In pusher seals the secondary seal
between the shaft or sleeve and the rotating element of the
mechanical seal is achieved by the use of an elastomer O ring
which slides along the shaft to compensate for face wear. These
seals possibly do not tolerate such degrees of misalignment as
bellows type seals, but offer easy replacement of the elastomer
as O rings are easily obtainable worldwide.
The shaft finish requirements to permit the O rings to slide are
generally more demanding than those for bellows seals, but the
pressure capabilities are higher, typically up to 80 bar.
Typical pusher seals are:
John Crane 8-1, 8B1, 58B, 5610, etc.
Flexibox R type
Roten 2 & 3 , Uniten 2 & 3, etc.
