Patent ID: 8714907

Claim:
A shaft seal for sealing a gap of a penetration of a shaft through a casing, wherein in an interior of the casing there is a process fluid under a sealing pressure and outside the casing there is an ambient fluid under an ambient pressure, the shaft seal comprising: a fluid feed; at least one fluid drain; and a plurality of sealing modules, comprising: an outer main seal; and an inner main seal, wherein between the inner main seal and the outer main seal, a provision is made for a first fluid drain of the at least one fluid drain, via which first fluid drain a first drain fluid is discharged, and wherein the inner main seal is a radial double seal defined by a first gas seal and a second gas seal, each of the first and second gas seals comprising: a sealing surface pair formed by a rotating sealing surface and a stationary sealing surface; a sealing plane, wherein the sealing surface pair is oppositely disposed in the sealing plane, wherein the sealing plane of each of the first and second gas seals essentially has a radial extent in relation to the shaft, and wherein the sealing surface pair of the first gas seal is located at a larger radius than the sealing surface pair of the second gas seal; and a common carrier to which the stationary sealing surface and the rotating sealing surface are fastened to, wherein the stationary sealing surface and the rotating sealing surface are elastically tensioned towards each other by the common carrier being pretensioned by an elastic element, wherein between the sealing surface pair of the first gas seal and that of the second gas seal, a circumferentially extending sealing fluid chamber is provided which is exposed to an admission of sealing fluid via a sealing fluid feed.