The failure of hydraulic wheeled cranes is divided into three categories: mechanical failure, electrical failure and hydraulic system failure.
- Crane hydraulic system
The crane is powered by hydraulic pressure, with a variety of hydraulic devices. Crane hydraulic system of common fault diagnosis and troubleshooting as follows:
① pressure does not rise
Check the hydraulic oil tank: whether the oil level is low (suction empty), whether the hydraulic oil is degraded or whether oil pollution, whether the oil temperature is too high, depending on the situation to replenish or replace the hydraulic oil. Check the hydraulic pump: whether the speed is normal, directly connect the relief valve and pressure gauge to the oil outlet to test the hydraulic oil pump, check whether the volumetric efficiency is reduced due to wear or damage of parts, and repair as appropriate. Check the relief valve: whether the setting pressure is reduced due to a loose adjusting screw, whether the valve seat surface is damaged or dusty, whether the valve is stuck in the open position, whether the needle valve is worn, whether the spring is deformed or damaged, adjust or repair as appropriate. Check the rotary joint: whether the seal is damaged, whether the sleeve and central shaft are damaged, repair or replace as appropriate. Check the pressure gauge: whether it is inaccurate.
②Hydraulic pump with abnormal noise
Check the hydraulic oil tank: whether the oil level is low (sucking empty), whether the hydraulic oil is deteriorated, too viscous or polluted, whether the oil temperature is too high, replenish or replace the hydraulic oil as appropriate. Check the hydraulic pump: whether the installation bolts are loose, whether the coupling, drive shaft, etc. are connected loosely, whether the internal parts are badly worn or damaged; whether the oil inlet pipeline inhales air, tighten or repair as appropriate.
③ Hydraulic pump overheating
Check the hydraulic oil tank: whether the oil level is low, whether the hydraulic oil is deteriorated or polluted, replenish or replace the hydraulic oil as appropriate. Check the hydraulic pump: whether the volumetric efficiency is reduced due to wear and tear, whether it is stuck due to wear and tear, repair or replace as appropriate.
When carrying out diagnosis and troubleshooting, the following must be observed in practice. Before operation, the tank level window should determine whether the hydraulic oil is sufficiently filled according to the regulations, and must be replenished if it is below the specified line. When refuelling, it must be injected through the refuelling filter and great care must be taken not to mix in impure substances such as different grades of oil or water. The oil filter element should be checked after 250h of work and cleaned or replaced if necessary. The hydraulic oil tank should be cleared of water and impurities every half month from the bottom oil discharge port, and all hydraulic oil should be replaced every year (or 2000h of work) (the oil change cycle can be extended if the oil has not deteriorated). When the crane is operating in a particularly harsh environment, the oil replacement cycle should be shortened accordingly. Various valves of the hydraulic system have been fully tested before leaving the factory and have been adjusted for pressure and flow, so they must not be touched casually. All kinds of machine parts, especially the hydraulic system devices, should not be attached to the dirt. After the operation, be sure to remove the dust, oil and dirt.
- Crane outrigger system
In order to increase the lifting capacity of the tyre crane when lifting, the crane is equipped with outriggers. The outriggers are required to be sturdy and reliable, easy to extend and retract, retracted when driving and outstretched to support the ground when working. The common faults of the crane outrigger system are: the outrigger moves slowly or does not move; the lift cylinder piston rod retracts when working; the outrigger extends when driving.
①Slow or immobile outrigger movement
Check whether the hydraulic system is faulty; check the relief valve: whether the adjustment pressure is lowered due to loose adjusting screws, whether the valve seat surface is damaged or dusty, whether the valve is stuck in the open position, whether the needle valve is worn, whether the spring is deformed or damaged, and adjust or repair as appropriate. Check the hand-operated valve: whether the valve stem is worn, whether the valve is damaged internally, replace as appropriate; check the outrigger cylinder: whether the piston is stuck, whether the piston rod is bent, replace as appropriate.
② lift cylinder piston rod retraction at work
Check the liquid-controlled check valve: whether the valve seat surface is damaged or dusty, whether the valve or piston is stuck in the open position, whether the spring is intact, whether the O-ring is intact, repair or replace as appropriate. Check the outrigger lift cylinder: whether the seal O-ring is damaged, whether the cylinder inner wall is scratched, replace or repair as appropriate.
③Extend the outrigger when driving
Check the manual control valve (for outrigger): whether the surface of the liquid control check valve seat is damaged or dusty, whether the liquid control check valve is stuck, whether the spring is damaged, repair or replace as appropriate; check the outrigger lift cylinder: whether the sealing O-ring is damaged or worn, whether the inner wall of the cylinder is scratched, repair as appropriate.
④ The following points should be noted during disassembly and overhaul
(1) Before overhaul, clean the outside of the legs (such as pipe joints, etc.); (2) The disassembled pipe joints must be wrapped with cloth to prevent impurities from falling in; (3) The piston, cylinder, etc. must be cleaned and blown dry; (4) Before assembly, the piston, cylinder, oil seal and other surfaces should be coated with hydraulic oil for lubrication; (5) When assembling, a protective ring should be placed on the piston to prevent the oil seal from being cut; (6) When installing the check valve (6) when installing the check valve, the tightening torque of the joints should not be too large, so as not to deform the main body of the valve, so that the spool and guide piston action failure; (7) because the hydraulic check valve has the performance of reverse controlled opening, playing a role in preventing the leg seat retraction insurance, so we should pay attention to the maintenance of the check valve.
- Crane slewing system
The reason why the crane can lift the weight to any space position within the specified working range, in addition to relying on the lifting mechanism to achieve vertical displacement of the weight, most must also rely on rotary movement to achieve horizontal displacement. The rotary motion has a limited horizontal movement range, requires little power and is relatively simple, so it is widely used in most construction cranes and is generally designed as a full rotary, i.e. in the left and right direction at will. Only in certain cranes is a full slewing mechanism or no slewing mechanism provided, and other mechanisms are used to adjust the space position. In the realisation of the slewing movement, the crane’s slewing part and the non-slewing part between the force transfer device called slewing support device, drive part of the central rotary joint called the slewing mechanism. The common failures of the crane slewing system are: slow or immobile movement, the turntable does not turn, the slewing system clearance is too large, etc.
①Slewing system action slow? Not moving
Check whether the hydraulic system is faulty; check the relief valve: whether due to loose adjusting screws, so that the adjusted pressure is reduced, whether the valve seat surface is damaged or dust, whether the valve is stuck in the open position, whether the needle valve is worn, whether the spring is deformed or damaged, as appropriate, to adjust or repair. Check the manual control valve: whether the valve stem is worn, whether the valve is damaged inside, repair as appropriate; check the rotary reducer, gear or worm gear, worm gear is damaged: replace or repair as appropriate; check the hydraulic motor: whether the plunger or bearing is stuck, whether it loses effectiveness due to severe wear, whether the output shaft is broken, repair or replace as appropriate.
②Turning table does not move
Check the hydraulic motor: whether the internal parts are worn, replace as appropriate.
③ rotary system clearance is too large
Check the rotary reducer worm wheel, drive gear: whether worn, replace as appropriate. Check the slewing support gear: whether worn, replace as appropriate.
- Crane luffing system
The common faults of the crane luffing system are: when the boom is raised or lowered, the boom luffing system moves slowly or does not move; there is irregular vibration.
① When the boom is raised, the luffing system moves slowly or does not move
Check whether the hydraulic system is faulty; check the relief valve: whether the adjustment pressure is reduced due to a loose adjusting screw, whether the surface of the valve seat is damaged or dusty; whether the valve is stuck in the open position, whether the needle valve is worn, whether the spring is deformed or damaged, adjust or repair as appropriate. Check manual control valves: whether the valve stem is worn, whether the valve is damaged internally, repair as appropriate. Check the swivel joint: whether the seal is damaged, whether the central shaft and sleeve are damaged, replace or repair as appropriate.
②The boom luffing system moves slowly or does not move when the boom is dropped
Check whether the hydraulic system is faulty; check the relief valve: whether the adjustment pressure is lowered due to a loose adjusting screw, whether the valve seat surface is damaged or dusty, whether the valve is stuck in the open position, whether the needle valve is worn, whether the spring is deformed or damaged, adjust or repair as appropriate; check the manual control valve: whether the valve stem is worn, whether the valve is damaged inside, repair as appropriate; check the luffing cylinder: whether the piston is stuck, whether the cylinder Check whether the inner wall of the cylinder is scratched, replace as appropriate; check the balancing valve: whether the guiding piston or check valve is out of order, repair or replace as appropriate; check the rotary joint: whether the seal is damaged, whether the central shaft and sleeve are damaged, replace or repair as appropriate.
Check whether the spring of the counterbalance valve is damaged and replace it as appropriate; the handle should not move too fast during operation.
- Crane lifting system
The common faults of crane hoisting system are: slow or no action of rope winding; slow or no action of rope releasing; vibration of rope releasing; load falling or falling by itself, etc.
①Rope roll action slow or no action
Check whether the hydraulic system is faulty; check the relief valve: whether the adjustment screw is loose so that the adjustment pressure is reduced, whether the valve seat surface is damaged or dusty, whether the valve is stuck in the open position, whether the needle valve is worn, whether the spring is deformed or damaged, adjust or repair as appropriate; check the manual control valve: whether the valve stem is worn, whether the valve is damaged inside, repair as appropriate. Check the counterbalance valve overload relief valve: whether the adjustment pressure drops due to a loose adjusting screw, whether the valve is stuck in the open position, whether the spring is damaged, adjust, repair or replace as appropriate. Check the hydraulic motor: whether it is broken, stuck and failed, whether the performance is reduced due to wear and tear of the parts, repair or replace as appropriate. Check whether the gear teeth of the lifting mechanism are broken, and replace them as appropriate; check whether the lifting brake is reasonably adjusted, and readjust it as appropriate. Check the rotary joint: whether the seal is damaged, whether the central shaft and sleeve are damaged, replace or repair as appropriate.
②Rope release action is slow or non-action
Check whether the hydraulic system is faulty; check the relief valve: whether the adjustment pressure is reduced due to loose adjusting screws, whether the valve seat surface is damaged or dusty, whether the valve is stuck in the open position, whether the needle valve is worn, whether the spring is deformed or damaged, adjust or repair as appropriate. Check manual control valves: whether the valve stem is worn, whether the valve is damaged internally, repair as appropriate. Check the hydraulic motor: whether it is broken, stuck and failed, whether the performance is reduced due to wear and tear of the parts, repair or replace as appropriate. Check whether the gear teeth of the lifting mechanism are broken, and replace them as appropriate. Check whether the lifting brake is poorly adjusted, readjust as appropriate; check the balance valve: whether it is out of order due to dust on the plunger or piston, blocked oil holes, etc., clean as appropriate; check the rotary joint: whether the seal is damaged, whether the central shaft and sleeve are damaged, replace or repair as appropriate.
③Vibration when releasing the rope
Check the balance valve: whether it is out of order due to dust on the plunger or piston, blocked oil hole, etc., clean as appropriate; whether there is air entering, exclude as appropriate.
④Load fall or fall down by itself
Check the hydraulic motor: whether the performance is reduced due to wear of parts, measure the oil leakage, repair or replace as appropriate; check the counterbalance valve: whether the performance is reduced due to plunger wear, dust on the surface, etc., whether the overload relief valve setting pressure is reduced, repair, replace or adjust as appropriate; check the lifting brake adjustment: whether it meets the regulations, readjust as appropriate.
- Crane telescopic system
The common faults of the crane telescopic system are: the boom extends slowly or does not extend; the boom retracts slowly or does not retract; the boom retracts when the control handle is in the middle position, etc.
①Sluggish or no extension of the boom
Check whether there is a fault in the hydraulic system (already described earlier); check the relief valve: whether the adjustment pressure is lowered due to a loose adjusting screw, whether the surface of the valve seat is damaged or dusty, whether the valve is stuck in the open position, whether the needle valve is worn, whether the spring is deformed or damaged, adjust or repair as appropriate; check the manual control valve: whether the valve stem is worn, whether the valve is damaged inside, repair as appropriate; check the boom: whether whether the sliding surface is well lubricated, whether the sliding plate is properly adjusted, replaced, greased and adjusted as appropriate; check the telescopic cylinder: whether the piston is stuck, whether the piston rod is bent, replaced as appropriate; check the rotary joint: whether the seal is damaged, whether the central shaft and sleeve are damaged, replaced or repaired as appropriate.
② boom retraction slow or not retracted
Check whether the hydraulic system is faulty; check the relief valve: whether the adjustment pressure is lowered due to a loose adjusting screw, whether the valve seat surface is damaged or dusty, whether the valve is stuck in the open position, whether the needle valve is worn, whether the spring is deformed or damaged, as appropriate? Check the manual control valve: whether the stem is worn, whether the valve is damaged inside, repair as appropriate; check the boom: whether it is bent, whether the sliding surface is well lubricated, whether the sliding plate is properly adjusted, adjust and lubricate as appropriate; check the telescopic cylinder: whether the piston is stuck, whether the piston rod is bent, replace as appropriate; check the balancing valve: whether the piston is stuck due to blocked flow holes or dust, causing it to work Check the balancing valve: whether the piston is blocked by the flow blocking hole or dust, resulting in poor operation. Check the swivel joint: whether the seal is damaged, whether the central shaft and sleeve are damaged, replace or repair as appropriate.
The boom retracts when the control handle is in the middle position.
Check the telescopic cylinder: whether the internal oil leakage is due to damage of the O-ring, whether the welding part is defective, replace and repair as appropriate.
If you are interested in any of the products mentioned in the article above, please send us an email totalsycn@gmail.com and we will look into your needs and provide a solution.
