CPT Advanced Diagnostics & Troubleshooting 2

Question 1

A centrifugal pump is cavitating. Which corrective action addresses the root cause when suction pressure is too low?

Accepted Answer

Raise the liquid level in the suction vessel

Answer

Raising the suction vessel liquid level increases the available NPSH, eliminating the low-pressure condition that causes cavitation.

Question 2

A control valve is hunting (oscillating continuously). The FIRST diagnostic step should be to:

Accepted Answer

Switch the controller to manual and observe if hunting stops

Answer

Switching to manual isolates whether the oscillation originates from the controller tuning or a mechanical problem with the valve itself.

Question 3

An orifice plate flow meter reads higher than the actual flow. Which condition MOST likely causes this error?

Accepted Answer

Liquid density lower than calibration value

Answer

A lower-than-calibrated fluid density causes the meter to over-read because flow is calculated assuming the calibrated density.

Question 4

During startup of a distillation column, tray flooding is suspected. Which symptom confirms flooding?

Accepted Answer

Differential pressure across the column increases suddenly

Answer

A sudden increase in column differential pressure indicates liquid backing up on the trays, confirming flooding conditions.

Question 5

A temperature transmitter has a fixed positive offset error of +15°F across all measurements. This type of error is called:

Accepted Answer

Zero or bias error

Answer

A consistent offset across the entire measurement range is a zero (bias) error, indicating the transmitter baseline needs re-zeroing.

(CPT) Certified Process Technician Practice Test