STM TRI SCREW PUMP

Model: STM

High-Efficiency Triple Rotor Positive Displacement Pump

The SPEW-STM Tri-Screw Pump represents the most advanced generation of triple-rotor positive displacement technology.
It is designed for continuous, High Pressure, medium flow, smooth, and pulsation-free transfer of lubricating liquids under high differential pressures.
The STM series combines precision screw geometry, hydrodynamic sealing, and close-tolerance construction to achieve exceptional efficiency and reliability across a broad viscosity range.

Engineered for critical process applications, the STM pump ensures constant flow irrespective of pressure or viscosity variations, with very low noise and vibration levels.
Its unique self-priming design, combined with robust metallurgy and superior surface finish, guarantees long life even under severe operating conditions — making it ideal for marine, power generation, refining, and lubrication system duties.

Features

Feature	Technical Explanation	User Benefit
Triple-Rotor Mechanism	One power rotor drives two idler rotors in precise synchronization.	Delivers a steady, pulsation-free discharge at all pressures.
Hydrodynamic Sealing	The pumped liquid forms a sealing film between rotors and casing.	Virtually leak-free operation with minimal wear.
High-Pressure Capability	Designed for up to 100 bar differential pressure.	Suitable for heavy-duty oil and hydraulic service.
Wide Viscosity Range	Handles fluids from 2 to 5,000 cSt.	Versatile for light fuels, lube oils, bitumen, and polymers.
Compact Modular Design	Close-coupled and foot-mounted options available.	Simplifies installation and skid integration.
Quiet, Smooth Running	Balanced hydraulic loads and continuous cavities.	Low vibration, low noise operation — ideal for continuous duty.
Self-Priming with High Suction Lift	Inherent screw geometry supports suction under vacuum.	Eliminates the need for separate priming systems.
Integrated Heating Jackets (Optional)	For handling heavy oils and waxy products.	Maintains fluid temperature and flow stability.
High Reliability Bearings	Radial/axial bearings isolated from hydraulic load.	Longer operational life and extended service intervals.
Service Accessibility	End-cover and cartridge-type assembly.	Easy maintenance and fast part replacement.

Structure

The STM Tri-Screw Pump consists of three intermeshing screws housed within a precision-bored casing insert.
The central power rotor, driven by a motor or gear reducer, transmits torque to two idler rotors via a thin film of pumped liquid.
These rotors form a sequence of progressing sealed cavities, which convey the fluid axially from suction to discharge without pulsation or turbulence.

Main Structural Components

Pump Casing:
Heavy-duty pressure-retaining body designed to withstand differential pressures up to 40 bar, incorporating suction and discharge ports optimized for laminar flow.
Rotor Set:
One drive screw and two symmetrically meshed idler screws manufactured from case-hardened or nitrided steel, ensuring perfect pitch alignment and minimal leakage.
Bearing Housing:
Supports the rotor assembly with high-precision antifriction or carbon bearings, isolated from the hydraulic zone to avoid contamination.
Mechanical Seal Assembly:
Available in single or double configuration, preventing leakage under high pressure and temperature.
Heating Jacket (Optional):
Integrated steam or thermal-oil jacket around casing and end cover to maintain product viscosity during start-up or transfer of high-viscosity media.
Drive Connection:
Direct-coupled via flexible coupling, or through gear reducer for low-speed, high-torque applications. Available with ATEX-rated motors for hazardous zones.
Relief Valve (Optional):
Integral or external bypass valve can be incorporated to protect the system against accidental overpressure.

Structural Advantages

Three-screw geometry ensures axial balancing of hydraulic forces, reducing bearing load.
Single rotating element contact eliminates wear points, increasing reliability.
Precision-machined clearances maintain high volumetric efficiency even at low viscosities.
Self-lubricating design eliminates the need for external lubrication.
Modular end-cover system simplifies service without disturbing connected piping.

-performance positive displacement unit engineered for continuous, low-noise transfer of clean lubricating liquids.
Its three precisely machined rotors operate within a close-tolerance housing to deliver constant, pulse-free flow, independent of pressure or viscosity variations. Designed for heavy-duty industrial and marine service, the STM pump ensures reliable operation under high differential pressures and demanding thermal conditions.