How to choose a wire gland for instrument installation?
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The diagram mentions the use of dust-proof junction box wiring boxes; what is the difference between these and explosion-proof junction box wiring boxes? The one with a tee isn’t explosion-proof, right? Should I use a 90-degree elbow instead? But a 90-degree angle doesn’t serve the purpose of drainage; how should one choose?
The person who designed the standard diagram must not be functioning properly in his mind; probably he was scared by water getting into the instruments, and that’s why he came up with such a messy design. Remember, the explosion protection isn’t there; it’s in the cable entry device.
The three-way drainage box is used for drainage; water often accumulates inside the conduit, so a drainage three-way fitting should be installed at the lowest point of the conduit. By removing the plug, the water accumulated in the conduit can be drained. There is no need to use tees in areas where water accumulation is unlikely.
It’s a misguided interpretation – what’s the difference between opening the plug to allow drainage and adding an elbow to open the back cover? The design doesn’t include a thread plug.
If that’s what’s said upstairs, then what exactly is the role of those three connectors?
The design is fine. It is correct to install a drainage tee at the lowest point of the conduit (also known as a cable protection tube; it is now called a cable duct). Not only the protection tubes, but cable trays as well should have drainage holes. As for explosion protection, sealing measures must be taken at the entrance of the instrument junction box.
I already said it’s a problem with the standard drawings; if the design is just copied mechanically, what could go wrong? In practice, few companies adopt the three-conduit solution, as wire ducts are not water pipes.
Don’t reject the standards; some of them do have unreasonable aspects. However, the issue of using conduit for drainage is mentioned in multiple specifications, and it hasn’t been removed even after several revisions. Continuing to argue about this doesn’t show how intelligent you are. Moreover, in practical experience, failures caused by water entering the wire conduit are very common. How many companies install three-way connections? Does it really have to be drained after installing the tee to prove that it’s correct? Does a fire hydrant need to be used to extinguish a fire in order to prove that it is necessary to install one?
Instrument: Wiring of the explosion-proof box for solenoid valves
I’ve learned it; I hope there will be more topics like this in the future