The causes of noise generated by hydraulic forklifts are complex and diverse, mainly involving multiple aspects such as hydraulic systems, mechanical components, engines, and pipeline design. The following are specific reasons and analysis:

Reasons related to hydraulic system

Vacuum phenomenon: When air is mixed into the oil, it is easy to form air pockets in the high-pressure zone and propagate in the form of pressure waves, causing oil oscillation and resulting in cavitation noise in the system. This may be due to blockages in the oil filter and inlet pipe of the hydraulic pump, or high viscosity of the oil, causing excessive vacuum at the pump inlet and allowing air to seep in; It may also be due to damage to the oil seal at the shaft end of the hydraulic pump or pilot pump, or poor sealing of the inlet pipe, causing air to enter; It is also possible that the oil level in the tank is too low, causing the hydraulic pump's inlet pipe to be directly emptied.

Wear and tear of internal components of hydraulic pumps: such as the wear and tear of the cylinder body and distribution plate, plunger and plunger hole of the plunger pump, which causes serious leakage inside the hydraulic pump. When the hydraulic pump outputs high-pressure and low flow oil, flow pulsation will occur, causing high noise. In addition, the servo valve core of the hydraulic pump and the piston that controls the flow rate may also experience local wear and tear, causing pulsation of the piston during movement, resulting in fluctuations in the output flow rate and pressure of the hydraulic pump, thereby generating significant vibration and noise at the pump outlet.

Hydraulic pump distribution plate problem: During use, surface wear or oil sludge deposition on the distribution plate at the opening of the unloading groove can shorten the unloading groove and change the unloading position, resulting in trapped oil and causing high noise. During the normal repair process, the distribution plate repaired by flat grinding may also have the consequence of the unloading groove becoming shorter. If it is not appropriately elongated in a timely manner, it will also produce significant noise. During the assembly process, the large unloading groove of the distribution plate must be installed in the high-pressure chamber of the pump, and its sharp angle direction must be opposite to the rotation direction of the cylinder body, otherwise it will also bring significant noise to the system.

Overflow valve problem: Overflow valves are prone to high-frequency noise, mainly caused by unstable performance of the pilot valve, which is the noise generated by air vibration caused by high-frequency oscillation of the pressure in the front chamber of the pilot valve. This may be due to the presence of air in the oil, causing cavitation in the front chamber of the pilot valve and resulting in high-frequency noise; It is also possible that the needle valve is excessively worn due to frequent opening during use, causing the conical surface of the needle valve to not fit tightly with the valve seat, resulting in unstable pilot flow, pressure fluctuations, and noise; It is also possible that the pressure regulating function of the pilot valve is unstable due to spring fatigue deformation, causing large pressure fluctuations and noise.

Hydraulic cylinder problem: Air is mixed in the oil or the air in the hydraulic cylinder is not completely discharged, resulting in cavitation under high pressure and causing significant noise. In addition, if the cylinder head oil seal is too tight or the piston rod is bent, noise may also be generated during movement due to friction.

Reasons related to mechanical components

Bearing damage: Bearings are critical components responsible for rotational motion and are frequently used in forklift operations. Once damaged, they may cause abnormal noise.

Inappropriate clearance between the separation bearing and the lever: Prolonged rotation may cause the separation bearing to lack oil, leading to abnormal noise.

Damage to clutch friction plate: If the keyway of the clutch driven plate and the input part of the transmission are worn, it may also be one of the reasons for abnormal noise.

Loose or worn mechanical components, such as plastic parts in the engine compartment, belt tightness, and aging claw pads, can all cause the machine to make abnormal noises. In addition, the severe wear and large gaps of the vehicle's guide wheels and rollers, the excessive wear and clearance of the chain and chain pin shafts, the excessive clearance between the upper and lower locking nails of the fork and the crossbeam of the fork frame, and the excessive rolling clearance caused by the conflict between the guide wheels, rollers, and door frame are also factors that contribute to the loud noise produced by forklifts during use.

Engine related reasons

Fuel issues: Improper use of engine oil or dirty engine oil, or even insufficient fuel combustion, can lead to unstable engine idle and increased noise.

Engine damage: Improper driving operations, such as frequently stepping on the accelerator in low gears or revving at high speeds in low gears, can cause significant damage to the engine, affecting its ability to climb hills in the future and generating noise.

Loose screws: A loose screw in the engine or exhaust pipe may also cause the machine to make abnormal noises.

Reasons related to pipeline design

Pipeline vibration: When the oil pipe is slender and has many bends that are not fixed, it is easy to cause pipe vibration and noise during the process of oil flow, especially when the flow rate is high.

Unreasonable pipeline layout: The suction and return pipes are too close, the inlet pipeline is too thin, the filter is blocked or the oil flow capacity is weak, all of which may cause noise in the hydraulic system.

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