Analysis of the failure and maintenance of forklift gear pumps

The gear pump is a rotary pump that relies on the change and movement of the working volume formed between the pump cylinder and the meshing gears to transport liquid or increase its pressure. It consists of two closed spaces, two gears, a pump body, and front and rear covers. When the gears rotate, the volume of the space on the gear disengagement side changes from small to large, forming a vacuum, sucking in the liquid, and the volume of the space on the gear meshing side changes from large to small, squeezing the liquid into the pipeline. The suction chamber and the discharge chamber are separated by the meshing line of the two gears. The pressure at the discharge port of the gear pump depends entirely on the size of the resistance at the pump outlet. Let's share the causes and troubleshooting methods of gear pump failures.

Failure cause 1: The oil level in the hydraulic oil tank is too low

Troubleshooting method: Add hydraulic oil

Failure cause 2: Hydraulic oil is not used according to the season

Troubleshooting method: Usually 46# hydraulic oil (or 68#) is applicable without special replacement. Consider using 32# when it is very cold in the north in winter

Failure cause 3: The oil inlet pipe is seriously blocked by dirt

Troubleshooting method: Remove foreign matter in the pipe

Failure cause 4: The oil seal of the active gear of the oil pump is damaged, and air enters the hydraulic system

Troubleshooting method: Replace aging or damaged oil seals and O-rings

Failure cause 5: The "O" rings of the oil pump inlet and outlet joints or elbow joints are damaged, and the fastening screws of the elbow joints are The bolts or the nuts of the oil inlet and outlet pipes are not tightened, and air enters the hydraulic system

Troubleshooting method: Replace the O-ring and tighten the bolts or nuts at the joints

Failure cause 6:Internal leakage of the oil pump and aging of the seal ring

Troubleshooting method: Replace the seal ring

Failure cause 7:The end face of the oil pump or the end face of the main and driven gear sleeves are worn or scratched, and the unevenness of the end faces of the two sleeves exceeds the tolerance

Troubleshooting method: Replace the worn gear oil pump or oil pump sleeve, and grind the end face on a flat plate if the wear is slight. The tolerance is 0.03mm; the end face of the upper sleeve is lower than the pump body, and the upper plane (normal value is lower than 2.5~2.6mm). If the tolerance is exceeded, a 0.1~0.2mm copper sheet should be added to the lower sleeve to compensate. When installing, the sleeve should be installed on the rear sleeve.

Failure cause 8:Internal parts of the oil pump are incorrectly assembled, causing internal leakage

Troubleshooting method: The unloading plate and the sealing ring must be installed in the oil chamber so that the two sleeves can maintain balance. The elastic force of the guide wire should be able to simultaneously push the upper and lower sleeves toward the driven gear. The rotation direction of the wheel is twisted by a small angle to make the machining planes of the two shaft sleeves of the driving and driven gears fit closely; the unloading groove on the shaft sleeve must be installed on the side of the low-pressure chamber to eliminate the harmful dead volume generated when the gears are meshing; before pressing the self-tightening oil seal, a layer of lubricating oil should be applied to its surface, and it should be noted that the oil-blocking edge should face the front cover and cannot be installed reversely; before installing the pump cover, a small amount of hydraulic oil must be poured into the pump housing and the meshing gears must be turned by hand

Failure cause 9:Installing a "right-hand" oil pump on a "left-hand" machine will damage the skeleton oil seal

Troubleshooting method: A "right-hand" pump cannot be installed on a "left-hand" machine, otherwise it will damage the skeleton oil seal

Failure cause 10:The hydraulic oil is too dirty

Troubleshooting method: Clean the system and replace the hydraulic oil

There are certain skills in repairing the gear pump of a forklift. It cannot be disassembled blindly to cause damage to other parts. It should be disassembled in an orderly and reasonable manner according to the installation form and structural form of the gear pump. This will not only not damage the parts of the gear pump, but also quickly disassemble it.