1. Common failure analysis and elimination method of hydraulic pump
Failure analysis:
1. The motor turns incorrectly.
2. Suction pipe or filter clogged
3. The axial clearance or radial clearance is too large.
4. Leakage at the connection, mixing with air.
5. Medium viscosity is too high or temperature rise is too high.

Method of exclusion:
1. Check the motor steering.
2. Dredge the pipeline, clean the filter, and replace with new working medium.
3. Check and replace the relevant parts.
4. Tighten the screws at each connection to avoid leakage and prevent air from entering.
5. Select the working medium correctly and control the temperature rise.
Failure analysis:
1. The oil suction pipe and filter are clogged or the filter capacity is small.
2. Air leakage at the seal of the suction pipe or bubbles in the medium.
3. The pump and the coupling are not concentric.
4. Low oil level.
5. Low oil temperature or high viscosity.
6. The pump bearing is damaged.

Method of exclusion:
1. Clean the filter to make the oil suction pipe unblocked, and select the filter correctly.
2. Add some oil to the connection parts or seals. If the noise is reduced, you can tighten the joints or replace the sealing ring. the oil return pipe port should be below the oil surface and a certain distance from the oil suction pipe.
3. Adjust concentricity.
4. Refueling fluid.
5. Heat the oil to an appropriate temperature.
6. Check (hand touch) the temperature rise of the pump bearing part.
Failure analysis:
The hydraulic resistance of the oil leakage pipeline is too large, so that the pressure in the pump body rises to exceed the pressure value used by the oil seal.

Method of exclusion:
Check whether the drain port on the pump body of the plunger pump is directly connected to the oil tank with a separate oil pipe. If it is found that the leaking oil pipes of several plunger pumps can be connected in parallel to a common pipe of the same diameter and then connected to the oil tank, or the drain pipe of the plunger pump is connected to the oil return pipe, it should be corrected. It is best to connect a pressure gauge to the pump leakage port to check the pressure in the pump body, its value should be less than 0.08Mpa.
2. Failure Analysis and Removal Method of Overflow Valve
Failure analysis:
1. The spring is bent or too soft.
2. Poor valve and valve seat have poor contact.
3. Poor adhesion between the steel ball and the valve seat.
4. Deformed or roughened spool.
5. Oil is not clean, damping hole is blocked.

Method of exclusion:
1. Replace the spring.
2. If the poppet valve is new, remove the adjusting nut and push the guide rod a few times to make good contact; or replace the poppet valve.
3. Check the roundness of the steel ball, replace the steel ball, and grind the valve seat.
4. Replace or repair spool valve.
5. Dredge the orifice and replace the cleaning fluid.
Failure analysis:
1. The spring is broken or missing.
2. Damping holes blocked.
3. Spool stuck.
4. The oil inlet and outlet are reversed.
5. Leaky installation of cone valve.

Method of exclusion:
1. Check, replace or replace the spring.
2. Dredge the orifice.
3. Disassembly, inspection and repair.
4. Check the oil source direction.
5. Check and reinstall.
Failure analysis:
1. Poor valve or steel ball has poor contact with the valve seat.
2. The clearance between the spool valve and the valve body is too large.
3. The pipe joint is not tightened.
4. Seal damage.

Method of exclusion:
1. Replace the new cone valve or steel ball when the cone valve or steel ball wears.
2. Check the gap between the valve core and the valve body.
3. Tighten the connection screws.
4. Check and replace the seal.
Failure analysis:
1. Loose nut.
2. The spring is deformed and does not recover.
3. The spool valve is too tight.
4. Poor operation of the main spool.
5. Cone valve wear.
6. There is air in the oil outlet.
7. The flow exceeds the allowable value.
8. Resonate with other valves.

Method of exclusion:
1. Tighten the nut.
2. Check and replace the spring.
3. Repair the slide valve to make it flexible.
4. Check the concentricity of the slide valve and the housing.
5. Change cone valve.
3. Failure Analysis and Elimination Method of Pressure Reducing Valve
Failure analysis:
1. Air is mixed into the oil.
2. Damping holes are sometimes blocked.
3. The roundness of the hole in the spool valve and the valve body exceeds the specification, causing the valve to jam.
4. The spring is deformed or stuck in the slide valve, making the slide valve difficult to move or the spring is too soft.
5. The steel ball is not round, the steel ball is not well matched with the valve seat or the cone valve is not installed correctly.

Method of exclusion:
1. Eliminate air in oil.
2. Clean the damping hole.
3. Repair valve hole and slide valve.
4. Replace the spring.
5. Replace the steel ball or disassemble the cone valve to adjust.
Failure analysis:
1. External leakage.
2. Poor valve and valve seat have poor contact.

Method of exclusion:
1. Replace seals and tighten screws, and ensure uniform torque.
2. Repair or replace.
Failure analysis:
1. The oil drain port is impassable; the oil drain pipe is connected to the oil return pipe and has oil return pressure.
2. The main spool is stuck when in the fully open position.

Method of exclusion:
1. The oil drain pipe must be separated from the oil return pipe and returned to the oil tank separately.
2. Repair and replace parts, check oil quality.
4. Failure Analysis and elimination method of throttle valve
Failure analysis:
1. The gap between the throttle valve and the hole is too large, there is leakage and internal leakage of the system.
2. The orifice is blocked or the valve core is stuck.

Method of exclusion:
1. Check the damage of the parts in the leakage site, repair and update, pay attention to the oil seal at the joint.
2. Disassemble and clean, replace with new oil to make the valve core move flexibly.
Failure analysis:
1. The impurities in the oil adhere to the side of the throttle, the cross section of the oil is reduced, which slows down the speed.
2. The performance of the throttle valve is poor, and the adjustment position changes due to vibration during low-speed movement.
3. Internal and external leakage of the throttle valve.
4. In the simple throttle valve, the speed changes suddenly due to the change of the system load.
5. As the oil temperature increases, the viscosity of the oil decreases and the speed gradually increases.
6. The damping device is blocked, there is air in the system, and the pressure changes and jumps.

Method of exclusion:
1. Disassemble and clean related parts, replace with new oil, and keep the oil clean.
2. Add throttle interlock device.
3. Check the precision and fit clearance of parts, repair or replace out-of-tolerance parts, and the connection should be tightly closed.
4. Check the function of the system pressure and pressure relief device and the control of the relief valve is normal.
5. Adjust the throttle valve or increase the oil temperature radiator after the hydraulic system is stable.
6. Clean the parts, add an exhaust valve in the system, and keep the oil clean.
5. Failure analysis and elimination method of directional valve
Failure analysis:
1. The spool is stuck.
2. Valve body deformation.
3. The centering spring with an intermediate position is broken.
4. The operating pressure is not enough.
5. The electromagnet coil is burnt out or the electromagnet has insufficient thrust.
6. The electrical circuit is out of order.
7. The hydraulic circuit of the hydraulic control valve is free of oil or blocked.

Method of exclusion:
1. Disassemble and clean the dirt and deburr.
2. Adjust the mounting screws of the valve body to make the pressure tight, the force is even, or repair the valve hole.
3. Replace the spring.
4. The operating pressure must be greater than 0.35Mpa.
5. Inspection, repair and replacement.
6. Eliminate faults.
7. Check the cause and eliminate.
Failure analysis:
1. The slide valve is stuck or the friction is too large.
2. The electromagnet cannot be pressed to the end.
3. The contact surface of the electromagnet core is uneven or bad.

Method of exclusion:
1. Repair or adjust spool valve.
2. Correct the height of the electromagnet.
3. Eliminate dirt and correct the electromagnet core.
6. Failure analysis and elimination method of hydraulic control check valve
Failure analysis:
1. Control pressure is too low.
2. Serious oil leakage at the control tubing joint.
3. Check valve stuck.

Method of exclusion:
1. Raise the control pressure to achieve the required value.
2. Tighten the joint to eliminate oil leakage.
3. Cleaning.
Failure analysis:
1. The check valve is stuck in the fully open position.
2. Non-uniform contact between the cone surface of the one-way valve and the cone surface of the valve seat.

Method of exclusion:
1. Repair and cleaning.
2. Maintenance or replacement.
7. Failure Analysis and Elimination of Excessive Oil Temperature
Failure analysis:
Poor operation of the unloading circuit.

Method of exclusion:
Check the electrical circuit, solenoid valve, pilot circuit and unloading valve for normal operation.
Failure analysis:
1. The valve size is too small, the energy loss is too large.
2. When the pump is selected, the flow of the pump is too large.

Method of exclusion:
1. According to the working pressure of the system and the maximum flow through the valve.
2. Reasonable pump selection.
Failure analysis:
1. Cooling water supply failure or fan failure.
2. There is precipitation in the cooling water pipe.

Method of exclusion:
1. Eliminate the fault.
2. Eliminate precipitation.
Failure analysis:
The cooling area of ​​the fuel tank is insufficient.

Method of exclusion:
Refit cooling system or increase fuel tank capacity and heat dissipation area.
Failure analysis:
1. Power loss due to wear.
2. Work with oil with too low or too high viscosity.

Method of exclusion:
1. Repair or replace.
2. Select the oil suitable for the viscosity of this system.
Failure analysis:
The liquid level in the tank is too low.

Method of exclusion:
Fill the oil to the recommended position.
Failure analysis:
The inner diameter of the pipe does not match the required flow rate or the inner diameter of the valve is not large enough.

Method of exclusion:
Install suitable size pipes and valves, or reduce power.
8. Common failure analysis and elimination methods of hydraulic cylinders
Failure analysis:
1. Air intrusion.
2. The sealing ring of the hydraulic cylinder end cover is too tight or too loose.
3. The piston rod is not concentric with the piston.
4. Full length or partial bending of the piston rod.
5. The installation position of the hydraulic cylinder is offset.
6. The linearity of the inner hole of the hydraulic cylinder is poor (drum taper, etc.).
7. Corrosion and roughening in the cylinder.
8. The nuts on both ends of the double piston rod are tightened too tightly, making them poorly concentric.

Method of exclusion:
1. Add an exhaust device; if there is no exhaust device, the hydraulic system can be activated to move the working parts quickly at the maximum stroke to force the air to be removed..
2. Adjust the sealing ring so that it is not tight or loose, and ensure that the piston rod can be pulled back and forth by hand without leakage (mostly a small amount of oil leakage is allowed).
3. Correct the concentricity of the two.
4. Straighten the piston rod.
5. Check and correct the parallelism of the hydraulic cylinder and the guide rail..
6. Boring and grinding repair, re-matching piston.
7. Minor repairs rust and burrs, severe ones must be boring.
8. The nut should not be tightened too tightly, generally tighten it by hand to keep the piston rod in a natural state.
Failure analysis:
1. The gap between the piston and hydraulic cylinder sealed by the gap is too large, and the throttle valve loses the throttling.
2. The one-way valve with buffer at the end fails, the buffer does not work.

Method of exclusion:
1. Equip the gap between the piston and the hydraulic cylinder as required to reduce leakage.
2. Amend the research and distribution check valve and valve seat.
Failure analysis:
1. The clearance between the hydraulic cylinder and the piston is too large or the O-ring seal is damaged, causing the high and low pressure chambers to communicate.
2. Due to the fact that a certain section of the working stroke is often used during work, the linearity of the hydraulic cylinder aperture is poor (partially with a waist drum shape), resulting in the communication of high and low pressure oil at both ends of the hydraulic cylinder.
3. The oil seal at the cylinder end is too tight or the piston rod is bent, which increases the friction or resistance.
4. Excessive leakage.
5. The oil temperature is too high, the viscosity is reduced, and the running speed of the oil cylinder by intermittent sealing or poor sealing quality becomes slow. If the high and low pressure oil chambers at both ends of the hydraulic cylinder communicate with each other, the running speed gradually slows down until it stops.

Method of exclusion:
1. Intermittent or replacement of O-ring seals with a single piston and hydraulic cylinder.
2. Boring and repairing hydraulic cylinder aperture, single piston.
3. Loosen the oil seal and straighten the piston rod with no oil leakage as the limit.
4. Look for leaks and tighten the joint surfaces.
5. Analyze the causes of heat generation, try to dissipate heat and reduce the temperature.