Tender Document for Construction of Ghorasal 300-450 MW ... - BPDB

Hot Water Distribution System
Hot water shall be distributed to the fill in each cell via a system of headers, laterals,
branch arms, and nozzles installed in the region above the fill and beneath the
drift eliminators. The joint between branch arms and nozzles shall be threaded so
nozzles can be easily removed for cleaning of the branch arms. There shall be a
means of cleanout provided at the ends of all headers and branch arms. Nozzles
shall be heavy duty and not prone to breakage of components.
The water distribution system shall be capable of operating with water quantities
varying between 15% below and 15% above the design water flow per tower cell
or quadrant. The distribution of water to individual nozzles shall be such that the
flow to each nozzle does not deviate from the average flow per nozzle by ±5%.
The distribution system shall include valves for sectionalisation, permitting removal
of each individual tower cell or quadrant from service for inspection, cleaning, or
repair. Isolatable cells shall be designed to accommodate routine online cleaning
and maintenance activities.
The risers and distribution pipe work shall be manufactured from FRP and provided
with adequate supports. Pipe work in each cell shall be identical and provided
with flanges so that sections are interchangeable and can be removed for
maintenance.
Fans, Gear Reducers and Motors
Each fan shall be directly connected to its motor through a totally enclosed, heavy
duty gear reducer and· drive shaft. Fan, gear, shaft bearings, and motor shall be
mounted on a common galvanised and epoxy coated steel base frae, designed
and constructed to prevent misalignment of the drive train and fan. Fan motors
shall not be located in the fan stack or air plenum.
Fans shall be adjustable pitch, manufactured from compression moulded fibreglass
reinforced polyester resin or equivalent, with aerofoil profile. The number of
blades shall not be less than six.
Blade clamp material shall be stainless steel or cast iron with stainless steel bolts
and nuts.
The driveshaft tubes and flanges shall be of AISI 316 L stainless steel or carbon fibre.
Shafts shall be prevented from major displacement by retaining straps just
clear of the shafts.
Gear reducers shall have an oil level sight glass, fill line, vent line, drain line, low
level switch and grease fitting connections all located outside the fan cylinder for
convenient maintenance access. All lines shall be fabricated from AISI 316 L
stainless steel.
Motors shall have easily removable couplings, located outside the fan cylinder.
The drive tube shall be capable of being withdrawn through the fan cylinder for
maintenance.
Two accelerometer type vibration transducers shall be installed on each motor/gearbox/
fan unit. One shall be fitted to the gearbox and the other to the motor.
Both shall be connected to the ICMS.
The cooling tower vibration monitoring equipment shall be Bentley Nevada 1900-
Ghorasal 300-450 MW CCPP Project (Vol-2A of 2) 32