After all weld inspection and joint coating we can do the backfilling of the pipe as per specifications. I n some case the sand or crusher dust have to filled up to the top of the pipe.
Fix the air valve stems during laying itself along with flange and suitable ball valve specials; it will be very useful during Hydro test of the pipe line also.
Fix the scour valve stems with valve and specials so that it will be used to drain water after Hydro test and commissioning of line.
Fix theAir cushion valves if necessary in particular places to avoid the vacuum pressures developing in side pipe line when surge effects.
Backfilling should be done layer by Layer to achieve good compaction and good levelling and formation after laying.
Precautions will be taken during laying and backfilling there will not be entering of rain water or soil inside the pipe line.
During laying itself the unwanted materials like electrode bits scraps other materials are to be removed carefully.These materials abstract the flow of water and all these materials will fall in Delivery chamber during commissioning,
Man holes 600 mm in Dia will be provided every 500 meter of pipe line which will be very useful during maintenance. Or Manhole cumAir valve also will be provided for better result.
Two Engine mounted Concrete mixture will be placed both end to mix the cement and sand and the water facility also [to be arranged near the machine by pump
If possible the root run will be done by E7018 Electrode which will give good strength and further layers’ may be by E 6013 electrode
TheAir valve,Air cushion Valve, Scour valve and HydroTesting Dummy Location will be finalized as per the site condition only.And it should be noted inAS LAID DRAWING.
After Hydro testing the gap closing will be done very carefully i.e. the measurement of gap piece will be prepared as per the whether condition and the contraction, Expansion limit also will be considered in correct manner so that we can able to maintain proper root gap and joint.
Aspecial manhole near gap closing area will be made to facilitate inside welding of spool piece.
Now we can apply the mortar from the mixture machine by manually both sides of the pipe.The pouring of the mortar may be done automatically by installing a chute method i.e. the conveyer should travel entire the pipe length to pour the mortar. Now we can see the mortar deposits inside the pipe uniformly by centrifugal force.
All the bare pipes after laying will be coated either cement mortar or Wrapping coating properly to prevent rust forming on the pipe base metal.
Manifold connections are to done proper way i.e. there may be valves and flow meters and surge vessels may come. So the proper space is to allowed accordingly the connections are to be given.
All specials like bends, reducers, Wye Piece and Transition pieces are to be fabricated separately and to be erected during laying of pipe.
The bends above 22.5 degree will concreted by thrust blocks so that we will save the pipe line from water hammering.
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