Leakage Model of Tubing and Casing Premium Connection Based on Sinusoidal Contact Simulation between Rough Surfaces

Abstract

This paper proposed a semi-theoretical model to quantitatively predict leakage rate of tubing and casing premium connections. The geometric parameters of the sealing surface profile approximated by a sinusoidal micro-convex surface were first obtained based on the random normal distribution sampling method. With the actual area prediction formula for elastic–plastic contact of an axisymmetric sinusoidal micro-convex body based on the equivalent simulation principle, the circumferential leakage width and radial average leakage height of the micro-leakage channel between sealing surfaces were then acquired with the surface roughness and geometric mean contact pressure. At last, the actual micro-leakage rate of the premium connection was derived by considering the non-uniform contact pressure distribution between sealing surfaces. An example was investigated to validate the model and reveal the sealing and leakage characteristics, and anti-leakage measures were proposed. The results show that average contact pressure, circumferential leakage width, and radial average leakage height between sealing surfaces were non-uniformly distributed. The leakage rate of a premium connection decreases exponentially with an increase in radial interference between sealing surfaces. In order to reduce leakage rate, it is beneficial to increase radial interference and lower sealing surface roughness.

Modeling Surface Roughness and Flow of Gases in Threaded Connections to Analyze Sealing Performance

“…The first is contact analysis between rough seal surfaces. The generation of surface roughness can be achieved through statistical models [16,17], fractal models [18,19], and deterministic models [20,21]. The contact of rough surfaces can be solved by either theoretical calculation [16,20] or numerical simulation [22].…”

Finite-Element Analysis on Energy Dissipation and Sealability of Premium Connections under Dynamic Loads

“…Li et al [5] used a combination of experimental and theoretical research to study the friction characteristics of bolted connection interfaces. Xu et al [6][7][8] used a combination of finite element simulation and theoretical models to calculate the contact pressure and contact area of the sealing surfaces, taking into account the micro profile of the sealing surfaces. The relationship between the average contact pressure, circumferential leakage width, and sealing surfaces was obtained.…”