The failures of hydraulic wheeled cranes can be divided into mechanical failures, electrical failures and hydraulic system failures.
1. Crane hydraulic system
The crane is powered by hydraulic pressure and equipped with various hydraulic devices. Common fault diagnosis and troubleshooting of crane hydraulic system are as follows:
① Pressure does not rise
Check the hydraulic oil tank: whether the oil level is low (suction), whether the hydraulic oil is deteriorated or contaminated, and whether the oil temperature is too high. Supplement or replace the hydraulic oil as appropriate. Check the hydraulic pump: whether the rotation speed is normal, directly connect the overflow valve and pressure gauge to the oil outlet to test the hydraulic pump, check whether its volumetric efficiency is reduced due to wear or damage of parts, and repair as appropriate. Check the overflow valve: whether the set pressure is reduced due to the loosening of the 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, and whether the spring is deformed or damaged. Adjust or repair as appropriate. Check the swivel: whether the seal ring is damaged, whether the sleeve and central shaft are damaged, and repair or replace them as appropriate. Check whether the pressure gauge is inaccurate.
② Abnormal noise of hydraulic pump
Check the hydraulic oil tank: whether the oil level is low (suction), whether the hydraulic oil is deteriorated, too viscous or polluted, and whether the oil temperature is too high. Supplement or replace the hydraulic oil as appropriate. Check the hydraulic pump: whether the mounting bolts are loose, whether the coupling and drive shaft are loosely connected, and whether the internal parts are seriously worn or damaged; Check whether the oil inlet pipe absorbs air, and tighten or repair it as appropriate.
③ Hydraulic pump overheating
Check the hydraulic oil tank: whether the oil level is low, whether the hydraulic oil is deteriorated or contaminated, and supplement or replace the hydraulic oil as appropriate. Check the hydraulic pump: whether the volumetric efficiency is reduced due to wear, and whether it is stuck due to wear. Repair or replace it as appropriate.
The following items must be observed during diagnosis and troubleshooting. Before operation, the liquid level window of the oil tank shall be used to determine whether the hydraulic oil is filled up as required. If it is below the specified mark, it must be supplemented. When refueling, be sure to inject through the refueling filter screen, and pay great attention not to mix with impure substances such as oil or water of different brands. The filter element of the oil filter shall be checked after 250h of operation, and cleaned or replaced if necessary. The water and impurities in the hydraulic oil tank shall be removed from the bottom oil drain every half month, and all hydraulic oil shall be replaced every other year (or after 2000h of operation) (the oil change period can be appropriately extended if the oil does not deteriorate). When the crane is operating in a particularly harsh environment, the oil replacement cycle should be shortened accordingly. All valves of the hydraulic system have been fully tested before delivery, and the pressure and flow have been adjusted. Do not touch them casually. All kinds of machine parts, especially the devices of the hydraulic system, must not be attached with dirt. After operation, the dust and oil stain must be removed.
2. Crane outrigger system
In order to increase the lifting capacity of the rubber tyred crane during lifting, the crane is equipped with outriggers. The outriggers shall be firm, reliable, flexible, retractable when driving, and extended to support the ground when working. Common faults of crane outrigger system include: outrigger moves slowly or does not move; The piston rod of lifting cylinder retracts during operation; Outriggers stretch out when driving.
① The outrigger moves slowly or does not move
Check whether the hydraulic system is faulty; Check the overflow valve: whether the set pressure is reduced due to the loosening of the 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, and whether the spring is deformed or damaged. Adjust or repair as appropriate. Check the hand operated valve: check whether the valve stem is worn and whether the valve interior is damaged, and replace it as appropriate; Check the outrigger oil cylinder: whether the piston is stuck and whether the piston rod is bent, and replace it as appropriate.
② The piston rod of lifting cylinder retracts during operation
Check the hydraulic control 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 in good condition, and whether the O-ring is in good condition. Repair or replace it as appropriate. Check the outrigger lifting oil cylinder: whether the sealing O-ring is damaged, whether the inner wall of the oil cylinder is scratched, and replace or repair it as appropriate.
③ Outrigger extension during driving
Check the manual control valve (for the outrigger): whether the valve seat surface of the hydraulic control check valve is damaged or dusty, whether the hydraulic control check valve is stuck, and whether the spring is damaged. Repair or replace it as appropriate; Check the outrigger lifting oil cylinder: whether the seal O-ring is damaged or worn, whether the inner wall of the oil cylinder is scratched, and repair as appropriate.
④ Pay attention to the following points during disassembly and overhaul
⑴ Before maintenance, clean the outside of the outrigger (such as pipe joints); ⑵ All disassembled pipe joints must be wrapped with cloth to prevent impurities from falling into; ⑶ The piston and cylinder barrel must be cleaned and dried; ⑷ Before assembly, the piston, cylinder barrel, oil seal and other surfaces shall be coated with hydraulic oil for lubrication; ⑸ During assembly, a protective ring shall be sleeved on the piston to prevent the oil seal from being damaged; (6) When installing the check valve, the tightening torque of each joint should not be too large to avoid deformation of the valve body and failure of the valve core and guide piston; (7) As the hydraulic control check valve has the performance of reverse controllable opening, which plays a role of insurance against the retraction of the outrigger seat, attention should be paid to the maintenance of the check valve.
3. Crane slewing system
The reason why the crane can send the lifting object to any spatial position within the specified working range, in addition to relying on the lifting mechanism to achieve the vertical displacement of the object, most must also rely on the rotary motion to achieve the horizontal displacement. The horizontal movement range of slewing motion is limited, the power required is small, and the requirements are relatively simple, so it is widely used in most construction cranes, and it is generally designed to be full slewing type, which can rotate in the left and right directions at will. Only on a specific crane can a full rotary rotary mechanism be set or no rotary mechanism be set, and other mechanisms are used to adjust the spatial position. When the slewing movement is realized, the power transmission device between the slewing part and the non slewing part of the crane is called the slewing bearing device, and the central rotary joint of the driving part is called the slewing mechanism. The common faults of the slewing system of the crane are: slow action or immobility, the turntable immobility, excessive clearance of the slewing system, etc.
① Swing system moves slowly? Immobile
Check whether the hydraulic system is faulty; Check the overflow valve: whether the set pressure is reduced due to the loosening of the 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, and whether the spring is deformed or damaged. Adjust or repair as appropriate. Check the manual control valve: check whether the valve rod is worn and whether the valve interior is damaged, and repair as appropriate; Check whether the rotary reducer, gear or worm gear and worm are damaged: replace or repair as appropriate; Check the hydraulic motor: whether the plunger or bearing is stuck, whether it is ineffective due to serious wear, whether the output shaft is broken, and repair or replace it as appropriate.
② The turntable can not rotate
Check the hydraulic motor for wear of internal parts, and replace as appropriate.
③ Excessive clearance of slewing system
Check the worm gear and drive gear of the slewing reducer for wear and replace them as appropriate. Check the slewing ring gear for wear and replace it as appropriate.
4. Crane luffing system
Common faults of crane luffing system include: boom lifting or boom lowering, and boom luffing system moves slowly or does not move; There is irregular vibration.
① Boom luffing system moves slowly or does not move during boom lifting
Check whether the hydraulic system is faulty; Check the overflow valve: whether the setting pressure is reduced due to the loosening of the adjusting screw, and whether the valve seat surface is damaged or dusty; Check whether the valve is stuck in the open position, whether the needle valve is worn, and whether the spring is deformed or damaged. Adjust or repair as appropriate. Check the manual control valve: check whether the valve stem is worn and whether the valve interior is damaged, and repair as appropriate. Check the swivel: whether the seal ring is damaged, whether the central shaft and sleeve are damaged, and replace or repair them as appropriate.
② The boom luffing system acts slowly or does not move when lowering the boom
Check whether the hydraulic system is faulty; Check the overflow valve: whether the set pressure is reduced due to the loosening of the 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, and adjust or repair as appropriate; Check the manual control valve: check whether the valve rod is worn and whether the valve interior is damaged, and repair as appropriate; Check the luffing oil cylinder: whether the piston is stuck and whether the inner wall of the cylinder barrel is scratched, and replace it as appropriate; Check the balance valve: if the guide piston or check valve is out of order, repair or replace it as appropriate; Check the swivel: whether the seal ring is damaged, whether the central shaft and sleeve are damaged, and replace or repair them as appropriate.
③ Check whether the balance valve spring is damaged and replace it as appropriate; The handle shall not move too fast during operation.
5. Crane hoisting system
Common faults of crane hoisting system include: rope winding moves slowly or does not move; The rope is released slowly or not; There is vibration during rope laying; The load falls or falls by itself.
① Rope winding is slow or does not work
Check whether the hydraulic system is faulty; Check the overflow valve: whether the set pressure is reduced due to the loosening of the 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, and adjust or repair as appropriate; Check the manual control valve: check whether the valve stem is worn and whether the valve interior is damaged, and repair as appropriate. Check the overload overflow valve of the balance valve: whether the set pressure drops due to loosening of the adjusting screw, whether the valve is stuck in the open position, and whether the spring is damaged. Adjust, repair or replace it as appropriate. Check the hydraulic motor to see if it is broken or stuck, and if its performance is degraded due to wear of parts. Repair or replace it as appropriate. Check whether the gear teeth of the lifting mechanism are broken, and replace them as appropriate; Check whether the hoisting brake adjustment is reasonable, and readjust it as appropriate. Check the swivel: whether the seal ring is damaged, whether the central shaft and sleeve are damaged, and replace or repair them as appropriate.
② The rope is released slowly or not
Check whether the hydraulic system is faulty; Check the overflow valve: whether the set pressure is reduced due to the loosening of the 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, and whether the spring is deformed or damaged. Adjust or repair as appropriate. Check the manual control valve: check whether the valve stem is worn and whether the valve interior is damaged, and repair as appropriate. Check the hydraulic motor to see if it is broken or stuck, and if its performance is degraded due to wear of parts. Repair or replace it as appropriate. Check whether the gear teeth of the lifting mechanism are broken, and replace them as appropriate. Check whether the hoisting brake is poorly adjusted and readjust it as appropriate; Check the balance valve: whether it fails due to dust on the plunger or piston, blockage of oil hole, etc., and clean it as appropriate; Check the swivel: whether the seal ring is damaged, whether the central shaft and sleeve are damaged, and replace or repair them as appropriate.
③ There is vibration during rope laying
Check the balance valve: whether it fails due to dust on the plunger or piston, blockage of oil hole, etc., and clean it as appropriate; Whether there is air entering shall be eliminated as appropriate.
④ The load falls or falls by itself
Check the hydraulic motor: whether the performance is degraded due to wear of parts, measure the oil leakage, and repair or replace it as appropriate; Check the balance valve: whether its performance is reduced due to plunger wear, dust on the surface and other reasons, and whether the setting pressure of the overload overflow valve is reduced. Repair, replace or adjust as appropriate; Check the adjustment of the lifting brake: whether it meets the requirements, and readjust it as appropriate.
6. Crane telescopic system
Common faults of crane telescopic system include: 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.
① The boom extends slowly or does not extend
Check whether the hydraulic generating system has any fault (as described previously); Check the overflow valve: whether the set pressure is reduced due to the loosening of the 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, and adjust or repair as appropriate; Check the manual control valve: check whether the valve rod is worn and whether the valve interior is damaged, and repair as appropriate; Check the boom for bending; Check whether the sliding surface is well lubricated and whether the sliding plate is properly adjusted. Replace, grease and adjust as appropriate; Check the telescopic oil cylinder: if the piston is stuck and the piston rod is bent, replace it as appropriate; Check the swivel: whether the seal ring is damaged, whether the central shaft and sleeve are damaged, and replace or repair them as appropriate.
② The boom retracts slowly or does not retract
Check whether the hydraulic generating system has faults; Check the overflow valve: whether the set pressure is reduced due to the loosening of the 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, and whether the spring is deformed or damaged? Adjust or repair; Check the manual control valve: check whether the valve rod is worn and whether the valve interior is damaged, and repair as appropriate; Check the boom: whether there is bending, whether the sliding surface is well lubricated, whether the sliding plate is properly adjusted, and adjust and lubricate as appropriate; Check the telescopic oil cylinder: if the piston is stuck and the piston rod is bent, replace it as appropriate; Check the balance valve: whether the piston is blocked by the choke hole or blocked by dust, resulting in poor operation, and clean it as appropriate. Check the swivel: whether the seal ring is damaged, whether the central shaft and sleeve are damaged, and replace or repair them as appropriate.
③ The boom retracts when the control handle is in the middle position
Check the telescopic oil cylinder: whether the O-ring is damaged, causing internal oil leakage, and whether the welding part is defective. Replace and repair as appropriate.
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2023-01-29