How many manways per vessel? 5

[nur12]

Hi,

I can't find any info in the Code regarding correlation between vessel length and quantity of the manways required.

Is there anything (except common sense) to justify how many manways shall be on the long vessel (9 m and up)?

Thank you.

 

[jte]

InnSk-

No Section VIII guidance on this one. Typically the owner/operator will have standards such as one manway at every x trays or at every drawoff or every reactor bed etc. Don't forget to include some nozzles to provide ventilation during a turnaround also. These can be process nozzles with flanged piping spool pieces which can be easily removed.

jt

 

[unclesyd]

The NBIC requires at least one as a means to inspect the vessel. A good designer will minimize the numbers of nozzles, thus eliminating potential leaks. As jte states put in what you need and no more.

Here are a few concerns with designing manways:

Make sure it's big enough to pass your internal components.
Keep your internals as large as possible to minimize work in vessel.

The smallest dia. should 20".

Keep the nozzel neck as short as practical and still nave the backside accessable.

Use studs instead of bolts they are cheaper.

If the service is corrosive make the flange thicker to allow machining.

Put the manway in an accessable area, dont make a person stand on a railing to get in the vessel.

I could go on, but this should get you thinking.

 

[bmoorthy]

Good tips indeed.

You may also consider, one manway per partition. That is, if you have baffle inside the vessel and you want to maintain both the sides, either you provide Manway on either side of baffle or you provide one man hole nozzle in the vessel and give a Man way in the baffle.

For tall columns (Process) with Beds/Limiters, then one man hole nozzle per Bed.

For tall towers/Columns with trays, consider giving man hole every 10m or near every process nozzle (Such as Reflux). You need a Platform near a Manhole and a ladder to reach the Platform (Man hole).

Also consider providing hand Grips inside the Vessel/Columns. This will help the personnel to come out easily and qickly.

If your operators are a bit oversize, consider 24". Most of the German design provides 24". 20" is ok for agile, young and energitic operator. If you are designing a vessel for 20 to 25 Years or you if you require future modifications etc in the vessel, then consider 24" manhole.

Good Luck
B.Moorthy
moorthykar@yahoo.com

 

[unclesyd]

bmoorthy,
I neglected to suggest the hand grip or foot grip by manways. This feature alone will get you several cups of coffee and a lot of attaboys. This was my main contribution to most designs as I carried a red pencil just for this purpose.

Anecdotal:
Myself and a mechanic were in a 42" vapor drum on a heating oil vaporizer when the AI decided to come and look for himself.
Being a little portly and as he entered the manway he completely blocked the nozzle, no light, at that time the 12 volt light decide to burn out. I don't know whether the mechanic was scared of the dark, claustrophobic, or lost his horizon, but he panicked. Damn near killed me going in the wrong direction and got me again going toward the manway. He hit the AI and scared him to the point he couldn't move as we about 5 minutes getting him unstuck. The vessel entry standby watch, listening on the radio, was laughing so hard he couldn't help and the mechanic was beating me to pulp. Every time I would get close to manway to help the AI the mechanic would run over me again and hit the AI in an attempt to dislodge him. It ended inside when I found my flashlight and gave it to the mechanic. He wouldn't give the ligh back and until this day I think he thinks it saved his life.

This makes your last statement a case in point.

 

[deanc]

See ASME SecVII Div 1 UG-46. Some help:ASME SecI PWT-14,15 and PFT-42,43.

Think it out,as if you were the one doing repairs.

I agree with unclesyd-I was once stuck inside an EXTREMELY small mud drum with someone wedged in the manway.

 

[nur12]

Thank you, it helps a lot. Unclesyd, that's funny.