2.8.25 Ash Slurry Disposal Pipes and Valves

 

                        Combined Ash Slurry Disposal Pipes

 

                        The ash slurry disposal piping and associated fittings starting from slurry disposal pumps suction upto ash slurry dump area outlet to ash slurry sump shall be furnished complete with all couplings, steel supports, hangers, clamps, support, inserts, nuts, bolts, gaskets etc.

 

                        The ash slurry disposal pipe diameter should be designed considering slurry veloci­ty of 2.8M/Sec. (Max) in the pipe.

 

                        The minimum wall thickness of slurry piping shall be 9.52 mm  (minimum)

 

                        The routing of the ash slurry disposal pipes shall be indicated in the drawings enclosed with the bids. The pipelines shall be provided with adequately sized drain connections with blind flanges as per the final layout requirements.

 

                        Bidder shall conduct line surge studies for the ash disposal pipelines. Suitable arrangements as required to protect the system based on approved line surge studies shall be included in Bidder’s scope.

 

The ash concentration in slurry (W/W) shall be for 25% w/w for bottom and combined bottom and fly ash. For fly ash the same shall be 30% w/w.

 

2.8.25.1            Fittings

 

                        All fittings (bends, elbows, laterals & spool pieces etc.) used in ash slurry disposal piping  upto ash dyke shall be basalt lined/ Ni hard with flanged ends or integral wear back type alloy C.I. fittings.  Minimum thickness of wear back shall be twice the pipe wall thickness.

 

                        These fittings shall be as per good engineering practice and of large radius (Min. 3D) con­struction.

 

                        Alloy C.I. or Basalt lined spool pieces (as the case may be) of minimum 1.5 metre length shall be provided at the discharge of every fitting having an angle of 45°.and more.

 

                        All fittings (bends, elbows, laterals & spool pieces etc.) used in ash slurry disposal piping over ash dyke shall be M.S. fabricated with flanged ends with minimum 20 mm thick integral wear back.

 

2.8.25.2            Couplings

 

                        For ease of rotation and replacement of ash slurry disposal pipes at regular intervals of time for maintenance purpose, sleeve type couplings shall be provided.

 

                        Straight length of pipes without any intermediate coupling shall not exceed 50 metres.  It shall be possible to replace or rotate (as applicable) any fitting and any particular spool or pipe during maintenance without unduly disturbing neighbour­ing healthy joints and pipe spools. 

 

                        The coupling shall be capable of taking a minimum of 2° angular deflection and sufficient gap between ends of pipes at couplings shall be provided to take care of expansion in piping.

 

The thickness of coupling sleeve shall be 9 mm (min.)

 

                        The material of construction shall be as follows:

                       

Ash slurry line		ERW steel pipes to SAIL commercial Quality/API-5L Gr.B/IS:3589
Ii.   Pipe Fittings (Bends, Elbows, Laterals And Spool Pieces Etc.)
1.0	Material and Hardness		:	i)Upto Ash dyke Ni hard/chromo alloy C.I. or equivalent of minimum 400 BHN. Integral wear back of minimum 20 mm thickness.
				OR
				20 mm thick cast basalt lined MS fittings (MS shell of 6 mm thickness)
				Hardness : 8 mhos (minimum)
				Bending strength : 300 Kg/cm2 (minimum)
				Compressive strength : 4500 Kg/cm2 (minimum)
				ii) Over Ash dyke
				MS fabricated with minimum 20 mm thick integral wear back. The pipe thickness of fittings shall be 10 mm.
III.	Couplings
1.0	Type		:	Sleeve type couplings with minimum9.0 mm thick sleeve.
2.0	Material of Construction
2.1	Sleeve		:	Carbon Steel to ASTM A-36/BS EN 10025:1993 Grade S:275/355
2.2	Flanges/End rings		:	Carbon Steel to ASTM A-108. Steel end rings shall be formed from special hot rolled section bar, Free from circumferential welds.
2.3	Gasket
	(i) Material		:	EDPM to BS:2494:1990 Type D/Isoprene/Buna-N/Neoprene
						Test Procedure
	(ii) Properties		:	(a) Durometer hardness: Shore ‘A’ points	50 to 70	ASTM D-2240
				(b) Tensile strength min.ultimate:	1300 psi(min.)	ASTM D-412
2.4	Nuts & Bolts		:	Hot dip galvanised/spray galvanised as per IS:4759. Bolts, nuts and washers should be of similar material to those used for coupling housings/sleeves to minimise the possibility of galvanic corrosion