Discussion on the explosion-proof wiring method for field instruments
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In accordance with Clause 8.1.13 of HG/T20512-2014, for the protection of the cables at the entrances and exits of field instruments, junction boxes, and local instrument panels (cabinets), the following two methods are recommended: 1. Continuous type: The flexible tube of the cable sealing joint is connected to the galvanized welded steel pipe. 2. Discontinuous type: cable sealing joint plus cable tray, or cable sealing joint plus galvanized welded steel pipe. Our company uses cable sealing joints together with galvanized welded steel pipes. From a safety perspective, we would like to know whether this approach is appropriate; please discuss whether it complies with safety standards in light of our company’s actual installation methods or design practices. Our security department requires that the side of the galvanized pipe be sealed with explosion-proof putty, but this putty tends to fall off. How can this be improved?
There should be an explosion-proof gasket at the connection between the cable sealing joint and the junction box. When the sealing joint is tightened, the explosion-proof gasket is compressed and bonded tightly to the cable, thereby providing a sealing effect.
Many factories these days use a discontinuous approach, and this is more common in the southern regions: cable sealing joints are combined with cable trays, or with galvanized welded steel pipes; in such cases, fireproof mortar is generally used for sealing.
Generally, sealing tape is used to seal joints, while for holes and openings, explosion-proof sealing putty is typically used for sealing.
Generally, explosion-proof flexible pipes are connected to steel pipes via threading, and steel pipes are also connected to each other using splices, without welding. Field instruments generally use products with gauges or terminals for wiring; the explosion-proof connectors can be connected directly to the gauges or the outlets on the terminals ； The cables in the junction box are secured and sealed with cable sealing joints, and the holes in the junction box are generally plugged with explosion-proof sealing putty.
Here in Xinjiang, we use explosion-proof sealed joints for sealing
The poster mentioned that the cables coming out of the steel pipe are sealed at the pipe’s opening using mortar, and that these cables are directly connected to the junction box; the junction box is sealed with appropriate connectors. Some of the cables in between are not protected – is that correct?