August 1, 2013
By Joe Bradfield
Every drilling rig comes with a list of preventive maintenance items. Some items are to be performed every shift, some once a week, others every so many hours of operation. In his position as product manager of Surface Drilling Equipment for Atlas Copco, Mike Wentworth has quite a bit of experience and can sympathize with drillers and owners about why some checklist items get skipped. Some things don’t cause immediate costly failure, and stopping to inspect or service some of them can be a hassle because an operator actually has to crouch down, get under them, or open them up for inspection.
But Wentworth is also keenly aware of why what you don’t see — or what you don’t look for — can, indeed, hurt your bottom line. Gleaned from service centers and from the experience of those who learned firsthand the high cost of premature failure, here is his list of the top eight preventive maintenance oversights that erode a rock driller’s profit margins.
1. Keep the accumulators charged.
This is at the top of Wentworth’s list. Every make of drill has a manufacturer’s specified frequency for charging accumulators. Whether it’s once every 40 hours or once every two weeks, the accumulators must be recharged with nitrogen to the proper levels. But some operators wait until they see the hoses start to vibrate before resetting them to the proper pressure. That’s too late.
Vibration means there is little to no gas left. During the time it took for the charge to deplete enough to notice the vibration, heat is already damaging the hammer and drill string couplings. Wentworth says that at $500 to $1,000 a steel, owners want the expected life for their equipment. The damage to the hammer is hard to assess externally. It might go undetected until its overhaul.
2. Clean out dust filters.
Operators don’t always pay attention to filters, which are behind the drill. Checking filters needs to be a part of the operator’s regular inspection ritual. By comparison, when a household vacuum sucks dust through a compromised bag filter, dust fills the room. No one tolerates that in a house so the problem is quickly remedied, resulting in no equipment issue.
Outdoors, though, a driller might tend to tolerate it more, without realizing the damage that is taking place on the fan. Unfiltered dust sandblasts the fan’s blades. As the blades deteriorate, the fan can start to spin out of balance. An out-of-balance fan wears away at its hydraulic motor, causing it to leak hydraulic oil. Replacing a complete fan is an expensive bit of downtime.
Operators must inspect filters regularly, especially checking for water contamination in wet drilling conditions. A heavy, wet filter tears much more easily.
3. Keep coolers clean.
Wentworth says his first five items were a challenge to prioritize. At times, pressure washing the coolers was at the top of the list because it’s such a simple thing to do, yet so often gets overlooked or put off. It’s definitely a top priority, though, because running fluids hotter than specified compromises their lubricating properties and is a primary cause of their breakdown. A rig’s coolers must be regularly cleaned to allow them to control heat.
4. Drain water out of the fluids.
Operators should routinely drain water from the diesel filter and both the hydraulic oil reservoir and the compressor, especially in hot climates. Atlas Copco advises its rig owners to drain water out of the compressor oil at least every other day, at a minimum. Water causes corrosion and, in cold climates, freezes up the valves. Lubrication properties are then compromised. Wentworth says some people blame equipment manufacturers when their hydraulics froze up, but it’s almost always the result of operator negligence.
5. Grease the hoses.
Wentworth said there are exceptions, but on most makes of drills, including Atlas Copco’s, the hydraulic hoses attached to the rock drill run over a drum as they ride with the feed. Failure to maintain exterior lubrication of the hoses may cause chafing that wears off the hoses’ protective covering. Using even the cheapest No. 2 grease available will preserve hose life.
6. Maintain rubber dust collector lining.
Inside the dust collection system, a rubber lining acts as a shock absorber and deflector, protecting the collector’s metal sides. If the lining were deteriorated or missing, it wouldn’t take long for the high-velocity rock chips and fines to wear a hole through the metal. Since it’s so expensive to replace a dust collector, Wentworth says rigs whose operators didn’t maintain their rubber dust collection lining will often, instead, have a welded patch on the outside of the collector. Most of the time, it’s only one patch because operators make sure to maintain the lining from then on, and there are no further problems.
7. Adjust the rock drill cradle wear slides.
As a rock drill cradle’s wear slides are worn down along the feed, they start to develop a little slop in their play. If not brought back to tolerance, the widening gap allows the hammer to wobble. The oscillation is not limited to the hammer. It transfers down the drill string and directly leads to excessive rate of wear on the drill string components. Adjusting the wear pieces on the cradles promotes higher production rates by efficiently drilling straighter holes, which consequently reduces energy to drill the holes and also minimizes component replacement frequency and cost.
8. Maintain centralizers.
Wentworth says maintaining the centralizers goes hand in hand with keeping the cradle wear slides adjusted. Adjust the centralizers to hold drill steel tight while drilling. If not, holes will be allowed to deviate, steels wear out faster, and, Wentworth says, “things break.” Again, drilling straighter holes raises production rates through efficient drilling, getting the hole drilled in the quickest time. It minimizes energy spent while drilling and protects against profit margin shrinkage due to accelerated frequency of component replacement.
Those drillers who can afford poor performance and shrinking profit margins are welcome to ignore all of the above, as manufacturers will step up to replace any parts and equipment that a drilling company treated as consumables. However, manufacturers would actually be much, much happier to hear you boast about how long you’ve used their equipment without a hitch. It’s best not to cut corners on preventive maintenance.
Joe Bradfield is senior writer for Ellenbecker Communications, an international communications firm specializing in the drilling, mining, and construction industries.