RE: [PSUBS-MAILIST] gas piping through hull

Antoine,

Another option would be to use "thread-o-lets" which are forged pipe fittings with female thread that are welded on the side of hull. A hole is drilled through the hull prior to welding on the thread-o-let. There would be two thread-o-lets, one for each side. 3000 and 6000 psi thread-o-lets are readily available as they are used extensively on process vessels and connections for instrumentation on pipes. They are approved for ASME pressure vessels. I used 3000 psi thread-o-lets for all of the thru hulls on my boat. The advantage of a thread-o-let for a welded pipe nipple is that the joint is stronger and treads are protected.

Cliff

----- Original Message ----
From: Antoine Delafargue <antoine.delafargue@gmail.com>
To: personal_submersibles@psubs.org
Sent: Saturday, January 12, 2008 10:50:36 PM
Subject: [PSUBS-MAILIST] gas piping through hull

Hello,

I am struggling on the design of gas piping through hulls for my 1atm 1 person sub project, if anyone could help:

-What is the best way to design gas through hulls (as close as ABS standards as possible) ?

a) the one I am considering: circular thick SS plate welded on the end cap with various holes (O2, MP air, MBT, snorchel/vent) machined in it and threaded for setting ball valves directly on it. (actually 2 plates for full redundancy). that s the "threaded" i don t like.

b) same SS plates but swagelok tubes welded on it and connected to the valves. that s the "welded" i don t like

c) same SS plates with machined holes, filled with some off the shelf gas through hulls, linked to tubes and valves. not as simple: it implies a seal between the SS plate and the through hull.

d) individual off the shelf gas through hulls welded on the hull. But I could not find a reference in the Swagelok catalog.

e) other suggestion...

Thanks a lot,

Antoine