Created on:2021-12-28 10:13

Fault analysis and treatment of large output pressure fluctuation and small flow of gear pump

Fault analysis and treatment of large output pressure fluctuation and small flow of gear pump

(1) Analysis and treatment of hydraulic oil pressure fluctuation and vibration fault

When CB-B gear pump is running, observe from the pressure gauge that if the pointer amplitude is greater than ± 0.15Mpa, it is called that the pressure fluctuation is large and accompanied by vibration. Especially when the output pressure is high and the flow is small, the hydraulic oil will produce large flow pulsation and cause high noise. The stability of hydraulic pump operation directly affects the stability of hydraulic oil flow, which is the root cause of flow noise. For the gear pump, the phenomenon of high noise, large pressure fluctuation and vibration often occurs and disappears at the same time. Therefore, the above reasons for high noise are also the reasons for high pressure fluctuation and vibration. See here.

(2) The output flow of gear pump is small or it is difficult to suck out hydraulic oil.

There are many and complex reasons why the output flow of gear pump is small or it is difficult to suck out hydraulic oil. The main reasons are as follows.

① Excessive oil suction resistance. When the oil filtering capacity of the selected oil filter is too small or it is seriously blocked due to hydraulic oil pollution, when the diameter of the oil suction pipe is too small and the viscosity of the hydraulic oil is too large, the oil suction resistance of the hydraulic pump will be large, resulting in difficulty in oil suction. A large vacuum degree is required during oil suction, resulting in noise.

② Oil leakage of gear pump is serious. The oil leakage mainly occurs on the sliding contact surface between the gear end face of the gear pump and the front and rear covers. The internal leakage caused by serious strain is too large, resulting in the reduction of output flow. The main causes of strain: first, the burr (on the tooth profile) of the gear was not carefully removed before assembly, and the joint surface was strained after operation; Second, dirt enters the pump and wedges into the sliding gap between the gear end face and the front and rear covers, damaging the mating surface, as shown in Figure J. the figure shows that the high and low pressure cavities are connected through the strained groove pores, resulting in output and flow reduction. This is very common. At this time, disassemble the gear pump, grind the front and rear cover end faces and gear end faces with flat grinding, and remove the burrs on the tooth profile (but not chamfer). The size of the unloading groove on the front and rear cover end faces after flat grinding will change, which should be deepened and widened appropriately.

JK.jpg

③ The parallelism of the axis of the gear shaft is out of tolerance. If the axis lines of the two bearing holes of the front and rear covers are not processed well or assembled well, the axis lines of the two gear shafts will not be parallel (skew), and the gear end face will eccentric wear the end faces of the front and rear covers, and the strain pattern is similar to that in Figure J, but it is not a full circle (fan-shaped circle), resulting in increased internal leakage. At this time, the treatment method is the same as above.

④ Large radial unbalance force. The radial unbalanced force causes the gear shaft to deform, collides with the inner cavity of the pump body, increases the radial clearance, and increases the internal leakage (Fig. K).

⑤ The hydraulic pump shaft is broken. The pump shaft is broken, and the motor drives the pump on the surface, but it is not oiled at all. Replace the pump shaft at this time.

⑥ The pump speed is not enough. The motor speed is not enough. The rated output flow of CB-B gear pump is calculated according to the motor speed of l450r / min. if it is lower than this speed, the flow will be reduced.

⑦ The pump body of the gear pump is installed reversely. After disassembly and repair, install the pump body reversely (Fig. L). At this time, the pressure oil in the pressure oil chamber P flows into the oil suction area o along the oil discharge groove E on the pump body, resulting in local short circuit and greatly reduced flow, so the pump body cannot be installed reversely.

⑧ The steering of the gear pump is incorrect. CB-B gear pump is a non forward and reverse pump (unless specified when ordering). When the pump turns wrong, it can not suck oil or the flow is very small. At this time, check the motor rotation.

⑨ The viscosity of hydraulic oil does not meet the requirements. When the viscosity of the selected oil is too high or too low, the viscosity is too high and the oil absorption resistance increases; If the viscosity is too low and the internal leakage is large, the output flow will be reduced. The oil with appropriate viscosity shall be selected according to the operation manual of the oil pump.

⑩ The temperature of the hydraulic oil is too high. If the oil temperature is too high, the temperature rise will reduce the oil viscosity, increase the internal leakage and reduce the output oil. At this time, it is necessary to find out the cause of high oil temperature and take corresponding measures. Centering high pressure gear

Pump, check whether the bow seal ring is damaged.

In addition, the internal and external leakage of the gear pump is large, resulting in insufficient output flow. See the description of "large internal and external leakage" below for details.

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