MIDAS SVX2 Combined SV and CT Profiler - Operating Manual
MANUAL-1553401442-1 | issue: 1.5
Page | 15
©
2022
–
Valeport Ltd
4.2.1 O-Rings
To help preserve the watertight nature of the equipment, please observe the following guidelines:
•
Ensure that all o-rings are free from cuts, abrasions or perishing.
•
Ensure that all-o-rings are free from dirt, grit, sand, hair and other foreign objects.
•
Ensure that an anti-extrusion ring is fitted on the low pressure side of each o-ring (see
Section 4.4.2)
•
Whenever an o-ring seal is opened (e.g. when changing batteries), ensure that a light
coating of silicon grease is applied to the o-ring before the seal is closed.
•
Ensure that all o-ring protected seals are tightened.
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 Anti-Extrusion ring has been fitted, please leave a minimum of 30 minutes for it to
recover its shape before fitting the tube.