Advanced Diagnostics & Troubleshooting Flashcards
7 cards from real CPT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Advanced Diagnostics & Troubleshooting flashcards as text
A centrifugal pump is cavitating. Which corrective action addresses the root cause when suction pressure is too low?
Answer: Raise the liquid level in the suction vessel
Raising the suction vessel liquid level increases the available NPSH, eliminating the low-pressure condition that causes cavitation.
A control valve is hunting (oscillating continuously). The FIRST diagnostic step should be to:
Answer: Switch the controller to manual and observe if hunting stops
Switching to manual isolates whether the oscillation originates from the controller tuning or a mechanical problem with the valve itself.
An orifice plate flow meter reads higher than the actual flow. Which condition MOST likely causes this error?
Answer: Liquid density lower than calibration value
A lower-than-calibrated fluid density causes the meter to over-read because flow is calculated assuming the calibrated density.
During startup of a distillation column, tray flooding is suspected. Which symptom confirms flooding?
Answer: Differential pressure across the column increases suddenly
A sudden increase in column differential pressure indicates liquid backing up on the trays, confirming flooding conditions.
A temperature transmitter has a fixed positive offset error of +15°F across all measurements. This type of error is called:
Answer: Zero or bias error
A consistent offset across the entire measurement range is a zero (bias) error, indicating the transmitter baseline needs re-zeroing.
A heat exchanger's outlet temperature is declining over weeks despite steady inlet conditions. The MOST probable cause is:
Answer: Fouling on the heat transfer surfaces
Gradual performance decline over time with constant operating conditions is the classic signature of fouling accumulating on heat transfer surfaces.
A pneumatic signal line to a valve actuator is leaking. What effect will this have on a fail-open (air-to-close) valve?
Answer: Valve will open to a greater degree than commanded
Loss of air pressure in an air-to-close actuator causes the spring to open the valve further than the controller commands.