© Valeport Limited
M
IDAS
WLR Hardware Manual
Page 17
0730877D.doc
4.2.2
ANTI-EXTRUSION RINGS
It is common Valeport practice to fit Anti-Extrusion Rings, also known as AE Rings or
Backing Rings, to o-ring seals on deep water instrumentation.
The function of an AE Ring is to prevent the o-ring from being squeezed out of its
groove under high pressure. Whilst this may not immediately cause a leak, it can
damage the o-ring to the extent that it will not properly seal on subsequent
deployments.
Where an AE ring is fitted, Valeport favour a single solid ring type made
from nitrile rubber. These are black or dark grey in appearance, and are
distinguishable from the o-ring itself by having a square cross-section, with
a single concave surface, as illustrated:
These rings should be fitted into the o-ring groove on the “dry”, or low pressure side of
the o-ring, with the concave surface adjacent to the o-ring itself:
It is particularly important to note that in order to fit these rings, they must be stretched
slightly to pass over the instrument body. This stretch does not immediately recover,
with the result that the AE ring may not sit snugly in the groove at first. Fitting the tube
to the instrument at this point may result in the AE ring riding out of the groove, and
preventing a proper seal. The instrument may then leak.
Once an AE ring has been fitted, please leave a minimum of 30 minutes
for it to recover its shape before fitting the tube.
Water
