Dual seal assembly

1. A dual seal assembly, in particular for sealing a gas compressor, comprising:

a first mechanical seal assembly including a pair of co-operating seal rings, one of which is provided for common rotation with a rotating component and the other of which is provided rotationally fixed at a stationary component,

a second mechanical seal assembly including a pair of co-operating seal rings, one of which is provided for common rotation with a rotating component and the other of which is provided rotationally fixed at a stationary component, one of the seal rings being axially movable and axially biased with a biasing force against the respectively other seal ring, said biasing force being transmittable through a force transmitting ring to the respective seal ring, in order to bias facing sliding surfaces of the seal rings, between which a sealing gap is formed during operation, in a mutual sealing engagement, and a secondary sealing assembly for sealing the axially movable seal ring with respect to circumferential guiding surfaces of a guiding component guiding the movement of the seal ring and the force transmitting ring, wherein the secondary sealing assembly is provided at the force transmitting ring and consists a pair of annular sealing members made of an elastic material, said sealing members being retained at the force transmitting ring near its periphery and its end face facing the seal ring such that the sealing members protrude beyond the force transmitting ring at least axially and are movable radially beyond the periphery of the end face due to the effect of the biasing force, such that the annular sealing members are configured to sealingly engage simultaneously with the seal ring and the circumferential guiding surfaces, whereas such engagement is substantially prevented when no biasing force is effective, wherein the axially movable seal ring is devoid of any grooves for receiving sealing members, wherein the circumferential guiding surfaces delimit a guiding ring space therebetween, in which the force transmitting ring and at least an axial portion of the seal ring is received, wherein one of the sealing members is retained near the inner periphery and the other of the sealing members is retained near the outer periphery of the force transmitting ring of the end face facing the seal ring, wherein the one sealing member is configured to sealingly engage with one of the circumferential guiding surfaces and the other sealing member is configured to sealingly engage with the other circumferential guiding surface, while the sealing members simultaneously delimit an axial gap space region circumferentially at the end face, wherein the first mechanical seal assembly and the second mechanical seal assembly are arranged back-to-back.

2. The dual seal assembly of claim 1 , wherein the sealing members substantially have the same cross-sectional dimensions, wherein the cross-sectional centers of the sealing members are arranged on a substantially common radial plane.

3. The dual seal assembly of claim 1 , wherein the force transmitting ring is interspersed with at least one axial aperture, wherein the aperture at one end opens out within the gap space region.

4. The dual seal assembly of claim 3 , wherein at least one flow passage is defined in the seal ring, which at one end opens out at the face end thereof facing the force transmitting ring in alignment with the axial gap space region and at the other end opens out into the sliding surface thereof, in order to supply a flow medium promoting the sealing gap formation between the co-operating sliding surfaces.

5. The dual seal assembly of claim 1 , wherein each sealing member is formed as an O-ring.

6. The dual seal assembly of claim 1 , wherein the rotationally fixed seal ring of the second mechanical seal assembly is axially movable.

7. The dual seal assembly of claim 1 , wherein a spring biasing device for applying the biasing force is provided at the second mechanical seal assembly.

8. The dual seal assembly of claim 1 , further comprising a leakage drain passage which is arranged in the axial direction between the first mechanical seal assembly and the second mechanical seal assembly.

9. The dual seal assembly of claim 1 , wherein the first mechanical seal assembly and the second mechanical seal assembly are identically constructed.