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Proper selection of a three-screw pump is crucial to ensure optimal performance and prevent potential issues. If the pump is not chosen correctly, it may result in unsatisfactory operation, excessive noise, vibration, or even severe damage to internal components, leading to system failure. Therefore, careful consideration must be given during the selection process. A thorough understanding of the operating conditions is essential. In addition to basic parameters like flow rate and pressure, it's important to know the properties of the fluid being pumped—such as its corrosiveness, gas content, solid particle concentration, temperature, viscosity, specific gravity, and whether it contains any abrasive materials. Additionally, suction conditions and installation requirements should be clearly defined.
Based on our experience, the following points should be taken into account when selecting a three-screw pump:
1. **Pump Speed Selection**
- The speed should be determined based on the viscosity of the medium and the pump specifications. For high-viscosity fluids, a lower speed is recommended. When the viscosity is low, a higher speed can be used.
- If the viscosity is above 20 °E, for large pumps (with a main rod diameter of 60mm or more), a speed of 970rpm or 720rpm is appropriate. If the viscosity exceeds 80 °E, reduce the speed to 200–500rpm.
- For smaller pumps, if the viscosity is above 20 °E, 1450rpm or 970rpm is suitable. If the viscosity is higher (over 80 °E), the speed should be reduced to 300–600rpm.
- Higher speeds can lead to increased friction and wear, especially when the fluid has poor lubrication or contains impurities. In such cases, a lower speed (below 1450rpm) is recommended to extend the pump’s lifespan.
2. **Structural Selection**
- For pumping lubricating oil at temperatures below 80°C, a pump with an integrated bearing structure is suitable.
- If the temperature exceeds 80°C or the fluid has poor lubrication, a pump with an external bearing structure should be selected.
- If the fluid is highly viscous or has poor flowability, a double-layer heating structure is recommended.
- For high-temperature applications, a pump made from high-temperature-resistant materials should be used. Please consult with our factory for more details.
3. **Performance Relationships**
- At the same speed, flow and pressure are approximately linearly related. As pressure increases, flow tends to decrease.
- Flow is directly proportional to speed, assuming the same viscosity and pressure.
- Shaft power is also proportional to both pressure and speed, provided the viscosity remains constant.
- As viscosity increases, both flow and shaft power increase, but their relationship is complex. It is advisable to consult a specialist if needed.
With proper selection and regular maintenance, a three-screw pump can deliver excellent operational results and long-term reliability.