[PSUBS-MAILIST] On sub rescue....

[Phil Nuytten <pnuytten@compuserve.com>]

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Hi, Chris:
        When a rescue sub such as DSRV or REMORA mates with a DISSUB, the
mating surfaces are not 'mirror' smooth. The mating suface has to be clean
and have no obstructions that would prevent mating - (wreckage, lines,
etc.,) but the seal is made by a resilient polymer gasaket - usually a
round configuration. Please do note that it's not the 'smooch' of the
sealing ring to a smooth surface that actually makes the seal, but the
sealing ring being forced to try to squeeze through a crack too small for
it to pass by the internal/external pressure differential ( same as any
properly designed face seal). Because of the area of  the manway nozzle, it
doesn't take much depth for the sealing forces to reach many thousands of
pounds ( total area X press. diff)  For example. at a  depth of a thousand
feet the total force on a six inch diameter joint on a Newtsuit or a Wasp
is 12,500 pounds. Once the two surfaces are mated and the slightest of
pump-down started, it's impossible to move the pieces relative to each
other - Thats why the REMORA ( which has a patented articulating conduit,
to enable parallel- plane mating at DISSUB mismatch angles of more 45
degrees) must align the two surfaces before touching down or beginning to
pump-down The DSRV or REMORA system use a fast pump-down to get an initial
seal - then must have a gas make-up system to replace the water being
pumped out, whilst still maintaining  a. one at to abient pressure
differential.
Yeh, I know . . .if it was easy - everybody'd be doin' it!
Phil Nuytten
 





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