The time it takes to purge air from an oil-circulating temperature control system varies depending on the size of the process. According to the frequently asked questions page on, a good rule of thumb is to watch the discharge pressure gauge while purging. When the gauge becomes steady and the pressure is approximately twice the suction pressure, the system has been purged of air.

Based in Buffalo, N.Y., Mokon is a maker of circulating water and hot-oil systems, and portable chillers for thermal processing.