Analysis of the Reasons for the Retraction of the Boom Hydraulic Cylinder of an Automobile Crane

When the TL 250 truck crane was performing lifting operations, the luffing hydraulic cylinder retracted. There are generally two reasons for this kind of failure: one is internal leakage of the luffing cylinder, and the other is oil leakage from the balance valve. Method to determine the fault: ignite the engine, hang up the power take-off, extend 4 legs, the boom elevation angle is about 50°, and the engine stalls when the 7-8t load is lifted about 1 lm from the ground. Pull the luffing lever back and forth several times to remove the oil pressure, and use a wrench to disassemble the high-pressure hose joint from the luffing control valve to the rodless cavity of the luffing cylinder. At this time, observe whether there is hydraulic oil flowing out of the oil hole of the pipe joint fixed on the luffing cylinder. If the hydraulic oil flows out continuously and slowly, it is determined that the balance valve is leaking; if there is no hydraulic oil flowing out, it is determined that the luffing cylinder is leaking.