Pneumatic temperature control pilots consist of a brass or stainless steel bulb temperature sensor that operates a valve controlling an air signal. These pilots may be used with diaphragm valves to control temperature only. Or, they may be used with pressure pilots to provide both temperature and pressure control.

When the pneumatic temperature pilot senses a temperature below its set point, it delivers an air signal to the air pilot based on the sensed temperature. This air signal becomes the air pilot loading force. If the main valve downstream pressure is below the air pilot loading force, the pilot valve diaphragm is no longer balanced. The air pilot valve opens and inlet pressure is passed through the air pilot to the signal line.

As the sensed temperature rises to the pneumatic temperature pilot set point, the temperature pilot valve closes and lowers the loading force to the air pilot. When the loading force decreases below the downstream pressure, the air pilot begins to close. Less steam passes through the air pilot to the signal line to the main valve, shutting off steam flow to the main valve diaphragm. The steam trapped under the main valve diaphragm bleeds off through an orifice, allowing the main valve to close.

• Pneumatic temperature control pilots may be combined with pressure pilots to provide multiple functions.
• Provide fast response over a minimal temperature change.
• Easily adjusted.
• Can be remotely located from the Main Valve and Air Pressure Control Pilot.
• Not affected by ambient temperature.
• Will not operate if air supply is interrupted.
• More costly than self-contained valves.

• Lightweight, compact size prevents strain on mounting pipes.
• Selection or components can provide either fail open or fail closed design.
• Optional wells allow bulb removal without draining system.
• Accuracy of control ± 4° F (± 2.2° C) with system recirculation.
• Series 315 PNT:

• For shop quality air:
• Minimum 15 psig (1.0 bar).
• Maximum36 psig (2.4 bar).
• Air consumption 0.50 scfm (0.014 m³).
• No limit to length of capillary.
• Bi-metallic temperature sensing.
• Temperature control ranges:
• 50 to 300 ° F (10 to 149 ° C).
• 200 to 450 ° F (93 to 232 ° C).

• Series 240 PNT:

• For control quality air
• Minimum 15 psig (1.0 bar).
• Maximum30 psig (2.1 bar).
• Low air consumption 0.008 scfm (0.00022 m³).
• Capillary length 6 ft. (1.8m).
• Copper sensing element.
• Temperature control range:
• -20 to 240 ° F (-7 to 116 ° C).
• Ambient Temperature range:
• 40 to 150 ° F (4 to 66 ° C).
• Signal range
• 0.5 psig (0.035 bar) minimum outlet pressure.
• To within 0.5 psig (0.035 bar) of supply pressure.