The truck-mounted crane is a specialized vehicle type that plays an essential role in various fields of engineering construction. From municipal environmental sanitation and garden construction to high-speed rail construction, it has become an indispensable tool. Its light operation and excellent flexibility make it highly favored by users and a reliable helper for many people in their pursuit of making money. However, like any mechanical equipment, during the usage of truck-mounted cranes, various problems are bound to occur. Sometimes, it can be a challenging task to determine which part has malfunctioned, which not only wastes time but also potentially delays the construction period. Let me now briefly discuss the common faults that generally occur in truck-mounted cranes, along with their causes and treatment methods.
Phenomenon: Truck-mounted crane does not work.
Analysis of causes:
Oil pump does not work:
The power take-off handle is not pushed in place. This is a relatively common oversight. When the power take-off handle is not fully engaged, it cannot transfer power from the vehicle’s engine to the oil pump, resulting in the oil pump not functioning.
The gears in the power take-off box are damaged. Over time, due to continuous use and wear, the gears in the power take-off box can become damaged. This can lead to a failure in transmitting power to the oil pump.
The transmission sleeve between the output shaft of the power take-off box and the input shaft of the oil pump is damaged. The transmission sleeve is crucial for connecting the power take-off box and the oil pump. If it is damaged, power cannot be effectively transferred, causing the oil pump to stop working.
The oil pump is burned out. Various factors such as overheating, lack of lubrication, or prolonged heavy load operation can cause the oil pump to burn out and cease functioning.
Treatment methods:
For the issue of the power take-off handle not being pushed in place, the solution is straightforward. The operator should ensure that the power take-off handle is fully pushed in to establish the proper connection and transfer of power.
If the gears in the power take-off box are damaged, a thorough overhaul of the power take-off box is necessary. This may involve disassembling the box, inspecting the gears for damage, and replacing any damaged gears. Professional mechanics may be required for this task to ensure proper repair and reassembly.
When the transmission sleeve is damaged, it needs to be replaced. The new transmission sleeve should be of high quality and compatible with the output shaft of the power take-off box and the input shaft of the oil pump to ensure smooth power transmission.
In case the oil pump is burned out, it must be replaced with a new one. It is important to choose an oil pump that is suitable for the specific model of the truck-mounted crane and meets the required specifications to ensure proper functioning.
For example, imagine a truck-mounted crane on a construction site suddenly stops working. After inspection, it is found that the power take-off handle was not pushed in properly. By simply correcting this oversight and fully engaging the handle, the oil pump starts working again, and the crane can resume its operations. However, if the problem is due to damaged gears in the power take-off box or a burned-out oil pump, more extensive repair work and potentially a replacement of parts are required, which can cause significant downtime and inconvenience.
Phenomenon: Oil pump works but there is no pressure oil.
Analysis of causes:
Insufficient oil in the fuel tank. This can occur due to leaks in the system, improper filling during maintenance, or a failure to check and top up the oil level regularly. When there is not enough oil in the tank, the oil pump cannot draw in sufficient oil to generate pressure.
The oil filter is blocked. Over time, dirt, debris, and contaminants can accumulate in the oil filter, blocking it and preventing the flow of oil. This restricts the oil supply to the system and results in no pressure oil.
Treatment methods:
If the problem is insufficient oil in the fuel tank, the solution is to add sufficient hydraulic oil. It is important to use the correct type and grade of hydraulic oil as specified by the manufacturer to ensure proper functioning of the system. Regularly checking and maintaining the oil level is also crucial to prevent this issue from recurring.
When the oil filter is blocked, it needs to be cleaned. In some cases, if the blockage is severe or the filter is damaged, it may need to be replaced. Regular maintenance and replacement of the oil filter at recommended intervals can help prevent this problem from occurring.
For instance, suppose a truck-mounted crane is experiencing a lack of pressure oil. After inspection, it is found that the fuel tank is low on oil. By adding the appropriate amount of hydraulic oil, the system can resume normal operation. However, if the issue is a blocked oil filter, cleaning or replacing the filter can restore the proper flow of oil and pressure.
Phenomenon: The lifting capacity of the truck-mounted crane is reduced and obviously cannot meet the requirements.
Analysis of causes:
The pressure of the hydraulic system is too low. This can be caused by several factors:
There is a leak in the system. Leaks can occur in various parts of the hydraulic system, such as pipelines, fittings, cylinders, or valves. These leaks result in a loss of pressure and a reduction in the lifting capacity.
The pressure of the relief valve is adjusted too low. If the relief valve is set at a pressure that is too low, it will limit the maximum pressure in the system and reduce the lifting capacity.
The volumetric efficiency of the oil pump is reduced. Over time, due to wear and tear, the oil pump may lose its efficiency and not be able to deliver the required volume of oil, resulting in a lower pressure and reduced lifting capacity.
Treatment methods:
For a leak in the system, it is necessary to check all pipelines and components carefully to identify the source of the leak. Once the leak is located, appropriate measures should be taken to stop the leak. This may involve tightening fittings, replacing damaged seals or pipes, or repairing damaged components.
If the pressure of the relief valve is adjusted too low, it should be checked and adjusted according to the regulations. However, over-adjustment should be avoided as it can lead to other problems. If the relief valve has lost its pressure-regulating function, it needs to be overhauled, and any damaged parts should be replaced.
When the volumetric efficiency of the oil pump is reduced, the oil pump should be replaced. Choosing a high-quality replacement oil pump that meets the specifications of the truck-mounted crane is essential to restore the lifting capacity.
For example, if a truck-mounted crane is struggling to lift heavy loads and it is determined that there is a leak in the hydraulic system, a comprehensive inspection is required. Once the leak is found and repaired, the lifting capacity can be restored. Similarly, if the relief valve is set too low or the oil pump is inefficient, appropriate adjustments or replacements can solve the problem.
Phenomenon: Luffing cylinder is weak.
Analysis of causes:
The sealing ring in the luffing cylinder is damaged, resulting in increased internal leakage. Over time, the sealing rings in the cylinder can wear out or become damaged due to factors such as pressure, friction, and exposure to contaminants. This allows hydraulic oil to leak internally, reducing the effectiveness of the cylinder and making it weak.
The piston in the luffing cylinder is damaged or the cylinder of the luffing cylinder is deformed, resulting in large internal leakage. Damage to the piston or deformation of the cylinder can occur due to excessive force, impact, or improper use. This can cause significant internal leakage and weaken the cylinder’s performance.
Treatment methods:
If the sealing ring is damaged, the sealing parts and piston should be replaced. New high-quality sealing rings and pistons should be installed to ensure a tight seal and proper functioning of the cylinder.
In case the cylinder is deformed or the piston is severely damaged, it is necessary to check the cylinder carefully. If the deformation is minor, it may be possible to repair it. However, if the damage is extensive, the cylinder may need to be replaced.
For instance, if the luffing cylinder of a truck-mounted crane is weak, inspection may reveal damaged sealing rings or a deformed cylinder. By replacing the sealing parts and piston or repairing/replacing the cylinder as needed, the cylinder’s performance can be restored.
Phenomenon: Telescopic cylinder is weak.
Analysis of causes: Same as the luffing cylinder.
Treatment methods: Same as the luffing cylinder.
Phenomenon: Winch is weak.
Analysis of causes: The volumetric efficiency of the winch plunger oil motor is reduced. Similar to the oil pump, over time, the winch oil motor can experience wear and tear, resulting in a reduction in its volumetric efficiency. This leads to a decrease in the power output of the winch and makes it weak.
Treatment methods: Replace the oil motor. A new oil motor that is compatible with the winch and meets the required specifications should be installed to restore the winch’s strength.
For example, if the winch on a truck-mounted crane is struggling to lift or lower loads, it may be due to a reduced volumetric efficiency of the oil motor. Replacing the oil motor can solve this problem and ensure the winch operates effectively.
Phenomenon: After the goods are lifted, they obviously drop naturally (more than 2 millimeters/second). It can be clearly seen that the luffing piston rod is pulled out, the movable boom and outriggers have obvious retraction phenomena, and the lifting hook has a natural drop phenomenon.
Analysis of causes:
There is internal leakage in the luffing cylinder, telescopic cylinder, and outrigger cylinder. Similar to the previous cases of weak cylinders, internal leakage in these cylinders can cause the lifted goods to drop.
The balance valve of the luffing cylinder and telescopic cylinder is damaged. The balance valve is designed to maintain pressure and prevent sudden drops. If it is damaged, it cannot perform its function properly, resulting in the goods dropping.
The two-way hydraulic lock at the outrigger is damaged. The hydraulic lock is supposed to keep the outriggers in position. If it is damaged, the outriggers can retract, causing instability and potentially leading to the dropping of the goods.
The volumetric efficiency of the winch motor is reduced, and the friction brake pads in the winch gearbox are damaged. As mentioned earlier, a reduced volumetric efficiency of the winch motor can weaken the winch’s ability to hold the load. Additionally, damaged friction brake pads can also contribute to the natural drop of the goods.
Treatment methods:
For internal leakage in the cylinders, see the treatment method for cylinder internal leakage as mentioned earlier.
If the balance valve is damaged, it should be replaced or overhauled. This may involve disassembling the valve, inspecting for damage, and replacing any faulty parts.
When the two-way hydraulic lock is damaged, it should be replaced or overhauled. Similar to the balance valve, proper inspection and repair or replacement are necessary to ensure its proper functioning.
For a reduced volumetric efficiency of the winch motor and damaged friction brake pads, the friction brake pads should be replaced, and if necessary, the motor may also need to be replaced.
For example, if after lifting goods, they start to drop naturally, a comprehensive inspection is required to determine the source of the problem. It could be due to internal leakage in the cylinders, damaged balance valves or hydraulic locks, or issues with the winch motor and brake pads. By addressing these problems through appropriate repairs or replacements, the safety and reliability of the truck-mounted crane can be restored.
The above table clearly shows the common faults and causes of truck-mounted cranes, as well as the treatment methods, for your reference. While we may hope that our beloved vehicle will not encounter problems, it is essential to master these skills to be prepared for emergencies. Regular maintenance, proper operation, and timely detection and repair of faults can help ensure the smooth and safe operation of truck-mounted cranes, minimizing downtime and maximizing productivity.
