Identifying Stator Wear

NickAcero

Progressive cavity pumps (PC pumps) are extremely versatile machines used across many industries for efficiently handling liquids and slurries. As with any mechanical component, the elastomer stators inside PC pumps will eventually wear out over time with use. Replacing worn stators is an important maintenance task to restore a pump's performance.

PC pumps work by using a helical rotor that rotates inside a dual-helix elastomer stator casing. As the rotor turns, cavities are formed between the rotor lobes and stator walls that progress fluid along the length of the pump. This progressively displaces fluid without subjecting it to high shear forces.

Common materials used for stators include nitrile (NBR), ethylene propylene (EPDM), chloroprene (CR), and fluoroelastomers like Viton. The stator material must be chemically compatible with the fluid being pumped and withstand operating temperatures, pressures, and abrasiveness.

Over time, normal operational factors like friction, pressure, and abrasive solids gradually erode stator elastomer. Signs it needs replacing include decreased pump efficiency, higher energy usage, reduced flow rates, and leakage past the stator. Visual inspection may reveal cracks, cuts, or noticeable thinning of the stator casing. Performance logs are helpful for tracking gradual degradation.

Early progressive pump replacement stators designs required significant downtime and work to swap out full stator casings, as piping had to be removed. Now, many manufacturers offer end-of-shaft designs allowing quick one-piece stator changes without touching connected plumbing. Self-tensioning systems also let operators adjust interference fit between rotor and new stator for optimal operation.

Replacement stators must closely match the original design specifications to fit properly and avoid premature wear. Select stators made of suitable elastomer for the fluid handled, plus the correct length, bore size, and cavity profile to interface precisely with the pump rotor. Authentic factory OEM parts ensure dimensional accuracy for long service life.

By understanding stator function and advancements in PC pump maintenance, operators can perform efficient stator changes to restore or exceed a pump's performance capabilities and maximum service intervals. Proper stator selection is key to avoiding additional repairs down the line.