2.8.18 Instrument Air Compressors and Drives

2.8.18    Instrument Air Compressors and Drives

 

                        Air compressors shall be designed for continuous operation with high efficiency to satisfy the system requirements. Satisfactory operation in parallel shall be ensured without any uneven load sharing, undue vibration, noise etc.

 

                        The design shall incorporate every reasonable precaution for the safety of all operation and maintenance personnel.  Each compressor unit should have all moving parts protected by a guard.

 

                        The scope of supply shall include all the necessary compressed air plant complete with compressor coolers, necessary isolating and non-return valves, pressure relief valve, water separators, silencers and vent pipe work, which shall be ducted to a safe discharge outlet.

 

                        4×100%  ( 2 working + 2 stand by) capacity instrument air compressors shall be provided for both units.

 

                        The output from each set of working compressors (as applicable), expressed as free air delivered (FAD) at ambient condition, shall be sufficient to meet the instrument air requirement for one unit and silo area air requirement such as silo bag filter cleaning valve actuation. etc.   At least 10% margin shall be provided on compressor capacity over and above the maximum flow requirement. The bidder shall furnish detailed calculations of compressor sizing with the bid. A discharge pressure of  8 kg/cm2 with three steps of unloading  and design ambient of 50 degree C ambient air temp and 100% RH shall be considered for sizing of the compressors.

 

                        Compressors shall be of reciprocating oil free type.  All instrument air compressors and their drives provided under this contract shall be completely interchangeable.

 

                        The wall thickness of the cylinders shall be sufficient to withstand the maximum cylinder pressure and to permit successive re-boring without hazard.

 

 

                        Piston shall be provided with piston rings to seal the leakage of compressed air. The piston rings shall be self-lubricating material preferable graphite impregnated teflon. In case the cylinder is horizontal, suitable slipper rings shall be provided to avoid rapid wear and/or distortion of the piston ring.

 

                        Each compressor shall have an inlet filter  (dry type) unit to protect the compressor.  The filter inlet area should be large enough to ensure frequent filter changes are not required.

 

                        A crank shaft driven positive displacement lubricating pump shall be used for lubricating the bearings and any other parts needing lubrication.

 

                        Cooling water requirement, if any, shall be arranged by the bidder.

 

                        Bidder shall include an inlet and/or outlet silencer so that each compressor unit complies with the noise requirements.

 

2.8.18.1            Air Receivers

 

                        Each compressor shall be provided with an air receiver of ample size of so that delivered air pressure is kept within  ±5% of rated pressure without excessive start/stop operation in the working cycle.

 

                        Air receivers shall be located convenient to compressor discharge.  The receivers and associated fittings shall comply with BS:5169 and BS:1123 or other approved standards.

 

                        The receivers shall each be supplied complete with test certificate, safety relief valve, fusible plug, pressure gauge, flanged inlet and outlet connections, inspection manhole (in accordance with Clause 25.2.4 of BS:5169-1975, or similar international equivalent), screwed drain connection, automatic drain trap with balance line, drain trap isolating valve, balance line isolating valve and manual drain valve, nameplate, support frame or legs, and a set of suitable foundation bolts.

 

                        As far as possible the design, manufacture and performance of air receivers shall be in accordance with the following latest applicable standards :

 

                        1)         IS : 2825 – Code for unfired pressure vessels.

 

                        2)         ASME-Sec. VIII Div.-1 Code for unfired pressure vessels.

 

                        3)         BS : 487 – Fusion welded steel air receivers.

 

                        4)         IS : 7936 – Air receivers for compressed air installations.

 

2.8.18.2            Water Separators

 

                        The Bidder shall supply water separators complete with automatic drain traps.  Each separator shall be rated for twice the individual compressor flow at 1 bar above maximum operation pressure.  Each water separator shall have flanged connections.

 

2.8.18.3            Air Drying Plant

 

                        One no. each for each compressor Air drying plant shall receive compressed air saturated with moisture.  They shall be capable of operating continuously to provide reliable, moisture free compressed air supply.  Dew point of the outlet air measured at the operating pressure shall be as mentioned in the data sheet or lower throughout the working of the drying plant.

 

                        The adsorber tower shall be sized for a drying cycle (i.e. the time any particular tower is adsorbing) of period as specified (8 hours). After this period the adsorber tower will be put under reactivation operation while the other will take over the duty.

 

                        The above stated change-over from drying duty to reactivation or vice-versa shall be fully automatic with manual over ride facility.

 

                        The four way valves shall not be used in the air drying plant piping circuit for changeover facilities.

 

                        Air drying plant shall be complete with all pipings, valves, instruments and other accessories as required for safe and satisfactory operation and reactivation of the plant.  Open through system shall be used for reactivation.

 

                        Atmospheric air is filtered and is passed through the wet desiccant by a blower with the help of proper valve arrangements after heating it to required temperature by an electric heater.  This moist air is exhausted to the atmosphere. Suitable solenoid and pressure reducing valves for slow depressurisation and re-pressurisation of the adsorber tower shall be provided for such case.

 

                        The filtering media for prefilter shall be cable/candle type ceramic filter designed to withstand at least 50% of the static pressure applied as differential pressure.  Pre-filter shall be provided with isolation valves.

 

                        Quantity of desiccant shall be calculated giving the consideration to the residual moisture content at the end of regeneration cycle.  Bidder shall submit detailed calculations in support of material and quantity of desiccant offered alongwith curves (with ref. to the source of these curves) indicating variation of adsorption capacities with temp. at various R.H. at working pressure of 8 kg/cm2(g).  Bidder shall also indicate the residual moisture left in the desiccant after regeneration.  For calculating the desiccant quantity, adsorption capacity and density to be considered shall not exceed 10% and 550 kg/m3 respectively. Dew point of outlet air shall be considered as (-) 40 degree C at 1 ata pressure.

 

                        Desiccant beds shall be designed with sufficient cross-sectional area for air flow resulting in low air velocity and consequently low pressure drop.

 

                        The adsorbent material shall be supported at top and bottom by stainless steel (AISI 304) 40 mesh strainer, on mild steel plates.

 

                        Adequate free board (minimum 20% of desiccant bed depth) shall be provided to dislodge the entrained particles from the adsorber.

 

                        The adsorber tower shall be provided with suitable inspection window made of glass/pespex for observation of the adsorbent conditions and desiccant filling and removal connection.

 

                        Each air drying plant shall be complete with suitable after filters in the down stream of the adsorber towers.  After filters shall be provided with individual isolating valves, 100% standby or bypass valves.  After filter shall prevent any carry-over of desiccant particles with the effluent air stream.

 

                        For reactivation air drying plant shall be provided with the air blowers and drive of sufficient capacity and pressure for supplying air.

 

                        Dry type air filter at the suction of blower shall be provided.

 

                        Heater shall be used to heat the air upto the required temp. for the purpose of reactivation of wet desiccant bed. Suitable temp. and pressure indication shall be provided at the outlet of the heater shell.  The heater shall be fabricated as per IS:2825 or approved equal.  The heater shall be thermostatically controlled, electric type and shall preferably of flanged type so that replacement burnt out heating element or other maintenance work is easy.

 

                        All pressure vessels such as moisture separator, prefilter and after filter casings, adsorber towers etc. shall be designed as per IS:2825 or approved equal.  All vessels shall be Class-II type as per the said standard.  Adequate provisions for manhole/handhole, relief valve, draining trap station shall be made.  Internal surfaces of all the vessels shall be suitably protected against corrosion and rusting.

 

Material of construction shall be as follows:

 

Compressor	To suit service condition and as per relevant codes/standards
Air receiver	IS:226/IS:2002/IS:2062
Inter Cooler and After Cooler
Tube	S.S.
Shell	SA 285 Gr. C
Air drying plant
Retention mesh for Silica Gel and other components coming in contact with moisture.	SS

 

2.8.18.4            Drive Motor

 

                        Drive motor shall be connected to the air compressors directly or through any suitable type of power transmission system.

 

                        The continuous motor rating (at 50°C) shall be at least fifteen per cent (15%) above the maximum load demand of the compressor in the entire operating range to take care of the system frequency variation.  Total maximum load demand shall include air compression power plus any power consumed in auxiliaries like cooling fan etc.  When the driver is not directly coupled to the compressor, due account shall be made for losses in power transmission in addition to the above 10% extra margin.

 

2.8.18.5            Instruments

 

                        Each Compressor shall be provided with the following instruments as a minimum:

 

                        (i)         Pressure Gauges

 

                        a)         with each air receiver for air pressure                              :           1 No.

 

                        b)         after each stage (LP & HP) for air pressure                     :           1 No.

 

                        c)         at the lubricating oil inlet for oil pressure                          :           1 No.

 

                        d)         at the prefilter (air drying plant) inlet and

                                    outlet for air pressure                                                     :    1 No. each

 

                        e)         at the adsorber tower inlet & outlet for

                                    air pressure                                                                   :    1 No. each

 

                        f)          at the after-filter (air drying plant) 

                                    outlet for air pressure                                                     :           1 No.

 

                        g)         at the blower (air drying plant) outlet

                                    for air pressure                                                              :           1 No.

 

                        h)         with the air receivers on instrument

                                    air line near each unit for air pressure                              :           1 No.

 

                        j)          at the cooling water inlet to each

                                    compressor unit for C.W. pressure                                  :           1 No.

                        k)         at the instrument air ring header

                                    for air pressure                                                              :           1 No.

 

                        l)          at the inter-cooler outlet for C.W. pressure                       :           1 No.

 

                        m)        before air receiver for each compressor

                                    for C.W. pressure                                                          :           1 No.

 

                        n)         at the after-cooler inlet for C.W. pressure                        :           1 No.

 

 

                        (ii)        Temperature Gauges

 

                        a)         after each stage (LP & HP) for

                                    air temperature                                                              :    1 No. each

 

                        b)         at the C.W. outlet of each cylinder

                                    for C.W. temperature                                                     :           1 No.

 

                        c)         at the inlet of HP cylinder for

                                    C.W. temperature                                                          :           1 No.

 

                        d)         at the after-cooler outlet for

                                    C.W. temperature                                                          :           1 No.

 

                        e)         at the after-cooler outlet for air

                                    temperature                                                                   :           1 No.

 

                        f)          with each air receiver for air temperature                         :           1 No.

 

                        g)         at the adsorber tower inlet & outlet

                                    for air temperature                                                         :           1 No.

 

                        h)         at the outlet of heater for air drying

                                    plant for air temperature                                                 :           1 No.

 

                        i)          at the lubricating oil inlet for

                                    oil temperature                                                              :           1 No.

 

                        j)          at the cooling water inlet to each

                                    compressor unit for C.W. temperature                             :           1 No.

 

                        k)         at the lubricating oil in crank case

                                    for oil temperature                                                         :           1 No.

 

 

                        (iii)       Pressure Switches

 

                        a)         with each air receivers

 

                                    i)          for air pressure high                                           :           1 No.

 

                                    ii)         for air pressure low                                            :           1 No.

 

                                    iii)        for load/unload                                                  :   1No. each

 

                                    iv)        for start/stop                                                      :   1 No. each

 

                        b)         at the lubricating oil inlet for oil pressure low                    :           1 No.

 

                        c)         at the compressor discharge

 

                                    -           for air pressure high                                           :           1 No.

                                    -           for air pressure low                                            :           1 No.

 

                        d)         at the air drying after filter outlet for

                                    instrument air pressure low                                             :           1 No.   

 

                        e)         at the instrument air ring header

                                    for instrument air pressure low                                        :           1 No.

 

 

                        (iv)       Temperature Switches

 

                        a)         with the cylinder jacket for water

                                    temperature high                                                            :           1 No.

 

                        b)         before the after-cooler for air

                                    temperature high                                                            :           1 No.

 

                        c)         after the after-cooler for air

                                    temperature high                                                            :           1 No.

 

                        d)         after the inter-cooler for air

                                    temperature high                                                            :           1 No.

 

                        e)         with the reactivation air dryer for

                                    reactivation air temperature low.                                     :           1 No.

 

 

                        (v)        Flow Indicators

 

                        a)         at the cylinder C.W. outlet for C.W. flow                        :           1 No.

 

                        b)         at the after-cooler outlet for C.W. flow                            :           1 No.

 

                        c)         at the inter-cooler outlet for C.W. flow                            :           1 No.

 

                        d)         at the lubricating oil cooler outlet

                                    for C.W. flow                                                                :           1 No.

 

                        e)         at the cooling water supply line to

                                    Air Compressor for C.W. flow                                        :           1 No.

 

 

                        (vi)       Level Gauges

 

                        a)         at the inter-cooler moisture separator                               :           1 No.

 

                        b)         at the after-cooler moisture separator                               :           1 No.

 

                        c)         at each air receiver.                                                        :           1 No.

                       

                        (vii)      Vacuum gauge at the suction filter                                   :           1 No.

 

                        (viii)     Flow switch in the cooling water supply

                                    line to air compressor unit to trip the

                                    compressor in case of low flow of water.                         :           1 No.

 

                        (ix)       Indicating type flow switch in the

                                    instrument air line to air receiver for

                                    each unit to alarm high flow due to leakage.                     :           1 No.

 

                        (x)        Differential pressure gauge across oil filter.                       :           1 No.

 

                        The bidder shall include any other instrument required to make the system safe, efficient and reliable.

 

2.8.18.6                        Gear Boxes

 

Gear boxes containing helical gears, totally enclosed and lubricated shall be used for speed reduction between motor drives and driven Equipments. (i.e. Compressors, blowers, clinker grinders, combined ash slurry disposal pumps, scrapper conveyors, etc.)

 

Gear boxes shall be totally enclosed and oil lubricated type. Positive lubrication shall be provided to all the bearings and particularly to the working surface of the gear teeth.

 

                        The gear unit shall be specifically designed for continuous service at the speeds required by the application. Precision and accuracy of manufacture is essential to minimise problems of vibration, impact stresses, noise distortions and lubrication.

 

                        Dynamically balanced, helical gears shall be used.

 

            i)          Casing

 

a)         The gearing shall be enclosed in an oil and dust proof gear case made of closed grained cast iron or fabricated steel.

 

b)         The gear case shall be horizontally split and stress relieved before machining. The faces of adjoining sections shall be accurately machined to provide oil tight joints. Oil level gauges, drain, fill vent, thermometer, dipstick and other required connections equipped with approved mountings, valves and fittings shall be furnished for the gear casing.

 

c)         The housing shall be generously proportioned and of rigid construction to provide permanent alignment of rotating parts and protection from possible external vibration. The arrangement shall be such that it will be possible to lift gear case cover without disturbing the alignment of shaft, gear and pinion.

 

                        The gear box shall be provided with suitable bearings of conservative design to meet the worst duties under transients.

 

            ii)         Rating of Gear Box

 

a)         Gear box shall be designed for heavy shock loads and while selecting a gear box a service factor of minimum 2.0 shall be considered.

 

b)         The nominal mechanical KW rating of each gear box shall not be less than the name plate KW rating of the selected drive motor.

 

c)         Thermal rating of each speed reduction gear box at 500C ambient temperature shall not be less than the name plate KW rating of the selected drive motor.

 

d)         For cooling of gear box, in case thermal capacity without auxiliary fan is not sufficient to meet the thermal rating of gear box, necessary auxiliary cooling fan shall be provided. Cooling coil for this purpose is not acceptable.

 

e)         The selection of gear box shall be subject to Owner’s approval. The Bidder shall furnish necessary calculations and selection charts for this purpose for Owner’s review and approval.

 

2.8.19               Wetting Head

                        Adequately sized wetting head shall be provided above collector tank for wetting the dry fly ash and separating it from convey­ing air, if any.

 

                        The wetting head shall be provided with a water supply of sufficient quantity and pressure for feeding the nozzles that will produce fog spray of water, ensuring rapid wetting of the incoming ash.

 

                        Nozzles shall be so directed as to prevent spray from entering the ash discharge pipe.

 

                        The bidder shall elaborate as to have water vapour generated by the rise in water temperature shall be prevented from rising from the wetting head into the discharge chute to avoid the possibility of dry ash discharge pipe chute blockage.

 

                        Wetting head shall be compact in design and provisions shall be made for easy replacement of nozzles.  Flanged connections shall be provided for all inlet and outlet connections of the wetting head.

 

Material of construction shall be as follows:

 

(a) Body	Close grained 2% Nickel cast iron minimum hardness 250 BHN.
(b) Nozzle	Body of MS/Cast Iron and replaceable tip of Anti corrosion tool steel or stainless steel of hard­ness 500-550 BHN. OR Ceramic material.

 

2.8.20               Collector Tanks

 

                        The collector tank shall be located below the wetting tank and serve the purpose to separate and vent out air  and  discharg­ing the ash slurry to the combined ash disposal sump through pipe lines.  This will also serve the purpose of separating and venting out the entrapped air discharged by wetting head and before discharging the entrapped air into atmos­phere, it shall be passed through an air washer to achieve a sustained outlet dust emission of 50 Mg/Nm³ (Max.) with the ash handling system operating at de­signed capacity.  The dust emission figure shall be guaranteed.

 

                          The collector tank shall be located at an elevation which will provide sufficient static head to overcome frictional and other losses in the gravity flow dis­charge line upto ash slurry sump.

 

                        For maintenance purposes suitable stair case, mainte­nance platform, walkway with handrails at necessary levels shall be provided.

 

                        The sizing of collector tank, inlet/outlet connections etc. shall be corresponding to the maximum anticipated discharge flow requirements.  The collector tank shall be complete with drain, overflow and vent pipe connec­tions alongwith pipes and requisite size and lengths.

 

                        The tank shall be internally lined with alloy C.I. liners of thickness not less than 20 mm.

 

The material of construction shall be as follows:

                       

Tank	Tested quality, M.S. of mini­mum 10 mm thickness, as per IS:2062.
Baffle	Tested quality M.S., of mini­mum 12 mm thickness, as per IS:2062.
Liners	Alloy C.I. (300-350 BHN), 20 mm, thick minimum.

 

 

2.8.21 Bag Filters

2.8.21               Bag Filters

 

                        The bag filter unit shall be placed above all the buffer/ interme­diate hoppers, and the main ash storage silos. In case of storage silos and buffer/ intermediate hoppers for pressure conveying system, the bidder should provide exhaust fans to assist venting.

 

                        Because of the stringent duty conditions, it should be possible to carry out the maintenance and replacement of the bags without affecting the performance of the system.

 

                        The Bidder shall justify in his bid, the air to cloth ratio selected, the bag material, the ability to with­stand the vacuum, pressure and temperature, the mainte­nance and replacement procedures of the damaged bags.

 

                        The performance of the bag filter shall not get affect­ed with 10% of the bags plugged.  This condition shall be demonstrated by the Contractor at site under actual working conditions.

 

                        The bag filter unit shall be designed to achieve as sustained outlet dust emission of 50 mg/NM³ (maximum).  The dust emission figure shall be guaranteed.

 

                        All bag filters and fans shall be installed under cover, and be protected from all potential adverse weather conditions.

 

                        All bag filters shall be supplied complete with auto­matic bag filter cleaning equipment, details of which shall be included in bid.

 

2.8.22 Dry Fly Ash Storage Silos

2.8.22               Dry Fly Ash Storage Silos

 

                        2 Nos. storage silos each to store 1000m3 of dry fly ash with adequate margins shall be provided. Storage silos shall be of flat/conical bottom type with the provision of air slides/fluidising pads at the bottom. Storage silos shall be provided to store precipitator fly ash with adequate air space.  This silo shall be used to collect dry fly ash for the purpose of sale. It shall have facilities for dry ash unloading into cov­ered road tankers and conditioned fly ash in open road tankers. The silos shall be R.C.C. constructed.

    

                        Each dry fly ash storage silo shall be provided with following arrangement for unloading the fly ash.

 

                        (a)        A retractable chute alongwith rotary feeder for unload­ing  the dry fly ash into closed road tankers at a rate of 120 T/hr. max.

 

                        (b)        A ash dust conditioner alongwith feeder for load­ing the conditioned ash into open road tankers at a rate of 40-120 T/hr.  The water content in the conditioned ash shall vary between 0 – 15 %

 

                        (c)        Two blanked connections along with isolation valves shall also be provided in the silo for future installa­tion of pneumatic equipment for transportation of a dry ash to third party and for installation of equipment to slurrify the dry ash to dispose off it through ash disposal system.

 

                        The storage silo shall be designed to provide a clear access of 5.5m for a road tanker to come under the silo and receive the ash from the retractable chutes. To facilitate locating these chutes over the road tanker opening, it shall be possible to move the chute in all directions in the horizontal plane. It may be noted that unloading system from Silo shall be suitable for both rail wagon unloading and closed tanker/open truck unloading.

 

                        Each retractable chute shall include a shut off device at the chute outlet, a level probe to determine the level of ash within the road tanker, dedusting and vent air systems, and a motor operated winch system to lower/raise the chute.

 

                        Each storage silo shall be provided with a separate and dedicated floor aeration system.  This aeration should only be required during silo unloading and should not be in operation during storage periods.

 

                        The silo aeration system shall be supplied by con­stant volume blowers. Any manifolds employed for air distribution in the aeration system shall be fitted with blank flanges at the mani­fold ends, to facilitate maintenance requirements.

 

                        A suitable dust suppression system at various levels of the silo shall be provided, if required.

 

                        The pressure/vacuum relief valves in the storage silos shall be provided.

 

                        Bag filters shall be provided on the storage silos for cleaning the aeration and displaced air before venting out.  The Bidders should provide exhaust fans to assist venting. Bag filters and fans shall be installed under cover, and the protected from all potential adverse weather conditions.

 

                        The dust loading from the outlet of the bag filters shall not exceed 50 mg/Nm³ under any operating condi­tion with 10 per cent bags plugged.  Bidders shall justify the selected air to cloth ratio of the bag filters.  The Bidders shall also supply details on how the air flow into and out of, the storage silos is balanced during different operating conditions. 

 

                        The provision of a proven dust collection system in the storage silos that separate out bulk of the ash from the conveying air shall be provided before the air is extracted through the bag filters.

 

2.8.22.1            Instruments

 

                        Each silo shall be provided with following instruments as a minimum :

 

                        a)         Silo ash level switches (High and Low)                            :           1 No.

 

                        b)         Level switch with the telescopic chutes

                                    (meant for unloading into closed tankers)                         :           1 No.

 

                        c)         Differential pressure gauge across the bag filter                 :           1 No.

 

                        d)         Differential pressure switch across the bag filter                :           1 No.

 

                        e)         Pressure gauge at the inlet of the bag filter                       :           1 No.

 

                        f)          Differential pressure gauge across the vent filter               :           1 No.

 

                        g)         Differential pressure switch across the vent filter              :           1 No.

 

                        h)         Pressure gauge at the inlet of the vent filter.                     :           1 No.

 

                        The bidder shall include any other instrument required to make the system safe, efficient and reliable.

 

2.8.23 Water and Air Piping, Fitting and Accessories

2.8.23               Water and Air Piping, Fitting and Accessories:

 

                        All required water and air pipework including all instrument impulse piping and fitting for complete DAETP shall be provided as specified.

 

                        All piping system shall be capable of withstanding the maximum pressure (pump shut off) in the corresponding line at the relevant temperatures.

 

                        All piping system shall be properly designed to take care of water hammer/pressure surges which may arise during operation of the system. 

 

                        All piping shall be provided with vents at the highest points and drains at the lowest points alongwith vent valves and drain cocks. Vents shall not be less than 15mm in size. Drains shall not be less than 25 mm size.

 

                        Bends, loops, off sets, expansion or flexible joints shall be used as required in order to prevent over­stressing of the piping system due to thermal movements and to provide adequate flexibility.

 

                        The design, supply and installation of all pipe sup­ports and hangers including pipe clamps, turn buckles, hanger rods, auxiliary steel etc. shall be furnished.  All bolting materials companion flanges, nuts gaskets etc. as required in the piping system and at all terminal points shall be furnished.

 

                        All piping shall be routed so as to avoid interference with other pipes and their hangers and supports, elec­trical cable trays, ventilation ducting structural members, equipment etc.  Adequate clearance shall be ensured with respect to the above to accommodate pipe movement.

 

                        The piping shall be arranged to provide clearance for the removal of equipment requiring maintenance and for easy access to valves and other piping accessories required for operation and maintenance.

 

                        Piping shall generally be routed above ground but where specifically indicated/approved by the Engineer the pipes may be arranged in trenches or buried.  Bidder shall provide either coal tar and Bitumen tapes on conventional coat and wrap system for corrosion protec­tion of buried piping as per relevant codes and stand­ards.

 

                        Overhead piping shall have a normal minimum vertical clearance of 3 metres above walk ways and working areas and 6 metres above roadways.

 

The following line velocities shall be considered for estimating the line sizes of water pipes and Air Pipes:

 

 

                        ————————————————————————————————–

                        Service                             Velocity, M/Sec

                        ————————————————————————————————–

                                                                    Pipe size              Pipe size                Pipe size

                                                                    size below           of 50 to                  of 200 mm

                                                                    50 mm                150 mm                 and above

                        ————————————————————————————————–

                        a)   Water pump                    06-0.9                 1.2-1.5                   1.2-1.5

                              Suction

 

                        b)   Water Pump                    0.9-1.8                1.5-2.4                   1.8-2.8

                              Discharge

 

                        c)   Compressed                    15-20                  15-20                     20-30

                              air below

                              2 Kg/cm²(g)

 

                        d)   Compressed                    20-30                  20-25                     25-35

                              air, 2 Kg/cm² (g)

                              & above

                        ————————————————————————————————–

                        Note

 

                        1.         Pipe Size in pump suction side shall be at least one pipe size larger than the corresponding pump discharge connec­tion.

 

                        2.         The proposed sizes of the water and air pipes shall be submitted.

 

                        The pipe supports shall be spaced as follows.

 

                        Pipe size(NB)    25        50        100       150       200       300       400       500

                        Spacing in         2.1       3.0       4.3       5.2       5.8       7.8       8.2       9.8

                        metre   

                       

2.8.23.1                                         Water and Air Piping,

Fittings and Accessories

1.0	Type of Pipes	a) Upto & including150 NB		MS, ERW pipes to IS:1239 Heavy grade
		b) 200 NB to 450 NB		MS ERW to IS 3589.
				OR
		SAIL or equal make		ERW commercial quality pipes.
		c) 500 NB and above		Rolled and welded from MS plate to IS:226 Dimensional toler­ance as per IS:3589.
				OR
				SAIL OR Equal make
				spiral welded pipes.
				Dimensional toler­ance as per IS:3589.
2.0	Pipe SIzes	As required.
3.0	Thickness of Pipes	a) Pipe specs. as per IS:1239		Pipe thickness shall be of Heavy grade.
		b) Pipe spec. as per IS:3589(ERW)		Min 6.35mm thick for 200 NB to 400 NB size and Min. 7.14 mm thick for 450 NB size.
4.0	Type of Line joints.
		a) 50 NB and below		Socket welded to ANSI:B16.11.
		b) 65 NB and above.		Butt welded to ANSI:B16.25.
5.0	Quantity	As required
6.0	Fittings (Bends)
		a) For sizes upto& including65NB		3D radius bends and material same as that of parent pipe.
		b) For sizes 80 NB to 300 NB		SR & LR elbow and material same as that of parent pipe
		c) 350 NB & above.		Miter bends with Miter angle not exceeding 22.5°.  Material shall be same as that of parent pipe and dimensional toler­ance shall be as per BS : 534.
7.0	Flanges	Slip on flat face type with drilled and pressure rating as per valve and other specialities. Material of construction shall be IS:226 upto 20 MM thickness and IS:2062 for higher thickness.
8.0	Bolts	As per IS:1367 Cl.4.6 or ASTM-A-307-Gr.B.
9.0	Nuts	As per IS:1367 Cl.4.0 or ASTM A-307 Gr. B.
10.	Gaskets	Wire inserted Red rubber.  Thickness shall be 1.6 mm for sizes upto and including 250 NB and 3.2 mm for higher sizes.
II.  Air Pipes
1.0	Type of Pipe		a) ERW pipe as per IS:1239, heavy grade with galvanising as per IS:4736 for pipes  upto & including 150 NB. For pipes of sizes above 150 NB it shall be as per Cl. I (1.0, b) & Cl. No. I (3 b) above.
			b) For compressed air piping for instru­ment and control loops, bulk heads, the following standard shall be adopted
			i)                 For sizes25 NB and including 50 NB. ii)                For sizes below 25 NB	Seamless Red Brass ASTM B43 Sch.40.         Seamless Copper to ASTM  -75
2.0	Pipe Sizes		As required
3.0	Thickness of pipes		For pipe size upto & including 150 NB pipe thickness shall be of heavy grade as per IS:1239 and for pipes of higher sizes, the thickness shall be as per clause No. I (3.0) b & c on page-5 mentioned above for water pipes.
4.0	Type of Line joints		(a) 65 NB and below	Screwed
			(b) 80 NB and above	Sleeve welded . However valve etc. shall be IS:226 upto 20 mm thickness and is:2062 for higher thickness.
5.0	Quantity		As required.
6.0	Fittings/ (Elbows)		As per ASTM-A-234 Gr. WPB (GI)
7.0	Flanges		Raised face type G.I. screwed and pressure rating as per valve and other specialities.   Material of construction shall be IS:226 upto 20 mm thickness and IS:2062 for higher thickness.
8.0	Bolts, nuts & Gaskets.		Same as for water pipes

 

2.8.24 Water and Air Line Valves and Special

2.8.24               Water and Air Line Valves and Specialities

 

                        All valve shall be suitable for the service conditions i.e. Flow, temperature and pressure under which these are required to operate and those performing similar duties shall be interchangeable, with one another unless otherwise approved. All valves and connections shall be suitably protected to prevent damage and entry of dirt, till erected.

 

                        End to End dimensions shall be in accordance to ANSIB16.10 or as per codes to which they conform to.

 

                        All manually operated valves of all sizes 350 NB and above shall be provided with gear operator of proven quality, reputed make and conforming to internationally accepted standard.

 

                        All valves shall be fitted with open/close position indicators.

 

                        All valves shall be provided with hand wheels, extension spindles and floor stands or any other arrangement wherever required so that these can be operated manually with ease by a single operator from the nearest operat­ing floor either at a lower or higher elevation as the case may be. Wherever necessary for safety purpose, locking devices shall be furnished with valves.

 

                        All Gate and Globe valves shall be of outside screw and yoke (OS&Y) type and provided with back seat to permit repacking with valves in operation.

 

                        The actuator operated valves shall be designed on the basis of the following:

    

                        a)         The internal parts shall be suitable to support the stresses caused by the actuator.

    

                        b)         The valve actuator unit shall be suitably stiff so as not to cause vibrations, misalignment etc.

 

                        c)         Motorised Valves shall be provided with hand operating gear, hand wheel and clutching and declutching arrange­ment.

 

                        The size of all valves shall be the same as that of parent pipe.

 

                        The end connections shall comply with the following:

 

                        -           Socket welding (SW)                 -           ANSI B16.11

                        -           Butt welding (BW)                     -           ANSI B16.25.

                        -           Threaded (SC)                          -           ANSI B2.1

                        -           Flanged (FL)                             -           ANSI B16.5.

 

                        Gate valves shall be used for isolation purposes, Globe valves shall be used for regulation purpose, check valves shall be used for non-return service, and plug valves shall be used for isolation purpose in those lines where quick opening and closing is required in the system.

 

                        Double flanged or wafer type butterfly valves of low leakage rate conforming to AWWA-C-504, BS:5155 or any other approval equivalent latest standard edition can also be used for isolation, quick isolation and regula­tion purposes.

 

                        Material of construction shall be as follows:

 

For sizes below 50 mm and working pressure or shut off pressure (whichever is  higher) is upto 15 Kg/cm2(g)/ (upto 10 Kg/cm2(g) for Plug valves)
	Body/Wedge/Disc		Gun Metal
	Trim & Stem		Gun Metal
For sizes 50 mm and above and working pressure or shut off pressure (whichever is higher) upto 15 Kg/cm2(g).
	Body/Wedge/Disc		C.I. to IS 210 Gr. FG 220
	Trim & Stem		Brass/ Gun Metal
For all sizes and working pressure or shut off pressure (which ever is higher) is   above 15 Kg/cm2(g) (Above 10Kg/cm2 for plug valves).
	Body/Wedge/Disc		Cast/Forged carbon steel
	Wedge/Disc/Plug		Cast carbon steel with 13% Cr
	Trim and Stem		Stainless steel

 

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

2.8.26 Ash Slurry Sump Isolation Plug Valves, Sump Liners and Agitating Nozzles

2.8.26               Ash Slurry Sump Isolation Plug Valves, Sump Liners and Agitating Nozzles

 

                        The ash slurry sump shall have two(2) isolated compartments in combined ash disposal pump house. Each compartment shall serve two (2) nos. streams of combined ash disposal pumps.  The bottom ash and fly ash slurries shall be led to a common distribu­tion trough at the top of the slurry sumps which will have manually operated plug valves enabling the slurry to flow to the desired compartments (corresponding to the pump steams in operation).

 

                        It shall be possible to operate slurry sump isolation valves from top of sump level. The valve shall be provided with gear operator if effort required to operate the valve exceeds 25 kgf.

 

                        Material of construction for slurry sump isolation valves shall be corrosion and abrasion resistant and shall be of quality most suited to proposed application. Suitable measures to protect the bearings from ash ingress shall be provided.

 

                        Valves shall be suitable for outdoor duty.

 

                        All the slurry distribution troughs and sump compartments shall be provided with abrasion liners in the areas of slurry impingment.

 

                        A layout drawing including cross section of slurry trenches shall be submitted. The Bidder shall furnish the section and dimensions of the trench liners as per the slopes indicated elsewhere in this specification to convey the slurry by gravity to the slurry sump. A free board of min. 100 mm shall be provided for the trench liners.

 

                        Cast iron lining (IS:210, FG 260) for the inner walls of the slurry trench/sump shall be provided by Contractor. The lining should be minimum 20 mm thick, on side walls and 30 mm thick at bottom”.

 

                        Bidder shall provide adequate number of high velocity water jetting/agitating nozzles in the slurry trenches/sumps to avoid setting of ash particles at the bottom of the trenches/sumps. The material of jetting/agitating nozzles shall be anti corrosion tool steel of hardness 500-550 BNH.

 

2.8.27 Horizontal Centrifugal Pumps

2.8.27               Horizontal Centrifugal Pumps

 

                        The ash slurry pumps for combined B.A. and F.A. disposal, B.A. Cooling water over flow pumps, BAHP pumps, BALP pumps, flushing water pumps seal water pumps, for ash slurry pumps, dust suppression, ash conditioning and seal water pumps in main storage silo area and cooling water pumps for cooling various equipments of ash handling plant shall essentially be horizontal and centrifugal type.

 

                        The equipment shall be capable of developing the required head at rated capacity for continuous operation.

 

                        All centrifugal pumps shall have a drooping characteristics curve, with the head continuously increasing with decreasing flow to maximum head at zero flow and the pumps shall preferably be non-overloading type beyond rated duty point.

 

                        The characteristics curves of each set of pumps shall match each other for equal load sharing in case of parallel operation and such pumps shall be identical and all parts shall be fully interchangeable.

 

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

 

                        Specific Design Requirements for Slurry Pumps

 

                        The ash slurry sump geometry and configuration shall be such as to minimise ash settlement, formation of vortices and air entrainment in the slurry as this may affect the operation of the slurry disposal pumps.  To minimise the ash settlement adequate number of high velocity water jetting nozzles shall be provided in the slurry sumps.

 

                        The rating of the ash disposal pumps shall be based on the stipulations con­tained herein as given under:

 

                        A)        F.A. and B.A. Handling

 

                                    The maximum velocities in slurry transformation lines for both F.A. and B.A. shall be limited to 2.8 m/sec.

 

                                    The maximum concentration of B.A. and F.A. slurries when being

                                    handled independently or combined shall be as under:-

 

                                    i)          B.A.                                         -           25% (W/W)

 

                                    ii)         F.A.                                          -           30% (W/W)

 

                                    iii)        Combined B.A. & F.A.              -           25% (W/W)

 

                        B)        Combined Ash Slurry Disposal System

 

                                    The combined ash slurry disposal system shall meet the following mandatory requirements :

 

a)                Not more than (2) pump streams shall be employed for handling the total bottom and fly ash slurry generated from the two units when the bottom ash is extracted either intermittently and fly ash is extracted at the specified  removal rates.

 

                                    b)         Minimum make up water should be required at the slurry sump during the operating condition when only one unit is operating or during the periods in a shift of 8 hours when fly ash slurry is being received continuously and the bottom ash slurry is being received intermittently since these operating modes are also considered as normal operating modes.

 

                                    c)         The concentration of the ash (combined bottom and fly ash in the sump) in the slurry handled by the ash slurry disposal pumps shall not exceed 25% (W/W) and the flow velocity in the ash slurry disposal pipeline shall not exceed 2.8 m/sec. during any operational mode of the system.  The bottom ash and fly ash slurry concentration under any mode of operation shall be decided considering the rated capacity of respective extraction systems.

 

                                    d)         The ash slurry disposal system should also be designed to cater to the operating conditions as when only the F.A. handling system for both the units is working (i.e. when B.A. and economizer ash evacuation is over), the slurry concentrations under such condition shall not exceed 30% (W/W) and the flow velocity in ash disposal pipe line shall not exceed 2.8 m/sec.

 

                                                            The fly ash slurry concentrations under this mode of operation, shall be decided, considering the rated capacity of the extraction system.

 

To maintain the concentration limit and to run the ash slurry disposal pumps effi­ciently a provision shall be made for make-up water pipe connections complete with motor operated gate valves and manual gate valves.

 

                        Minimum 10% margin shall be considered for ash slurry pump sizing over and above the total slurry disposal head requirement comprising the straight pipe line frictional loss and bends loss.  The value of the constant ‘C’ in William-Hazen equation, shall be considered as 140 for calculating the system head.

 

                        An additional flow of 100 m³/hr (continuous) shall be considered on ash slurry pump capacity to take into account sludge disposal from clarifier units to be pumped by ash slurry disposal pumps to the disposal area.  Bidder may take advantage of this additional quantity of sludge (the density of solids in sludge may be taken as 1.1 and the concentration as 5%) while arriving at ash slurry concentration for the combined ash disposal pumps.  Apart from the working streams one standby and one maintenance standby shall be provided for the ash slurry disposal system.

 

                        The slurry pumps shall essentially be slow rpm pumps. The rotational speed of the impeller at design point shall not exceed 1000 rpm.

 

                        The first stage of slurry disposal and transportation pumps shall be provided with variable speed hydraulic coupling of robust design for setting the optimum operating speed of the pumps based on actual site requirements after the system is installed.  Minimum (+) 10% and (-) 45% speed variation with respect to speed at rated  design point shall be provided in the first stage of combined ash slurry disposal pumps and ± 20% for bottom ash transportation and BA overflow water pumps. The slurry pump motor speed shall not exceed 1500 rpm.

 

                        To minimise the drive losses in the first stage of slurry disposal and transportation pumps, a constant speed reduction gear box shall be provided.  The gear boxes to be employed shall be suitable for heavy duty application and of such reputed make which have proven established record of trouble free service under heavy load transmission duties.

 

                        For the subsequent slurry disposal and transportation pump stages, the drive shall be transmitted through belt drive arrangement.  If in future, the operating speed of these pumps is also required to be changed, the Owner intends to carry out this change by replac­ing the existing belt-pulley with a pulley of different diameter to allow a future variation of ± 10%.  Pump and motor layouts in the pump house shall be accordingly decided to take care of this requirement.

 

                        Continuous motor rating (name plate rating) at 50°C for ash slurry pumps shall have atleast 20% margin above the maximum load demand of the driven equipment at the rated duty point. The maximum load demand shall be calculated considering slurry density, efficiency of pump when handling slurry and the complete drive losses in the transmission (fluid coupling, gear box, etc.). For selecting the motor, the maximum pump efficiency to be considered shall be 70%. To ensure interchangeability, all the pumps & motors of the pumping streams shall be of similar rating and the pumps shall be designed for + 10% and – 45% speed variation.

 

                        Pumps shall be single stage, end suction design provided with heavy duty impellers suitable for highly abrasive duty application.

 

                        All the wear parts of pumps, impellers and liners etc. shall have a minimum guaranteed life of 8000 hrs. of operation.

 

                        Provision shall be made for adjustment to take up wear by axial movement of the shaft.

 

                        The seals shall be water flushed packed glands, fed from an external clean water supply source.

 

                        The impeller tip speed at the rated parameters shall not be more than 1676 metres/min.  Bidders shall make selection of the pump size such as to limit the tip speeds to above specified limits.

 

                        The passages and clearances in pump components shall be properly designed, considering the size of ash and clinker to be handled.

 

                        The pumps shall have flooded suction inlet and shall be located indoors.  Howev­er, pumps shall be suitable for operating with upto 2 metres suction lift.

 

                        The glands of the pumps should be suitably designed to prevent clogging of ash particles.

 

2.8.27.1            Specific Requirements for Seal Water and other Horizontal Water Pumps

 

                        (a)        Seal water system, taking suction from water supply terminal points, shall be provided to supply gland sealing water for ash slurry disposal pumps, bottom ash slurry transportation pumps, BA overflow water pump, sludge pump, sump drainage pumps, clinker grinders, submerged scraper conveyors and cooling water for air compressors, blowers, vacuum pumps, fluid couplings, etc. Any other cooling/seal water requirement for the plant shall also be included in this seal water system.

 

                        (b)        To meet the gland sealing requirement in combined ash disposal pump house and bottom ash transportation pump house (if applicable). The pumps will take suction from  clarified water storage.  Separate pump sets shall be provided for meeting the sealing water requirements in each of the above mentioned buildings and 100% standby pumps shall be provided for each of these duties.

 

                                    For sealing requirement of clinker grinders, SSC’s (if applicable) in the boiler area and sump drainage pumps in bottom ash transportation pump house the water shall be tapped from the  clarified water storage.

 

                                    All the necessary piping and valving shall be in the scope of supply.

 

                        (c)        Additionally One (1) no. tank shall be provided in the ash storage silo area for meeting the water requirements of ash conditioning, dust suppression, cooling water for silo aeration blowers (if any) and seal water for sump drainage pumps.  Necessary pumps (as specified and as required) shall be provided to meet these requirements which will take suction from this tank.  Bidder may combine the requirements of dust suppression, cooling water for blowers and seal water for sump drainage pumps (depending upon the pressure/flow requirements) in which case the cooling water requirement for silo aeration blowers (if any) and water requirement for dust suppression shall be considered as simultaneous requirement.  The pumps shall be suitably designed to take care of the varied water requirements.

 

                        (d)        The design of the seal water system for supplying water to gland sealing to various ash slurry pumps shall be such as to have the gland sealing water system for maximum of two (2) stages of the working streams supplied from one seal water pump and shall have its own 100% standby pump.  For the balance stage (stages) of the working streams separate seal water pump shall be provided with its own 100% standby facility.  The seal water pump shall be sized for meeting the seal water requirements of pumps in working streams and one (1) no. additional stream which will be in flushing mode.

 

                        At least 15% margin shall be provided in the pump capacity over and above the maximum seal water/cooling water and other flow requirements. For calculating the system head, the value of constant ‘C’ in William Hazen equation shall be considered as 100.

 

                        Continuous motor rating (name palte rating) at 50°C for seal/cooling water pumps and other horizontal water pumps shall have at least 15% margin above the maximum load demand of the driven equip­ment in the complete operating range to take care of the system frequency varia­tion.

 

                        Seal water/cooling water and other horizontal water pumps shall be direct driven with speed not exceeding 1500 rpm.

 

2.8.27.2            Construction Features

 

            ●          Casing

 

                        i)          The casing shall be structurally sound to provide housing for the pump assembly and shall be designed hydraulically to minimise radial loads at part load operations.         

 

                        ii)         With the exception of the slurry pumps, pump casings shall preferably be horizontal split type, with the top casing and internals being removable without disturbing the main pipework connections.  In general all pumps shall be designed such that the rotating assembly can be withdrawn without removing the motor. The casing shall be finished to smooth surfaces as far as possible.  Casing drain and vent connection with plugs and valves shall be provided where required. Casing shall withstand without expansion joints, the usual moment and thrusts.

 

                        iii)        In case of ash slurry pumps, these shall be of either twin casing construc­tion or single casing with metal lining construction or single volute casing construction. The pressure casing (or outer casing) shall be generally in accordance with the stipulation of API-610. The thickness of inner casing in case of single casing with metal lining pumps and the wear margin in case of single volute casing pumps shall not be less than 35 mm.

 

            ●          Impeller

 

                        i)          The complete rotor assembly shall be statically and dynamically balanced and designed with critical speed substantially abvoe the operating speed.

 

                        ii)         Impellers shall be made in one piece and securely fixed to the shaft.  Means shall be provided to prevent loosening during operation including rotation in reverse direction.

 

                        iii)        Impeller fastening nuts (if provided)shall be of cap type and shall tighten in direction of normal rotation.

 

                        iv)        For ash slurry pumps, the minimum impeller thickness shall not be less than 30 mm and shroud cover thickness shall not be less than 35 mm.

 

            ●          Impeller/Casing Wearing Rings (Where applicable)

 

                        Replaceable type wearing rings shall be provided at suitable locations for each pump. The rings shall be so fitted as to prevent turning while the pump is in opera­tion.

 

            ●          Shaft

 

                        i)          The shaft shall be finished to close tolerance at the impeller, coupling, pulley and bearing diameters. The impeller, pulley and shaft sleeves shall be firmly secured to the shaft by key and/or nuts.  Slurry pump impellers may be screwed on the shaft (threads to tighten during normal pump rota­tion).         

 

                        ii)         The shaft shall be adequately sized to withstand all stresses from rotor weight and hydraulic loads etc. and ground and polished to final dimen­sions.

 

                        iii)        The design of the shaft shall also take into consdieration the critical speed of the shaft which shall be at least 20 percent above the maximum operating speed or about 60 to 75 percent of the lowest operating speed.

 

            ●          Shaft Sleeve

 

                        Pumps shafts shall be protected by renewable type shaft sleeves which shall extend well beyond the pump glands. The sleeves shall be highly  polished and shall be securely fastened to the shaft to prevent any loosening.

 

            ●          Bearings

 

                        i)          Heavy duty ball, roller (tapper roller wherever required)or sleeve bearings, adequately designed for the type of service specified and for long and trouble free operation, shall be furnished. Sleeve type bearing shall not be supplied for slurry handling liquids.

 

                        ii)         The design of oil lubricated bearings shall be such that the bearing lubricat­ing oil does not contaminate the liquid being pumped.

 

                        iii)        Grease lubricated ball bearings are acceptable, if the pumps is specifically designed for grease lubrication and if shaft speed is less than the speed limit recommended by the bearing manufacturer and the fluid temperature does not exceed 65.5 deg.C (150 deg.F).

 

                        iv)        Each bearing housing shall have drain plug.

 

            ●          Thrust Bearings

 

                        Adequately designed thrust bearings to absorb pump end thrust or other unbal­anced forces, if any, shall be provided wherever required. Suitable arrangement for adjusting clearances shall be provided.

 

            ●          Stuffing Boxes & Sealing

 

                        i)          Stuffing boxes of packed ring construction or of mechanical seal type as applicable shall be provided. Packed ring stuffing boxes shall be properly lubricated and sealed as per service requirement and manufacturer’s stand­ard.

 

                                    If lantern rings are provided between the packages, these shall be complete with inlet and outlet piping connections.  Lantern rings shall be axially split type.

 

                        ii)         For pumps handling clear cool water if external gland sealing is required, it shall be done from the pump discharge or from any intermediate stage.

 

                        iii)        For pumps handling sandy/muddy water or slurry, external clear water sealing shall be provided. The design should also provide for flushing of the clearance between pump rotation and stationary parts continuously by trickle clear water flow.

 

                        iv)        The Bidder shall provide the necessary piping, valves, boosters, fittings, etc. for the gland sealing connection.

 

                        v)         For mechanical seals, the mating surfaces shall be suitably hard faced to ensure long life.

 

            ●          Couplings

 

                        i)          The pump & motor shaft shall be connected with a suitably designed flexi­ble coupling of approved design preferably with a spacer to facilitate dismantling of the pump without disturbing the motor.  Necessary expand­ed metal coupling guards for the coupling shall also be furnished.

 

i)                 Other arrangements for coupling the pump with prime mover may be employed only in case the same is categorically specified.

 

ii)                For pumps handling abrasive slurry or where fast wearing of pumps is likely due to the particular service conditions, variable speed drive shall be employed, thus enabling operation of pumps within specified ranges of speed with respect to pump speed at rated operating point. Pumps shall be suitable for operation at such higher speeds. The variable speed drive shall be the variable speed hydraulic coupling as specified.

 

            ●          Base Plates

 

                        i)          The base plates shall be of fabricated steel and of rigid construction, proper­ly ribbed as required.  Driplip with drain tap based on type of service speci­fied shall be furnished.

 

                        ii)         All directly coupled pump motor sets shall be supplied with common base plates.

 

                        iii)        For pumps coupled with motor through the variable speed drive transmission system, separate base plates for pumps and motors are acceptable.

 

                        iv)        The common base plate together with all foundation bolts and nuts shall be supplied by the Contractor.

 

            ●          Connections/Nozzles

 

                        Cast iron flanges shall be flat faced. Flanges shall be full or spot faced on the back side also.

 

                        All accessories required for proper and safe operation of the complete pump motor set shall be furnished.

 

                        Each pump shall be provided with drain, vent and a priming connection at suitable location, wherever applicable.

 

                        Pumps are required to operate for some period with discharge valve closed. The pumps shall be suitable for zero-flow operation for a reasonable period.

 

            ●          Accessories

 

                        The following accessories shall be supplied for all pump motor sets:

 

                        i)          Foundation bolts and nuts for pumps.

 

                        ii)         Foundation bolts and nuts for motors.

 

                        iii)        Foundation bolts and nuts for base plates.

 

                        iv)        Foundation bolts and nuts for slide rails, if slide rails are provided.

 

                        v)         Base plate for all pump-amotor sets.

 

                        vi)        Transmission guard for flexible coupling/vee belt transmission etc. as ap­plicable.

 

                        vii)       Slide rails for motors if variable pitch, set of vee belts or flexible coupling as applicable.

 

                        viii)       Suitable connection for sealing/cooling/flushing water supply, if applicable.

 

                        ix)        Lubrication fittings as necessary for proper and easy lubrication of the equipment.

 

                        x)         Drain and vent cocks as required.

 

                        xi)        Priming funnel or overhead tank, as required.

 

                        xii)        Foundation bolts for hydraulic coupling.

 

                        xiii)       Suitable adopter for pumps suction and discharge, if required.

 

                        xiv)       Anchor Bolts, Sleeves, Inserts, Lifting Lugs, Eye Bolts etc.

 

                                    The Bidder shall supply all anchor bolts, foundation plates, sleeves, nuts inserts etc. to be embedded in concrete for the equipment to be supplied.  The length of foundation bolts shall be liberally sized to reach below the reinforcement level.

 

                        xv)       Any other accessories mentioned elsewhere in this specification.