Standard Commercial Products for External and Outdoor Lighting System to be chosen as per the design requirement specified in the project documents including recommended and approved list of manufacturers.
Construction of Lighting Column
Columns are to be circular section, tapered, formed sheet steel, powder paint coating finish (color to be approved by the Engineer), electrically welded, and of height specified. Columns up to 12 m height are to be one-piece section. Columns above 12 m and up to 20 m height may be supplied in two-piece sections, of the slip joint type with sufficient overlap to ensure correct vertical alignment of column after assembly. Columns are to have minimum wall thickness of 3 mm at base. Sheet steel is to have minimum rupturing resistance of 37 kg/mm2 and minimum yield strength of 24 kg/mm2.
Top of column is to be designed to receive single or double arm brackets or other arrangement required, supporting number of luminaires shown on the Drawings. Bracket arrangement is to be designed to ensure that failure, due to wind induced oscillations, does not occur and that rotation from desired alignment is not possible.
Lighting Column Design
Column cross-section, thickness of steel, joints, welds, bolts etc. are to be designed to withstand gust wind velocity of 160 km/hr blowing in the most unfavorable direction at a height 10 m above ground level, with column fully equipped. Fatigue of steel is in no case to exceed half elasticity limit, taking into account dynamic stresses due to vibrations. Steel flange plate, of adequate thickness, is to be solidly welded onto lower edge of column as shown on the Drawings, and is to have specified number of holes for holding down bolts together with central cable access hole not less than 150 mm diameter.
Access Door of Lighting Column
Access door of weatherproof construction, with non-degradable heat resistant rubber gasket, is to be positioned at column base and is to be suitably sized to insert and service the supply cable terminations and protective device. Door is to be flush fitting with retaining mechanism and positive locking arrangement with removable hexagonal key. Column is to be reinforced at door opening. Opposite each door, a non-hygroscopic baseboard of suitable size to accept appropriate equipment is to be fixed to inside of column by purpose-made brackets. Steel earthing stud with washers and nuts is to be welded inside the column near the access door.
Finish of Lighting Column
Columns shall have an external powder paint coating (color to be approved by the Engineer). Welds are to be smooth with spatter removed, inside and outside surfaces of column are to be cleaned by pickling or blasting and are to be free of grease. Steel components of columns to be hot-dip galvanized after fabrication. Minimum thickness of zinc coating is to be 500 g/m2 on both inside and outside surfaces of column. Galvanizing is to be to NFT 91 121 (June 1958) or BS EN SO 1461. Any damage to galvanizing is to be rectified during erection by wire brushing affected area and treating with approved rust converter to the satisfaction of the Engineer. Flange plate and inside and outside of column base are to be coated with heavy bitumen paint prior to erection.
Protection and Wiring of Lighting Column
Columns with 1 or 2 luminaires are to be connected over 1 phase and neutral. Columns with 3 or more luminaires are to be connected over 3 phases and neutral, unless otherwise shown on the Drawings.
- IP rated "cut-out" weatherproof enclosure box to be provided at base of pole containing MCB and cable terminations. Fixing/holding screws shall be captive type.
- Bolted terminals and cable lugs are to be provided with 3 phases and neutral terminals, for incoming and outgoing 3 phase 4-wire cable, and of the sizes shown on the Drawings.
- Terminal blocks shall be high temperature, non-inflammable, non-toxic material with high quality fixing screws. Individual terminals for ach termination.
- 1 circuit breaker, single pole 6 A is to be provided for each phase leading to a luminaire.
- Circuit breakers are to be compensated and rated for 50 deg. C (122 deg. F) ambient with interrupting capacity of at least 9 kA.
- Wiring is to be PVC insulated 3 core or 4 core, heat resistant type to 105 deg. C (221 deg. F) conductor temperature.
- Cable is to be at least 4 mm' stranded, tinned, annealed, electrolytic copper conductor.