Over the past five years, I have seen so many drilling contractors around the world switch from buying down-the-hole (DTH) tooling from European-based manufacturers to lower-cost Asian suppliers.
Now, I am not saying that everything from the Far East is of inferior quality, because at the end of the day they have been sending people into space in locally manufactured craft since 2003. However, when speaking to the same drilling crews six months later, I am told that the product life just was not up to required standards. What was supposed to be a cost-reduction exercise actually ending up costing more in the long-term.
As a supplier of tooling, we have to think of ways of increasing the product life of DTH hammers and bits without affecting prices. In this day and age, everything we, as consumers, purchase comes with a so-called expected shelf-life; we only expect things to last for a set period of time. In our industry that means that the old adage of ‘you get what you pay for' can be felt, especially when it comes to DTH tooling.
Add in the fact that mineral and oil prices vary from minute to minute and it means drilling crews are constantly being expected to lower their overall cost per metre, creating an incredibly competitive marketplace for contractors, particularly in the water-well sector.
Here at Ibbotson Drilling Services, in an attempt to help our customers lower their cost per metre, in the month of May we offered free servicing of all DTH hammers across the UK. We received many types and brands in our workshop from Chinese-made through to the industry-leading brands of today.
A common issue we faced with the hammers we received for servicing during that month was corrosion on internal components caused by the presence of water. It is so crucial that every hammer is always run with effective hammer oil lubrication.
Think of a DTH hammer like the pistons in a car engine - without adequate lubrication, the pistons can seize in the engine block. Rock drill oils are recommended because they contain the emulsifying and viscosity additives necessary to deal with high-pressure and high air flow conditions in which water is usually present, if only from condensation in the air line. Oil not only provides slip to prevent pick-up and premature failure of components but it also acts as a seal on the surface of running parts, allowing them to use air more efficiently without pressure loss. It is, therefore, of paramount importance that the correct grade of oil is used at the appropriate consumption rate to suit volume and pressure, in line with the hammer manufacturer's recommendation.
Most modern valveless hammers, particularly when operating at high pressures, need a heavy oil weight providing, of course, that ambient temperatures allow the oil to run through the air line. It is good practice to stand the DTH hammer upright, with an appropriate thread protector, in oil after operation, as this helps to prevent any dirt entering the hammer or rust building up.
In hard, abrasive drilling conditions, chuck wear will be concentrated on the areas that coincide with the drill bit exhaust grooves. In order to prolong chuck life, the drill bit should be indexed so that the exhaust grooves are adjacent to those areas of the chuck with less wear. Indexing the bit will also even outchuck and drill bit spline wear.
It is advisable to monitor the rate of wear over a measured depth drilled to determine the frequency for re-grinding of the carbide inserts. The flat widths should generally not exceed 25 per cent of the button diameter, although this varies from manufacturer to manufacturer.
Recently, here at Ibbotson Drilling Services, we have focused towards servicing our clients' tooling to ensure maximum meterage and life - in particular, DTH hammer and drill bits, which are at the forefront of any contractor's business. Through the ongoing support of our partnership arrangement with Drillwell, both businesses have the ability to maintain a wide-range of drilling accessories. Investment in breakout equipment, servicing tools and lathe tooling will allow this partnership to grow into a one-stop service centre for all drilling contractors. Services ranging from re-threading casing and drill rods right through to re-grinding of DTH bits.
