STF TRI SCREW PUMP

Model: STF

High-Efficiency Triple Rotor Positive Displacement Pump

The SPEW STF Series Tri-Screw Pump is a high pressure, Low flow, High-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 light-duty industrial and marine hydraulic oil service, the STF pump ensures reliable operation under high differential pressures with low thermal conditions.

Features

Feature	Benefit
Triple-rotor design	Smooth, non-pulsating delivery with minimal vibration and noise.
Hydrodynamic sealing	Leak-free operation without mechanical seal wear.
High-viscosity capability	Handles oils up to 760 Cst efficiently.
High suction lift	Self-priming with excellent NPSH characteristics.
Compact modular construction	Easy integration in confined skid or marine layouts.
Robust materials	Carbon-steel or alloyed construction for long life.
Low maintenance	Only one rotating element—no dynamic axial load.
Variable mounting	Horizontal, vertical, or submerged versions.

Structure

The STF Tri-Screw Pump consists of three intermeshing screws housed within a Very high 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 210 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.
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.