The speed of the screw pump has its advantages and disadvantages. Generally, 200~400r/min is recommended abroad. Most Chinese oil fields use 100~300/min. The speed of the screw pump depends on the specific situation. If the pressure head and pump efficiency are too low, the displacement of the large pump in the shallow well is not enough, and the lifting head of the pump is small, the speed of the pump can be increased appropriately (250~350min); 60~150r/min should be used for wells with small displacement, low water cut and insufficient fluid supply.
The speed of the screw pump has a great influence on the pumping system of the screw pump. It is advantageous to increase the speed of the screw pump.
1. Favorable factors to increase the speed of the screw pump
(1) The higher the speed of the screw pump, the higher the pump efficiency. The working characteristics of the screw pump have both the hard characteristics of the plunger pump and the soft characteristics of the centrifugal pump. Especially when the pump leakage is serious and other conditions remain unchanged, increasing the pump speed can improve the pump efficiency.
(2) The higher the speed of the screw pump, the higher the lifting head of the pump. Under normal circumstances, the pressure head of the screw pump is related to the number of stages of the pump and the pressure-bearing capacity of the single stage. The more stages of the pump, the greater the single-stage pressure bearing capacity, and the greater the lifting head of the pump. To improve the single-stage pressure bearing capacity, the interference of the pump must be increased, which will increase the friction and reduce the efficiency of the screw pump pumping system. The pump pressure head can be increased by increasing the pump speed, and the pump pressure head can be increased by increasing the pump speed when the lifting head of the pump is not enough or the potential is small.
(3) The higher the speed of the pump, the larger the theoretical displacement of the pump. The theoretical displacement of the screw pump is directly proportional to the speed of the pump, so the adjustment of the speed of the pump should be considered when selecting the displacement.
(4) Under the conditions of the same pressure head and the same displacement of the pump, the torque at high speed is small.
2. Unfavorable factors to increase the speed of the screw pump
(1) The higher the speed of the screw pump, the greater the wear of the stator and rotor of the screw pump.
(2) The higher the speed of the screw pump, the greater the heat generated between the stator and rotor per unit length, which will cause thermal expansion of the rubber, increase the torque between the stator and the rotor, and increase the load on the entire pumping system.
(3) The high rotation speed of the screw pump increases the friction between the sucker rod and the oil pipe, which intensifies the wear between the oil pipe and the sucker rod.
(4) As the speed of the screw pump increases, the degree of fatigue of the rod-tube system increases. The force condition of the ground driving device becomes worse, and the power of the motor becomes larger.
