Under normal use, the excavator break hammer will work for about three years, and there will be a reduction in work efficiency. This is because in the work, the external surface of the piston and cylinder body wear, so that the original gap increases, the high-pressure oil leakage increases, the pressure decreases, resulting in the impact energy of the excavator break hammer decreases, and the work efficiency is reduced.
In individual cases, due to improper use by the operator, the wear of the parts is accelerated. For example: the transitional wear of the upper and lower guide sleeve, the loss of guiding effect, the axis of the drill rod and the piston tilt, the piston in the work of hitting the drill rod, the external force received by the end face is not a vertical force, but a certain Angle of the external force and the center line of the piston, the force can be decomposed into an axial reaction and a radial force. The radial force causes the piston to deviate to one side of the cylinder block, the original gap disappears, the oil film is destroyed, and dry friction is formed, which accelerates the wear of the piston and the hole in the cylinder block, and the gap between the piston and the cylinder block is increased, resulting in increased leakage and the impact of the excavator break hammer is reduced.
The above two situations are the main reasons for the reduction of the efficiency of the excavator break hammer.
It is common practice to replace a set of pistons and oil seals, but simply replacing a new piston will not completely solve the problem. Because the cylinder has been worn, the inner diameter size has become larger, the inner diameter of the cylinder has increased the roundness and taper, the gap between the cylinder and the new piston has exceeded the design gap, so the efficiency of the breaking hammer can not be fully restored, not only that, but also because the new piston and the worn cylinder work together, because the cylinder has been worn, the external surface roughness has increased, which will accelerate the wear of the new piston. If the middle cylinder assembly is replaced, of course, it is the best result. However, the cylinder block of the excavator break hammer is the most expensive of all the parts, and the cost of replacing a new cylinder assembly is not cheap, while the cost of repairing a cylinder block is relatively low.
The cylinder of the excavator break hammer is carburized in the production, the high level of the carburizing layer is about 1.5~1.7mm, and the hardness after heat treatment is 60~62HRC. Repair is to re-grind, eliminate wear marks (including scratches), generally need to grind 0.6~0.8mm or so (side 0.3~0.4mm), the original hardened layer is still about 1mm, so after re-grinding the cylinder, the surface hardness is guaranteed, so the wear resistance of the inner surface of the cylinder and the new product is not much different, the wear of the cylinder is feasible to repair once.
After the cylinder is repaired, its size is bound to change. In order to ensure that the original design impact energy remains unchanged, it is necessary to redesign and calculate the front and back cavity area of the cylinder. On the one hand, it is necessary to ensure that the area ratio of the front and back cavity remains unchanged with the original design, and the area of the front and back cavity is also consistent with the original area, otherwise the flow rate will change. The result is that the flow of the excavator break hammer and the bearing machine are not matched reasonably, resulting in adverse consequences.
Therefore, a new piston should be prepared after the repaired cylinder block to fully restore the design gap, so that the working efficiency of the excavator break hammer can be restored.
Post time: Aug-23-2024