Selection of the diameter of the protective tube when passing cables through it
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Dear sea friends, the outer diameter of a cable is 28.4±3 mm. Will a 2” protective tube be large enough to accommodate such a cable? Is there a formula for this?
There should be no problem with this. If it is a GB hot-dip galvanized steel pipe, the outer diameter is 60.3, the wall thickness is 3.8, so the inner diameter is 52.7.
Standard SH/T3019-2016 7.3.4: When a single cable is passed through a conduit, the inner diameter of the protective conduit shall not be less than 1.5 times the outer diameter of the cable.
GB 50217 5.4.4 The selection of the diameter of the protective tube and the number of cables that can pass through it shall comply with the following provisions: 1 Only one cable should be placed in each tube. Except for important locations such as power plants and substation stations, no more than 3 power cables or multiple control cables may be run in each conduit for all the circuits of a single motor, or for all the circuits of low-voltage motors in the same equipment. The inner diameter of the tube should not be less than 1.5 times the outer diameter of the cable or the outer diameter of the envelope surrounding multiple cables. The inner diameter of the pipe holes in the exhaust pipe should not be less than 75 mm.
This post was last edited by Sea Blue Homeland on 2018-3-30 at 17:27, by the same person as above
The inner diameter of the hot-dip galvanized steel pipe is 52.7. The cable is 28.4±3 mm, which is 1.5 times the required size – perfectly suitable.
The standard is that for a single cable, the inner diameter of the protective tube should be no less than 1.5 times the outer diameter of the cable; in fact, the choice is made with the principles of facilitating construction and keeping costs reasonable in mind.
It is not recommended to follow the standard procedures when passing cables through protective tubes, especially for thicker multi-core cables. It’s not that the protective tubes are too narrow to accommodate the cables; in practice, it has been found that at corners, it’s impossible to bend the cables enough to fit through the explosion-proof cable glands.