Loading of bearing retaining pin of tricone drill bit

Abstract

Improvement of cone drill bit design is an engineering challenge as it is connected with considerable energy to be transferred via the drill to well bottom in the limited well space. In such conditions, it is difficult to create a full-size bearing assembly, including bearings and lubricating devices, as well as the sufficiently efficient cutting structure of the bits. Moreover, the condition of equal lives of the cutting structure and the bearing assembly is to be fulfilled. The operating practice of tricone drill bits in shothole drilling reveals their low serviceability. The life of a bit ranges from a few hours to a few days subject to physical and mechanical properties of rocks. The main cause of bit failure is damage of the retaining pin shoulder rivet under high contact stresses. Aimed at improvement of cone drill bit design and justification of engineering changes, the stress–strain analysis of the bearing retaining pint is performed, and it is found that the pin shoulder rivet experiences essential contact stresses and bending loads. It is proposed to equip cone drill bits with circulation lubrication system for the bearing assembly. Lubrication improvement can ensure reduction in loading of the bearing assembly components and, consequently, provide higher durability and wear resistance of these parts. The study was supported by the Ministry of Education and Science of Russia according to the state contract with the Ural State Mining University, Contract No. 0833-2020-0007.