Keywords: mechanical seal, contact stress, heat conduction, sealing, FEM, leakage, fluid pressure, friction heat.

A mechanical seal is one of the sealing techniques and has a sealing face between a primary ring and a mating ring. The contact pressure on the sealing face is caused by axial loads due to both a spring and external sealing fluid pressure, and prevents the leakage of external fluid [1]. The sealing face plays a very important role in a mechanical seal, so it is necessary to obtain an optimum design of it by temperature and stress analyses and experiments.

When a mechanical seal is used under high pressure and temperature, both external fluid pressure and friction heat on the sealing face deform the primary ring [2], which leads to a decrease in the sealing ability. In this paper, the effect of external fluid pressure on contact conditions of the sealing face was investigated. Finite element analyses of coupled transient heat conduction and contact stresses were conducted, in consideration of the friction heat generated on the sealing face that depends on contact pressure, shaft rotation speed, friction coefficient, and elapsed time.

Just after the shaft began to rotate, temperature and contact stress of the primary ring increased near the outside diameter. After that, the contact portion moved gradually toward the inside diameter of the primary ring.

In the case of low external fluid pressure, temperature and contact stress of the primary ring increased on the inside diameter. This is because the free end of the primary ring expanded outward by the temperature increase due to friction heat on the sealing face. With an increase of external fluid pressure, a high contact stress position moved toward the outside diameter, and the maximum temperature increased. This is because the external fluid pressure shrank from the free end of the primary ring.

Thermocouples and strain gages were attached on the internal surface of the primary ring near the sealing face, and temperatures and strains were measured. The distributions of measured temperatures and strains at the steady state were compared with those calculated. These results show that measured values are in good agreement with calculated ones, and the validity of this analysis was confirmed.

1

E. Mayer, "Axiale Gleitringdichtungen", VDI-Verlag, 1982.

2

A. Parmar, "Thermal Distortion Control in Mechanical Seals", in Proceedings of 12th International Conference on Fluid Sealing, Paper B3, 109-126, 1989.

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