Shaft sealing device

A shaft sealing device that seals a sealed fluid, comprising:

• a mating ring having a sliding surface and attached to a casing into which a rotating shaft is inserted;
• a seal ring having a sliding surface that slides against the sliding surface of the mating ring, and attached to the rotating shaft;
• and
• a backup seal ring attached to the rotating shaft on a counter-sealed fluid side in an axial direction with respect to the sliding surface of the mating ring and the sliding surface of the seal ring, and having a sliding surface facing the sealed fluid in the axial direction,
• wherein the casing is provided with a communication hole configured to communicate with a space to which an outer peripheral surface of the seal ring faces,
• the casing has an inner peripheral surface provided with a groove configured to communicate with the space and extending in an axial direction,
• the groove has a tapered surface which is adjacent to the space and which is increased in a diameter toward the space,
• the sealed fluid is supplied from an outside of the casing to the space via the communication hole and discharged via groove, and
• wherein the backup seal ring is attached to the rotating shaft, by a tightening device by which a tightening force is adjustable, at a position at which the backup seal ring is separated from the mating ring.