Provn of Copper plate earthing Pits at AFS Suryalanka

Amount

M&L for Chemical earthing with copper earth plate electrode of size 900 X 600 X 5mm buried directly in ground, earth pit not less than 2.25 mtr depth below ground level (1.25 mtr width) and with top edge of the plate not less than 1.35 mtr below ground level connected to copper earth lead strip of size 50mX6 mm (length not more than 7.5 mtr and connected to test point) by means of bolts, nuts , check nuts and washers of tinned copper / brass in addition to brazing of all joints including excavation and earth work, disposal of surplus soil to a distance not exceeding 50 mtr , Charcoal dust 250Kg, common Salt Crystal 200kg and Magnesium Sulphate Crystal 100kg to be used in pit , GI pipe light grade of 80 mm bore as protection pipe, GI pipe 25mm dia medium grade of enough length to reach just above copper plate fitted with funnel with wire mesh, along with cap and running water tap to be provided for keeping the soil wet, PCC pit with PCC (1:3:6) pre cast chamber of internal size 40x40x30 cm and 40 mm thick RCC 1:2:4 type B1 using 20 mm graded stone aggregate as in cover slab (42X42cm) reinforced with 8 mm dia TMT bar both ways at 100 mm C/C complete all as specified and conforming to IS 3034-2018 : Code of practice for earthing all as specified and as directed.

Note for item No. 01 :- The following precautions to be observed while erecting the earth pits :- (i) The copper plate and the copper strip to be brazed. (ii) Alternate layers of charcoal and salt shall be laid in the earth pit on top of the copper plate. Minimum five layers to be laid. (iii) After laying of alternate layers of charcoal and salt, a 2 inch layer of magnesium sulphate needs to be laid. Balance volume to be filled with soft black soil. (iv) The chemical, salt and magnesium sulphate should never be mixed but are to be laid in layers only. (v) Ceramic spacer to be placed between the copper strip and the wall while extending the earth to the equipment. Large holes not to be drilled into the copper strip for fixing ceramic spacers.

S&F earth continuity conductor or main earthing lead fixed to wall or batten or recess or chases or buried in ground or drawn in conduit pipe or fixed to poles or any other indicated situation as required of size 50 x 6 mm copper strip on necessary insulators for every 1 mtr complete all as specified and as directed.

M&L for earth plate marking made up of angle iron 25x25x3 of length not less than 1.0 mtr, (0.5 mtr above GL) fixed with MS plate of 300 x 150 mm x 2mm by welding including two coats of red oxide paint with one coat of anti corrosive paint of colour omplete all as specified and as directed Note:- The following shall be written in marking plate with anticorrosive paint. "Earth Pit Nos : _____ ER Value : _____ Measured on : _____ Next Due on : ____

S&F Test point terminal block made of gun metal or phosphorus bronze size 75x75x25mm drilled and screwed including 3 nos. 8mm dia 25mm long hex. head screw complete all as specified and directed.

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