Selecting vessel head for design pressure > 90 barg 1

[mthausif123]

Hi. I am designing a pressure vessel whose design pressure is >90 barg. There are some internals inside the vessels hence inspection is required. I cannot install a manhole because the shell ID < 1000 mm. Can I provide flanged head? And what type of head? Ellipsoidal or spherical?

 

[jt1234]

Whatever you like, less weight may cost less.

 

[LittleInch]

I know I'll get shouted at here, but why not just buy a cap to ASME B 16.9?

And a B16.5 class 600 or 900 flange. Design it to PV codes to get the thickness, but these are off the shelf items.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[GD2]

OP,
By UG-36 (b)(1), you are allowed to go up to opening of half the size of the vessel limited to 20in for a vessel size of 60 in or less. You have a 40 in vessel. By rule of UG-46 (g)(1), you can either provide an elliptical manhole of 12 in x 16 in or a circular manhole not lesser than 16 in. The 16 in manhole will be less than half the vessel diameter. You can even opt for 18 in.

Alternately, you can use a bolted dished cover per Appendix 1-6 if you want to follow that route.

GDD
Canada

 

[jt1234]

GD2, you are mis-interpreting the code. There is no limit on the size of opening. It is just how you will reinforcement the opening. There are so call large opening reinforcement in the Appendix, or small size opening per UG-36 to UG-43, that is what code says. You can even use FEA to design. There are plenty large TEE in any plant. The size can be so large beyond your imagination.
The use of body flange for diameter under 1000 mm is not uncommon. We have numerous vessels with that in order to easily install internals and dump catalyst or molecular sieves.
Just pick a standard flange, B16.47 series A or B, or B16.5. Watch out the shell OD shall match the standard flange small end OD (Shell ID will be reduced such that ask Process engineer if that is acceptable. If not, you need to increase one piping size). And pick hemi head, elliptical head or cap as Little Inch says, and be done with it. Very simple.

 

[r6155]

1) obviously GD2 is wrong.
2) (OP) More info: Is this a tower, material, corrosion,?... etc. etc.

Regards

 

[GD2]

Jt1234 and r6155,
I agree properly reinforced openings in cylindrical and spherical shells are not limited to any size.
My response was focussed on a simple solution to the specific issue raised by OP without having to venture all rules and available options like Mandatory Appendix 1-7 and FEA.



GDD
Canada

 

[Christine74]

For the unanswered question about what type of head to use, unless this is some exotic alloy I usually see 2:1 ellipsoidal heads used for this pressure and diameter. However I would recommend against specifying the head type, instead let the vendor select whichever type is most economical for your application.


-Christine

 

[mthausif123]

Thank you all for your responses. My senior has asked me to explore the possibility of using a full flange flat head instead of an ellipsoidal or hemispherical head. The reason given is that there is just one nozzle on the head, and its size is less than half the size of the vessel. Given this information, a full flange flat head might be acceptable. I would appreciate your opinions on this matter. Thank you!

 

[iangineer]

If you need room, then a flat head may work, but it will be pretty thick compared to an ellipsoidal head. You can probably build a simple setup in Compress or PV Elite to determine which one you like better without having to do a full detailed model.

 

[jt1234]

Standard blind flange per B16.47 or B16.5 if 24" and less will save you a lot of headache. We have done this "a lot". Depending on the nozzle size on the blind, you can exempt from reinforcement calculation, or use a reducer, or weldolet. There are many discussions regarding how to reinforce nozzle on a blind.

 

[r6155]

You need to consider how the studs are installed and tensioned, there is a big difference between a 40" flange and a 20" flange. What tensioning system do you plan to use?

Regards