Re: [PSUBS-MAILIST] Through Hulls

[jbarlow@bjservices.ca]

     I am in the business of building inline pipeline inspection tools,
(which requires holding external pressure out of a canister, not unlike a
ROV, etc) and we have some success building cable passes with swage-lok
(flare) fittings but if I were to climb inside I would purchase connectors
from SEACON, Impulse, Kemlon, or some other such manufacturer.  They are
rated to 5000 - 10000 psi and experience has shown that they are much more
reliable than they sort you describe.  We only use those for silicon oil
pressure balanced applications now.
     If the wrong sort of cabling is used then the swage fitting itself
could leak.  Or if the outer insulation of the cable becomes damaged then
external pressure (sea water) can move inside the cable through the
bulkhead to inside the hull.  The electrical function of the cable may or
may not be affected.   However any leak that would happen would likely only
be small, that is true.  With a commercial bulkhead connector if the cable
becomes damaged the pressure integrity of the vessel remains unaffected.

     It is also true that you can build a shaft seal using leather packing,
but I would recommend using an O-ring or some other such commercially
available and proven method.

As for the hydraulic vs electrical "debate", I (and I suspect Gary) was
only trying to say that there are some advantage to hydraulic power and/or
propulsion, perhaps it should not be dismissed completely.  especially for
limited service components such as bow thrusters, etc.  Electric servos
would certainly do and be much simpler for some applications.  I think that
blanket statements about what is right and what is wrong are misleading and
perhaps each application should be looked at separately to find a  correct
solution for each problem.

As for making your own thru-hull penetrations then using hydraulic fittings
and hose  which the wires are runs through would perhaps be an acceptable
method.  We have used that method in the past with considerable success,
and even used the hose as a coupling to pull a multi-bodied tool.

I hope I have offered some thing useful to the discussion.


Thanks,
Jay.




|--------+------------------------------------->
|        |          Dan h <machine@epix.net>   |
|        |          Sent by:                   |
|        |          owner-personal_submersibles|
|        |          @psubs.org                 |
|        |                                     |
|        |                                     |
|        |          21/11/2002 07:00 AM        |
|        |          Please respond to          |
|        |          personal_submersibles      |
|        |                                     |
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  |      To:     PSUB <personal_submersibles@psubs.org>                                                                                        |
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  |      Subject:     [PSUBS-MAILIST] Through Hulls                                                                                            |
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Gary and Walter

I think most of us get and understand the points discussed by both of
you.  I, although not an expert with credentials, agree with you both.
I find the discussion interesting but the point of blanket statements
has run it's course.  What I would really like to hear from you guys is
more "tech talk."

Walter     A description of how you design your through hull electrical
connectors, what type of cable is better and for what reasons would be
vary helpful to many of us in here.  This would be of far more use to us
amateurs.   Please describe how you recommend building an electrical
through hull.

And Gary    Although I'm not propelling my sub with a through hull
shaft, I can't see the complexities of a straight shaft design.  It
seems that a good face seal, with maybe a backup seal as a safety
measure, would be simple, cheep and safe.  My sub is using motor pods
with HP shaft seals and are not pressure compensated.  I have three
motor pods, each with a shaft seal.  I like this design but do think
that one straight shaft would have been much easier and just as safe
although not offering the same control.  Why is a straight shaft
something to be avoided?  Your thoughts please.

Thanks guys,
Dan H.