Cable Tray and Supports

Outline Construction Specifications E&M Works Station Utilities

Chennai Metro Rail Project Phase -1 Contract No- UAA01

damage the conduits, shall be permitted to be used for conduit of 1 inch and smaller. (6) The conduits shall be defined in SI units as on the drawings. The table below show the comparison of diameters of conduit in inches and in mm. Conduit Diameter in Inches

½

¾

1

1¼ 1½

2

2½

3

3½

Conduit Diameter in mm

15

20

25

32

50

65

80

90

40

100

4.4.8.4.2 Cable Tray (1) Cable trays used indoors shall be made of hot-dip galvanized after fabrication to afford good corrosion resistance during storage, installation and service life. The ventilated type cable tray, punching, with cover shall be provided with the dimensions as indicated on the drawings. The fabricated shall be made of a minimum 2.0 mm thickness steel sheet and shall be capable of being subject to temperatures up to 500oC for 1 hour and shall not support combustion under the same temperature. (2) The supports for horizontally run-cable tray shall be provided such that they shall be capable to adjust vertically. Where tray and ladder systems are supported by drop rods additional restraints shall be included to provide adequate lateral support. Restraints shall be installed at all bends and intersections and at intervals not exceeding 15 metres on straight runs. Support rods shall be at least 6mm diameter. Trapeze or other hangers shall be clamped on the drop rods between two nuts. (3) Support brackets shall be of the same type. (4) Site cuts or bends to hot dipped galvanized components shall be properly repaired in the field using cold galvanizer. (5) Cable drops to equipment shall be rigidly supported using cable tray. Structural steel members, plant pipe work support steelwork or walls may be used for cable drops. (6) Each section of the cable tray shall be electrically bonded, with a minimum 6 mm2 cross section area earth-bonding strap or wire, to the next section to form an electrically continuous system and bonded to the main grounding system with green/yellow low smoke zero halogen material, sheathed, single core cable. All edges, fittings, or any parts of the cable trays shall be finished free from bar, sharp edges, or projections damaging to the insulation or jacket of the cables. (7) The number of cables installed on the cable tray shall be provided in compliance with the requirements of the Indian Standards Specifications, Indian Electricity Rules and IE wiring regulation. And 40% spare space capacity shall be provided for cable laying inside the cable tray. (8) Cable tray or ladder shall not be installed across building or structural expansion joints. On horizontal runs the tray or ladder shall be installed with a 20 mm gap at the expansion joint. Supports shall be installed within 150 mm on either side of the joint. 4.4.8.4.3 Wire way (if applicable) (1) Wire way shall be made of hot-dip galvanized after fabrication to afford good corrosion resistance during storage, installation and service life and shall be provided to form the continuous steel sheet troughs with removable covers attached to the wire way by screws for housing the cables. The minimum thickness required for wire ways shall be as per the following table (in millimetre unit):

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Chennai Metro Rail Project Phase -1 Contract No- UAA01

Outline Construction Specifications E&M Works Station Utilities

Size of wireways (width x height)

Thickness

50 x 50 up to 100 x 50 100 x 100 up to 150 x 100 200 x 100 up to 300 x 100 150 x 150 up to 300 x 150 Larger than above

1.6 1.6 1.6 1.6 2.0

(2) Wire ways shall be installed so that all Signalling cables wireways are separate from power cables wireway. (3) Separated wireway for normal and emergency circuits shall be provided as indicated on the drawings. (4) The full length of the wireways shall be supported by the metal hangers at every intervals of not more than 1.50 m for horizontal and vertical installation. The supports for horizontal run shall be provided such that it shall be able to adjust vertically. (5) Each section of the wireways shall be electrically bonded, with a minimum 6 mm2 cross section area earth-bonding strap or wire, to the next section to form an electrically continuous system and bonding to the main grounding system shall be copper with green/yellow, low smoke zero halogen material, sheathed, single core cable. All edges, fittings, or any parts of the wireways shall be finished free from bar, sharp edges, or projections damaging to the insulation or jacket of the cables. (6) The number of cables installed in the wireways shall be provided in compliance with the requirements of the Indian Standards Specifications, Indian Electricity Rules and IE wiring regulation. 40% spare space capacity shall be provided for cable laying inside the wireways. 4.4.8.4.4 Boxes and Accessories (1) Boxes shall be provided in the conduit work for cable connections, cable pulling, installations of switches, and installation of outlets. (2) All boxes provided in the conduit work shall be made of metal. A box provided for cable connections and concealed in or exposed on ceiling shall be a standard galvanized steel square or circular box or a metal box, made of steel sheet with not less than 1.6 mm thickness, with one primer anti-rust coated and two coating finishes. (3) All wall boxes on exposed work shall be of die cast aluminium or cadmium-plated cast-iron. (4) All boxes and conduit accessories shall be fully weather-proof when used in outdoor locations and other locations as agreed during construction. (5) Conduit outlet boxes, for socket outlets, lighting switches, etc., shall be of hot-dip galvanized steel complete with adjustable lug, ample knockouts, and brass earth terminals fitted in the base. (6) Each box shall be covered with a cover plate matching with the box construction and suitable for application condition. 4.4.8.5

Installation System The whole conduit system shall be installed to comply fully with the relevant provision in Indian Standard Specifications, Indian Electricity Rules and IE wiring regulations. Conduits shall be laid either recessed in walls and ceilings or on surface on walls and

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