Editing signaling and blocking cables
During the installation of cables, the following work is carried out: placing cables in the pit, laying reserves of cables and cutting their ends, installing cable couplings in the ground or on separate bases, attaching couplings and terminations to structures, wiring, jointing and connecting cable cores to contact clamps or panel tabs with leads of cable couplings and signaling equipment, fixing the location, painting and marking of couplings and terminations. The cable is installed by electricians who have a certificate to carry out the work.
Before the installation of floor cables begins, pits are dug for laying their reserves and installing branching, universal and connecting couplings, track transformer boxes and other devices.
The internal and external surfaces of cable couplings and compartments for cable entry into track transformer boxes and cable boxes are thoroughly cleaned of dust and dirt before installing cables. Before cutting floor cables, their ends in the pit are disassembled in direction and cleared of soil. The cable reserve in case of re-cutting is laid in a semi-circle at the point of entry into the relay cabinet, branch coupling and other devices. Before cutting the cable, the insulation resistance of the cores is measured, their integrity and the absence of communication between themselves and the metal sheath, screen or armor are checked. Cable cutting involves the stepwise removal of the outer cover, armored cover, cushion, sheath, screen, belt insulation and core insulation.
Signal interlocking cables with plastic sheaths. The termination of cables with a plastic sheath is performed without end couplings. The ends of the cables are inserted into travel boxes, cabinets, cable racks and other devices directly to the nearest clamps. The end is left such a length that the cores of this cable, after cutting, can be connected directly to the clamps without extension.
When cutting the end of the cable (Fig. 84), the length L of the cable end is determined in each individual case depending on the input device. The first bandage is applied with soldering wire in three to four turns at a distance L + 60 mm from the end of the cable. The cable yarn is unwound from the end of the cable and cut off at the bandage. From the first bandage, at a distance of 30 mm, a second wire bandage is applied to the armor. After this, the armor is unwound to the second bandage.
In cases where it is necessary to secure the armor with flanges, the tape is cut off at a distance of 30-40 mm from the bandage. When securing the end of the cable to the panel in the cabinet, on the cabinet, the armor tapes are cut off directly at the bandage. At a distance of 30 mm from the second bandage, a transverse incision is made on the plastic shell to a depth of no more than 1/2 of the thickness of the shell. The cut sheath is removed from the end of the bundle of cores. The waist insulation tapes are unwound and cut at the edge of the shell. The polyethylene insulation is removed from the cores at a distance of 40 mm if the core is connected under a nut, and at a distance of 10 mm if the core is soldered to the petal. After cutting, the cable cores are passed through the corresponding holes in the panel for connection to the terminals.
The cables are introduced into the relay cabinets through protective pipes. In areas with electrical traction, the armor of cables in relay cabinets is isolated from the protective metal pipe by winding two bands of cable yarn onto the cable.
Signal interlocking cables with sheaths made of polyethylene and polyvinyl chloride are widely used.
In branching and universal couplings, armored signal-blocking cables with plastic sheaths are cut as follows. Protective tube 1 is pushed onto the cable (Fig. 85, a). Then a bandage of three or four turns of adhesive wire is applied. The location of the bandage is determined by the distance from the point of fastening the armor or cable sheaths (between the lower base of the coupling and the flange of the protective pipe) to the clamps, taking into account the length of the laying of the cores and the margin for their re-termination. After this, the protective covering is removed from the end of the cable. At a distance of 30 mm from the first bandage, a second bandage 2 is applied to the cable armor, the armor strips are unwound to this bandage and cut off, leaving 40-60 mm for sealing. The ends of the armor tape 3 are bent at a right angle. Then, at a distance of 30 or 45 mm from the second bandage, the plastic shell 4 and waist insulation tapes are removed. The cable is inserted into coupling 5 and secured in such a way that the bent ends of the armor are clamped between the lower base of the branch coupling 1 and the flange of the protective pipe. Cable cores 2 (Fig. 86) are connected with some reserve directly to the clamps of coupling 1 on the blocks.
The inlet holes of the coupling are sealed with jute, heel or other insulating material. To protect from moisture and dust, the bottom of the coupling is filled with 10-12 mm of cable mass MB-70 or MB-90.
Cutting and installation of cables without armor with plastic sheaths begins by removing the sheath at a distance of 60 mm from the end of the cable and making two longitudinal cuts in a section 60 mm long, one opposite the other.
The notched parts of the sheath are bent at right angles to the cable (Fig. 85.6) and the belt insulation tapes are removed at a distance of 30-45 mm from the bend. Adhesive polyvinyl chloride tape 1 is wound with tension on the remaining part of the waist insulation with a 30% overlap. Winding thickness 2-2.5 mm. The polyvinyl chloride tape should extend 12-15 mm onto the cable sheath.
Inserting the ends of the cable and filling them with cable mass is carried out in the same way as when cutting armored cables, with the only difference being that the ends of the plastic sheath 2 are clamped between the base of the coupling and the flange of the protective pipe.
In universal couplings of types UKM-12 and UPM-24 and in cable racks, the cable is mounted in the same way as in branch couplings (see Fig. 86).
When installing signal-blocking cables in relay cabinets of the ShRSh type, protective pipes are put on the ends of the cables, after which they are inserted into the cabinet and the pipes are attached to its bottom. Cables inserted into a relay cabinet of the ShRU type are secured with plastic clamps and protected from mechanical damage by a common metal casing.
In relay cabinets of the ShRSh type, the cables are placed opposite the panels to which they are connected; The cable cores are embroidered freely, without being tied into bundles. In relay cabinets of the ShRU type, the cable cores are tied into bundles, which are placed vertically along the panels; At the corresponding panel clamp, the cores are branched from the bundle at a right angle.
When installed in traffic light glasses with metal masts, the cables are secured using a conical winding of resin tape applied to the ends of the cables (within 200 mm of the cut of the sheath), of such thickness that the winding fits tightly into the base of the coupling and holds the cable.
Cables with a polyethylene sheath in polyethylene couplings. When connecting cables with polyethylene sheaths from the end of the cable at a distance of 335 mm for cables with a number of cores up to 9, 390 mm for cables with a number of cores from 12 to 19 and 450 mm for cables with a number of cores from 21 to 61 on a jute or plastic protective the cover is applied with a wire bandage of two or three turns of adhesive wire. The outer cover is removed from the end of the cable to the bandage. At a distance of 30 mm from the first bandage, a second bandage is applied to the armor, the armor strips are unwound and cut. The polyethylene cable sheaths are cleaned and wiped with a cloth soaked in gasoline.
The cables to be connected are laid side by side towards each other so that their ends extend beyond the edges of the coupling to be installed by 50-100 mm. In the middle of the coupling, both cables are tied with twine.
Marks are made on the sheaths of the cables being connected at the ends of the coupling, after which the twine is removed. From the marks made, step back towards the ends by 30 mm for cables with a number of cores from 3 to 12, by 40 mm - for cables with a number of cores from 16 to 27 and by 50 mm - for cables with a number of cores from 30 to 61 and a polyethylene sheath deleted. Half-couplings 2 are put on the ends of cables 1 (Fig. 87) and pushed beyond the cutting area. Then the cables are secured in an installation machine or installation gantry so that the ends of the sheaths are at a distance of 30-40 mm from the securing clips. The screen tapes and screen longitudinal wire are wound into rolls and temporarily secured to the sheaths of the cables being installed. Cable cores are divided into bundles or layers.
The connection of cores 3 begins with the central layer, observing the insulation colors without transition of pairs from layer to layer. The connected cores are cut so that their ends overlap each other by 75-100 mm.
At a distance of 50 mm, the insulation is removed from the ends of the cores, and a polyethylene or polyvinyl chloride tube (sleeve) 4 50 mm long is put on one of the two connected cores. The twist length should be 20-25 mm. Each twist is soldered, bent, pressed tightly to the conductor and the sleeve is moved so that the distance from the end of the sleeve to the exposed twist wires is at least 10 mm.
After connecting all the cores, the resulting splices are compacted and wrapped with two layers of polyethylene or polyvinyl chloride tape so that the tape extends 20 mm onto the shells.
The ends of the sub-screen wires are connected by twisting. The screen is restored by winding the splice with cable screen tapes or aluminum foil tapes previously wound into rolls. The ends of the screen tapes are connected to each other into a “lock”.
The coupling halves are moved onto the core splice so that one coupling half fits into the other until it stops.
The surface of the polyethylene cable sheath over a length of 40–45 mm and the ends of the coupling halves over a length of 30–35 mm are thoroughly cleaned with a knife and degreased with gasoline. The joints between the shell and the coupling halves and between the coupling halves are tightly wrapped with polyethylene tape. Three or four layers of glass tape 35 mm wide are wound tightly over the polyethylene tape, with 50% overlap. The glass tape should extend beyond the edge of the winding of polyethylene tape by 20-25 mm. The areas where the coupling halves and cable sheaths meet are uniformly heated with the flame of a gas burner or blowtorch.
The welded joint is cooled to a temperature of 50-60 °C and the glass tape is removed. The welding area should be free of air bubbles, cavities, cracks, folds, delaminations and burns. The polyethylene coupling and adjacent cable sections are wrapped in two layers of resin or rubberized tape with 50% overlap.
Upon completion of installation, the polyethylene coupling is placed in a cast iron coupling, which is filled with MB-70 or MB-90 cable mass.
Cables with homogeneous and dissimilar plastic sheaths are mounted in polyethylene couplings using casting compounds at an air temperature of at least -10 °C. Before connecting, the ends of the cables are separated. Screen tapes and screen wires are rolled into rolls and left at the edge of the armor tape. The two separated ends of the cable are folded together so that the rolls of screen tape do not interfere with the cables' tight fit to each other. The cores are disassembled into layers in bundles of 9-12 cores. The cores of bundles of the same name are connected to each other, observing the colors of the cores.
Cables with a number of cores up to 12 are connected in one level, and cables with a number of cores over 12 are connected in two levels with an equal number of cores at each level. A length of 50 mm of insulation is removed from the ends of the conductors, the conductors are twisted in pairs, the twists are shortened to 25 mm, and soldered by immersion in molten POS-40 solder.
In Fig. 88, a: 1 - cable sheaths; 2 - current-carrying conductors; 3 - twists. Sleeves 4 (Fig. 88, b) 50 mm long, made of polyethylene tubes, are pushed onto the soldered twists of the cores. The sleeves should extend 15-20 mm onto the polyethylene insulation. On top of the sleeve, bundles of cores are tied with adhesive tape 5 or harsh threads boiled in paraffin.
The ends of the wires soldered to the armor tapes are twisted together and cut so that a twisted end 15-20 mm long remains. The screen tapes are shortened to 70 mm, folded together, connected with a roofing seam, and both ends of the cable are wrapped in one turn. Screen wires are wound over screen tapes, twisted and wound onto armor tape, then soldered.
Unarmored cables are installed in the same way as armored ones, with the exception of the connection of armored tapes.
The splice of cable cores (Fig. 88, c) is wrapped with three to four layers of glass tape 6, 20 mm wide and 0.1-0.2 mm thick. To prevent the tape from unwinding, its end is secured with threads 7. A coupling 8 is applied to the prepared cable splice (Fig. 88, d) and the level at which the cable will be immersed in it is determined, so that the ends of the sleeves do not reach the bottom couplings 10-15 mm. Both cables at this level are wrapped with plastic tape 9.
To allow the compound to flow freely between the cables, insert 10 is inserted at a distance of 10–15 cm from the place where the sheaths are cut, providing a gap between the cables of 2–3 mm. The insert is made from the sheath of one of the cables being connected. Then the coupling body is placed vertically in the loose soil of the pit dump and filled with bitumen compound 11 to two-thirds of the height. The temperature of the compound during pouring is 70–95 °C. After filling the coupling and cooling the compound for 3-5 minutes, the cable is inserted into the coupling to the level marked with plastic tape. Without waiting for the filling mass to cool completely, the coupling is installed vertically in a recess in the bottom of the trench so that the coupling rests on the ground. Loose soil is added and compacted into the gap between the cables and the bottom of the pit at the exit from the coupling, then the pit is backfilled.
