ABSTRACT
This chapter considers factors affecting the selection of hydraulic seals, the design of the seal and its envelope, and the physical sealing mechanism. An understanding of these, and the limits of hydraulic sealing technology, should prevent the designer of hydraulic equipment from calling for the unattainable. Because leakage from the cylinder rod escapes to the environment, the reciprocating rod seal is one of the most critical elements in hydraulic equipment. A leaking rod seal can cause operational problems and environmental pollution. The dynamic sealing mechanism, and the lubrication, of a hydraulic rod seal is governed by the behavior of hydraulic fluid drawn by the moving rod into the seal contact. Hydraulic seals were made long before the seal manufacturers knew the details of the elastohydrodynamic sealing mechanism. A compromise must be achieved between the aims of dynamic sealing and good lubrication. This requires formation of a film, not too thin, on the outstroke, and good return pumping ability.
