There are many reasons for the slow lifting of the long arm of the excavator. Xiaobian gives our friends a detailed analysis and diagnosis of this fault, so that we can reduce the occurrence of faults as much as possible in the construction and make our construction go smoothly.
The main reasons for the slow or weak lifting of the excavator arm are as follows:
The reduction of the output power of the cylinder will make the boom lift slowly.
The reduced pressure difference between the two sides of the piston also causes the arm to lift slowly,
The reduction of the flow output of the hydraulic pump will inevitably cause the big arm to lift slowly!
The details are as follows:
1. Fault symptoms
Analysis: When the excavatoris working, it will be found that the big arm lifts slowly.
Ii. Reason analysis
The lifting of the big arm of the excavatordepends on the pressure oil output from the oil pump entering the back chamber of the big arm cylinder along the pipeline through the valve. The piston in the cylinder moves under the action of the working oil pressure and lifts the big arm through the piston rod.
From this point of view, the lifting speed of the big arm is related to the pressure and flow rate of the oil entering the cylinder. According to the principle that the power of the input cylinder is equal to the output power of the cylinder, and the power P of the input hydraulic cylinder is equal to the product of the working pressure of the hydraulic cylinder and the flow into the hydraulic cylinder, the slow lifting of the excavatorboom is mostly due to the reduction of the power of the input hydraulic cylinder, that is, the reduction of the power of the input cylinder. The reasons that cause the power of the input cylinder to decrease are:
01 Effects of oil pump
According to the piston moving speed in the cylinder is proportional to the working flow of the oil into the cylinder, if the flow output of the hydraulic pump is reduced, it will inevitably make the boom cylinder lift slowly. Further analysis, the actual flow of the oil pump is equal to the product of the theoretical flow of the oil pump and the total efficiency (the sum of the volumetric efficiency of the oil pump and the mechanical efficiency) If the total efficiency of the oil pump is reduced, the actual flow of the oil pump must also be reduced. The main reasons for the reduction of the total efficiency of the oil pump are: the increase of the leakage of the oil pump and the increase of the mechanical friction loss.
02 Cylinder effect
Hydraulic cylinder piston seal ring damage, cylinder strain, cylinder head seal ring damage caused by oil transiting or oil leakage, so that the volume efficiency in the cylinder is reduced, that is, the efficiency of the cylinder itself is reduced, so the output power is reduced, which is manifested as the boom lifting speed is slow.
03 Impact of oil leakage
The suction section of the oil pump (oil pump to oil tank) pipeline is badly sealed and draws air, affecting the pump oil efficiency; The oil leakage from the pressure range of the oil pump to the cylinder to the outside of the system or the leakage back to the tank through the control valve will reduce the oil flow into the cylinder and the pressure, resulting in slow lifting of the boom.
04 Impact of oil circuit blockage
The working oil of the hydraulic system generally has mechanical impurities, which are blocked in the parts with small oil carrying surface in the oil circuit, which reduces the flow of oil into the cylinder, and also causes the pressure to decrease. Therefore, the output power of the cylinder is reduced and the lifting of the big arm is slow.
The blockage of the filter screen at the oil suction port will increase the vacuum degree of the oil suction section of the oil pump. When the air pressure in the separated oil is reached, the air dissolved in the oil is separated and is inhaled by the oil pump, which affects the output power of the oil pump. According to the output power of the cylinder is equal to the input power of the oil pump, the big arm of the excavatoris slow to lift due to the reduction of the power of the cylinder.
The blockage of the oil filter net or radiator in the oil return circuit will increase the back pressure of the cylinder, resulting in a small pressure difference between the two sides of the cylinder piston. According to the proportional relationship between the piston moving speed of the cylinder and the pressure on both sides of the piston, when the pressure difference on both sides of the piston is reduced, the excavatorarm will lift slowly.
05 valve effects
The safety valve (overload valve or relief valve) setting pressure is too low or the valve is not tightly closed, will cause the working oil pressure in the system to drop, according to the Basque pressure everywhere equal theorem, so the pressure in the cylinder is also reduced, so the cylinder due to low pressure and slow lifting speed.
The same is true of a check valve that closes loosely due to mechanical impurities or poorly sealed valves and seats.
The gap between the spool of the reversing valve and the mating pair is too large, resulting in some pressure oil flowing back to the tank when working, and the result is the same as the above situation.
Iii. Diagnosis and exclusion
If the hydraulic working device is slow, it indicates that the fault of the slow lifting of the boom cylinder is in the main oil supply or the total oil return part. If the working speed of other working devices is normal, only the boom cylinder lifts slowly, it indicates that the failure of lifting weakness is in the boom branch.
01 Appearance check the leakage outside the main oil circuit. If there is an oil trace outside the system in the main oil circuit, it indicates that the fault lies in the inability of the big arm to lift. The cause of the oil leak should be identified along with the oil trace and removed.
02 Check the oil liquid in the tank. If the oil is seriously insufficient or there are too many bubbles, it is due to the slow lifting of the big arm caused by the insufficient pressure of the main oil circuit. The oil should be filled to make the liquid level meet the height requirements. If there are too many bubbles, it may be that the oil circuit and the gas circuit at the rotating joint are connected, and the sealing ring of the rotating joint should be replaced. If the oil oxidizes and deteriorates into black brown and emits a foul smell, it indicates that the oil deteriorates and should be replaced.
03 Check the oil temperature. If the system oil temperature exceeds 80 ° C, it indicates that it is the cause of slow lifting of the big arm and should be cooled. If the fault disappears after cooling, it proves that the radiator has poor heat dissipation or the continuous working time of the large load is too long.
In addition, if the oil temperature is low, the lifting speed of the big arm is slow when the oil temperature is high, indicating that the oil quality is bad or the hydraulic components of the system are worn, so that the system efficiency is reduced. The former mostly occurs in the use period. The latter occurs mostly in the wear out period.
04 Check the main safety valve. If the adjusting stud of the safety valve is screwed in (the pressure change is 2.352MPa per turn), the pressure rises to the specified value, and the lifting speed of the big arm is normal, it is caused by improper main safety adjustment.
If the adjustment is ineffective, it indicates that the spool of the main safety valve is stuck in the open position or is not strictly closed, and should be removed for inspection and elimination. If the pressure regulator spring breaks, it should be replaced.
05 When adjusting the main safety valve, the pressure regulator stud does not increase (23.52MPa) per turn, indicating that the oil pump is faulty. If the slow lifting failure of the excavator arm occurs in the early stage (closing period), it proves that there is air leakage in the oil suction passage; If it occurs in the wear period, it is proved that the oil pump is seriously worn and the pump oil efficiency is low, and it should be repaired or replaced.
06 Check the cylinder, if the control valve is in the middle after the cylinder is lifted, the big arm has obvious automatic drop, it may be the cylinder seal is poor, the cylinder safety valve is not tightly closed, the oil pipe oil leakage control valve oil leakage, should then identify the cause and eliminate the symptoms.
If the cylinder lift is slow in the early stage, most of the seals are likely to be damaged when assembling the cylinder. It is also possible that the mechanical impurities (metal chips, sand, etc.) at the time of assembly are not removed during manufacturing, and the valve spool or check valve is stuck in the open position to affect the closing of the valve spool; The pipe joint connection is loose and the sealing ring is damaged and leaking oil. The above reasons can cause the pressure in the hydraulic system to drop, resulting in slow lifting of the excavator arm, and the reasons should be further identified and eliminated.
If the relief valve pressure of the boom cylinder is lower than the specified value, it should be adjusted. The method is: screw out the plug and increase the pressure in the spring pad (for every 1mm thicker gasket, the pressure can be increased by 2.45MPa). Bucket cylinder failure phenomenon, cause analysis, diagnosis and elimination method.
Choose BONOVO for high-quality, customizable brush cutters for skid steers with fast delivery. Contact us today to discover how our superior products can enhance your land management tasks!
for more info just visit our website at www.bonovogroup.com
contact # : +86 158 6218 2088
email : sales@bonovogroup.com
×
- Home Thunder God
-
It is currently Jan 23rd, '25, 16:11
All times are UTC-05:00 - Delete cookies
- Contact us