The so-called cylinder rod crawling is that after the excavator shuts down the engine, the cylinder rod will produce a certain displacement under this static state.
The crawling of excavator cylinder rod is common but annoying for excavator drivers; At the end of the work in the evening, the position of the large and small arms of the excavator did not stop well. Check it on the machine tomorrow morning. It was found that the position of the large and small arms sank, and it was felt that the machine was faulty.
In fact, when each excavator leaves the factory, there is a certain quantitative standard for this crawling index. It is best not to crawl in the ideal state, but it is difficult to achieve in the actual production and manufacturing process. Therefore, it is set with "standard upper and lower limits". Only when the "crawling amount" exceeds the upper and lower limits, can it be determined that the excavator has a fault.
Of course, all manufacturers have their own limit standards, which are different, that is, the large and small arms and bucket cylinder rods are also different. Only when the "crawling amount" exceeds the upper and lower limits, the excavator can be identified as faulty. What is the cause of the fault?
1. Check whether there is air in the cylinder
If air is mixed in the oil and sucked in from the hydraulic pump, the air inlet fault of the hydraulic pump can be eliminated first.
For new hydraulic cylinders, repaired hydraulic cylinders or hydraulic cylinders with long equipment shutdown time, there will be air in the cylinder and pipeline.
It can be vented through the vent plug of the hydraulic cylinder. For the hydraulic cylinder without special exhaust device, loosen the inlet and outlet pipe joints at both ends of the hydraulic cylinder and run back and forth for several times to exhaust the hydraulic cylinder. If the oil leaked from the joint changes from white to clear, it indicates that the air has been removed. At this time, the pipe joint can be tightened again. For hydraulic cylinders that are difficult to exhaust air by this method, the methods of loading exhaust and filling oil into the cylinder can be used to exhaust the air.
For the situation that negative pressure will be formed in the cylinder and air is easy to be sucked from the piston rod, pay attention to the rationality of the sealing design of the piston rod.
After startup, let the hydraulic cylinder run for 10min at the maximum stroke and speed to force the gas to be discharged.
2. Check whether the hydraulic cylinder is due to poor assembly accuracy
The assembly quality of hydraulic cylinder should be improved. If the piston rod and piston are not concentric, correct their coaxiality; Straighten the piston rod when the piston rod is bent. The matching between the piston rod and the guide sleeve shall be H8 / F8. The sealing ring qualified by the regular manufacturer shall be used in strict accordance with the size standard and quality standard. When the V-shaped sealing ring is used, the sealing friction shall be adjusted to a moderate degree.
3. Check whether the installation accuracy of hydraulic cylinder is poor
If the connection point between the load and the piston rod is as close as possible to the sliding surface of the guide rail; The axial line of piston rod shall be consistent with the load center line; The contact length with the guide rail shall be longer as far as possible; The connection position between the load and the hydraulic cylinder shall be subject to the fact that the thrust of the hydraulic cylinder does not tilt the load; Better guidance, better machining accuracy and assembly accuracy, and pay attention to lubrication.
4. Check whether the hydraulic cylinder end cover seal is pressed too tight or too loose
Adjust the sealing ring so that it is not tight or loose. The guide sleeve is concentric to ensure that the piston rod can move back and forth by hand or only tapping with a hammer, and a layer of oil film is hung on the piston rod.
5. Check whether the guide rail has poor manufacturing and assembly quality and poor lubrication
Measures can be taken to clean and dredge the guide rail lubrication device, readjust the lubrication pressure and lubrication flow, apply a layer of anti creep oil such as molybdenum disulfide lubricating oil between the relative moving surfaces of the guide rail, and scrape the guide rail again if necessary.
