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Pressure Vessel - Flat Plate thickness at Pipe Ends

Pressure Vessel - Flat Plate thickness at Pipe Ends

Pressure Vessel - Flat Plate thickness at Pipe Ends

(OP)
Recently my company has moved towards building non-code pressure vessels which we have previously had supplied by an outside vendor. The vessels will consist of 1", 1.5" or 2" SCH. 40 carbon steel pipes (1.315", 1.9" and 2.375" OD, respectively) and flat end caps (also c. steel) welded to each end. The rest of the unit is rated for 300 PSI at 400*F, so those are the conditions we need to be prepared for.

I would like to know what ASME code requires for the thickness of this plate, and, if different from code, what thickness would be sufficient for a non-code vessel.

I do have a copy of Roark in the mail so that I can confirm all these calculations myself when it arrives, however in the interest of time any insight you could provide would be very helpful.

Thanks all,
Andrew Wells

RE: Pressure Vessel - Flat Plate thickness at Pipe Ends

What strength "carbon steel" are you going to use for your stress cal'c?   

What spec of pipe material?    

RE: Pressure Vessel - Flat Plate thickness at Pipe Ends

Hi Andrew,
You can design the 'vessel' in accordance with ASME VIII-1, use UG-34 to calculate the flat ends. The ASME code does not advise thickness of the non-code vessel components. Just take notice that the Roark's calculation has to include the pressure vessel code safety margins in order to compare them (apple for apple, vessel for vessel).
Cheers,
gr2vessels

RE: Pressure Vessel - Flat Plate thickness at Pipe Ends

If the plates are welded on the ends of the pipe, do you need to do any testing for laminations in the plate?

RE: Pressure Vessel - Flat Plate thickness at Pipe Ends

(OP)
Thanks for the replys, everybody.

racookpe1978, I'll head out to the shop and find out exactly what strength carbon steel and grade of pipe we have available. I was planning on using a "general" value of 27,000 ksi for the maximum stress, along with a safety factor of 1.6 or two, depending on how everything turns out.

gr2vessels, I do not currently have access to any ASME code publications, however I appreciate the tip and will be sure to include a healthy safety factor in my calculations.

moltenmetal, I'm not 100% sure what you are asking, however we are using non laminate pipe so I don't believe that will be an issue.

RE: Pressure Vessel - Flat Plate thickness at Pipe Ends

The laminations would be defects in the PLATE, not a feature of the pipe.  Think of a bad piece of plate as sheets of paper, with most of them glued together but not all of them completely glued together.

I don't know much about this, but do know that you are not permitted to make a hubbed or weld neck flange out of plate without additional testing of the plate prior to machining- otherwise you are required to use a forging. Using an untested plate for that type of flange, unlike a blind flange, would potentially put lamination flaws in tension.  

The same would seem to be true if you just set on and welded a plate to the end of a piece of pipe and called it a flat unstayed head.  

Now if you set the plate INTO the end of the pipe and did a full pen groove weld there, you would not need to worry about laminations in the plate.  The plate would be supported all around its edge through its entire thickness.  More work, granted.

My question is a code question, to those in this group who have ASME VIII tatooed to the inside of their eyelids (and there are MANY such experts here- I am definitely not one of them!).

RE: Pressure Vessel - Flat Plate thickness at Pipe Ends

Welded pipe caps are not very costly in small sizes and would look snazzier.  And it might be cheaper to used threaded fittings if that was an option.

Re:  the laminations in plate- note that other non-code flange specifications allow flanges and blind flanges to be made from plate.

RE: Pressure Vessel - Flat Plate thickness at Pipe Ends

(OP)
Thanks again for the input, everyone.

moltenmetal, I was not aware of that, thanks for the heads up.  

JStephen, pipe caps were discussed and are definitely the way we will go on furure projects.

Roark arrived in the mail last night, so everything should be squared away fairly soon.

RE: Pressure Vessel - Flat Plate thickness at Pipe Ends

The units the OP is talking about are below the scope of ASME VIII but are definitely *not* non-code.  They need to be designed and fabricated and inspected in accordance with a code- B31.3 perhaps in this case, which allows you to use ASME VIII Appendix 2 to design a flange or other head if need be.

Personally I would allow a slip-on type body flange or a blind to be made from plate any day of the week, but to make any other kind from plate I would want UFD done to ensure that the plate is free from defects before machining.  I just wanted to now if ASME VIII took that position as well.

Yep, for small sizes, pipe caps are the way to go, provided you have a welder properly qualified to do the butt welding and you don't mind the cost of the radiographs.  If not, for the 2" and smaller stuff, you can buy socket welding caps.

RE: Pressure Vessel - Flat Plate thickness at Pipe Ends

For socket-weld caps, specify "SA-105 3000#".  They are cheap, and don't engender any mandatory radiographs, like buttweld caps do.  

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