Troubleshooting methods for the slow steering fault of excavators

A WY4-60 excavator often experiences a problem of slow steering of the front wheels when making sharp turns during operation. According to the working principle of the steering system, it can be determined that this fault is caused by the decline in the volumetric efficiency of the hydraulic steering system and the excessively low system pressure. The main cause of its occurrence is severe leakage both inside and outside the hydraulic system. Generally, the following methods can be adopted for inspection and elimination.

(1) Check whether there is any leakage on the outside of the hydraulic steering system.

The main symptoms of external oil leakage are: significant loss of hydraulic oil, decreased system pressure, unstable movement of the steering cylinder and motor, resulting in slow and weak steering, and even no steering at all. The main causes of external leakage are: improper fit of oil pipe joints, poor sealing and pipeline rupture. Improper fit, wear, aging or damage of seals; The oil temperature is too high, thereby increasing leakage. When external oil leakage is detected, timely maintenance should be carried out.

(2) Check the hydraulic oil

The quality and quantity of hydraulic oil will directly affect the working condition of the steering system. If there is too little hydraulic oil, the hydraulic pump will suffer from insufficient oil supply, causing the machine's steering action to be slow. Therefore, the hydraulic oil should be added to the specified liquid level. When the hydraulic oil is not clean or there are foreign objects in the oil tank, impurities entering the hydraulic system can cause damage to the seals or damage to the mating pairs of components, increase internal leakage, and thus lead to slow steering. For this reason, a careful inspection of the quality of the hydraulic oil is necessary. If impurities are found in the oil, the hydraulic oil should be replaced in time and the entire hydraulic system should be cleaned.

(3) Check whether air has entered the hydraulic steering system

Even a small amount of air entering the hydraulic system can have a significant impact on it, causing the steering cylinder to crawl, reducing the efficiency of the hydraulic system, and thus leading to slow steering. The ways for air to enter the hydraulic system are: the joint of the suction pipe of the steering pump is loose or the pipe is cracked. Poor sealing of the steering pump; The oil level in the fuel tank is too low, causing the suction pipe or return pipe to be exposed above the liquid surface. The quality of the hydraulic oil is poor. The inspection method is as follows: Start the engine and turn the steering wheel to observe the fuel tank. If bubbles come out of the fuel tank, it indicates that air has entered the hydraulic system. At this point, it is necessary to identify the cause and eliminate it.

(4) Check the steering cylinder

When the sealing parts between the piston and the cylinder barrel in the steering cylinder are worn or damaged, the internal leakage will increase, causing the steering cylinder to move slowly. The method of inspection is as follows: Remove the steering cylinder and install it on another excavator with normal steering for testing. If the steering is good after installation, it indicates that there is no problem with the steering cylinder. If the steering is still slow after the gear change, it indicates that the problem lies in the seal of the steering cylinder. At this point, the steering cylinder should be disassembled for inspection to check the damage condition of the piston and seals, as well as whether the cylinder barrel has been scratched, etc., and then repaired.

(5) Check the steering pump

If there is severe internal leakage in the steering pump, it can also cause the machine to turn slowly. One important cause of leakage inside the steering pump is that the gap between the side of the rotor and blades and the end face of the side plate is too large (the normal gap should be within 0.047mm, and the maximum should not exceed 0.100mm). The inspection method is as follows: When the performance of the steering cylinder, central rotary joint and steering gear is all in good condition, install a new pump for comparative tests. If the steering performance is good after the replacement, it indicates that the fault lies in the steering pump and a new pump should be replaced.

(6) Check the central rotary joint

When the inner cylindrical surface or sealing ring at the central rotary joint of the excavator is severely worn, it will cause the entire oil and gas system passing through the rotary joint to communicate with each other at the seal failure point, resulting in the operation of each system of the rotary joint being insensitive. When the machine turns, high-pressure oil leaks into the air line or other hydraulic pipelines (such as suspension, outriggers, etc.), thereby reducing the amount of hydraulic oil supplied to the steering cylinder and causing the steering cylinder to move slowly. The inspection method is as follows: Pull the manual air switch of the wheel brake upwards. If the gas sprayed out from the inside contains oil mist, it indicates that the central rotary joint has been severely worn, causing oil to leak into the air passage. At this point, the sealing ring of the central rotary joint must be replaced and the central rotary joint repaired.

(7) Check the steering gear motor

When the working surfaces of the stator and rotor of the steering motor or the working surface of the rotary valve are severely worn, the actual amount of high-pressure oil entering the steering cylinder will decrease, resulting in slow steering action. If the performance of the steering cylinder and the central rotary joint is good, the steering wheel can be turned to the extreme after the engine is turned off. If the front wheels of the machine can immediately deflected and do not feel heavy at this time, it indicates that there is a problem with the steering gear, and it should be repaired or replaced immediately.

(8) Check the single-path steady flow valve

When the oil pressure of the hydraulic steering system is too low due to the weakened spring force of the single-way flow stabilizing valve, it will cause the steering cylinder to work weakly, resulting in slow steering. For this, the nylon plug at the remote control port of the single-way steady flow valve base can be removed and a pressure gauge can be installed. Then start the engine, turn the steering wheel to the left or right in place, and set obstacles on the side of the front wheels. At this point, observe the reading of the pressure gauge. If the pressure does not reach 7Mpa, the adjusting screw of the single-way steady flow valve should be appropriately pushed in (the fixing nut needs to be loosened first), and the fault will be eliminated.