Typical structure of screw pump

Typical structure of screw pump

Figure g shows the structure of a high pressure balanced three screw screw pump with a special hole on the bushing. The special hole a on the outer sleeve leads the liquid in the high pressure chamber into the balance piston at the bottom of the screw. The driving screw 4 extends from the high pressure chamber and is supported by the radial ball bearing 2 to bear the residual axial force of the driving screw and fix its position. A large diameter shoulder is set at the high pressure end of the driving screw, and a high pressure thrust bearing unloading structure is adopted.

Figure h shows the screw pump structure with low pressure balanced unloading structure. The end chamber of the screw balance piston in the high-pressure chamber is communicated with the low-pressure chamber through the small hole a, the cavity B of the front cover 7, the oil return valve 9 and the deep hole C of the bushing to balance the axial force of the screw. The function of the oil return valve 9 is to keep a small back pressure in the end chamber and cavity B of the balance piston, so as to avoid the same vacuum state as the oil suction chamber and damage the lubricating oil film of the sliding bearing.

Figure I shows the structure of double suction screw pump. In order to make the shaft end easy to seal and reduce the unbalanced force caused by the extended end, the oil is usually absorbed on both sides and drained in the middle, and the axial force is basically balanced. The unbalanced force is caused by the difference between the atmospheric pressure and the pressure in the suction chamber.