What is a Pneumatic Temperature Controller?

Close-Up of a Pneumatic Temperature Controller

Oil and gas producers use a Pneumatic Temperature Controller to control a set temperature in production vessels. It is most commonly used in indirect heaters, emulsion treaters, rebillers, steam generators, heat exchangers, cooler shutter controls, and salt bath heaters.

How Does It Work?

Kimray's Pneumatic Temperature ControllerPneumatic Temperature Controllers have a stainless tube to monitor changing temperatures. This tube is connected to a diaphragm or a bellows assembly.

A pilot plug seat is throttled from the combination of differential pressure across the diaphragm or bellows and changes in the length of the stainless tube.

The pilot plug consists of two stainless balls fused together. One of these balls is the supply pressure inlet, and the other ball is the pressure vent.

Indirect vs. Direct Output Pressure

Line Art of a Pneumatic Temperature Controller

Pneumatic Temperature Controllers use both indirect and direct output pressure during operation.

Indirect output pressure can be sent to any pilot or control valve. In response to higher temperatures in the system, the stainless tube grows in length. This allows the tube to move the thermostat diaphragm. Then the output pressure decreases, causing the intended pilot or control valve action.

Direct output pressure is vented. This ensures that no signal is sent to the pilot or control valve. Much like the indirect output pressure, the direct output pressure lengthens the stainless tube so that it can move the thermostat diaphragm assembly toward the seat. The thermostat has a semi-throttle action, which accounts for output pressure increases and acts on the diaphragm.

Lastly, when the temperature begins to decrease, the action of the Pneumatic Temperature Controller is reversed to increase output pressure.


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Breck Swigart serves as a Product Manager at Kimray, and is responsible for Kimray’s line of pneumatic valves, pneumatic pilots, regulators and temperature controllers. He collaborates with Kimray’s engineering, manufacturing, and quality teams to optimize the performance of our products and make a difference for our customers.

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