Could someone please explain the dew point temperature of the instrument air?

Dew point temperature: The temperature at which air must be cooled to reach saturation, under conditions of constant water vapor content and pressure. The purpose of providing a dew point temperature for instrument air is to prevent changes in ambient temperature from causing the water vapor in the instrument air to condense into water, thereby avoiding water contamination in the instrument air. Dew point temperature is related to pressure; as pressure decreases, the dew point temperature rises. The required dew point temperature is determined based on the required supply air pressure; in actual operation, the pressure of the instrument air is very low (for example, the starting pressure of the standard atmospheric pressure signal is 0.02 MPa, which is more than ten times lower than the supply air pressure). Therefore, such a requirement is set even though the local ambient temperature does not drop to -40°C. The dew point temperature of instrument air is generally set to be n°C lower than the local historical extreme minimum temperature (the petrochemical standard is 10°C lower).

It’s that when a certain temperature is reached, corrosion of the carbon steel portion increases significantly; this is generally checked when using nitrogen sealing.

Thank you very much for answering my questions. By the way, is there any petrochemical standard that provides specifications regarding dew point?

This post was last edited by feng*aosa on 2019-8-15 at 15:36

How does the dew point temperature rise when pressure decreases? Under the same conditions, the higher the pressure, the easier it is for dew to form, right?