The 75 pump (type ZB) used in truck cranes absorbs and compresses the oil by continuously changing positions (rectilinear motion) of the seven pistons in the cylinder bore. When the plunger wear serious, its cylinder bore with the gap will increase, and the aperture becomes very irregular, so that the pump pressure drop, reduce efficiency, or even can not be used. Found in the repair, many of the old 75 pump can still be repaired. After the repair of 75 pumps, generally can reuse 2 to 3 years. Repair method can be avoided. Under normal circumstances, the hydraulic components with the coupling is not interchangeable, but in practice some of the pump to re-deploy the plunger repair is feasible. In the case of a 75 pump, the interior of the cylinder is also not easy to repair, while the plunger is better, so the function of the pump can be restored by repairing the plunger. There are three ways to repair it: (1) Look for the less worn plungers (7 in a group) on multiple used 75 pumps, and then re-pair them according to the size of the ram and cylinder and finally grind. In this process, with the outer diameter micrometer and the inner diameter dial gauge accurate measurement of the outer diameter of the plunger size and ovality, as well as the cylinder bore diameter, taper, so that the selected plunger and cylinder bore with the clearance To 0.02_0.4mm requirements. This optional repair pump generally can be used for more than 2 years. (2) When there is no extra old pump, the plunger outer diameter and the bore hole diameter can be measured, and then with the small gap and wear more serious re-pairing. Serious wear of the plunger can be electroplated to achieve the required size (if the coating thickness, can be refined to the required size); the plunger and the cylinder hole, mark, one by one research and development. Note: When electroplating, the plunger on the surface of a ball inside the slide should not be plated. With small clearance and meet the requirements of the plunger and cylinder bore can continue to use. (3) When the plunger wear serious, especially on the surface of the hard scars of the plunger, can measure the size of the Department and re-car a few. Car system, we should pay attention to allow the grinding margin, but also for quenching and tempering, more hemp According to our experience, like 75 pump this more expensive hydraulic components, without affecting the safety of the premise Under, take less money, repair without updating the method, you can also achieve the purpose of normal use.