Three screw pump structure and working principle

The three-screw pump is mainly composed of a bushing (pump cylinder) fixed in the pump body, an active screw rod inserted in the pump cylinder and two driven screws which are engaged with the screw rod pump. Three intermeshing screws, in the pump cylinder by each lead to form a sealed chamber, resulting in suction and discharge between the seal. Pump work, due to the two driven screw symmetrical with the active screw meshing, so the role of the radial force on the active screw completely balanced, the active screw does not bear the bending load. The radial force exerted on the follower screw is supported by the pump cylinder bushing along its entire length. Therefore, it is not necessary to provide a separate bearing on the outer end and substantially not to bear the bending load. In operation, a layer of oil film formed between the outer surface of the screw and the inner wall of the pump cylinder can prevent the direct contact between the metal and greatly reduce the wear of the screw tooth surface. Screw pump work, both ends of the role of the liquid suction pressure, so the screw to produce axial thrust. For small pumps with differential pressure less than 10 kgf / cm2, thrust bearings can be used. In addition, high pressure oil is introduced into the bottom of each screw sleeve through the center bore of the active screw to create a balanced thrust at the lower end of the screw that is counter to axial thrust. Screw Pump Like other positive displacement pumps, when the pump outlet is completely closed, the pressure inside the pump rises to the point of damaging the pump or overloading the motor. Therefore, the suction pump outlet, you must set the safety valve. Three screw pump shaft seals, usually mechanical shaft seal, and the level of work under pressure can take different forms. More keyword search: Rod pump

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