Crushing hammer can not strike the internal cause – piston hair

There are many factors causing the crushing hammer to be weak, such as insufficient nitrogen pressure, insufficient accumulator pressure and insufficient oil pressure, but the main cause of internal leakage is the piston or cylinder hair pulling.

The main causes of piston hair pulling are described below.

Piston as the core zero accessories of the crushing hammer, the role is extraordinary, but, along with the import piston longitudinal strain caused by more disputes, therefore, the author summarized some experience, analyzed the causes of piston hair, hoping to give the majority of users some tips.

活塞 (2)

(1) The hydraulic oil is not clean

If the oil is mixed with impurities, these impurities wedge into the gap between the piston and the cylinder block, can cause strain. This strain has the following characteristics: generally, there are trenches deeper than 0.1mm, a small number, its length is about equal to the stroke of the piston.

(2) The clearance between the piston and the cylinder is too small

This situation often occurs when replacing the new piston. If the clearance is too small, the clearance of the hydraulic breaker changes with the increase of the oil temperature in the work, then the piston and the cylinder block are easy to cause strain. Its characteristics are: the depth of the tear is shallow, the area is large, its length is about equal to the stroke of the piston.

(3) Low hardness of piston and cylinder

Piston in the movement of external force, because of the piston and cylinder surface hardness is low, easy to produce strain phenomenon. It is characterized by shallow depth and large area.

(4) the rod guide sleeve failure

The guide sleeve is poorly lubricated or due to the poor wear resistance of the guide sleeve, accelerate the wear of the guide sleeve, the gap between the rod and the guide sleeve sometimes reaches more than 10mm, then the center line of the rod is easy to skew, when the piston movement to the tail of the rod, the reaction force of the piston is a partial force, a component of the force is formed on the radial force of the piston, The piston is biased to one side under the radial force, which makes the original clearance disappear, the oil film is damaged, and the dry friction is formed, which soon makes the surface of the piston and the cylinder block strained. Its characteristics are that the strain area is larger, about 1/3 of the cylinder area, the trace of the strain is shorter, equal to the displacement of the rod.


(5) Improper repair method

Not only can cause the piston and cylinder block strain, even can cause more serious consequences. When repairing a hydraulic breaker for a unit, we found that in the step hole of the cylinder block, the large hole has a large taper near the small end, which is 0.28mm smaller than the average size of the large hole, and the coaxiality deviation between the large hole and the small hole is more than 0.15mm. It is understood that the customer tried to repair the strained cylinder block by honing and prepared a new piston before sending it for repair. As a result, life jam occurred during the test run. After disassembly, it was found that both the piston and the cylinder had extensive strain, which was caused by improper repair methods. It is not suitable to use honing method to repair the strained or worn step hole, because the structure of the honing head is not suitable for grinding the step hole, and because the honing head is floating relative to the workpiece, honing processing is not suitable to repair the hydraulic hammer has been strained cylinder.

Post time: 2022-12-16