Eccentric Screw Metering Pump (DM Nova Rotors): Precise Metering for Viscous & Particle-Laden Fluids

An eccentric screw pump consists of a helical steel rotor that rotates eccentrically inside a rubber stator with a helical profile. As the rotor turns, sealed cavities (cavities) form between the rotor and stator and move continuously and uniformly along the axis from the suction end to the discharge end. Each revolution displaces a nearly constant cavity volume, so the delivered volume is directly proportional to the number of shaft revolutions.

This characteristic turns the PC pump into a volumetric metering device: instead of controlling by cycle as with an air-operated diaphragm pump or by piston stroke, the screw pump meters by controlling shaft speed through a variable frequency drive (VFD). The flow is nearly continuous and low-pulsation, so batch accuracy and repeatability are maintained even with viscous or particle-laden fluids. The pump is self-priming and can reverse direction when reverse suction or line purging is required.

Nova Rotors developed the DM metering series based on the eccentric screw principle, divided into two application groups. The industrial metering version delivers steady flow rate directly proportional to speed, suitable for dosing viscous chemicals, additives, and particle-laden fluids in processing lines. The sanitary metering version targets food and pharmaceutical products such as creams, sauces, gels, and honey — where precise dosing and preservation of the structure of shear-sensitive products are both required.

Because the delivery mechanism is a uniformly traveling sealed cavity, the DM pump exerts low shear on the fluid. This is a differentiating factor when dispensing fluids with visible particulate phases (meat, fruit pieces, seeds) or gels prone to phase separation: the product passes through the pump with its state nearly intact. For applications requiring size reduction of solids before metering, or for handling sludge, wastewater, or pharmaceuticals, Nova Rotors also offers a twin-shaft grinder/macerator that can be fitted at the inlet.

A diaphragm metering pump (AODD or mechanical) delivers by cycle so the outlet flow has pulses, and with very viscous fluids or large particles the check valves can jam or leak. A piston metering pump provides high accuracy with low-viscosity fluids but also relies on a valve system and struggles to handle viscous or particle-laden fluids consistently. The eccentric screw pump uses no valves inside the pump chamber and produces near-continuous flow, so it maintains evenness as the fluid thickens or contains particles.

In return, the rotor and stator are a wear pair that require periodic replacement, and the pump must never run dry because friction will burn the rubber stator. Dry-run protection and correct stator material selection according to the fluid should therefore be incorporated at the design stage.

In food and beverage, the sanitary DM pump is used to fill and meter creams, sauces, jams, gels, honey, and particulate fillings into packaging, or to feed batches for mixing operations, with hygiene and product-structure-preservation requirements. In pharmaceuticals and cosmetics, the series doses viscous liquids, gels, and base creams in consistent quantities. In industrial and chemical applications, the industrial metering version is used to inject additives, viscous chemicals, and particle-laden fluids into processes.

Where highly corrosive fluids or specific installation configurations are required, the Nova Rotors product range includes related series to extend the application scope — further details are available on the brand page. For each project, selecting the rubber stator (NBR, EPDM, Viton) according to the chemical properties and temperature of the fluid is the determining factor for service life and dose stability.