December 9, 2009
November 17, 2009
The work shall consist of mechanical and electrical work and equipment, all associated structural civil and architectural works, Control and Instrumentation equipment, mechanical services and pipe work and electrical services associated with this ash handling plant, the principal features of this plant being:
(a) a wet ash extraction and conveying system for ash collected in the boiler furnaces, economiser and air preheater ash hoppers including treatment system of Bottom ash hopper overflow water.
(b) a dry extraction and conveyance system for the ash collected in electrostatic precipitators collection hoppers and duct hoppers.
(c) a dry fly transportation and storage system which includes dry ash storage silos.
(d) combined fly ash and bottom ash slurry disposal system.
(e) ash water supply system.
Notwithstanding the scope mentioned for various sub-systems in the following paragraphs, it is the responsibility of the contractor to carry out complete job on turnkey basis and integrate the sub systems with each other.
22.214.171.124 Bottom Ash Handling System
Scope under this specification for bottom ash handling system starts from the boiler furnace bottom to the disposal of ash slurry in the sump of combined ash slurry pump house, consisting of : -
(i) The bottom ash handling system employing W-type water impounded hoppers and jet pumps, the plant shall include, at least, the following basic elements.
(a) Two (2) numbers water impounded bottom ash hoppers of structural steel complete with hydraulically operated discharge gates, refractory cooling arrangement, hopper overflow, water seal boxes, sluicing headers with nozzles, seal trough with overflow connection, refractory lining, access doors, observation and inspection glass windows, poke holes supporting steel structures, platforms, stairs and all accessories as specified and as required.
(b) Eight (8) numbers, clinker grinders complete with drive motors, fluid coupling, gear reducers and accessories as specified as required.
(c) Eight (8) numbers jet pumps alongwith discharge gate housing, using flushing and drain connection, etc. as specified and required.
(d) Four (4) length of bottom ash slurry transportation MS lines complete with pipe bends, fixtures, elbows, gaskets, nuts, bolts, structural steel supports and other accessories as specified and as required, from the outlet of jet pumps to the ash slurry sump in the Ash slurry pump house.
(f) Eight (8) numbers solenoid operated pneumatically actuated knife edge gate valve at the outlet of jet pumps.
126.96.36.199 Economiser Ash Handling System
(a) Thirty six (36) numbers flushing equipment below economiser/economiser bypass duct ; primary and secondary air preheater hoppers, complete with flushing nozzles, expansion joints, vertical pipe connections, gaskets, slurry discharge and overflow pipes and necessary fixing clamps and structural steel supports as specified and as required.
(b) Thirty six (36) numbers hopper isolation valve assemblies as specified complete with hopper connecting flanges, gaskets, nuts, bolts etc.
(c) MS disposal pipes for transfer of economiser and air preheater ash slurry from flushing apparatus to economiser/APH slurry trench complete with pipe bends, fixtures, elbows, gasket, supporting steel structure etc.
(d) Alloy cast iron liners for lining the slurry trenches.
(e) All instrument air piping to the various valves and instruments complete with fittings, valves, pressure reducing station, filters, flanges, gaskets, nuts and bolts, hangers, supports, etc.
(f) All instrumentation and control.
188.8.131.52 Dry Fly Ash Extraction System
Scope under this specification for dry fly ash extraction system starts from electrostatic precipitator and air pre heater ash collection hoppers outlet onwards and consist of :-
(i) For Vacuum Extraction System
(a) One (1) no. material handling valve/feed valve at the outlet of each ESP and duct hopper. One (1) no. chute isolation valve at the outlet of each ESP hopper and duct hopper. Expansion joints wherever required shall also be provided.
(b) Sixteen (16) nos. Mechanical vacuum pumps alongwith drive and accessories for two (2) units. Out of 16 nos. 8 nos. shall be working & eight (8) nos. shall be dedicated standby.
(c) Dry fly ash conveying cast iron pipes from ESP and duct hopper outlet onwards upto buffer hoppers/collector tanks complete with valves, specialities, bends, hydraulic/pneumatic actuators, structural steel supports, platforms, etc.
(d) Eight (8) nos. fly ash surge-cum-collection buffer hoppers each complete with supporting steel structures, platforms, stairs, aeration system, primary collector, secondary collector alongwith bag filter etc. or target box alongwith bag filter etc. for two (2) units.
(e) Sixteen (16) nos. collector tanks each complete with wetting heads, air-washers, seal boxes supporting structure, platforms etc. for both the units.
(f) All interconnecting compressed air/exhaust pipelines complete with valves and fittings and supporting steel structure.
(g) M.S. Disposal pipes for transfer of slurry from collector tank to fly ash slurry trench with supporting structures. Fly ash slurry trench shall be provided below collector tanks to transfer fly ash slurry from collector tanks to slurry sump in the combined ash slurry pump house as specified and as required.
(h) Alloy cast iron liners for lining the slurry trench upto ash slurry pump house.
(i) All nuts, bolts and jointing materials at flanged termination points.
(j) Mechanical ventilation (supply/exhaust fans) for different areas in vacuum/extraction compressor house and air conditioning of control panel rooms.
(k) Two (2) number (1 no. for each vacuum pump house/extraction air compressor house) pendant controlled electrically operated overhead travelling crane as specified complete with runway rails, necessary rail clamps, bolts, splice bars and stops for each of the runway.
(l) Four (4) x 100% instrument air compressors alongwith its air drying plants, air receivers complete with motors, valves, pads and pipelines alongwith supporting steel structures to meet the complete requirement of ash handling plant such as actuation of material handling, segregation valves ; various water and airline valves, slurry valves ; bag filter cleaning etc.
(m) 2 x 100% capacity aeration blowers per unit (i.e. total four (4) numbers) for aeration of buffer hoppers complete with heaters, valves, pipelines including supporting steel structure, insulation, silencer, filters and all other accessories as specified and as required.
(n) All instrumentation and control.
184.108.40.206 Dry Fly Ash Transportation and Storage System
Scope under this specification for dry fly ash transportation and storage system starts from the outlet of buffer hoppers and consists of :-
(a) Sixteen (16) nos. of pump tanks/air locks/eductors/ash transporters, two each at the outlet of each buffer hoppers, for transportation of dry fly ash to storage silos.
(b) Three (3) nos. transport air compressors alongwith silencer, filter, drive motor, after cooler alongwith all other accessories and supporting structures, platforms etc. as specified and as required.
(c) Three (3) nos. refrigerant type air dryers alongwith accessories as specified and as required.
(d) Three (3) numbers air receivers alongwith safety relief valve, automatic drain trap and other accessories as specified and required.
(e) Three (3) lengths of cast iron pipes of adequate thickness for fly ash conveying from surge/buffer hoppers to storage silos, including pipe rack, trestles, platforms, access stairs and other associated supporting steel structure and other accessories as required.
(f) Two (2) nos dry ash storage structural steel silos each of 1000 M³ effective capacity and complete with an aeration system, dust separators and all other accessories as required and as specified. The silos shall be complete with all fittings, accessories and supporting steel structures access staircases, platforms, stainless steel liners as required for safe and reliable operation and maintenance of dry fly ash storage system.
(g) Aeration plant consisting of three (3) numbers silo aeration blowers (one for each silo+one common standby) complete with heaters, valves, pads and pipelines including supporting steel structures, insulation, silencer, filter and all other accessories for aeration of silos.
(h) One (1) no. air receiver alongwith safety relief valve, automatic drain trap and other accessories complete with supporting steel structures to meet the complete requirement of ash storage silo such as actuation of material handling, segregation valves ; various water and airline valves, slurry valves ; bag filter cleaning etc.
(i) Target box and bag filter assembly alongwith pulse jetting arrangement, fan units etc. and other accessories.
(j) Slide plate valves below storage silos.
(k) Two (2) numbers of hydro-mix conditioner units alongwith drive motor, ash feeding & measuring arrangement, one (1) number for each silo, alongwith associated water piping and valves, for unloading the conditioned fly ash into trucks.
(l) Three (3) nos.. water booster pumps (1 for each unloader + 1 common standby) for conditioned ash unloaders alongwith drives and controls as required and specified.
(m) Two (2) number of Dry fly ash unloaders (one for each dry fly ash storage silo) alongwith rotary feeders, telescopic chutes and other accessories as specified and as required.
(n) All necessary hydraulic or pneumatic actuators.
(o) All interconnecting compressed air pipelines complete with valves, fittings, pipe rack and supporting steel structure.
(p) 2 x 100% wash water pumps alongwith drive motor and accessories in silo area alongwith dedicated hose pipe.
(q) 2 x 100% vertical sump drainage pumps alongwith drive motor and accessories in silo area to pump the accumulated ash water to the combined ash slurry disposal pump house sump including piping alongwith necessary valves, fittings, supports, etc. as specified as required.
(r) Two (2) number pendant controlled electrically operated overhead travelling crane one (1) number each in transport air compressor house and silo area utility building to handle the equipment in the transport air compressor house and silo area utility building pump & blower room, as specified complete with run way rails, necessary rail clamps, bolts, splice bars and end stops for each of the runway.
(s) All nuts, bolts and jointing materials at flanged termination points.
(t) Mechanical ventilation (supply/exhaust fans) for different areas in utility building and air conditioning of control panel rooms.
(u) All instrumentation and control.
220.127.116.11 Ash Slurry Disposal System
Scope under this specification for ash disposal system starts from ash slurry sump in the combined ash slurry pump house and consists of :
(i) In the combined Ash Slurry pump house
(a) Four (4) streams of horizontal ash slurry disposal pumps, complete with drive motors, variable speed hydraulic couplings, for first stage pumps and fixed belt drive arrangements for subsequent stages, base plates, foundation bolts, inserts, embedments and accessories as specified and as required.
(b) Four (4) lengths each of 6 km length of ash slurry disposal pipelines (excluding the length of bends & fittings) from the ash slurry pump house to the ash dyke including the lines around the ash dyke and extensions into the dyke at a number of discharge points complete with basalt lined bends, specialities, fittings, fixtures, pipe couplings, gaskets, nuts, bolts, clamps, embedments, structural steel supports for piping system and other accessories.
(c) Complete ash slurry piping alongwith bends, supports alongwith bolts, nuts, clamps etc. inside the ash slurry pump house. All the piping inside the pump house shall be basalt lined.
(d) Eight (8) nos. adequately sized motor operated or solenoid operated & pneumatically actuated metal to metal seated knife edge gate valve/100% tight shut off rubber lined knife edge gate valves/plug valves shall be provided at the suction and discharge of combined ash slurry disposal pumps.
(e) Two (2) nos. slurry sump compartment isolation valves.
(f) Adequate no. of manually operated plate valves at the slurry disposal pipelines outlets in the dyke area as specified and as required.
(g) Two (2) nos. vertical sump drainage pumps with motors complete with piping, valves, fittings, supports, inserts, sleeves etc.
(h) Alloy Cast iron liners (as specified) for lining the ash slurry sumps.
(i) One (1) no. pendant controlled electrically operated overhead travelling crane to handle the equipment in ash slurry pump house, as specified complete with runway rails with necessary rail clamps, bolts, splice bars and end stops for each of the runway.
(j) Mechanical ventilation (supply exhaust fans) for different areas in ash slurry pump house and switchgear rooms.
(k) All instruments and control .
18.104.22.168 Ash Water Pumps, Water Piping and Accessories :
(a) All types of Ash water pumps namely Bottom ash LP water, Bottom ash HP water, Fly ash HP water, Flushing water pumps etc. complete with drive motors, base plates, foundation bolts, inserts, embedment and accessories as specified and as required. Complete ash water pipe lines, valves, fittings, pipe rack, structural steel supports for piping system and other accessories as specified and as required. The ash water pumps namely Bottom ash LP water, Bottom ash HP water, Fly ash HP water, Flushing water pumps are to be located in Ash water pump house.
(b) Seal/cooling/other water pumps and motors complete with all the accessories of drive and mounting as specified and as required.
(c) Bottom ash over flow water system
(i) Two (2) number Bottom ash over flow water storage tank, one (1) number settling tank and one (1) number surge tank, including their structural steel supports.
(ii) Four (4) numbers (3×50% capacity) bottom ash over flow water pumps complete with drive motors, variable speed hydraulic coupling and other accessories as specified and required for pumping BA hopper cooling water overflow from Bottom ash overflow water storage tank/sump to settling tank.
(iii) Bottom ash overflow water pipes from BA hopper to BA overflow water storage tank, from BA overflow water tank/sump to suction of BA overflow water pumps, from discharge of BA overflow water pump to settling tanks complete with valves, fittings, structural steel supports etc. Overflow transfer pipes to transfer clear water from surge tank to overground sump of ash water pump house, by gravity flow.
(iv) Two (2) nos. sludge pumps, to remove sludge from settling & surge tank to sump of combined ash slurry pump house.
(v) Any treatment facility required to ensure that bottom ash over flow water total suspended solids is restricted to 100 ppm.
(d) All ash water and seal water piping to all the equipments and sumps complete with fittings, valves, strainers, flanges, gaskets, nuts, bolts, hangers, supports, flushing nozzles, agitating nozzles, etc. as specified as required.
(e) All overflow and drain piping from various equipment to the nearest plant drainage as required.
(f) One (1) no. pendant controlled electrically operated overhead travelling crane to handle the equipment in Ash water pump house, as specified complete with runway rails with necessary rail clamps, bolts, splice bars and end stops for each of the runway.
(g) All instrumentation & control.
Two nos. 3.3 kV supply feeders shall be provided from 3.3 kV station board for feeding supply to entire AHP.
1. H.T. Switchgears
One (1) no. 3.3 KV, switchgear of adequate rating consisting of two incomers and one bus coupler which shall cater to all the HT/LT loads of Ash handling plant as supplied by bidder.
(a) Adequate nos. 3.3 KV/0.433 KV, oil filled outdoor type transformers of adequate rating, two (2) nos. each outside LT switchgear room near vacuum pump house/compressor house for each unit.
(b) Adequate nos. 3.3 KV/0.433 KV, oil filled outdoor type transformers of adequate rating outside LT switchgear room at ash water pump house.
3. LT Switchgear
(a) Two (2) nos. 415V, MCCs, one for each unit located in the switchgear rooms near respective vacuum pump/compressor houses of adequate rating. These MCCs shall receive power from the 415 V switchgear under bidder’s scope and shall feed power to various LT loads of vacuum pump/compressor house and bottom ash system through two (2) nos. 3.3 KV/0.433 KV transformers for each unit.
(b) One (1) no. 415V MCC located in LT switchgear room near Ash water Pump house of adequate rating. This MCC shall receive power from the 3.3 KV switchgear under bidder’s scope and shall feed power to various LT loads of Ash water pump house through two (2) nos. 3.3 KV/0.433 KV transformers under bidder’s scope. This MCC shall provide incomers to Ash slurry pump house MCC also.
(c) One (1) no. 415V MCC located in LT switchgear room in Silo area of adequate rating. This MCC shall receive power from Bidder’s own MCC.
(d) One (1) no. 415V MCC located in HT/LT switchgear room near Ash slurry pump house of adequate rating. This MCC shall receive power from bidder’s Ash water pump house MCC and shall feed power to various LT loads of Ash slurry pump house.
4. (a) Three (3) nos. A.C. fuse boards and four (4) nos. DC fuse boards.
(b) Local push button stations for all drives and local motor starters for ventilation fans.
(a) All 3.3 KV/1.1 KV, XLPE/PVC, FRLS, power control and special cables as required.
6. Cabling viz. cable laying alongwith cabling accessories, cable trays with supporting structures, terminations and jointing kits, overhead trestles etc.
7. Complete illumination system as required for complete internal & external lighting of associated plant and buildings.
8. Complete earthing and lightning protection alongwith earth grid and its interconnection to the nearest earth grid.
November 16, 2009
2.2.3 Control and Instrumentation
i) All instruments like local gauges and switches for pressure/differential pressure (DP)/vacuum/temperature, flow, level; Transmitter for pressure/DP, flow and level, including hopper level, RTDs for temperature measurement, control valves etc. shall be provided as per enclosed tender drawings and as required for safe and efficient operation of the entire plant.
ii) All required instrumentation cables and junction boxes shall be provided for interconnection of contractor supplied instrument and control device, PLC based control panels and MCC switchgear.
iii) Control System
(a) PLC based control system for the entire ash handling plant
(b) (i) One (1) no. Main control desk located in the main control room near ash slurry pump house alongwith mimic of entire ash handling plant, push buttons, control & selector switches, lamps, meters & annunciation windows.
The mimic of the entire ash handling plant alongwith HT/LT switchgears shall be configured on the Operator Work Stations (OWS).
One (1) no. processor panel for housing the hot redundant processors. Further, redundant LAN ports shall be provided for integration with Purchaser’s DDCMIS.
(ii) Two (2) nos. Bottom ash local control panels with mimic one for each unit for control of various drives in bottom ash area. Necessary push buttons, control/selector switches, lamps, meters, annunciation windows etc. shall be provided.
(iii) One (1) no. silo control panel with mimic for control of various drives in silo area alongwith necessary push buttons, control/selector switches, lamps, meters & annunciation windows.
All the above control desk/panels shall include necessary I/O racks.
(iv) Remote I/O racks as per system requirement.
(c) High & low level switches of ESP Ash hoppers shall be wired to the I/O racks for control, monitoring & annunciation.
22.214.171.124 Operational Philosophy, Control and Instrumentation
a) Control Panels
Control of various pumps, valves, drives and the system be achieved from the respective control panels to be offered by the Bidder and to be located as below :
(i) Main control desk - 1 no. located in control room near Ash Slurry pump house.
(ii) Bottom Ash Local - 2 nos. (1 for each unit) located in control panel boiler area at 0.0m.
(iii) Silo Control - 1 no. located in Silo area.
b) Basic Control Philosophy
Bottom Ash Handling System
Bottom ash system shall be manually operated from the local bottom ash control panel of 0.00 m elevation located near the respective Boiler. One no. bottom ash control panel shall be provided for each unit. The operating status of bottom ash handling system equipments of both the units shall be reflected in the mimic diagram of bottom ash handling system mounted in the main control desk in main control room located near ash slurry pump house.
Fly Ash Handling System
Control for each unit fly ash extraction and conveyance plant shall be based on separate programmable logic control (PLC) systems in accordance with PLC specification. The basic control philosophy is given below :
Fly Ash Extraction
a) The main control desk located in main control room near ash slurry pump house common for both the units under the scope of this contract shall also control duct hopper and ESP ash extraction. It will have mimics for indication and control of entire ash handling plant.
b) All process control for fly ash extraction of each unit shall be obtained from the main control desk. However, direct local switching of individual drives and actuators shall be possible for maintenance purpose with the necessary basic protection incorporated. “Local/Remote” switching shall disable the relevant remote process control when in “Local” mode.
c) The operator will normally pre-set-up the required de-ashing routing and sequence to management instructions. Subject to completion of the necessary permissive and sequence interlocks operator “Start” initiations of the appropriate lines would automatically select and start the service plant for commencement of de-ashing.
d) Once started, the systems, will continue in automatic operation as programmed. It shall be possible for the operator to make on-line adjustments to timings, routings, selections etc. with appropriate ‘selection checks’ before “Command” initiation. Also programme interruption shall be possible to effect unscheduled or out of sequence extraction before return to the original programme.
e) The emptying of the fly ash collection chute groups to the buffer hoppers or wetting heads will be performed in a pre-determined sequential manner. The command signal for automatic switching over from one group of collection chutes to the next shall be based on the lapse of a set time period. The sequencing of collection chute emptying shall be adjustable, the chute empty signal will be suitably delayed to account for the time required to evacuate the ash remaining below low level probe.
f) Manual intervention to permit collection from a collection chute group out of sequence will be provided at the main control desk. This would normally be followed by restarting of the sequence unless further manually directed. Fly ash from ash group of chutes will be pneumatically conveyed to the appropriate intermediate/ surge hopper or storage silo or wetting head.
Ash Water System & Bottom Ash Overflow Water System
Ash water, seal water pumps, bottom ash overflow water system and associated facilities shall be operated from the main control desk located near ash slurry pump house. The operating status of all ash water, seal water pumps and bottom ash overflow water system shall be reflected in the mimic diagram of ash handling plant mounted on the main control desk.
Ash Slurry Disposal System
Ash slurry disposal pumps, associated make –up and slurry valves shall be operated from the main control desk located in main control room near ash slurry pump house. The operating status of ash slurry disposal pumps and various valves shall be reflected in the mimic diagram of ash handling plant mounted on the main control desk.
Silo Area :
One (1) no. silo control panel shall be provided for controlling the unloading of ash from two (2) silos. Operating status of various equipments shall be reflected in the mimic diagram of the ash handling plant mounted on the main control desk.
The above is only a general description of operational philosophy. The Bidder shall include in his proposal a detailed description of the control system as offered by him and as required for safe operation of the plant, complete with bill of materials, schematic diagrams, description of function of different components, component ratings etc.
126.96.36.199 Protective Interlock Arrangement for Ash Handling System
To ensure safe operation of the equipment connected with handing system of bottom ash and fly ash, the following minimum protective features and safety interlocks shall be included in Bidder’s scope of supply.
i) It shall not be possible to start the Bottom Ash overflow water pump and ash slurry disposal pump unless the following conditions are satisfied:
a) Pre-set gland seal water pressure is available.
b) One stage of pumps shall start only if other stage/stages in the upstream side of this stage is running. (Applicable to series pumping only).
c) Suction valve is open
d) Main Ash slurry sump and BA overflow water tank level is at or above the preset safe operating level.
e) In case of series pumping the sequence of starting of each series of slurry disposal pumps shall be suction valve first, 1st stage pump (closest to suction valve) next, followed by 2nd stage pumps so on and finally discharge valve. This shall be achieved by sequence start control switches.
f) By using a suitable device, the interlock requiring the last stage is tripped when discharge valve is closed is to be suitably by passed during a normal starting. However, the pump shall automatically trip if the discharge valve fails to open within a preset time after starting of the last stage pump.
ii) The BA overflow water pump and ash slurry disposal pumps shall trip in the event of the following emergency conditions.
a) Seal water pressure falls below a preset value (for any stage of pumping).
b) Main Ash slurry sump and BA overflow water tank level falls at or below preset danger (low) level.
c) If for any reasons one pump stage in a series tank, the other stages of the series shall also trip. (Applicable to series pumping).
d) Suction/discharge valve is closed.
iii) The discharge valve of BA overflow water pumps, ash slurry disposal pumps shall close as soon as the slurry pump/last pump stage in the series has tripped. Discharge valve will open after running of Ash slurry pump stream.
iv) a) It shall not be possible to start the clinker grinder motor unless the preset gland water pressure for the grinder is available and preset water pressure is available at jet pump.
b) In the event of gland seal water pressure falling below preset value, the running grinder motor shall trip and the corresponding hopper gate closed.
c) In the event of an overload on the grinder, the grinder motor shall trip. In such a case, subject to availability of preset gland seal water pressure, the ginder motor shall reverse in short impulses to remove materials jammed in the grinder. After pre-determined cycles, in case jamming is not cleared, the grinder motor shall trip.
d) It shall not be possible to open the hopper discharge gate unless clinker is started and running.
v) Protective interlocks on fly ash handling system :
a) Evacuation initiation and status monitoring check shall include:
- Air pressure/vacuum and flows
- Valves status
- Surge/buffer hoppers/storage silos levels/ESP hopper ash & Blow Tank/ash transporter Level
vi) Protective Interlock Arrangement for Ash Water Pumps
It shall be possible to keep any one Ash Water Pumps as standby. Ash Water Pump shall be arranged to start automatically when any one of the working Ash Water pumps trips of Ash Water Line Header pressure falls below pre-set value.
vii) Level Detection Equipment for Combined Ash Slurry Sump, Ash Water Sumps, Drain Sumps and Settling Tanks of BA overflow water system.
The Bidder shall furnish the following equipment for the detection of Level is sumps:
a) High Level & Low Alarms
Necessary Sump level switches shall be furnished for providing annunciations in Control Panels. The electric switch assembly of the above level switches shall be located outside water space. Horns and other accessories shall be provided for local alarms.
b) Low Level Switch for Tripping of Pumps
Low level switches shall be provided for tripping the slurry pumps, for extreme low level (danger level) of sumps.
c) Level Indicators
Level indication device complete with local arrow scale type level indicator shall be provided for all sumps.
d) Tank/Sump Make-up Water Valve
The Bidder shall supply adequate size valves for installation in the make-up water line to ash slurry sumps/tanks. These valves shall be complete with device for operation form main control panels. The valves shall be ON-OFF type.
viii) Seal Water Pump Control
a) It shall be possible to start the seal water pumps only if preset suction pressure is available.
b) The seal water pump shall trip in the event of suction pressure dropping below preset value.
c) During normal operation, any one of the two seal water pumps shall be working. On seal water discharge pressure falling below a preset value, the standby pumps shall be automatically switched on subject to availability of preset suction pressure. Starting of this standby pump shall be annunciated in the main control panel. It should also be possible, by means of selector switch provided in the main control panel, to keep any one of the pumps as normally working and other as standby.
ix) Sump Drainage Pump Controls
Either of the two (2) sump pumps provided in Ash Supply pump house, BA pumphouse & silo area shall be automatically switched on if the level in the sump rises above a preset level. The second pump shall automatically start if the first pump fails to start when level is high or if the level continues to rise.
The operating pump shall trip in case the sump level goes below a preset level.
November 13, 2009
2.3.1 Design Data
The bidder shall base the design of the ash handling plant on the ash densities and production rates given below, the predicted ash distribution, the requirements of this specification, and the normal safety margins which the Bidder includes in his design of ash handling plant.
(a) Ash Densities
(b) Ash Distribution in the boiler/ Ash Collection System
* Bottom Ash - 20%
* Economiser Coarse Ash - 5%
* Air pre-heater/ duct Ash - 5%
* ESP ash - 90%
(c) As the ESP is designed to operate satisfactorily with one or more fields de-energised if it is assumed that no more than two fields will be out of service at any one time.
(d) Even when any ESP field is not in operation then also mechanical collection of ash will take place due to sudden drop in velocity experienced by ash particles. This aspect shall also be considered by Bidder while designing the system.
(e) Electrostatic Precipitator Design
Each unit is provided with four (4) nos. of Electrostatic precipitators with a total of 128 ash collection hoppers per boiler. Each ESP has eight (8) fields each having four (4) nos. collection hoppers. These ash collection hoppers are located directly beneath the fields and receive the fly ash dislodged from the collecting electrodes and emitting systems. The collecting hoppers are of inverted pyramidal shape with an outlet opening size of 400 mm x 400 mm (in side) and are designed to have a minimum valley angle of 60 deg. This valley angle is provided to ensure free flow of fly ash. Each of the first field hoppers of each ESP has a capacity of twelve (12) hour ash collection.
All other hoppers have same volumetric capacity as that of the first field hoppers.
Collection hoppers heaters are provided, to avoid condensation of water vapour on the inside surface of the collection hopper. The Bidder shall ensure a gas-tight joint at each collection hopper chute, to avoid admission of moisture into the collection hoppers, which may interfere with the free flow of ash from the ash collection hoppers, due to ash depositing on the collection hopper inner surfaces.
The rapping mechanism for the collecting electrodes has adjustable duration. The first field of the ESP which collects the maximum amount of fly ash is rapped most frequently (for example approximately 20 times per hour, that is once in every 3 minutes). The amount of ash that has been collected during the above period will be rapped off in a short duration of one minute, with the result that the ash handling system will have to cope with sudden surges in the pattern of ash collection in the collection hoppers.
When the first field is rendered in-effective due to any reason the second field which was earlier collecting ash at a lower rate, will now be collecting at an increased rate equal to that in first field. The same logic applies for the subsequent fields in series. The ash handling system shall be designed to cater for the switching out of any two fields with the consequent increase in removal rates in the remaining fields.
2.3.2 Ash Removal Rates, Slurry disposal and dry ash Storage
188.8.131.52 Ash Removal Rates
The proposals shall be based on the following ash removal rates:
(a) The bottom ash removal system employing W-type water impounded hoppers and jet pumps, the system shall be capable of removing the accumulated bottom ash of four (4) hours production at the specified rates within 1hrs. 30 min. (90 minutes) period including the time required for starting, stopping, sequential changeover from one unit to second unit and water flushing of the system for the following two conditions.
(1) Maintain water level by allowing the make up valve to remain open.
(2) Complete draw down by totally emptying the hopper of all water and ash with the make-up valve closed.
Bidders may assume that the bottom ash from each individual hopper section will be removed in parallel. Bottom ash from each boiler shall be removed in series/sequence.
(b) Economiser and air preheater ash shall be removed continuously at the collection at specified rate. The economiser and air preheater ash removal of two boilers will be done in parallel and continuously.
(c) (i) The fly ash handling plant capacity shall be based on removing the total fly ash (from ESP and duct collection hoppers) produced by each boiler continuously operating during period of 8 hrs. within a 6 hrs. period. The fly ash handling plant associated with each of the two (2) boilers. shall operate in parallel.
ii) The capacity of second stage, conveying (i.e. transportation of dry ash upto main silos outside/near the plant boundary) shall match the capacity of extraction system.
184.108.40.206 Ash Slurry Disposal Rates
The ash slurry disposal system shall pump the resultant ash slurry generated from both the bottom & fly ash handling system continuously from the slurry sump to the disposal area through pipe lines at guaranteed rate with two (2) pump series in operation and both the units working.
220.127.116.11 Dry Ash Storage
Bidder shall provide two (2) nos. dry fly ash storage silo to collect dry fly ash from the Electrostatic precipitators as and when required.
The minimum effective capacity at each fly ash storage silo shall be 1000 m³.
The full procedures for conducting of tests for testing the plant shall be agreed between the Owner and the Contractor prior to placing of the order. Before acceptance by the Owner, the completely erected plant shall be tested by the Contractor on site under normal operating conditions. The contractor shall also ensure the correct performance of the plant under abnormal condition, where applicable, i.e. the correct working of the various emergency and safety devices.
Bidder should provide complete details of their normal procedures for the testing of the quality of erection and of the performance of the erected plant. These tests should include the following at least:
A site pressure/vacuum test on all erected pipe work to demonstrate the quality of the piping and the adequacy of joints made at Site.
All the equipments shall be test run at site to demonstrate their smooth, vibration free and trouble less operation.
Site tests shall be carried out to prove satisfactory operation of electrical interlocks for each individual equipment and for the complete system.
The control panels and instruments furnished by the Contractor shall be used for the purpose of the performance and guarantee tests. If additional instruments and other accessories are required during the test, the same shall also be furnished by the Contractor and shall remain the property of the Contractor after successful completion of the tests.
November 12, 2009
(a) Performance and Guarantee tests shall be conducted in accordance with the conditions specified in ‘General Technical Conditions’ of Technical Specifications
(b) The performance guarantee tests shall be conducted for Seven (7) days continuous operation of the boiler at 80% to 100% load. In case, the boiler trips during the test duration the interpretation of performance test shall be mutually agreed between OWNER and bidder. In case of any major breakdown in any of the equipment disrupting the operation of Ash Handling Plant, the breakdown period shall be added to the testing period of 7 days.
(c) The performance guarantee test shall be conducted to prove uninterrupted operation of ash handling plant of each unit separately as they are completed and all units simultaneously when they are completed. The ash handling plant shall be operated with its normal auxiliaries, (as applicable commensurate with the number of boiler units in operation) without using standby pumps or any other standby equipment. During the performance guarantee test, the guarantee parameters of the various equipments as detailed below shall be demonstrated by the Contractor. In addition to above shop and site tests, the test requirement specified in subsequent section for Mechanical, Electrical, Civil and Structural items shall also be complied with by the bidder.
2.5.1 Guarantees and Liquidated Damages Guarantees
The performance and guarantee test shall be conducted in accordance with the conditions specified in General Technical conditions, and in Clauses above. The parameters guaranteed by the Bidder shall have no tolerance value whatsoever. The equipment and systems offered under this specification shall be guaranteed to meet the following performance.
(a) Bottom Ash Handling System
(1) In case the Bidder offers intermittent type bottom ash removal system employing W-type water impounded hopper and jet pumps, the system shall be guaranteed to meet the following performance. (i) Continuous effective extraction, crushing and conveying of bottom ash generated during various modes of boiler operation to the ash slurry sump and the continuous effective pumping of combined slurry from this sump to the ash slurry dump area. The extraction of bottom ash and economiser ash shall be done twice in every shift of eight (8) hours. The total time for evacuating the 4 hours collection of bottom ash and economiser ash corresponding to maximum collection rates specified shall not exceed 1 hour 30 minutes (90 minutes) including the time required for starting, stopping, sequential changeover from one unit to second unit and water flushing of the system for the following two conditions and with 25mm wear on the diameter of the throat section of the jet pumps : – Maintain water level by allowing the make up valve to remain open. – Complete draw down by totally emptying the hopper of all water and ash with the make up closed. (ii) Power consumption (KW) as measured at motor input terminals for ash crusher/clinker grinder operating during continuous effective ash extraction rate as outlined in 1 (i) above. (2) In case the Bidder offers continuous type bottom ash removal system employing submerged scrapper chain conveyors, the system shall be guaranteed to meet the following performances. (i) Continuous effective discharge, crushing and sluicing of bottom ash generated during various modes of boiler operation to the bottom ash slurry sump and the continuous effective pumping of slurry from this sump to the main slurry sump in ash slurry pump house for onward effective pumping from main sump to the ash slurry dump area. (ii) (a) Continuous normal extraction capacity (50 T/hr or 25 T/hr as the case may be) of the submerged scrapper chain conveyors with the linear speed of chain not exceeding 2.0 m/min. (guaranteed extraction rate). (b) Dead start capability of submerged scrapper chain conveyor i.e. it shall be able to start and discharge the bottom ash with water filled trough full of bottom ash upto maximum water level. (iii) Power consumption (KW) as measured at motor input terminals for submerged scrapper chain conveyor operating at the guaranteed extraction rate. (iv) Power consumption (KW) as measured at motor input terminals for ash crusher operating at the guaranteed bottom ash extraction rate. (v) Rated capacity at Rated Head of each bottom ash slurry transportation pumps/bottom ash overflow water pumps, sludge pumps etc. (vi) Power consumption (KW) of each bottom ash slurry transportation pumps/bottom ash over flow water pumps/surge tank over flow transfer pump above as measured at motor input terminals when operating at the rated capacity and head as stated in 2(v) above. The performance test listed at 2(iv), 2(v) & 2(vi) above shall be performed on test rig at the vendor’s works and actual motor shall be used for this purpose. (3) The continuous effective conveying and pumping as stated above shall be established by no stagnation of ash or slurry at any point in the complete system and with all interlocks, protections and sequential operation working satisfactorily.
(b) Economiser and Air preheater
Ash Handling System Continuous effective extraction and conveying of ash collected in economiser, economiser bypass duct, primary air preheater and secondary air preheater hopper from hoppers to economiser/air preheater slurry trench; from economiser/air preheater slurry trench/pipe line to ESP fly ash slurry trench; from ESP fly ash slurry trench to sump of combined ash slurry pump house. The continuous effective extraction and conveying of ash as stated above shall be established by no stagnation of ash or slurry at any point in the complete system and with all interlocks, protections working satisfactorily.
(c) Fly Ash Handling System
(i) Continuous effective extraction and conveying of fly ash from all fly ash collection hoppers i.e. ESP and duct hoppers, generated during various modes of boiler operation upto collector tank/ buffer hoppers, from buffer hoppers to ash storage silo and from collector tank to the ash slurry sump and the continuous effective pumping of ash slurry from this sump to dyke area. The fly ash collected in each unit in every shift of eight (8) hours corresponding to maximum ash collection rates shall be extracted in six (6) hours. (ii) The continuous effective extraction conveying and pumping as stated above shall be established by no stagnation of ash or slurry at any point in the complete system and with all interlocks, protections and sequential operation working satisfactorily. (iii) Rated capacity at rated discharge pressure of each air compressor/blower/vacuum pump as applicable. (iv) Power consumption (KW) of air compressors/Blowers/vacuum pumps, as applicable, as measured at motor terminals when operating at the rated capacity and pressure as stated in b(iii) above. (v) The performance listed in c (iii) & (iv) above shall be performed on test rig at the vendor’s works and actual motor shall be used for this purpose.
(d) Ash water and Seal Water Pumps
(i) Rated capacity at rated head of each ash, seal and flushing water and other water pumps. (ii) Power consumption (KW) of each ash, seal and flushing water pump and other pumps as measured at motor input terminals when operating at the rated capacity and head as stated in c (i) above. (iii) The performance listed in c (i) & (ii) above shall be performed on test rig at the vendor’s works and actual motor shall be used for this purpose.
(e) Ash slurry Disposal Pumps
(i) Rated capacity at Rated Head of each ash slurry disposal pump. (ii) Power consumption (KW) of each ash slurry disposal pump as measured at motor input terminals when operating at the rated capacity and head as stated in d (i) above. The power consumption figure shall be corrected to take into account ash slurry as the pumping medium. (iii) The performance listed in d(i) & (ii) above shall be performed on test rig at the vendor’s works and actual motor shall be used for this purpose.
(f) The value of the various performance guarantee parameters stated above shall be as per the requirements specified in the equipment specifications. Where not specified, these shall be as per guarantees furnished by the Bidder.
2.5.2 Liquidated Damages Should the results of the performance and guarantee tests show that the equipments has failed to meet the guaranteed parameters, the Contractor shall carry out modifications considered necessary within 90 days of the notification by the Owner. If the equipment fails to meet the guarantee (except the power consumption) at the end of the above specified period of 90 days, the Owner may at his discretion reject the equipment. The total power consumption for the complete ash handling plant of two (2) units shall be worked out by using the following formula: P = (p × n × f) P = Total power consumption. p = Power consumption of the Individual drives listed below, at motor input terminals without any negative tolerance n = No. of drives in operation f = weighting factor for the various drives as listed below The guaranteed power consumption for the package shall be worked out by using the guaranteed 'p' value indicated by the Bidder in relevant Schedule (Guarantee Declaration Schedule) of 'Bid Proposal Sheets'. The actual power consumption for the package shall be worked out by using the measured 'p' value during PG tests (at shop or site as the case may be). Using the above computation method, if the actual power consumption exceeds the guaranteed power consumption, liquidated damages shall be payable by the Contractor at the rate of Rs.1,24,000/- per KW excess power consumption, over the base guaranteed figure indicated by him in his bid. Such liquidated damages may be recovered by the Owner by deduction from the contract price or by enforcing the contract performance guarantee or in any other manner deemed fit by the Owner. For this purpose, the drives of standby equipment shall not be considered. List of drives with guaranteed power consumption and weightage factors thereof.
Drive Weightage Factor
1. Bottom Ash Crushers 0.3125 for jet pump system & 1.0 for submerged scrapper conveyor system.
2. Bottom Ash H.P. 0.3125 for jet pump system Water Pump
3. Bottom ash L.P. Ash 1.0 Water Pumps
4. Fly ash water pumps 1.0
5. Bottom Ash Slurry 1.0 Transportation pumps
6. Submerged scrapper 1.0 chain conveyor
7. (i) Fly ash extraction 1.0 air compressors with air drying plant (ADP) (ii) Fly ash extraction 1.0 vacuum pumps (iii) Buffer hopper aeration 1.0 Blower alongwith heater (iv) Silo aeration blower 1.0 with heater (v) Transport air 1.0 compressor with air drying plant
8. BA hopper cooling water 1.0 over flow pumps/sludge pumps
9. Ash slurry disposal 1.0 pumps
10. Seal/cooling water pumps 1.0
11. Instrument air compressor 1.0 with air drying plant
The Contractor shall indicate and include in his scope of supply all the start-up commissioning spares. The contractor shall further separately indicate the prices of recommended spares necessary for three (3) years continuous operation, in addition to mandatory spares. The Contractor shall also identify the total population of each item of spares both mandatory, and recommended, and their service life expectancy under normal operation conditions, with his bid in the form of Schedules. All spares supplied under this contract shall be strictly interchangeable with the parts for which they are intended for replacement. The spares shall be treated and packed for long storage under the climatic conditions prevailing at the site e.g. small items shall be packed in sealed transparent plastic bags, with desiccator packs as necessary. Each spare part shall be clearly marked or labeled on the outside of the packing, together with the description. When more than one spare part is packed in single case, a general description of the contents shall be shown on the outside of the case, and detailed list enclosed. All cases, containers and other packages must be suitably marked and numbered for the purpose of identification. All cases, containers or other packages are liable to be opened for examination, as may be considered necessary by the Engineer.
2.6.2 Mandatory Spares Parts The list of mandatory spares which are considered essential by the Owner shall be indicated and the Bidder shall quote prices for all these spares. The Bidder shall furnish the itemized and total price for these spares mentioned in the above annexure . Further, wherever the spares are indicated as a percentage, and result in a number plus fraction, the same shall be converted to the next whole number. In compliance with the requirements of ITB, the prices for mandatory spares must be given separately, and shall be used for bid evaluation purposes. All mandatory spares shall be delivered to site alongwith corresponding main equipment.
2.6.3 Recommended Spares In addition to the mandatory spares, the Contractor shall also provide a list of recommended spares giving unit prices, and total prices for 3 years of normal operation of the equipment, in the relevant schedule of the BPS, This list shall take into consideration the mandatory spares specified in Annexure-GO-VI, and should be a separate list. The Owner reserves the right to buy any, or all the recommended spares. The recommended spares parts shall be delivered to the project site atleast two months before the scheduled date of trial operation of the system.
The list of recommended spares to be furnished by the successful bidder should contain the following :
(i) Population of each item installed alongwith reference drawing number. (ii) Service life expectancy of each item.
(iii) Offer validity period
(iv) Price justification Prices of recommended spares will not be used for evaluation of the bids. The prices of these spares will remain valid for a period of not less than 1 year after the date on which the validity of main Bid expires. Whenever, recommended spares are the same as mandatory spares, then the prices of the mandatory spares and such common recommended spares shall be the same. Further, the prices of any recommended spares, which are not common with mandatory spares listed in this volume, shall be subject to review by the Owner and shall be finalised after mutual discussions.
2.6.4 Start-up Commissioning Spares Start-up commissioning spares are those spares which may be required during the start up and commissioning of the equipment/system. All spares used until the plant is handed over to the Owner shall come under this category. The Contractor shall provide for an adequate stock of such start up commissioning spares to be brought by him to the site for the plant erection and commissioning. They must be available at site before the equipment are energized and the unused spares, if any, should be removed from there only after the issue of taking over certificate. All start up spares which remain unused at that time shall remain the property of the Contractor. The list of commissioning spares to be brought by the Contractor to ensure smooth commissioning of the plant will be subject to Owner’s approval. Contractor shall submit a complete list of all such start up spares. The cost of commissioning spares if any and consumed before the handing over of the plant shall be deemed to have been included in the lumpsum proposal price of the package and the Contractor shall have no claim on this account to the Owner. No mandatory or recommended spares will be used during startup and commissioning of the equipment/plant.
November 3, 2009
2.8.1 Bottom Ash Hopper Discharge Gate
The furnace Bottom Ash Water Impounded Hopper shall be provided with 4 Nos. discharge gates (minimum 900mmX900mm size), one on each opposing slope of each hopper section. Each gate shall be capable of discharging 100% of the contents of one hopper section, within the specified time.
The scope includes necessary drives to open and close the ash gates. Electric drives are not acceptable. In case the drives are air assisted, oil shall be used as medium for movement of gate. The Bidder shall elaborate the features that ensure smooth and guided opening/closing of the gates to limit friction and wear.
Adjustment of the ash gate seal shall be provided preferably from outside the gate housing. As the movement or distortion of the hopper could affect the operation or leak tightness of the ash gates, all ash gates shall be inclined at the same slope as the hopper, and each ash gate and housing should be of integral construction. Gate housing mating flanges shall not be fabricated from more than one piece of material, and manufacturing tolerances on flange surface finish and flatness shall suit the service. Further, the gate housing shall be adequately stiffened to provide the required structural rigidity for preventing the possibility of leakages due to distortion. Thickness of the gate housing shall not be less than 10 mm.
Wear protection liners with a high degree of surface finish shall be provided on the gates and all other sliding surfaces coming in contact with the gate. Wear liner/impingement plates shall be provided on the inside of the gate housing, in the areas of slurry impingement.
The ash gate housing shall include an access door of at least 450 mm diameter, a pressurised air lancing and a poke door, a suitable venting system, ash observation window with electric light and flushing nozzles on either side of the feed gate. The observation window shall be protected from inside by a shield which shall be operable from outside the housing. The ash gate housing sumps shall also be provided with drain and flushing connections with necessary valves.
All joints, door accessories etc. shall be assembled to be completely water tight.
Material of construction shall be as follows:
|Material of Construction||
|Gates||Cast Iron IS:210, Gr.FG-260.|
|Gate wear liners||6 mm thick SS:316|
|Housing wear plates/ Impingement Plates||25 mm thick Cast Iron IS: FG-260219,Gr.|
|Housing||10 mm thick (min) Mild St eel IS:226.|