Progressive cavity screw pump for high-viscosity fluids: solutions up to 1,000,000 cps

High-viscosity fluids have high flow resistance, easily generating pressure losses in pipelines and adhering to pipe walls. With centrifugal pumps, increasing viscosity rapidly reduces efficiency and makes it difficult for the impeller to create a stable flow, so centrifugal pumps are mainly suited for thin fluids. Air-operated diaphragm pumps (AODD) can handle thicker fluids but exhibit pulsation due to the diaphragm stroke, causing pressure surges in the pipeline. Many thick media are also shear-sensitive: when agitated strongly, cream can separate, sauce can thin out, and gel can lose its structure.

Therefore, for high-viscosity fluids, a pumping principle is needed that can both generate stable pressure and minimise shear action on the fluid. This is the strength of the progressive cavity screw pump.

The progressive cavity screw pump (also known as a cavity pump) is a single-shaft positive displacement pump. A helical rotor (single start) made of steel rotates eccentrically inside a rubber stator (double start). As the rotor rotates, sealed cavities form between the rotor and stator, moving steadily from the suction end to the discharge end, conveying the fluid in individual “pockets” rather than agitating and pushing it like centrifugal impeller blades.

This mechanism delivers a steady flow rate proportional to rotational speed, with low pulsation and notably low shear — the key factor for preserving the structure of cream, sauce, gel, or emulsions. The pump can also convey fluids with solid particles and fibres, and is self-priming and reversible. The wobble variant (floating stator) simplifies the number of components, making it suitable for viscous fluids with low solids content.

The rotor–stator assembly is a wear part that deteriorates over time. An important operating note: do not allow the pump to run dry, as friction between the rotor and the rubber stator in the absence of fluid lubrication will cause the stator to burn. The stator material is selected according to the fluid, typically NBR, EPDM, or Viton.

For media so thick they barely flow under gravity, Nova Rotors offers a sanitary twin-screw range capable of handling very high viscosity up to 1,000,000 cps at pressures up to 25 bar. The two intermeshing screws create a gentle conveying flow with virtually no shear, suitable for thick pastes, concentrated molasses, heavy cream bases, thick sauces, and products that require full structural integrity.

In addition, the Nova Rotors Diamond progressive cavity range serves the majority of industrial high-viscosity fluid requirements with diverse configurations: standard DN-JN for general-purpose applications, hopper-feed DH-JH for thick materials (solids content up to 28%), sanitary DX-JX meeting EHEDG/3A with CIP/SIP for food processing, and vertical-shaft DV for high-viscosity fluids in industrial, chemical, and environmental applications.

In food and beverage, the progressive cavity screw pump conveys molasses, honey, thick syrups, tomato sauce, mayonnaise, cream, and heavy base mixtures while preserving texture and smoothness. In cosmetics, the pump is suited to gels, moisturising creams, thick shampoos, and emulsions requiring phase stability. In environmental and industrial treatment, the pump handles thick sludge, adhesive slurries, and fluids containing particles and fibres.

When selecting a pump, it is important to clearly define the actual viscosity at the operating temperature, solids content, corrosiveness, and hygiene requirements (sanitary or industrial grade) to choose the correct range and stator material. Accurately establishing these parameters helps the pump run reliably and extends the service life of wear parts.