A. B. Hopkins Generating Station
SYSTEM DESCRIPTION
Circulating Water System
Unit No. 2
2-CW-SD
A.B. Hopkins Generating Station
November 1, 1994
Circulating Water System - Unit 2
2-CW-SD
TABLE OF CONTENTS
Section
Page
1.0 INTRODUCTION ...................................................................................................................
1.1
Purpose and Scope ....................................................................................................
1.2
References .................................................................................................................
1.2.1
P&ID ............................................................................................................
1.2.2
Electrical One Line Diagrams .......................................................................
1.2.3
Control Diagrams .........................................................................................
1.2.4
Instrument Loop Diagrams ...........................................................................
1.2.5
Instruction Manuals ......................................................................................
1.2.6
Miscellaneous ..............................................................................................
1.3
System Overview ........................................................................................................
1.3.1
Primary System Flowpath ............................................................................
1.3.2
System Secondary Flowpath(s)/Components ..............................................
1
1
1
1
1
1
1
2
2
3
3
5
2.0 MAJOR COMPONENTS AND SUBSYSTEMS ..................................................................... 7
2.1
Circulating Water Pumps ............................................................................................ 7
2.1.1
Function ....................................................................................................... 7
2.1.2
Detailed Description ..................................................................................... 7
2.1.3
Technical Design Data ................................................................................. 9
2.1.4
Operation, Control, and Safety ..................................................................... 9
2.2
Condenser ................................................................................................................. 11
2.2.1
Function ...................................................................................................... 11
2.2.2
Detailed Description .................................................................................... 11
2.2.3
Technical Design Data ................................................................................ 12
2.2.4
Operation, Control, and Safety .................................................................... 12
2.3
Cooling Towers .......................................................................................................... 14
2.3.1
Function ...................................................................................................... 14
2.3.2
Detailed Description .................................................................................... 14
2.3.3
Technical Design Data ................................................................................ 17
2.3.4
Operation, Control, and Safety .................................................................... 18
3.0 LIST OF INSTRUMENTS AND CONTROLS ........................................................................ 22
Table 1 - Local Indicating Instruments .................................................................................. 22
Table 2 - Control Room Indicating Instruments .................................................................... 24
4.0 LIST OF ALARMS AND SETPOINTS .................................................................................. 25
5.0 LIST OF SYSTEM CONSTRAINTS...................................................................................... 26
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A.B. Hopkins Generating Station
November 1, 1994
Circulating Water System - Unit 2
2-CW-SD
LIST OF ILLUSTRATIONS
Figure
Page
Figure 1.1 - Circulating Water System ............................................................................................. 4
Figure 2.1 - Circulating Water Pump ............................................................................................... 8
Figure 2.2 - Cooling Tower ............................................................................................................ 15
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A.B. Hopkins Generating Station
November 1, 1994
1.0
INTRODUCTION
1.1
Purpose and Scope
Circulating Water System - Unit 2
2-CW-SD
The purpose of the Circulating Water System is to condense the turbine exhaust steam in
the condenser, thus providing a low pressure area for the turbine to exhaust. The condensed
steam is reused as condensate in the Condensate System. The heat absorbed by the circulating
water is dissipated to atmosphere through convection and evaporation in the cooling tower.
1.2
References
1.2.1
a.
Ebasco Services Incorporated, Circulating Water and Condenser Vacuum System,
CTAL-HPK2-M-F-0006, Rev. 0
1.2.2
a.
Revision 0
Control Diagrams
Reynolds, Smith, and Hills, Circ Water Pump 2A, S-5
Reynolds, Smith, and Hills, Circ Water Pump 2B, S-6
Reynolds, Smith, and Hills, Cooling Tower Fan 2A, S-12
Reynolds, Smith, and Hills, Cooling Tower Fan 2B, S-13
Reynolds, Smith, and Hills, Cooling Tower Fan 2C, S-14
Reynolds, Smith, and Hills, Cooling Tower Fan 2D, S-15
Reynolds, Smith, and Hills, Cooling Tower Fan 2E, S-16
Reynolds, Smith, and Hills, Cooling Tower Fan 2F, S-17
Reynolds, Smith, and Hills, Cooling Tower M.O.V 2A, S-117
Reynolds, Smith, and Hills, Cooling Tower M.O.V 2B, S-118
Reynolds, Smith, and Hills, Cooling Tower M.O.V 2C, S-119
Reynolds, Smith, and Hills, Cooling Tower M.O.V 2D, S-120
Reynolds, Smith, and Hills, Cooling Tower M.O.V 2E, S-121
Reynolds, Smith, and Hills, Cooling Tower M.O.V 2F, S-122
1.2.4
a.
b.
c.
d.
e.
Electrical One Line Diagrams
Reynolds, Smith, and Hill, Unit No. 2 Addition, 480 V Unit Substations Single Line and
Arrangement Diagram, E-4, Rev. 0
1.2.3
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
k.
l.
m.
n.
P&ID
Instrument Loop Diagrams
Temperature Control - TG Lube Oil Coolers, Loop 38
Cooling Tower Blowdown Control, Loop 63
Makeup Water Control, Loop 64
Cooling Tower Acid Feed Control, Loop 66
Inhibitor Pump Control, Loop 68
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A.B. Hopkins Generating Station
November 1, 1994
f.
g.
h.
i.
j.
k.
l.
m.
n.
o.
p.
q.
r.
s.
t.
u.
v.
w.
x.
y.
z.
aa.
Cooling Water to Waterbox A, Loop 288
Cooling Water to Waterbox B, Loop 289
Cooling Water from Waterbox A, Loop 290
Cooling Water from Waterbox B, Loop 291
Cooling Tower Fan 2A Load Current, Loop 300
Cooling Tower Fan 2B Load Current, Loop 301
Cooling Tower Fan 2C Load Current, Loop 302
Cooling Tower Fan 2D Load Current, Loop 303
Cooling Tower Fan 2E Load Current, Loop 329
Cooling Tower Fan 2F Load Current, Loop 330
Circulating Water Pump 2A Load Current, Loop 323
Circulating Water Pump 2B Load Current, Loop 324
Circulating Water Pump Discharge, Loop 361
Cooling Tower Fan 2A Motor Control, Loop 400
Cooling Tower Fan 2B Motor Control, Loop 401
Cooling Tower Fan 2C Motor Control, Loop 402
Cooling Tower Fan 2D Motor Control, Loop 403
Circulating Water Pumps Control, Loop 440
Cooling Tower Fan 2E Motor Control, Loop 500
Cooling Tower Fan 2F Motor Control, Loop 501
Cooling Tower Level Alarm, Loop 658
Cooling Tower Return Test Flow, Loop 1242
1.2.5
a.
b.
c.
Revision 0
Instruction Manuals
Babcock and Wilcox, Boiler Operations Manual, Vols. I & II
Hamon Cooling Tower Instruction Manual
Johnston Pump Company, Circulating Water Pump Installation Manual, TH-1130-31
1.2.6
a.
Circulating Water System - Unit 2
2-CW-SD
Miscellaneous
Reynolds, Smith, and Hills, Connection Diagrams, C-1 through C-198
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A.B. Hopkins Generating Station
November 1, 1994
1.3
Circulating Water System - Unit 2
2-CW-SD
System Overview
The Circulating Water System provides cooling water to the main condenser for
condensing the steam turbine exhaust steam. Additionally, the Circulating Water System provides
cooling water to the condensate cooling water heat exchangers, the steam turbine lube oil coolers,
and to the condenser vacuum pumps. The heat absorbed by the circulating water is rejected to
the atmosphere in the cooling tower. The Circulating Water System primary flowpath includes the
following major components:
a.
c.
1.3.1
Circulating Water Pumps
Cooling Tower
Primary System Flowpath
The Circulating Water System, as illustrated in Figure 1.1, is a closed loop type circulating
water system, flow through the system is maintained by two 50% capacity circulating water
pumps. The two circulating water pumps take suction from the cooling tower cold water basin
circulating water sump through individual pump suction screens and discharge into a common
header. The common header supplies circulating water to the main condenser inlet water boxes.
Circulating water flows from the inlet waterboxes through the condenser tubes. Exhaust steam
from the LP turbine passes across the condenser tubes and is condensed. (The condenser shell
and vacuum system are discussed in the Condensate System Description.) Circulating water
inside the condenser tubes then flows through the outlet waterboxes to cooling tower.
Relatively hot circulating water returning from the main condenser is directed to the top of
the cooling tower. The cooling tower riser directs the hot water throughout the cooling tower. The
hot water flows downward through the six individual cells and collects in the cooling tower cold
water basin. As water flows down through the cooling tower, it transfers heat to the air that is
being drawn countercurrent (upward) across the falling water by the cooling tower fans. Relatively
cold circulating water from each cold water basin flows into the common circulating water sump
which provides suction to the circulating water pumps.
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A.B. Hopkins Generating Station
November 1, 1994
Circulating Water System - Unit 2
2-CW-SD
Insert Figure 1.1
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A.B. Hopkins Generating Station
November 1, 1994
1.3.2
Circulating Water System - Unit 2
2-CW-SD
System Secondary Flowpath(s)/Components
The Circulating Water System also contains or interfaces with the following secondary
systems and/or components:
a.
Makeup Circulating Water Supply - To maintain sufficient water level in the cooling
tower cold water basin, makeup water is continuously supplied from the number 3 and
4 well water pumps to makeup for water loss due to evaporation, drift, and blowdown.
The well water pumps take suction from the deep wells and discharge through the
chlorine house and into a common header. The common header supplies makeup
water to cooling tower basin through makeup level control valve 2CWLCV064. The
makeup level control valve modulates to maintain the cooling tower basin level at
setpoint (approximately 6 inches below the top of the basin wall).
b.
Circulating Water Blowdown - During cooling tower operation, water is lost to the
atmosphere due to evaporation. This increases the concentration of salts and other
solids in the water remaining in the cooling tower basin. To control the concentration
of the solids, circulating water is continuously blowndown through the blowdown line,
located on the circulating water pump 2B discharge line. Typically, a water sample is
taken on the outlet of the condenser water box from a drain valve. The water sample
is analyzed for conductivity using a conductivity meter.
The flow of water through the blowdown line is controlled by 2CWFCV063, located on
the southeast side of the cooling tower. Blowdown then gravity flows to the point of
discharge (P.O.D.) and on to the Ochlockonee River. The adjustment of the
blowdown is performed by chemical laboratory personnel and requires no operator
action.
c.
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Auxiliary Cooling Water Supply - The circulating water system provides sufficient
water flow to the steam turbine lube oil coolers, the condenser vacuum system heat
exchangers, and the condensate cooling water heat exchangers. After the water
passes through the various heat exchangers, the auxiliary circulating water supply
combines into a common discharge header. The discharge header combines into the
discharge from the main condenser and flows to the cooling tower with the circulating
water. Additional information regarding the circulating water supply to the turbine
generator lube oil coolers and the condenser vacuum system heat exchangers is
provided in the Main Turbine and Condensate System Descriptions respectively.
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A.B. Hopkins Generating Station
November 1, 1994
d.
Circulating Water System - Unit 2
2-CW-SD
Chemical Injection - The circulating water is tested by the plant laboratory for the
following:
The circulating water conductivity level should be maintained in the range of 950 to
1100 micrmohs. For microbiological control, bottled chlorine gas is injected into the
makeup circulating supply using a feeder system at the chlorine house. For pH
control, both sulfuric and hydrochloric acids are injected using a feeder system at the
cooling tower water flume.
Additionally, a scale inhibitor (HEDP Phosphonate) is
used to control scaling and a copper corrosion inhibitor (Betz CU-1) is used to control
corrosion inside the condenser tubes. The injection amount and intervals are
performed by chemical laboratory personnel and require no operator action.
e.
Electrical Distribution System - The electrical distribution system is used to supply
power and energize all of the circulating water system pumps, fans and slide gates.
The MCCs located throughout the plant feed the system pumps provide the required
protection and starter functions for the motors.
f.
Instrument Air System - Instrument air supplied between 3-27 psig is used as the
medium to operate the system controls, including local controllers, control valves, and
instrumentation.
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A.B. Hopkins Generating Station
November 1, 1994
2.0
MAJOR COMPONENTS AND SUBSYSTEMS
2.1
Circulating Water Pumps
2.1.1
Function
Circulating Water System - Unit 2
2-CW-SD
The Circulating Water Pumps supply cooling water to the surface condenser for
condensing the steam from the steam turbine exhaust. In addition, the circulating water pumps
provide cooling water to the steam turbine lube oil coolers, and the condenser vacuum pump, and
the condensate cooling water heat exchangers.
2.1.2
Detailed Description
Two, 50% capacity, circulating water pumps, arranged in parallel, are located at the
cooling tower. Each circulating water pump, illustrated in figure 2.1, is a vertically mounted
centrifugal, single stage pump manufactured by Johnston Pump Company. The pumps are sized
to provide a capacity of 63,000 gpm at 50 foot discharge head. The pumps take suction from the
circulating water sump, through individual screens.
The Circulating Water Pumps are driven by a 1250 hp, 395 rpm, 4160 VAC electric motor
manufactured by Allis-Chalmer. The motor is coupled to the pump shaft by means of a rigid,
adjustable, flange type coupling which provides for vertical adjustment of the pump shaft.
The pump is equipped with stuffing boxes integral to the pump casing. Seal water is
supplied from the discharge of the pump to each seal assembly. The seal water cools and
lubricates the packing, and prevents premature wear and damage. A slight leakoff should be
allowed to ensure adequate seal water flow to lubricate and cool the packing.
Each circulating water pump is provided with an air eliminator, isolated by a manual valve,
to remove the entrained air from the pump during startup.
A thermocouple is installed in the shell of each pump motor bearing for temperature
monitoring. A thermocouple is a temperature sensing device composed of two dissimilar metals
wires. The wires are welded together at one end to form a measuring junction used to sense
bearing temperature. The junction develops a small dc voltage proportional to the bearing
temperature. The wires from each thermocouple are routed to a terminal block external of the
pump motor. Each thermocouple provides an input signal to the Micromax Data Manager where
the dc voltage is interpreted into a corresponding temperature value.
Each circulating water pump motor is equipped with space heaters. The space heaters
are energized during periods of motor shutdown. The heaters maintain internal temperature
above the dew point; thus, moisture condensation and water accumulation inside the motor is
prevented. Particularly, in moisture laden atmospheres, space heaters reduce the formation of
corrosion and simplify maintenance of the motor windings.
Circulating water pump 2A discharge piping is equipped with a rupture disk to prevent
circulating water piping overpressurization. The rupture disk is isolated by a manually operated
butterfly valve.
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A.B. Hopkins Generating Station
November 1, 1994
Circulating Water System - Unit 2
2-CW-SD
Insert Figure 2.1
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A.B. Hopkins Generating Station
November 1, 1994
2.1.3
Circulating Water System - Unit 2
2-CW-SD
Technical Design Data
Circulating Water Pumps (2A and 2B)
Johnston Pump Company
Pump Manufacture
Vertical,
single stage, open impeller,
Pump Type
centrifugal
50 feet
Total Discharge Head
63,000 gpm
Rated Discharge Flow
Allis-Chalmers
Motor Manufacturer
1250 hp
Motor Horsepower
184 amps
Motor Current
4160 volts
Motor Voltage
395 rpm
Motor Speed
2.1.4
Operation, Control, and Safety
The circulating water system is generally one of the first systems started and one of the
last systems shutdown. The circulating water pump motors are energized from the station 4 KV
switchgear, located in the first floor switchgear room, and are operated and controlled from the
control room. Protective relays are incorporated into the operation of each pump motor feeder
breaker. The relays are preset to trip the breaker in the event of motor overload or detection of a
ground. Each breaker is equipped with the following protective relays:





51-50 relay (phase A)
51-50 relay (phase B)
51-50 relay (phase C)
51-50 ground relay
86 Lockout relay
Each feeder breaker is equipped with pistol grip, TRIP/CLOSE control switch, an ammeter
and associated four position (OFF/1/2/3) control switch, and a hour meter. Green and red
indicating lights are installed above the breaker control switch to provide the Operator with
indication of breaker position. In the TRIP position, the breaker control switch can be locked out of
service by turning the lockout relay control switch to the LOCKOUT position. When locked out of
service, both breaker indicating lights are extinguished. Current flow through each phase of the
breaker can be monitored at the ammeter by placing the ammeter control switch in the respective
position.
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A.B. Hopkins Generating Station
November 1, 1994
Circulating Water System - Unit 2
2-CW-SD
The starting current to the circulating water pump motors is three to five times the full load
current. This heavy current causes increased magnetic forces on the stator coils and heating of
the rotor cage and stator winding. Starting limits must be followed to prevent any damage to the
motor windings. With the motor cold, no more than two consecutive starts must be attempted.
The motor must be allowed to coast to a complete stop between starts. With the motor hot, no
more that 1 start must be attempted within 30 minutes of shutdown. If the hot-start attempt fails, a
period of no less than 60 minutes must elapse before a second start may be attempted.
The operation of each pump is monitored and controlled in the Control Room through
individual Stop/Normal/Start pump control switches. Indicating lights are located above each
control switch to indicate pump status. A red light indicates the pump is operating, a green light
indicates the pump is secured, an amber light indicates the pump is in auto, and a white light will
indicate a motor trip condition. Above the indicating lights on the BTG Board is a remote motor
load indicator (2CWIIB323/4) for each of the circulating water pump motors.
The operation of each circulating water pump is performed by the operator and no safety
interlocks are provided other than motor overcurrent protection. Before a pump can be started,
the manual inlet valves to the waterboxes must be two turns open and the steam turbine lube oil
coolers, condenser vacuum system heat exchangers, and condensate cooling water heat
exchangers manual inlet valves must be closed to prevent possible water hammer damage. In
addition, the manual isolation valve for the rupture disk must be closed until the circulating system
is filled and vented. Each circulating water pump is started by placing the control room individual
control switch in the START position. Prior to opening the waterbox inlet valves the motor
amperage, as indicated on the gauge above the control switch, must fall below 184 amps. After
the circulating return flow to the cooling tower is established the manual inlet valves to the various
auxiliary heat exchangers can be opened as required. Once return flow to the cooling tower is
established and verified, the manual isolation valve for the system rupture disk is opened to
protect the system from overpressurization.
During unit startup, one circulating water pump is placed in service. Once the unit is up to
startup load, the second circulating water pump is placed in service. The point at which the
second circulating pump is placed in service is dependant on the turbine back pressure and the
ambient air temperature. At least one circulating pump should remain in service as long as turbine
exhaust steam is entering the condenser. If only one circulating water pump can be used the
turbine load must be reduced to allow all of the entering steam to be condensed and the proper
turbine back pressure maintained.
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A.B. Hopkins Generating Station
November 1, 1994
2.2
Condenser
2.2.1
Function
Circulating Water System - Unit 2
2-CW-SD
The function of the condenser is to decrease the backpressure against which the steam
turbine must operate, thereby permitting full utilization of available steam energy at the lowest
absolute pressure. The condenser functions as a heat sink, under vacuum, to condense the
turbine exhaust steam for reuse in the Condensate System. The condenser also serves as a
centralized point of collection for condensate drains and vents of various plant equipment. The
Circulating Water System supplies the water to be used to remove the heat.
2.2.2
Detailed Description
The main condenser is located directly beneath the low pressure turbines. The inlet and
outlet waterboxes are located on the first floor and are vertically divided into two sides. The
condenser is attached to the steam turbine by a flexible expansion joint. The condenser is a shell
and tube type of heat exchanger which transfers heat from the steam turbine exhaust to the
circulating water system. The driving force for this heat transfer is the difference in temperature,
or thermal energy levels, of the two fluids. The greater the temperature, or energy level,
difference the faster the heat transfer, or energy exchange. The heat transfer is enhanced by the
large surface area of the condensers tubes.
The condenser tubes are arranged in a two pass, divided flow arrangement. Tube sheets
installed on the inlet and outlet waterboxes separate the tube side and steam side of the main
condenser. The circulating water is designed to flow through the main condenser at approximately
121,000 gpm during base load conditions. The condenser is equipped with 15,744 parallel tubes
extending across the condenser from the inlet waterbox to the outlet waterbox. The tubes are
supported by equally spaced support tube plates. The 90/10 Copper Nickel alloy tubes are 32'8.375" long and 1.0" in diameter. The tubes provide a cooling surface area of 129,670 square
feet.
Each condenser waterbox is equipped with a vent line to remove air from the waterbox.
Each vent line is equipped with a manual valve which is opened during startup to vent the
waterbox while filling the condenser tubes with circulating water. The condenser waterboxes are
also equipped with various sample lines used by the laboratory to test the circulating water quality.
The shell side of the condenser is equipped with a pneumatically operated vacuum
breaker (2AEPV482), that allows the condenser shell to be brought back to atmospheric pressure.
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A.B. Hopkins Generating Station
November 1, 1994
2.2.3
Circulating Water System - Unit 2
2-CW-SD
Technical Design Data
Main Surface Condenser
Manufacturer
Cooling Surface Area
Number of Water Passes
Capacity
Cooling Water Supply
Cooling Water Inlet Temperature
Tube Material
Number of Tubes
Tube Length
Tube Diameter
Tube Wall Thickness
2.2.4
Westinghouse
129,670
2
1,048,384 lb/hr (steam condensed)
121,000 gpm
86F
90/10 CuNi Alloy 760
15,244
32 ft. 8.375 in.
1.0 inch O.D.
20 BWG
Operation, Control, and Safety
Operation of the main condenser tube side is controlled by the flow of circulating water
through the condenser tubes. At least one circulating water pump must be in service prior to
placing one side of the condenser in service. The main condenser waterboxes should be vented
during system startup by opening the vent line manual valves.
The condenser is placed into operation by starting the circulating water pumps and
opening the circulating water inlet and outlet valves. Circulating water enters the condenser
through the inlet waterboxes, flows through the condenser tubes, and exits through the outlet
waterboxes combining back into a common header. Circulating water removes the heat of
evaporation from the turbine exhaust steam. The steam condenses at the tubes and falls to the
bottom of the hotwell. The warm circulating water exits the waterboxes and flows back to the
cooling tower.
When the main condenser is removed from service, the condenser tube side remains in
service until the condenser vacuum has been decreased to atmospheric conditions and the
Turbine Gland Steam System has been secured. The circulating water pumps are then removed
from service to stop circulating water flow through the main condenser tubes.
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A.B. Hopkins Generating Station
November 1, 1994
Circulating Water System - Unit 2
2-CW-SD
Four thermocouples (2CWTE1231/2/3/4) are installed in the circulating water headers at
the inlet and outlet (2 each) of the condenser. Each thermocouple provides an input signal to the
Micromax Data Management System, and to the remote indicators located in the control room.
Pressure transmitters (2CWPT280/1/2/3) provide input signals to the remote pressure indicators
located in the control room. The signals provided by the thermocouples and transmitters, in
conjunction with local pressure (2CWPI116/7/8/9) and temperature indicators (2CWTI065/6/7/8),
provide a method of monitoring condenser performance.
The thermocouples also provide signals that will initiate the following alarms in the control
room:




Revision 0
"Waterbox A Inlet Temp High" at 115 F.
"Waterbox B Inlet Temp High" at 115 F.
"Waterbox A Outlet Temp High" at 135 F.
"Waterbox B Outlet Temp High" at 135 F.
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A.B. Hopkins Generating Station
November 1, 1994
2.3
Cooling Towers
2.3.1
Function
Circulating Water System - Unit 2
2-CW-SD
The function of the cooling tower is to cool the circulating water used as a cooling medium
in the surface condenser and the other auxiliary heat exchangers in the generating station.
2.3.2
Detailed Description
The cooling tower, illustrated in Figure 2.2, is located outside, to the west of the generating
station main building . The cooling tower, manufactured by Hamon (Research Cortell), is a
mechanical induced draft, cross flow type cooling tower. The tower is designed according to the
counterflow principle and incorporates asbestos'-cement heat transfer surface to assure maximum
availability for year-round operation, to minimize maintenance, and to virtually eliminate any
necessity for replacement of parts or material.
The tower consists essentially of the following six major parts:






Basin
Warm Water Inlet and Distribution
Fill
Drift Eliminators
Structure/Enclosure
Mechanical Equipment
Basin
The cold water basin, which is under the entire base of the tower, is 382 feet long by 71.2
feet wide and contains approximately 1,080,000 gallons of water when filled to the operating level,
approximately six inches from the top of the basin wall. The water basin feeds the water to the
circulating water sump and then to the pump suction screens.
Warm Water Inlet and Distribution
Warm water enters the tower from the condenser outlet through a concrete pipe. This
concrete pipe supplies water to six risers or one per cell, which, in turn, supply the concrete
distribution flumes above the fill level.
Each flume is fitted with asbestos cement distribution pipes which distribute the warm
water evenly to all sections of the tower fill. Each segment of pipe is fitted with evenly spaced
plastic nozzles which in turn are fitted with splash plates that cause the water to be uniformly
distributed over a wide area of fill.
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A.B. Hopkins Generating Station
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Circulating Water System - Unit 2
2-CW-SD
Figure 2.2
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A.B. Hopkins Generating Station
November 1, 1994
Circulating Water System - Unit 2
2-CW-SD
Fill
The fill consists of a variable number of tiers of asbestos-cement sheets. These sheets
are supported from prestressed concrete beams, with uniform spacing between the sheets maintained by plastic spacers and struts. The water leaving the splash plates falls onto the fill sheets
where it runs down the sheets to the cold water basin below. The falling water is opposed by the
induced air flow through the fill, and air/water contact is established.
Drift Eliminators
Immediately above the distribution piping network are the drift eliminator waves which are
supported by the concrete structure. The drift eliminators reduce moisture entrained in the air
from leaving the tower as drift.
Structure/Enclosure
The tower structure and enclosure consists of concrete and asbestos-cement
components. Cast-in-place concrete columns support a combination of precast and cast-in-place
beams. These beams carry the internals of the tower, support the fan stack and diffuser, and
brace the asbestos-cement panels used as siding. The manner of casting the beams in the
columns, results in a monolithic connection, requiring no future maintenance attention.
To facilitate inspection of the tower components the tower is equipped with an access
system. A walkway and stairway are provided on the north side of the tower. Access is provided
to each cell through a door at the drift eliminator level. A ladder is provided on each warm water
riser to provide for inspection of the remaining equipment.
For storm electrical shock protection the cooling tower structure is provided with a lighting
protection system.
Mechanical Equipment
Each cooling tower cell consists of the following mechanical equipment:




Fan
Reduction Gear
Motor
Cell Slide Gates (MOVs)
The cooling tower fans are axial flow type, specifically made for cooling tower service, are
manufactured by Hudson Products. Each fan consists of eight glass reinforced epoxy resin
blades held by a galvanized steel hub. The 40 foot diameter fans are mounted on top of the
output shafts of the gear reducers.
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A.B. Hopkins Generating Station
November 1, 1994
Circulating Water System - Unit 2
2-CW-SD
Each reduction gear reducer is manufactured by Nutall, and is a double reduction type.
The reduction gear is a parallel shaft, mechanically lubricated type with a speed reduction ratio of
1785/88 rpm.
The reduction gear is directly connected by a flexible, non-lubricated coupling to an
electric drive motor. The 200 horsepower totally enclosed fan cooled motor, manufactured by Allis
Chalmers, is centrally located inside of each cell.
The motor and gear reducer are mounted to a structural steel frame. This frame is
anchored on top of the cast-in-place riser, which provides a massive and rigid support, which
serves to dampen any vibrations generated by the operation of the equipment.
Each cell can be isolated for maintenance by the two motor operated slide gates, or
MOVs, provided for each cell. Two 24" x 41" Coldwell Wilcox slide gates are driven by two 6 to 1
worm gear boxes driven by a common electric operator. The electric operator is Rotork 14A
Syncropak type of actuator. The slide gates isolate each side of the hot water flume for the
specific cell.
2.3.3
Technical Design Data
Manufacturer
Cooling Tower Type
Heat Exchange Direction
Number of Cells
Circulating Water Capacity
Cooling Tower
Hamon Cooling Tower Division
Counterflow
Vertical
6
127,000 gpm
Cooling Tower Fans
Manufacturer
Size
Model
Blade Type
Number of Blades
Speed
Revision 0
Hudson Products
40 Ft. diameter
APT-40B-8
Glass Reinforced Epoxy Resin
8
88 rpm
Page 17
A.B. Hopkins Generating Station
November 1, 1994
Circulating Water System - Unit 2
2-CW-SD
Cooling Tower Fan Motor
Manufacturer
Electrical Supply
Horsepower
Allis Chalmers
4KV / 3 phase
200
Cooling Tower Fan Reduction Gear
Manufacturer
Nutall
Type
Double Reduction
Speed Ratio
1785:88
Cooling Tower Slide Gate
Manufacturer
Size
Number Per Cell
Electric Operator Manufacturer
Electric Operator Model
Electric Supply
Gear Box Type
2.3.4
Coldwell Wilcox
24" x 41"
2
Rotork
14A Syncropak
480 VAC/3 phase/60 Hz
6 to 1 worm gear
Operation, Control, and Safety
Principle of Operation
The transfer of heat from the circulating water to atmosphere is accomplished in the
cooling tower fill by passing the relatively warm circulating water over thin sheets, through a
stream of moving air. The object of the cooling tower design is to achieve a maximum area of
contact between the water surface and air. This is accomplished by flowing a very thin film of
water down the sides of hundreds of thousands of asbestos-cement sheets that provide for
maximum contact with the rising air through the sheet spacing.
Revision 0
Page 18
A.B. Hopkins Generating Station
November 1, 1994
Circulating Water System - Unit 2
2-CW-SD
Heat transfer from the warm water is accomplished primarily through evaporation, which
makes it possible to cool the water below the atmospheric dry bulb temperature. In evaporating
one pound of water approximately 1,000 BTU's are transferred from the water into the air.
Additional heat is also transferred to the air due to the temperature difference between the water
and the air.
The warm moist air is then drawn through the drift eliminators by the cell fans. The drift
eliminators cause the air to abruptly change direction, thus removing the entrained water droplets.
After the entrained moisture is removed from the air in the drift eliminators the fan discharges the
slightly moist air to atmosphere.
The cooling tower is operated and controlled based on unit load, ambient temperature,
humidity, and condition of the cooling tower equipment. The cooling tower is controlled by
operating the cooling tower fans, maintaining basin level, and operating the cell slide gates.
Cooling Tower Fan Control
The cooling tower fan motors are energized from the station 4160 VAC loadcenters and
operated and controlled from the control room. Protective relays are incorporated into the
operation of each pump motor feeder breaker. The relays are preset to trip the breaker in the
event of motor overload or detection of a ground. Each breaker is equipped with the following
protective relays:





51-50 relay (phase A)
51-50 relay (phase B)
51-50 relay (phase C)
51-50 ground relay
86 Lockout relay
Each feeder breaker is equipped with pistol grip, TRIP/CLOSE control switch, an ammeter
and associated four position (OFF/1/2/3) control switch, and a hour meter. Green and red
indicating lights are installed above the breaker control switch to provide the Operator with
indication of breaker position. In the TRIP position, the breaker control switch can be locked out of
service by turning the lockout relay control switch to the LOCKOUT position. When locked out of
service, both breaker indicating lights are extinguished. Current flow through each phase of the
breaker can be monitored at the ammeter by placing the ammeter control switch in the respective
position.
The starting current to the cooling tower fan motors is three to five times the full load
current. This heavy current causes increased magnetic forces on the stator coils and heating of
the rotor cage and stator winding. Starting limits must be followed to prevent any damage to the
motor windings. With the motor cold, no more than two consecutive starts must be attempted.
The motor must be allowed to coast to a complete stop between starts. With the motor hot, no
more that 1 start must be attempted within 30 minutes of shutdown. If the hot-start attempt fails, a
period of no less than 60 minutes must elapse before a second start may be attempted.
Revision 0
Page 19
A.B. Hopkins Generating Station
November 1, 1994
Circulating Water System - Unit 2
2-CW-SD
The operation of each cooling tower fan is monitored and controlled in the Control Room
through individual Stop/Normal/Start control switches. Indicating lights are located above each
control switch to indicate cooling tower fan status. A red light indicates the cooling tower fan is
operating, a green light indicates the cooling tower fan is secured, an amber light indicates the
cooling tower fan is in standby, and a white light will indicate a motor trip condition. Above the
indicating lights on the BTG Board is a remote motor load indicator for the cooling tower fan main
drive motor.
The cooling tower fans are operated in conjunction with the Circulating Water Pumps in
order to maintain condenser vacuum at approximately 28" Hg and a design cooling water
temperature of 86F. To maintain the proper condenser vacuum it may be required to produce a
lower circulating water temperature. The cooling tower fans and circulating water pumps are
operated to meet these "ideal conditions" which are influenced by ambient conditions. For
example, if two circulating water pumps and all six cells on the cooling tower were in service with a
rise in circulating water temperature, the condenser backpressure would also begin to rise due to
the lack of cooling ability. At this point, an additional fan would be started in order to meet the
backpressure and water temperature criteria.
The operation of each cooling tower fan is performed by the operator and no safety
interlocks are provided other than motor overcurrent protection. Each cooling tower fan is started
by placing it's control switch in the START position. Typically, each fan is started and remains
running until it is no longer required for operation.
Cooling Tower Level Control
The cooling tower cold water basin level is automatically controlled. A level transmitter
(2CWLT064) located in the cooling tower basin sends a signal to a level controller (2CWLIC064)
which in turn sends a pneumatic signal to the makeup level control valve (2CWLCV064) to
maintain the level at 6" below the top of the cold water basin. The cooling tower cold water basin
level can be observed on a remote level indicator (2CWLIB064) located in the control room, which
is also fed its signal by the basin level transmitter (2CWLT064).
Sufficient water level must be maintained in the cooling tower cold water basin and the
circulating water sump to prevent pump cavitation or loss of pump suction. Level switch
(2CWLSL658) is installed in the circulating water sump to detect low water level. If the water level
decreases to +74", the level switch initiates a "Cooling Tower Basin Level Low" alarm to the
control room warning the Operator of the condition. When the level increases to +80", level switch
(2CWLSH658) initiates a "Cooling Tower Basin Level High" alarm to the control room warning the
Operator of the condition. No trips are associated with the alarms.
Each cooling tower is equipped with manually operated blowdown stations. The amount
of blowdown depends on the amount of total dissolved solids in the circulating water. Typically, a
water sample is taken on the outlet of the condenser water box from a drain valve. The water
sample is analyzed for conductivity using a conductivity meter. The desired level of
Revision 0
Page 20
A.B. Hopkins Generating Station
November 1, 1994
Circulating Water System - Unit 2
2-CW-SD
total dissolved solids (TDS) is between 200 - 700 ppm. The length of the blowdown varies based
on the amount of total dissolved solids. Other chemical conditions are tested for and corrected for
by the chemical laboratory. These include the following:










Parameter
Normal Range
pH
Conductivity
Hardness (CaCO3 and Total)
P and M Alkalinity
Phosphates
Tolytriazole
Silica
Sulfates
Chlorine
Copper
50 - 100 ppm
8.0 - 8.3 S.U.
900 - 1100 mmho
360 - 400 ppm
4 - 6 ppm and 100 -120 ppm
1.5 - 1.7 ppm
n/a
25 - 30 ppm
100 -125 ppm
n/a
Cooling Tower Cell Slide Gate Control
The cooling tower slide gates 2A through 2F are energized by 480 VAC feeder breakers
located on MCC 2-9. Each breaker is equipped with a ON-OFF switch which opens and closes
the breaker at the MCC.
At the cooling tower cells, each slide gate is provided with its own OPEN STOP CLOSE
push buttons. Green and red indicating lights are provided to give slide gate operational status to
the local operator.
The normal operation of each cooling tower slide gate is monitored and controlled in the
Control Room through individual Open/Stop/Close control switches. Each slide gate is manually
operated and has no automatic operation capabilities. Indicating lights are provided in the control
room for each slide gate a red light indicates the gate is closing or closed, a green light indicates
the gate is opening or opened.
Revision 0
Page 21
A.B. Hopkins Generating Station
November 1, 1994
3.0
Circulating Water System - Unit 2
2-CW-SD
LIST OF INSTRUMENTS AND CONTROLS
Instrument
2CWTI068
2CWPI118
2CWPI116
2CWTI066
2CWTI065
2CWPI119
2CWPI117
2CWTI067
n/a
n/a
2CWTI096
2CWPI166
2CWPI164
2CWTI098
2CWTI097
2CWPI167
2CWPI165
2CWTI099
2CWTI101
2CWPI164
2CWPI172
2CWTI103
2CWTI101
2CWPI164
2CWPI172
2CWTI103
2CWTI079
2CWPI143
2CWTI177
2CWTI080
2CWPI141
2CWTI078
Revision 0
Table 1 - Local Indicating Instruments
Function/Description
Waterbox 2A Inlet Temperature
Waterbox 2A Inlet Pressure
Waterbox 2A Outlet Pressure
Waterbox 2A Outlet Temperature
Waterbox 2B Inlet Temperature
Waterbox 2B Inlet Pressure
Waterbox 2B Outlet Pressure
Waterbox 2B Outlet Temperature
Waterbox 2A Level
Waterbox 2B Level
Vacuum Cooler 2A Inlet Temperature
Vacuum Cooler 2A Inlet Pressure
Vacuum Cooler 2A Outlet Pressure
Vacuum Cooler 2A Outlet Temp
Vacuum Cooler 2B Inlet Temperature
Vacuum Cooler 2B Inlet Pressure
Vacuum Cooler 2B Outlet Pressure
Vacuum Cooler 2B Outlet Temp
Turb Gen L/O Cooler 2A Inlet Temp
Turb Gen L/O Cooler 2A Inlet Press
Turb Gen L/O Cooler 2A Outlet Press
Turb Gen L/O Cooler 2A Outlet Temp
Turb Gen L/O Cooler 2B Inlet Temp
Turb Gen L/O Cooler 2B Inlet Press
Turb Gen L/O Cooler 2B Outlet Press
Turb Gen L/O Cooler 2B Outlet Temp
C.C. Water Cooler 2A Inlet Temp
C.C. Water Cooler 2A Inlet Press
C.C. Water Cooler 2A Outlet Temp
C.C. Water Cooler 2B Inlet Temp
C.C. Water Cooler 2B Inlet Press
C.C. Water Cooler 2B Outlet Temp
Normal Range
70 - 90 oF
15 - 20 psig
10 -15 psig
80- -100 oF
70 - 90 oF
15 - 20 psig
10 -15 psig
80- -100 oF
middle
middle
70 - 90 oF
15 - 20 psig
10 -15 psig
80- -100 oF
70 - 90 oF
15 - 20 psig
10 -15 psig
80- -100 oF
70 - 90 oF
15 - 20 psig
10 -15 psig
80- -100 oF
70 - 90 oF
15 - 20 psig
10 -15 psig
80- -100 oF
70 - 90 oF
15 - 20 psig
80- -100 oF
70 - 90 oF
15 - 20 psig
80- -100 oF
Page 22
A.B. Hopkins Generating Station
November 1, 1994
Instrument
2CWLT064
2CWFT064
2CWTE1232
2CWPT282
2CWPT280
2CWTE1233
2CWTE1234
2CWPT281
2CWPT283
2CWTE1231
2CWTE1338
2CWTE1339
2CWIIB323
2CWIIB324
2CWIIB300
2CWIIB301
2CWIIB302
2CWIIB303
2CWIIB329
2CWIIB330
Revision 0
Circulating Water System - Unit 2
2-CW-SD
Table 2 - Control Room Indicating Instruments
Function/Description
Normal Range
Cooling Tower Level
+75" to +79"
Circulating Water Blowdown Flow
800 - 1000 gpm
Waterbox 2A Inlet Temperature
70 - 90 F
Waterbox 2A Inlet Pressure
15 - 20 psig
Waterbox 2A Outlet Pressure
10 - 15 psig
Waterbox 2A Outlet Temperature
80 -100 F
Waterbox 2B Inlet Temperature
70 - 90 F
Waterbox 2B Inlet Pressure
15 - 20 psig
Waterbox 2B Outlet Pressure
10 - 15 psig
Waterbox 2B Outlet Temperature
80 -100 F
Vacuum Cooler 2A Outlet Temp
80 - 100 F
Vacuum Cooler 2B Outlet Temp
80 - 100 F
Circ Water Motor 2A Motor Load
<184 Amps
Circ Water Motor 2B Motor Load
<184 Amps
CT Fan Motor 2A Motor Load
<26.3 Amps
CT Fan Motor 2B Motor Load
<26.3 Amps
CT Fan Motor 2C Motor Load
<26.3 Amps
CT Fan Motor 2D Motor Load
<26.3 Amps
CT Fan Motor 2E Motor Load
<26.3 Amps
CT Fan Motor 2F Motor Load
<26.3 Amps
Page 23
A.B. Hopkins Generating Station
November 1, 1994
4.0
Circulating Water System - Unit 2
2-CW-SD
LIST OF ALARMS AND SETPOINTS
ALARM CONDITIONS
Alarms
Waterbox A Inlet Temp High
Waterbox B Inlet Temp High
Waterbox A Outlet Temp High
Waterbox B Outlet Temp High
Cooling Tower Basin Level High Alarm
Cooling Tower Basin Level Low Alarm
Motor Overtemperature
Revision 0
Initiating
Device(s)
TE-1232
TE-1234
TE-1233
TE-1231
LSH-658
LSL-658
Micromax
Device
Setpoint(s)
115 oF
115 oF
135 oF
135 oF
+80"
+74"
155F
Page 24
A.B. Hopkins Generating Station
November 1, 1994
5.0
Circulating Water System - Unit 2
2-CW-SD
LIST OF SYSTEM CONSTRAINTS
The following constraints listed are system specific operational considerations that must
be closely followed. Failure to recognize these constraints may result in personnel injury or
equipment damage:

Cooling Tower level should be maintained as close to 6" below the top of the cold water
basin as possible, as indicated on 2CWLIB064.

Circulating Water Pumps should maintain the discharge to the condenser and auxiliary
coolers at 15 - 20 psig, as indicated on the local and remote pressure indicators.

The condenser back pressure should be maintained between 1 and 3" Hg absolute, with a
condenser vacuum of 28".

The circulating water system should maintain the condenser inlet circulating water at the
design temperature of 86 F, unless ambient conditions warrant lower temperature to
maintain the turbine exhaust back pressure.

Circulating Water Pump motor loads should not exceed 184 amperes, as indicated on the
remote load indicators.

Cooling Tower Fan motor loads should not exceed 26.3 amperes, as indicated on the
remote load indicators.
Revision 0
Page 25