OIT Maintenance and Troubleshooting 3 — Questions and Answers
Question 1: During startup of a heat exchanger, tube-side outlet temperature does not rise as expected. What is the FIRST item to verify?
- Shell-side heating medium flow is open and flowing (Correct answer)
- Tube-side flow rate is at design
- Thermocouple calibration is correct
- The bypass valve is closed
Correct answer: Shell-side heating medium flow is open and flowing
Without adequate heating medium on the shell side, the heat exchanger cannot transfer heat to the tube-side fluid.
Question 2: A relief valve is found to be leaking slightly at normal operating pressure. What is the MOST likely cause?
- The set pressure is too close to operating pressure (Correct answer)
- The valve is undersized
- Inlet piping is too long
- The disc material is incompatible
Correct answer: The set pressure is too close to operating pressure
Operating too near the set pressure can cause the valve disc to lift slightly, resulting in simmering or leakage.
Question 3: An operator finds that a level transmitter is reading higher than the actual tank level. Which fault is MOST probable?
- The low-side impulse line is blocked (Correct answer)
- The high-side impulse line is blocked
- The transmitter span is too wide
- The tank has a dip tube installed
Correct answer: The low-side impulse line is blocked
A blocked low-side (reference) leg traps liquid and creates a false high-pressure signal, causing the transmitter to read high.
Question 4: What maintenance task should be performed before reinstalling a centrifugal pump after repairs?
- Check shaft alignment with the driver (Correct answer)
- Flush the discharge piping
- Calibrate the pressure gauges
- Test the motor insulation resistance
Correct answer: Check shaft alignment with the driver
Misalignment is a primary cause of vibration, seal failure, and bearing damage, so alignment must be verified before startup.
Question 5: Which instrument is used to measure shaft misalignment on rotating equipment?
- Dial indicator (Correct answer)
- Tachometer
- Megohmmeter
- Manometer
Correct answer: Dial indicator
A dial indicator measures the runout and offset between two rotating shafts to determine alignment quality.
Question 6: An operator smells burning insulation near a motor. What is the IMMEDIATE action?
- De-energize the motor and initiate lockout (Correct answer)
- Reduce motor load and continue monitoring
- Apply cooling water to the motor casing
- Increase ventilation to the motor room
Correct answer: De-energize the motor and initiate lockout
Burning insulation indicates imminent motor failure and possible fire; the motor must be de-energized immediately.
Question 7: What condition is indicated when a compressor discharge temperature rises above normal while suction conditions remain constant?
- Fouled or damaged discharge valves (Correct answer)
- High suction pressure
- Low compression ratio
- Excessive cooling water flow
Correct answer: Fouled or damaged discharge valves
Damaged or fouled discharge valves reduce compression efficiency, causing the gas to work harder and heat more.
OIT Maintenance and Troubleshooting 3
During startup of a heat exchanger, tube-side outlet temperature does not rise as expected.
What is the FIRST item to verify?