Enlarge

DESCRIPTION

The INVALCO Model CTS-5025 Pneumatic - Type Temperature Controller provides pneumatic temperature control in a wide control range. It can be set to control at temperatures from 0°F to 750°F. Under laboratory conditions temperatures can be controlled within +/- 1°F. Actual operational range is determined by control location, circulation rate, etc. The stainless steel construction is a simple design - the head, inner valve, spring, and link can be removed, inspected, and reassembled in a short time. A 5°F temperature change causes 3-15 psi output signal change with 20 psi to 25 psi supply recommended.

Principal of Operation

This temperature controller utilizes the difference in thermal expansion coefficient of two materials to produce a mechanical motion. The simplified drawing (Figure 1) illustrates this principle. The sensing element of the controller is installed in the vessel. Temperature changes surrounding the element cause the following reactions:
1. The outer metal tube will expand on temperature increase or contract on temperature decrease. The change in length is proportional to the temperature change occurring.
2. The change in length of the inner rod which has a low expansion coefficient is negligible. However, since one end of it is attached to the outer metal tube, the inner rod moves as the outer tube length changes.
3. The opposite end of the inner rod pushes against and supports a floating link holding it concentric with a spring-loaded inner valve. With a temperature decrease, the inner rod applies pressure on the float-ing link, causing it to pivot around the adjacent fulcrum point which tilts the inner valve plug off its seat allowing the output signal to increase. The temperature adjust knob adjusts the setpoint by moving fulcrum point up or down.
4. When used with the standard head shown in Figure 2, an increase in temperature produces a decrease in output. By plugging the bleed, this head may be used for direct firing of burners.
Figure 3 illustrates the direct-acting head which, by changing the air flow through the head, gives an increase in output with an increase in temperature.