Screw Pump vs Gear Pump

Two Positive-Displacement Designs, Two Mechanisms

Both pumps are rotary positive-displacement (PD) machines: each shaft revolution moves a fixed volume of liquid, so flow tracks speed far more closely than discharge pressure. The similarity ends there — a screw pump conveys fluid along the axis of its screw or screws, while a gear pump carries fluid between meshing gear teeth and the casing. Both outperform centrifugal pumps as viscosity climbs, which is why Qingdao Green Power's published guidance for its IS/ISW centrifugal range is to switch to a gear or screw pump above about 150 cSt. The wider logic is covered in our centrifugal vs positive displacement pump comparison.

How a Screw Pump Works vs a Gear Pump

The G-type single screw pump is a progressive cavity design: a helical metal rotor turns inside an elastomeric stator, forming sealed cavities that travel steadily from suction to discharge. Flow is smooth and nearly pulseless, shear stays low, and the open passages handle media that would destroy a close-clearance pump — Qingdao Green Power lists high-viscosity oils and resins above about 1500 cSt, sludge, slurry, food pastes and shear-sensitive polymers, provided any solids stay below the minimum flow passage dimension. Because the elastomeric stator does the sealing, a G-type pump must never run dry: without liquid the rubber stator is destroyed within seconds.

The 3GB triple screw pump is a multi-screw rotary machine in which three intermeshing screws convey fluid axially. The pumped oil lubricates the screws, so this family is engineered for clean, low-viscosity oil at high temperature — published at 2.4–241.7 m³/h up to 350°C, which suits hot-oil circulation and thermal systems.

A gear pump works differently again. Two meshing gears trap liquid between the teeth and the casing and sweep it from inlet to outlet. Because the teeth themselves seal, clearances are deliberately tight, letting gear pumps reach high differential pressures in a small, economical package on clean lubricating fluids — but the same tight clearances rule out solids, abrasives and deposit-forming fluids.

Screw Pump vs Gear Pump at a Glance

When to Choose a Screw Pump

Choose a screw pump when the fluid is too thick, too abrasive or too temperature-demanding for a gear pump; within the family, the fluid decides the variant:

• G-type single screw — high-viscosity, shear-sensitive or abrasive media, food pastes and polymers, with smooth low-pulsation flow. See the G-type screw pump product range.
• 3GB triple screw — clean low-viscosity oil at high temperature, where the oil itself lubricates the screws; a proven fit for the duties covered in thermal oil pump selection.

When to Choose a Gear Pump

Choose a gear pump when the liquid is a clean, lubricating fluid — fuel oil, lubricating oil, hydraulic oil or similar — and the duty needs a compact, economical machine that reaches higher pressures without a larger PD pump. Gear pumps dominate lubrication and fuel systems on moderately viscous oils; our KCB gear pump selection article explains how to size that alternative for oil duties.

Viscosity, Temperature and Cleanliness Decide

Three questions settle most decisions. Viscosity: above about 150 cSt centrifugal pumps fall away and the choice is between PD types, with G-type screws leading on the very thick end. Temperature: hot, clean, low-viscosity oil points to the 3GB triple screw. Cleanliness: gear pumps reward clean lubricating fluids with compact, high-pressure performance, while solids or abrasives push the duty toward a G-type screw pump. If the product is food-grade and shear-sensitive, a rotary lobe pump is a third PD candidate — see the rotary lobe pump working principle guide. For any model, flow or pressure rating, confirm current model availability and specifications with Qingdao Green Power.

Frequently Asked Questions