An investigation on the lubrication mechanisms of the mechanical radial face seals - II: hydraulic balance of the ring

摘要

Purpose - The main purpose of the research work carried out is to investigate the hydraulic balance conditions of the sealing ring of a mechanical radial face seal in terms of the residual load acting on the ring by employing the theoretical model developed mentioned in the first part of the investigation. Design/methodology/approach - The end load balance conditions for the movable seal ring have been examined by considering the residual load acting on the ring under all running conditions. The main lubrication and sealing mechanism is assumed to be due to the existence of the relative tilt between the mating surfaces, which is formed by the bearing misalignment. The aim of the theoretical model developed is to predict the necessary minimum film thickness between the relatively moving surfaces by considering the non-dimensional running (operating) conditions and the geometrical parameters defined. The theoretical model is based on the main differential equation (Reynolds' equation) which is achieved by adopting the standard finite difference form. Findings - Under the combination of the hydrostatic clamping forces and hydrodynamic restoring forces, an equilibrium position is reached with the seal ring displaced from its central position. At a particular non-dimensional pressure, the seal ring comes into contact with the stationary plate and this limits the upper value of pressure that can be resisted by the mechanical seal type examined without metal-metal contact. With the theoretical model developed, it was found that the minimum film thickness between the realtively moving surfaces could be predicted. Originality/value - This paper provides a considerable scientific contribution to the field of lubrication and sealing aspect of the mechanical radial face seals. The results presented in the first part of the investigation and the remarks outlined in this paper would be considered as a design tool for the seal designers with special reference to ring behaviour under hydrodynamic and hydrostatic conditions.