Troubleshooting common gear pump failures

1. Causes and elimination of vibration and noise (1) Intake air 1CB-B gear pump's pump body is in direct contact with the hard seal of the two sides, if the contact surface flatness can not meet the requirements, the pump It is easy to inhale air during work; similarly, the end cap of the pump and the gland are also in direct contact with each other, and the air is also easy to invade; if the gland is a plastic product, due to its damage or deformation due to temperature changes, the seal will not be made. Strictly into the air. The method to eliminate this kind of trouble is: When the flatness of the pump body or the pump cover does not meet the specified requirements, it can be grinded on the flat plate with gold grit by "8" shape, or it can be grinded on the surface grinding machine. The flatness shall not exceed 5μm, and the perpendicularity of the plane and the hole shall be ensured; for the leakage of the pump cover and the gland, an adhesive such as epoxy resin may be used for sealing.

2 The pump shaft is generally sealed with a skeleton oil seal. If the spring that clamps the lip falls off, or the oil is reversed, or the lip is strained or deteriorated, the back end of the oil seal will always be under negative pressure and air will be sucked in. Generally, the new oil seal can be replaced to solve the problem.

3 If the oil in the fuel tank is not enough, or if the suction nozzle is not inserted below the oil level, the pump will inhale air. At this time, the oil should be added to the oil marking line; if the oil return surface is exposed, sometimes the oil will be exposed. Instantaneous negative pressure in the system causes air to backflow into the system, so the return pipe should generally be inserted below the oil level.

4 The installation position of the pump is too high from the oil level. Especially when the pump speed is reduced, air cannot be sucked due to insufficient vacuum in the pump suction chamber. At this point, the relative height between the pump and the oil level should be adjusted to meet the specified requirements.

(5) The suction filter is blocked by dirt or its capacity is too small, leading to increased suction resistance and inhalation of air. In addition, the larger diameter of the inlet and outlet ports may also cause air into the air. At this time, the oil filter can be cleaned, or the oil filter with a larger capacity and an appropriate inlet and outlet diameter can be selected. This will not only prevent the inhalation of air, but also prevent the generation of noise.

(2) Mechanical Cause 1 The connection between the pump and the coupling caused vibration and noise due to irregularities. Couplings should be adjusted as required.

2 As the dirt in the oil enters the pump, it causes the gears and other components to wear and cause noise. The oil should be replaced, and the filter must be reinforced to disassemble the pump for cleaning. For gears that are worn out, they must be repaired or replaced.

3 The damage or serious wear of the pump parts will cause vibration and noise: if the tooth shape error or the circumferential error is large, the two gears are in poor contact, the tooth surface roughness is high, the length of the common normal line is excessive, the backlash is too small, and the two meshing gears The contact area is not in the index circle position. At this point, you can change gears or gear pairs. At the same time, bearing needle roller cage damage, long-short-axis journal and needle wear, etc., can lead to bearing rotation is not smooth and produce mechanical noise, at this time need to remove the gear pump, replace the needle roller bearing.

4 Gear assembly axial clearance is too small; the sliding surface between the gear end face and the front and rear end covers can not be carefully removed due to gear burrs before assembly, thus pulling the joints during operation, so that the internal leakage is large, resulting in reduced output flow; Dirt enters the pump and wedges into the gap between the end surface of the gear and the front and rear end caps, causing the high and low pressure chambers to communicate due to the radial strained grooves, reducing the output flow. The following measures should be taken to repair the above situations respectively. Disassemble the gear pump, appropriately increase the axial clearance that is the end face of the grinding gear; use a surface grinder to flatten the front cover and the end face of the gear, and remove the burrs on the gear teeth (can not be chamfered); before and after grinding by plane The depth dimension of the relief groove on the end face of the end cap will vary, and the width should be appropriately increased.

(3) Other causes Oils with high viscosity may also generate noise. The fluid with the proper viscosity must be used.

2, the output flow is less than 1 high oil temperature will make its viscosity drop, increase the internal leakage, so that the pump output flow decreases. The cause should be identified and measures must be taken; for medium and high pressure gear pumps, the seal must be inspected for damage.

2 If the viscosity of the selected oil is too high or too low, the output flow rate of the pump will be reduced. The oil with acceptable viscosity should be used.

3CB-B gear pump can not be reversed in general. If the pump body is installed in reverse, the pressure oil chamber and the suction chamber will be short-circuited locally, so that the flow rate can be reduced or even not sucked. At this point, you should check the direction of the pump.

4 engine speed is not enough, resulting in reduced flow. The cause should be identified and eliminated.

3, poor rotation 1 axial clearance or radial clearance is too small. Re-adjustment and repair.

2 Dirt in the pump. Disintegrate to remove foreign matter.

3 The assembly is wrong. The machining reference plane of the two pin holes of the gear pump is not an assembly reference plane. If the pin is driven in first and then the screws are tightened, the pump will not move. The correct method is to tighten the screws while turning the gear pump, and finally match the drill hole and insert the pin.

4 Concentricity difference between the pump and the engine coupling. The coaxiality should be within 0.1mm.

5 The pump parts are not demagnetized. All parts must be demagnetized before assembly.

6 Roller cover failed or roll needle broken. Repair or replace.

7 The working oil outlet is blocked. Remove foreign objects.

4、Fever 1 Causes the gear pump to rotate poorly. All causes can cause the gear pump to heat up. Excluding methods can also refer to its implementation.

2 Oil viscosity is too high or too low. Reselect oil.

3 The side plates, bushings and gear end face are severely rubbed. Repair or replace.

4 The ambient temperature is high, the volume of the fuel tank is small, and poor heat dissipation will cause the pump to heat up. Should be dealt with separately.

5. Repair of main parts (1) Gear 1 Tooth repair: Use a fine emery cloth or oil stone to remove the parts that have been strained or have been ground into multiple prisms. Then change the orientation of the gear meshing surface and conduct appropriate research. Finally, clean it. For serious wear parts that can be observed with the naked eye, should be replaced.

2 End face repair: The gear end face wears due to the relative rotation with the bearing seat or the front cover and the back cover. When it is light, it will raise the wire. Grinding method can be used to grind and polish the burr marks. When the wear is serious, the gear should be placed on the surface grinding machine. Grinding. It should be noted that the two gears must be put on a surface grinding machine for grinding at the same time to ensure that the thickness difference between the two gears is within 5 μm; at the same time, it must be ensured that the perpendicularity of the end surface and the hole and the parallelism of both end surfaces are 5 μm. Within the range, use whetstone to invert the sharp edges, but do not chamfer them so that they do not have burrs and flashes.

3 When the meshing surface of the gear is worn, apply whetstone to remove the burr produced by the wear; at the same time, change the meshing orientation of the gear, and engage the tooth surface that originally did not mesh, thus not only ensuring its original working performance. , Can also extend the working life of the gear.

(2) The wear of the pump body is mainly on the side where the internal cavity contacts the gear term circle, and occurs mostly on the suction side. If the pump body is of symmetrical type, the pump body can be turned over 180 degrees before use; if the pump body is of asymmetric type, the wear part of the bore hole of the pump body needs to be repaired by electroplating bronze alloy technology or brush plating.

(3) Wear of the bearing race The raceway of the bearing is generally on the end face that contacts the gear and the inner hole that contacts the needle roller. When the end face wears or pulls up the line, four bearing races can be placed on a surface grinder, and the napped end faces can be ground with reference to the side that is not in contact with the gear. The accuracy should be within 10 μm. The bearing races generally wear less, and if worn, they can be ground; or they can be enlarged and the needle roller can be re-aligned; or the bearing race can be replaced.

(4) The failure of the long, short axis, and short axis is mainly due to the wear occurring at the contact with the needle roller bearing. If the wear is slight, it can be repaired by polishing (and replaced by a new needle roller bearing); if the wear is serious or broken, it needs to be repaired by chrome plating or re-worked. When reworking, the requirements for the parallelism and symmetry of the keyway on the long and short axes must be met; the clearance between the flat key and the gear keyway installed on the shaft must not be too large; the shaft must not be in the gear bore Radial oscillation occurs; the coaxiality of the surface of the journal and the mounting gear must not exceed 10μm, and the coaxiality of the journal at both ends must not exceed 20-30μm.