Analysis of the Causes of the Retraction of the Luffing Hydraulic Cylinder of a Truck Crane

When the TL 250 truck crane is performing lifting operations, the luffing hydraulic cylinder has a retraction phenomenon. There are generally two reasons for this kind of malfunction: one is leakage in the amplitude cylinder, and the other is oil leakage from the balance valve.

The method for diagnosing faults: Ignite the engine, attach the power take-off, extend the four outriggers, raise the boom at an Angle of about 50°, and shut down the engine when lifting a load of 7-8 tons about 1 meter off the ground. Pull the amplitude control lever back and forth several times to release the oil pressure. Use a wrench to disassemble the high-pressure hose joint from the amplitude control valve to the rod-free cavity of the amplitude cylinder. At this point, observe whether there is any hydraulic oil flowing out of the oil hole at the pipe joint fixed in the luffing cylinder. If the hydraulic oil flows out continuously and slowly, it is determined that the balance valve is leaking oil. If no hydraulic oil flows out, it is determined that there is internal leakage in the luffing cylinder.