Redundant Linear Seals-A Selection Criterion

Leakage from the linear rod seals of hydraulic cylinders may be controlled by placing additional seals downstream of the primary seal and introducing controlled pressure in between the seals. This technique is called the ‘biasing method' and was developed at the Fluid Power Research Center at Oklahoma State University (FPRC/OSU). The controlled pressure modifies the distribution of stress in the seal at the rod-seal interface. The result is a modification in the distribution of pressures in the films of leakage fluid which form between the rod-seal interface. By controlling the fluid film pressure distribution, the volumes of leakage fluid which pass between the rod-seal interface may be controlled to any desired extent.

The theory behind the biasing method is explained and experimental evidence of its effectiveness in controlling external leakage from linear rod seals is presented.