Process Engineering Division – Instrumentation and Automation Section – Daily Question – Question from 2020-11-12
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Process Engineering Division – Instrumentation and Automation Section – Daily Question – Question No. 2020-11-12: Discussion question: 294. Please list the common non-compliant practices in the installation of cable and wire protection conduits
1. The electrical cables and instrument cables were not laid separately, resulting in severe interference to the instruments.
2. When the cable is laid at bends, excessive force is applied, causing damage to the cable’s conductors; there is no protection at those bends, and as a result the cable’s outer sheath gets damaged, allowing the conductors to be exposed.
3. The cables are laid in the cable tray in a disorganized manner, causing them to twist together. This not only looks unsightly but also hinders heat dissipation and takes up extra space. Poor coordination among the people handling the cables results in excessive excess length at the bends, making the setup look bulky; on the other hand, too little excess length causes the cables to be too tight, preventing the cover plates from being closed properly.
4. When intrinsically safe cables and non-intrinsically safe cables are installed in the same tray, they should be separated by partitions to prevent signal interference.
1. Strong-current cables and weak-current cables share the same protective conduit. 2. The cables are severely bent. 3. There are too many connections. 4. The protective conduit is not securely fixed
The electrical cables and instrument cables lack interference protection measures, and the connections of the protective sleeves are not properly sealed
(1) The cable protection pipes are layered on top of each other, so that they rise above the surface of the rebar. (2) Two or more power pipes are placed side by side in close contact. (3) The depth at which the power conduit is buried in the wall is too shallow; it is even buried in the loose layer outside the wall. The pipe shows dead bends, cracks, and dents. (4) The wire conduit enters the distribution box; its end inside the box is not filled properly, resulting in an excessively long exposure ； The pipe openings are uneven and of different lengths ； No protective ring is needed for the pipe outlet ； Not securely fastened. (5) When embedding cable protection tubes, the tube openings are not sealed with plugs, but rather the openings are flattened and bent using pliers.
1) The cable ducts are layered on top of each other, with the pipeline installation positioned above the level of the rebar. 2) Two or more wire ducts are placed side by side in close proximity to each other, with some of them having a larger diameter. 3) The wire ducts are buried too shallowly in the wall, or even in the loose layer outside the wall. The pipe shows dead bends, hard bends, and dents. 4) The wire conduit enters the distribution box; its opening inside the box is not straight and extends too far out ； The pipe openings are uneven and of different lengths ； No protective ring is needed for the pipe outlet ； Not securely fastened.
The bending radius for laying and installation is too small； Not neatly arranged ； The selected model does not match the cables and wires ； Damage or corrosion of the protective tube, etc...