Circle and square of manhole
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When should manholes be round? ? When to use square? ?
I have only seen round and elliptical ones, but never square ones. Generally, the kettle is oval, and the homemade pots are round, which is easy to make.
Round or oval manholes and hand holes are common, while square ones are rare. Round ones have good bearing effect, while square ones do not bear pressure. It can also be said that containers with normal pressure equipment and the internal medium is not flammable, explosive, toxic or other dangerous media can be made into square manholes and hand holes.
According to the provisions of GB150 opening reinforcement, the opening should be circular or oblong (the ratio of the major axis to the minor axis should be less than or equal to 2). This is mainly considered from the perspective of stress. The stress concentration coefficient of this structure is small. If the opening is rectangular and is used on a pressure vessel, finite element analysis and calculation should be performed. Therefore, pressure-bearing equipment should use circular manholes as much as possible, and atmospheric pressure equipment can use rectangular or square manholes according to their structure and usage.
I personally understand that there are three reasons: 1. The human body is round in shape. 2. The round one has a larger area. 3. The round one brings less stress to the tank than the square one.
There are also square ones, and there are some on square grooves. The standard stipulates round ones, and there are a few size plans.