In the realm of heavy machinery operations, truck-mounted cranes play a crucial role. However, like any complex mechanical system, they are not immune to occasional malfunctions. During normal operation, truck-mounted cranes may sometimes seem to “get lazy” and take an unplanned break. At such times, we need to assume the role of a diligent doctor, meticulously diagnose the “cause” behind the truck-mounted crane‘s sluggishness and then prescribe the appropriate remedy to cure its “laziness.”
Generally, there are four main reasons for a truck-mounted crane to exhibit signs of being “lazy.”
Problems with the crane’s operation and power source:
The crane of a truck-mounted crane may appear “lazy” and reluctant to work, or it might “cut corners” by lacking strength and failing to meet the specified requirements. This issue often stems from problems with either the oil pump or the hydraulic oil tank.
If the oil pump refuses to function properly, the first step is to check whether the air pressure has reached the specified value. Additionally, verify whether the solenoid valve and the power take-off switch are energized. It is also essential to examine whether the air circuit of the power take-off is properly ventilated. In many cases, this problem occurs because the handle of the power take-off is not pushed in completely. At such times, simply pushing the handle of the power take-off into the correct position can often solve the issue.
If there is a problem with the internal gear of the power take-off box, it becomes necessary to inspect the transmission sleeve between the output shaft of the power take-off box and the input shaft of the oil pump. If the transmission sleeve is found to be faulty, it must be replaced promptly.
Another situation that may arise is when there is no problem with the oil pump itself, but the speed of the crane is unstable. This is mainly due to insufficient hydraulic oil or a clogged oil filter. In such cases, the solution is relatively straightforward – add hydraulic oil or clean the oil filter to restore proper functioning.
For example, imagine a truck-mounted crane on a construction site that suddenly starts to operate sluggishly. The operator notices that the crane’s lifting speed is much slower than usual, and it seems to lack the power it had before. By following the diagnostic steps, the operator first checks the air pressure. If the air pressure is within the specified range, they then move on to check the solenoid valve and power take-off switch. Suppose they find that the power take-off handle was not fully engaged. Once the handle is pushed in properly, the crane resumes normal operation.
On another occasion, if the crane’s speed remains unstable even after ensuring the power take-off is functioning correctly, checking the hydraulic oil level and the condition of the oil filter becomes crucial. If the oil level is low, adding hydraulic oil can often resolve the issue. If the oil filter is clogged, cleaning or replacing it can restore the crane’s performance.
Weakness in the luffing cylinder:
If the sealing ring of the luffing cylinder of a truck-mounted crane is damaged, it can cause an increase in internal leakage. This internal leakage can lead to a significant reduction in the performance of the luffing cylinder, making it appear weak. In such cases, the damaged seal and piston should be replaced without delay.
The deformation of the cylinder barrel of the luffing cylinder can also cause the luffing cylinder to lose power. Additionally, damage to the piston within the luffing cylinder can 同样 result in an increase in internal leakage and a subsequent loss of strength. When this occurs, it is necessary to replace the internal piston and address the deformation problem of the luffing cylinder.
For instance, during the operation of a truck-mounted crane, the operator notices that the luffing cylinder is not performing as expected. The boom fails to extend or retract smoothly, and there is a noticeable loss of power. Upon inspection, it is discovered that the sealing ring of the luffing cylinder is damaged. Replacing the damaged seal and piston restores the proper functioning of the luffing cylinder, allowing the crane to resume its normal operations.
If the cylinder barrel is found to be deformed, it may require specialized repair or replacement to ensure the luffing cylinder can operate effectively. This could involve machining the barrel to correct the deformation or replacing it entirely if the damage is too severe.
Issues with the hydraulic system pressure:
A problem with the hydraulic system, specifically insufficient pressure, can also cause the truck-mounted crane to appear “lazy.” This is mainly due to leakage within the hydraulic system or the pressure of the relief valve being adjusted too low.
When faced with this problem, it is essential to carefully inspect all pipelines and components to identify and take measures to stop the leakage. Leaks can occur at various points in the hydraulic system, such as at pipe connections, seals, or valves. Any detected leaks should be repaired promptly to prevent further loss of pressure and ensure the proper functioning of the crane.
In addition, checking the set pressure of the relief valve is crucial. If the relief valve has lost its pressure-regulating function, it needs to be repaired, and any damaged parts should be replaced. The relief valve plays a vital role in maintaining the proper pressure within the hydraulic system. If it malfunctions, it can lead to a significant drop in pressure, affecting the performance of the crane.
For example, suppose a truck-mounted crane is experiencing a significant reduction in lifting power. After a thorough inspection, it is determined that there is a leak in one of the hydraulic pipelines. Repairing the leak stops the loss of pressure and restores the crane’s lifting capacity.
If the relief valve is suspected to be the problem, adjusting its pressure setting or replacing it if necessary can resolve the issue. This requires a careful understanding of the crane’s hydraulic system and the proper procedures for adjusting and maintaining the relief valve.
Weakness in the winch:
If the volumetric efficiency of the winch plunger motor is reduced, it can cause the winch to appear weak. In such cases, the winch plunger oil and motor need to be replaced.
Another issue that may arise is that after the goods are lifted, they drop significantly. Careful observation may reveal that the luffing piston rod is pulled out, the movable boom and outriggers retract, and the lifting hook drops naturally. This can be caused by leakage in the luffing cylinder, telescopic cylinder, and outrigger cylinder. In such situations, the damaged seal and piston need to be replaced.
If the balance valve of the luffing cylinder and telescopic cylinder is damaged, it should be replaced or repaired. Similarly, if the two-way hydraulic lock at the outrigger is damaged, it also needs to be replaced or repaired.
In case the friction brake pad in the winch gearbox is damaged, simply replacing the friction brake pad and motor can resolve the problem.
For instance, during the operation of a truck-mounted crane, the winch fails to hold the load properly, and the goods start to drop unexpectedly. By carefully inspecting the various components, it is determined that there is a problem with the winch plunger motor. Replacing the motor and the plunger oil restores the winch’s ability to hold the load securely.
If there is leakage in the cylinders or damage to the balance valves or hydraulic locks, addressing these issues promptly is essential to ensure the safety and proper functioning of the crane.
In conclusion, truck-mounted cranes may exhibit “laziness” in these various aspects. However, by carefully identifying the “cause” and prescribing the right remedy, it is definitely possible to solve these problems. Regular maintenance, inspections, and prompt attention to any signs of trouble can go a long way in ensuring the reliable operation of truck-mounted cranes. This not only prolongs the lifespan of the equipment but also enhances safety and productivity on the job site.
