It’s been a while since we’ve done a blog on matrix troubleshooting. Core bits play an integral role in getting great drilling performance and many things can cause a bit to underperform. One of the best ways to determine what is off is to examine the wear profile of your bit crown and change drilling parameters if necessary. Today, we’ll look at burnt core bits, some of the causes and some of the solutions.
As we’ve mentioned in earlier posts, the ideal wear on a core bit is attained when the wear on the diamonds and matrix is balanced and even, and the full depth of impregnation is evenly consumed. This allows the driller to get as much footage as possible on the bit. In comparison the image above shows a matrix that has completely melted with waterways that are closed.
Water is the likely culprit
The most likely reason your core bit has burned is water circulation: either the water circulation is poor or it has run out. Luckily, knowing that the problem is related to water, or the lack of it, there are a number of actions you can take.
Check the pump
If the pump is not performing optimally, your water circulation can be reduced. This can cause burning of a core bit or shorter bit life. Make sure your pump is cleaned regularly, checked for maintenance issues, leaks, and its parts replaced as required.
Check the rods
Do a quick check to make sure your rods are not leaking. Rods can be damaged prematurely by abuse or misuse, or just simply wear out from use, which will lead to leaking. Poor or no lubrication of the drill string can cause vibration and increased torque both of which lead to increased wear and tear of the rods, and eventual leaking. A good quality metal based thread compound is a must to prevent galling and reduce damage from constant making and breaking of rod string. Check this guide for more complete information on handling your drill rods.
Check the length of the inner tube:
The inner tube adjustment is important to ensure the bit gets enough water. If the core case is too far from the bit bevel, you risk washing away more fragile formations, if the core case is too close to the bit bevel, you will starve the bit of water and burn the matrix.
Increase the water flow
If you have checked the items above and found no problems, you should probably increase your water flow. The water flow should be as high as possible but must be related to the bit size and type of rock to be drilled. To make sure you have the correct water flow, you should refer to recommended water flow charts such as the one found in this guide.
We have already written about polished diamonds and overly exposed diamonds, because examining the wear patterns on your bit crowns is an excellent way to improve your drilling performance. If ever in doubt about the wear patterns on your core bit and how to remedy the situation, don’t hesitate to contact a member of technical crew for tips or advice.