What type of manhole should be chosen for storage tanks of concentrated sulfuric acid at atmospheric pressure?
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There is currently a vertical storage tank for concentrated sulfuric acid at atmospheric pressure, containing 98% concentrated sulfuric acid; according to HG 20660-2000, it is classified as having moderate hazard. I would like to ask whether a manhole at the top should be of normal-pressure type, or whether, in accordance with the provisions regarding pipe flanges in the appendix of HG/T 20583-2020, a butt-welded flange manhole should be used. When the manhole is located on the lower side of the cylinder and in contact with the medium, what type of manhole can be used in this case?
Is a butt-welded flange manhole also used when the manhole is located at the top?
Choose a PN10 flat welding flange.
Excuse me, is there any specific evidence? Then can we choose PN6?
The pipeline pressure in typical chemical plants is basically 0.6 MPa; therefore, the system pressure is also 0.6 MPa, so a value of 1.6 MPa is sufficient. Choose according to the system pressure.
According to HG/T20660-2017, sulfuric acid is classified as having an extremely high level of toxicity; it is recommended to use manholes with necked butt-welded flanges of PN16.
I don’t know if it’s inconvenient to perform welding work around your sulfuric acid tanks? If it is convenient to perform welding work in the surrounding area, it is recommended not to install manholes on the concentrated sulfuric acid tank; holes can be created temporarily when cleaning the tank. Storage tanks are generally cleaned every few years.
This approach isn’t very feasible; after all, it’s not possible to weld every time it’s cleaned. ;P
In a regular organization, such a practice is impossible. . . Whether welding is possible or not, an access hatch is required.