Why are these instrument junction boxes placed up there?
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As shown in the figure, there are many such instrument junction boxes above the device tube bank. What are these boxes used for? If anyone knows, please let me know. Thank you
The instrument junction box is used to house and protect the electrical connections of sensors or instruments. It is placed there mainly to prevent moisture and dust from entering, while also facilitating inspection and maintenance. .
This is the intermediate junction box, where signals from the on-site monitoring instruments, valve open/close commands and feedback, valve position control signals and position feedback, etc., are gathered in this box. From there, they are transmitted via main cables to the DCS or PLC cabinet
It looks like a central junction box, but there are so many of them... I’m not sure anymore :o
It depends on the device you are connecting to. From the picture, it seems that the box is explosion-proof; it’s possible that many wires at the site are connected to this box to form a multi-core cable or to transmit signals to the control room, or it might simply serve as an intermediate connection point.
It looks like a central junction box, but there are so many of them... I’m not sure anymore
The intermediate junction box is designed to be installed near the cable tray, which facilitates inspection and maintenance.
As can be seen from the picture, it is an instrument wiring box. To reduce the costs associated with project construction, main cables are usually pulled from the instrument cabinets to this intermediate wiring box using multi-core cables of types such as 12*2*1.0, 6*2*1.0, or 8*2*1.0; after reaching the wiring box, branch cables of types 1*2*1.5 or 1*3*1.5 are used to connect to the instruments, thereby saving on cable costs. The main cable inlet is not visible in the image; generally, we install cables with entry and exit at the bottom, and here only thin cables can be seen, which appear to be branch cables. Secondly, the EX marking on the box indicates that it is likely an explosion-proof wiring box. However, there are several issues: the branch cables do not appear to be armored, the incoming cables lack flexible tubes, and the cables have no mechanical protection. For the second box, where flame-proof cables are fed in bare, a flexible tube combined with a flame-proof cable sealing joint, or an armored cable combined with an armored cable gland, is required to achieve flame-proof sealing. You don’t have this here. The installation specifications for instruments require that the instrument cables pass through openings in the tray sides using plate connectors, and galvanized pipes or branch trays should be used; you don’t have a direct connection from the tray to the box here, and the main tray cover is also missing.
Also, regarding your junction box, it’s obvious that the explosion-proof claim is false