A mechanical seal device which seals a rotary shaft inserted in processing equipment that performs processing under a sterile condition, and which is provided between an inside of the processing equipment and an outer atmosphere, the device comprising:
- a casing disposed so as to cover a periphery of the rotary shaft that projects from the processing equipment;
- a first slidable sealing member comprising a rotary shaft-side seal sliding surface provided around the entire circumference of the rotary shaft, along a plane intersecting the lengthwise direction of the rotary shaft, and a first casing-side seal surface, provided along the inner circumference of the casing, which slides against the rotary shaft-side seal sliding surface;
- a second slidable sealing member comprising a rotary shaft-side sealing sliding surface, which is disposed at a position distanced from the processing equipment, with respect to the first sliding member, in the direction of extension of the rotary shaft, and provided around the entire circumference of the rotary shaft, along a plane intersecting the lengthwise direction of the rotary shaft, and a second casing-side seal surface, provided along the inner circumference of the casing, so to slide against this rotary shaft-side seal sliding surface;
- a biasing means provided for at least one of the first slidable sealing member and the second slidable sealing member, and biased so as to press one of the rotary shaft-side seal sliding surface and the corresponding casing-side seal surface against the other seal sliding surface, in said at least one of the first slidable sealing member and the second slidable sealing member, so as to make airtight a first space surrounded by the casing, the rotary shaft, the first slidable sealing member and the second slidable sealing member;
- wherein the first and second slidable sealing members are configured to move under pressure differentials against the biasing means to open gaps between the first and second slidable sealing members and the first and second casing-side seal surfaces;
- a sealing fluid supply port provided in the casing to supply sealing fluid to said first space, and to let the sealing fluid flow in gaps between the rotary shaft-side slidable sealing surfaces and the casing-side sealing surfaces in each of the sliding members
- a sterilizing gas supply port provided in the casing to supply saturated steam or sterilizing gas as the sterilizing gas to the first space, and to let the sterilizing gas flow in gaps between the rotary shaft-side slidable sealing surfaces and the casing-side sealing surfaces in each of the sliding members;
- a sealing member which includes a surrounding member and a seal member, the surrounding member surrounding a second space, which is an area that communicates with the gap between the rotary shaft-side slidable sealing surface and the casing-side sealing surface in the second slidable sealing member and is located downstream of the gap in the flow direction of the sealing fluid toward the outer atmosphere, and the seal member sealing an opening between the surrounding member and the rotary shaft to seal off the second space from the outer atmosphere;
- a discharge port opened to the second space for discharging the sealing fluid or the sterilizing gas;
- and
- a pressure detecting part for detecting the pressure of the sterilizing gas in supply lines flowing to the first space;
- wherein the second slidable sealing member is configured as an airtight seal member so that as a result of sterilizing gas in the first space leaking out to the second space via the gap between the rotary shaft-side seal sliding surface and the casing-side sealing surface in the second sliding sealing member, the second area is filled with sterilizing gas at a pre-established pressure for a pre-established set time, so as to sterilize the rotary shaft-side seal sliding surface and the casing-side seal surface in the second sliding member.