The Mark 82 is an internally piloted regulator offering better accuracy than a direct acting temperature regulator. The MK82 is available in two configurations, reverse and direct. The internal pilot valve seats and the main valve seats, in resting position, are up and closed. As the process temperature rises, the fluid in the sensing bulb vaporizes to apply pressure to the pilot diaphragm, opening the pilot valve. The upstream pressure passes through the pilot valve and the pilot port, opening the main valve to provide the required cooling action.