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COOLING TOW RS
SECTION
OPERATION ND CONSTRUCTION
There a e exhibits placed
in
the center of
Ihe
book that
will be
referred
to later in the program. The J should
be
removed
and
set aside now
so
Ihal they
will be
handy
when needed.
1.
A refinery uses
as much as
25 barrels of
water
for every
barrel
of crude processed.
A 200,OOO·bal l ei-a-day refinery
mi
g
ht
use as much as
barrels of water.
. 2. Of all
the water
used
by
a refinery, 80
to
90 is used
as
cool-
•
ant to absorb energy.
3. Look
at
tn15
heat
exchanger.
HOT
COOL
~ L I Q U I D
As the liquid travels through the pipe, the heat from the
liquid is exchanged or transferred
to
the _ _
4. eat always travels from areas of higher
te
mperature
to
·areas
of (higher/ lower) temperature.
5 , Water can absorb only so much heat.
As water becomes hotter, its effectiveness as a coolant (in
creases/ d ocreases).
6. After a
while,
the temperature
of
water
becomes so hillh
that
it
can no
longer absorb from
the hot
liquid .
7.
The
water in
this
h
eat
exchanger works
as
a coolant only as
long as it is
than the
liquid being cooled.
8. Maximum cooling IS achieved by constantly
replacing
hot
water
with
water.
1
•
5,000,000
heat
water
lower
decreases
heat
cooler
coo1
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9. In order
to
provide for further cooling, two things are possible.
First,
the
hot
cooling water can be discharged and
with fresh water.
Or, the hot
cooling water can he and reused
or further cooling.
he amount o water needed for cooling in a large refinery is
in
the
range of tho.usands/millions) of barrels per day.
of barrels
o
water per
day from
the water
supply would
be
extremely
The amount
of
water needed
is
so large
th t
many water sup-
plies would /would not) be able
to
provide enough.
A refinery
must
be careful about the qu lity of
the
water
it
discharges.
Discharging millions
of
barrels
of
hot water per day might
cause a problem.
. Cooling
the
hot water enables
the
refinery
to
water over and over again.
The liest way to handle hot water
is
to discharge it / cool and
reuse
it .
. Hot water is cooled for reuse in special cooling
OF HE T
TR NSFER
Suppose
a
steel
rod
is heated
t
one end.
c
The entire rod heats up evenly./Section gets
hot
first.)
19.
AJ
s ~ t o n
A becomes hot,
it
acquires thermal, or
energy.
•
20. Thermal, or heat, energy always travels from higher
to
temperature regions.
2
replacE'(t
cooled
millions
c o ~ t l y or expE'nsive
would not
pollution
reuse
cool and reuse it
tower :::
,
Section gets hot first.
he t
lower
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21
s
one seetion
of
the steel rod beeomes hot,
the
rod (conducts/
does not
conduct) the
heat
to the colder sections.
22 In this example, the heat
tran
sfer from section A to C (occurs/
does not occur) by conduction.
3 . Conduction occurs when heat or thermal energy flows
through a
substance
from a
to a
temperature region.
24 Suppose a hot baT of steel is placed in contact with a cold one.
COLO
BAR
HOT BAR
B
POINT OF CONTACT
A
The. heat energy from baT A (will transfer/will not transfer)
to
baT B
25 The cold bar becomes hot first
at
the point
of
_ _
26
. Then,
the heat
is transferred through the bar by
27 Another method
of heat
transfer is convection.
WATER
rn BURNER
The burner heats the water in the vessel (all at once/at
the
bottom only).
28
. As the water at the bottom of the container gets hot, it be-
comes less dense. .
A volume of hot water weighs (more/ less)
than
the same
volume of cold water.
29
s
the
water
at
the
bottom of the vessel gets hot,
it
will
(float
to the top/
stay at
the bottom).
30 In this case, heat
is
carried to other parts of the vessel by
conduction / physical movement .
3
conducts
occurs
higher; lower
will transfer
contact
conduction
'
at
the bottom only
less
fioat to the top
physical movement
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31. Convection
is
the transfer of thermal or heat energy by actual
within a 5ubstance.
3
.
Heat
transfer also occurs in another way.
f you bring your hand
near any
hot object you
f l
/
do
not
feel) the heat from it.
33. Usually solids liquids
or
gases have a high enough tempera-
ture
to
emit
radiate
energy.
34. This method of heat transfer or flow
is
called convection /
radiation).
Review
35. There are three methods of heat transfer:
r d
iation conduc-
tion and
36. Heat flowing within a substa:lce
from
a higher temperature
region
to
a lower temperature region is heing transferred
by
37. This shows a flame heating the bottom opening
of
, duct.
~
OLD
AIR
Ai;
it enters
the
cold air absorbs thermal ener
gy
and
e c o m ~
88. As the air becomes hot
it
rises and leaves
th
e duct taking
its
energy with it.
39. The method of heat traMler
by
physical movement is calleu
4
physical movement
feel
hent
or
thennal
radiati on
.
.
convection
conduction
hot
heat, or thennal
convection
•
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HOW COOLING
TOWERS
COOL W TER
Result,
f
Evaporation
•
;-. 40. S o r r ~ Conn of energy is required for any movement or change
in matter.
o boil water) a source of _______ energy is needed.
41.
The
molecules in any body
of
water move
due to
the
heat
_______ in them.
42.
The
speed of the molecules depends upon the
amount
of
heat
energy in them.
The
more heat, the the
molecules
move
.
43.
In
any body of wat
er
some molecules move faster than others.
/
/
The
molecules which move faster have (more/ less) heat
energy.
44. Some molecules
moYe
fa st enough to break away from the
body
of water and mix with the air.
The molecules
that
break away first have a (higher/lower)
amount of heat energy.
45.
As
the
molecules leave the body of water,
_______
energy with them.
they take their
46. The
,
olecules that remain have a lower level of heat energy.
With a lower level of energy, these molecules move (slower.
faster
.
47. In order for them to escape from the body of water, the slow-
moving molecules have to in speed.
48. Adding heat energy
to
the molecules will cause them to move
?nce moving fast enough, the molecules will es;ap:. ·;hi;
IS
evaporahon
_
. ._- . _
After partial evaporation, a body of water (is cooler/ stays the
same).
5O I ;Cooling towers are designed to expose hot water to the air.
This
(a
llows/ does not allow) partial evaporation of the wate r.
51. This partial evaporation (cools/does not cool) the water.
hat Affects Evaporation
52. In order for water to evaporate, it (needs/ does not need )
to
be in contact with air.
53. The larger the surface in contact
wi
th air, the (more/1ess)
molecul
es
can leave a body of water at a given time.
5
•
heat
energy
•
faster
more
higher
heat
slower
increase
faster
is cooler
allows
cools
needs
more
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\ :
54. The
more
water molecules that leave a body
or
water at a
given time, the (faster/ slowe, ) the rate of evaporation.
55. These two basins contain the same amount of \vater.
A
8
The rate of evapOl ation is faster from basin A / B).
56.
The
faste, the
rate
of evaporation from a body of water, the
(fasteri slower) the body of water will cool.
57. Cooling towe S are designed to provide the
hot
water with a
_ surlaceato-air contact.
58 .
The hotter
the water, the more (fast / slow) -moving molecul.s
in it.
59. Hot water will evaporate than cold
lVater.
.
Atmospheric pressure exerts /does not exert) pressure
on
a
body of water.
61, Atmospheric pressure (resists / does
not
resist) the molecules
escaping from a body of water.
62. It is easier
for
water molecules to leave a body of water at
(high / low) atmospheric pressures.
63. As
air
acquires moisture water molecules), its humidity
64
.
Air can hold only a certain
amount
of
water molecules.
f
it
becomes water saturated it will no longer
water molecules.
/ 65 .
The
higher the humidity of th e air in
contact
with the water,
the the rate or evaporation.
eview
•
66. Hot
water evaporates
at
a (higher/ lower)
rat
e than cold water.
/ 67 . Which
of
the following affect the
rate
of water evaporation:
a) humidity of the air
b) surface
of
contact
e t w e ~ n
water and
air
c) the temperature of the water
6
faster
B
faster
large
fast
faster
exerts
resist '
low
rises, or increases
slower
higher
n;b;c
·t· . : ,:
: '
'
' , .
.
;. ,
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CONSTRUCTION OF COOLING
TOWERS
68. In the early days
of
continuous processing, no attempt was
made to
cool
process water. Water that was cool already was
taken into the plant from the outside, then discarded when hot.
/
When a plant was located near a river or stream, the cool water
was taken into the plant upstream and released
69. When a plant was
not
located near a river, the water was taken
from a pond. Hot process water was returned to the pond
surface and cooled by surface exposure to the
70. The open pond
coo
ling system was eventually modified.
HEAT EXCHANGER
COOL
WATER
SPRAY POND COO LING SYSTEM
In this system, hot cooling water is over the
pond surface.
71.
By spraying
the
hot water, more water-to-
surface contact is reached.
72. With a larger water-te-air surface contact. the rate of evapora
tion increases/ decreases).
~ 7 3 .
However, wind could blow away the sprayed water, resulting
in water and damage to
nearqy
structures.
,
.
74.
The
spray pond . ystem was also modified.
,
FENCE
•
o reduce water loss due to drift, and to prevent property
damage. this system includes _ around the pond.
7
'
.'
downstriam
' . '
.
• 1
·
. '
.. ,,:
'. ,
. .
--,. .
:.; , .,
,
.'
I
,
air
or·itmosph r
; . ~ ~ .
.,. .
:
,
,.
:;.;..,
.
'.
. ' ; .:; ; .6
.'
sprayed
air
. .
Increases
.,.
.
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75
he
air contacting both of these ponds
is
at the same humidity
level.
O
WINO
" ' U ~ l u A I R
WINO
B
As e v p o r t i o ~ occurs, the air in conlact wilh th water
becomes (morelless) saturated.
76. As the ail becomes m Te saturated, the rate of evaporation
77 . he air over pond B never becomes saturated because it is
constantly being with new air.
78.
he
rate of evaporation is mnre constant
in
pond (A/ B).
79.
he
rate
of evaporation in the open pond, t
he
spray pond,
and the spray type cooler
is
greatly affected by the prevailing
80.
he
rate of evaporation
is
also aflected by the .
of
the
air.
Atmospheric Cooling Towers
81. Exhibit 1 shows an atmosphen c cooling
tower
his cooling tower, like a pond system, depends on the
_ : _ .
_ velocity and the relative _
_
of the air.
82. Some of the wind entering the tower is carried upward,
but
most of the wind blows straight the tower.
83
.
he
wind flow through the tower is interrupted and changed
by the and bars
84. he louvers help direct wind and also
prevent
water
/
85.
he
hot air and water vapors leaving the top of the tow
have to pass through
the
.
86. Some atmospheric cooling towers have adjustable sections of
and drift to aid
in
the
control of air flow .
87 ':The splash bars slow down the raU of water and break it up
into small
8
more
decreases
replaced
B
wind
humidity
wind; humi dity
through
louvers ; splash
loss
drift eliminators
.
. . .
louvers
; e
liminators
.
drops
. .
.
.
l , ,
8/20/2019 Cooling Tower Section 1 API
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, ,
, ,
Cooling T W ~
i
, "
, , .'
EXHI IT
OOKLEY
, "' j
" ( " ' j ':
.
. :
::::
"".':
'
,
"
,: .. .
:;
':
:
.
,
, , ,
-,
.' , .
:
.
.
,
" . ,
'
;.
'.
I .
:. " . · r ·
,
It
, -
:.
.
:
'. .' .
"
, ,
.
"
. .
, ,
8/20/2019 Cooling Tower Section 1 API
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=::>
COOLED
WOTl :
BASIN
ATMOSPHERIC COOLING
TOVIER
j'
:\
,
..
_ _ _?HOT AIR
ANO
WATER VAPO j
.
/
FROM HO
'
WATER
I
,
•
I·
,
,
" '".oC l
. I
i
J
;
,
•
,
j
-
1 1 r b ~ ~ ~ ~ ~ ~
MAKE
-
WATE
CO
OL
WATER
,
, ,
- : ,
. ' , .
: j l
. . ...,
-,
. • I ~
I .
8/20/2019 Cooling Tower Section 1 API
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I
.
l . ,,
;,
NATURAL - DRAFT COO LING TOWER
HOT
AIR AND W
ATER
VAPOR
•
I - -CHIMNEY
. HOT W4-r
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FORCEO ORAFT
COOLING TOWER
HOT AIR
DRIFT
M N AT OR
HOT WATER N
SPLASH BARS
SO
LID
SIDES
S
~ O O L E D
WATER BASIN
COOL WATER
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. .I .
WAT. Q B SIN
INDUCED-DRAFT COOLING TOWER (CROSS-FLOW)
HOT l ND
V POR
ROSS FLOW
IR
M KEUP W TER
COOL W TER
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INDUCED DRAFT COOLING TOWERS
A.
COUNTERFLOW
I R ~
AIR
B. CROSSFLOW
...... -
LOUVERED
SIDES
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88. The longer contact
of
water with air causes quicker·
and faster than in a spray pond.
89. Due to evaporation and drift, there is
some
\vater
which has to be replaced with makeup
90.
s
the
quantity
of air passing up and through the cooling tower
changes, water loss due to evaporation and drift
91. The longer air remains
in
a cooling tower, the (more / less)
moisture
it
absorbs.
92. he
more moisture the al contains, the :faster/ slower)
it
ac(:.epts more moisture.
93. In order to
get
maximum evaporation in a cooling tower, the
air should pass through (quickly/ slowly).
94. Look at this drawing.
D
IRECTIO
N OF
PREV ILING
WIND
-
A
B
More evaporation will take place in tower A / B).
95. For best operational results, atmospheric cooling towers
should be placed
so
that the prevailing wind blows through
the (shortest / longest) dimension
of
the tower.
/96 :
In
an
atmo
spheric cooling tower, a lO-mile-per-hour wind
wi l
cause (more/ less) cooling than a I mile-per-hour wind.
97. Without wind, an atmospheric cooling towe l operates (more
efficiently/ less efficiently).
9
. Atmospheric cooling towers are designed
to
operate
best
under
the
normal prevailing wind conditions at each site.
f wind velocity is much higher tha n normal , there will be ...
higher than normal loss
of
water due to (drift/ evaporation).
99. High winds
will
cause water to be blown (rom atmospheric
cooling towers. Such towers are placed so that water blown
from them will not cause to surrounding
buildings or equipment.
9
.
evaporation
cooling
loss
water
changes
more
slower
quickly
A
shortest
more
less efficiently
drift
damage
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100.
Whenever watel is cooled by evaporation,
1
here
IS
always
some water
_
101 When cooling
water
10°F by evaporation, one percent
of
the
water is lost due to evaporation. In cooling 100 gallons
of
water 10°F, a tower loses ga;lon(s) of water
due
to
102 Drift loss is usually about 0.
2 of the
water
flow
or about
gallon s) per 100 gallons.
'
103 . Makeup water is used to replace water loss due 10
or leaks.
104. If there are no leaks and a cooling tower cool s 100 gallons of
water 10°F, there
will
be gallon s)
of
water
loss due
t
evaporation
and
, alIon(s) due
t
drift.
eview
105.
An atmospheric cooling tower depends upon wi
nd C _
and
the
relative of
the
air for effe
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. he splash bars break the falling wa
ter
into fine drops in order
to provide better air-to- contact.
of the heat in water transfers to the air. As the air
heats uP. it beeomes (lighter/heavier).
When it
is
light enough. the air
in
the chimney.
; J.l1e heateu air is replaced with co ld air that
e n t e ~ s
the tower
through
the
Beeause of its design. a natural-draft tower (does/ does not)
depend as much on the wind direction as the atmospheric
tower.
rature of th e air inside the chimney is always
_
than the atmospheric temperature.
. This difference in temperature causes a constant _
to exist.
he natural-draft cooling tower (needs/ does not need) drift
eliminators.
Makeup water is needed to replace water loss due to leaks
and
. Louvers or baffles
at
times are installed around the air inlet
of the natural-draft tower.
9p.ch louvers or baffles can / cannot) control the amount of
aIr
entering the tower.
.
y
regulating the amount of air entering the tower, the
amount of cooling due to can be regulated.
Cooling Towers
Atmospheric cooling towers depend upon the natural
flow
of
up and across the falling wate
r.
Natural-draft cooling towers create an upward
flow
of
h r o u ~
the falling water.
3 shows a forced-draft cooling tower. he air flow
through the falli ng water is produced by •
ernal construction of a forced-draft cooling tower is
c;imilar to an atmQspheric tower, but the sides are ,_
Motor...{ riven fans force air into the tower through openings
near the of the tower.
11
water
lighter
rises
air inlet
.-
\
\
.,
J
does not
_.
....
.
.
·
, ,
>
.
- -
'.
hi
gher, or warmer .
· .. . f
draft, 01
flow,
or
movemen
does not need
evaporation
can
evaporation
. aIr
au
fans ·
closed. or solid
bottom, or base
.
',
· . , .
, / :: \ '
. ',
,
.
I
, 'I ; 1
,
..
8/20/2019 Cooling Tower Section 1 API
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0. The cooling of the water in all towers depends mainly on the
amount and D air passing throug
h
uSed
in forced-dra
ft
cooling towers should produce a
large of air with a low velocity.
2. Both mechanical-draft and atmospheric towers
are
provided
with
_ _
to prevent water
loss
due to air velocity:·
. f one
01
more of the fans is shut down, the cnoling rate is
due to low -to-water contact .
The
degree of cooling can be adjusted by controlling one .or
more of the and the rate of flow.
In a forced-draft cooling towel , the fans (push pull)
the
air
through the towe,
Look at Exhib
it
4. In the induced-draft cooling tower, the fan
is located at the of the tower.
7 s the fan ro
tate
s, it (pulls/ pushes) the air through the tower.
8. The air is driven upward.from the top of the tower, where it
can be carried away easily
by the
_ _ _
. his reduces th e
po
ss ibility of wet air reentering
the
at
the
bottom.
Exhibit
5
shows two types of induced-draft cooling towers.
The tower with its sides open is the ype.
In the counterflow type, the largest
part
of the tower has
ides.
. In a tower with solid sides, the induced air travels most of the
time
in
the same
direction
as
/ an
opposite direction from)
the
falling water, •
Both towers
have. movable
s ide louvers to regulate the
- -
ntake.
.
In
both towers. the air volume flowing through the tower is
controlled by the of
the f n
and the
amount
of opening of t
he
side
12
humidity
volume. or amount
drift eliminators .
less; air
ans; air
push
top
pulls
wind
.,
i
cooling tower,
01
air intake
.
cro
ss
now
enclosed , or solid
•
an
opposite direction from
speed
louvers
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-Cell Cooling Towers
Large eooHng towers are usually constructed in
ells
or sections
which can be operated independently.
The cooling capacity of a multi-eell cooling tower
c n be
de
creased
y
taking one
or
more out of service
. This
is
:lower side view of an atmospheric cooling tower.
The drawing indicates that the tower has cells
47 f
a tower with only one cell needs cleaning or repairs, the
entire tower has to be
48 Any cell can be operated independently. f one cell in a multi
cell tower must
be
shut down, the entire tower (must also bel
need not be)
shut
down.
Review
149
An atmospheric cooling tower depends greatly upon
the
natural
velocity
for
effective operation.
150 The
natural-draft tower is constructed in such a way that it
causes its own
, 151 Mechanical draft
towers
depend
upon motor driven
o force the air through them.
152 The induced·draft tower (pushes/ pulls)
air
through
the
tower.
,153. A tower with fans
at
the bottom is (an induced / a forced)
-draft tower.
154 All cooling towers cool water primarily by the process of
155 The
rate
'of evaporation of water depends upon
the
water
surface-to-air contact and on the relative
of the air.
13
sections,
or
cells
three
shut down
need not be
wind
draft
.fans
pulls
a forced
•
.
evaporation
humidity
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The greater the water-to-air surface contact, the
the rate of evapol·ation.
The greater
the
water-to·air contact, the more
__
_ _ _
is accomplished.
.
The .plash bars in cooling towers break up the spray
of
water
into smaller droplets as
well
as prolonging
the
water-to
___ --_
contact.
f the air passing th; ough a cooling tower is water·saturated
to the maximum, there
will
'
will
not) be
any
cooling due to
evaporation.
. f
there is no e aporation taking place,
but
the air
is
cooler
than the watel , there
will
be (no/ some) cooling du
' to on·
duetion, convection, and radiation.
In a cooling tower there is always some cooling
o
water due
to conduction, convection, and
______
. However , most
of
the cooling of water in a cooling tower is
accomplished by
_____
In any other
type
of cooling tower, drift eliminators a
re
needed
to minimize water because of the wind.
However, in a natural-draft cooling tower, drift eliminators
. (are/ are not) used.
Any cooling tower
is
subject to water losses produc
ed
by drift,
ll? aks,
and evaporation.
These losses are compensated for by water.
In
mechanical-draft towers, the volume of air passing through
the
tower can be adjusted by controlling one or more
of the
Controlling the volume
of
air passing through the tower
(controls/does
not
control) the amount
of
cooling.
It is easier
to
control the amount
of
cooling in a(n} (atmos
pheric/mechanical-draft) cooling tower.
Mechanical-draft towers (can/cannot) regulate or control
the
amount of air passing through the tower.
They cannot control the relative ______
of
the air .
They cannot control
the
temperature of the _
__
___
used for cooling.
.
Mechanical-draft
towers
can ·control
the
amount of all'
passing through them, as well as the
__
_
o
evaporation of the water.
14
(aster,
or
greater
cooling,
or
evaporation
will
not
some
radiation
evaporation
loss
are not
makeup
ans
controls
mechanical·draft
can
humidity
'
•
ir
rate,
or
amount
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nstruction aterials
S. When iron is exposed to water and the oxygen in the air,
it
4. In
a cooling tower, practically all
parts
are exposed
to
____________
and
__________
__
6. Iron and' carbon steel are used to a very limited extent in
cooling tower construction because
they
corrode or
rust
(rapidlyIslowly),
76.
The
best grades of California redwood are used because they
resist cOT "osion caused by and ____ -_
77
.
laetals
WhlCh resist corrosion are used in certain
parts
of red-
wood towers. Copper-coated nails resist ______
78. Cast-iron is used in anchoring members
that
hold
the
tower
on its concrete basin, but
it
does corrode and has to be
_ _ _ _ _ _ _ _ _
occasionally,
179.
Brass boltS, washers, and
nuts
are used because they also
_______ corrosion and rust.
180. Fir
wood is used as well as redwood because
it
resists
rot due
to
moisture. Like fir, synthetic materials such as tensile, fiber
glass, and other plastics resist moisture rot (poorly / well) .
181.
Although some wood resists corrosion and rot and has rela
tively little expansion due
to
heat, wood sw lls when
it
absorbs
water
and when
it
dries.
182. Expansion and contraction from either temperature change
or water content change
can _____
he tower structure.
188. Treating the tower wood with creosote increases its resistance
to 1.t0th
water-logging and moisture ________
__
184.
Synthetic materials are (more/ less) damaged by corrOS Ion,
water-log and,
rot
than
wood.
186. Regardless of the material used in construction, cooling towers,
like other refinery units, should be peri-
odically for structural soundness,
Cooling Tower Mechanical Equipment
186. The
fans on forced- and induced-draft towers are driven
QY
electric
____________
187.
The
pressure necessary
to
circulate
the
cooling water through •
the plant cooling water system is provided
by
direct-acting
steam
or
motor-driven
_ _
_____
188.
All mechanical equipment with rotating or moving
parts
must
be lubricated on a definite schedule
to prevent
exceSSIve
15
.
corrodes, or rusts
.,
water; air
rapidly
water;
ail'
corrosion
replaced
resist
well
'.
'I ' . , '
,
' ' J ' q
, i
contracts, or shrinks ;i
,
weaken
rot, or
damage
less
,
,
. ,
'
:
..,
,
.
.
•
. ;
.
¥
. :
./;
.
inspected, or checked
;'
.J" · . t
il
motors
pumps
wear
..
,
,
,
.
'.
. ,
. ' ,
8/20/2019 Cooling Tower Section 1 API
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The operator must lubricate equipment regularl y and
all equipment daily for other co nditions
which require repair or replacement.
AFFECTING
COOLING TOWER PERFORMANCE
. The most important factor in
any
kind of cooling tow. r
is
how
fast
the water
any
condition which prevents
water
from evapo-
rating
.'.
the
efficiency of the cooling tower.
Air contains moisture or water vapor.
On a
damp day,
the
air holds (a
lot of
/ very little) water.
f the
air surrounding a cooling
tower
is
very
humid, the water
in
the
cooling tower does not evaporate as much as it would
if
the
air was
On damp,
humid
days, a cooling tower works (be
ter
than
/
not as well as) it does on dry days.
that affects the rate of evaporation
is
t
he
amount
of in
the
air in
contact
with
the
\vater.
and
Relative Humidity
. Air becomes denser as
the
temperature decrea., s.
Air
is densest
when
temperatures
are
very hot
/ very cold ).
. More moisture can
be
contained
in
air if
it
is less dense.
Very cold air
can
contain (more/ less) moisture
than
hot air.
Temperature
(is / is not) an
important
factor in measuring
humidity.
Here is one way
to
express humidity measurements.
Suppose we
have
a humidity measurement
that
reads 1 pound
of water in
10
pounds of air.
This
reading
is
expressed as
(degree of saturation/ weight per given volume) .
Pound is
an
expression of a specific
quantity.
1
pound
and 10
pounds are (relative/ absolute) expressions
of
quantity
.
per quantity is (relative/
absolute) humidity.
Temperature is not considered in measurements
of
absolute
humidity.
~ t > s o l u t e
humidity
readings tell how much water is in a given
quantity of air, but (do/ do not) tell how much
more
water
.
the air
can absorb.
6
check. or j n s p
evaporates
reduces
a lot
of
dry
o.
not as well as
humidity. or moisture
very cold
less
is
weight
per
given volume
a0so1ute
absolute
do not
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. order tc know how much evaporation can take place, it is
_sary
to know how much more
the
air
absorb.
ipposewe have a humidity reading that says air at 85
0
holds
of the maximum it could hold
at that
temperature.
~ ~ \ ~ ~ ~ I ; ~ S expressed as degree of
saturation
/ weight per
humidity reading s given a
p ~ r c e n t a g e
of maximwn
Humidity erprE:S.Sed as a
f J f : ' T ~ n t a g e ot
maximum humidity at
a given t a n ~ t U e s rtlative / e;bso\utE: / humidity .
206. A r e I a t i . . - ~
humidity
reading doc do.,; not) give
an
indica·
tion of how much more wa ter air can absorb.
207.
f
air bolds all the water vapor it can hold at
any
temperature,
it
is
aaid
to
be
.208. The
relative humidity
o
air
at the point of saturation
lS
0 0
209.
AJ.
relative humidity increases, evaporation
210.
T h ~ \ . p e r f o r m a n c e of a cooling tower increases/ decreases) as
the
relative
humidity increases.
211.
Relative humidity is the least/ most) important variable
af·
fecting
the
performance of cooling towers.
Dry.and Wet-Bulb
Temperatures
212. This combination of thermometers and wick is a hygrometer.
'
THERMOMETER
The thermometers are identical except
that
one bulb s covered
bya
17
water .
degree of saturatio_n
relative
doos
saturated
100
decreases
decreases
most
'
•
wick
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:213. Beeause the wick is saturated with water, the thermometer
I it covers is called a ·bulb thermometer.
214.
Evaporation has a cooling effect.
I
I
I f
the water in the wick
of
the wet-bulb thermometer is
evaporating, t
wiJ
show a (warmer/cooler) temperature than
the other thermometer. .
215. The
faster evaporation occurs,
the
(greater/ less) difference
there will be in flte readings.
216.
Evaporation will occur faster If the air surrounding the wick
is (moisUdry)
.
217.
In
dry air, the wet-bulb reading is always (lower/ higher) than
the dry-bulb reading.
218.
Suppose the dry bulb reads 90°F and the wet bulb reads 75°F.
100
90
80 %
90
/ b
/ .
f0
7
-.e
50 / · 0
0:
80
f-
w
~
70
:E
a:
W
:
./
V;
t =
/
/
V
0 V
/ .
V
V
v
V
y
V
0
'
:n
m
,
:.-
20 1
<
m
10
0
•
I
:x:
f-
ro
60
--'
=>
ro
f-
50
w
;0:
,,:
V V / V
t:
V V
./
V
/ V /
/
V
V
C
3:
>2
i
-<
40
;:::::
v::
V
:/
50
60
70
80
90
100
II: DRY UL TEMPERATURE
The
chart shows that the relative humidity is_____ .
ZI9. I f the dry bulb reads 60°F and the wet bulb reads GO°F, the
relative humidity is
.
l20. The greater the difference between readings, the (higher
lower) tbe relative humidity.
18
wet
cooler
greater
dry
lower
50
100
lower
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, .
A sling psychrometer also measures relative humidity.
GAUZE
WICK
. .. .
.
. .
.. _- .
DRY
BULB
The operator whirls the sling psychrometer n the outside
atmosphere after saturating the wick with --'_
22.
f
the atmosphere
is
not
satura
ted , there will be _ _ _
readings on the two thermometers.
:23.
When the wet bulb reads lower t
han
the dry bulb, it
is
because
water
has
from
th
e wick.
124
Evaporation causes
25. Cooling tower performance is (highest / low est) when wet- 'and
, dry-bulb temperatures are equal.
Even when the air is saturated in the tower, some cooling
occurs
y
convection and conduction.
1Zl
Therefore
,
cooling
t owers do not depend entirely on
_ to accomplish cooling.
When the outside air
is
cooler than
the
water being cooled,
some cooling occurs due
to
radiation, and
even though none occurs due to evaporation.
228
)ve'\thoullh no evaporation occurs,
i
the air is cooler than
the
, water; heat IS transferred from
the
water
to the
.
.
229 . The heated air
then
carries the
heat
with
it
out of the tower
by
_ _ _
230
Cooling towers are never 100 efficient.
f
the
wet-bulb temperature is 65°F, that would be the n -
mum a pproach
temper ture of the water.
The
lowest possible water temperature after cooling with the
above condition would be
(6
0 F
above
65'F).
23I
The
efficiency of cooling towers, regardless of
type
increases
as the difference between wet-bulb and dry-bulb temperature
19
•
water
different
evaporated
cooling
lowest
evaporation
conveetion
conduction
convection
above
65 F
increases
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Operation
The degree
or
cooling in cooling
towers in part
depends
on
the
amount of air flowing through the
In
addition il the air is hot and humid the degree 01 cooling
is (more/less) than when the air is cold and dry.
air temperature may result in too much
_
Water freezesat
3Z0F
In winter, air temperatw e well below 32°F may cause cooling
water to
on
parts of the coo
lin
g tower.
6. Because of more co ld air contact, water broken up into small
droplets freezes (faster/slower) than
if
it was in a solid stream.
(onnations may
~
_
the passages between
splash bars.
The
operator has to watch (or fannation of ice around the fan.
I ice builds up around the Ian too much it
may
shut
off
the
How
01
In cold weather moisture-filled air is
li
kely
to
form _
on
the
fan blades and other moving parts.
This may cause overloading 01 the fan motor and costly
The operator needs to know how to prevent _
. formation in the tower and
on
moving parts.
One way to control
fr
eezing
is to
limit the quantity of
cold
entering the tower.
In
atmospheric towers, adjustable louvers can
limit the
intake
01
44
To
limit the intake
of
air
in
induced-and forc
ed
-
draft
towers
the can be slowed
or
shut down .
245
Decreasing the pitch
of
the Ian blades will also reduce the
ntake.
246
f ice has formed
in
the fill deck it can be melted by reducing
the
amount of co
ld
entering the tower.
247. The incoming water will melt the ice because the water is
248 ans which do not have variable-pitch blades are usually
equipped so
that
the direction of rotation can be
Now tum the page,
2
turn the boo t over, and go on .
•
tower
less
cooling
freeze
laster
block
Ice
damage, or repairs
ice
alf
f ns
air
hot,
or
warm
changed. or reversed
•
8/20/2019 Cooling Tower Section 1 API
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On a forced-draft towel', the fan pushes the aIr into the
(top bottom)
of
the tower.
R ,d sing the pitch
of
the fan blades causes air to be (pushed
into
/ ;
ucked out of) the tower. .
Since
the ail
in
the
tower is hot, reversing
the
fan
can/cannot)
melt an ice buildup.
: -
The quantity
of
ail' flowing through the forced- or induced
draft towel' can be controlled:
by shutting off one or more _ ;
by
changing the pitch 01' direction of rotation of
and
by
changing the
of
fan motors.
and Summary
Cooling towers are needed
in
modern refineries
to
reduce
the
temperature of cooling water. Cooling water needs cooling
so
that
it can again
be
used
in
exchangers
to:
condense petroleum
cool products enough so that they do not go off
in storage due to heat; and to products
to
pressure- or fire-safe storage temperature.
Cooling towers depend mostly on the (conduction
of
heat
from water to air/ partial evaporation of water .
Evaporation depends on water-to-
contact.
The most important condition affecting the rate of evapora
tion: is the (temperature/ relative humidity) of the air.
: .
Atmospheric cooling towers depend primarily upon the pre-
f. vailing
for
performance.
The natural-draft tower is designed in such a manner
that
the
heat of hot water causes a through it.
f-
In fo""ed- and induced-draft cooling towers, the draft is
caused by motor-driven
The draft in forced- and
(eaaier/harder)
to
control
towers:
induced-draft cooling towers is
than
the
draft
in atmospheric
Redwood
and
fir
is used in
the
construction of cooling towers
because it resists wet
21
•
bottom
.
sucked out
of
, ,
can ::t ,,'
fans
fan
blades
-.'
: ; :(:1
:
.•
,
.
.
'. .
..
" .
. . .
.
:
,r- ,
.
.
..
.,.. t
·t
I
::
'
..
'.
,
peed
. ' :'
..
vapors
specification
cool
.
.
,;
partial evaporation
of
watt
air
relative humidity
.
...
wind
-;-
.'.
.
•
.
. t
,.
draft
.'
,
.'.
,.
:-
ans
': 1>
..
¥
i'
.
I
,
. , .1
I'
,
',.
easIer
t
.
' : .
ot
,.
':i
.
8/20/2019 Cooling Tower Section 1 API
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Ideally, metal
parts
of the towers should be highly
to con-osian .
. Metal
parts are
coated with special
to
in·
crease their corrosion
resi
stance.
The operator should keep
alert
to evidence 1 excessIve
and wet
Cooling towers perlorm best when th air passing through
them-
is
cool .and (dry jwet).
.are instruments used in
determining
the _ 1
the air.
f there
is
no difference
in
the temperature reading of a dry. and
w e t b u l b thermometer the relative humidity is .
.
At
100
relative humidity, there
will
be (some/
no
) cooling
due
to evaporation.
Even though there m
ight
not be any cooling due
to
evapora·
tion, a cooling tower
will
still cool water slig
htly
due to
radiation,
and
.
In cold climates, where temperatures get belol. Ireezing, the
- operator must guard against the (ormation 1 _
in
the tower as wen as the fans.
A natural·dralt tower (needs /does
not need
drift eliminators.
All
other towers have
to
reduce loss of water due to wind .
73
. Makeup water is needed in cooling towers to replace water
loss aue to leaks, and _
CONDITIONING
ND CHEMICAL PROPERTIES OF WATER
1
H20 is a chemical symbol (or water. It shows that a water
molecule is a compound made up
o
two atom s of hydrogen
and one atom of
2
wnen hydrogen and oxygen combine to (orm water, the
process
is
a (chemical/physical) change.
22
• J
:
r e s l s t n
coating or paint
corrosion. or rust: rot
dry
relative humidit} «
100
•
no
conduction; convection
ice
does not need
drirt eliminators
evaporation; drift
•
oxygen
chemical
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3. The drawings show different changes that water can undergo.
E J
t ~ ~
(
I
. .
, ,) ,,)
(
-' r ))
I
-
l
ICE (SOLID) WATER (L IQUID)
BELOW
32
F
32 F
TO
212 F
STEAM (GAS)
ABOVE
212 F
These
changes are (chemical / physical).
4. Whether water is a solid liquid
or
vapor its molecule are
. still composed of two atoms and one
atom.
~ e a t i n g or
cooling water causes
it
to change state from one
form
to
another
. Changing·
the
state
of
water is only a change.
. .
6.
A ·ehemical change occurs only when atoms
or
molecules
change from one substance into an entirely
substance.
: ·7 .Water does
not
undergo chemical change easily.
. Chemically,
it
is relatively (stable/ unstable).
il 8:'
Water also has a good heat capacity. That means that
it
has
,
.
i
.a good capacIty
to
absorb .
9. BTU stands for British Thermal Unit. It is a measurement of
quantity of
energy.
10 pteiji£ al is the number of BTU's required to raise the tem
perature of pound of any substance ° . For water this
takes 1 BTU.
To raise 2 pounds
of
water by 1OF for example requires
BTU's.
,
.
11.
Here
is
a table of specific heat values for different substances.
,
\r "
toY;'
,.
l '.'
t'
Substanee
t
b*_
Air
.
..
. :
Alcohol
r ' ··Aluminum
" . Brass
...
.... Copper
fj
>;; ·Earth (dry soil)
• c-
Glass
'. :
,
..
Gold
;
J
,
ce
Iron
(steel)
;; "
. (
. ..
Specific Heats
Sp.
Ht
.
Substance
Sp.Ht.
0.24
Kerosine 0.50
0.
60
Lead
0.03
0.22
Lube Oil 0.45
0.091
Mercury 0.033
. 0.093
Steam
0.48
0.20
Stone
0.192
0.21
Tin
0.055
0.032
Water 1.00
0.51
Wood (avg.)
'0.42
0.115
Zinc
0.093
.' Kerosine has a specific heat value of
23
, .
•
physical
hydrogen
oxygen
physical
different
stable
heat
heat
2
0.50
,-
8/20/2019 Cooling Tower Section 1 API
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12. To raise the temperature of 2 pounds of kerosine by 1°F
,requires BTU.
3 . When any 1iquid or fluid is used as a coolant, it absorbs heat
energy from the material being _ _
. As a coolant absorbs heat energy, its temperalllre'
5. Raising the temperature of 1 gallon of
ker
osine a certain
amount requires (more/ less) heat than raising a gallon of
water the s me amount.
16. A substance with a high specific heat can absorb (more/
less
)
heat per degree of temperature change than a substance with
a low specific heat.
17. A substance with a high specific heat should make a good /
poor) coolant.
18 . Water can disso1ve
m l.n
y things. Water
is
norrnally a (good /
poor) solvent.
19. Many tiny, i n s o ~ u b l e particles, such as grains of sand, rust,
and calcium carbonate, become suspen e
in
water .
Water can contain two kinds
of
solids : (1) dissolved solids
and
2)
solids.
20 . Water
is
made up of two and one
atom.
21. Chemically speaking, water is (stable/ unstable ' .
22. Water makes a good coolant because it has a _
specific heat.
23.
Because
of
its
properties. water can
carry various solids.
_ . and
24. The two types of solids th t can be found
n water are
and solids.
OF TOT L SOLIDS
O
COOLING
25
. The makeup water used in refineries comes from natural
sources such as rivers, lakes, and wells.
Such waters are likely to contain both and
solids even though they may appear per-
fectly clear.
24
•
1
cooled
rIse
s
less
.
more
good
good
suspended,
or
undissolve
hydrogen
oxygen
stable
high
dissolve
dissolved; suspended
dissolved
suspendod
..
8/20/2019 Cooling Tower Section 1 API
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26.
Because the water circulates many times through pipes, ex
changers" rooling towers, and basins, it picks up (more/ less)
solids.
27. ,The total solids increase because the water
. i·
a little
bit
of
the substances it contacts.
,i8'.'When water evaporates,
it
(takes/does not take) the solids
with it.
,
~ R
.'
-
29. Mter
partial evaporation,
the
solids tend to concentrate in
v l
the remaining water. Ccx.>led
water leaving a cooling tower
} ~ has (mOl'e:
1ess
) total sohds per gallon
than
the hot water
i
.
entering the tower.
. \ ~ t
.I .
..
'
80. The circulating water
in
a cooling system has (more/less)
'total solids than the fresh makeup water.
. ·ji} : . •
:
sl
f,
So,
the
discarding
of
some
cooling water and the addition
of
ll
'
~
m a k e u p water tends to keep the total volume of solids
)J
.(up/down).
r '
Suspended solids tend to settle out in sections o(
the
cooling
.system where
the
vel
oc
ity o(
the
water is (slowed/increased).
C'
1
f
3S
. 'Some diasolved solids are less soluble in hot water than in cold
i;l¥"i .a
ter
. When the water becomes hot, these dissolved solids
. , . ,
Decome
solids
. ; ...
,
.
34. Calcium and magnesium carbonate are less soluble in hot
", ,:: water than in cold water. When cooling water goes through
0" •
t .: heat exchanger, calcium and magnesium carbonate become
, . . solids.
, ' j
':'1- i
1 : ~
,.>
~ e ~
~ t e r containing calcium and magnesium carbonate
,_ .'
. , \8
>otled
n a vessel, form on the sides and
~ bottom of the vessel.
t-f f > : ,
.
l-
....
'
.oj.
36
. The aame thing happens when
the
water
pa
sses
through a
'. '
heat '
"","
... .. .....
.}1 " " , )
3 i : D e p o s i t s
or scales (ormed in the tubing o( heat exchangers
'- ,will {increase/decrease} heat transfer.
...... r··
>1 :1/ ,:
S 8 . ,The 'buildup of deposits in an exchanger, regardless of
the
t . . 'cause or
source of the deposit, is called fouling. Fouling makes
~ i l t P e r i o d i c necessary. ' .
¥
A
~ o a r s e , suspended solids also cause wear in narrow passages
..
;or turns in the flow. This
kind
of wear is (erosion/ corrosion).
'
~
4 0 . ri. oo much buildup of solids is permitted in a cooling tower,
. . . it, too, has to be periodically.
,
25
more
•
dissolves
,,
does not take "
, "
more
{
more
down
exchanger
.
decrease
::.:
cleaning
,
••
-
\
erosion
cleaned
8/20/2019 Cooling Tower Section 1 API
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41. Tiny, microscopic plants sometimes thrive in cooling water
systems.
These tiny growths, often green in
col
or, r
eq
ui
re ligh
t in order
to grow. They
start
growing on the wa
ll
s of
clo
sed/open)
parts
of
the system.
42
Parts
of the
growth break away from the
wa
lls and
start
floating in the water. They become part of the
solids. .
43. They Cfl n
plug narrow passages
in
the system
and
damage
woodinthe
. These are biological, or living, substances.
To
control or stop
their growth they have to be _ _
45
. The biological growths are algae and slime. There are a number
of varieties; all cause to cooling systems.
46. Cooling water,
in
addition to dissolved so
li
ds and suspended
solids, contains some dissolved oxygen and carbon dioxide
which
are
solids/gases).
47
. It
is
not the water in the system that causes cor ro sion, erosion,
and fouling.
It is the disSolved suspended
so li
ds, and
dissolved
KEEPING COOLING WATER IN CONDITION
48. Waters from different water sources are likely to contain
kinds and quantities of solids and gases.
49
. The chemical analyses and the physical tests made on the
different waters are likely to be _ _ _
50
The chemist prescribes what the operator must
do
to keep
the
cooling water in good
51
The operator may
be
required to make a
few si
mple tests and
change his
of
the water as the te
st ma
y indicate.
52. Because each cooling system is different and t he natural make·
up water is different, methods of treatment are
CONTROLLING
SUSPENDED
ND DISSOLVED
SOLIDS
,63 . If it is necessary or the operator
to
make certain
te
sts on
cooling water, his supervisor will arrange f
or
the necessary
instructions and for the test .
.
5
.
Chemists use two measures to express the quantity of various
f .
impurities in water: grains per gallon gr
. /
ga
l
) and parts per
: million PPM).
One
grain per gallon equals
17
parts per millio
n
f the
total
solids in cooling water is 10 gr./ gal., the
PPM
is
26
open
suspended
cooling towers
killed, or poisoned
dama
ge
or
fouling
gases
solids
gases
different,
or
various
different
condition
l:
eatrnent; r eonditi
different
equipment, or tools
170
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:55: Cooling water analyses usually are reported in
PPM. 50
PPM
. total solids means that in one million pounds of water there
; ". are pounds of suspended and dissolved solids.
. t
.•
~
56.;rhere are both suspended and dissolved solids in the natural
makeup water. These
solidc; in
crease in the cooling tower water
~ ~ b e c ~
of and because
of
the treating
. chemIcals that are added.
. ','
, ,
,
,
. 57.
Some small increase of both kinds of solids also comes from
:t he basins, pipes, and wood
in
the cooling system .
.
. : r h e total
of
solids in cooling waters varies from one PPM in
;,j;lt relatively clear water to 50,000 PPM in muddy river water
~ " .
Muddy rive,' water probably has (more / less) suspended solids
. : : :
~
than dissolved solids.
~ . ~ : . ,
' . . ,
,' •.;,·,(-
.t
... - .4 . , •
.
,:.\i.i"
- ~ . . : . ~ . "
sedimentation Ba$in$
-',
,
'1
8/20/2019 Cooling Tower Section 1 API
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Mechanical and hemical Clarifiers
68
. Mechanical clarifiers take up less space than sedimentation
basins.
V RI BLE
SPEED DRI
OUTLET L A I U ~ ~ ~ ~ r
.
HARD
WATER
INLET
CHEMICA,L FEED
INLET
~ ~ ~ ~ J i S L U D G E OUTLET
Here, turbid water and coagulating chemicals are
fed
in
through (the same inlet /different inlets),
69 The design
of
the clarifier causes the chemicals to be thor-
oughly with the raw, turbid ,vater.
70.
Aluminum compounds such as aluminum sulfate, sodium
aluminate, and iron compounds, such as ferrous sulCate and
ferric chloride. are coagulants.
When added to turbid water with other chemicals, they speed
up
71 . Coagulants with other chemicals form a spongy floc which
settles rapidly, taking with it sediments, algae particles, and
other suspended
72 The chemicals coagulate the suspended solids so th t they
become heavy enough to settle quickly to the
of the clarifier tank.
73 The solids pile up as sludge on the bottom of the clarifier tank.
A rotating scraper moves the sludge toward the center where
it
can
enter the sludge
•
.
74 Because the chemicals speed up the settling, these clarifiers
require more/less) space than a sedimentation basin.
75
Because
of
the coagulating action
of the
chemicals, water from
these clarifiers is
th n
water from sedimenta-
tion basins.
8
L
.
different in
ts
mixed
.-
sedimentation,
or purification
solids, or matter
bottom
outlet
.
less
clearer
or
deaner
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Filtration
76
. Suspended s
oli
ds can be removed fr
om
water by filtering the
solids out. Filte,'s
wo
rk by
ei
ther gravity
01'
pressure.
OPEN TO ATMOSPHERE
SAND
GRAVEL
WATER INLET
' , '
: . . : 7 -
_
-
'
BACKWASH OUTLET
l2::==
FILTERED
WATER
:= f t t=OUTLET
~ = = = = ~ ~ ~ ~ H I N L E T
This is a filter,
77, Note that the tank
[o
r this filter is completely enclosed.
•
BACKWASHING FILTER
BACKWASH OUTLET
'I·
,'
,, , This is a ilter.
78.
'Both gravity and '
pr
essure filters can produce
backwash.
:,i: Water can be forced back in the _
_ direction
~ normal flow
•
.
79.
,
The solids trapped in and on the filt er bed
r
e backwashed or
I(
ftusbed
into the disposal system.
.
Filters
are usually installed in batteries of two or more so
th t
. '< the flow of filtered water c n continue through t least one
o ,filter while the other is being
2
gravity
pressure
;
,:: - ' .',
,
:
:',
- ',
: .
.
.?,
, ',0,
: ~ :
'.
.
1 i,
; f
.
iI
. -i ,
I
' i
:.'
,,':
, ,
.f
:. '
t ' .
. r
,
opposite, or .e.·en
.
waste.
backwashed,
8/20/2019 Cooling Tower Section 1 API
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Hard water is water which contains dissolved
Distilled water does not contain either dissolved solids and
gases
or suspended solids and gases.
t
is ther
ef
ore soft/ hard).
Rain water
is not entirely so t because
it
picks up some hard-
ness from the solids and gases in the
Natural water from wells, lakes, and streams is often quite
hard.
When
the
water is heated, some
of
the dissolved solids in the
water fann
insoluble in the equipment.
85.
The hardness itself does not cause
corr
osion
in
the system
but the deposits create a condition favorable to _ _
by other impurities in the water.
86.
Cooling water conditioning is necessary to prevent
or
minimize
.. .corrosion fouling and formation in heat
.exchanger equipment.
87. The dissolved solids which cause calcium and magnesium
hardness also cause scale formation
if
the cooling water be
comes hotter/ colder).
88. Calcium and magnesium scale on heat exchanger tubes
significantly reduces
the
transfer
of
_
hrough
the tube walls.
89. Scale also reduces
the
flow
of
fluid through the heat exchanger
shell, completely plugging some or all
of
t
he
exchanger
if
it
is not removed .
90 . The formation of scale makes the equipmen t less efficient
, . and makes costly necessary.
•
91.
There are three widely used methods for conditioning water
against scaling.
One method is
to
soften
the
water by making
the
soluble
compounds insoluble so
that they
can be remoyed
by
settling
T
30
•
solid.
soft
air or atmosphere
deposits, or solids, or
50
corrosion
scale
hotter
heat
tub es or passages .e
cleaning
or repair
filtration
8/20/2019 Cooling Tower Section 1 API
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, '.
92.
This is a cold-process softener.
: ;
,
•...
CHEMICAL
INLET
MECHANICAL
M I ~ E R
,.
,. .
. ,
,. '
,
....
The softening reaction is accomplished
by
feeding in chemicals
such as ·lime nd soda ash and mixing them with the water
'Jli
·
by means
; 98 This softener uses heat as well as chemicals .
1I1J
_1
'- li;-.,'
, HARD WATER
.
INLET = = ; e : : ~
W
;;;.;;;
' : ¥ . ~ :
. I '
#
..
,: ..
CHEMICAL
INLET
it::I'
r , = . ~ - - - S,'EAM IN
~ E = = T R E A T E D
WATER
TO F I L T E R ~
SLUDGE
BLOW QFF
~ y
U H e r e
the raw water and the chemicals are heated y
~ ~ ~
.
~ ~
L
i
94;;
,There is / is no) mechanical mixing.
~
H e a t speeds up the softening reaction.
~ r B e c a u s e the reaction is speeded up in a given amount of time
i ~
hot-process softener can soften (more/ less) water.
i.,. ,
'.
••
31
.
,
...
'
.,
,.
,
mechanical
.:-
.
1 ~ ,
.,
steam
IS
no
more
,
8/20/2019 Cooling Tower Section 1 API
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96. f the processing rate for
bot.h
hot·
an
d coJd·process
unit ; i5
the same, the size of the hot / cold ) unii can be smaller.
97. eat makes the softening reaction mor£' complete.
For a given amount of processing time, the water from :
hot/cold)
unit
is likely
to
be softer.
98. Because its reaction is faster and more complete. chemical
costs for
th
hot-process unit are usually higher/ lower) than
th cqsts for the cold unit.
99 The amount
of
chemicals used depends, however, on th
hardness
of
the raw
100. Generally, the higher
th
hardness
of
th
raw water, the
higherflower) the chemical costs to soften the water.
101.
Zeolites, chemicals that produce ion
exc
hange, are
also
used
. to soften water.
.
.
HARD
WATER
INLET
ZEOLITE
SOFT
WATER
T
LET
==o; \lV
ION EXCHANGE
UNIT
REGENERANT
TANK
(SODIUM CHLORIDE BRINE)
In this kind of softener, the water intimately mixes with /
passes through) th zeolite.
102. An ion is an
atom
that
either
has
extra
electrons or is m j ~ i n
some electrons.
An ion exchange involves one substance collecting ions from,
or giving up ions to, another substance.
Passing
th
water through
th
zeolite makes possible/
prevents) ion exchange.
32
hot
hot
lower
water
higher
.
passes through
makes possible
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Usually, the zeolite has sodium ions attached to it.
When hard water passes through the zeolite, the sodium ions
of the zeolite exchange with calcium
or
magnesium ions
of
the raw
calcium 01 gnes Um removed, the
water
is now
than it was.
When all the sodi
um
attached to the zeolite has been removed,
the zeolite
can
st
ill
.
can
no
longer) exchange ions.
Suppose a sodium chloride brine
is
flushed through the
saturated zeolite.
There (
now
can be still can t be) an ion exchange.
The zeolite now exchanges or
ions with the brine.
The brine gives up ions to
the
zeolite.
sodium once more attached to it, the zeolite
is
re
activated.
. It can (once again/ still no longer) soften water passed through
to
.
The zeolite can only be reac tivated a certain number
of
times.
..
.
,
Eventually, the zeolite mu st be
Zeolite softeners yield much softer water than is usually
needed
in
a .cooling system.
Their use
is
generaJly limited to providing very soft boiler
feed water and some
of
the water in the
I
ooling
system
.
112.
Sulphuric acid also can be used in water to control scale.
Sulphuric acid is highly
113. Therefore, the quantity
of
acid added to the water has to be
carefully
114. The
sulphuriC acid acts on scale-forming substances
to
keep
tbem dissolved in the water.
Tbis means tbat adding sulphuric acid to the water makes
seale-forming substances (morelless) soluble .
115.
So long as these substances remain soluble,
it
is (easy/ difficult)
for them to settle out and form scale.
•
116. Retarding the rate at which scale-forming substances settle
out
(speeds up/slows down)
the
formation of scale.
117 ~ o t h r way to control the formation of scale is to blow down
or discard some cooling water continuously,
This lost water is then replaced with (hard / soft) makeup water.
33
water
·:.;, :;l
,
•
.
'.
"
.'
s o f t ~ .
..
can no longer
..
now can
calcium;
sodiwri ·
; , .
once again
makeup ,
,
corrosive
more
slows
soft
.
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ROSION CONTROL
Cooling water corrodes by destroying the metal which it
Perfectly pure water is not corrosive.
Cooling water corrodes because there are dissolved
and gases in it. '
Dissolved solids in the natural makeup water become can·
centrated because of _ which takes place in
the cooling tower.
.Gases such as oxygen and carbon dioxide are picked up trom
the
in
the cooling tower.
Carbon dioxide causes the water to become acidic. Acidic
water is corrosive/non--corrosive).
Oxygen in contact
with iron
causes oxidation
or
hese fonns of corrosion are in part eliminated by using
corrosion-resisting
in
construction of parts
which come in contact with cooling water.
But, using expensive metals entirely is more costly than
the water to lessen its tendency to corrode
metal.
i. One way
to
treat the water
to
prevent corrosion
is
to
inhibit
or stabilize the water chemically so that it will not attack
, . Another approach is to treat the water
so that it
deposits a
tbin, protective film on the of the metal.
lhoclic
Protection
1.
he tarnishing of polished metal is a fonn
of
.
Oxidation of the metal occurs in dry air. Water is not involved
in
the
corrosion This kind of corrosion
is
called dry
•
). Because water is involved, the kind of corrosion which occurs
in cooling systems
is
(wet/dry) corrosion.
1
During
wet
corrosion,
two
reactions occur at the same time.
Metal passes into the water and hydrogen p:\SSes
out
of
the
nto the metal.
34
,
,
contacts
solids
.
,
I
evaporation
\
aJr
corrosive
rust, or corrosion
metals, or matei
ials .
.
.
conditioning, or softenins
metal
surface
wet
water
.
, . .:
.
.
,
. ,
.. .
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1 ~ 2 .
When this occurs, there is a tiny
flow
of electricity between
• the water and the
133 The metal is the anode and the water is
thecathode
GALVANOMETER
CATHODE
.;;. ::-\- HYDROGEN
IRON CONDENSER BOX
The a l v a n ; ~ e t e r indicates a small flow of
, .;
34 Iron is going into solution from the metal walls (anode) and
hydrogen is l
eav
ing the water at the
135. Suppose a strong direct current
is
applied in the opposite
direction.
ELECTRICAL
SOURCE
+
In this situation, hydrogen leaves the water
and is taken from the rod.
136
The anode, which may be scrap iron, corrodes,
metal from the iron condenser box is
.
137 This arrangement provides cathodic protection metal
in the cooling water system.
To keep the current flowing in the right direction at tbe right
magnitude, the operator may be required
to
make adiust-
ments of the outside source.
138
.
The amount of current that must be applied from the outside
source
(depends/dOes not depend) on the corrosiveness
of
the
water and on stray c\PTtnt trom nearby electrical equipment.
,
1·;
, . .
metal
,
, .
current,
or
electricity;
:a
.- ,
:.
cathode ·1
metal
Prevented .
.,
,
.'
,
''',:
,
. ..
current o r ' e l ; o C t ; C i t y
'.
depends :.
.,,
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TESTING FOR ACIDITY ND ALKALINITY
139. Water from any source is either
ac
id
ic
alkaline
or
neutral.
Litmus
paper
and phenolphthalein and methyl-orange solu
tions are indicators that
do
not show neutral water but can
indicate either acidic
ir
water.
140
. I f blue litmus paper
is
dipped in acidic water, it turns red.
I f
then dipped in alkaline water, the paper turns
once more.
141.
Phenolphthalein solution is colorless and stays colorless
In
ae:idic
water.
I t turns
red when added to water.
142. A drop of methyl-orange solution is yellowish-orange. When
added
to
alkaline water it remains yellowish-orange, but turns
reddish-orange when added to water.
143.
Litmus paper, phenolphthalein and methyl-orange onl y
in
dicate whether a sample
of
water is acid or alkaline.
They do not indicate the degree of acidity or
144. The degree of acidity or alkalinity can be es tablished by
finding a
p
value for a given sample.
p SCALE
, 1 I I I I , , I I I
o
1 2 3 4 5 6 7 B 9 10
11
12 13 14
t - - I . - - - A C I O - - - - t- I - - A L K A L I N E --1
NEUTR L
A sample of water with a p value of 7
is
145. A sample of water with a p value of 5
is
146_
A sample of water with a
p
value of 9.5 ;s
147 . I f you want to increase the p value of the cooling water,
you would add (an acid/ an alkali) .
148.
Water with a high
p
value is (more/less) likely to form
:Sea e than to corrode metal.
149. Water with a pH value
of
9.0 causes red litmus paper to tum
•
150.
Water with a pH of 4.0 causes methyl-orange indicator
to
turn - orange.
151. A sample of water with a p value of 11.3 causes phenol-
:phthalein indicator
to turn
36
alkaline
hlue
alkaline
acidic
alkalinity
neutral
acidic
alkaline
an alkali
rnor
blue
reddish
,
.
red
•
'
.;.
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152 Phenolphthalein in 4.0
pH
water is
_____
153
If
applied excessively,
the
chlorine and phenolic compounds
used as i n f e c t a n t s and algaecides are to
the wood
in
cooling towers.
154.
Excess alkalinity over a long period
of
time
is
damaging
to
cooling tower lumber. Water which is damaging to lumber is
likely to have a (high/low) pH value.
155.
Wood contains organic acids which act to protect
it
from
rotting.
These acids can be washed out by sub-
stances with high pH values.
156.
Excessive chlorine also destroys the natural preservatives in
cooling towel wood .
Excessive
and excessive
should be avoided,
REVIEW AND SUMMARY
157. Water for cooling is (readily available/ scarce) in most areas.
158 Water has the capacity to absorb (more/ less)
heat
than most
available coolants,
•
159.
Water
is (more/ less) costly than other possible coolants.
. Water from natural sources is/is not) corrosive to metals.
Water
has
/ does not have)
scale-forming
'and fouling
tendencies.
162 Water
is non-eombustible and therefore does not add
to
dangers from fire.
It
also responds readily to a large variety of
treatments.
153 Accumulation of suspended solids in cooling water may be
reduced
by
filtration, adding
soft
water,
sedimentation, and continuous from the
system.
164.
In
cloling W81.-.er
the main problem with
hard
water makeup
is that
it
(does not evaporate Quickly/increases scale.fonning
tendencies) ,
165
Lime-soda and zeolite processes are used to ,-
water.
37
. ,
colorless'
high
alkaline
,: .
. .
i i,..\
. .;.":
' ..
" \
. .
·
;
,
"
·
alkaline; < : h l o r i n e
' .
' .
,
,r
·
; j
.
..
' ,:.: "
-..
.
,
•
,,
1
r e a d i l y : a V a i l a b j ~
more
less
IS
has
r
-
s;
t.
"
.
chemical,
r
·fl.
,
f '
makeup
l o w d o w n
'
increases
soften
8/20/2019 Cooling Tower Section 1 API
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166. The
pH
value is
an
expression of (hardn., --softness/acidity
alkalinity) of the water.
167 . Water with a
pH va
lue
of
3.9 is _ _
Water with a pH value
of
7.9 is _
168.
Water with a
pH
value
of
7.0 is _ .
169.
Algae and
sli
me are (mineral / biological) m:-\ter.
170. Algae occurs mostly where water is expo od to (darkness/
sunlight).
171. Algae and slime cause heat exchanger _
172. Coagulation is a process which may be aid
.d
by the use
of
17 . -Coagulation aids (tiltration only
/s
edime, cation only/both
tiltration
and
sedimentation).
. 174. Gases, especially oxygen
and hydrog
. . , sulfide, cause
of metal parts.
175. A process for protecting metal equipmen against electro·
.
, .
chemical corrosion
is pro
t· ction
ITHE END I
•
,
-
acidity-alkalinity
cid
alkaline
nelltral
biological
sunlight
fouling, or cloggin;
chemicals
-
.
both tiltration
and
sedimentation
corrosion
cathodic
. ,
..
-,
_
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