Q&A forum: Pressure Vessel Calculator (ASME VIII)

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I just purchased the pressure vessel calculator, and the external pressure calculation isn't working as intended. no matter how many stiffeners I add, or remove (and increase/decrease cross sectional area) the external pressure stays the same. whether it's 0 stiffeners or 20. there is no change to pressure.

... the way ASME VIII works is that you enter the wall thickness and the number of rings, and the calculations tell you;
a) minimum second moment of area for each ring (Iᵣ), and;
b) the minimum allowable wall thickness (tᵣ) for the specified OD (Dₒ)

I bought your pressure vessel calculator this weekend, and because I’m a Mac user not PC, I sent the download instructions and key to a colleague of mine to use it for me, but he said it didn’t work..
Here’s the email I got from him:

The install went ok. Trying to run gives "incorrect license" and then asks me to call them for tech support.

It appears to be a trap function on a registry key, as there is no ini/config files listed -- ie, no way to fix without investing at least a few hours time. Although cut/past key and business name, apparently if not enter "country" with exact same code as used at registration time, it forces a full fail.

I need to calculate the wall thickness for a 18 inch diameter x 48 inch long vacuum tank made of 304 stainless steel. He suggested I simply ask you to do this for me, email me the answer, and give up on your product and get my money back, unless you can give him a quick solution to making it work, he’s a busy man and barely has time for me. It would be nice if your product worked without this trouble.

Please assist

All our calculators install and operate on private computers (i.e. not on company computers), if the user does not have unrestricted access to the registry file on his computer, i.e. it is being installed on a company machine, it will not work. Companies are expected to pay a higher price for multi-user access

We have sold hundreds of this calculator (Pressure Vessel) for use on private PCs around the world with no problems

I have just successfully installed the program on one of our machines using your security key (************-************) and your names (**** and *******)

When this problem has been (occasionally) reported in the past it has always been as a result of the user incorrectly applying the security details.

I am unable to locate an ASME Code Division 1 nominal definition for the external pressure strain Factor A. Several formulas are presented for differing design conditions, none of which correspond to the Calqlata website equation (see below). Please provide a citation for your published equality:
'A' is normally defined by ASME as; 0.125÷(Dₒ/t)

When ASME VIII was first drawn up for internal pressure vessels (1960s), their materials test engineers selected and tested a number of suitable carbon and alloy steels. Stress-strain (B-A) curves were generated for each of the selected metals and published in the Code, along with associated linear interpolation Tables.

In the early "Noughties" ASME decided to digitise their Code, but mathematical interpretation of all the stress-strain curves proved difficult, so they dropped the curves and relied solely on the nominal formula, which originally only applied to internally pressurised vessels (and quoted by your enquirer).

I, on the other hand, did mathematically interpret all of the original curves and included them in my calculator (see Technical Help for the calculator; Fig 5), hence the purpose of my graphs.

So, the formula for 'A' in my calculator is as ASME always intended for internally pressurised vessels.
But for externally pressurised vessels, the formulas in my calculator are according to the original material test charts.
I am not a great fan of short-cuts and approximations.

All of this, is of course explained on the Technical Help page for this calculator.