33 71 19 - UNDERGROUND ELECTRICAL SERVICES.pdf

MINISTRY OF HOUSING Western Sector Projects Sitework & Infrastructure OMRANIA and ASSOCIATES Project Specification

UNDERGROUND ELECTRICAL SERVICES SECTION 33 71 19 - 1

SECTION 33 71 19

UNDERGROUND ELECTRICAL SERVICES

PART 1: GENERAL

1.01 SECTION INCLUDES

A Underground electrical services including, but not limited to the following:

1. Duct banks.

2. Stub-ups.

3. Manholes.

4. Handholes.

5. Earth rod pits.

6. Concrete pads.

7. Cable warning signs and tapes.

1.02 RELATED SECTIONS

A Section 01 31 00 Project Management and Coordination.

B Section 0133 00 Submittal Procedures.

C Section 01 61 00 Common Product Requirements.

D Section 01 78 36 Warranties.

E Section 31 23 16.13 Trenching.

F Section 33 05 13 Manholes and Structures.

G Section 33 05 00 Common Work Results for Plumbing.

H Section 03 30 00 Cast-in Place Concrete.

I Section 26 05 00 Common Work Results for Electrical.

J Section 26 05 53 Electrical Identification.

K Section 26 05 13 MV Cables and Accessories.

L Section 26 05 19 LV Cables and Wires.

M Section 26 05 33 Electrical Raceways.

N Section 26 05 29 Equipment Connections and Supports.



O Section 26 56 00 Exterior and Street Lighting.

P Section 26 05 26 Earthing System.

1.03 REFERENCES

A SASO Saudi Arabian Standards Organization.

B SASO 14 Standard for uPVC Pressure Pipes.

C IEC 60346 Electrical Installation of Buildings.

D BSEN ISO 1452 Plastics Piping Systems for Water Supply and for Buried and above Ground Drainage and Sewerage under Pressure, Un-plasticized Polyvinyl Chloride (uPVC).

E BSEN 61386 Conduit Systems for Cable Management.

F BS 7671 Requirements for Electrical Installations (IEE Wiring Regulations).

G ASTM C 33 Standard Specification for Concrete Aggregates.

H ASTM D 1557 Test Method for Laboratory Compaction Characteristics of Soil using Modified Effort.

I SEC DPS SEC Distribution Planning Standards.

J SEC SDMS SEC Distribution Materials Specifications.

K SEC SDCS SEC Distribution Construction Standards.

1.04 SUBMITTALS

A Comply with section 0133 00.

B Submit catalogues, brochures, factory test certificates and samples of various items proposed for underground electrical services.

C Submit complete schedule of proposed pipes, accessories and fittings.

D Submit shop drawings indicating all required information about the underground electrical services, including the following:

1. Routing of underground ducts and their arrangement.

2. Sections indicating duct details and crossings of other services.

3. Termination of uPVC ducts to Manholes.

4. Detailed drawing indicating arrangement of ducts, spacing between ducts, spacers, etc.

5. Internal arrangement within manholes.

E Submit duct sizing calculations as required by the Engineer.



1.05 QUALITY ASSURANCE

A All items for underground electrical services shall be manufacturer's standard construction and materials except civil works such as excavation, backfilling and concreting. Where this conflicts with any part of the specification, the contractor shall so state at the time of tender.

B Manufacturers: Firms regularly engaged in the manufacture of such items of the types and sizes required, and whose products have been in satisfactory use in similar service for a period not less than 5 years. Preference shall be given to local manufacturers.

C All underground electrical services for power and communications shall comply with the requirements and standards of the electricity supply authority (SEC), telecommunications supply authority, BS and SASO.

1.06 DELIVERY, STORAGE AND HANDLING

A Comply with section 01 61 00.

B Avoid rough handling during unloading of pipes and other items for underground electrical services. Chains or wire ropes may be used, provided they are suitably covered, to protect pipes and other items from damage.

C Unloading by mechanical means such as crane or forklift may be used where pipes and other items for underground electrical services are delivered in bundles or in crates. However, consideration shall be given to the total weight and the lifting capacity of the mechanical equipment, and the observance of the statutory safety requirements.

D Pipes and other items for underground electrical services shall not be dropped or thrown to the ground, knocked against other conduits or against sharp objects that may cause permanent damage.

E In preparing for laying pipes in trenches, the pipes and fittings may be unloaded along the trench direct from the back of a truck. Ducts and fittings shall be unloaded on the side opposite to backfill. Fittings including end bells, couplings and other accessories such as solvent cement and lubricant shall be stored at the trench site under cover to prevent loss or damage.

F When storing on site, pipes and other similar items shall be placed at a level surface and shall be supported to minimize distortion, and protected from direct sunlight. Horizontal supports of adequate width shall be spaced not more than 1.5 meter from center to center beneath pipes to provide continuous and even support.

G Vertical side supports shall be provided at 3 meter spacing on rectangular stacks. The maximum free height of such stacks shall not exceed 1.5 meter.

1.07 WARRANTY


1.08 SEC/MUNICIPALITY COMPLIANCE

A Contractor shall comply with all applicable SEC distribution material specification, construction and planning standards for power distribution networks and municipality specification for road lighting. Some of the specifications and standards are attached with the contract documents for guidance, however contractor shall obtain copy of all applicable



specification and standards from the concerned authorities as required on site or instructed by the Engineer.

B Any conflict found between this project specification and SEC or municipality specification/standards shall be immediately brought to the notice of Engineer for final decision.

PART 2: PRODUCTS

2.01 ACCEPTABLE MANUFACTURERS

Not Used.

2.02 GENERAL

A Underground electrical services for power, lighting, low current systems, control cables and earthing shall comprise manholes and handholes interconnected via concrete encased PVC pipes, direct buried uPVC pipes or cable trenching, all as shown on the drawings and described in the specifications or required on site for proper installation and maintenance of electrical systems.

B Any trenching, backfilling, compaction and general grading required for electrical works shall be carried out in accordance with section 31 23 16.13 (Trenching). The excavation and backfilling for MV and LV power distribution networks shall also comply with SEC specification and standards, whereas trenching for street/road and landscape lighting shall comply with specification of local municipality having jurisdiction.

C Any metal frames, covers, louvers, etc. related to the works described under this section shall be carried out in accordance with section 33 05 13.

D Any cast-in-place concrete related to underground electrical services described under this section shall be carried out in accordance with section 03 30 00.

2.03 DUCT BANKS

A Duct banks shall be either direct buried type or concrete encased type, as applicable and required on site.

B Class 4 Un-plasticized Poly Vinyle Chloride (uPVC) pipes shall be used for direct buried or concrete encased underground duct systems. uPVC pipes and fittings including bends, joints, coupling, etc. shall be from the same manufacturer. The pipes shall be capable to withstand a pressure of 10 bars.

C uPVC pipes shall be suitable for a temperature range of 10 C to 60 C. Pipes within the duct bank shall be supported on plastic interlocking spacers, at intervals of approximately 1500 mm. A 40 mm minimum separation, edge to edge, shall be maintained, both horizontally and vertically, between the ducts.

D Jointing of pipe work and fittings shall be by use of solvent weld sockets carried out in accordance with manufacturer's instructions. Solvent weld cement shall be from the same manufacturer or of a type approved by the manufacturer of the pipe work.

E Additional ring seal joints shall be provided as necessary to account for expansion and



contraction.

F All duct banks shall have a 75 mm concrete cover on the top, sides, and bottom of the uPVC pipes. Anchorage shall be used to hold the ducts in place while pouring the concrete encasement.

G Where the duct bank enters a building below ground level, the conduit shall terminate in an appropriate fitting. An end bell shall be used on conduits entering manholes.

H After completion of the installation of cables in the duct bank, seal the ends of duct banks using special caulking compound of a putty-like consistency which shall be workable with the hands at temperatures as low as 1.7 oC, and shall not slump up to a temperature of 149 o

I A run of conduit shall not contain more than the equivalent of four quarter bends. Bends in conduit shall be made without reducing the internal diameter of the conduit. The inside radius of conduit bends shall not be less than one meter.

C and shall not harden significantly when exposed to air.

J Matching end bells and plugs, constructed of high impact plastic, shall be provided throughout the duct bank at the ends and in manholes.

K Each length of conduit shall be provided with one standard coupling. Couplings shall have a center step to ensure proper seating. Joints shall be made with solvent cement as recommended by the conduit manufacturer.

L Concrete encasement shall be class C20 concrete with 13 mm maximum size aggregate for all duct banks. For warning purposes, a red dye shall be troweled into the top surface after pouring the concrete.

M Expansion joints of 55 mm per 100 meters maximum shall be provided in duct banks. Additionally, a construction joint shall be installed if pouring of concrete is commenced any time after initial set of adjacent concrete. Neither expansion nor construction joints shall be installed under a roadway.

N For duct banks in stable soils, the soil below the duct bank shall be compacted to 90 % of maximum density to a minimum depth of 300 mm. A dewatering system shall be used to lower the water table below the final excavation depth to eliminate disturbance of in-situ soil densities.

2.04 STUB-UPS

A Stubs-up for electrical equipment connections and other requirements shall consist of either 100 mm or 150 mm diameter hot double-dipped galvanized rigid steel conduit entirely encased in concrete.

B Rigid steel conduits and bends for stub-ups shall comply with the requirements of section 26 05 33.

C The bends for stub-ups shall be 90 degrees with a minimum radius of 1200 mm.

D Bends for stub-ups shall serve as transition between PVC conduits embedded below grade and rigid steel conduit installed exposed on surface. Such bends shall be provided with a PVC steel coupling on one end and a threaded male or female adapter on the other end.

E Use rigid aluminium or galvanized steel conduit for bends and for all sections extending above finished grade level. For ducts carrying single conductor cable, use only aluminium



conduit.

2.05 MANHOLES

A Appropriate type and size of manholes shall be provided as shown on the drawings or required on site in compliance with the requirements of local codes and Saudi Electricity Company (SEC) or the telecommunications supply authoritys regulations.

B Manholes for communication and low current systems shall be constructed in accordance with the standard practice and requirements of the telecommunications supply authoritys regulations.

C A sump pit shall be built into the base slab directly beneath the manhole opening to collect and retain any water present in the manhole. Periodic maintenance may be required since sump pumps will not be permanently installed.

D The duct bank manhole/interface shall include an expansion joint to take up longitudinal movement due to expansion and construction of the duct bank. This joint shall also act as a water stop to prevent water from seeping inside the manhole.

E The exterior of the manhole shall be waterproofed, with a bituminous coating in accordance with section 03 30 00.

F Each manhole shall have two cable pulling irons opposite each duct bank entrance.

G Access to deep manholes shall be through a chimney. Permanent ladders or rungs shall be installed, if required by the Engineer on site or shown on the drawings.

H Manholes shall be provided with earth-rods and cable supports when required as per the local codes or SEC standards.

I Frames and covers of all manholes shall be heavy duty, cast iron, round or square with solid type gasket lids, and countersunk locking devices. Covers shall seal tightly and not rock when installed.

2.06 HANDHOLES

A Handholes may be formed either monolithically or built up to designed sizes by combining several concrete sections cast in various shapes and sizes.

B Handholes shall be provided with cast iron covers, sumps, ground-rods, etc. as shown on drawings or required as per the requirements of local codes or other applicable standards. Section joints shall be grouted.

C The frames and covers of all hand holes shall be heavy duty, cast iron, round or square with solid type gasket lids, and countersunk locking devices. Covers shall seal tightly and not rock, when installed.

2.07 EARTH ROD PITS

A Earth rods pits shall be provided for all earth rods in accordance with the requirements of section 26 05 26 (Earthing System).

B Earth rod pits shall be precast concrete of either square or round section with cover.

C Covers of earth rod pits shall have appropriate markings as approved by the Engineer.



2.08 CONCRETE PADS

A Concrete pads shall be provided for all pad mounted equipment whether shown on drawings or not.

B Concrete pads shall be minimum 150 mm high, unless otherwise indicated, complete with steel reinforcement and necessary bolts, anchors, etc. required for the proper installation of pad mounted equipment.

C Structural calculations for concrete pads supporting heavy equipment shall be submitted for Engineers approval before commencement of work on site.

2.09 CABLE WARNING SIGNS AND TAPES

A Where cables are directly buried, cable warning signs shall be installed to minimize the likelihood of damage to the cables by excavation. These signs shall be suitable for mounting on a riser pole, substation fence or separate stakes to suit the installations.

B Posts for cable warning signs shall be placed as close to the cable as practical, but not closer than 900 mm horizontally from the cable.

C Cable warning tapes shall be provided in accordance with the requirements given in section 26 05 19 (LV Cables and Wires). Tapes shall be placed at least 300 mm above the buried cables and shall cover full width of the cable trench.

PART 3: EXECUTION

3.01 INSPECTION


B Establish and propose exact routes and requirements of underground electrical services for approval of the Engineer, after co-ordination with all other existing or new underground services, before commencement of the work on site.

C Examine the areas and conditions under which the underground electrical services are to be installed, and correct any unsatisfactory conditions detrimental to the proper and timely completion of the work. The contractor shall not proceed with the work until all unsatisfactory conditions have been corrected in a manner acceptable to the Engineer.

D Ensure that a responsible and competent supervisor is present during concreting operations. Advise the Engineer in advance of concreting, so that he may inspect the ducts up to placing, be present during the pour and inspect the complete duct bank before backfilling.

3.02 EXCAVATION AND BACKFILLING

A Before commencement of the excavation, check the presence of any existing underground services by means of appropriate tools and equipment. The contractor shall be penalized for damaging any existing services in accordance with the rules and regulations set forth by the owner and described in section 26 05 00.

B Carry out excavation and backfilling in accordance with the requirements of section 31 23 16.13 (Trenching).



3.03 DUCT BANK INSTALLATION

A Direct buried PVC ducts shall have a minimum dry sand cushion of 150 mm and a minimum dry sand cover of 300 mm.

B Depth of direct buried PVC ducts and PVC coated rigid steel conduits shall not be less than 500 mm from finished grade level to the top of conduits.

C Provide underground pipe bridges to support the duct bank where it crosses previous excavations or other excavations which are part of this contract.

D Where additional excavation below the trench bottom is required, slope the walls at 45 degrees along the direction of the trench, and backfill with granular material compacted to 95% of modified proctor. The trench bottom shall be flat or convex in cross section.

E Prior to laying pipes for concrete encased duct banks, construct a concrete skim slab not less than 50 mm thick. Provide base spacers across the skim slab at 1500 mm intervals, leveled to the grades indicated for the bottom layer of ducts.

F Trenches and duct banks shall be graded so that conduits will have a fall of at least 75 mm per 30 m towards the lower manholes or from the high point of the section towards the manholes or from the building towards a manhole.

G Construct a dry well of crushed stone at the low points of the duct bank, and where indicated at manholes. Dry wells shall be pits not smaller than 500 mm square x 1200 mm deep below the invert elevations of the low points of the duct banks or manholes.

H Lay ducts with configurations and reinforcement as shown, using plastic or other suitable intermediate spacers to maintain the correct spacing. Maintain spacing between ducts of not less than 40 mm horizontally and vertically. Concrete encasement surrounding the duct bank shall be rectangular in cross-section, having a minimum concrete thickness of 75 mm beyond any surface of the conduit.

I Provide intermediate spacers at maximum 1500 mm centres, and stagger in adjacent layers. Use anchors, ties and trench jacks as required to secure the ducts. Ensure that ducts are not broken, damaged or disturbed during placing of the concrete. Remove weights or wood braces before the concrete has set, and fill the voids.

J Top of concrete encased duct banks shall be 500 mm minimum below finished grade and shall connect manholes and handholes as shown and required on site. Where a duct bank connects to a building, adapt the duct bank, at one meter beyond the building exterior wall, to the building conduit with the required couplings.

K Changes in direction of duct bank runs shall be accomplished by using special couplings limited to 5 degree and/or 45 degree bends having a 1 m radius sweep with straight sections of ducts between changes of direction and S sweep sections having a minimum of 500 mm offset.

L Where duct bank enters manholes, conduits shall terminate in end bells. Clean each conduit thoroughly before laying. During construction and after completion of the duct banks, plug the ends of conduits to prevent water washing mud into the conduits. Take particular care to keep the conduits clean of concrete or any other substance during the course of construction.

M Securely anchor duct and brace with intermediate and base plastic spacers to prevent movement during the placement of concrete.



N All duct banks shall enter manholes through rectangular openings of suitable dimensions provided in walls. Such holes shall be sized to properly receive the duct, but shall not be too large for proper caulking. The space between duct banks and manhole walls shall be caulked tight with lead wool.

O Reinforcing steel and metal ties may encircle all ducts, but shall not encircle any duct or group of ducts in the duct bank.

P Place concrete carefully and spade continuously to ensure a flow between and under the individual ducts and to provide a solid mass of concrete. Vibrators shall not be used, until specifically required by the Engineer.

Q Cut, ream and taper ends of ducts in the field in accordance with the manufacturer recommendations, so that duct ends are equal to factory made ends.

R Immediately after placing of concrete, pull through each duct a mandrel not less than 300 mm long and of a diameter of 6 mm less than the internal diameter of the duct, followed by a stiff bristle brush to remove all sand, earth and other foreign matter. Work the mandrel through the ducts carefully to avoid disturbing or damaging ducts where concrete has not set completely.

S Replace or repair to the approval of the Engineer any completed ducts which are defective or unsatisfactory in any way, at no additional cost to the contract.

T Provide a 6mm dia (minimum) nylon rope in each conduit after cleaning, after which the conduits shall be capped/plugged immediately.

U Ensure that concrete has attained 50% of its specified strength before backfilling.

V Back opening in ducts with asbestos, braid packing and seal the asbestos packing with permanently resilient silicon base non inflammable water proof compound.

W Pull a stiff bristle brush and a swab to remove water, mud and fine sand through each duct immediately before pulling in cables.

3.04 STUB-UP INSTALLATION

A Comply with applicable requirements of section 26 05 33.

B Exact stub-up locations and termination requirements for each item of equipment shall be verified on site, before commencement of laying underground or under floor PVC conduits for required power and control wiring.

C Where extensions of PVC conduits above grade are required as stub-ups, a transition bend having PVC/Steel coupling on one end and threaded male or female adapter on the other end shall be used.

D The PVC coated rigid steel transition bend or conduit shall extend minimum 150 mm above grade. Unless otherwise specified or indicated on the drawings, a concrete envelope 100 mm high above the finished floor shall be formed around such risers to minimize corrosion at point of emergence. The top of the envelope shall be sloped for drainage.

3.05 CONSTRUCTION OF MANHOLES AND HANDHOLES



A Manholes and handholes shall be constructed of precast or cast-in-place concrete as approved by the Engineer to sizes shown on the drawings. Horizontal concrete surfaces of floors shall have a smooth steel trowel finish.

B Frames and covers shall be watertight and covers shall fit the frames without undue play. These shall be free from warp and blow holes that may impair their strength or appearance.

C Steel and iron shall be formed to shape and size with sharp lines and angle and shall have a smooth finish.

D Provide all necessary lugs and brackets.

E Set pulling-in irons and other built-in items in place before pouring concrete.

F When required by SEC or local authority having jurisdiction, provide a 3 meter earth rod external to each manhole and handhole and an earth bar in each manhole and handhole affixed to the wall above the duct bank box-outs. Connect to earth rod using 70 mm bare copper conductor and bond earth conductors associated with each power cable inside the manhole or handhole.

3.06 CABLE WARNING SIGNS AND TAPES INSTALLATION

A Direct buried cables shall be installed in accordance with SEC specification/standards and the requirements for external cable installation given in sections 26 05 13 (MV Cables) and 26 05 19 (LV Cables & Wires).

B Direct buried cables shall have a minimum dry sand cushion of 100 mm below the cable and a minimum dry sand cover of 100 mm from top of the cable.

C Cable warning signs shall mark all direct buried splices and shall be placed at intervals not exceeding 30 meter along the cable route.

D Cable warning tapes shall be installed 300 mm directly above cable throughout the entire cable route and shall cover the full width of cable trench.

END OF SECTION

SECTION 33 71 19

33 71 19 - UNDERGROUND ELECTRICAL SERVICES.pdf

Documents

Transcript of 33 71 19 - UNDERGROUND ELECTRICAL SERVICES.pdf