290HC Mast Sectionsolve the problem of unloading failure of tower crane from two aspects of electric circuit and liquid circuit
1. Check the circuit
The purpose of circuit detection is to check whether the moment limiter and limit switch can also transmit the electrical signal to the unloading solenoid valve while providing the panel indicator alarm signal. If they can, the unloading circuit will be connected to realize the safe unloading, otherwise, the safe unloading will fail.
2. Inspection of liquid circuit
Check the liquid circuit, first check the pipe layout, no mistakes, and finally focus on the logic valve. It is suspected that the spring of the check valve in the logic valve is hard or the diameter in the valve is small, which makes the back pressure of the unloading oil circuit larger, resulting in the unblocked unloading oil circuit and the difficulty of unloading. Therefore, the pressure of an or BN port corresponding to the action is measured under the alarm state, and it is found that the pressure is about 1MPa, while the main valve only needs about 0.6MPa pilot pressure to open, which proves that the suspicion is correct. It is precisely because of the large back pressure in the logic valve that the unloading difficulty is caused.
