[PSUBS-MAILIST] Fw:

[Sean T. Stevenson via Personal_Submersibles]

I would suggest characterising this exactly - do you have access to ultrasonic measurement? With the halves already welded, getting a caliper in might be tricky.

Use a template to measure the out-of-round deviation in the worst possible plane. (Radius to match your design outer radius, subtending 120° of arc) If the radial distance between the template and the shell surface never exceeds 1/2 percent of the overall diameter at any point, then you're good to go. Just locate and measure the minimum shell thickness and use that measurement to determine the maximum allowable working depth.

Looking forward, it's probably worth having a chat with someone at EE to explain why sphericity is critical, and seeing if they can accommodate you. They probably don't deal with many externally pressurised vessels, so e.g. additional press steps may be within their capabilities, but just not have occurred to them to do.

Personally, I hate talking to people on the phone, so I create engineering drawings which are exhaustively toleranced, such that there is no way a supplied part could comply with the drawing and not be suitable. If a part doesn't meet the spec, I don't accept it.

Sean


On October 24, 2015 7:11:09 AM MDT, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>Sean,
>I would say just out of round, very slightly.
>Hank
>
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