Re: [PSUBS-MAILIST] Spherical and Elliptical heads

[Jon Wallace <jonw@psubs.org>]

Hi Brian,

Lines 21 and 41 can be thought of as your safety margins, and at the 
default setting of .67 the calculator is giving you a 1/3 margin.  You 
can adjust these numbers up or down (maximum value of "1"), to find the 
max PSI for various safety margins.  If a higher safety margin (a lower 
"n" value) reduces the max PSI to a depth less than you want to achieve, 
you have to increase the tank head thickness to maintain that safety margin.

For tank heads, decide up-front the diameter, max water depth (using 
PSI), and safety margin you want and then enter these parameters into 
the calculator.  Then simply adjust thickness ("t" on lines 15 and 34) 
to get you at or above the PSI parameter you decided upon.

One other note with tank heads is that they vary in thickness due to the 
manufacturing process.  Always specify your required thickness as the 
"minimum" thickness when you order it.  You may find that in order to 
ensure your minimum thickness requirement, the tank head has to be 
formed out of a thicker plate.

Jon


Brian Cox wrote:
> Thanks, much better.
>
>   Do we not need to fool with line 41 -( n= for max allowable working
> pressure for head  - .67) ?
>
> Brian
>
>   




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