Screw many factors affect the operating characteristics, wherein the amount of interference between the rotor and the stator and rotor speed, these two are the main factors
2.1Interference effect: Screw Works decided to guarantee a certain pump efficiency, it is necessary that the stator, the rotor surface contact line to maintain adequate seal, and the seal is dependent on the extent of the amount of interference between the rotor and the stator. Therefore, the amount of interference directly affects the size of the vacuum pump efficiency level
The difference between the amount of interference at different volumetric efficiency of large and therefore it will seriously affect the system efficiency of the pump. On the one hand, large interference obtain higher pump efficiency, but the rod of torque increase, prone tubing, rod broken off phenomenon, and the stator rubber wear is intensified, affect pump life; on the other hand, the amount of interference small though less prone to these problems, but the volumetric efficiency of the pump is too low, the system will reduce the efficiency of the pump. Therefore, to pump the amount of interference were reasonable choice. What is a reasonable amount of interference, that is, to ensure interference value under certain conditions for the lifting of pressure and volumetric efficiency
2.2 the influence of the rotor speed, the speed of the rotor determines the capacity of the screw pump. In the oil well productivity under the permission, the higher the speed of the rotor, the greater the displacement. However, the higher the speed, the centrifugal force of sucker rod is, the greater the bending vibration of sucker rod, the more serious, sucker rod coupling and the tubing wall friction will increase, at the same time, the lifting height will be increased due to frictional losses and the acceleration of the stator rubber wear. As a result, the rotor speed not too high, the general should be less than five hundred per minute to appropriate.
In addition to the above two factors, should also pay attention to the influence of medium viscosity. Because of the vacuum screw pump to lift crude oil and often used in practical application for the lifting of heavy oil, therefore, the pump in the process of lifting job characteristics and job characteristics when lifting water there will be a very big difference. On the one hand, the viscosity increase loss decreased to improve the volume of the pump efficiency and system efficiency; , on the other hand, the increase of the viscosity will be increased resistance to flow and reduce the full extent of the pump and the lifting height, decreases in the volume and the system efficiency of pump at the same time, increase friction will increase the resistance torque of pump. In practice, therefore, should give full attention to the influence of the viscosity