The sequence of opening the manholes on tower equipment
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The question regarding the sequence in which the manholes of tower equipment are opened is: from top to bottom or from bottom to top? Why is such a requirement?
Before opening the tower manhole, the shutdown procedures must be completed; at that time, there may still be some process fluids remaining inside the tower, which can release toxic and harmful gases. According to the \"chimney effect\" principle, the manhole at the top should be opened first, followed by the manholes further down one by one. The volatile gases inside the tower rise and are discharged through the upper manhole to prevent injury.
The main consideration is ventilation; it was sealed before opening. If one opens it from bottom to top, it’s difficult to access the topmost manhole due to the high concentration of toxic and harmful gases inside. By opening it from the top first, there is no convection inside, so the toxic gases don’t spread easily, which makes it easier to open the manhole. The same principle applies when sealing it.
They all open from top to bottom. Prevent personal injury
From top to bottom, it prevents a lack of oxygen in the lower part, as well as the accumulation of other substances that could cause suffocation
Chimney effect, safety, operating procedures and regulations
Open it at the top first; there is much less thermal convection there. Conversely, it’s difficult to open it at the top.
Top-down, first is convenience, second is safety, and ventilation
From top to bottom, for safety reasons; if the lower parts are opened first, the toxic and harmful gases inside can easily cause poisoning or suffocation. There have been many such accident cases