- I) Structural difference
The single-head male spiral rotor of the single-screw pump rotates eccentrically in a special double-head female spiral stator (the stator is soft), and can swing back and forth along the center line of the pump, always keeping meshing with the stator. Click here to view the specific working principle of the single-screw pump. The twin-screw pump has two screw shafts of the same size, one is the driving shaft and the other is the driven shaft, which rotate synchronously through gear transmission. The three-screw pump uses the rotation of the screw to suck and discharge liquid. The middle screw is the active screw, which is driven by the prime mover to rotate, and the screws on both sides are driven screws, which rotate in the opposite direction with the active screw. The threads of the main and driven screws are both double-headed threads.
- II) Difference in performance parameters
Single-screw pump: flow rate can reach 150m³/h, pressure can reach 20MPa.
Twin-screw pump: The pressure is generally about 1.4MPa, 7MPa for viscous liquid, 3MPa for liquid with low viscosity, flow rate is 6~600m³/h, 1600m³/h, and the viscosity of the liquid shall not be greater than 1500mm²/s.
Three-screw pump: The flow range is 0.2~320m3/h, the pressure is about 3.4-340kgf/cm2, the flow rate can reach 18600cm3/min, the viscosity can reach 50000Mpa·s, the solid content can reach 50%, and the working temperature is 1~250°C. It needs to be specially made if it exceeds this temperature.
Features of single-screw pump:
- It can transport liquids containing solid particles;
- It can be used for fluids of almost any viscosity, especially for high viscosity and non-Newtonian fluids;
- The working temperature is limited by the stator material.
Applications: used for molasses, pulp, starch paste, chocolate paste, paint, asphalt, paraffin, grease, mud, clay, clay, etc.
Features of twin-screw pumps:
- The gap between the screw and the pump body, as well as between the screws, is 0.05~0.15mm, with less wear and long service life;
- The stuffing box is only affected by the suction pressure and has less leakage;
- Compared with three-screw pumps, it is not sensitive to impurities.
Applications: used for lubricating oil, grease, crude oil, asphalt, fuel oil and other high-viscosity oils.
Features of three-screw pumps:
- Wide pressure and flow range, flow range 0.2~320m3/h, working pressure up to 5MPa;
- Wide range of types and viscosity of transported liquids, viscosity range 1mm2/s-760mm2/s;
- Because the inertia force of the rotating parts in the three-screw pump is low, a very high speed can be used;
- Good suction performance, with strong self-priming ability;
- Uniform and continuous flow, small vibration, low noise, almost no pulsation;
- The three-screw pump has a solid structure, easy installation (horizontal, vertical, flange, plug-in) and easy maintenance;
- The three-screw pump has strong heat resistance, and the general working temperature is (1~250°C). It needs to be specially made if it exceeds this temperature;
- Heating or cooling structure can also be provided according to the needs of the transported medium;
- The three-screw pump has almost no wear, and the three-screw pump has a long service life as long as the selection is correct.
- Three-screw pumps have high working efficiency
Applications: used for lubricating oil, grease, crude oil, asphalt, fuel oil and other high-viscosity oils.
The above is an introduction to the differences and characteristics of three-screw pumps, twin-screw pumps and single-screw pumps. I believe everyone has a clear understanding. Of course, in addition to these three types, screw pumps can also manufacture screw pumps with more spiral heads of rotors and stators, such as pumps composed of three-head spiral rotors and two-head internal spiral stators, but the requirements for manufacturing accuracy are higher, and the flow rate does not always increase with the increase in the number of spiral heads, so it has little practical significance. Although this meshing pair of rotors and stators with more spiral heads has not been used in single-screw pumps, it has been widely used in the field of screw drilling tools in petroleum machinery.