How to replace one of the electrical cables inside a corrugated conduit

From a building point of view, plastic pipes represent a valid and widely used solution both for the transport of fluids and for accommodating cables of electrical and other systems.

Plastic pipes, and in particular corrugated pipes, are widely used for the passage of cables, power lines, and telephone lines, thanks to their flexibility and the presence of a double perimeter wall. Let’s first see the main characteristics of corrugated pipes to understand then how to proceed with the replacement of an electric cable placed in a corrugated pipe.

 

Corrugated pipes: generalities and characteristics

Let’s start with a general description of corrugated pipes to better understand the area in which we operate. Corrugated pipes are made with plasticized materials of various types that have different operating characteristics.

Polypropylene is one of the materials with which corrugated pipes are manufactured, a material that has considerable success thanks to its structural properties of great resistance to breaking loads and high temperatures. In addition to all this, polypropylene stands out for its ability to counteract chemical corrosion and for the high level of protection against mechanical abrasions to which a pipe could be subjected. Not surprisingly, this type of corrugated pipes are widely used in construction and in the electrical sector, given their ability to withstand particularly high loads and also be of little harm to the environment.

Corrugated pipes are also made of polyethylene, a material that has much lower resistance characteristics than the previous polypropylene. In addition, PVC may have micro-perforations that can invalidate its use as it may allow liquids / humidity to filter with possible damage to the internal cables. Another unpleasant feature of PVC is its environmental toxicity and also for humans in the event of fire as it releases acid gases and intense smoke.

Apart from these different characteristics, the corrugated pipes produced from the two plasticized materials are sized in the same way: they can have diameters ranging from 16 to 110 millimeters, with the pipes of greater width that, logically, they will be able to accommodate at their internal a higher amount of electrical cables.

But what if the electric cables prewired in a corrugated tube need to be serviced? How best to proceed?

The maintenance operation may involve both the resolution of technical problems relating to one or more cables, and the actual replacement of the same. Let’s see …

 

The replacement of the electric cables inside the corrugated pipes

Take as an example the case in which the cables of a wired electrical system start to give problems from the point of view of functionality. This is a rather common phenomenon, deriving from the wear of the cables themselves or from the presence of factory defects. In such cases, it is necessary to extract (literally!) the electric cables from their location, so as to be able to carry out maintenance work or replace them.

In reality, maintenance is considered an intervention that is substantially not recommended because it acts on electrical cables, not so much because it is a dangerous operation, but rather because of its little use in terms of time and labor costs. We are in fact talking about cables with a relatively low cost, therefore it may be more advantageous to proceed with a replacement, which will be followed by the installation of a new cable system, rather than resorting to the maintenance of the damaged cables.

The substitution itself is mainly a mechanical operation, but one that cannot be improvised. The electric cables will be pulled away from their location, taking all the necessary precautions to avoid tearing or breaking them, especially when the cable to be replaced is only one but it is found together with other cables in the same tube, perhaps not quite well laid out. The ideal in all cases would be to have an insertion tool that thanks to its functionality, is able to pull the electric cables from one part of the pipes to the other.

 

The insertion tool is a particular small cable made of plastic material. It is an extremely flexible object, therefore capable of entering inside pipes and junction boxes and taking away the cables to be replaced.

As regards its use, the tool must be inserted with great care into the corrugated tube in which the cables to be replaced are located. The tube can be intercepted starting from any electrical box. Once the conducting cables are reached, the latter will be grouped together, and then be folded backward beyond the eyelet of the tool itself. At this point the user will simply have to pull the tool towards him, acting with the greatest possible caution (the use of another person is recommended to push the cables into the tube, in the direction of the one who pulls). At this point we will proceed with the extraction of the cables until we reach the junction boxes, always trying to act linearly.

The replacement of the cable will always take place using this tool in the opposite direction: the cable to be inserted will be hooked to the eyelet of the tool or in any case to the top of the same and they will be run together from one electrical box to another: once the cable will be completely inserted, it will obviously be detached from the tool. And you can proceed with the connections to the rest of the system.

 

The use of this tool is the quickest and most practical method for these replacements, but also, in this case, an expert hand is needed: the insertion tool is a delicate and foldable instrument up to a certain point therefore delicate, for this reason, it is recommended to leave to a specialized electrician the replacement of the cables.

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