What is the difference between a single screw pump and a twin screw pump? Which is better?

Screw pumps can be divided into single screw pumps, twin screw pumps, and three screw pumps according to the number of internal screws. The main differences between single screw pumps and twin screw pumps are as follows:

• 1. Structural differences:

Single screw pump: There is only one screw shaft, and the single-headed male screw rotor rotates eccentrically in a special double-headed female screw stator (the stator is softer). It can swing back and forth along the center line of the pump and always keep meshing with the stator.

Twin screw pump: There are two screw shafts of the same size, one driving shaft and one driven shaft, which can achieve synchronous rotation through gear transmission.

• 2. Characteristics difference:

Single screw pump, the stator material will limit its operating temperature. It can transport liquids containing solid particles, and can also be used to transport various viscous liquids. It is also very suitable for transporting liquids with high viscosity and non-Newtonian fluids.

Twin-screw pump: insensitive to impurities; the gap between the screw and the pump body and the screw is 0.05~0.15mm, so the wear is small and the service life is long; the stuffing box only bears the suction pressure, so its leakage is small.

• 3. Difference in performance parameters:

Single screw pump: flow rate can reach 150m³/h, and pressure can reach 20MPa.

Twin screw pump: pressure is usually around 1.4MPa, below 7MPa for viscous liquids, and 3MPa for low viscosity liquids. The flow rate is usually 6~600m3/h, up to 1600m3/h, and the liquid viscosity shall not be greater than 1500m2/s.

• 4. Application difference:

Single screw pump: can be used to transport chocolate paste, starch paste, molasses, pulp, clay, mud, tar, paint, grease, paraffin, etc.

Twin screw pump: used for the transportation of high viscosity oils such as lubricating oil, grease, crude oil, tar, fuel oil, etc.

• Which is better, a single screw pump or a twin screw pump?

Compared with twin screw pumps, single screw pumps have their own advantages and disadvantages. It is not necessarily the case that one is better. The main thing is to choose the appropriate screw pump according to the medium being transported and the application:

1. The volumetric efficiency and pressure resistance of the single screw pump are the lowest, but the tolerance of the transported medium is the highest. It is suitable for conveying media with particles, viscous slurries, etc., and the flow rate and pressure do not need to be too large.

2. The volumetric efficiency of the twin screw pump is slightly higher, but the pressure is high. If the viscosity is low, the efficiency will drop quickly, the range of the transported medium is also wide, the displacement is also large, and it is more sensitive to the particle size. It is generally suitable for high-viscosity media with large flow, such as fuel oil, crude oil, etc., requiring large flow and high pressure, and is generally used as a delivery pump.