Mechanical seal

A bellows mechanical seal comprising:

• a seal ring;
• a collar attached to the seal ring through a bellows;
• a mating ring slidably contacting the seal ring;
• and
• a secondary seal configured to seal a gap between the collar and a rotary shaft or between the collar and a housing,
• wherein the collar has, at a first end thereof in an axial direction a restriction piece extending toward at least one of an inner diameter side and an outer diameter side and, at a second end thereof in the axial direction, threaded screw holes extending in the axial direction,
• the bellows mechanical seal further includes an adaptor which is attached to the collar, whose axial movement is restricted by the restriction piece, and which extends to the inner diameter side or the outer diameter side over the restriction piece,
• the collar and the adaptor define at least part of a housing space having the secondary seal housed therein, and
• the collar is fixed to the housing or the rotary shaft by screwing each of set screws into each of the threaded screw holes, whereby to bring the restriction piece into contact with the adaptor and by moving the collar and the adaptor in a same axial direction in a state in which the adaptor and the secondary seal are fitted on an outer periphery surface or an inner periphery surface of the collar and sandwiched between a housing side member or a rotary shaft side member, the housing side member being the housing or a member fixed to the housing, the rotary shaft side member being the rotary shaft or a member fixed to the rotary shaft.