Maintenance & Troubleshooting Techniques Flashcards

A control system is producing erratic outputs despite correct setpoint commands. After confirming the controller is functioning, the technician should next suspect:

Answer: Faulty or drifted sensor feedback causing incorrect process variable input

A controller acts on its input signal; if the sensor feeding it has drifted or is faulty, the output will be erratic even though the controller logic is correct.

What does a rising trend in oil analysis particle count for a gearbox indicate?

Answer: Increasing internal wear generating metallic debris

Increasing particle counts in oil analysis are an early warning of wear-related debris generation inside the gearbox before visible damage or vibration change occurs.

When troubleshooting a PLC-controlled system, the technician should first:

Answer: Review the fault log and I/O status on the programming terminal without interrupting production

The PLC's built-in diagnostics (fault log, I/O status display) provide immediate fault information non-invasively before any physical intervention is needed.

A motor draws higher than rated current at no load. This most likely indicates:

Answer: Internal winding short or insulation breakdown within the motor

Excess current at no load points to internal electrical faults such as shorted turns, which create high circulating currents independent of mechanical load.

Which Non-Destructive Testing (NDT) method is most suitable for detecting subsurface cracks in non-ferrous metal components?

Answer: Ultrasonic testing (UT)

Ultrasonic testing transmits sound waves through the material and detects reflections from subsurface defects, making it effective for non-ferrous metals unlike MPI.

When an equipment failure occurs during a critical operation window, the technician's first priority should be to:

Answer: Assess safety, isolate the fault, and restore operation using an approved workaround or spare

In a critical situation, safety assessment and rapid fault isolation to restore operability take priority over root cause investigation, which follows after stabilization.

A heat exchanger shows reduced heat transfer efficiency despite clean fluid flow. The most probable cause is:

Answer: Fouling or scaling on the heat transfer surfaces

Fouling deposits on heat transfer surfaces create an insulating layer that dramatically reduces thermal conductivity and overall heat exchanger performance.