A basic, but important, tip is to “Keep it Clean”. Even the smallest foreign particle can cause untold damage to the Hammer.

“World Class” DTH Tools need tight tolerances between the piston and the internal running surfaces for speed and efficiency. Dirt or other foreign bodies passing through can become trapped between the outer wall of the piston and the internal bore of the cylinder.

When this happens, with the piston striking the bit at over 30 times per second, intense heat can be generated and minute cracks can begin to develop from the surface and travel inwardly to cause piston failure.

The tell-tail blue heat spots often seen on the surface of the piston affected by contamination, indicates that at some point the zone has been subjected to temperatures in excess of 600 centigrade. And whilst insufficient lubrication will cause heat zones to form, contamination is also a major contributor.

A further problem can occur when debris becomes trapped between the piston and the drill bit. Damage can be caused to the inter-face surface of the piston and bit anvil with the risk of face distortion and crack propagation.

If a new bit is fitted to a Hammer with a damaged piston face or alternatively, if a bit with a damaged anvil is fitted to an undamaged piston then cross damage will result at a very early stage.

The following tips will help reduce the risk of problems through contamination:

• Always store Hammers & Drill Pipes in a clean environment.
• Use clean protective end caps on Hammers & Pipes when not in use.
• Ensure Drill Pipes are clean on the inside prior to use. (welding scale can be present in new tubes).
• Brush any dirt off threads prior to use.
• Do not allow dust to build up around the break-out gate or on the carousel (Lazy Susan) table.
• When fitting the Hammer to the rig, leave the protective cap in place until the Hammer is ready to be coupled up.
• Do not use Hammers or Pipes knowing that contamination has entered the airways.
• Do not throw protective end caps to the ground but keep them in a clean place when not in use.
• Always service Hammers in a clean environment.
• Use only clean containers and sealable drums for air line lubricants.
• Take care to prevent contamination occurring when fitting new hoses or when attaching bull hoses to rigs with separate compressors.

Where heat spots or scoring marks are evident on the wall of the piston, it is advisable to remove them with  an emery stone or tape. If scoring is present within the bore of the wearsleeve, this can be smoothed with a Glaze Buster grinding tool, as used in the automotive industry to clean engine piston bores.