Which Instrument is Faulty? Transmitter, Recorder, or Controller

In this process, steam is introduced into “stripping” vessel C-7 to help remove volatile sulfur compounds from “sour” water.

The temperature of the stripped gases exiting the tower’s top is controlled by a pneumatic temperature control loop. Unfortunately, this loop seems to have a problem.

Which instrument is faulty?

Which instrument is faulty

The temperature indicating recorder TIR-21 registers 304 degrees Fahrenheit, while the temperature indicating controller TIC-21 registers 285 degrees Fahrenheit. The calibrated range of TT-21 is 100 to 350 degrees Fahrenheit.

A technician connects a test gauge to the pneumatic signal line and reads a pressure of 12.8 PSI:

Which instrument is faulty: the transmitter, the recorder, or the controller, or is it impossible to tell from what little information is given here?

Explanation

We know the indicating controller (TIC-21) must be miscalibrated because the pneumatic signal pressure of 12.8 PSI agrees with the recorder’s indication of 304 degrees F.

Interest to add any further points? Share your answers with us through the below comments section.

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Credits: Tony R. Kuphaldt

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Which Instrument is Faulty? Transmitter, Recorder, or Controller

 
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