Manway size selection 1

[vinothsvk]

Dear all,
I am vinoth. I am working in oil and gas field (especially pressure vessel design) and I am new in engg-tips. I have doubt in selection of manway size. For example,the vessel ID 1400 mm.shall I go to select the manway size 24inch or 20 inch. Basically which basis are followed to select the manway size. In ASME Sec VIII Div-I describes any procedure about manway size selection?.

Thanks.

 

[SnTMan]

vinothsvk, welcome to Eng-Tips. There is no guidance in Sec VIII, Div 1 for sizing a manway. But, ask yourself "Would I rather go in thru a 20" or 24" manway? Which size would the physically large maintenance individual I'll never meet prefer?"

I personally would not make it smaller than 24".

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[marty007]

The only guidance that ASME provides (UG-46(g)(1)) is that an elliptical or obround manhole shall not be less than 12"x16", or a circular manhole shall not be less than 16". I've always shuddered at thinking of crawling into a 12"x16"...

That aside, I agree with SnTMan. These days, I don't see any customers asking for 20" manways anymore unless there are special circumstances.

 

[SnTMan]

marty007, correct, I had forgotten. Open book before opening mouth

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[r6155]

See

http://www.eng-tips.com/viewthread.cfm?qid=173241

Regards
r6155

 

[SNORGY]

Most companies I work with appear to be defaulting to minimum 24" D (or 20" minimum I.D.), I believe, in order to accommodate a man of average size to comfortably gain access into and egress from the vessel with a full SCBA for Confined Space Entry.

 

[Mech2325]

Yes, read UG 46

 

[vinothsvk]

Thank you snTMan & marty007

 

[MJCronin]

Although there seems to be no limit in the ASME code, it is strongly suggested in the EN (and other) vessel codes that the manway size not exceed on-half of the vessel diameter. This is a reasonable structural limitation and particularly important for the design of small diameter tall columns.

With your vessel diameter of 1400 mm, you are getting close to half of the diameter with a 24 inch manway.... my vote would be for you to use a 20 inch.

Remember, the primary reason for a pressure vessel manway is to enable access for internal visual inspection....

Inspection can be possible through multiple small inspection "hatches"... judiciously placed.

Another rarely used alternative (although very expensive) can be complete body flanges...

http://www.eng-tips.com/viewthread.cfm?qid=306431

http://www.eng-tips.com/viewthread.cfm?qid=173241

MJCronin
Sr. Process Engineer

 

[r6155]

I prefer the term ACCESS OPENING instead of INSPECTION OPENING.
Access opening is required for inspections / examinations (visual, radiographic, ultrasonic, particle magnetic, liquid penetrant, ..etc), internals replacement, weld repairs, cleaning. All above mentioned during fabrication and in-service inspections.

Regards
r6155

 

[r6155]

The most important is to guarantee safe access / egress and good ventilation.

Regards
r6155

 

[KevinNZ]

One of my clients uses DN750 manways, Inspectors are getting bigger!