Low dew point temperatures are maintained in compressed air or process gas pipelines up to 1/4″ outside diameter by fitting In-Line Desiccators
to reduce water vapor content to a safe level in systems with working pressures up to 60 psi.
While primarily used to remove water vapor as the prime source of contamination, the selective adsorption of other components of the gas can be achieved by careful selection of the grade and pore size of the molecular sieves desiccant.
Various grades of filters may be fitted in the dry gas outlet side of the dryer to ensure that the gas is cleaned to a specified level before it re-enters the gas line. Particulate cleanliness to below 1µm can be maintained by using special filters.
Actual water vapor content must be measured wherever dew point temperature or maximum water vapor concentration is specified and necessitates the use of a line dryer. Fitting a color-change Humidity Indicator signals when the maximum safe water vapor concentration of 2,560 ppmV at STP (about 14°F [-10°C] dew point). An in-line dew point temperature alarm should be fitted if the safe level required is lower than 2,500 ppmV.