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Painting of shell manhole flange surface

Painting of shell manhole flange surface

Painting of shell manhole flange surface

Dear experts,

Shell manhole flange which is machined from plate will have a serration. In some projects I saw this serrated flange face is painted and we used CNAF gasket without any leaking issue during operation.

In other project we did not painted this serrated surface and we used CNAF gasket as well and no leaking issue.

Another project we did not have serrated surface but we applied something like grease (Molycot)and used CNAF gasket. No leak was found.

Another project we use RFWN flange for manhole flange(expensive manhole). We painted the flange face except the gasket contact surface We used spiral wound gasket. No leak was found.

Is there any standard stating how it should be ?



RE: Painting of shell manhole flange surface

Ring gaskets or full-face gaskets, machined or not machined, also seem to work either way.

RE: Painting of shell manhole flange surface

The best approach would be to have a serrated finish and apply no surface treatment over the majority of the gasket contact face. This is a low pressure application so you can get away with pained surfaces or no serrations in most cases.

The weld neck with spiral wound is overkill but is never going to leak on a tank if assembled correctly.

I would not apply anti-seize or grease to any gasket surface, I think this is bad practice. Lubricating an o-ring or seal ring is a different story but CNAF gaskets should have a clean and degreased surface IMO.

RE: Painting of shell manhole flange surface

API 650 is rather vague and basically says anything that works so long as the purchaser accepts / agrees it.

I wouldn't normally paint gasket sealing surfaces or have non serrated finishes, but within only a few metres head you can probably get away with nearly anything.

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