Screw pump selection

Screw pumps are suitable for transporting clean, lubricating fluids such as lubricating oil, fuel, and hydraulic oil. They can also handle high-viscosity substances like inks and adhesives, which is why they are also known as high-viscosity pumps. Because these media can form a lubricating film on the surface of the parts, providing protection and reducing the likelihood of direct contact between the helical surfaces as the screw rotates ； Screw pumps can also reduce leakage through the gaps ； Furthermore, since the gap between the helical surfaces during screw meshing, as well as the gap between the outer diameter of these helical surfaces and the inner diameter of the screw bushing, is relatively small (the higher the discharge pressure, the smaller the gaps are required in order to minimize leakage), any impurities—especially particulate, hard impurities—can get trapped if they enter the working section. Even small impurities such as metal shavings cannot be crushed or pushed into areas where there is no meshing due to the lack of forced transmission provided by synchronous gears or involute profiles; as a result, the impurities become stuck, preventing the pump from functioning properly. This can lead to surface damage in mild cases, while in severe cases it can cause the pump to seize. Therefore, screw pumps are very sensitive to impurities. It is particularly important to note that if certain ships use screw pumps as lubricating oil pumps, and these pumps are also required to function as oil transfer pumps for cleaning the system’s piping before mooring tests, then screw pumps are not suitable for this purpose. The impurities generated during the cleaning process can easily damage the pump; therefore, it is recommended to use five-screw or twin-screw pumps, which are less sensitive to such impurities, after taking appropriate measures.