Numerical investigation of contact stress between rotor and stator in a two-lead progressing cavity pump

• A three-dimensional finite element model for a two-lead PCP is established.
• The contact stress distribution in seal lines for the operating PCP is presented.
• An approach based on Stribeck-type curve to predict friction behavior in PCPs is proposed.
• The actual wear and damage phenomena of PCPs appearing in oilfields are explained.

The contact stress between rotor and stator in a progressing cavity pump (PCP) is critical to seal performance and service lifetime of the PCP. In this paper, an approach to predict the contact stress and friction behavior in PCPs is proposed. The approach is based on the results from the finite element analysis (FEA) and Stribeck-type curve. A three-dimensional finite element model for the contact stress between the rotor and the stator within a two-lead PCP is successfully established. The fluid pressure, the eccentric force and the laden torque are applied to the model. And the finite element analysis is conducted to investigate the contact stress between the rotor and the stator in the two-lead PCP. The simulated results show that the contact stress in the spiral seal lines (SPSLs) is always high compared to that in warping seal lines (WSLs) at the identical relative position, and the contact stress increases along seals from the first seal line to the last one. The maximum contact stress of the PCP appearing in every seal line is off-center. It is found that the serious wear and/or damage for the progressing cavity pump during operating always occurs on the paths which are off-center of the spiral seal lines. The results are validated against the actual phenomenon which appeared in oilfields from open literatures.