ASME Code for Pressure vessel Caps 2

[Ahmed Zeid]

Hello all,

I am working on a project where I need to design a pressure vessel (7000 psi). The vessel is to be closed from the top using a threaded cap (something like a bolt with a much wider head). I was told that there's an ASME code for such part. Anyone knows what is the full name of the code or where can i find it?

Thank you.

 

[XL83NL]

ASME Sec VIII Div 1 would govern the design of pressure vessels (though at 7000 psi you seem to come into the realm of ASME Sec VIII Div 2). In the ASME VIII sections you'll find the applicable paragraph with the design formulae/requirements for your head. A head could be made of a pipe cap to ASME B16.9, but those don't come threaded. If the vessel is really small, I could imagine the cap being made to an ASME B16.11 cap, but then the head is more like a plug (depending if you need in or external threads).
Can you share a bit more details on the vessel? Size, global layout, material, temperature, etc. ?

Huub

 

[Ahmed Zeid]

Thank you for your reply XL83NL,
Attached is the cross section view of my vessel(The threaded cap is the one on top). Wall thickness of 1.7 in, internal diameter of 1 in and a total height of around 8 in. The material is A514, and temperature can go up to 600F.

(Please ignore the outer cover, that's just a threaded tube to cover the vessel.)

Based on that, which code do you think i should be using for this case?

 

[SnTMan]

Ahmed Zeid, based on the dimensions given, it is not likely that your vessel falls within the scope of any US pressure vessel Code. You would have to check with the jurisdiction in which it will be installed and operated if they require such a vessel to be a Code vessel.

That said, you can design to any Code you wish. Note that your design may not be addressed explicitly by the Code of your choice. Instead it likely falls under "good engineering practice" provision of said Code.

It appears to me that your chosen material A-514 is not recognized by ASME pressure vessel Codes. As such, allowable stress at the design temperature is not tabulated in these Codes.

As XL83NL says, you may find standard threaded fittings useful, although you would have to satisfy your self in some way they would meet your design conditions.

Although your vessel is small, I'd personally not plan on sealing that pressure with tapered pipe threads, but with an O-ring or other gasketed arrangement. See the Parker handbook for example.

Regards,

Mike

BTW: Double posting is discouraged.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[Ahmed Zeid]

@SnTMan, Thank you for your reply.

It's not a constraint that my design should be ASME certified, but as you mentioned it's more of a good practice. I already designed my vessel using ASME Sec.VIII Div.1 . And i believe i will be using B16.11 for my cap design as proposed by @XL83NL. And yes, the cap would also have an O-Ring in addition to the thread for a better seal if that is what you meant. Thanks for the Parker handbook suggestion, i will check it out.

My apologies for double posting, i didn't know that.

Thank you and Regards,
Ahmed

 

[XL83NL]

With such dimensions, we’ve built pressure vessels in the past using common Swagelok (or any other twin ferrule compression or tubing joint manufacturer, like Parker or Ham-Let) fittings. It’s advantage you don’t need to weld and can use ‘off-the-shelf’ items with a predetermined rating.
I believe you may need a bit of luck sourcing 7000psi O-ring seal fittings though.

Huub

 

[SnTMan]

I used to work with guy who built small vessels for petroleum industry laboratories. 10K psi was routine, sealed with o-rings. Very do-able

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[XL83NL]

Oh sure it’s very doable. We’ve done higher pressures and higher temperatures on O-rings. The trick is making it safe and cheap. Custom machining allows virtually anything. Buying off the shelf fittings is what keeps your business running if this is your routine work.

Huub