Pump End 5–3
8. Slide the stator and liner off of the rotor. The liner may be inside of the suction
housing. The liner must be removed and replaced when the stator is replaced. The
liner protects the stator from wearing against the suction housing.
9. Inspect the stator for wear. The next section describes types and causes of wear.
Determining the cause of wear is important or the pump will fail again. The average
life of a stator is eight to 10 years.
Pump Stator Inspection
Three types of stator wear can cause pump failure: a tear or hole in the stator, worn lobes or a
swollen stator. Each type of stator wear is described below.
Tear/Hole in the Pump Stator
A hole or tear in the stator is caused by a blockage in the discharge line. If the pump runs for
a long period of time against a blocked line, the high pressure (approximately 150 psi) in the
pump cavity will rupture or tear the stator.
The blockage must be cleared before the pump is put back into service. Check the discharge
line for a plugged line, closed valve, frozen valve or bad check valve/anti-siphon.
Worn Lobes
Examine the lobed area in the center of the stator. Normally, the rubber lobes are rounded at
the high points; worn lobes are attened at the high points. On attened lobes, the texture of
the worn rubber is either smooth or rough.
Stator lobes that have worn rough display one or more of the following characteristics:
• Wear looks rough and loose pieces of rubber hang from the lobes
• Rubber is stuck in the lower valley between the lobes
• Rubber is soft or has hard spots on it
• Worn lobes display surface cracks that resemble weather-checking on an old tire
• Rotor has rubber stuck to it
Figure 5-6
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