Created on:2021-09-25 14:30

Lifting and transportation equipment_ Maintenance of truck crane_ Repair and inspection of directional valve

Lifting and transportation equipment_ Maintenance of truck crane_ Repair and inspection of directional valve

(1) Repair of reversing valve stem (slide valve) after wear

After the valve stem (slide valve) of the directional valve (especially) is worn, the fit clearance with the valve body hole increases, the sealing performance at the oil port decreases, the hydraulic system leaks internally, and the bearing capacity decreases (or shifts). If the internal leakage is serious, it will cause an accident. If only one or two valve discs of a multi-way directional valve are seriously worn, the valve discs were replaced after wear in the past. At present, there are more and more repairs. It is economical and technically feasible to repair it. When repairing, first clean the valve body hole and carry out accurate measurement; Then make the grinding mandrel according to the measured dimensions (see Figure g).

When grinding the valve body hole with the grinding mandrel, first fix the valve body and keep the valve body hole vertical, and then thread the reinforcement rod into the hinge shaft hole to lift the grinding mandrel. In the process of lifting, pay attention to the left and right rotation to grind the hole evenly as much as possible, focusing on restoring the roundness of the valve body hole. After grinding, accurately measure the hole, make a new valve rod according to the measured size, conduct quenching and tempering treatment, and finally finely grind and form. If the original valve rod can be used according to the measured hole size after the valve plate is repaired, use the original valve rod; If the valve rod becomes thinner, it can be repaired by electroplating. Before electroplating, the outer diameter of the original valve rod can be turned to 0.2mm. After electroplating, the valve rod can be ground according to the new size requirements.

(2) Detection of oil outlet sealing of directional valve

In the luffing mechanism and telescopic mechanism of truck crane, there are four factors affecting the sliding of heavy objects: the sealing ring at the piston is damaged and internal leakage; The sealing ring at the head of the hydraulic cylinder is damaged and there is oil leakage along the movable rod; The balance valve is not tightly sealed and has internal leakage; The valve rod of the directional valve is seriously worn, and the seal at the oil port connected with the actuator is not tight. A simple and convenient detection method is proposed for the reason of heavy weight drop caused by loose sealing of directional valve. Its working principle is shown in Figure H.

When it is suspected that the sealing of an oil outlet connected between the reversing valve and the hydraulic cylinder is not tight, the oil pipe of the other oil outlet connected between the reversing valve and the hydraulic cylinder (luffing cylinder or telescopic cylinder) can be removed and blocked; Put the reversing valve in the middle position after; Then connect and fasten according to the requirements of figure h, press the hand pump and bleed through the bleed screw; Finally, pressurize with a manual pump and observe whether the value of the pressure gauge can reach the standard pressure value of the system (the standard pressure of telescopic and luffing systems is 21MPa). If the pressure cannot be added or maintained after adding, and the pressurized hydraulic system does not leak oil, it can be concluded that there is a problem with the directional valve. Oil pipe 3 in Figure h is an oil circuit for measuring another oil outlet. The specific oil outlet date to be measured should be determined according to the actual situation. However, it should be noted that when this method is applied, the crane shall be unloaded; The jib must be in the low position; The directional valve must be kept in the neutral position; At the same time, do other safety work well.

Home    Article    Lifting and transportation equipment_ Maintenance of truck crane_ Repair and inspection of directional valve