|
The meta clad ring
are under shrinkage stress and expand in correspondence to
the coefficient of thermal expansion of the metal holder
material.
The shrink fits
and the shrinking in temperatures have to be selected in
accordance with the maximum
Service
temperature.
Customary shrink
fist and shrinking in temperatures:
H7/z8
350° - 400°C
H7/za8
450° - 500°C
To be observed
when shrinking into meta holders:
Because of
dimensional changes during shrinking in:
-
subsequent machining of the ring bore
-
subsequent machining of thin walled steel holders (~ 0.2mm
oversize for machining)
Wall thickness of
the steel holder: 2-5 % of the outer diameter of the carbon
ring, minimum 2mm.
In most gap seals, depending
on the pressure drop (see design recommendations), several
rings are arranged behind another in
steel or cast iron chamber rings.
Due to the
pressure drop the rings are pressed axially against the face
of a chamber ring resulting in additional axial sealing.
The precondition
is that the chamber face is well mechanical (Rt <=2 )
and as the metal clad x carbon rings are concerned, that the
carbon ring protrudes axially from the metal holder. |
