Re: [PSUBS-MAILIST] Hull Penetration and Reinforcement

[Jon Wallace <jonw@psubs.org>]

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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