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RE: [PSUBS-MAILIST] Hull Penetration and Reinforcement
Jon, I don't have the Steel vessel rules. I guess I can download them.
However Section 6.7 Reinforcement states that reinforcement ---"for external
pressure need only be 50% of that required by the rules"----
ASME is considered more conservative I believe and that was more familiar to
me. I am a bit remiss not following up on the Steel Rules tho.
I am afraid I cant keep on with finalizing this thread at the moment as I
have a bit on. As you say my spreadsheet requires knowing what is going on.
I was not suggesting that mine should be used and it is easy to change that
to make it more idiot proof. I have updated mine since I sent you it with a
few conditional alarms but it does need tidying up. References limits etc.
I did warn you that my spreadsheets are a bit messy as I am the only one
using them at present. Regards, Hugh
-----Original Message-----
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Jon Wallace
Sent: Tuesday, 6 April 2010 3:47 p.m.
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Hull Penetration and Reinforcement
Hugh,
Thanks for that reference. Using ASME F=1 and 50% reinforcement equals
ABS F=.5 and no reduction of reinforcement. So the reinforcement area
calculated by both ASME and ABS equal each other. However, with F=1 the
A1 calculation evaluates to 0 when the hull thickness and required hull
thickness are the same. This makes the ASME calculations much more
conservative than the ABS calculations.
Going back to the K350 conning tower example, ASME would require a
minimum thickness of 1.17 inches according to your spread sheet. Using
ABS calculations, the minimum thickness is .69 inches, however that's
for a hole up to 18 inches in diameter (in the case of the K350).
Kittredge used 3/4 inch material for the K350 which represented an
additional 19% of reinforcement to compensate for the larger size hole
(24.5 inches).
Do the ASME rules have similar wording to ABS 4-4-1A1/7.1.1?
The reinforcement requirements apply to openings not exceeding the
following dimensions.
- For shells 1525 mm (60 in.) diameter or less, 1/2 the shell
diameter but not over 508 mm (20 in.).
Can you check Line 25 in your spread sheet "Ring Height Actual"? This
has no limit associated with it even though Line 15 "Total Height of
allowable reinforcing" has a limit associated with it. So for example,
in the case of the K350, if I change Line 25 to nine inches, Line 32
"minimum thickness" drops from 1.17 inches to .16 inches. According to
ABS the thickness of the nozzle can never be less than (Tr) the required
thickness of the pressure hull.
One last thing, I don't see a value in the spreadsheet for the nozzle
material that penetrates inside the pressure hull. Does ASME allow for
that?
Jon
Hugh Fulton wrote:
> Jon, Extract from ASME 8 div1 UG37.
>
> (d) Design for External Pressure
> (1) The reinforcement required for openings in
> single-walled vessels subject to external pressure
> need be only 50% of that required in (c) above,
> where tr is the wall thickness required by the rules
> for vessels under external pressure and the value of
> F shall be 1.0 in all external pressure reinforcement
> calculations.
>
> Regards, Hugh.
>
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