What is the difference between screw pump and rotary pump?

Both rotor pumps and screw pumps are volumetric pumps, and their performance is basically similar – both can smoothly convey high-viscosity materials and have high conveying pressures. So, what are the differences between rotor pumps and screw pumps?

  1. Different internal structure. The rotor pump conveys materials by rotating the two rotors in the opposite direction in the pump cavity, reducing the volume from the feed port to the delivery port, while the screw pump conveys materials by rotating the spiral screw in the rubber stator, so that the material rotates from front to back and finally is delivered from the discharge port.
  2. Different life of accessories. Since there is no friction between the rotor pump components, the wear parts of the rotor pump have a long service life, and the wear of the flow parts mainly comes from the abrasive and corrosive components in the medium; while the friction between the rotor and stator of the screw pump, the particles in the medium, etc., affect the service life of the wear parts at the same time. The stress generated by the eccentrically rotating rotor is all borne by the stator, which aggravates the wear between the components. Even if the medium without any particles is conveyed, the stator of the pump will gradually wear out.
  3. Different hygiene levels. The non-streamlined curved surface of the screw pump and the numerous defects in the chamber determine that it cannot be a sanitary pump. Damage to the PTFE or rubber of the cavity wall is more likely to cause pollution to the conveying medium. Due to the streamlined structure of the rotor and the lack of dead points and non-metallic parts in the rotor chamber, high-viscosity positive displacement pumps are more suitable for use in industries with high sanitary requirements such as food, beverage, and medicine, especially now that production lines are becoming more and more automated, and more and more online cleaning is being used, which further shows the importance of choosing a cam rotor pump. Therefore, the sanitary level of the rotor pump is higher than that of the screw pump.
  4. Different conveying directions. The conveying direction of the rotor pump can be reversed, and the pump is a completely symmetrical structure; while the screw pump cannot be reversed, and its seal is under pressure when conveying in the reverse direction.
  5. Different self-priming capabilities. The screw pump has good self-priming capabilities, but it is necessary to avoid idling of the pump body, and it cannot exceed 30 seconds; the rotor pump can produce good self-priming capabilities when the speed is greater than 200rpm.