2.8.29 Vertical Sump Drainage Pumps

2.8.29               Vertical Sump Drainage Pumps:

 

                        The equipment shall be vertical centrifugal type with separate discharge pipe and shall be capable of developing the required head at rated capacity for continuous operation.

 

                        Individual components of the identical pumps shall be interchangeable.

 

                        Head-capacity curve of the pump shall be rising type upto the shut-off condition.

 

                        The characteristics curves of each of pumps shall match each other for equal load sharing in case of parallel operation.

 

                        Standard type pumps with a proven record of reliability shall only be provided.

 

                        The pump shall be capable of handling equipment/floor drain water which will be contaminated with all kinds of suspended impurities and abrasive ash particles.  The pump shall be designed and equipped for indoor/outdoor operation, as specified.

 

                        Continuous motor rating (name plate rating) at 50°C for vertical sump drainage pump shall have at least 10% margin above the maximum load demand of driven equipment in the entire operating range (including run out condition of pumps in case of parallel operation) to take care of system frequency variation.  The maximum load demand shall include the drive losses in the transmission system.

 

2.8.29.1            Construction Features

 

            ●          Column Pipe

 

                        The column pipe shall serve as a housing for the line shaft and bearing and support for bowl (casing).  The line shaft bearing shall be supported from the pump column pipe.  Individual sections of column pipe shall be coupled by flanged joints.  The flange outside diameter shall not exceed the bowl outside diameter.

 

            ●          Casing

 

                        (i)         In addition to housing the impellers properly, the casing shall provide a smooth path to water passages and shall be hydraulically designed to minimise radial thrust.

 

                        (ii)        Suitable sealing arrangement shall be provided to prevent the leakage of pumped liquid into the column pipe.

 

            ●          Impeller

 

                        (i)         The impeller shall be semi open or open (non clogging) as per standard design of the Manufacturer.  All rotating parts including the impeller shall be statically and dynamically balanced.  The critical speed of all the rotating parts shall be substantially above the design speed.

 

                        (ii)        Impellers shall be securely fastened to the impeller shaft with keys, taper bushings or locknuts.

 

                        (iii)       The impeller shall be specifically designed to pass large solids or unscreened liquids.  The clearances between stationary and moving parts shall be such as to allow sustained performance without excessive maintenance.

 

            ●          Pump Shaft-Motor Shaft Coupling

 

                        (i)         The pump shaft shall be connected to motor shaft by a heavy duty rigid/flexible coupling or the pump shall be V belt driven.

 

                        (ii)        In the case of shafts with rigid couplings the maximum permissible error in the axial alignment of the pump shaft with the axis of the motor shaft shall be limited to maximum of 1.00 mm.

 

            ●          Discharge Pipe

 

                        (i)         The discharge pipe should be terminated above the base plate or mounting channel.  Type of end connection shall be as specified in data sheets.

 

                        (ii)        No support shall be provided for the bottom elbow (near pump bowl) to facilitate easy removal of the pump from top without the necessity to go down to the sump for removal of bottom support, if provided.

 

            ●          Base Plate

 

                        The base plate shall accommodate the column pipe level switches, oil lubricator and discharge pipe so that the whole pump unit can be dismantled from the top by removing the base plate.  The base plate size shall be such as to cover the full opening on top of the sump with adequate clearance between the sump edge and foundation bolts.  In case the size of base plate becomes too large either to cover the sump or to accommodate the discharge pipe, then smaller base plate with mounting channels may be provided. The channel length shall be adequate to span the opening in the sump and the spacing between the channels should be adequate to facilitate removal of pump without disturbing the channels.  Also the discharge pipe shall be supported from the channel by removable clamps.

 

            ●          Shaft

 

                        (i)         The design of the shaft shall also take into consideration the critical speed of the shaft which shall be minimum 20% higher than any operating or run away speed.

 

                        (ii)        Individual sections of the shaft shall be interchangeable.

 

 

            ●          Line Shaft Coupling

 

                        The type of couplings shall be such to prevent loosening during reserve rotation.

 

            ●          Line Shaft Bearing

 

                        Bearings shall be oil/water lubricated. Line shaft bearings shall be spaced not more than 1.5 meters apart.  Suitable oil lubricators (mounted on top of the base plate) with lubricating pipe to each bearing shall be provided for supplying the lubricating water to the bearings.  For lubrication purpose clarified water shall be available at a head specified elsewhere.  If the clarified water is required at a higher pressure than specified above, the same may be boosted up by separate set of pumping system.

 

            ●          Thrust Bearing

 

                        Suitable thrust bearing shall be provided to take the axial thrust.

 

            ●          Shaft Sleeves

 

                        Replaceable shaft sleeves shall be furnished.  The shaft sleeve shall be securely locked to shaft to prevent loosening while in operation.

 

            ●          Suction Bell

 

                        The pump shall be complete with adequately dimensioned suction bell, to guide and streamline intake fluid.

 

            ●          Impeller Adjustment

 

                        The pump shaft shall have suitable arrangement for vertical adjustment of impeller position from an accessible point.  The impeller adjustment shall be such that the impellers run free in any installed condition in spite of the extension of line shaft caused by hydraulic down thrust, the weight of the shafting and impellers.

 

            ●          Wearing Rings

 

                        Replaceable type wear rings shall be provided for casing and/or impellers wherever applicable.

 

            ●          Accessories

 

                        All accessories as required for efficient and safe operation of the pump motor sets shall be furnished by the Bidder, and these shall include but may not be limited to the following :

 

                        (i)         Base plates together with foundation bolts and nuts.  The base plate shall accommodate the discharge pipe, which is to be terminated above the floor level.

 

                            (ii)        Motor Stool.

                       

(iii)       Non-return valves and gate valves on pump discharge lines

           

(iv)       Lifting lugs, eye bolts etc.

 

                        (v)        Pre-lubricating tank with accessories (if necessary).

 

                        (vi)       Sleeves and inserts to be embedded in concrete.

 

                        (vii)      Coupling guard, if necessary.

 

2.8.29.2            The sump drain pumps shall be provided as follows:

 

S. No.	Description	Sump Drainage Pumps for Ash Slurry Pump House	Sump drainage Pumps for B.A. Slurry transportation pump house (if applicable)		Sump drain age pumps for silo area
1.	Type	Vertical, Centrifugal, single stage, semi-open or (open non-clogging) type impeller.
2.	Duty	Intermittent, However, to be designed for continuous operation.
3.	Fluid to be pumped	Slurry pump house floor suspended solids drain and sump drain with(30% ash particles by weight) Pump shall be able to handle 60 mm lump size of ash		B.A. slurry pump pit drain with suspended solids(30% ash particles by weight).		Silo area drains (with 30% particles by weight)
4.	Capacity and total dynamic head (Guaranteed)	80M3/Hr, 15MWC		80M3/Hr,15MWC		80M³/ Hr @ required head to pump the drain back to combined ash disposal pump house
5.	Suction Condition	…………………Submerged……
6.	Number of pumps	Two (1W+1S)		Two (1W+1S) For each unit		Two (1W+1S)
7.	Pump speed (Max.)	………………. 1000 rpm …………………………………………….
8.	Type of coupling between pump & Motor	…………….. Directly driven through flexible or rigid coupling/V-belt driven
9.	Location of pump thrust bearing	…………….. in Motor Stool ……………………………………..
10.	Material of Construction
	(i) Casing	……………Alloy cast iron (350 BHN) (Min 2.7% Ni; 1% Cr.)…………………………………………….
	(ii) Impeller	………………alloy cast iron (350 BHN          (Min 2.7%, Ni, 1% Cr.)……………………………………………
		……………….. Stainless Steel …………………………………..
	(iii) Impeller shaft
	(iv) Line shaft	……………. EN – 8 to BS:970 ………………………………..
	(v) Column pipe and discharge pipe	Fabricated steel to pipe           IS:226 (Minimum 6 mm Thk) …………. ……………………
	(vi) Shaft sleeve	Hardened stainless steel to 400 BHN
	(vii) Base plate	Steel to IS:226 upto 20 MM thickness and IS:2062 over 20 mm thickness

 

 

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