Storage tank square manhole calculation method
Storage tank square manhole calculation method
(OP)
Dear all,
a client came to me with a question regarding a storage tank which he wants to equipe with a square (1100x1100 mm) manhole in the shell for which he needs a calculation.
I have checked different codes (API650, EN 14015, EN 13445 etc) but couldn't find a calculation method for a square manhole.
Is there a standard calculation method available according to European or American codes?
I can always do a FEA but I think that's too exhaustive for this question.
Thanks in advance for your replies.
With regards,
Corné
a client came to me with a question regarding a storage tank which he wants to equipe with a square (1100x1100 mm) manhole in the shell for which he needs a calculation.
I have checked different codes (API650, EN 14015, EN 13445 etc) but couldn't find a calculation method for a square manhole.
Is there a standard calculation method available according to European or American codes?
I can always do a FEA but I think that's too exhaustive for this question.
Thanks in advance for your replies.
With regards,
Corné
RE: Storage tank square manhole calculation method
RE: Storage tank square manhole calculation method
I assume the local stresses around a square cut-out are different from those on a round cut-out. That's why I'm looking for some code-formula's to check the reinforcement needed for a square manhole (or cut-out in general).
RE: Storage tank square manhole calculation method
The stresses around rectangular manways can be large due to the discontinuity at the corners. I have seen many oval manways used to reduce these stresses.
RE: Storage tank square manhole calculation method
I have seen rectangular manholes in roofs, but not in shells indeed, I think for the reason you mention (high stresses at the corners).
If an oval manhole is used can I then use the area replacement methods used in the different codes, using the small diameter for reinforcement in one direction and the large for the other direction?
Maybe another option is a rectangular manhole with rounded (half cirle) ends. I assume I can use the same area replacement formula using the diameter (which is equal to the cross section of the cut) and add a reinforcement around the manhole?
Is there any code adressing one of these options?
Thanks in advance for your reply.
RE: Storage tank square manhole calculation method
Using a square manway, you have stress concentrations you don't have with a round manway, and the potential for cracking in or at the corners. You also don't have the past experience that you do with conventional nozzles or manways, so you're on your own. If the manway is square, it would still be preferred to round the corners, or make it an obround manway or something.
RE: Storage tank square manhole calculation method
I was already afraid I am on my own in this issue.
If the client really wants a square manhole and the normal shell stresses are high I think a FEA will be the only option then.
If normal shell stresses are low I'm not really afraid about the stress concentrations.
RE: Storage tank square manhole calculation method
RE: Storage tank square manhole calculation method
RE: Storage tank square manhole calculation method
Normally, there wouldn't be any check in the vertical direction.
RE: Storage tank square manhole calculation method
Aside from preference, why must the manway be square ?
Manways are used to move "things" in and out of the tank.
What reason does your client give when you ask why must it be rectangular ?
RE: Storage tank square manhole calculation method
Eventually the problem is solved much easier than I could expect.
After some questioning the client told me he has already a couple of the same tanks with the same manhole in use for many years. So instead of making a calculation we have now decided to use the "copy from the past" method. It's in use for years and no issues have been found. Both internal and external inspection bodies agreed.
Thanks all for your replies on this matter.
RE: Storage tank square manhole calculation method
In all fairness the respective formula should be applicable in your case most presumably indeed!
Best Regards
Qalander(Chem)