Industrial fluid media cover a wide range of viscosity, including low-viscosity water, edible oil, medium-viscosity syrup and emulsion, ultra-high-viscosity grease, resin paste, yeast fermentation liquid and sludge colloid. Centrifugal pumps can only deliver thin fluid with high shear force, which is easy to cause foaming, material delamination and active ingredient damage; lobe pumps feature obvious pulsating flow and poor sterile performance. As a mainstream positive displacement rotary pump, screw pump has become the preferred conveying equipment for high-viscosity, shear-sensitive, particle-containing and sterile fluid working conditions. This article gives professional and popular definition of screw pump, elaborates operating principle, core classification, structural composition, advantages & limitations, material selection, industry application, operation rules and common misconceptions. It forms a complete technical document system together with sanitary twin screw pump for beer, high-viscosity electric drum pump and screw pump component articles, providing unified standard knowledge for equipment selection, workshop operation and foreign trade promotion.
A screw pump is a volumetric push-type fluid conveying equipment. Different from centrifugal pumps that rely on impeller suction, it pushes fluid forward stably through meshing and rotating screws. The medium is sealed in closed cavity and transported integrally without stirring, turbulence or easy foaming, suitable for almost all viscous fluid transportation.
A screw pump is a rotary positive displacement pump. It changes the volume of closed cavity via meshing motion between metal screws or screw-stator components, realizes negative pressure liquid suction, sealed medium isolation and pressure discharge, and completes axial continuous conveying, quantitative pressurization and bidirectional delivery of industrial fluid.
All industrial fluid pumps are divided into two major categories with essential operating differences:
Centrifugal Pump: Represented by ordinary impeller drum pump, fluid delivered by high-speed impeller suction, high shear, only for low-viscosity thin liquid.
Positive Displacement Pump: Represented by screw pump, lobe pump, gear pump and diaphragm pump, fluid delivered by cavity extrusion propulsion, strong adaptability for high viscosity, low shear and self-priming working conditions.
Core Positioning: Screw pump is the most adaptable positive displacement pump, covering viscosity range from thin water to 1,000,000 cSt ultra-high viscosity paste.
Invented in Germany in 1931, initially applied to ship hydraulic oil supply. After iterative upgrading, it has been widely used in food brewing, daily chemical, fine chemical, grease, environmental protection and fluid transfer industries, and has gradually become the first choice for high-viscosity fluid conveying worldwide.
The screw rotates to form independent closed sealed cavities. Fluid is locked inside the cavities, moving integrally from pump inlet to pump outlet in straight line. The whole process is smooth pushing delivery, no stirring, no eddy current, no air entrainment, no material damage.
Liquid Suction Stage: Meshing cavity volume expands to form negative pressure, medium enters the pump body automatically.
Closed Conveying Stage: Cavity fully closed, medium isolated completely without backflow, cross contamination or air mixing.
Pressure Discharge Stage: Cavity volume shrinks gradually, medium pressurized and discharged stably from outlet.
Core Feature: Integral translational conveying, different from open stirring conveying of centrifugal pumps.
Applicable viscosity: 1 cPs ~ 1,000,000 cSt
Self-priming capacity: Dry self-priming height up to 8-9m, no need pre-filling liquid
Shear performance: Adjustable ultra-low shear, protecting active material components
Flow state: Non-pulsating stable output
Operation mode: Bidirectional reversible rotation (forward feeding, reverse residual liquid recovery)
Allowable medium temperature: -10℃ ~ 135℃ (match different sealing materials)
Classified by screw quantity, three mainstream types cover all industrial working conditions, matching our full pump product line:
Metal helical rotor + elastic rubber stator + universal joint assembly + transmission shaft + mechanical seal + reduction motor
The rotor performs eccentric rotation and revolution inside the rubber stator, realizing sealing by rubber elastic deformation; metal rotor contacts the rubber stator directly during operation.
Pros: Low procurement cost, super strong self-priming performance, excellent ultra-high viscosity adaptability, easy to make plug-in drum type structure.
Cons: Direct friction between rotor and stator, rubber vulnerable to wear, slight shear force, not suitable for frequent high-temperature CIP/SIP sterilization.
High-viscosity electric drum pump, honey, malt syrup, grease, sludge, barreled paste, common industrial high-viscosity medium transfer.
Live yeast beer, aseptic pharmaceutical materials, working conditions prohibiting rubber precipitation, frequent high-temperature sterilization workshops.
Two conjugate stainless steel screws + external synchronous gearbox + streamline zero-dead-angle pump cavity + double-end sanitary mechanical seal
Driven by external synchronous gears, two screws rotate synchronously without any metal contact or friction, full metal flow passage without rubber medium contact.
Pros: Ultra-low shear, zero metal wear, support CIP online cleaning and SIP high-temperature sterilization, no rubber impurity precipitation, bidirectional stable operation, compatible with high & low viscosity media.
Cons: Precision structure, relatively higher manufacturing cost.
Sanitary twin screw pump: Special for beer brewing, craft draft beer, aseptic daily chemical, pharmaceutical ointment, high-end food production;
Industrial anti-corrosion twin screw pump: For corrosive glue, solvent resin, chemical paste transfer.
1 driving main screw + 2 driven auxiliary screws, fully closed oil lubrication meshing structure
Precision meshing operation, ultra-quiet running, high pressure and constant flow output.
Pros: High conveying pressure, stable oil supply, low noise, long service life for pure oil medium.
Cons: Cannot deliver medium containing solid particles, only applicable for oily fluid, narrow viscosity adaptation range.
Ship hydraulic system, industrial lubricating oil supply, high-pressure diesel delivery, mechanical hydraulic oil station.
| Item | Single Screw Pump | Twin Screw Pump | Three Screw Pump |
|---|---|---|---|
| Screw contact state | Metal-rubber contact friction | Zero metal contact | Metal meshing contact |
| Shear level | Low shear | Ultra-low shear | Medium shear |
| Sterilization adaptability | Not support frequent SIP | Support full CIP/SIP | Not sanitary type |
| Particle resistance | Good | Excellent | Poor |
| Cost level | Low | High | Medium |
Consistent with screw pump component article, divided into four functional modules:
Rotor, rubber stator, conjugate screw, pump body cavity; determine flow rate, pressure and viscosity adaptation capacity.
External synchronous gearbox, universal joint, transmission shaft, frequency conversion/reduction motor; realize torque transmission and screw synchronous operation.
Single/double-end mechanical seal, skeleton oil seal, isolation flushing chamber, food-grade anti-corrosion gasket; prevent liquid leakage and external air infiltration.
Sanitary tri-clamp inlet & outlet, anti-blocking feed base, pressure relief safety valve, explosion-proof module, frequency control cabinet.
Wide Viscosity Adaptability: Cover thin water to 1,000,000 cSt ultra-high viscosity paste, centrifugal pumps fail completely under viscosity over 1000 cPs.
Adjustable Ultra-Low Shear: Protect yeast activity, emulsion structure and material flavor, avoid beer foaming, oxidation and ingredient breakage.
Stable Non-Pulsating Delivery: Constant flow and pressure, improve filling qualification rate, reduce pipeline vibration.
Strong Self-Priming Performance: Dry self-priming available, no need pre-filling water, perfect for 200L standard drum material extraction.
Strong Working Condition Compatibility: Pass soft/hard particles, bidirectional operation, high-temperature sterilization, frequency speed regulation optional.
Low efficiency for large-flow thin water working conditions, inferior to centrifugal pump;
Rubber stator of single screw pump is wearing part, need periodic replacement;
Universal Operation Red Line: Strictly prohibit dry running, stator will burn out within 30s without medium lubrication;
Precision twin screw pump has higher initial procurement cost than ordinary impeller pumps.
Carbon steel: Ordinary industrial oil, non-corrosive wastewater;
304 stainless steel: Neutral food, daily chemical non-corrosive paste;
316L / 1.4404 passivated stainless steel: Beer, pharmaceutical, weak acid corrosive medium;
2205 duplex stainless steel: Medium & strong corrosive chemical colloid;
PP/PVDF anti-corrosion plastic: Strong acid and alkaline corrosive liquid.
NBR: Mineral oil, lubricating grease, neutral oily paste;
EPDM: Sugar liquid, fruit juice, cold beer, water-based food medium;
HNBR: 80-95℃ high-temperature wort, hot oil medium;
Food-grade silicone: Dairy products, high-end cream, FDA food contact standard;
FKM fluororubber: Organic solvent, high-concentration chemical glue, strong corrosive medium.
Beer wort, fresh draft beer, yeast liquid, jam, chocolate, pastry filling, condensed syrup (sanitary twin screw pump priority).
Emulsified cream, facial cream base, shampoo stock solution, thick essence paste.
High-viscosity resin, latex glue, printing ink, solvent additive, anti-corrosion thick slurry.
Butter, lithium grease, high-viscosity silicone oil, heavy crude oil, industrial lubricant.
Sludge sewage, kitchen waste slurry, high-concentration organic wastewater.
200L standard barrel on-site material extraction, matched with high-viscosity plug-in electric screw drum pump.
Never dry run without medium;
Start at low speed for ultra-high viscosity medium to avoid motor overload;
Reduce operating speed for particle-containing medium to lower component wear;
Complete closed-loop CIP cleaning after shutdown for sanitary food & beer working conditions.
Install pump horizontally as priority; design short straight inlet pipeline with fewer elbows to avoid air suction, medium foaming and oxidation.
Misconception: Higher rotating speed brings larger flow rate.
Correction: Screw flow depends on screw lead, not speed; high speed will cause material heating, shear damage and component wear.
Misconception: All screw pumps can deliver live yeast beer.
Correction: Only non-contact twin screw pump is available; single screw pump will break yeast cell walls by friction.
Misconception: Screw pump has the same working principle as gear pump.
Correction: Gear pump features strong squeezing shear; screw pump adopts integral translational low-shear conveying.
Misconception: All rubber stators are universal.
Correction: Rubber material must match medium acidity, alcohol and solvent to avoid swelling, cracking and odor migration.
Misconception: Self-priming capacity means the pump can run dry.
Correction: Self-priming refers to suction capacity, medium lubrication is indispensable for screw pump operation.
Large flow + thin water medium → Choose centrifugal pump
High viscosity + barreled material + low budget → Choose single screw pump
Aseptic production + anti-foaming + yeast protection → Choose sanitary twin screw pump
High-pressure oil supply + hydraulic system → Choose three screw pump
Essentially, a screw pump is a positive displacement translational push pump, conveying fluid via closed cavity volume change instead of centrifugal suction. Three core types have clear positioning: single screw pump focuses on cost-effective ultra-high viscosity transfer; twin screw pump focuses on low-shear aseptic food & beer conveying; three screw pump focuses on high-pressure pure oil supply.
It makes up the inherent defects of centrifugal pumps in high-viscosity, shear-sensitive and sterile working conditions. Standard use specifications include prohibiting dry running, matching material with medium property, selecting screw type according to process demand. Cooperated with standardized cleaning and periodic vulnerable part replacement, screw pump can realize long-term stable operation, which is the core general fluid conveying equipment for modern industrial production.