Pressure and Temperature Control Valves

Pilot Operated Valves: Watson McDaniel HD series pilot operated regulating valves are used in steam applications to control pressure and/or temperature. Pilot operated regulating valves utilize a main regulating valve in conjunction with a separate control pilot. Pilot operated valves are more accurate and typically have higher flow capacities compared to direct acting regulating valves. The main regulating valve can be paired with a pressure pilot (sold separately) for steam pressure control or it can be paired with a temperature pilot (sold separately) for temperature control.

• Pressure Pilot

• Temperature Pilot

• Back Pressure Pilot

• On/Off Solenoid Pilot

• Differential Pressure Pilot

Pilot operated pressure regulating valves are commonly used for two applications within boiler feed systems: pressure control for pressurized deaerators, and temperature control for atmospheric feed tanks. When used on a deaerator, the main regulating valve is paired with a pressure pilot to create a pressure reducing valve. Most deaerators typically maintain a steam pressure between 3-10 psig. Steam is generated from the boiler at the boiler’s operating the pressure. The pressure reducing valve is used to regulate the flow of steam and maintain a steady operating pressure within the deaerator.

When used on an atmospheric feed tank, the main regulating valve is typically paired with a temperature pilot. As the name implies, these tanks operate at roughly atmospheric pressure (0 psig). Boiler feedwater typically needs to be at an elevated temperature to prevent thermal shock on the boiler. Direct steam injection via a sparge tube is often used to preheat the water. A temperature pilot is used to maintain a steady operating temperature within the feed tank. Note, many sparge tubes are designed with a maximum operating pressure in mind. In these cases, a temperature pilot AND a pressure pilot may be needed. The temperature pilot will maintain temperature within the tank and the pressure pilot will prevent the sparge assembly from exceeding it’s designed operating pressure. A pilot adapter (sold separately) is needed when using two or more pilots.

The HD series main regulating valve is available in sizes from ½” to 6” and the body is rated to 300 psig. The standard model should be used when the incoming pressure exceeds 15 psi. The low-pressure model should be used when the incoming pressure is less than 20 psi.