Triple screw or progressive cavity? Choosing by viscosity and solids

Triple screw pumps and progressive cavity pumps overlap on paper — both are positive displacement, both handle viscous media — but they behave very differently in service. The choice usually comes down to two questions: how much solid matter is present, and how much shear the product will tolerate.

Triple screw pumps are the better answer for clean, lubricating liquids at high pressure: fuel oils, hydraulic oils, lubricants and refinery products. They run at close tolerances, deliver a smooth pulseless flow, and give long life where the fluid actually lubricates the screw set. They dislike abrasives and dry running.

Progressive cavity pumps tolerate solids, abrasives and high viscosities, and are far more forgiving of poor suction conditions. Their trade-offs are lower pressure per stage, a larger footprint, and a stator that wears and needs replacing as a service item.

A practical rule: if the fluid is clean and lubricating and the pressure is high, look at triple screw first. If it contains solids, is abrasive, or is genuinely non-lubricating, look at progressive cavity first — and price the stator as a consumable rather than treating it as a failure.

Our catalogue carries both families, including Allweiler triple screw and progressive cavity ranges, so the comparison can be made on real curves rather than generalisations.