Three-Screw Pump Overview

As a power source for liquid delivery, three-screw pumps are widely installed and matched in lubrication stations, hydraulic systems and process cooling systems, serving industrial fields such as shipbuilding, metallurgy, steel, petrochemical, electric power, mechanical processing, etc. Years of application experience have proven that three-screw pumps have obvious advantages over other positive displacement pumps in terms of economic benefits, delivery quality, service life and maintenance, making them the preferred matched pumps for these industries.

Although the screws rotate, the liquid in the closed chambers does not stir or vortex; it only moves axially along the main screw at low speed. Therefore, three-screw pumps feature excellent suction performance.

The main screw is fully hydraulically balanced, and the idler screws are hydraulically driven. Under normal operating conditions, there is no contact between the main and idler screws. The oil film prevents wear on the screw helical surfaces, resulting in a long service life.

It should be noted that during pump start-up and shutdown, the main and idler screws operate under boundary lubrication conditions, with momentary direct contact. The strength, surface hardness and machining accuracy of the screws must withstand such boundary conditions. In addition, the idler screws are subject to certain radial forces as determined by theory. Only when the screws, bushings, material selection and operating pressure are properly matched can the oil film between the outer diameter of the idler screws and the inner bore of the bushings be maintained without rupture, thus avoiding metal-to-metal contact and wear.

For lubricating oil transfer pumps, our company has mature technology and reliable processing methods to prevent the above failures.

Working Principle, Structure and Characteristics

The three-screw pump is a rotary positive displacement pump. Its working principle is as follows: a pump casing (or three-hole bushing) and three symmetrically parallel intermeshing screws form a series of isolated closed chambers. As the main screw rotates, fluid is drawn into the closed chambers. With the rotation of the main screw, the closed chambers move continuously and uniformly in the axial direction, conveying fluid from the suction chamber to the discharge chamber to achieve pumping and pressure boosting.

Three-screw pumps are suitable for conveying various lubricating liquids free of abrasive impurities and chemical corrosion to pump components. Examples include lubricating oil, mineral oil, synthetic hydraulic oil and natural oil. Other special lubricating media such as light fuel oil, heavy fuel oil, coal tar, high-temperature asphalt, viscous glue, emulsion, etc., can also be transferred. In such cases, please refer to the corresponding product catalogue for correct selection and application.

Product Features

1. Hydraulically balanced rotors, low vibration and low noise.
2. Stable output with no pulsation.
3. High efficiency.
4. Strong self-priming capability.
5. Series design with high interchangeability of parts and various installation types.
6. Compact structure, small size and light weight; capable of operating at high speed and high pressure.

Types of Conveyed Media

a. Lubricating liquids: such as machine oil, lubricating oil, heavy oil, residual oilb. Low-lubricity liquids: such as light diesel oil, heavy diesel oil, waxy thin oilc. Viscous liquids: such as various synthetic rubber solutions, artificial rubber solutions, emulsionsd. Heating or cooling jackets can be provided according to the conveyed medium.

Applications

• Used as fuel oil supply and transfer pumps in heating equipment.
• Used as hydraulic, lubrication and control motor pumps in machinery industry.
• Used as loading, transfer and supply pumps in chemical, petrochemical and food industries.
• Used on ships as transfer, boosting, fuel injection, lubricating oil pumps and marine hydraulic unit pumps.