Cover plate gaskets0 pages

Cover plate gaskets

Cover plate gaskets are used as self-sealing gaskets, meaning that the sealing force does not come from bolts but from
the internal pressure. Therefore bolts with a smaller crosssection can be selected. The entire connection is more compact. The following illustration shows the design principle.

When new, the gap should be as narrow as possible. The
specified fit tolerance can be used as an indicator. The selection and model is left to the equipment manufacturer.
Diameter d2

Fit tolerance dG/dV

d2 < 500 mm

D9/h8

d2 > 500 mm

E8/h8

The cover plate can be tilted by 1° or 2° as shown in the
illustration, for ease of fitting.
Cover plate gaskets have a rectangular or an internally (less
often, externally) sloped cross-section. There is a range of
profiles in seven different shapes available, with which all
sealing problems can be solved. The necessary deformation to conform to the sealing surfaces is achieved with the
cover tensioning bolts.

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When laying out the bolts, attention should also be paid to
the weight of the cover and where it is to be installed. Depending on the type of profile and the geometry of the gasket,
achieving sufficient deformation will require the correct level
of surface pressure and/or the correct internal pressure.
At high pressures or with reworked covers, caps should be
provided, so that the graphite does not extrude into the gap
between the housing and the cover plate. Compressed caps
are made of 0.4 mm thick stainless steel sheet metal 1.4541.
At very high pressures solid, lathed caps are usual.

Indicative values for maximum bridgeable gaps:
b [mm]

5

10

15

20

30

40

s [mm]

0,4

0,6

0,8

1,0

1,2

1,3

Gap width s is the average gap as shown in the illustration.

The minimum pressure required for a self-sealing connection is given as pkrit. Where d1=internal diameter and d2 =
external diameter of the gasket, and the sealing factor is K,
the following is true:
pkrit = K • ( 1 -

d1
d2

) [N/mm2]

The sealing factor K was established in tests and can be
taken from the table on the following page.
The maximum permitted operating or test pressure can also
be estimated from the critical pressure. The selected tolerances and the presence or absence of metal caps or lathed
protective caps is of critical importance.

The following gives an indication:
Pressure

Model
pmax < 3 · pkrit

without caps

3 · pkrit <

pmax < 6 · pkrit

with metal caps

6 · pkrit <

pmax < 12 · pkrit

with lathed steel cap

Kempchen Dichtungstechnik GmbH · Tel. +49 (0)208 8482 0 · Fax. +49 (0)208 8482 285 · info@kempchen.de · www.kempchen.de

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Cover plate gaskets