Inpection Openings UG-46

[LuisLopezgil]

Hello:

I am working for a Mexican Company that is a new U code stamp holder.
One of our clients - from Belgium - Ordered us a U stamped 48" O.D. Pressure Vessel ( 40 psig and full vacuum) for corrosive service (1/16" C.A.) for a vegetable oil process plant.
Their drawings do not indicate any manhole, only two 6" flanged inspection nozzles (there is no space problems for the installation of a manhole). I advised to our client that is necessary to install a manhole according to UG-46 but they refuse to accept it, they say that in the recent past they ordered to other company an identical vessel and they had no problems to obtain it U stamped.

Before to ask to our Inspector, I would like to know your kindly opinion about if could be substituted a manhole for two small inspection openings without a shape reason and as it looks without a process use reason too.

Thanks a million.

 

[gr2vessels]

Luis,
The code allows the Client to opt for a manway opening OR two handholes for a 48" vessel, if operating conditions would preclude in someway the use of a manway. Obviously, an assessment from the Client or an independent body may be required by the AI, in order to prove that the two handholes would provide sufficient area of access for internal inspection in lieu of a manway (refer to UG-46(f)(3)..."except that those whose shape or use makes one impracticable shall have at least two handholes 4 in. × 6 in. (102 mm × 152 mm) or two equal openings of equivalent area").
Cheers,
gr2vessels

 

[moltenmetal]

I wouldn't put a manway on a 48" shell unless it was needed to install internals.

I also wouldn't enter a 48" shell unless there were very good reasons to do so.

It's the owners' call, not the fabricator's.

 

[unclesyd]

moltenmetal,
We've got 8 48" SS columns with two 24" manways each that we can't get rid of because of insurance requirements. They were in the original design and are of absolutely no use except to open and repair the gasket surface. The columns are being replaced with Ti still with one 20" manway per column, a slight concession. A Titanium column and internals will last at least 50 years, probably more, and we still have to have a manway for inspection. During my tenure this situation nearly got me run off several times.

If you want to crawl through some small openings come by sometime as we have about 20 steam, flash, ans vapor drums with 11x15 elliptical manways. I have made all of them more times than I like to remember.

Anecdotal:
I had just egressed a steam drum when somehow steam was introduced into the mud drum. All of a sudden a little steam showed up in steam drum with my cohort and a mechanic inside. I think both of them came through the manway at the same time as I reached to help them out and both were standing there beside the manway cussing. Never did find out where the steam came from. Before reentering the drum my cohort cut the line from the blowdown manifold to the blowdown header.