Installation of electrical wiring in pipes. Scheme, description

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Installation of electrical wiring in pipes. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Electric installation work

Wiring in pipes (steel and plastic) are performed only in cases where the use of other laying methods is not recommended. Pipe wiring is used to protect wires from mechanical damage, to protect insulation from adverse environmental conditions. To protect against mechanical damage, the pipeline can be made leaky, and to protect the wires from the external environment, it must be moisture and dust tight.

The tightness of the pipeline is ensured by sealing the joints between pipes, their connection to junction boxes and various electrical appliances.

To avoid overheating of steel and plastic pipelines, they should be laid below the pipes of the heating system. When crossing with them, the distance to the electrical wiring pipes must be at least 50 mm, and with parallel laying - 100 mm.

Steel pipes are laid so that moisture cannot accumulate in them. To drain moisture that can condense in pipes, they are laid on horizontal sections of the route with a slight slope towards the box.

Unprotected insulated wires of the APRTO, PRTO, APV, PV, etc. brands can be placed in steel and plastic pipes.

Installation in pipes should be carried out in such a way that, if necessary, the wires can be removed and replaced by others. Therefore, if there are 2 bending angles on the pipeline route, then the distance between the boxes should not exceed 5 m, and on straight sections - 10 m.

Connections or branches of wires in pipes are prohibited, they are made only in boxes.

Installation of electrical wiring in steel pipes can be carried out with open, hidden and external laying. Steel pipes are used when laying wires without pipes is not allowed and non-metallic pipes cannot be used.

Pipes must be free of rust, dirt and burrs before installation. To protect the shell of wires and cables from corrosion, pipes laid openly are painted on the outside (preferably also inside) or galvanized pipes are used. When laying in concrete (concealed laying), the pipes are not painted on the outside for better adhesion of their surface to the mortar.

Crushing (corrugation) of pipes when bending at corners is not allowed.

It is not recommended to bend the pipe at an angle of less than 90 °, since it will be difficult to drag the wiring through with a complex configuration of the pipeline and its long length. For this reason, pipe bending radii are limited: when laying pipes hidden, the bending radius must be at least 6 outer diameters; with one bend or open laying - at least 4 outer diameters; when laying a pipe in concrete - at least 10 outer diameters.

With open laying, the distance between the fixing points of steel pipes in horizontal and vertical sections depends on the diameter of the pipes being laid. Pipes with a diameter of 15-32 mm are fixed after 2,5-3,0 m, at bends - at a distance of 150-200 mm from the angle of rotation.

With open laying, the pipes are attached to the supporting structures with brackets, overlays and clamps made of strip steel.

When installing wiring, the ends of the pipes after trimming are cleaned of burrs, countersunk and terminated with metal or insulating bushings that protect the wire insulation from damage at the point of entry and exit from the pipe.

In damp, especially damp, fire hazardous rooms, outdoor installations and in attics with open and hidden laying, steel pipe joints must be sealed. The sealing of the connection points and the points of entry into the boxes must be carried out with standard threaded couplings with a seal with tape or hemp on drying oil, minium.

When laying steel pipes hidden in dry and damp rooms, in walls, ceilings and floors, it is also necessary to seal the joints and the places where the pipes enter the boxes.

When laying openly in dry, dust-free rooms, the pipes themselves are connected, as well as their connection with boxes, without seals: sockets, cuffs on screws and bolts, sleeves from pipe segments or rolled from sheet steel, welded to the pipe at several points.

Plastic pipes have sufficient mechanical strength, smooth surface. When using them, the probability of shorting the wires to the ground decreases, labor costs during installation are reduced (operations such as threading, painting, etc. are excluded)

Plastic pipes laid openly are fastened with brackets that allow free movement of pipes with a temperature change in length. The distance between the brackets is taken as follows (see table):

Table

Installation of electrical wiring in pipes

The distance between pipes laid in parallel must be at least 65 mm with a diameter of up to 25 mm.

Staples are fixed with screws or using nylon dowels.

Author: Bannikov E.A.

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