-test uncertainty and ensures the validity of the test.
This Committee suggests that the post-test uncertainty should not exceed the following:
4-1 GENERAL
II any revisions are made to the methods and guidance provided in this Code, the estimation of their effed on test uncertainly shall be made and understood by all parties to the test. This Section presents the mandatory requirements for the instruments. methods, and precautions which shall he employed. The Instnjmont & Apparatus (l&A) Supplements should be constilted if sufFicient information is not included in this Section. By mutual agreement of the parties to the test, alternative instrumentation or instrument systems, such as flow metering or mass-flow techniques, may be used, provided that such devices or systems have demonstrated accuracy equivalent or greater to that required by this Code.
4-2 CALIBRATION OF INSTRUMENTS AND APPARATUS
lnstrunwnts and apparatus used for determination under this Code shall be calibrated in accordance with their respective l&A Supplement.
4-3 TEMPERATURE
Temvrature measurements shall be carried out in accordance with accepted practices and procedures as discussed in the IICA Supplement on Temperature Measurenient, PTC 19.3. Temperature shall be measured to within ±0.75F (0.4 K). To meet this accuracy requirement. temperature shall be measured with resistance thermometers or calibrated thermocouples used with precision reading instruments. Liquid-in-glass thermometers may be used for such secondary readings as ambient temperature for manometers and barometers. If liquid-in-glass thermometers are used to measure other variables, they must be calibrated, stem corrections must be applied, and graduations must be such that a precision of 0.F (0.1 K) is observable. Stagnation thermometer wells shall be used or computed velocity correction applied when the average steam velocity at the sensing point escevds 300 Ft/sec (100 mIs).
When the degree of subcooling is lOW (6 K) or less, the difference shall be measured by differential temperature sensing devices as prescribed in PTC 19.3.
Pressure transmitters. electronic pressure indicators, calibrated elastic gages, or nanometers shall be used for reading constant or slowly varying pressures..
(a) Manometers shall be of the vertical U-lube or single leg type with a minimum bore of ‘I lit (S mm). Spacing bchveen scale graduations shall not be more than l/ in, (3 mm), In a single leg manometer, means shall be available for adjusting the scale zero while the insinament is in use. Manometers shall be selected such that the scale length and the manometer fluid density permit a reading accuracy to within ±0.5% of the measured pressure or pressure difIen.ntial.
(Ii) Deadweight gages shall be selected with weights suitable for the pressure range to be measured in accordance with FTC 19.2.
(c) Bourdon gages or other elastic gages may be used for measurements of pressure provided that they are cal ihrated against a deadweight gage before and after the test. The ambient teii’iperature of the gage during calibration shall be within 2tY’F (10 K) of the ambient temperature prevailing during the Code test. The diameter of the scales and the arrangement of graduations shall pennit readability to within ±1.0% of the pressure being measured.
(d) Barometric pressure shall be measured to an accuracy within ±0.1 in. (2.5 mm) of mercury. The barometer shall be located in a stable environment at the test site and shall sense the same pressure as that of the gages and manometers used For the Code test. I’TC 19.2 should be used for the procedure for care and maintenance. and the application of appropriate corrections.