【国外标准】 Standard Practice for Sampling Steam

5.1 It is essential to extract and transport steam in a manner that provides the most representative sample of the process steam in order to accurately determine the amount of all impurities (dissolved chemicals, solid particles, chemicals absorbed on solid particles, water droplets) in it (1).3 An accurate measure of the purity of steam provides information that may be used to determine whether the purity of the steam is within necessary limits to prevent damage or deterioration (corrosion, solid particle erosion, flow-accelerated corrosion, and deposit buildup) of downstream equipment, such as turbines and process heat exchangers. The sources of impurities in the steam can include boiler water carryover, inefficient steam separators, natural salt solubility in the steam and other factors. The most commonly specified and analyzed parameters are sodium, silica, iron, copper, and cation conductivity.1.1 This practice covers the sampling of saturated and superheated steam. It is applicable to steam produced in fossil fired and nuclear boilers or by any other process means that is at a pressure sufficiently above atmospheric to establish the flow of a representative sample. It is also applicable to steam at lower and subatmospheric pressures for which means must be provided to establish representative flow.1.2 For information on specialized sampling equipment, tests or methods of analysis, reference should be made to the Annual Book of ASTM Standards, Vols 11.01 and 11.02, relating to water.1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversions to inch-pound units that are provided for information only and are not considered standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.