Mechanical seal arrangement

A mechanical seal arrangement for sealing a process chamber, which is filled with a non-toxic gaseous process medium, with respect to a bearing chamber, comprising:

• a first mechanical seal with a rotating slide ring having a first sliding surface and a stationary slide ring having a second sliding surface, which define a first sealing gap between the sliding surfaces;
• a second mechanical seal with a rotating slide ring having a third sliding surface and a stationary slide ring having a fourth sliding surface, which define a second sealing gap between the sliding surfaces;
• a first pretensioning device which prestresses the stationary slide ring of the first mechanical seal in the axial direction (X-X);
• a second pretensioning device which prestresses the stationary slide ring of the second mechanical seal in the axial direction (X-X);
• a fluid chamber arranged between the first mechanical seal and the second mechanical seal, which is in fluid connection with the first and second sealing gap and, during operation, receives leakage from the process chamber via the first sealing gap, and from which a return line leads off, configured for a return of process medium from the fluid chamber to a process area;
• wherein the first mechanical seal and the second mechanical seal are arranged such that a rear side of the stationary slide ring of the first mechanical seal and a rear side of the stationary slide ring of the second mechanical seal face each other,
• wherein the stationary slide ring of the first mechanical seal comprises a first step on the inner circumference such that a minimum first inner diameter D1 of the stationary slide ring of the first mechanical seal is smaller than a maximum second inner diameter D2 of the stationary slide ring of the first mechanical seal,
• wherein the stationary slide ring of the second mechanical seal comprises a second step on the outer circumference such that a minimum first outer diameter D3 of the stationary slide ring of the second mechanical seal is smaller than a maximum second outer diameter D4 of the stationary slide ring of the second mechanical seal,
• wherein the first sealing gap of the first mechanical seal is open in a non-operating state of the mechanical seal arrangement, so that the process medium can flow from the process chamber into the fluid chamber via the open first sealing gap,
• and wherein the second sealing gap of the second mechanical seal is closed,
• and wherein a first leakage direction in the first sealing gap extends from the outside from the process chamber inwards to the fluid chamber and a second leakage direction in the second sealing gap extends from the inside from the fluid chamber outwards to the bearing chamber.