Page 38 - Diamond Products Catalog

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TROUBLESHOOTING
Much can be learned from examining impregnated bits when they are pulled from the hole. The illustrations and observations in this section can help identify and remedy many common field problems. Normal retirement or discarding of an impregnated bit should take place only after it has been totally consumed. Most Boart LongyearTM impregnated bits have full-depth waterways to allow the bit to be fully consumed. The first indicator that a bit is nearing normal retirement is a rise or kick in pump pressure due to the diminishing depth of waterways. In StageTM bits, this rise is observed at the transition of each stage.Ideally, an impregnated bit drills steadily with the matrix and diamond wearing away at the same rate.
NORMAL WEAR PATTERNS
New Condition
IRREGULAR WEAR PATTERNS
Ideal Wear Pattern
The face wear pattern of an impregnated bit should be relatively flat with slightly chamfered sides. Bit feels sharp, comet tails have formed to support diamonds. Diamonds release from matrix as they are worn. Gauge stays within tolerance.
Normal Retirement
Full depth of impregnation evenly consumed. Gauge stays within tolerance.
Concave Face Wear (Rounded to Inner Diameter)
Cause: Often caused by excessive penetration rate for the RPM used. This can also be caused by core grinding, overdrilling.
Solution: Reduce penetration rate or increase RPM
Concave Face Wear (Rounded to Outer Diameter) Cause: Insufficient water flow
Solution: Check pump and rod string for leaks; increase pump output.
The causes and solutions described in this section are not exclusive lists, but represent common causes and generally effective solutions based on the experience of Boart Longyear and its customers.