Drilling Offsider Exposed to Potential Fall From Height
Description of the Incident
A drilling contractor was pulling drill rods on a top drive drill using a clamshell arrangement. During this process, the clamshell hook would not lower under its own weight and the driller identified that the utility winch rope had spooled incorrectly and was stuck onto the winch drum mounted on top of the mast.
The driller instructed a member of the drill crew to climb on top of the rotation head and the driller then proceeded to raise the offsider and the rotation head approximately 7 metres up the mast to allow the offsider to access the winch and free the stuck winch rope. The position of the offsider on top of the rotation head is shown in the illustration below.
Once the epee was completed, the driller lowered the rotation head back to the bottom of the mast where the offsider was able to climb off the rotation head.
Comment and recommendations
This is such an interesting and important alert because it clearly highlights a problem that exists on every exploration drill rig! Unfortunately, mining companies are unaware of the problem and contractors ignore the problem.
All current drill rigs, both chuck drive and top drive drills, have a rod clamp or break-out table rigidly fixed to the base of the mast and so, if the drillstring is in the borehole, it is simply not possible to lower the mast to gain access to a component mounted up the mast.
As shockingly negligent the driller’s actions appear to have been, in this case, he could not lower the mast and he could not pull any more drillpipe – he was stuck and so he had two options;
He could get a member of the drill crew to clamber up the mast or,
He could use the rotation head as a “lift”.
The driller assessed that option 1 was more hazardous than option 2 and so he selected option 2.
This situation has occurred many, many, times in the past and it will occur many more times in the future. Let’s be clear, there will be occasions when a component mounted up the mast will require repair while the drillstring is in the borehole and in some of these situations, it will be necessary for a member of the drill crew to ascend the mast.
Over the years, I have been fortunate enough to have audited a number of exploration drilling contractors and never have I seen a Standard Operating Procedure (or SWI or SWP or JSA or JRA, call it what you will) for this activity. In every case, when I have asked for a procedure, the response has been that the operation is treated as non-routine and the contractor will carry out some sort of job risk assessment before he conducts the activity. In my view this is absolute nonsense, while carrying out a repair at height may be “non-routine”, it is most certainly “foreseeable” and, if a proper and complete activity-based risk assessment had been done, it would have been identified. A fully risk assessed procedure could then have been developed.
I guess that the contractor would not want to tell his customer that it may be necessary for a member of the drill crew to ascend the mast. While this is understandable, I believe that it indicates a poorly developed safety management system. If we are to achieve zero harm then we all have to have a common understanding of risk and a shared understanding of how risk is managed. Hiding or ignoring risk is a recipe for disaster.