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20. TECHNICAL SPECIFICATION FOR DISTRIBUTION BOXES

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This specification covers the design, manufacture, testing, pre-despatch inspection by purchaser and supply

of MS sheet, Distribution Boxes (DTBs) for housing electric connections of General category i.e. Domestic

& Commercial connections.

CONSTRUCTIONAL AND TECHNICAL PARTICULARS

2.1 The DTBs shall conform to drawing attached. It shall be for housing incomer and 8 No. outgoing cable

connections.

2.2 The DTBs shall be made from 20 SWG MS sheet by Deep Drawn Method. The base and cover of the DTBs

shall be individually in one piece without any welding except for fixing of the accessories like hinges,

clamps, handle etc. which shall be spot-welded. The cover of DTBs shall be fixed on two-tamper proof

inside hinges not visible from outside. The hinge pin diameter should be 3mm. Hinges shall be made from

2mm MS sheet. The pin of hinges shall have head on top so that it does not fall down after wear & tear.

The door of DTBs shall open from right to left by minimum 1200. The collar of the door (cover) in closed

position shall rest on the collar of body (Base) of DTBs. The collar of the door shall overlap the collar of

the body of DTBs by minimum 8mm. The collar of the body shall be provided with good quality rubber

gasket lining of min. 3mm thickness. Thickness of rubber lining shall be such that it provides proper

sealing between the cover & base of DTBs to avoid penetration of dust & ingress of water. Rubber lining

should be fixed with suitable adhesive so that the same does not get removed by itself on opening of the

door. The fixing arrangement of the sealing screws shall consist of 2mm thick strip (L-shaped) welded

from inner side of the body & another strip having U-shaped end with 3mm holes welded from inner side of

door of the DTBs. The length of the extended portion of the strips shall be such that the sealing screws in

tightened position are at a distance of about 5mm from end of the collar of the cover.

2.3 All the steel sections used in fabrication shall be carefully leveled and straightened before any works is

done on them. No rough edges shall be permitted anywhere through out the work and rubber entrance be

provided so that no cable gets cut from the entry point. The material of MMB shall be capable to withstand

mechanical, electrical and thermal stresses as well as the effects of humidity, which are likely to be

encountered during its service. All the spot welding work shall be done carefully so as to avoid overheated

spots, cavities, porosity, burns and dents etc. The surface should be properly cleaned before welding and

slag removed after welding.

2.4 A handle of minimum 60mm length and 10mm width and 20 SWG sheet thicknesses should be provided for

opening and closing of the cover.

2.5 2 Nos. holes with superior quality plastic/rubber cable glands shall be provided at the bottom of DTBs.

Internal diameter for incoming/outgoing gland shall be suitable for 16mm², 2-core stranded Aluminum

conductor PVC power cable. Glands shall be made such that internal diameter of glands provided for cables

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should be closed with the film of minimum 1mm thickness. Cable will go through the cable glands by

cutting the film of the glands.

2.6 Louvers for ventilation shall be provided on the sidewalls of the box as shown in drawing. 20SWG

adequately perforated sheet shall be welded from inside of the louvers suitable for IP-33 protection class.

2.7 DTBs shall be adequately protected against rust, dust water and corrosion both from inside and outside.

The DTBs shall have Light Admiralty Grey shade (IS-5:1993 Colour No. 697) on outside and glossy

white on inside. The DTBs shall be powder coated. The surface of the DTBs shall be properly pre-treated

and cleaned in 7 tank process and shall be applied with a powder coating of suitable thickness on outer side

and inside. The facility for 7-Tank Phosphating & powder coating shall be in house of the manufacturer to

ensure proper quality since these boxes are for outdoor applications.

2.8 Earthing screw of diameter M6 threads with washer shall be provided in the threads of L-shape clamp

welded to main body on left side. There should be no powder coating on earthing screws.

2.9 All the screws, studs and washers shall be properly galvanized.

2.10 The tolerance permissible on the overall dimensions & weight of the MMB shall be (±) 3.5% and (-) 2%,

respectively. Any weight on positive side will be acceptable. However, the tolerance for the fittings shall be

(±) 3%. In case of an order, the actual weight of sample shall be mentioned for supplies.

2.11 4 Nos. Tin coated busbars to be provided for 3 phases & 1 neutral of capacity 100A, 200A, 150A & 300A.

The busbars should have screw type arrangement to tight the incoming and outgoing cable sizes upto 35

mm2. 9 nos. holes in each busbar for phases and 14 no. holles to be provided on neutral bus bar. The busbar

should be installed on insulators of min 1” in size.

2. MARKING

PSPCL insignia and manufacturer name as shown in drawing shall be embossed on the door of the DTBs.

The word ‘PSPCL’ shall be marked indelibly on the Metal Meter Box. In addition Danger Mark is also

required to be provided on the DTBs as per drawing.

3. The box shall comply with the requirement of IP-33. The box shall be fully type tested as per requirement

of IS 13947(Part-1):1993. The type test shall be carried out from the govt.-approved laboratories &

certificate shall be submitted preferably along with the tender.

4. INSPECTION

The manufacturer shall give minimum 14 days advance notice about readiness of material at his works. The

material shall be inspected for conformity with PSPCL specification before the same is accepted. PSPCL

may also carryout stage inspection of the MMBs before powder coating. For this the manufacturer shall

intimate the manufacturing schedule in advance.

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5. PACKING:

The DTBs shall be suitably packed in 3 ply corrugated boxes in order to avoid damage in transit, handling,

storage & further transportation form store to field.

GUARANTEED TECHNICAL PARTICULARS (GTPs) FOR DISTRIBUTION BOXES

(DTBs)

Sr.

No.

Description Particular

1 Manufacturing Process

2 Size (in mm)

3 Sheet Thickness (in SWG)

4 Window Size

5 Sizes of each bus bar provided inside

the DTB

6 Powder Coating

7 Zinc coating on Nuts/ Bolts/ Washers

as per relevant ISS

8 Weight of DTB(in Kg)

9 Degree of protection

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