Working principle of first and third screw pump
Screw pump depends on screw intermeshing space volume change to transport liquid. When the screw rotates, the seal line at one end of the suction cavity moves continuously to one end of the outlet cavity, which increases the volume of the suction chamber and reduces the pressure. The liquid enters the suction chamber along the suction tube under the action of differential pressure. With the rotation of the screw, the liquid in the sealing chamber moves continuously and uniformly along the axial direction to the discharge chamber. Because the volume at one end of the discharge chamber is gradually reduced, the liquid is discharged. Screw pump is a volumetric pump whose pressure depends on the total resistance of the pipe system connected to it.
Two, the characteristics of screw pump: excellent self-priming performance is almost zero. The flow pulsation. The simple and compact structure. The extremely simple maintenance requirements. The satisfactory service life. The conveying medium without bubbles and vortex.
Types of transport media: 1, lubricating liquids, such as mechanical oil, spindle oil, transformer oil, heavy oil and residuum, etc.; 2, low lubricating liquids, such as wax oil, light diesel oil and heavy diesel oil, high temperature asphalt, coal tar, etc. 3, viscous liquids, Such as lubricating grease, viscose, asphalt, etc.
Advice on selection of four and three screw pumps
Although the three-screw pump has many advantages, if the type of the pump is not suitable, it will not only get no satisfactory operation effect, but also lead to the pump noise and vibration, and even seriously damage the internal parts of the pump, so that the pump system can not work properly. Type selection personnel should be considered carefully, reasonable selection, if necessary, should consult the technical department of our factory. When selecting a three-screw pump, the operating conditions of the pump should be understood as thoroughly as possible. In addition to the operation parameters, such as flow rate and pressure, the characteristics of the conveying medium such as the corrosion of the medium, the steam content, The ratio of solids to solids and the size of solid particles, as well as the working temperature, viscosity and specific gravity of the medium, According to our experience, we should pay attention to the following points when selecting the three-screw pump:
1.The rotational speed of the pump is determined by the viscosity of the conveying medium and the specification of the pump.
1.1 when conveying the high viscosity medium, the pump should select the low speed. If the viscosity is low, the corresponding choice is high speed: medium viscosity > 150cst. For large size pump (main rod diameter 60mm above, 970rpm or 720rpm speed is appropriate, if the viscosity is higher (viscosity of 600cstr), such as viscose, can reduce the speed of use, push recommending 200 - 500rpm ;
For small - sized pumps, when the medium viscosity is 150cst, the rotation speed is preferably 1450 rpm or 970 rpm, and if the viscosity is higher ( viscosity ) 600 cst ), the rotation speed can be reduced, and 300 - 600 rpm is recommended ;
1.2 because the higher the rotational speed of the pump, the smaller the volume of the pump under the same performance parameters, but because of the high rotational speed and high friction power, the pump has a large wear and short life, if the lubricity of the conveying medium is poor or contains trace impurities, Lower speed should be selected to keep the pump longer life, recommended below 1450rpm.
2.The selection of the structure can be made according to the pump installation and operation conditions, referring to the series and type of the three-screw pump.
2.1 conveying lubricating oil, temperature below 80 °C, choosing the pump with built-in bearing structure;
2.2 temperature exceeding 80 °C or conveying medium moistening When the sliding property is poor, the pump with external bearing structure shall be selected;
2.3 the pump with double-layer heating pump structure shall be selected when conveying medium with poor fluidity and high viscosity or when the medium is needed for heating or heat preservation;
2.4 when conveying at high temperature,Should choose the heat-resistant material made of pumps, please contact our factory.
3.Pump material combination choice: transport different properties of media, need different material combination.
1.The three-screw pump is divided into two types: the body sleeve one and the body sleeve separating.