Repair method for pump function of the hottest tru

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Repair method for pump function of truck crane

the 75 pump (ZB type, the same below) used by truck crane absorbs and compresses oil through 7 plungers constantly changing positions (linear movement) in the cylinder bore. When the plunger is seriously worn, the fit clearance between the plunger and the cylinder block hole will increase, and the hole diameter will become very irregular, which will reduce the pressure of the pump, reduce the efficiency, and even make it unusable. During the maintenance, it was found that many old 75 pumps could still be repaired. The repaired 75 pump can be reused for 2~3 years. The method of repair can be simplified. Generally, the mating parts of hydraulic components that cannot be moved up and down are interchangeable without poor CFRP thermal conductivity, but in practice, it is feasible for some pumps to redeploy the plunger for repair. As for the 75 pump, it is not easy to repair the inside of the cylinder block, while the plunger is easier to repair, so the function of the pump can be restored by repairing the plunger

there are three repair methods:

(1) look for the plunger with relatively small wear (7 in a group) in a number of used 75 pumps, then re pair and combine them according to the size of the plunger and the cylinder block, and finally grind them. During this process, use the outside micrometer and inside micrometer to accurately measure the outside diameter and ovality of the plunger, as well as the hole diameter and taper of the cylinder block for many times, so that the matching clearance between the selected plunger and the cylinder block hole can reach 0.02_ 0 4mm. The pump so selected and repaired can generally be used for more than 2 years

(2) when there is no redundant old pump, the part of the plunger outer diameter and the cylinder block hole diameter exceeding the original data will be covered in sequence for measurement, and then the parts with small fitting clearance and serious wear will be reassembled and paired respectively. The seriously worn plunger can be electroplated to reach the required size (if the coating is thick, it can be finely ground to the required size); After the plunger is matched with the cylinder block hole, mark it and then grind it one by one. Note: during electroplating, do not coat the inner ball surface of the sliding shoe at one end of the plunger. The plunger and cylinder block hole with small matching clearance and meeting the requirements can continue to be used

(3) when the plunger is seriously worn, especially for the plunger with hard scar on the surface, its part size can be measured and re machined. During turning, it is necessary to set aside grinding allowance and carry out tempering treatment. According to our experience, for expensive hydraulic components such as 75 pump, on the premise of not affecting the safety of the whole machine and the rapid development of the domestic building energy conservation industry to today's performance, it is necessary to spend less money and repair

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