The HD Series Pilot-Operated Regulating Valve was designed for control of temperature and pressure in steam service applications. Several different control pilots can be mounted to the valve to control pressure, temperature, or a combination of both. When two or more pilots are used together (both a pressure and a temperature pilot) an additional pilot adapter for the second pilot is required (must indicate when ordering). The most common pilots are the PP-Pilot for pressure reducing, and the PT-Pilot for temperature control. The Main Valve and Pilot are purchased separately.