Detailed Explanation of Screw Pumps

Working Principle and Practical Applications

Screw pumps are one of the oldest and most reliable positive displacement pump technologies in the industrial fluid handling sector. Their full product range, including single-screw, twin-screw, and triple-screw pumps, is widely used in oil and gas, chemical, marine, and other industries. These pumps have gained global customer recognition for their reliable performance and customized solutions. Despite their simple structure, many engineers lack a thorough understanding of their working principle and selection applications. This article provides a detailed explanation based on TEFFIKO engineering practice to support equipment selection decisions and maximize the optimal performance of screw pumps.

Working Principle of Screw Pumps

The core of a screw pump is to convey fluid along the axis of one or more rotating screws. When the screws rotate, the helical structure forms sealed chambers that move from the suction port to the discharge port. Each rotation entrains a fixed volume of fluid and pushes it forward.

Its key advantage is pulse-free flow. Unlike centrifugal pumps that convey fluid by kinetic energy, screw pumps deliver nearly constant flow, which is critical for process-sensitive applications such as lubrication systems, hydraulic drives, and precision metering.

Single-Screw, Twin-Screw and Triple-Screw Structures

• Single-screw pump (cavity pump) operates with a rotating rotor and a fixed rubber stator. The screw structure forms multiple continuous chambers that propel fluid from the suction port to the discharge port. It is suitable for high-viscosity and shear-sensitive fluids but has limitations in rotational speed and temperature resistance.
• Twin-screw pump adopts two intermeshing, counter-rotating screws. It can handle high-viscosity and semi-volatile fluids, operates at higher speeds than single-screw pumps, and is widely used in crude oil pipeline transportation, refinery crude oil feeding, and hydraulic systems.
• Triple-screw pump consists of one driving screw and two driven screws. The meshing of the driving screw thread with the driven screws forms sealed chambers, offering higher pressure and better efficiency. It is suitable for clean, lubricating liquids such as hydraulic oil and fuel oil.

Core Advantages Over Centrifugal Pumps

• Strong self-priming capability: Suction lift can reach more than 6 meters, no additional priming equipment is required, startup is fast, and it adapts to low liquid level and frequent start-stop scenarios.
• Adaptable to high-viscosity media: The higher the medium viscosity, the more stable the conveying performance, which centrifugal pumps can hardly achieve.
• Low-shear conveyance: Fluid is conveyed smoothly along the axial direction without turbulence, suitable for emulsions and suspensions, and effectively protects shear-sensitive media.
• Stable flow rate: No pressure pulsation, reduces pipeline stress, operates with lower noise, and ensures stable production processes.
• Bi-directional operation: Fluid can be conveyed in reverse by changing the rotation direction of the screws, offering flexibility for more industrial scenarios.

Common Application Areas

• Oil and gas industry: Crude oil transportation, pipeline pressurization, fuel oil supply.
• Hydraulic systems: Industrial presses, mobile equipment, marine steering gears.
• Lubrication systems: Gearbox, compressor, and steam turbine lubrication – the pulse-free conveying feature avoids pressure fluctuations in lubrication systems and extends equipment service life.
• Refining industry: Asphalt, residual oil, and polymer transportation.
• Chemical industry: Resin, adhesive, and printing ink transportation – low-shear conveyance protects medium properties, prevents product deterioration, and adapts to corrosive and high-viscosity media.
• Marine sector: Deck machinery, engine lubrication, ballast systems – TEFFIKO screw pumps adapt to complex marine working conditions, resist vibration and impact, and ensure navigation safety.

Operating Condition Range

Screw pumps perform best within specific parameter ranges. The optimal operating conditions are as follows:

• Rotational speed: 1000–3600 rpm for twin/triple-screw pumps; 300–1800 rpm for single-screw pumps (lower speed).
• Viscosity: Optimum applicable viscosity is typically 10–1000 cSt; designs for lower or higher viscosity media are also available.
• Pressure: Twin/triple-screw pumps can reach over 200 bar; single-screw pumps are usually below 20 bar.
• Temperature: Limited by bearing and screw materials, general applicable temperature range is -40℃ to +300℃.

Operation beyond the above conditions will accelerate component wear and even cause damage.

Common Failure Modes and Preventive Measures

• Bearing wear: Bearings are subjected to continuous radial and axial loads. Select bearings with appropriate rated load and monitor temperature.
• Screw wear: Abrasive particles in the medium will erode the screw surface. Install a filter at the inlet or use screws made of hardened materials.
• Dry-run damage: Single-screw pumps with rubber stators will be damaged instantly during dry running. Equip with a dry-run protection device.
• Overheating damage: High-pressure and low-flow conditions tend to cause medium temperature rise. Install a minimum flow recirculation or heat dissipation device.

Misconceptions to Avoid in Selection

• Do not select based on clean water performance curves, as medium viscosity significantly affects pump performance.
• Do not ignore the Net Positive Suction Head Required (NPSHr), especially for high-viscosity media.
• Do not select only based on maximum flow rate; consider the flow regulation range and part-load efficiency.

Summary

Screw pumps have irreplaceable advantages over centrifugal pumps: they can convey high-viscosity, lubricating, and shear-sensitive media, achieve pulse-free conveyance, and feature excellent self-priming capability. Mastering their basic principles helps engineers make reasonable selections and avoid premature equipment failure caused by common mistakes. As a global leading brand with 20 years of expertise in the screw pump field, TEFFIKO provides reliable and efficient screw pump conveying services to industries worldwide with advanced R&D technology, strict quality inspection (100% full inspection of all products), full product range coverage, and customized solutions. We support customers throughout the process from selection guidance, equipment supply to after-sales support, helping them achieve efficient and stable equipment operation and unlock new value in industrial fluid handling.