When selecting the three-screw pump, it is necessary to understand the use conditions of the pump as much as possible. In addition to the operating parameters, such as flow rate and pressure, the characteristics of the transport medium, such as the corrosiveness of the medium, the vapor content, and the ratio of solid solution. And the size of the solid particles, as well as the working temperature, viscosity, specific gravity, corrosiveness of the material, etc., and the suction conditions of the pump device, the installation conditions must be understood. According to our experience, the following should be noted when selecting the three-screw pump. point:
First and third screw pump speed selection
The speed range is determined by the viscosity of the delivery medium and the specifications of the pump:
When conveying high viscosity media, the pump should be selected for low speed. If the viscosity is low, the high speed can be selected accordingly:
For medium viscosity > 20 ° E, for large-size three-screw pumps (over 60 mm outer diameter of main rod), the speed should be 970 rpm or 720 rpm, if the viscosity is higher (viscosity > 80 ° E), such as viscose, can be reduced Speed ​​use, recommended 200-500rpm;
For small-size three-screw pumps, when the medium viscosity is > 20 ° E, the rotation speed is 1450 rpm or 970 rpm. If the viscosity is higher (viscosity > 80 °E), the speed can be reduced. Recommended 300-600 rpm; The higher the pump, the smaller the volume of the pump under the same performance parameters. However, due to the high speed, the friction power is high, the wear of the pump is large, and the service life is short. If the lubricity of the transport medium is poor or contains trace impurities, it should be selected. Lower speed to keep the pump for a longer life, recommended below 1450 rpm.
Second, the choice of structural form
The choice of structure can be based on the operating environment of the pump and the installation environment, choose the appropriate installation form and follow the following principles:
1 . When a lubricating oil is delivered and the temperature is T < 80 °C, the pump with the built-in bearing structure is selected.
2 . If the conveying lubricity is poor, or when the temperature T > 80 °C, select the pump with the external bearing structure.
3 . When transporting a medium with low fluidity, high viscosity, or heating or holding the medium to be transported, a pump with a double-layer heat pump structure is selected.
4 . When transporting high temperature media, choose a pump made of high temperature resistant material or a locally cooled pump.
5 . The sample can be consulted about the pump's inhalation capacity.
Third, the choice of pump material combination
Fourth, the pump's ability to absorb
High suction performance can be achieved by reducing the rotational speed or heating to reduce the viscosity of the medium, see the NPSHR form.
Fifth, the matching of matching motors
After the model of the pump is selected, according to the sample data, the shaft power N of the pump can be found. After the power of the shaft is added with a certain power reserve, as the basis of the optional motor, the general motor power Nm is not less than the pump shaft power N times. The value obtained with the power coefficient K is: Nm ≥ K·N. The K value is obtained from the table below.
Sixth, in order to ensure the cleanliness of the pump medium, it is required to be equipped with a filter before the pump inlet, and the filtration precision is 40~80. Â Head.
In addition, when selecting the pump, the pump performance parameters provided by the sample are often given in the form of a table or a specific viscosity and speed performance curve. The performance value of the required pump may not be directly read out at this time. Principle, make a rough estimate. For more accurate data, consult a professional.
1 . The flow rate of the three-screw pump is approximately linear in the same speed and viscosity. The higher the pressure, the smaller the flow rate.
2 . The flow rate of the pump at the same viscosity and pressure is approximately proportional to the rotational speed.
3 . At the same speed and viscosity, the shaft power is approximately proportional to the pressure.
4 . Under the same viscosity and pressure, the shaft power is approximately proportional to the rotational speed.
When the viscosity increases, both the flow rate and the shaft power increase, but since the relationship is complicated, consult a professional if necessary.
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First and third screw pump speed selection
The speed range is determined by the viscosity of the delivery medium and the specifications of the pump:
When conveying high viscosity media, the pump should be selected for low speed. If the viscosity is low, the high speed can be selected accordingly:
For medium viscosity > 20 ° E, for large-size three-screw pumps (over 60 mm outer diameter of main rod), the speed should be 970 rpm or 720 rpm, if the viscosity is higher (viscosity > 80 ° E), such as viscose, can be reduced Speed ​​use, recommended 200-500rpm;
For small-size three-screw pumps, when the medium viscosity is > 20 ° E, the rotation speed is 1450 rpm or 970 rpm. If the viscosity is higher (viscosity > 80 °E), the speed can be reduced. Recommended 300-600 rpm; The higher the pump, the smaller the volume of the pump under the same performance parameters. However, due to the high speed, the friction power is high, the wear of the pump is large, and the service life is short. If the lubricity of the transport medium is poor or contains trace impurities, it should be selected. Lower speed to keep the pump for a longer life, recommended below 1450 rpm.
Second, the choice of structural form
The choice of structure can be based on the operating environment of the pump and the installation environment, choose the appropriate installation form and follow the following principles:
1 . When a lubricating oil is delivered and the temperature is T < 80 °C, the pump with the built-in bearing structure is selected.
2 . If the conveying lubricity is poor, or when the temperature T > 80 °C, select the pump with the external bearing structure.
3 . When transporting a medium with low fluidity, high viscosity, or heating or holding the medium to be transported, a pump with a double-layer heat pump structure is selected.
4 . When transporting high temperature media, choose a pump made of high temperature resistant material or a locally cooled pump.
5 . The sample can be consulted about the pump's inhalation capacity.
Third, the choice of pump material combination
Material combination code | Pump body | Vision set | Scope of application |
W1 | HT200 | Rare earth copper molybdenum ductile iron | Medium and low pressure conveying of poorly lubricated liquids such as fuel oil. |
W2 | HT200 | ZL109 | It can deliver low-lubricity, suitable viscosity liquids such as lubricating oil. |
W3 | QT450-10 | ZL109 | It is used for special occasions (such as marine pumps). It has good lubricity and good viscosity, such as lubricating oil. |
W5 | QT450-10 | Rare earth copper molybdenum ductile iron | It is used in special occasions (such as marine pumps) for low-lubricity and low-lubricity, such as fuel oil. |
W21 | HT200 | ZCuSn5Pb5Zn5 | It can deliver less lubricious or lower viscosity liquids such as heavy oil, fuel oil, diesel, etc. at lower pressures. |
W23 | QT450-10 | ZCuSn5Pb5Zn5 | For special occasions (such as marine pumps) or to deliver less lubricious, lower viscosity liquids such as heavy oil, fuel, diesel, etc. at higher pressures. |
W29 | 20 ( welding assembly ) | ZCuSn5Pb5Zn5 | For places with special requirements |
High suction performance can be achieved by reducing the rotational speed or heating to reduce the viscosity of the medium, see the NPSHR form.
Fifth, the matching of matching motors
After the model of the pump is selected, according to the sample data, the shaft power N of the pump can be found. After the power of the shaft is added with a certain power reserve, as the basis of the optional motor, the general motor power Nm is not less than the pump shaft power N times. The value obtained with the power coefficient K is: Nm ≥ K·N. The K value is obtained from the table below.
N (KW) | K |
N ≤ 5 | 1.25 |
5 < N ≤ 10 | 1.2 |
10 < N ≤ 50 | 1.15 |
N > 50 | 1.1 |
Sixth, in order to ensure the cleanliness of the pump medium, it is required to be equipped with a filter before the pump inlet, and the filtration precision is 40~80. Â Head.
In addition, when selecting the pump, the pump performance parameters provided by the sample are often given in the form of a table or a specific viscosity and speed performance curve. The performance value of the required pump may not be directly read out at this time. Principle, make a rough estimate. For more accurate data, consult a professional.
1 . The flow rate of the three-screw pump is approximately linear in the same speed and viscosity. The higher the pressure, the smaller the flow rate.
2 . The flow rate of the pump at the same viscosity and pressure is approximately proportional to the rotational speed.
3 . At the same speed and viscosity, the shaft power is approximately proportional to the pressure.
4 . Under the same viscosity and pressure, the shaft power is approximately proportional to the rotational speed.
When the viscosity increases, both the flow rate and the shaft power increase, but since the relationship is complicated, consult a professional if necessary.
Label: three screw pump  Three screw pump selection   Http://kpslgb.cn.gongchang.com
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Material: Q235 steel
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