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Reasons for Vibration of Hydraulic Gear Pump
Views: 925 Update Date: Dec 04 , 2018

When we use hydraulic gear pumps, we may meet some comment problems. The vibration is one of these problems. It can be caused by inhalation of air or mechanical transmission.

1. Causes of inhalation of air in gear pump

The vibration and noise of the gear pump are closely related to the intake of gas in the pump to a large extent. There are many ways for gas to enter the pump, mainly for the following reasons:

(1) Inhalation pipeline seal is not good, leading to air into the pump body. Solving this problem is relatively simple, and the leaking part is completely sealed.

(2) Generally, the pump body of gear pump and the end caps on both sides are hard seals in direct contact. If the flatness of the contact surface does not meet the required requirements, it is easy for the pump to inhale air when working. Similarly, the end caps of the pump and the pressure caps are also in direct contact, and the air is easy to penetrate. If the pressure caps are plastic products, because of their damage or temperature. Change and deformation will also make the seal not tightly into the air. When the flatness of the pump body or cover does not meet the prescribed requirements, it can be grinded back and forth on the flat plate with the "8" shaped grinding line with gold-steel sand, or on the surface grinder, so that the plane does not exceed 5 mm. It is also necessary to ensure the verticality of the plane and the hole.

(3) Gear pumps with skeleton oil seals for sealing shaft seals. If the spring of the lip is clamped off, or the oil package is reversed, or the lip is pulled, the back end of the oil seal will often be in a negative pressure state and inhale air, usually new oil seal can be replaced for interpretation.

(4) If there is insufficient oil in the oil pool or the suction nozzle is not found below the oil surface, the pump will inhale air. At this time, it should secrete the flushing oil into the oil tank to the oil marking line. If the return pipe is exposed to the oil surface, sometimes the air will be backfilled into the system because of the instantaneous negative pressure in the system, so the return pipe nozzle is usually inserted below the oil surface.

(5) The installation position of the pump is too high from the oil surface. Especially when the speed of the pump decreases, the air is sucked because the necessary positive vacancy of the pump suction chamber cannot be guaranteed. At this time, the relative height of the pump and the oil should be adjusted to meet the specified requirements.

(6) The oil-absorbing filter is blocked by dirt or its capacity is too small, which leads to the increase of oil-absorbing resistance and the inhalation of air. In addition, the larger diameter of the oil inlet and outlet may also bring air into the filter. At this time, the oil filter can be cleaned, or the filter with large capacity and appropriate inlet and outlet diameter can be selected. At this time, it can not only prevent inhalation of air, but also prevent noise.


2. Causes of mechanical transmission

(1) The connection between the gear pump and the coupling is out of order, which leads to the vibration and noise of the gear pump. The coupling should be adjusted according to the requirements.

(2) Noise is caused by wear and tear of gears and other parts caused by dirt in oil entering the pump. Oil should be replaced, filtering should be strengthened, pump should be removed and cleaned; gear with serious wear and tear should be repaired or replaced.

(3) Vibration and noise will occur if parts in pump are damaged or worn seriously: for example, the tooth profile error or pitch error is large, the contact between two gears is not idle, the tooth surface roughness is high, the common normal length is excessive, the backlash is too small, and the contact area between two meshing gears is not in the indexing circle position. At this time, the bearing can be replaced because the rotation is not smooth and the mechanical noise is generated. At this time, the gear pump needs to be dismantled and the needle roller bearing replaced.

(4) The axial assembly clearance of gears is too small; the movable joint between the end face of gears and the parts of front and rear end caps and the burr of gears before assembly are not carefully understood, so that the joint surface is damaged during operation, resulting in large internal leakage, resulting in a reduction of output flow; the dirt enters the pump and wedges into the gap between the end face of gears and the front and back of gears, resulting in a high joint surface. The low pressure cavity is connected by the radial pull or the groove, which reduces the output flow. The following measures should be taken to repair the above situation: dismantling the gear pump, properly increasing the axial clearance, that is, grinding the end face of the gear; grinding the front and rear end face of the gear with a surface grinder, and clearing the burrs on the gears (no chamfering); after surface grinding, the depth and size of the unloading groove on the front and rear end face also change. The width should be increased appropriately.

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