Simulation studies on drilling mud pump plunger seal failure under ultrahigh pressure and ultradeep conditions

•The mechanisms and causes of drilling mud pump plunger seal failure are discussed.•The inadequate seal structure is the root cause of the failure.•Inadequate structures cause uneven, large stress, strain and pressure distributions.•Improvements in structure can reduce failure effectively. Plunger seals are key components in drilling mud pumps. Under ultradeep and ultrahigh pressure conditions, plunger seals often fail and their service life decreases. This leads to lower drilling mud pump efficiency. In this paper, the simulation study is carried out with the contact finite element method, using the stress–strain curves of rubber material tests, Mooney-Rivlin constitutive model material parameters are determined through data fitting. Analyzing the seal mathematical model, building the finite element model, using penalty function algorithm based on the contact surface, applying loads and boundary conditions to simulate the assembly and the actual working conditions of the seal and analyzing the distribution law of the stress, strain and contact pressure of plunger seal, the easily failure places are found, the root causes of failure are analyzed, and the fundamental ways of preventing seal failure are proposed to provide a theoretical basis for the structurally optimized design of the new drilling mud pump plunger seals. The results show that: failure of the rear of the sealing ring, the root of V-type surface between the sealing ring and mantle ring, the sealing surface lips between the seal ring and the plunger, and the sealing surface lips between the seal ring and the cylinder is extensive. The first sealing ring is most damaged. The internal causes of the sealing ring’s failure are the uneven distribution, high stress and stress concentration of stress and contact pressure. However, the root reason for failure is the inadequate sealing ring structure design. Structural improvements should be considered to reduce stress and strain and provide a more even stress distribution. If peak contact pressures reach the outer sealing ring and prevent abrasives from entering the sealing surface, the chance of failure is reduced.