external pressures on vacuum vessels 3

[mjduff]

I have been asked to build a vessel out of 30" schedule 40 carbon steel pipe, that will be 36" tall and sealed at both ends. The cylinder will be placed under a vacuum in excess of 29" hg. at an operating temperature of less than 200 degrees c. Even if an absolute vacuum could be achieved, the external pressure would never exceed 15psi at sea level. The wall thickness of the pipe is 3/8" and I would think it capable of handling such a load, but I can not find a formula to prove it to myself. Your comments would be appriciated.

 

[TGS4]

Check out Section VIII, Div.1 - pay special attention to articles UG-28. Please note that if you are designing a pressure vessel, you'll need to follow ALL of the requirements of Div.1. Making a vessel out of pipe is perfectly acceptable.

 

[codeeng]

Your 36" pipe is good for full vacuum regardless of length based on using no more than 1/16" corrosion allowance. You can check it out using UG-28 as TGS4 suggests.

 

[codeeng]

Sorry that's 30" pipe.

 

[pennpoint]

mjduff
Be sure of your materials specification. I have designed a built many vacuum vessels. None used carbon steel, all were fabricated of 304 Stainless steel. Based upon your inital statements .375 is more than enough wall thickness, however do consult with ASME Section VIII, Div.1 with sub paragraphs as suggested by "TGS4" and "codeeng". If this is for an aerospace application it will not be acceptable if carbon steel is used.
Be sure.

Best regards
pennpoint

 

[unclesyd]

What type of end seals are you going to use?

 

[Artisi]

I know from experience and cals (using Australian test code for pressure vesels) that this pipe selection will be ok, however you need to look at the vessel end covers.
You should also recheck yourself using the code appropriate to your own country as you are the designer and need to document your calculations - as pointed out by others.

Naresuan University
Phitsanulok
Thailand

 

[TangoCleveland]

You mentioned that the pipe was 30" Sch 40. That's not a 3/8" wall thickness. For 3/8" wall on this size, the designation is "Standard Weight". My pipe tables don't call out Sch 40 for 30", but they do show 30" sch 20 as 0.500" wall.

Larry