The main reasons for the unstable operation of the hydraulic cylinder of marine cranes
The main reasons for the unstable operation of the hydraulic cylinder of marine cranes
1. The interior of the hydraulic cylinder is sluggish.
Improper assembly of internal parts of the hydraulic cylinder, deformation, wear of parts or over-limit of shape and position tolerances, excessive action resistance, causing the piston speed of the hydraulic cylinder to change with different stroke positions, resulting in slippage or crawling. The main reasons are poor assembly quality of the parts, surface scratches or iron filings produced by sintering, which increase resistance and reduce speed. For example: The piston and the piston rod are not concentric or the piston rod is bent, the hydraulic cylinder or the piston rod is offset from the installation position of the guide rail, the sealing ring is installed too tightly or too loosely, etc. The solution is to repair or adjust it again, replace the damaged parts and clean the iron filings.
2. The quality of the seal is directly related to slippage or crawling.
When O-rings are used at low pressure, compared with U-rings, due to the relatively high surface pressure and the large difference in dynamic and static frictional resistance, they are prone to slippage or crawling. The surface pressure of the U-shaped sealing ring increases with the rise of pressure. Although the sealing effect also improves accordingly, the difference in dynamic and static frictional resistance becomes larger, the internal pressure increases, and it affects the elasticity of the rubber. Due to the increased contact resistance of the lip, the sealing ring will tip over and the lip will stretch, and it is also easy to cause sliding or crawling. To prevent it from tipping over, a support ring can be used to keep it stable.
3. Poor lubrication or out-of-tolerance processing of the hole diameter of the hydraulic cylinder.
Because there is relative motion between the piston and the cylinder barrel, the guide rail and the piston rod, etc., if the lubrication is poor or the bore diameter of the hydraulic cylinder exceeds the tolerance, it will accelerate the wear and reduce the straightness of the centerline of the cylinder barrel. In this way, when the piston works in the hydraulic cylinder, the frictional resistance will fluctuate, causing slippage or crawling. The solution is to first grind the hydraulic cylinder, then assemble the piston as per the matching requirements, grind the piston rod, and configure the guide sleeve.
4. Air enters the hydraulic pump or hydraulic cylinder of the ship crane.
Air compression or expansion can cause the piston to slip or crawl. The troubleshooting measures are to inspect the hydraulic pump, set up a good exhaust device, and quickly operate the full stroke back and forth several times for exhaust.
Maintenance of the hydraulic system of ship cranes
1. The ship crane should be oiled and replaced in accordance with the regulations in the hydraulic oil lubrication table, and the interior of the oil tank should be cleaned.
2. After the pressure of the relief valve of the ship crane is adjusted, it should not be changed at will. Before each climb, the pressure should be checked with an oil pressure gauge to ensure it is normal.
3. The ship crane should be frequently inspected to ensure that all pipe joints are firm and tight, and there should be no oil leakage.
4. When starting the ship crane in winter, it should be started and stopped several times back and forth. Only when the oil temperature rises and the control valve operates flexibly can it be put into formal use.
5. If leakage is found in the oil pump, cylinder and control valve of the ship crane, timely maintenance should be carried out.
6. When starting the oil pump for the first time after the installation and major overhaul of the ship crane, it is necessary to first check whether the inlet and outlet are connected in reverse and whether the rotation direction is correct. Check if there is any air leakage in the oil suction pipeline, then test it by hand, and then start and test it within the specified speed range.
7. The oil filter of the ship crane should be frequently inspected for any blockage, and the adjustment value of the control valve should be checked for any changes after use.
Burrs are a common phenomenon, but do we have to replace them every time burrs occur?
In fact, it's not like that. Minor burrs don't need to be replaced. Once the area of dry burrs exceeds 5%, it should be replaced in time to prevent breakage. When we use it, we should pay attention to protecting the steel wire rope well. After use, apply grease for maintenance to increase lubrication. Also, do small maintenance every day and major maintenance every week. Under such circumstances, The service life of the steel wire rope of the small boat crane will be very long.
When burrs are seen, it is necessary to replace them in time. Because once burrs occur, the steel wire rope will become thinner. When it becomes thinner, the load capacity will also decrease. Originally, when lifting 1 ton of goods, if the steel wire rope becomes thinner, the load capacity may increase to 900 kilograms. If it is lifted around 1 ton, it may break, causing the heavy object to fall and pose a danger.
When not lifting goods, the lower hook of the crane also needs to be hung with weighing items. If they are too light, it will cause disordered arrangement and mutual entanglement when the hook is retracted.
Common faults of ship cranes and their troubleshooting methods
1. The system overheats and makes excessive noise
Reason: Air is mixed into the hydraulic system, sometimes due to mechanical wear.
Solution: Release air from the oil pump's inlet and outlet, and replace it after maintenance.
2. Oil leakage at the front cover and end of the hydraulic motor
Cause: The sealing ring is damaged, and the oil seal of the output shaft is damaged.
3. Pressure Fluctuations
Cause: System blockage. The oil level is low, air is mixed in, and mechanical wear is severe.
Solution: Clean the oil circuit, add sufficient hydraulic oil, and carry out maintenance and replacement.
