This paper investigates the impact of the face waviness and pressure inversions on the leakage and on the outer fluid entry of mechanical face seals using a numerical model and an experimental setup. The numerical model couples a transient Reynolds equation, an analytical contact model, a force balance solver, and a solver for the thermo-mechanical deformations. The experimental tests on a face seal with low waviness and on a face seal with high waviness provide leakage and outer fluid entry data, which are reproduced by the model. Contrary to the face seal with low waviness, the face seal with high waviness has poor performance and the pressure inversions increase significantly the ingression of outer fluid. The parametric study shows a decrease of leakage with increasing spring force, and an increase of leakage and outer fluid entry with increasing values of waviness amplitude. The higher leakage observed for wavy seals is shown to be due to the higher average film thickness, and to some extent due to the mechanisms associated with waviness: hydrodynamic pressure generation, film squeeze and stretching.

This paper investigates the thrust exerted on a vessel as a result of axial rupture, which has not previously been examined theoretically or practically. A simple model is developed to predict the peak thrust when the breach is large, that is when the fracture is propagating with constant velocity and the maximum rate of separation of the free edges downstream of the fracture tip has been achieved. The model assumes that the depressurization process within the breach zone is dominated by the transverse rarefaction wave initiated by the arrival of the breach as it advances along the vessel. The prediction is compared with a measurement made during a burst test on a large air-pressurized steel vessel. A novel measurement technique employed an inverse Brinell hardness test, in which the indentation size was used to calculate back to the force that produced it. This was interpreted with the help of a finite element computer simulation of the indentation process.