Checking plastic parts

Repair

Checking plastic parts

Checking plastic parts

Checking elastic pad

  1. 1.
    Once the adapter plate has been removed, take out the elastic pad and execute a visual and dimensional check.

The drawing shows the check dimension ”h”. This dimension is reduced the longer the elastic pad is used, either due to the material “settling” or due to wear through relative movement.

After a service life of approx. 500–1000 operating hours, dimension ”h” may fall below its lower limit, at which point the elastic pad must be replaced.

The lower limit for dimension “h” is 81 mm (3.19 in.).

  1. 1.
    Measure dimension “h“ and replace elastic pad when it is below 81 mm (3.91 in.).

When contact pressure is too high, the material of the elastic pad “flows” over the edges of the cylinder cover, causing the material to crack and leaving notches.

As time goes on these notches get bigger and can cause larger pieces of the elastic pad to break off or lead to deep cracks.

  1. 1.
    Replace elastic pad when deep cracks are detected.

Checking shock absorber

  1. 1.
    Once the percussion unit has been removed, take out the shock absorber and execute a visual and dimensional check.

Here again, excessive loads to the shock absorber may cause cracks/notches which then necessitate replacement in pairs.

The check dimension ”h” should be measured when dismantling the hydraulic breaker.

The lower limit for dimension “h” is 31 mm (1.22 in.).

  1. 1.
    Measure dimension “h“ and replace both shock absorbers when it is below 31 mm (1.22 in.).

Checking lower guide plates

  1. 1.
    Once the percussion unit has been removed, take out the lower guide plates and execute a visual and dimensional check.

The guide plates are subject to wear during normal use. The penetration of dust and dirt along with surface pressure cause heavy abrasion to the plates.

Further possible wear and damage:

  1. Abrasion

  2. Dirt deposits

  3. Conchoidal fracture

Depending on condition, the guide plates should be replaced individually or in sets.

The check dimension ”h” should also be measured upon dismantling to decide whether replacement is necessary.

The lower limit for dimension “h” is 12 mm (0.47 in.).

  1. 1.
    Measure dimension “h“ and replace guide plates when it is below 12 mm (0.47 in.).

Plate thickness is mostly only wear-reduced locally. A decision on whether to replace the guide plates therefore depends on the general condition of the parts in each case.

Note

By measuring the thickness of the guide plates it is possible to determine whether replacement can be postponed by inserting thin sheets as shims.

When shimming in this way, a sheet at least 2 mm (0.08 in.) thick must be inserted on each side.

However, shimming must be restricted to max. 2 mm (0.08 in.) on each side. Service openings must remain accessible!

Checking upper guide plates

  1. 1.
    Once the percussion unit has been removed, take out the upper guide plates and execute a visual and dimensional check.

The upper guides plates are made from special foamed plastic (PUR) and therefore have a certain degree of elasticity.

After removing the percussion unit, these plates can be removed from their guides and examined.

Here again, a decision is made depending on the individual condition of the plates as to whether replacement is necessary.