Motor trips instantly on start or barring the coupling shows no rotation.
1
Oil starvation seized rotor bearings
criticalRotary screw
CheckIsolate and LOTO, remove coupling guard and attempt to bar the airend by hand. Check sump level and last oil change interval; look for varnished or black oil.
FixAirend replacement or factory rebuild. Correct the lubrication fault (blocked oil filter, failed thermostatic valve, wrong oil) before running the new unit.
ToolsSpanner / barring bar · Oil sample bottle
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2
Liquid slug / hydraulic lock in the airend
highRotary screw
CheckLook for oil above the sight glass and oil flooding back through the inlet valve after shutdown.
FixDrain excess oil, repair the leaking inlet valve or check valve that allows blowback, then bar over before restarting.
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3
Reverse rotation damage after phase change
criticalRotary screw
CheckConfirm rotation arrow against motor direction with a phase rotation meter before energising.
FixSwap any two incoming phases. Inspect the airend for rotor contact damage; a reversed screw can be destroyed in seconds.
ToolsPhase rotation meter
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4
Broken valve or piston debris in the cylinder (recip)
criticalReciprocating
CheckRemove the head and inspect valve plate, reeds and piston crown.
FixRebuild the pump: new valve plate, gaskets, and inspect the rod and crank for collateral damage.
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Safety
Lockout/tagout before opening enclosures. Verify zero energy. Bleed system pressure before opening any pneumatic connection.