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Manway size

Manway size

Manway size


I was wondering is there a recommended maximum manway in reference to the diameter of a vessel.  We have a 54" diameter vessel.  The client is proposing a 36" manway.  UG-46(l) indicates the minimum size for a round manway is 16".  The client minimum size is 24".  But they would like a 36" manway.  However they are concerned on a maximum size.  

I know we can reinforce the area, but I just was checking if there is a technical reference or a commmon industry standard on how big a manway can be with reference to the diameter of the vessel?


RE: Manway size

Seems a little silly to have such a large manway for such a small vessel. What's the reason, large removable internals? There is no Code limit in size but generally 24" would be a refinery standard.

RE: Manway size

Thanks for the response.  I do realize 24" is typically a refinery standard, but this pressure vessel is a multi-media filter -- so we were thinking it would be easier to get the media out with a larger manway which is why we were considering a 36" manway.  

Someone had mentioned that there was a generic formula to determine if a manway was to big or if it would need extra reinforcing.  But I cannot seem to find it in the code.

Again thank you for your input.  

RE: Manway size


Money spent on a larger manway is difficult to justify up front by the project folks but will most likely pay large dividends in future operating costs and safety (easier to get people and stuff in/out means less likelyhood of an incident).

You need to read VIII-1 UG-36 and Appendix 1-7. From UG-36:(b) Size of Openings
(1) Properly reinforced openings in cylindrical
shells are not limited as to size except with the following
provisions for design. The rules in UG-36 through UG-43
apply to openings not exceeding the following: for vessels
60 in. (1 500 mm) inside diameter and less, one-half the
vessel diameter, but not to exceed 20 in. (500 mm); for
vessels over 60 in. (1 500 mm) inside diameter, one-third
the vessel diameter, but not to exceed 40 in. (1 000 mm).
For openings exceeding these limits, supplemental rules
of 1-7 shall be satisfied in addition to UG-36 through


RE: Manway size

Thank you so much that was what I was looking for.  And you are right we were having a hard time justifying the cost.  

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