Insights into the pumping behavior of sealing counterfaces using continuous logging

Surface structures of the sealing counterface are called “lead structures” when they have the capability to pump oil rotation dependent through the sealing contact of a rotary shaft seal systems. This feature is called “pumping effect”. The structures interrupt the equilibrium state of the sealing system, which may lead to dry run or leakage as failure result. Especially for higher circumferential velocities the pumping effect increases and therefore cannot be neglected. To assess the influence of lead structures on the sealing system, one can measure the pumping rate of the sealing counterface experimentally. The higher the pumping rate of a sealing counterface, the more likely the sealing system will fail. In this paper, the development a new pumping rate evaluation method with the help of a continuously measuring scale, which allows to visualize the course of the pumping rate over time, is described. With this knowledge it is possible to determine the end of the running-in phase of the sealing ring and to determine the minimum duration of the pumping rate tests. The pumping rate evaluation method is demonstrated with different shaft counterfaces to validate the stability of the new method.