By Colin Rice
Colin Rice Exploration Drilling Advisory - www.colinrice.co.za
A summary of the relevant legal requirements of wireline retrieval operations.
This is the first article in our Technical Series on Wireline Retrieval Operations. Click here for an outline of the entire Technical Series on Wireline Retrieval Operations.
Wireline retrieval involves similar processes and equipment as is used in other hoisting operations and so all of the requirements that apply to hoisting a drillstring apply equally to retrieving and deploying a wireline inner tube assembly.
We have published two previous articles which focussed on the legal aspects of hoisting operations. I would like to remind you of some key points in this article, but for more detailed information, please read article 1 and article 2 here.
Whilst the requirements below apply specifically to South African law, they are a good guide on how hoisting and lifting, in general terms, should be approached:
All elements of lifting equipment and lifting tackle must be correctly designed, maintained and operated.
Hoisting systems that use steel wire ropes must be designed and operated with a factor of safety of 6.
All lifting tackle (the components that connect the rope to the load) must be designed and operated with a factor of safety of 4, and,
All elements of lifting equipment must be clearly and conspicuously marked with their safe working load.
I am frequently challenged by contractors on the factor of safety of 6 that we have to apply to steel wire ropes, many believe that it is too large a factor and that it reduces the “legal” hoisting limit of many drill rigs. For this reason, many contractors believe that it should be reduced.
I would agree with this suggestion but only if we could ensure that steel ropes were properly inspected and discarded - my experience however, tells me that we are not very good at this! In the past 3 weeks alone I have come across 5 instances where hoist ropes have snapped and many, many more instances of wireline rope snapping. I believe that all of these occurred because of the contractor failed to observe point 1 above. Unless we really focus on improving maintenance and operational issues we will continue to have hoisting system failures and this potentially puts the contractor, and the mining company on the wrong side of the law.
The next article in this series focuses on the processes involved in wireline retrieval.