1. Pressure reducing valve malfunction
① The pressure reducing valve fails. The main valve is blocked due to hydraulic oil contamination, the main valve is blocked, or the main valve is stuck or the cone valve is not in good contact with the seat and the spring is deformed.
② The spool is clamped radially. Caused by hydraulic oil pollution and manufacturing accuracy problems.
③ pressure pulsation. It is caused by problems such as unstable oil inlet (such as pressure pulsation from hydraulic pump) and air.
2. Sequence valve failure
① The sequence pressure does not match the set pressure. Improper adjustment of the pressure regulating spring; the spring deforms and the high pressure cannot go up; the slide valve is stuck; the valve body is installed in the wrong direction after disassembly and cleaning.
② Vibration and noise. The tubing is not suitable and the oil return resistance is too large.
3. Hydraulic check valve failure
① Noise. Resonance with other valves; oil flow exceeds allowable value.
②The seal is not good when it flows back. There is a gap between the valve core and the valve seat; the valve port is dirty; the valve port is worn.
③ Poor control. Control pressure is too low.
4. Excavator electromagnetic directional valve failure
① Cannot change direction. The system is contaminated; the flow rate exceeds the set value of the valve; electrical failure; the electromagnet is damaged or the suction force is insufficient; the spring force exceeds the electromagnetic suction force;
②The electromagnetic coil is overheated or burned out. The coil is poorly insulated; the solenoid core is not suitable; the coil is short-circuited; the voltage is too high.
③ AC solenoid valve noise. Mainly because of poor contact of the electromagnet.
④ Leakage. Sealing ring or protective ring is damaged; bolt connection is loose; solenoid valve is damaged.
5. Electro-hydraulic directional valve failure
①The spool cannot move. The valve core is damaged; the valve body is deformed; the control pressure is insufficient; the return spring is broken.
②The electromagnet burned out. Poor insulation; improper electromagnet core; voltage is too low; commutation pressure, flow rate and back pressure of the port are too high; push rod is too long or too short.
6. Multiple directional valve failure
① Pressure fluctuation and noise. The spring is bent and too soft; the damping hole of the overflow valve in the valve is blocked; the check valve is not closed tightly.
②The valve stem does not work well. The return spring is damaged.
③ Leakage. The cone valve is not in good contact with the valve seat; the studs are not tightened.
7. Pipeline failure
① Leakage is due to loose joints.
②The pipe is blocked, caused by debris, oxidative corrosion, etc.
③The pipe diameter becomes smaller.
④ Too many turns, the angle is too small.
8. Hydraulic oil pollution
Harm of hydraulic oil pollution:
① The solid particles in hydraulic oil, such as molding sand, cuttings, abrasives, welding slag, rust, paint, fiber, etc., are the most harmful, causing system performance deterioration, component wear, seal body damage, shortened life and even damage.
②Moisture mixed into hydraulic oil includes various chemical solvents, precipitates and surface active substances, etc., which will corrode the components and make the viscosity of hydraulic oil smaller, deteriorate, freeze, oil emulsification, etc.
③ mixed with air, causing system cavitation, cavitation, vibration, noise, bad response and crawling.
75% of system failures are caused by hydraulic oil pollution, so attention should be paid to the problem of hydraulic oil pollution.
9, hydraulic pump failure
① Pump noise.
②The pump does not discharge oil or the oil discharge is insufficient. Insufficient pump speed; insufficient oil absorption; air leakage at the suction port; clogged oil filter or suction pipe; low oil level; excessive oil viscosity causing poor oil absorption; too low oil viscosity causing internal leakage (internal leakage).
③ The pump pressure is insufficient and weak. The constant pressure of the relief valve is too low; other control elements and actuators leak; the pump has insufficient or no oil absorption; the leakage in the pump is serious; the vane pump blades are installed incorrectly.
④The pump temperature is too high. Improper design, assembly, adjustment and use, improper unloading of the system, excessively high flow velocity of the pipeline, and excessive pressure loss. The oil temperature is preferably 55 ° C, and the pump can be 65 bar.
⑤ Leak in the pump. Caused by parts processing (unloading slot position problem, groove depth problem, etc.), improper assembly (sealing or scratching), improper use (wrong installation of import and export), etc.
10, hydraulic motor failure
① The output torque of the hydraulic motor is insufficient, and the operation slows down. Caused by insufficient oil supply caused by pump failure.
②The internal leakage is large. Mainly related to working pressure difference, oil viscosity, hydraulic motor structure, displacement size and processing and assembly, especially at low speeds.
③External leakage (external leakage). Mainly caused by sealing and oil viscosity are too small.
④ crawling. Caused by uneven friction resistance, unsuitable oil viscosity, air ingress, contaminated hydraulic oil, and component wear.
⑤ The motor is emptied and hit. Mainly caused by insufficient back pressure.
⑥ Noise. Mechanical noise: caused by loosening or collision of bearings, couplings or other moving parts. Hydraulic noise: mainly due to pressure and flow pulsations, volume changes, cavitation and hydraulic shocks.
11, hydraulic cylinder failure
①Insufficient thrust or malfunction. Due to internal leakage, poor processing of the cylinder and assembly problems.
②Crawling. It is caused by air mixing, non-concentricity of piston rod and piston, bending of piston rod, rust or roughness of cylinder barrel (containing iron filings, etc.) and excessive gap between parts.
③ Shock and vibration. Caused by excessive buffer gap, excessively tight motion seal, and poor assembly of parts.
④ Leak. Due to poor sealing, strain and hydraulic oil viscosity problems.
12, overflow valve failure
① Pressure fluctuation. It is caused by the spring's rigidity or deformation, poor contact of the cone valve, inaccurate pressure gauge, insensitive movement of the spool valve and unclean hydraulic oil.
②Vibration and noise. Caused by spring deformation, air entry, excessive oil return resistance and excessive oil volume.
③ Oil leakage. Caused by poor contact or wear of the poppet valve and excessive clearance of the spool valve.
④The pressure cannot rise. Caused by spring breakage, spool locking, damping hole clogging, reverse connection of inlet and outlet, etc.
