By Richie Gushulak, Product Manager / Design Engineer
A successful Core Drilling operation involves the continual advancement of Core Tooling into the ground, as efficiently as possible, until the point of bore hole completion. The drilling process incorporates the use of a Core Barrel Assembly which includes a removeable Inner Tube Assembly. Each time this inner assembly is winched from the rod string, the Head Assembly must be fully detached from the Inner Tube, rendering the core sample accessible to the drilling team for further processing. It is during this stage that the drilling team can fully assess the Head Assembly for damaged or worn components or any other anomalies. It is imperative to address these issues prior to using this Head Assembly on the next drill run. Greasing the Head Assembly is one very simple, proactive step drillers and helpers can take to minimize the wear of the assembled components and extend the time between replacing parts. It can also prevent serious downhole problems from occurring.
As with other mechanisms, Head Assembly components are subjected to wear over time and with normal use. Wear compromises the integrity of the parts and can lead to costly downtime. The rate or degree to which these parts wear can be drastically altered by the level of routine maintenance applied between each use.
During the assessment phase as mentioned, there is often ample opportunity to apply grease to the Inner Tube Cap Assembly. This assembly, which threads directly on to the Inner Tube, is equipped with a standard Grease Fitting. We recommended that you use a grease gun and apply grease to this fitting once each time the Head Assembly is detached from the Inner Tube (in normal drilling conditions this would equate to once each time a Drill Rod is added to the rod string).
During this critical preventative maintenance step, grease fills the Inner Tube Cap Body until it builds pressure at which time the grease will travel along the Spindle until it finds the Upper Bearings which are housed in the Spindle Bushing. Once completely refilled, grease will begin to seep out from the assembly adjacent to the Shut-Off Valves and Shut-Off Washers. Wipe away excess grease with a piece of burlap or a rag and the Head Assembly is ready to be reinstalled onto the Inner Tube. Grease is critical to the proper function of the Upper Spindle Bearing(s), Spindle Bushing, Spindle, Lower Spindle Bearing and Compression Spring. Without adequate grease, these components will be subjected to elevated heat and are prone to premature wear and/or failure.
Be Proactive – Inspecting for Wear Saves You Time in the Long Run
Worn Head Assembly components can often be replaced proactively with little issue, costing a small amount of downtime and the cost of the parts affected. Unfortunately, this is not always the case. Should a critical part fail during coring operations, the cost in downtime can become catastrophic to a drilling contractor. An example of this is expired ball bearings, causing parts to bind or jam together in the Core Barrel Assembly. The drilling company may be required to spend additional resources on solving the problem and in some cases, be forced to completely remove the Drill Rod string from the bore hole to address the issue. During this downtime, the exploration company is losing money instead of advancing the project. It is certainly a worthwhile safeguard to apply grease to the Head Assembly each run and continue to put core in the core box.