COLUMNS AND BRACKETS

7.5.1 General

All columns and brackets shall be of tapered, octagonal, hot-dip

galvanised interchangeable sections complying in all respects with the Drawings. They shall be

manufactured to comply with B.S.

1840 and B.S. 5649 with Grade 43C or 50C steel conforming to B.S.

4360. The base-plates and bracket arms shall be manufactured as seperate units suitable for mounting or fixing on to the columns.

7.5.2 Design Loading

The columns shall be designed to withstand loadings comprising :-i) loads due to wind speeds of up to

27 m/sec.;

ii) loads due to the weight of the columns, lighting luminaires and bracket arms;

iii) other applied loads if applicable.

7.5.3 Fabrication of Column Sections Each column section shall be mechanically formed and longitudinally welded by the continuous automatic gas shielded electric arc process (M.I.G. process) to B.S. 5135. The sections shall be constructed so as to overlap each other by a minimum of 1.5 times the diameter of the immediate lower section (external across-faced dimension) and to be easily assembled on site by using simple tools without employing welding techniques. The manufacturer shall

minimum overlapping position of 1.5 times the external across-faced dimension.

7.5.3.1 Doors and Door Openings Weather proof doors shall be provided with an anti-vandal locking device over the door opening of each column as shown on the Drawings. The complete locking device shall be made from stainless steel. Door openings shall have internal reinforcement to compensate for the loss of stiffness in the columns caused by forming the door openings.

7.5.3.2 Service Slots

For flange mounted types of columns, cable entries shall be through the flange plates via a hole of suitable diameter as shown on the Drawings. A suitable duct for cable entry shall also be provided at the concrete base.

For planted root types of

columns, service slots shall be on the same side and vertically below the service doors.

7.5.4 Bracket Arms

Bracket arms shall be of suitable outreach as indicated on the Drawings and in the B.Q. The bracket arms shall be octagonal in shape for up to 2.0 m in length. For bracket arms longer than 2.0 m in length, the extra length shall be formed from Grade 43C tubular steel conforming to B.S. 4360. The bracket arms shall be arranged so as to give a 50 uplift as shown on the

luminaire shall be welded at the end of each bracket arm. After welding, etc., bracket arms shall be treated as described in Sub-Section 7.5.10 before being hot-dip galvanised.

7.5.5 Base-Plates

For flange mounted types of columns, flange-plates of substantial thicknesses as shown on the

Drawings shall be welded on to the columns.

For planted root types of columns, detachable anti-sink plates shall be supplied.

Base-plates, nuts and bolts, etc., shall be hot-dip galvanised after

manufacture.

7.5.6 Baseboards

A piece of baseboard shall be included in each base compartment for cable termination or control gears assembly. Baseboards shall be made from fibre board of 10 mm

thickness. Alternative baseboards made from galvanised perforated metal may also be used with the approval of the S.O. Baseboards shall be made to the dimensions as indicated on the Drawings and shall be fixed securely in position inside the columns.

7.5.7 Street Lighting Cut-Outs

Street lighting cut-outs shall be of a type manufactured for use in street lighting installations. They shall have facilities for double fusing loop-in loop-out terminals. The cut-out bases shall have a supply cable contact block rating of at least 50 A and shall be capable of accepting circular cable cores of up to 25 sq.mm copper 2-core or 4-core

cables as appropriate. Cut-outs shall be provided with adequate shrouding to prevent cross-phasing or

accidental contact with live metal.

The fuse carriers shall be self-aligning and shall accept any of the standard rated fuses for the purpose.

Each unit shall possess high mechanical and di-electric strength and shall be suitable for use in the tropics. Samples of complete cut-out units shall be submitted for the approval of the S.O.

7.5.8 Earthing Terminals

Columns shall be provided with a corrosion resistant terminal having substantial contact surfaces for the attachment of an earthing lead. This terminal shall be provided close to the door opening inside each column. Where bolts are used, they shall be not less than 6 mm in diameter and shall be provided with two suitable washers and nuts.

7.5.9 Cable Entry

Armoured cables brought into the columns shall be provided with compression cable gland terminations.

An appropriate type of earthing clamp shall be provided to bond the armouring of the cables which shall be effectively earthed.

7.5.10 Erection of Columns

Columns shall be installed in accordance with the manufacturer's recommendations and as shown on the Drawings. The Electrical Contractor shall peg out the positions of the columns for the approval of the S.O. before planting the columns.

Columns shall be erected such that the service doors shall face away from on-coming traffic except at parapets of bridges and retaining walls. At such locations, the

orientation of the service doors shall be determined by the S.O. After erecting each column, backfill shall be compacted by means of suitable ramming equipment.

7.5.11 Protection Against Corrosion Individual sections of the columns, base-plates, doors and bracket arms shall be protected against corrosion by hot-dip galvanising the sections both internally and externally, all in accordance with B.S. 729. All welding works shall be completed before galvanising.

Treatment prior to galvanising shall include degreasing, rinsing, pickling, further rinsing and fluxing.

The minimum average weight of the zinc coating shall be 460 g/sq.m for any individual test area.

The galvanised columns and bracket arms shall be of prime finish and of good uniformity, i.e. they shall be free from injurious defects such as blisters, flux and uncoated spots.

The planted sections of columns and the base-plates shall be factory-coated with bitumen using the hot-dipping process conforming to AASHTO M 190.

SECTION 8