H.4.1.7 manhole cover shall be provided with a suitable vent

joythejob · Feb 25, 2022

Hi, everybody

I have a question about the API 650 H.4.1.7.
If we want to design the metallic pontoon floating roof, annular closed flotation compartment, due to H.4.1.7 the manhole cover shall have suitable vent.
What is suitable vent? is it free vent?

And I still confuse about "closed compartments shall be capable of being reseal in field after inspection(to prevent liquid or vapor entry)",
meanwhile the manhole cover with vent.
so, what is the purpose of the vent on the manhole cover?

stewbaby · Mar 7, 2022

Not a tank designer, just a long time purchaser / project manager of installations. I have to assume their intention is to relieve trapped vapors. They of course want the sealed manway and a higher vent (versus just a cover) so product during an upset or fire fighting liquids can't get into the pontoon.

JStephen · Mar 7, 2022

Little gooseneck vents (free vents) for the first item.
"Reseal in the field" sounds like they just don't want you having to cut holes to access the interior. This may apply to the floats on skin-and-pontoon aluminum roofs more than anything.

joythejob · Mar 29, 2022

Thank for all your replies.

Finally, I read Annex C, EFR and it talks about the vent on pontoon.
I think both are in the similar concern between EFR and IFR. In Annex C, it says "vent" is to protect against internal or external pressure for compartment.
Also, the requirement of manhole neck height is to protect the condition of punctured pontoons and broken center deck so that it causes liquid flows in to compartment.

This is my point of view... share with you

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H.4.1.7 manhole cover shall be provided with a suitable vent

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