Repair work

Repair

Repair work

Repair work

To dismantle the hydraulic breaker observe all instructions given in Chapter Dismantling.

To assemble the hydraulic breaker observe all instructions given in Chapter Assembling.

Changing tensioning bolts

Note

If a defective/fractured tensioning bolt is replaced, it is not necessary to replace the other tensioning bolts if the hydraulic breaker was no longer used (or only for a very short period) after the defect/ fracture occurred.

However, if the part has been damaged for some time, all tensioning bolts must be replaced.

  1. 1.
    Remove tensioning bolts.
  2. 2.
    Check condition and function of tensioning bolts, washers and threaded inserts in the lower breaker part, replace if necessary.
  3. 3.
    Mount new tensioning bolts and washers to the matching (marked) borings.
  4. 4.
    Observe tightening regulations and torque for tensioning bolts (see Chapter Tightening torques).

Removing scores from main control valve and bore

Note

The main control valve must be able to move easily in the bore. If this is not the case, check to see whether jamming is caused by scores.

  1. 1.
    Remove main control valve.
  2. 2.
    Smooth away scores on main control valve using emery cloth.
  3. 3.
    Check bore for scores, if necessary smooth off using emery cloth.
  4. 4.
    Carefully clean treated surfaces then oil lightly with hydraulic oil.
  5. 5.
    Fit control slide valve.

Note: When restarting the hydraulic breaker, observe for malfunctions. If there are start-up problems or the hydraulic breaker does not run smoothly, inform your local Epiroc Customer Center / dealer.

If scores or galling cannot be fully removed by careful polishing, a decision must be taken in each case as to whether to fit new parts or have the parts in question reworked in the factory.

Removing scores on percussion piston and cylinder bore

Note

If scores can be seen on the removed percussion piston they must be removed by mechanical finishing or manual polishing with emery cloth. The piston diameter may not be reduced by more than 0.05 mm (0.002 in.) by mechanical reworking. Score ends in the grooved area of the piston must be carefully deburred. If scores or galling cannot be fully removed by careful polishing, inform your local Epiroc Customer Center / dealer. A decision must be taken in each case as to whether to fit new parts or have the parts in question reworked in the factory.

If scores can be seen on the cylinder bore, inform your local Epiroc Customer Center / dealer. A decision must be taken in each case as to whether to fit new parts or have the parts in question reworked in the factory.

  1. 1.
    Remove percussion piston.
  2. 2.
    Check cylinder bore and percussion piston for scores and follow the previously described routine for each.
  3. 3.
    Thoroughly clean treated parts and all grooves and lubricate with hydraulic oil.
  4. 4.
    Fit percussion piston.

Note

When restarting the hydraulic breaker, observe for malfunctions. If there are start-up problems or the hydraulic breaker does not run smoothly, inform your local Epiroc Customer Center / dealer.

Replacing retainer bars and working tool

If burring is detected when removing the working tool or the two retainer bars it must be ground off carefully. If excessive wear such as sharp edges, notches or heavy indentations are detected, the retainer bars must be replaced.

  1. 1.
    Check the impact surface of the working tool for chips and cracks.
  2. 2.
    Check the impact surface of the working tool for deformation:

    A = new working tool

    B, C = worn working tool

  3. 3.
    Replace the working tool if you detect chips, cracks or deformations (B and C).
  4. 4.
    Check the wear condition of the impact ring if you detect deformations (B). Replace impact ring if necessary.
  5. 5.
    Check the shaft of the working tool for wear whenever replacing it.

     

     

  6. 6.
    Replace the working tool if the shaft has worn to the minimum diameter Dmin of 97 mm (3.82 in.).
  7. 7.
    Check both retainer bars whenever replacing working tools.
  8. 8.
    Rework or replace the retainer bars if you find any signs of wear, such as sharp edges, notches or severe erosion.
  9. 9.
    Deburr the retainer bars by careful grinding.
  10. 10.
    Install the retainer bars in their reversed orientation if they cannot be reworked anymore.
  11. 11.
    Replace the retainer bars if both sides cannot be reworked anymore.
  12. 12.
    In addition check all four sealing plugs and replace if necessary or provide if any are missing.

Changing the wear bushes

The inside diameter of the lower wear bush has to be checked every time the working tool is changed and at the latest every 100 operating hours.

The wear bushes are to be changed when their inside diameter has increased from 100 mm (3.94 in.) to 103 mm (4.10 in.) (measuring point see below).

When the lower wear bushing is removed, the inside diameter of the upper wear bushing must be checked, replace if necessary. In this case replace impact ring too.

Removal with press-out aid

Note

This work can only be performed in a well equipped workshop with a hydraulic press of 200 tonnes (441000 lbs) or more capacity.

  1. 1.
    Knock out locking bolt using pin punch and hand hammer.
  2. 2.
    Fit grip of press-out-aid (A) into screw (B) and screw in press-out-element, bottom (D).
  3. 3.
    Fit the press-out-aid into the lower breaker part from below, rest on lower bush.
  4. 4.
    Remove screw (B) and grip (A) from press-outaid.
  5. 5.
    Place the press punch on the press-out-aid from above and press out the lower bush.
  6. 6.
    Fit grip of press-out-aid (A) into screw (B) and screw in press-out-element, top (C).
  7. 7.
    Insert press-out-aid into the lower breaker part from below, rest on impact ring.
  8. 8.
    Remove screw (B) and grip (A) from press-outaid.
  9. 9.
    Place the press punch on the press-out-aid from above and press out upper wear bush together with impact ring.

Help when steel bushes are stuck

Note

If a steel wear bush is stuck and cannot be pressed out, a qualified welder may apply welding beads. When the part cools down again, the wear bush will contract and come loose in its seat.

Note

Welding of the hydraulic attachment is only permitted if carried out by qualified welders who:

  1. have been trained to operate MIG welding equipment according to the national regulations.

  2. know all the relevant national/regional safety provisions and accident prevention rules.

WARNING

Harmful vapors

Harmful vapors are generated when welding bronze.

  1. Do not apply welding beads to a bronze wear bush.

WARNING

Harmful vapors

Chisel paste is flammable. Harmful vapors are generated when chisel paste is burnt.

  1. Remove all chisel paste and other contamination from the wear bushes.

  2. Provide sufficient ventilation during welding.

  3. Wear personal protective equipment (ambient air-independent breathing mask) if no air extraction system is available.

WARNING

Risk of fire / explosion

Flammable detergents and chisel paste residues can ignite or cause an explosion during welding.

  1. Do not use flammable detergents.

  2. Carefully remove all detergent residues from the wear bushes.

  3. When applying welding beads, keep a 20 mm (0.79 in.) distance to the lubricant groove of the wear bush, since this may still contain lubricant residues.

  1. 1.
    Apply thick axial or radial welding beads to the inside of the worn wear bush using an electrode welder.

    Upon cooling the wear bush and impact ring contract and loosen in their seats.

Note

If it is not possible to replace the wear bushes, a complete replacement lower breaker part can be purchased from your local Epiroc Customer Center / dealer.

Mounting new wear bushes and impact ring

WARNING

Risk of injury from excessive heat or cold

Heated or cooled parts may cause serious injury to the hands.

  1. Wear protective gloves when handling heated or cooled parts.

  1. 1.
    Before fitting impact ring, supercool it in liquid nitrogen (N2).
  2. 2.
    Heat lower breaker part to around 200 °C (392 °F).
  3. 3.
    Freeze both wear bushes for about 8 hours (-18 °C (-0.4 °F)).
  4. 4.
    Fit the impact ring.
  5. 5.
    Wait until lower breaker part has cooled down.

    Note

    The wear bush recesses must be aligned with the bores for the locking pins in the lower breaker part.

  6. 6.
    Fit both wear bushes.
  7. 7.
    Fit locking bushes and locking pins.

Welding on breaker box

Note

Welding of the hydraulic attachment is only permitted if carried out by qualified welders who:

  • have been trained to operate MIG welding equipment according to the national regulations.

  • know all the relevant national/regional safety provisions and accident prevention rules.

WARNING

Harmful vapors

Chisel paste is flammable. Harmful vapors are generated when chisel paste is burnt.

  1. Remove all chisel paste and other contamination from the wear bushes.

  2. Provide sufficient ventilation during welding.

  3. Wear personal protective equipment (ambient air-independent breathing mask) if no air extraction system is available.

WARNING

Risk of fire / explosion

Flammable detergents and chisel paste residues can ignite or cause an explosion during welding.

  1. Do not use flammable detergents.

  2. Carefully remove all detergent residues from the wear bushes.

NOTICE

Damage to the breaker box

As the worn parts burn away, the breaker box may buckle as high levels of heat are produced and the steel’s properties may change.

  1. Once a wear part has burnt away, leave the breaker box to cool before removing the next part.

Weld seam preparation

  1. 1.
    Before starting welding work, remove all contamination on and around the seam edges.

Scale, rust, oil, paint and moisture give off hydrogen which can jeopardise welding results and result in cracks.

Preheating temperature

To avoid cracking, a higher working temperature is recommended depending on steel plate grade, overall plate thickness and hydrogen content.

Combined sheet thickness of:

  50 mm (1.97 in.)     75 °C (167 °F)

  70 mm (2.76 in.)   100 °C (212 °F)

100 mm (3.94 in.)   150 °C (302 °F)

Fillers

Hardox plates should be welded using fillers (electrodes / wire) producing a low hydrogen content in the weld. Filler as for ST 52-3. e.g. MAG wire SG2 / SG3 or electrodes E 5143B10.

Fillers must be stored in such a way as to avoid any moisture absorption.

Post-treatment of welds

Welds must be made without notches or ground free of notches in order to reduce tension.

Replacing the wear protection

If wear is detected on part or all of the wear protection on the lower part of the breaker box, the parts can be replaced to restore the wear protection on the breaker box.

MB 750 / MB 750 E

MB 750 DP

After removing the percussion unit and all plastic parts from the breaker box, the worn parts can be removed by an expert using a flame cutter or the weld seams removed using a cutting wheel.

Once the worn parts have been removed, the new parts can be attached and welded in place.

The new wear protection kit can be purchased from Construction Tools.

  1. 1.
    Remove worn parts one at a time using a flame cutter or the weld seams removed using a cutting wheel.
  2. 2.
    Grind flame-cut areas on the breaker box flat.

    Weld seam preparation

  3. 3.
    Before starting welding work, remove all contamination on and around the seam edges. Scale, rust, oil, paint and moisture give off hydrogen which can jeopardise welding results and result in cracks.

    Preheating temperature

    To avoid cracking, a higher working temperature is recommended depending on steel plate grade, overall plate thickness and hydrogen content.

  4. 4.
    Preheat new wear parts and the breaker box area where you have to carry out weld seams to 150 °C (302 °F) to 200 °C (392 °F).

    Optional welding processes

    gas metal arc welding ISO 4063-13

    gas tungsten arc welding ISO 4063-14

    shielded metal arc welding ISO 4063-111

    Post-treatment of welds

  5. 5.
    Make welds without notches or grind free of notches in order to reduce tension.
  6. 6.
    Run a non-destructive surface crack test (but at least a visual weld seam check) of all weld seams.

    Tack welds and root beads are the points which are most susceptible to the formation of cold cracks.

  7. 7.
    If you find cold cracks in a welded joint, you have to grind them out or gouge them out with a carbon arc (grind joint edges) and then perform a repair weld.

MB 750 / MB 750 E

MB 750 DP

Repairing cracked welds

If cracked welds are detected, they can be repair welded after the percussion unit and the plastic parts have been removed from the breaker box.

After the necessary preparations have been made by a specialist, repairs can be carried out.

Possible weld cracks:

Side plate / top plate / front plate joint

Side plate / damping element bearing joint

Side plate / bottom plate joint

The necessary preparations include:

  1. Cleaning the points in question.

  2. Grinding down the cracks until the weld is crackfree.

  3. Providing suitable weld fillers (electrodes or wire such as used for steel grade St. 52-3, e.g. MAG wire SG2/SG3 or E 5143B10 electrodes).

  4. Preheating the zone to be repair-welded to approx. 100 °C (212 °F).

If possible, the repair zone should be filled and welded from both sides.

Replacing the bottom plate on the breaker box

If the bottom plate of the breaker box is heavily worn, it can be replaced simply with a new one.

After removing the percussion unit and plastic parts from the breaker box, a specialist can remove the bottom plate by flame cutting and replace it with a new one.

This job requires the following preparations:

  • Flame-cut areas on the breaker box must be ground flat

  • Prepare weld seams

  • Pre-heating temperature

  • Filler materials

  • Post-treatment of weld seams

Reworking the retainer pins for the shock absorber

If in the course of time the retainer pins for the shock absorber in the breaker box have become loose due to the widening of the bores, they can be welded back into position.

The following steps are necessary:

  1. 1.
    Remove the percussion unit and all plastic parts from the breaker box.
  2. 2.
    Remove the two retainer pins.
  3. 3.
    Countersink bores from above Ø = 22 mm (0.87 in.), 8 x 45°.
  4. 4.
    Reinsert retainer pins in bores and align to size weld from above and clean weld seam.
  5. 5.
    Once the weld has cooled, replace shock absorbers and other plastic parts.
  6. 6.
    Refit percussion unit in breaker box.