Failure analysis and finite element simulation of key components of PDM

• Oval holes caused by thermal failure in general rubber lining.
• Rubber layer peeling and damage appear on the surfaces of rubber linings.
• The thrust bearings experienced serious wear, corrosion and rupture.
• Universal shaft petals appear fractured in the root and wear on contact surfaces.

As one of the most commonly used downhole drilling tools, PDM (Positive Displacement Motor) is widely used in drilling and workover. Drilling practice shows that PDM is frequently scraped for the failure of key components. The coupled thermo-mechanical finite element model of rubber linings, finite element models of thrust bearing and universal shaft petals were established respectively, and the failure reasons were discussed by simulation. It was found that there are oval holes caused by thermal failure in general rubber lining, while no oval holes in the uniform wall thickness rubber lining. Rubber layer peeling and broken appear on the surfaces of rubber linings under the load of drilling fluid and rotor. Thrust bearings experienced serious wear, corrosion and rupture in the terrible downhole environment. The universal shaft petals appear fracture in the root, and wear on contact surfaces under torque and axial load. The results obtained in the paper show that the analyzing model and evaluation methods are quite reasonable and can be generally applied, which have great significance on the enhancement of structural design and repair for PDM in the future industry.