Screw pumps are positive-displacement machines that transfer fluid by trapping it between helical screw threads and the pump casing, then progressing it axially from suction to discharge. They are the preferred choice for high-viscosity fluids and are valued for their low noise, minimal pulsation and gentle handling of shear-sensitive media.
History
The helical screw for lifting water is attributed to Archimedes of Syracuse, who described and applied the device for irrigation and ship bilge drainage around 250 BC — a design that still bears his name and remains in use for open-channel conveyance today. The enclosed twin-screw positive-displacement pump emerged in industrial form in the early twentieth century to meet the growing demand for clean, low-pulsation transfer of petroleum products and lubricating oils. The single-screw progressive cavity pump was patented in France in 1932 by René Moineau, a French engineer and aviator, who extended the screw principle to viscous, abrasive and solids-laden fluids — creating one of the most versatile positive-displacement designs in engineering history.
Operating Principle
One or more helical screws (rotors) mesh together inside a close-tolerance casing. As the screws rotate, the meshing threads seal successive pockets of fluid and advance them axially toward the discharge port. The fluid does not rotate with the screws — it travels in a straight line along the pump axis, resulting in extremely smooth, pulsation-free flow.
Rotor Configurations
- Single-screw (progressive cavity): One helical rotor turns inside a double-helix elastomer stator — handles viscous, abrasive and solids-laden fluids; flow is proportional to speed
- Twin-screw: Two intermeshing screws rotate in opposite directions — for clean to lightly contaminated oils and chemicals; capable of very high pressures
- Triple-screw: A central drive screw flanked by two idler screws — standard configuration for hydraulic and lube oil systems; compact and quiet
Key Technical Parameters
- Flow rate (Q): 0.1 to 3,000 m³/h depending on rotor geometry
- Differential pressure: Up to 300 bar for twin-screw; up to 48 bar for triple-screw
- Viscosity range: 1 cSt to over 1,000,000 cSt — screw pumps are purpose-built for viscous fluids
- Speed: Typically 500 to 6,000 RPM; lower speeds for abrasive or solids-laden media
- Temperature: Up to +350 °C with appropriate materials and shaft seals
Applications
- Crude oil and refined petroleum product transfer and loading
- Marine fuel oil, lubricating oil and hydraulic fluid systems
- Progressive cavity pumps for sludge, drilling mud and cement slurry
- Chocolate, honey, caramel and other viscous food products
- Polymer dosing and resin transfer in chemical plants
- Power plant auxiliary oil systems for turbines and compressors
Advantages
- Self-priming without external priming aids
- Handles gas-entrained and two-phase fluid mixtures
- Extremely low noise and vibration levels
- Flow rate is almost independent of discharge pressure — ideal for loading and transfer at fixed speed
- Gentle fluid handling — no impeller-induced shear
- Handles viscosities far beyond the capability of any centrifugal pump
Limitations
- Higher unit cost than centrifugal pumps of equivalent flow rate
- Close rotor-to-casing clearances mean abrasive particles cause accelerated wear
- Twin and triple-screw designs require clean fluid — filtration is essential
- Progressive cavity stators are subject to degradation from chemically aggressive fluids
- Flow rate decreases (slippage increases) as differential pressure rises
Selection Criteria
- Measure fluid viscosity across the full operating temperature range — viscosity drives rotor pitch and speed selection
- Determine abrasiveness and solids content — high solids favour progressive cavity; clean viscous oils favour twin or triple screw
- Calculate required differential pressure — twin-screw for high pressure, triple-screw for moderate hydraulic duty
- Verify NPSH availability — screw pumps can achieve suction lifts up to 9 m
- Select stator elastomer (for progressive cavity) compatible with fluid chemistry and temperature
- Match shaft seal type to fluid hazard level — mechanical seal for hydrocarbons, packing for abrasive slurries
Top 10 Manufacturers
- 1. Leistritz AG (Germany) — ~15% global market share; twin and triple screw for oil, gas and marine
- 2. IMO AB / Circor International (Sweden / USA) — ~13%; three-screw hydraulic and lube oil pumps
- 3. Allweiler / Circor (Germany / USA) — ~10%; industrial screw and progressive cavity
- 4. PCM Group (France) — ~9%; progressive cavity for oil and gas and food processing
- 5. Netzsch Pumpen und Systeme GmbH (Germany) — ~8%; progressing cavity for sludge and viscous media
- 6. Seepex GmbH (Germany) — ~8%; progressive cavity for food, pharma and chemical
- 7. SPX Flow Inc. (USA) — ~6%; sanitary progressive cavity pumps
- 8. Mono Pumps / NOV Inc. (UK / USA) — ~5%; mining and oilfield progressive cavity
- 9. IDEX / Viking Pump (USA) — ~4%; industrial twin screw and gear combination
- 10. Wangen Pumpen GmbH (Germany) — ~4%; progressive cavity for biogas and sewage sludge