How many control wires can be passed through a galvanized pipe?

The number of cables that can fit inside a conduit depends mainly on the diameter of the conduit and the outer diameter of the cables. According to standards, it is generally recommended that the cable filling rate should not exceed 40% to 50% of the inner diameter of the pipe. To avoid cable damage and excessive friction, while also taking into account the convenience of potentially adding more cables or carrying out repairs in the future. For the galvanized pipe you mentioned, with a G3/4 inch diameter (approximately 20 mm inner diameter), we can estimate as follows: the cables to be used are 2 x 1.5 mm² power cables and 4 x 1.5 mm² status feedback cables. The number 1.5 mm here refers to the cross-sectional area of the cable, not its outer diameter. Generally, the outer diameter of a cable is greater than its cross-sectional area, depending on the method of cable manufacturing and the thickness of the insulating material. For example, the outer diameter of a 1.5 mm² single-core cable is likely to be around 5–7 mm, while the outer diameter of a multi-conductor cable is larger. We need to know the actual outer diameter of the 2 * 1.5 and 4 * 1.5 cables you mentioned in order to calculate more accurately. Assume that two relatively common actual outer diameters are 7 mm and 10 mm. So: - The outer diameter of the power cable is 7 mm, and its area is approximately 38.5 mm² (π*(7/2)²). - The outer diameter of the status feedback wire is 10 mm, with an area of approximately 78.5 mm² (π*(10/2)²). The total area of the two cables is 38.5 + 78.5 = 117 mm², while the internal area of the G3/4'' galvanized pipe is approximately π*(20/2)² ≈ 314 mm². If calculated based on a filling rate of 40%-50%, the available area would be 314*40% ≈ 125.6 mm² to 314*50% ≈ 157 mm². Under this estimation, if the actual outer diameter of the cables is similar to the assumed value, these two cables can pass through a G3/4'' galvanized pipe. But note that this is a very rough estimate; in practice, it is necessary to accurately measure the outer diameter of the cable and refer to relevant building and electrical codes. The relevant specifications for the Chinese mainland can be found in the \"Code for Electrical Design of Buildings\" GB 50054-2011 or its updated versions, as well as relevant industry standards and the installation requirements set by equipment manufacturers. The specifications provide clear requirements and guidelines regarding the installation of electrical conduits, the number of wires to be run through them, and the filling rate inside the conduits. In practical work, it is necessary to comply with the requirements of these standards. If you are outside of China, you may need to follow local regulations for design and construction. .

19DX101-1(19) – Common data on building electrical systems; take a look at this post on the forum

Not allowed{:9008:}

For the installation of protective pipes, the filling factor is 0.3 to 0.5, with a value generally not exceeding 0.4. However, cables of different voltage levels are not allowed to be run in the same conduit; in explosion-proof environments, proper sealing becomes a problem, so generally only one cable is placed in each conduit. Refer to the contents related to the installation of protective pipes in SH 3019 and HG 20512.

Thank you for your answer. I checked the installation specifications for instruments issued by the Ministry of Chemical Industry and the petrochemical industry, but they don’t specify any requirements regarding the number of cables

I’ve read both of these specifications. I remember that there seemed to be requirements regarding the quantity – it seems that no more than two tubes are allowed per unit, but I can’t find where that information is stated

Why? Is there standard support?

Are the specifications for building electrical systems also applicable to the installation of chemical process instruments? Are there no regulatory requirements related to instrumentation due to the petrochemical or chemical industry?

Just wear it and don’t ask questions. There are already many unreasonable regulations nowadays. The cable for a control valve can be used; it works even when both intrinsically safe and flameproof signals are present. In practice, haha.