Evaluation of operating life length of rotary tricone bits using Measurement While Drilling data

• The paper suggests a practical method for evaluating the performance of rotary tri-cone bits based on large scale Measurement While Drilling (MWD) data in an open pit mine.
• Production degradation profile of 52 bits has been carefully considered for evaluating this method.
• While using this method, the relation between production degradation coefficient and life length of the bit has been established.
• Multivariate data analysis shows the relationship of all the interacting parameters (recorded from MWD system) with bit life length. The influence of air pressure on recorded penetration rate has been discussed.
• From multivariate analysis, the abnormal behaviour of the bit is detected. The reason of abnormal behaviour is also identified.
• Finally, the analysis shows that rock mass characteristics represented by penetration rate and specific energy basically are poorly correlated to bit life length. Instead, bit life length seems well correlated to the operational parameters such as rotation torque, rotation speed and to a minor extent feed force.
• However, these relations (by using MWD data) must be verified for other mines such as coal or bauxite where the variation in hardness with possibly very different geological setting exists.