What is the purpose of the hole in the center of the manhole cover?
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Our facility has some storage tanks whose manhole covers have holes in their center; the depth of these holes is almost equal to the entire thickness of the manhole cover. This is not indicated on the drawings, nor is it mentioned in HG21599. I’m not sure what purpose these holes serve Thank you for your advice! Manhole specifications: RF600-4.0 HG21599-1999.
I asked the same question before, and the person in charge of the equipment said it was the exhaust port during welding (with inner stainless steel material and outer carbon steel material). I’m not sure if it’s right.
The OP’s self-answer is absolutely correct
I have seen it, but I don’t know what use it is.
It’s that the thickness of the exhaust blank doesn’t reach the thickness of the human-shaped blank
I’ve never seen any with a hole in the middle; it seems that the exhaust openings for manholes are all on the sides.
I only know that there are welding vents on the reinforcement ring; I’ve never heard of or seen vents on the manhole that are almost as thick as the manhole itself. I’m not sure – could you send a photo so we can take a look?
It is the hole for exhaust and leak detection.
:L, I think it’s used to fix the manhole cover; there’s a mechanism on the outside that can rotate 90 degrees, and inside there’s a corresponding clip that locks in place after a 90-degree rotation – this is also why the cover is shaped like an ellipse
Today I learned something new again; thanks to the original poster for the question and the answer. :)
It can’t be an exhaust vent, as that would reduce the strength of the manhole cover
I really didn’t pay attention to this detail; I’ll learn from it.
That is a seam welding hole; the manhole cover is composite
It is a process hole used during welding to allow the gases generated during welding to escape
Sampling and analysis port, serving a safety function.
It doesn’t look like an exhaust vent. The vent hole should be on the reinforcement plate.