ATM PROJECT-electromic. work

3.13     BUILDER WORK

PART 1     GENERAL

 

3.13.1.1    DESCRIPTION OF WORK

Builder's work in connection with electric power and low  current systems comprises trenches, foundations, supports,  duct banks, manholes ,handholds, earthing pits, chases, holes  and similar works.

3.13.1.2    WORK INCLUDED

MANHOLES, HANDHOLES, DUCTS AND DUCT BANKS:

Below grade indoors and outdoors which are not an integral  part of structural slabs, beams and columns etc., including excavation, forming duct assemblies, reinforced concrete envelopes where required, backfilling, removal of excess  materials and restoring to grade.

TRENCHES:

For directly buried or duct assemblies including excavation ,sand layers, protective tile and marker tape,  backfill and making good to natural grade or existing surface as shown on the Drawings.

EQUIPMENT FOUNDATIONS/ BASES:

Which are not an integral part of structural slabs and not included on the Structural Drawings?

COORDINATION

Of all civil work required for electrical work including preparation of all necessary shop and construction drawings or supply of data for construction of civil work..

CHASING FOR CONDUIT:

Provision of sleeves, holding bolts brackets, grouting,  fixing in walls, plastering and making good to base surface for installations not provided in structural member or  slabs.

PART 3 PRODUCTS AND MATERIALS

 POLYVINYL CHLORIDE (PVC) DUCT:

Is to be nominal size shown on the Drawing minimum 3.2 mm wall thickness for 100 mm I.D. ducts and 4.7 mm I.D. wall thickness for 150 mm ducts.  Ducts are to be no sparking type and suitable for direct burial in ground.  Minimum tensile strengths to be 500 kg/cm2 and impact strength 5 kg/cm2.  Ducts are to be supplied in lengths of 6 m except for complementary sections which could be supplied in shorter lengths.  One end of each section is to be tapered.

CONCREATE:

To be approved by the civil engineer.

COVERSFORANHOLESANDHANDHLOES : 

Are to be cast-iron or steel framed medium duty concrete in fill type to take a slow moving wheel load as planned for the particular area in consideration and are to comply with BS 497.

PART 4   MANHOLES,HANDHOLES AND DUCT BANKS

3.13.4.1‏       ‏UNDERGROUND SYSTEMS:

Supply and install directly buried underground ducts or concrete enveloped duct-banks and construct cable pits  (hand holes and manholes) as indicated on the Drawings or as  required for installation of cables in accordance with approved construction drawings, with defined centerlines and  invert levels.

3.13.4.2   CABLE MANHOLES AND HANDHOLES:

Are to be concrete using   Asulphate resisting cement.  Provide waterproofing lining to all external surfaces of hand holes or manholes. Dimensions and reinforcement are to be as indicated on the Drawings or in accordance with standard details to be on approved construction/shop drawings. Provide all steel accessories for supporting cables, where necessary, pull-eyes anchored in manholes, drain pit and drain pipe as required.

3.13.4..3      CONCRETE ENVELOPE:

Provide concrete envelope for power distribution systems duct banks where required or shown on the Drawings.  Reinforced concrete envelope unless otherwise shown, is to be provided only where ducts cross water, gas, sewage mains and under roadways.  Provide 12 mm longitudinal reinforcing rods spaced approximately at 300 mm centers along bottom and sides of duct-bank.  Provide 10 mm U-shaped transversal bars spaced at 400 mm centers along the duct-bank.

3.13.4.4. DIRECTLY BURIED PVC DUCTS:

Provide directly buried ducts for outdoor lighting cable installations except at crossing with other services or roads, where reinforced concrete envelopes are to be provided extending at least 0.3m each side of such crossings.   Directly buried ducts are to be backfilled with sand and sieved compacted soil free from stones or other debris for reinstating the trenches to ground level.  Concrete tiles are to fully cover cable duct, extending a minimum of 50 mm over the duct outer sides, and placed 300 mm minimum below ground surface.  A warning tape or galvanized steel mesh is to be provided 200 mm below finished ground surface along duct runs.

3.13.4.5 UNDERGROUND DUCT INSTALLATION:

Excavate and drain trance provide well compacted hard ground, form duct assembly using special duct supports. Jointed ducts, using waterproof cement to manufacturer's recommendation, are to have at least an 80 mm overlap.  Junctions are to be waterproof and sand proof.  A 3 mm galvanized steel wire is to be left inside empty ducts to allow   for future pulling of cable. Steel wire is to be left with a length of 1 m outside duct bank at both ends, securely fixed to wooden bungs for holding the wire and sealing the duct.  Ducts ending in cable manholes or hand holes are to be neatly cut, reamed and set behind chamfered pre-cast concrete duct end block or terminated with appropriate bell mouth bushing, set in concrete wall.  Ducts not ending in manholes or hand holes are to be properly capped.

3.13.4.6          SLOPE:

Provide 1% slope for duct banks for draining to exterior manhole/ hand hole or locations instructed.

3.13.4.7          DUCT SYSTEM INSPECTION:

Directly buried duct runs or concrete enveloped duct-banks are to be inspected in the presence of the Engineer, before backfilling or concerning, by pulling a steel mandrel or other approved device, of diameter equal to 90% of inside diameter of duct and 500 mm long.  Mandrel is to pass through entire run of duct without getting stuck. Ducts which do not allow mandrel to be pulled through are to be  repaired or replaced to the satisfaction of the Engineer.

3.13.4.8          SEALING:

All conduits and ducts, active or spares, entering a building or a manhole are to be completely and adequately sealed at termination with approved plastic moulds or wooden bungs to prevent the entrance into the building of rodents, gas or vapors.

3.13.4.9 DUCT SUPPORTS:

Duct runs, whether with or without concrete envelopes are to be supported on preformed, non-metallic separators.  Any separator containing metal is to have the metal non-continuous and is not to form a magnetic loop in any manner.  Spacing between separators is to be close enough to prevent sagging of ducts and breaking of couplings and watertight seals.  Separators are to be secured with cords where necessary but not tie wires.

3.13.4.10   CLEANING THE DUCT BANK:

A brush with stiff bristles to be pulled through each  duct before pulling in cables.

3.13.4.11 FOUNDATIONS FOR EQUIPMENT

          ‏GENERAL :

Foundations are to be constructed with materials complying with other relevant sections of the Specification as appropriate.  They are to be dimensioned to suit equipment and coordinated with all other work on site.   Surfaces and levels of foundations are to comply with the Drawings and ý approved shop and construction drawings.

CONCRETE FOUNDATIONS:

Are to be reinforced.  Submit calculations to conform to specification requirements and local conditions.  Calculations are to be approved by the Engineer before any work is executed on site

SLEEVES OR DUCTS:

Are to be provided whether shown on the Drawings or not, and in accordance with detailed construction drawings and shop   drawings or as instructed by the Engineer.  Approval of installation on site is to be obtained before pouring concrete.

PART5 M ISCELLANEOUS REQUIREMENTS :

           SUPPORTING FRAMES:

          For switchgear supported over concrete cable trenches where required according to the Drawings and specific equipment designs, are to be coordinated, supplied and installed during placement of concrete.

COVERS:

For closing concrete trenches in electrical rooms and the like, where not provided for in other Sections of the Specification or not shown on drawings/ details, are to be supplied and installed to applicable standards.  They are to comprise flanged and reinforced chequered steel plates, tightly fitting to fixed and anchored galvanized angle or channel frames reinforced to take up any load anticipated in the areas under consideration. Covers and frames are to be coated with zinc chromate primer and finished with two coats of gray enamel.

‏          CHASING

For conduit in surfaces of concrete walls is to be coordinated with civil work program and is to be minimal.   Provision of forms for chases and slots in concrete slabs or  surfaces, such as for magnetic loops in parking systems, is  to be coordinated and shown accurately on construction drawings, ahead of pouring concrete or any other surfacing  material.

         

 MOUNTING BRACKETS

Supports, rails and tracks for supporting electrical installations are to be of galvanized steel and are to be fixed to walls, beams or the like by expansion anchor bolts of correct size and material.  Plastic inserts and lead anchors are not acceptable unless approved for specific light duty installations.  Drilling for anchor bolts must be made with appropriate electric drills and at approved positions.

END OF THIS SECTION