A shaft seal that is slidably mounted in a housing with essentially equal balanced forces acting on each radial side. Fluid from the high pressure side of the shaft is communicated to equal areas on the two sides by ducts and constrained to the design areas by "O" rings. The seal moves radially in response...http://www.google.es/patents/US4494760?utm_source=gb-gplus-sharePatente US4494760 - Pressure balanced floating seal
