What is the hole in this flange for?
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It’s the hole in this gray-painted flange (I remember someone asking about this question a few days ago, but they didn’t send any pictures; I happened to see it at the office today, so I took a photo and am asking for advice). The second question concerns that long rod bolt on this orange-colored flange (which is an explosion-proof electric heater) – what is its purpose?
Long rod bolts are used as jacks to lift the cover when opening it. The holes in the gray-painted flange are used to check for leaks in the flange gasket. (The flange may be a faced flange)
The screw holes on the gray-painted flange may be vent holes for the welded flange, or inspection holes for pressure testing.