標(biāo)準(zhǔn)號：D1142-95
標(biāo)準(zhǔn)全稱應(yīng)該翻譯為：“露點(diǎn)溫度法測定氣體燃料中蒸汽含量的試驗(yàn)方法”
ASTM D1142 - 95（2006） Standard Test Method for Water Vapor Content of Gaseous Fuels by Measurement of Dew-Point Temperature
Significance and Use
Generally, contracts governing the pipeline transmission of natural gas contain specifications
limiting the maximum concentration of water vapor allowed. Excess water vapor can cause
corrosive conditions, degrading pipelines and equipment. It can also condense and freeze or form
methane hydrates causing blockages. Water-vapor content also affects the heating value of natural gas, thus influencing the quality of the gas.
This test method permits the determination of water content of natural gas.
1. Scope
1.1 This test method covers the determination of the water vapor content of gaseous fuels by measurement of the dew-point temperature and the calculation therefrom of the water vapor content. Note 1Some gaseous
fuels contain vapors of hydrocarbons or other components that easily condense into liquid and
sometimes interfere with or mask the water dew point. When this occurs, it is sometimes very
helpful to supplement the apparatus in with an optical attachment that uniformly illuminates the dew point mirror and also magnifies the condensate on the mirror. With this attachment it is possible,
in some cases, to observe separate condensation points of water vapor, hydrocarbons, and
glycolamines as well as ice points. However, if the dew point of the condensable hydrocarbons is
higher than the water vapor dew point, when such hydrocarbons are present in large amounts, they
may flood the mirror and obscure or wash off the water dew point. Best results in distinguishing
multiple component dew points are obtained when they are not too closely spaced.
Note 2
Condensation of water vapor on the dew-point mirror may appear as liquid water at temperatures as low as 0 to 10F （18 to 23C）. At lower
temperatures an ice point rather than a water dew point likely will be observed. The minimum dew
point of any vapor that can be observed is limited by the mechanical parts of the equipment. Mirror
temperatures as low as 150F （100C） have been measured, using liquid nitrogen as the coolant
with a thermocouple attached to the mirror, instead of a thermometer well.
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