Generator Set Maintenance Flashcards

What is the purpose of a scheduled valve lash adjustment on a diesel generator engine?

Answer: To maintain proper clearance between valve stems and rocker arms for correct valve opening and closing

Valve lash settings ensure valves open and close at the correct time and duration; incorrect lash causes power loss, poor combustion, or valve damage.

When inspecting a generator's vibration isolation mounts during routine maintenance, which condition requires immediate replacement?

Answer: Complete separation, compression set greater than 30%, or oil saturation of the rubber element

Separated, severely compressed, or oil-soaked mounts can no longer isolate vibration, allowing damaging forces to transfer to the generator frame and foundation.

A generator set's engine governor is hunting (repeated speed fluctuation) at no load. Which maintenance action should be performed first?

Answer: Check and adjust governor droop setting and inspect linkage for binding or wear

Governor hunting is often caused by worn linkage creating feedback instability or incorrect droop settings; these should be inspected and adjusted before replacing components.

What is the recommended maximum time interval for exercising a standby diesel generator set under load to prevent fuel degradation and maintain readiness?

Answer: Monthly under load for at least 30 minutes

NFPA 110 and most manufacturers recommend monthly loaded exercise for a minimum of 30 minutes to maintain fuel system conditioning and verify operational readiness.

During a maintenance inspection, a technician notices the turbocharger compressor wheel has small nicks and erosion marks. What is the most likely cause?

Answer: Air filter bypass allowing dirt ingestion into the intake

Erosion and pitting on the compressor wheel are caused by abrasive particles entering through a compromised or missing air filtration system.

What is the significance of monitoring wet bulb temperature when performing generator cooling system evaluations?

Answer: It establishes the minimum achievable coolant temperature, affecting radiator sizing and heat rejection capacity

Wet bulb temperature defines the thermodynamic limit for heat rejection; ambient wet bulb values must be factored into cooling capacity calculations especially in humid climates.

When performing a 5,000-hour major overhaul on a diesel generator set, which component is typically evaluated using Plastigage during reassembly?

Answer: Crankshaft main and rod bearing clearances

Plastigage is a precision measurement method used to verify main and connecting rod bearing oil clearances during engine assembly to ensure proper lubrication film thickness.