[Mobile Oxygen-Nitrogen Generating Units]
[From the U.S. Government Publishing Office, www.gpo.gov]

Till i°S WAR DEPARTMENT TECHNICAL MANUAL
NON-CIRCULATING
M< OBILE
OXYGEN-NITROGEN
GENERATING UNITS
UAK DEPARTMENT • 14 JANUARY 1944
NTSU LIBRARY

W A R DEPARTMENT TECHNICAL MANUAL
T M 5-355
MOBILE
OXYGEN-NITROGEN
GENERATING UNITS
WAR DEPARTMENT • 14 JANUARY 1944
United States Government Printing Office
Washington : 1944
WAR DEPARTMENT,
Washi ngton 25, D. C., 14 January 1944.
™ 5-355, Mobile Oxygen-Nitrogen Generating Units, is published for the
information and guidance of all concerned.
[A. G. 300.7 (19 Oct 43).]
By orde r of the Secre tary of War :
G. C. MARSHALL,
Chief of Staff.
Offici al :
J. A. ULIO,
Major General,
The Adjutant General.
Dis tri but ion :
X.
(For explanation of symbol see FM 21-6.)
II
Contents
Paragraphs Page
SECTION I. Components of Air. .................................................. *........................................ 1-10 1
II. Liquefaction of Air............................................................................................. 11-12 7
III. Compression......................................................... 13-17 8
IV. Air Purification................................................................................................... 18-22 14
V. Heat Exchangers................................................................................................. 23—29 24
VI. Expansion Devices.............................................................................................. 30-32 31
VII. Rectification......................................................................................................... 33-35 40
VIII. Oxygen and Nitrogen Compression................................................................. 36-38 49
IX. Accessories............................................................................................................ 39-44 56
X. Setting-up and Starting Procedures................................................................ 45-48 59
XI. Oxygen Cylinders........... ................................................................................ 49-51 63
INDEX........................................................................................................................... /.......... 65
hi

Section I
Components of Air
1. PURPOSE This manual is prepared as an
instructional supplement to the Technical Manuals prepared
by the manufacturers of oxygen generating
plants. It describes the oxygen-nitrogen manufacturing
processes of plants made by the Independent
Engineering Company and Air Products Incorporated.
2. INTRODUCTION a. General
There are three methods of producing oxygen for commercial
or laboratory use. They are: first, extracting
oxygen from the air; second, passing an electric current
through water, thus liberating oxygen; and third,
by chemical reactions such as the decomposition of
potassium perchlorate and similar substances (into
oxygen). Of these three processes, the one most commonly
used and also the one adopted for use by the
U. S. Army, is the extraction of oxygen from air.
Before considering this process, it is necessary to
discuss the properties of air and its components.
b. Components of Air Air is composed
primarily of two desirable and two undesirable components.
The two desirable ones are oxygen and
nitrogen. Oxygen constitutes about 20.8 percent of
air, and nitrogen about 78 percent. Two undesirable
components are water and carbon dioxide. In the
following paragraphs, these components will be discussed
in detail.
Figure 1. Semitrailer-mounted oxygen plant (Air Products Inc.).
1
Figure 2. Semitrailer-mounted oxygen plant (Independent Engineering Co.).
3. OXYGEN a. Oxygen as it exists in the air
is denoted by chemists as 02. Oxygen in the air is
recognized as a colorless, odorless gas. In the two
plants described in this manual oxygen exists in both
the liquid and the gaseous form. If the temperature
is low enough, oxygen will liquefy. In the liquid state
it has a slightly bluish color and is a bit heavier than
water. In changing from a liquid at its boiling point
at atmospheric pressure to a gas at room temperature,
oxygen expands approximately 860 times. This tremendous
expansion partially explains the necessity for
careful handling of liquid oxygen.
1*. Some important data on oxygen are shown in
table I. The terms “critical temperature” and “pressure”
are explained in paragraph 11.
4. TEMPERATURE SCALES Degrees
centigrade (°C.) are expressed on a different scale
from that for degrees Fahrenheit (°F.). The following
table gives the corresponding temperatures in
degrees Fahrenheit for temperatures in degrees
centigrade.
Temperature conversion table chart
Degrees centigrade Degrees
Fahrenheit
I
Degrees centigrade Degrees
Fahrenheit
-273_____ ___ -459. 4 -30_______ -22
-270________ -454 — 20_ — 4
—260__. . -436 -10_.._ 14
—250___ . -418 0___ 32
- 240___ -400 5 41
—230_. -382 10___ 50
— 220. ______ -364 15______________ 59
-210 _ _ — 346 20 68
-200____ — 328 25 77
-190___ — 310 40 104
-180___________ -292 45______________ 113
-170___________ -274 50____ ______ 122
-160___________ -256 55______________ 131
-150__________ -238 60____ 140
-140__________ -220 65_____________ 149
-130___________ -202 70______________ 158
-120___________ -184 75______________ 167
-90____________ -130 80___ ________ 176
-80____________ -112 85____________ 185
-70____________ -94 90______________ 194
-60 _ -76 95 ____________ 203
-50________ -58 100_____________ 212
-40____________ -40
2
8 0.0 0 0
7 5,0 00
70,000
65.000
60,0 0 0
55,00 0
50,000
45,000
UJ
UJ 40,0 00
UJ 35,000
30.000
25,000
20.000
15.000
10.000
5,000
SEA LEVEL
FLIERS DIE EVEN IFBREATHING 100% OXYGEN
FLIERS MUST BREATHE 100% PURE OXYGEN
HEIGHT OF MT. EVEREST
FLIERS DIE WITHOUT OX
HIGHEST ALTITUDE IN PLANE
WITH PRESSURE EQUIPMENT
HIGHEST MAN HAS EVER REACHED ANDERSON &STEVENS
1935 IN BALLOON WITH PRESSURE SEALED GONDOLA
FLIERS MUST BREATH
50% OXYGEN
BOILING POINT IS SO LOW
THAT BLOOD BOILS
-66‘
-48c
-30‘ UJ
STRATUS I2‘
6'
59'
25 20 15 10
UJ
tn
oc
UJ
8
LU
tr
ATMOSPHERIC PRESSURE (in inch es of mercury )
Figure 3. Variation of pressure and temperature with altitude.
^BATTLEGROUND TODAY
^STRATOSPHERE BEGINS HERE
LACK OXYGEN
4.BEGINS+O AF
”FECT PILOTS
STRATO
CUMULUS
CUMULUS
FOG AND RAIN
UJ
-67
XIRRUS^
23'
Since the temperature recorder (pyrometer) on the
oxygen plant is calibrated in degrees centigrade, all
further references in this manual to temperature will
be expressed on this scale.
5. NITROGEN a. About four-fifths of the air
persons breathe is practically inactive and of no chemical
value. This portion is nitrogen (2V2). It is not
able to support combustion, to burn itself, or to enter
readily into chemical reactions. Because oxygen readily
combines with substances to form oxides, nitrogen
in the air acts as a diluting agent which prevents too
rapid oxidation or combustion.
I». Nitrogen, as do oxygen and air, becomes a
liquid at a low temperature—about 13° lower than the
temperature needed to liquefy oxygen. Some important
data are shown in table I.
6. CARBON DIOXIDE a. The first of the
two undesirable components in air to be discussed is
carbon dioxide (C02). In dry air away from cities,
the amount of CO2 present is between 0.03 and 0.04
3
ALTITUDE IN FEET
40,000
3 9,000
38,000
37,000
3 5,000 —
3 3,000-
3 2,000
3 0,000
2 9,000
2 8,000
2 7,000
2 6,000
25,000
2 4,000
2 3,000
2 2,000
2 1,000
20,000
19,000-
18,000—
I 7,000-
16,000-
15,000-
14,000 —
13,000 —
12,000
I 1,000
10,000
9,000
8,000
7,000
6,000
5,000
4,000
3,000 —
2,000-
1,000-
SEA LEVEEO
O
O in
in
in
co O
ID
in
o
m* in
ID o
in in
ro
*
O
ro
£
tn
(XI
Note: Altitude is lowered 200 ft for every
1/2 % decrease in oxygen purity
Figure 4. Purity of oxygen required for various flying altitudes without pressure equipment.
oo>
4
percent. In cities the air contains as much as 0.07
percent, while the air indoors may have as much as 0.5
percent.
b. Carbon dioxide is added to the air from two
main sources—the burning of fuel and the breathing
of humans and animals. It is removed from the air
by growing plants which utilize the gas as a food, retaining
the carbon for growing tissue and exhaling
part of the oxygen.
C. As found in the air, CO2 is colorless and odorless;
it has a slight taste. It is not poisonous, but will
not sustain life nor support combustion. This gas will
liquefy readily to a colorless liquid at room tempera- .
ture and at a pressure about 73 times greater than
atmospheric pressure. If the temperature is dropped
to — 56° C. at this pressure, CO2 will freeze into a
snowlike solid known as dry ice. Some important
critical data on this gas are shown in table I.
<1. For our purposes, CO2 is undesirable in the air
for the following reason. Temperatures in the oxygen
plant run as low as —196° C. at atmospheric pressure,
which solidifies the CO2 present in the air. The resulting
dry ice clogs the valves in the air lines. The longer
the plant is in operation, the more solidly CO2 collects
in the valves. Eventually, the plant must be shut
down and then warmed up above the freezing point to
vaporize this material.
e. Since the plant normally operates at about 50
atmospheres, the CO2 will freeze out before the temperature
of the air drops to —79° C. The reason for
this is explained in paragraphs 11 and 12.
Table I. Critical data on major components of air
Oxygen Nitrogen Carbon dioxide
Boiling point______________________
Critical temperature_______________
Critical pressure___________________
Critical density____________________
Molecular weight----------------------------
Specific gravity of liquid at its boiling
point.
Melting point at 73 atmospheres___
Sublimation point at 1 atmosphere, _
— 118.8° C______________
49.7 atmospheres________
0.430 grams per cubic
centimeter.
32______________________
1.143.
-196° C_______________
-147° C_______________
33.5 atmospheres________
0.311 grams per cubic
centimeter.
28______________________
31.1° C.
73.0 atmospheres.
0.460 grams per
centimeter.
44.
-56° C.
-79° C.
cubic
7. WATER a. The other undesirable component
of air in oxygen generation is ordinary water.
There is from 0.01 to 0.02 pounds of water in each
pound of the air we breathe. This water cannot be
seen since it exists as a gas or vapor.
b. Water will freeze at 0° C. or 32° F. Since the
temperature in the plant is so low, the water in the air
is carried into the plant and soon freezes in the lines.
Again, as is the case in a CO2 “freeze-up,” the plant
must be warmed up above the freezing point of water
so that the ice will melt and run out the drain lines.
Several mechanical and chemical methods are used
in the plant to remove most of the water before
the cooling process starts, but complete removal is
impossible.
8. INERT GASES a. In addition to the abovementioned
components of air, there are several almost
insignificant components. There is always present in
the atmosphere about 1 percent of the rare gases—
helium, neon, argon, krypton, and xenon. Argon constitutes
about 0.94 percent of the atmosphere, and is
by far the most abundant of the rare gas group.
These gases are odorless, colorless, tasteless, and
chemically inactive.
b. Some important critical data on these gases are
shown in table II.
Table II. Critical data on rare gas components of air
Parts per million in atmosphere__ _ _ _
Critical temperature_____ _______ ________
Critical pressure (in atmospheres)__________
Boiling point----------------------------------------------
Freezing point_____________________________
Atomic weight_____________________________
Helium Neon Argon Krypton Xenon
5___________
-268° C___
2. 75________
-268. 92° C_
-271. 9° C__
4. 0_________
15__________
-220° C___
29
-246. 09° C_
-233° C___
20. 2________
9, 500_______
-117° C___
52
-185. 86° C_
-188° C___
39. 91_______
CtoO | | Cn | I—‘ 1 ! •
CO C i Cn CO CO 1
i co CO 1 o i
1 ° ■ : P : I I O l l i 1 1 1 1 1
। । Q । । ।
0. 09.
-15° C.
74.
-108. 03° C.
-140° C.
130. 2.
9. SYMBOLS AND FORMULAS OF
CHEMICALS, a. General. The abbreviations
of chemicals and other materials used in the
production of oxygen and acetylene are given below.
563566°—44----- 2
b. Symbols. For convenience, a chemist prefers
to use abbreviations rather than words to name
an element or a compound. Thus, in place of the
word “oxygen” he writes the letter O; for “hydrogen”,
the letter H; and for “nitrogen” the letter N. These
letters are called symbols. Frequently the symbol is
the first letter of the English name of the element foi'
which it stands. Some examples are:
Name of element: Symbol
Oxygen____________________ 0
Nitrogen____________________ N
Hydrogen___________________ H
Carbon_____________________ C
Sulfur_____________________ S
Argon------------------------------------- A
Sometimes two letters are necessary to identify the
element. Some examples are:
Name of element: Symbol
Helium_____________________ He
Neon______________________ Ne
Chlorine____________________ Cl
Silicon_____________________ Si
Aluminum__________________ Al
Krypton____________________ Kr
Xenon______________________ Xe
Some symbols are derived from the name of the
element in some other language. Examples are:
English name Foreign name Symbol
Iron_______ Ferrum (Latin)_______ Fe
Mercury____ Hydrargyrum (Latin)_ Hg
Copper_____ Cuprum (Latin)_____ Cu
Tungsten------- Wolfram (German)____ W
C. Formulas. The chemical abbreviation for
a compound is called its formula. A formula indicates
the kind of atoms that make up the compound
and the atomic proportions in which they are united.
Thus, H2O, the formula of water, indicates that the
water molecule is composed of two atoms of hydrogen
in combination with one of oxygen. Saltpeter is represented
by the formula KNO^, which indicates that
its molecule contains three kinds of atoms united in
the proportion of three atoms of oxygen to one each
of nitrogen and potassium. Each molecule of the
common gases—oxygen, hydrogen, nitrogen, and
chlorine—contains two atoms; consequently the formulas
are written: O2, H2, N2, and Cl2.
10. SUMMARY. The following table gives a
general summary of air and its components:
Components of air and their boiling points
Name Percent Boiling point
(° C.)
Boiling point
(° F.)
Liquid air 100 —194 317
Nitrogen 78 —196 — 320
Oxygen 21 —183 297
Argon . 95 —186 303
Neon . 0015 — 246 411
Helium______________ . 0005 -269 -452
Krypton____________ . 0001 -153 -244
Xenon_______________ . 000009 -108 -162
G
Section II
liquefaction of Air
11. CRITIC AU TEMPERATURE AND
PRESSURE ;i. General Two important
steps must be taken before air can be converted from
the gaseous to the liquid state. These steps are
compression and cooling,.
b. Compression A cubic foot of a liquid is
heavier than a cubic foot of a gas, because in the
liquid state the particles are close together. Hence,
the first step in liquefaction is to crowd together the
particles of a gas. This step is known as compression.
It seems, off hand, that if enough pressure were put
on a quantity of gas, the particles would be forced
close enough together to form a liquid, but this is not
altogether true. It is known scientifically that gas
particles move so fast that they will not stick together.
The only way to slow down their speed is to reduce
the temperature.
c. Cooling If the temperature is reduced low
enough, the gas particles will keep together and will
go into the liquid state. The temperature required to
slow down these particles sufficiently is known as the
critical temperature. In other words, the critical temperature
is the highest temperature at which a gas will
liquefy. The critical pressure is the minimum pressure
necessary to turn a gas into a liquid at the critical
temperature.
<1. Critical factors It must be borne in
mind that pressure alone will not cause a gas to liquefy.
Unless the temperature is below the critical point, no
amount of pressure will cause a gas to liquefy. Some
gases, however, have a high critical temperature.
For instance, CO2 will liquefy at room temperature
(31.1° C.) if the pressure is high enough. The following
table gives the critical temperature of some common
gases with the accompanying pressures:
Name Critical
temperature Critical pressure
Degrees C. Atmospheres
Air_______________________ -140. 7 37. 2
Oxygen---------------------------- -118. 8 49. 7
Nitrogen_________ ________ -147. 1 33. 5
Carbon monoxide_________ -139. 0 35. 0
Carbon dioxide + 31. 1 73. 0
Argon_ —122. 0 48. 0
Helium___________________ -267. 9 2. 26
12. INTRODUCTION TO OXYGEN
PRODUCTION. In producing compressed oxygen
by the mechanical separation of air, six fundamental
steps generally are involved. These are:
compression, air purification, liquefaction, expansion,
rectification, and recompression. The exact methods
by which these steps are accomplished often may vary,
depending on the kind of oxygen plant used; also, commercial
methods frequently differ radically from those
used in mobile oxygen generators. Several different
mobile plants have been manufactured and tested, but
in this manual only two different makes are discussed.
One is made by Air Products, Incorporated, and the
other by the Independent Engineering Company.
These are the only generators in use in the armed forces
at the present time. The fundamentals of production
of these two are the same, but there are important differences
in the methods of accomplishing the steps
listed above. In this manual the one plant will be
referred to as the Air Products plant and the other as
the Independent plant.
7
Section III
Compression
13. AIR COMPRESSOR a. Before entering
the compressor the air passes through an air filter
designed to remove dust, leaves, sand, or any other
foreign matter. This filter is essentially a layer of
steel wool containing a thin film of oil. It can be
removed and cleaned easily when necessary.
1*. rhe compression is accomplished by one or more
three-stage compressors. The air is compressed in
one cylinder to a certain pressure, discharged into
another cylinder for compression to a higher pressure,
and then into the third cylinder for compression
to the final high pressure. This final pressure is commonly
known as the “head or operating pressure.” A
single large cylinder and piston could be used to develop
the same pressure, but in a mobile plant this is
not desirable. For one reason, it would require large,
bulky machinery. Figure 5, a diagram of the flow of
air through a three-stage compressor, gives a simple
picture of the mechanisms involved.
C. When air is compressed its temperature rises
considerably. It is compressed three separate times
in going through the compressor; and it is necessary
to reduce the temperature after each step to prevent
mechanical difficulties such as expansion of the metal,
which would cause the parts to “freeze.” Excess
temperature also causes the oil in the cylinders to
“crack” and deposit carbon, which is a common
source of valve trouble.
INTER - COO LI NG COILS
SAFETY / \
AIR FILTER A VALVE / A \ A \ (7~- -
TIt TO TTil/OTT F"
AIR IN J| I L \\ । _ \\ni y
J.---LEpLsCHARGE I—r^'Tl /TX DRAIN
INTAKE ' VALVE 1 — Vf VALVE
BLOW VALVE TT I |
BACK
“I o.j — h/l-j? LL
„ _ _ BEARING — J Lt or U Lot 1 Y- y CRANK-SHAFT
1ST STAGE 2ND STAGE 3RD STAGE
FLYWHEEL
Figure 5. Flow through a three-stage compressor.
n
<1. Intercooling coils, submerged in a water bath,
are used to reduce the temperature of air after each
stage. This action often is known as removing the
heat of compression. The water surrounding these
coils flows around them and picks up the heat of
compression; in the Air Products plant it is cooled
in a radiator. In the Independent plant it is cooled
in an evaporative condenser.
e. In the Air Products plant the air is compressed
by a single three-stage vertical Nordberg compressor.
This compressor is capable of delivering 5,500 cubic
feet of air per hour under a pressure of 3,000 pounds
per square inch. The crankshaft speed is approximately
300 rpm. Cylinder lubrication is accomplished
by a Manzel force-feed lubricator. It is simply
a pump arrangement in which oil is forced through
a bath of thick, clear substance, usually glycerin, into
a line to one of the stages of the compressor. There
are three such baths and three lines, one to each
stage. As the drops of oil are forced through the
Figure 6. Nordberg three-stage vertical air compressor.
bath, they are easily visible and can be counted. This
makes it easy to regulate the lubrication. It is important
that the right amount of oil be fed to the cylinders,
for too much oil may cause unnecessary carbon
deposits and load the air stream with oil vapors to be
carried into the heat exchangers and column. A
desirable oil schedule is as follows:
First stage--------------- Two drops per minute.
Second stage_______ Two drops per minute.
Third stage________ One drop per minute.
f. In the Independent plant, air is compressed by
five three-stage V-type Curtis compressors, each delivering
about 1,250 cubic feet per hour at a pressure
of 800 pounds per square inch. One respect in which
Figure 7. View of Curtis three-stage V-type compressor.
IO
this compressor differs from the Nordberg is that it
has two first-stage cylinders which discharge into the
second stage. Both compressors, however, have single
second and third stages. For feeding oil to the cylinders,
the Curtis compressor has an oil pump which
operates at a pressure of from 20 to 30 pounds per
square inch; this pressure, rather than the sight-feed,
oil-drop method, determines proper regulation. The
lubrication and maintenance problem with these small
compressors is relatively much greater than with the
single Nordberg; for each Curtis compressor has 4
cylinders and pistons, each with 2 valves and valve
springs. Hence the 5 compressors together have 20
cylinders and pistons and 40 valves and valve springs,
compared to the 3 cylinders and pistons and 6 valves
and valve springs in the Nordberg compressor. The
Curtis compressors are powered from a line shaft
which is propelled by an RXLD Hercules engine which
delivers 110 horsepower. Each compressor has its
own clutch; hence, if there is a break-down, it can be
disengaged for repair.
14. COMPRESSOR RADIATOR The water
in the compressor bath of the Air Products plant
is cooled by a large radiator. As the water picks up
the heat of compression from the cooling coils, it rises
to the top of the bath and flows out the line to the
radiator. Hence it passes through the honeycomb fins
of the radiator and is cooled by a strong blast of air
pulled through by a large fan, which is propelled by
a pulley connection to the engine shaft. After circulating
through the radiator and being cooled, the
water enters a water pump and is sent back to the
bottom of the compressor bath. Here it is again
ready for circulation.
15. EVAPORATIVE CONDENSER a.
The evaporative condenser is a more complicated piece
of equipment than the radiator. The warm water
leaves the water jacket of the five compressors and
enters a water pump which forces it first through a
radiator, then to a coil immersed in a cool water bath,
Figure 8. Radiator, fan, and water recirculating pump (Air Products plant).
Il
Figure 9. Evaporative condenser, showing sprays and blowers (Independent plant).
12
and finally back to the compressor water jackets for
use once again.
I*. After the water in the bath has absorbed the
heat from the compressor water, it is forced by another
pump through several water sprays located directly
beneath two fans whose draft of air causes evaporation
in the sprays. This evaporation cools the water. The
water in the evaporative condenser bath must be
checked, and, the bath filled once or twice a day,
depending on the climate.
C. A large amount of water in the air is not desirable
when running an oxygen plant, for water
freezes quickly in the main air stream at the low temperatures
within the plant. Chemical absorbers are
provided to remove this water. Any water above the
normal amount in the air throws a burden on these
absorbers.
16. FLASH POINT OF OIL a. A special
oil, known as high flash-point oil, is used in the Nordberg
compressor. The oiling system in this compressor
is such that the oil fed to the cylinders is only the
amount necessary for lubricating the pistons and
valves during the time interval between drops from
the oiler. This oil is subjected to high temperatures
on the cylinders of the compressor. Ordinary oil
under a temperature of approximately 300° F. undergoes
a chemical change known as “cracking”; it is
converted into carbon and several gases.
I>. Standard oils are used in the air compressors
and the oxygen compressor crankcase of the Independent
plant because the discharged air temperatures
are not high enough to break down the oil. However,
a special oil with a flash point in excess of 450° F. is
used in the Air Products plant, because the discharge
air temperatures are high enough to crack standard
oils. An oil’s temperature of decomposition is known
as its flash point.
C. A simple emergency test for determining the approximate
flash point of an oil is as follows. A sample
of about 2 ounces is placed in a crucible or some other
container and heated, as shown in figure 10. Then
the oil is stirred constantly with a stirring rod, its
temperature being measured continuously by a thermometer
registering as high as 400° F. As the temperature
rises to about 200° F., a small flame from a
match or some other source is held a few inches above
the hot oil. This is done for every few degrees of rise
in temperature until the vapors rising from the oil
begin to spark or ignite in small explosions. The
temperature at this point is recorded as the approximate
flash point. An oil with a flash point below
350° F. deposits excessive carbon in the compressor
and hence is a source of trouble.
400° F
THERMOMETER
fn
Figure 10. Apparatus for testing the flash point of oil.
17. WATER TRAPS a. After the air has
been compressed in the compressors, a considerable
quantity of water appears. The tiny particles of water
vapor in the air also have been compressed, or brought
in close contact with each other so as to form deposits
of water. This water must be removed before the air
is cooled prior to liquefaction; otherwise, ice forms
inside the small tubes of the heat exchangers and clogs
the lines. The force of expansion when the water
freezes may even split the tubes.
1*. The first step in removing the water is by use
of cylindrical traps. The air usually comes in at the
side, takes an upward turn, and goes out at the top,
leaving its water behind it. The reason the water is
left is that it is too heavy to take the sudden turn;
instead, it drops down to the bottom of the trap and
is drawn off by a valve. There are many modifications
of this particular type of trap; however, they all embody
the same fundamental principle that water is
heavier than air. It is emphasized that this trap can
be used to remove only water in the free state, or, in
other words, water that is liquid. Water in the gaseous
state—and there will be some of it—must be taken ®ut
by other means.
563566° 44------ 3 13
Section IV
Air Purification
1«. GENERAL PURPOSE a (1) As pre
viously mentioned, air contains two desirable and two
undesirable components. The purpose of air purifiers
is to remove the undesirable ones. Unfortunately as
the air goes through the compressor, it picks up a third
undesirable component, oil; some of the lubricating
oil is carried along with the air stream. Obviously,
this oil must be removed before it passes into the
heat exchangers and column, for oil in the presence
of pure oxygen burns violently or even may explode.
The respective effects of oil, water, and carbon dioxide
in the purifiers are as follows: oil, in the presence of
oxygen, causes explosion; water freezes in exchangers
and may split tubes; carbon dioxide turns into dry ice
and clogs expansion valves.
(2) There are many different methods of removing
these components. The methods used in the two
mobile plants, though suitable for this type of equipment,
are not entirely feasible for commercial use
because of cost of chemicals and manpower.
I*. In both plants oil is removed by mechanical
separation, that is, by traps employing some means
of preventing the oil particles from passing along
with the air stream. Carbon dioxide is removed by
a chemical reaction with either caustic soda or caustic
potash. Caustic soda, or lye, as it is commonly known,
is denoted by chemists as sodium hydroxide (NaOH).
Caustic potash is very similar to lye and is referred
to as potassium hydroxide (KOH). As it reacts with
caustic soda the carbon dioxide forms sodium carbonate,
which is simply washing soda. The chemical
equations for the reaction of carbon dioxide with
sodium hydroxide and potassium hydroxide are as
follows:
C. Water is removed to a very low dew point by
mechanical means and chemical absorption. As was
co2 + ZNaOH --> Na2COs + h 2o
Carbon
dioxide
Caustic
soda
Sodium
carbonate
Water
co2 + 2 KOH --» K2COS + H2O
Carbon
dioxide
Caustic
potash
Potassium
carbonate
Water
explained in section III, water traps remove considerable
free water. In addition, the air is forced
through a cylinder containing a chemical known as
silica gel for absorption of water vapors to a low
water content of approximately —60° C. dew point.
What is meant by the term “dew point”? This is
simply the temperature at which water vapors begin
to condense from the air. Air with a dew point of
60° C. would have to be cooled to that temperature
before one drop of water would appear on the surface
of its container.
19. CAUSTIC SCRURRING TOWERS
a. In the Air Products plant carbon dioxide is removed
by allowing the air stream to come in contact
with a countercurrent spray of caustic soda solution.
Chemists have found that the reaction between carbon
dioxide and caustic solution is more complete at higher
pressures; therefore, the scrubbers are designed to operate
at a pressure which will help the chemical reaction
but will not require too heavy equipment.
I». Air is introduced into the compressor through
an air filter and is compressed to 75 pounds in the first
stage; then, instead of going into the second stage, it
enters the first caustic tower under pressure. It enters
the lower side just above the level of caustic solution,
as shown in figure 11, and rises through the tower,
which is packed with stainless steel “curls.” A curl
is simply a strip of steel about 1 inch wide, which provides
a good surface contact between the air and the
caustic solution, which descends on the curls in sprays.
After leaving the first tower, the air enters the lower
side of the second tower and rises through similar
packing against caustic sprays. After passing the
sprays, the air enters a chamber on top of the second
tower, also filled with “curls.” This chamber is designed
to remove any entrained particles of caustic
solution. Next, the air leaves the towers and enters
a simple water trap for further removal of entrainment.
C. The caustic cycle is very simple. Fifteen pounds
of flake caustic soda is added to 22 gallons of water in
the caustic mixing tank, as shown in figure 11. This
mixture is then pumped into the two receptacles at the
14
bottom of the tower. Next the mixing tank is closed
off by valves and the caustic pump started. The caustic
solution enters the pump from lines beneath the
towers. It is then pumped simultaneously to sprays in
each tower whence it drops down through the packing
and again into the liquid chambers at the bottom of
the towers, where it is drawn off for recirculation.
20. HIGH PRESSURE REMOVAL OF
OIL, CARBON DIOXIDE, AND WATER
*1. The high-pressure air purifiers used in the Independent
plant consist of four large cylinders, as shown
in figure 12, fitted with screw caps on both the top and
bottom. These cylinders are connected in series, the
air, in each case, entering at the bottom of a cylinder
CARBON DIOXIDE AIR OUT
AIR + CARBON DIOXIDE IN
‘ I' It
Ay + I
ie a « 6 o/0 I si A”/o 8 ia>\ | t t n t y
PACKING_________ e 4 7CJ e« > % /*' ’ | AA ° V _______ CAUSTIC
RINGS e€®effee e e e e M | l^'V 1° SPRAYS
p e e e ® ®«ee ® a o e ® % e % e, ® e Q ,eG 1 aa pJ ®G '* °a ®„ pe %°
"_*_—________ 4 ^°k Vo4L’ ee *a®4 t %°o* e° ® ®,$><“» et *-e > «•e >® a> Se S®® V®<.
„G< O®e>o&„* Tape ®en. se°es tA ®o a®" 'e“e a *’ 60 IpL ' f®«l > t1J ,1 4* 4 6G a t* 6 as® 1lLa M®°G *eIoe '
o 1 a ® ® e £ e e< Jee »a T e|e.Je’ « « t ® Is
ejC.e/fO6,elG,®e|e',3,lfiG । ®
-—l = zl= -!--)= zz------------------- SCREENS
CAUSTIC ----- J / / / / x V x I----- --------
SODA ------ =T* "i----- -----------
SOLUTION-----------------------------------------------------------------------------
MIXING TANK _Z ZZ____ — ------------ ------- -
__ 1 ~Z CAUSTIC SODA
— ---------- ---------- -------- ----------- SOLUTION
CAUSTIC
RECIRCULATING .
PUMP \
c
CARBON DIOXIDE SCRUBBERS
Figure 11. Caustic scrubbing towers showing caustic lines and recirculating pump (Air Products plant).
15
IG
- SECOND
Cyli nder
DRAIN r.
VALVES^
REMOVES
OIL
‘FIRST
CYLINDER
FOURTH
CYLINDER (THIRD '
cyl inder
i
| re move s ’ ■
|co2 a HgO.
REMOVES
co2
CONTAINS
SILICAGEL
i jCONTAINS
HCAUSTIC
Hl POTASH
CONTAINS
CAUSTIC
POTASH
Figure 12. Air-purifying cylinders (Independent plant),
CONTAINS
BROKEN
ROCK
REMOVES
0 PURIFYING *^0^ 2
MATERIAL O
I < < < I
J/4"DIA r/zXtz/Li «'^W///AV///^W/A
qifv r A (7 - i r TO DRAIN
\S,EVE valve
\ WF
|1 Z gj—RUBBER GASKET
; yy
Figure 13. Bottom section of air-purifying cylinder (Independent plant).
and leaving at the top. At the bottom of each cylinder
is a drain line equipped with a valve, so that any
liquid collecting in the cylinder during operation can
be withdrawn. To prevent, or help to prevent, the
drain valves from clogging, two metal sieves are located
in the bottom of each cylinder; they tend to prevent
the solid purifying agent in the cylinder from
getting into the drain line and valve. The drawing of
the bottom section of the air-purifying cylinders reveals
the detailed construction.
!»• (I ) The first cylinder is designed to remove
oil from the air stream. It is filled with a porous substance
having a large area of contact with the air.
Usually, this substance is nothing more than crushed
rock, commonly called rock chat. The oil, as it comes
in contact with the rock, sticks to the ragged surface
and goes into its pores. The more surface available,
the more oil is removed. Hence each individual rock
should be small, but not so small as to go through
the metal sieve at the bottom of the cylinder and clog
the drain valve. Rocks %-inch thick are about right,
as the diameter of the holes in the sieve is *4 inch.
A rock or stone which pulverizes easily should not be
used if something else is available. Nor should hard,
smooth stones and rocks be used, for their surfaces
are so slick that the oil, instead of staying on the surface
and filling the pores, flows on. Pebbles found
in shallow streams are of this type and should not be
used when something better is available.
(2) When the supply of the right type of rock is
scarce, the rock chat in the cylinders can be reused
many times, but after the first time it does not do so
good a job, and throws some of the burden over to
the second cylinder. The rock chat should be removed
each week, washed with a stream of water, and then
spread out over a large area to dry. The drain valve
should be opened at least once every half hour to
allow any oil accumulated in the bottom to flow out.
17
C. (1) The second and third cylinders are designed
to remove carbon dioxide and some water.
They are filled with walnut-size lumps of caustic
potash, or, in chemical language, potassium hydroxide
(KOH). As mentioned previously, it has almost the
same properties as common lye. It reacts with the
carbon dioxide to form potassium carbonate and water.
When put into the cylinder the walnut-size caustic is
a very dry solid. Dry caustic is practically unreactive,
and will not remove carbon dioxide. However, enough
water comes over from the water trap and past the
first cylinder to moisten the lumps of caustic, a thin
film of water forming around each lump. In this condition
the caustic is very reactive and readily combines
with the carbon dioxide. Also, as the equation for
the chemical reaction shows, some water is formed
during the removal of carbon dioxide.
(2) Besides reacting with carbon dioxide, caustic
potash absorbs large quantities of water from the air.
A lump of caustic placed in a receptacle in the open
room and left standing for a day absorbs enough
water from the air to be completely dissolved itself.
This property helps to explain the purpose of the third
cylinder and the fact that it is filled with the same kind
of caustic as the second cylinder. It removes the
water formed during the chemical reaction in the second
cylinder and also some of that which came over
from the water trap on the compressor. When the
caustic in the second cylinder is low, the third cylinder
acts as a spare to remove carbon dioxide.
(3) The second and third cylinders must be
drained with great care. As the caustic reacts and dissolves
in the presence of water in the air and water
from the chemical reaction, it settles to the bottom of
the cylinder. Potassium carbonate and small lumps
of caustic settle with it, and a heavy sludge results.
When this is drained out, occasionally solid particles
clog the valve. Since during normal operation the
cylinder is under approximately 800 pounds pressure,
the sludge should come out through the drain line
with considerable force when the valve is opened.
Hence, when the valve and line are clear, a hissing
sound can be heard near the valve. If this distinctive
sound is not heard, probably the valve and line are
clogged. The best way to free the valve and line is
to remove the valve and free the passage with a wire
or some other suitable object. Be sure, however, to
shut down the compressor and relieve the pressure first.
In extereme emergencies a torch can be applied to the
valve to melt the caustic and free the passage; but this
must be done only with great care, for it results in a
sudden release in pressure which not only disrupts the
column operation, but may rupture the screens in the
fourth cylinder. These screens are discussed in d
below.
(4) The caustic in the second cylinder should be
removed once a week and spread on a flat surface, the
largest lumps being recovered and replaced in the
cylinder, the small ones and the sludge discarded.
The cylinder should be filled with new caustic up to
the point where the cylinder begins to taper down.
Usually it is not necessary to change the caustic in
the third cylinder, for the sludge formation in it is
not very great; instead, new caustic should be added
to the top of the cylinder as the old is used. In humid
climates, where caustic dissolves readily in both cylinders,
a desirable practice is to empty both cylinders,
discard the contents of the first, place the residue of
the second in the first, and then fill both to the top with
new caustic.
<1. ( 1 ) The fourth cylinder is designed to remove
water to a point where the amount in the air stream
will not affect seriously the operation of the plant.
It is filled with a material having a high affinity for
water. The substance which has been adopted for use
by the Corps of Engineers is silica gel, a clear, crystalline
material which will absorb approximately 50 percent
of its weight in water from saturated air. The
silica gel particle contains numerous small pores which
tend to drink in the water from the air by capillary
action. Estimates have been made that 1 cubic inch
of silica gel has a surface of about 50,000 square feet.
(2) This cylinder dries the air enough that the
water is only about 2 pounds per million cubic feet
of air. This seems like an insignificant amount, but
over a period of time enough water collects in the heat
exchangers to retard the air flow. This usually takes
about 3 days. A spare set of exchangers is provided
for freeze-ups.
(3) The silica gel left in the cylinder is usually
good for 1 week’s operation. If, however, after it has
been removed, the silica gel is still a telltale blue, reactivation
is not necessary. In extremely hot weather
there is a great deal of water in the air, and the silica
gel gets wet much faster than in colder weather. This
should be considered when operating in torrid regions.
In hot climates the greater percentage of water in the
air causes the caustic in the second and third cylinders
to dissolve much faster. Therefore, they must be
checked more frequently.
(4) The fourth cylinder, like the other three, has
a drain valve which is opened about once every half
hour. This time interval depends, however, on the
amount of water in the air. The valve tends to leak,
since the small pulverized particles are deposited on
the valve seat and prevent the valve from closing
entirely. The valve stem must be removed occasionally
and the seat cleaned. Two fine-mesh screens, with
a piece of felt between them, are located at the bottom
of the cylinder, on top of the metal sieve, to prevent
the fine particles from settling down to the drain line.
There is the same arrangement of screens and felt on
top of the cylinder. This prevents the silica gel dust
from passing over into the heat exchangers with the
air stream. When inserting these screens into the cylinder,
care must be taken to prevent any wrinkles
18
which would allow the fine particles to get by. As an
extra precaution a burlap sack, or some other similar
material, can be placed in the cylinder in addition to
the screens.
(5) The draining or “blowing-down” of the
fourth cylinder should be a fast operation, to prevent
a sudden drop in pressure. Since there is very little
free water to be drained, this operation is not very
important. If the pressure drops suddenly, the water
absorbed inside the particles of silica gel vaporizes, or
expands and ruptures, or disintegrates the silica gel.
This action is largely responsible for the formation of
tiny particles and dust which clog the valve.
21. SILICA GEL REACTIVATOR, a.
Since silica gel is a critical material in the theater of
operations, it cannot be thrown away after it has become
wet in the drying cylinders. Instead, it is put
Figure 14. Silica gel reactivator.
If>
AIR IN (WET)
i- 1=0------------------I
If- -—=s > -f
, NITROGEN IN
( DRY )
AIR AIR
DRYER DRYER
NO. I NO.2
IN BEING
OPERATION DRYED
ELECTRIC
HEATER
( i NITROGEN I
------------------- f\Zj-------------------- ------------------f)------------------ 3Z BYPASS TO
’]-------------------O------- 1 --------------------------------O-------------------- HEATER -''f-f
<----- 0 U --.. ^■---0 -I I
Fl I’ NITROGEN FROM LJ~ \
< -- HEA■ T EXCHANGER --"----------- -
NITROGEN OUT (WET ) 0
---------------------—-----------------------<|
------------------------------------------------------------------III NITROGEN EXHAUST
SILICA GEL DRIERS
Figure 15. Regenerative driers, schematic, showing air and nitrogen lines (Air Products plant).
into the reactivator and dried, about 50 pounds being
placed in the chamber at a time.
I>. The construction of the reactivator is simple.
Basic are a chamber and a cap for the same containing
five 500-watt electric heaters. Around the cap are
several holes, or air ducts. Underneath the chamber
are an electric motor and a fan. The fan draws the
air through the air ducts, past the heater where it is
warmed, and then through the silica gel and out the
bottom oi the reactivator. In going through the
20
M B
Figure 16. Regenerative driers, side view showing nitrogen by-pass and nitrogen manometer (Air Products plant).
563566°—44---- -4 21
figure 17. Regenerative driers, front view showing air and nitrogen lines and electrical connections (Air Products plant).
22
silica gel, the hot air picks up the water, leaving the
silica gel dry once again and ready for use. The
reactivator will dry 50 pounds of silica gel containing
10 percent moisture, in 3 hours, or 50 pounds containing
20 percent moisture, in 5 hours.
C. A general rule in operating the reactivator is to
run it until the temperature on the thermometer, which
is located on the front, shows 300° F. Then remove
the cap and see if the silica gel is telltale blue. Under
no condition should the temperature of the reactivator
rise above 450° F. If it does, the silica gel disintegrates.
After reactivation, the gel contains about 2
percent moisture, and is suitable for further use.
22. DEHYDRATING HEAT EXCHANGER
AND REGENERATIVE
DRIERS a. The process of water removal discussed
in this paragraph applies specifically to the
Air Products plant. After leaving the third stage of
the compressor, the air enters a water trap and then
passes into a unique piece of equipment known as the
dehydrating heat exchanger, the principle and construction
of which is outlined in section V. However,
the function of the heat exchanger is very simple.
The temperature in the dehydrating exchanger is maintained
at just a few degrees above 0° C. The air
passing through it is cooled to this temperature and
passes on, but the water vapor begins to condense and
is drained away. When air is cooled its ability to
carry water vapor is lowered.
b. At 0° C. water vapor in the air freezes into ice;
therefore the dehydrating exchanger should operate
just above 0° C., so that water will condense from the
air but will not freeze and clog the exchanger. The
water content of the air leaving the exchanger is said
to correspond to a dew point of slightly above 0° C.
If allowed to come in contact with the low temperatures
in the other heat exchangers, air containing this
amount of water would deposit ice very quickly and
clog the air lines. For efficient operation the water
should be removed to a dew point of approximately
— 60° C.; therefore the air is sent through a cylinder
containing silica gel. The characteristics of silica gel
have been thoroughly discussed in paragraph 20.
C. The method of using silica gel in this plant differs
considerably from that used in the Independent
plant. Figure 15 shows the flow of air through the
drying cylinder and the regenerative principle. There
are two identical silica gel cylinders, between which is
located a 2-kiIowatt heater. The air enters at the top
of the cylinder in operation and leaves from the bottom.
After a time the silica gel absorbs enough water
to become saturated, and in this condition it is no
longer useful. At such times the air is transferred
to the other cylinder for continued drying, and the
wet cylinder is dried out or regenerated for use once
again. The waste nitrogen from the plant is used to
dry the silica gel. Certainly this nitrogen is dry, for
it comes from the rectifying column where it boiled
away from liquid air at a temperature of —192° C.
In such air there could have been no appreciable
amount of water in the gaseous state; therefore, the
nitrogen which left it must be dry.
<1. To increase the absorbing power of nitrogen in
its dry condition, it is passed over a strip heater which
operates at a 2-kilowatt power input. After being
heated the gas is passed into the wet silica gel cylinder
and released to the atmosphere. There is an automatic
time clock for the heating element. Usually this clock
is set for 4 hours, which means that after 4 hours the
current is automatically shut off and the heating
process discontinued. There is also provided a thermometer
to indicate the temperature inside the cylinder.
Then, too, there is a thermostat which will throw
the switch automatically, if the temperature gets too
high. The temperature usually ranges around 300° F.;
it should never rise above 450° F.
e. After it has dried, the air is sent on to the heat
exchangers. The oil from the compressor, which is
almost insignificant in amount, is removed in the
caustic towers, in the several traps, and in the dehydrating
heat exchanger. The great advantage of this
air drier is its semiautomatic regenerative feature.
After the silica gel in the Independent plant gets wet,
the large cylinder must be uncapped and drained to
remove the gel. This requires shutting down the
plant. The 100 pounds in a cylinder must be reactivated
in 50-pound lots in a separate silica gel reactivator
heated by an outside current. An Onan 3-kva
electric generator is usually connected to furnish the
needed electrical power. In the Air Products plant
no extra equipment is necessary; nor is it necessary
to change the silica gel once it gets wet.
23
Section V
Heat Exchangers
23. GENERAL PURPOSE AND CONSTRUCTION
As mentioned in paragraph 11, in
the liquefaction of air two important steps must be
taken: First, compression, and second, cooling. The
method of compressing air has already been discussed.
This section deals with cooling.
a. When any substance is cooled, whether solid,
liquid, or gas, the drop in temperature is effected by
contact of the substance with some colder material.
Generally, in the oxygen plant the air is cooled by contact
with cold nitrogen and oxygen. Probably the
first question that arises is, “Where do we get the
nitrogen and the oxygen?” They come directly from
liquid air in a piece of apparatus known as the rectifying
column. The air entering the system does not
come directly in contact with the nitrogen and oxygen,
but rather with the pipes containing them. Each gas
flows through a separate pipe or tube of different sizes,
usually arranged so that one may fit inside the other.
A simple apparatus illustrating the principle involved
would be one with a tube containing air flowing around
an inside tube containing cold oxygen, the air tube in
turn being contained in an outer tube containing cold
nitrogen. As the air flowed through them, both oxygen
and nitrogen would exchange their refrigeration
for the air’s heat.
b. The object of the heat exchangers, therefore, is
to allow the cold oxygen and nitrogen to absorb the
heat from the incoming air so that the temperature of
the air, after it has passed through the exchangers,
will be very low, around —80° C., and the temperature
of the oxygen and nitrogen, as it leaves the exchangers,
will be almost that of the entering air. If these conditions
are fulfilled, the exchangers are said to be
efficient. A heat exchanger usually has a large number
of tubes through which the gases pass, in order
to provide a large area of contact between the oxygen
and nitrogen on the one hand and the air on the other.
Three or four hundred 14-inch tubes in an exchanger
is not uncommon.
C. Since the equipment in a mobile plant must be
compact, two or three small exchangers, connected in
series, are used instead of a single long one. A set of
three exchangers is referred to as a bank of exchangers.
After about 3 days, depending on the amount of water
in the air, the exchangers in the Independent plant
freeze. When this occurs, the air cannot pass, and it
would seem the plant would have to be shut down.
But there is a spare bank of exchangers to take care of
this difficulty; when one bank freezes the air can be
sent into the other, and the oxygen and nitrogen
streams are accordingly switched.
24. FREON PRECOOLER a. Since the
temperatures required for producing oxygen are very
low, considerable time is required to lower the temperature
of pieces of equipment such as the heat exchangers,
rectifying columns, valves, etc. The time required to
cool the Independent plant and start production, for
instance, is approximately 6 hours. In the Air Products
plant the designers incorporated the freon heat
exchanger as one of the three used. This, combined
with skill in the design of the cold section of the plant,
makes it possible to cool down from 25° C. and produce
oxygen at a purity of at least 99.5 percent in a period
of hours.
1>. There are three fluids in the freon exchanger:
High-pressure air, low-pressure cold nitrogen, and
freon. The air enters the exchanger at a point approximately
two-thirds of its height and flows in small copper
tubes down around the center tubes, which contain
nitrogen. The nitrogen rises in the center tubes countercurrent
to the flow of the air. The freon flow is
controlled by an automatic thermal expansion valve.
The liquid freon from the freon condenser, under a
pressure of approximately 120 pounds per square inch,
is forced upward through a tube alongside the condenser
to the automatic valve. The freon expands to
a pressure of approximately 0 pounds per square inch,
gauge pressure, and in so expanding cools to approximately
—40° C. This valve is designed to provide
the necessary amount of freon flow, regardless of variations
in the refrigeration load. The freon leaves the
valve and is wound around the upper third of the
nitrogen tubes. From the top of the nitrogen line, the
freon tube turns back to the very bottom of the exchanger
where it discharges the freon as a liquid.
The latter fills the inside of the exchanger up to the
air inlet and automatic thermal expansion valve. The
24
NITROGEN INLET
(COLD)
NITROGEN OUTLET
(WARM)
Figure 18. Heat exchanger {Independent plant).
OUltf"
= ==m J L I F = =
w—j 0l.f 1*i1J iUi —]__ AIR OUTLET i— u| ," r I ,* *T M_□ —(COLD)
1 I 0XYGEN inle t
C I “Z"l (COLD) 1111F
MW
OXYGEN OUTLET
(WARM)
AIR INLET
( WARM)
valve tends to maintain the level of freon at this height.
As it gives up its refrigeration to the warm air, the
liquid freon vaporizes and rises through the upper
part of the exchanger to a discharge line which sends
the gaseous low-pressure freon to a compressor. Here
the freon again is compressed to 120 pounds per square
inch and passed through a radiator type condenser,
where the heat of compression is removed. Upon being
cooled, the freon turns into a liquid and is drained
to a cylindrical receiver for use again in the exchanger.
25
C. The freon system requires little maintenance.
The compressor and the condenser fan lubrication
must be checked once or twice a day. Water must
be kept at the proper level in the condenser. Also
the freon pressure must be watched. A decreasing
pressure indicates loss of freon. If this occurs, freon
can be added to the system by connecting a cylinder
of freon to the inlet valve on the silica gel freon dryer.
The gas, under pressure, passes through the silica gel
and enters the system.
25. FLOW OF FLUIDS—AIR PRODUCTS
PLANT The flow of gases through the exchangers
of the Air Products plant can best be followed
by studying figure 19. The two regular exchangers
used to cool the air to a low temperature of
approximately —80° C. are designated on the diagram
as “Air, O2, N2, heat exchangers.” There are only
]4 tubes in this particular type of exchanger, 7 small
tubes inside of 7 larger ones. The high-pressure
oxygen passes through 6 and the nitrogen through
TO
AIR OUT
AIR IN
PURE NITROGEN OUT
AIR BYPASS
TO SILICA
GEL DRIERS
TO SILICA
GEL DRYER
LOW PRESSURE
OXYGEN OUT
DRY AIR IN
FROM SILICA GEL DRYER
THERMAL
EXPANSION
VALVE
LIQUID HIGHPRESSURE
FREON FROM
RECEIVER
DEHYDRATING
HEAT
EXCHANGER
CRUDE
NITROGEN OUT
FROM COMPRESSOR
FREON
COMPRESSOR
AIR , OXYGEN,
NITROGEN HEAT
EXCHANGERS
FREON
HEAT
EXCHANGER
AIR OUT
TO BOILING COIL
PURE NITROGEN IN
NITROGEN BYPASS
Figure 19. Flow through heat exchangers (Air Products plant).
CRUDE NITROGEN
IN FROM COLUMN
OXYGEN IN
FROM LIQUID PUMP
2«
one of the innermost tubes; the air passes through the
inside of the larger tube. A great many very thin fins
emerge from the outside walls of the air lines. The
nitrogen passes around these 7 lines and absorbs from
the fins the heat which they in turn have absorbed
from the air. This type of exchanger is very simple
and efficient, having only 14 tubes. Because of their
efficiency only two such exchangers are needed.
26. FREEZE-UPS—A I R PRODUCTS
PLANT a. When the regular heat exchangers,
designated on the diagram as the “Air, O2, N2, heat
exchangers,” are operated in series with the freon and
dehydrating exchangers, there is little difficulty with
ice deposits. If the temperature falls below 0° C. in
the dehydrating heat exchanger, a freeze-up develops,
but the cold nitrogen which passes through this exchanger
is easily regulated by opening or closing the
nitrogen bypass, as shown in figure 19. Even if the
exchanger does freeze, the air can be bypassed to the
silica gel driers and operation continued as usual.
The nitrogen bypass should be opened at the same
time. After about an hour the exchanger will have
thawed and again be ready for operation.
h. After several weeks of continuous operation, it
is desirable to warm the entire plant to normal room
temperature. This allows any solid carbon dioxide
and ice in the system—always in very low quantities—
to thaw and be removed. This process is referred
to as defrosting. All that is involved is the
Figure 20. Freon compressor.
27
W
Figure 21. Freon condenser.
opening of all the drain valves on the panel and heat
exchangers and allowing air, under a pressure of
1,000 pounds per square inch, to pass through the
system. For quick defrosting the air is first sent to
the heaters in the silica gel drying system, where the
3-kilowatt heating elements heat it to a temperature
of not greater than 200° F. Instead of passing
through its own lines, the air is sent back through
the nitrogen lines for efficient removal of undesirable
substances.
27. FLOW OF FLUIDS—INDEPENDENT
PLANT The flow of gases through the exchangers
of the Independent plant can best be followed
by studying the schematic diagram shown in figure 22.
In these particular exchangers, the nitrogen flows inside
about 60 tubes, the air passing around them.
This can be seen clearly in the cross-sectional view
of the exchangers. The oxygen flows inside a group of
nine small tubes wrapped around the main shell of the
exchanger.
28
AIR OUT
__________________________ OXYGEN IN
NITROGEN IN , K
I "I r*| "I
R '-0-
C~ gO Or
RED^JA'NK B LU EMBANK
R —----- —t<4q [f» ®B
L-p , i- + \~^ ~ Lr L~i
(5v B ~ r r R ---- --- --------------------------------------- Q 0-CLOSED VALVE I ___ __________ QR Q* B T O-0PENVALVE
| | | R- RED
B - BLUE
Figure 22. Heat exchanger banks (Independent plant).
28. FREEZE- UPS—INDEPENDENT
PLANT a. One pressure gauge is placed in the
line before, and one after, the banks of heat exchangers.
During normal operation these gauges read
approximately the same pressure, the only difference
being caused by the friction of the air in going through
the exchangers. But when a freeze-up occurs, the air
cannot get through; consequently, the pressure gauge
placed after the exchanger shows much less pressure
than the one just before it. This is a sure indication
of congestion. The exchangers do not freeze up suddenly;
rather the tubes clog one by one. Experience
proves that when the pressure difference between the
inlet and outlet gauges is about 50 pounds, the
exchangers should be switched.
1». (1) Imagine that the red bank of exchangers
is beginning to freeze. This is indicated by the pressure
difference of a few pounds between the inlet and
outlet gauges. When the air cannot pass through the
red bank, preparations must be made to pass it through
the blue bank. The blue bank is now warm because
it has been standing idle for several days with no cold
gases passing through it. Before sending the warm
air into it, this bank should be cooled to prevent warm
air from passing into the very cold liquefier and rectifying
columns. If there is not such a preliminary
563566°— 44------ 5
cooling, much of the liquid air boils away. As the
pressure difference is noted, the nitrogen lines should
be switched so that the cold gas will go through the
blue (warm) bank, instead of the red one. The four
valves, located in a vertical row, and the two gate
valves, located at the lowest point on the side of the
column assembly box, are the nitrogen valves. Three
are painted red and three blue, corresponding to thenrespective
banks of exchangers. Open these blue
valves and close the red ones. By the time the pressure
difference is 50 pounds, the blue bank should be
cold enough to receive the air; therefore, the blue air
valve is opened and the red one closed. The air valves
are the two largest valves on the side of the box. The
two oxygen valves are switched last; with the exception
of the drain valves, just above which they are
located, they are the smallest of the valves.
(2) While one bank of exchangers is being used,
the other is being thawed out. Nitrogen is used for
this purpose. If the flow diagram of the exchangers is
carefully studied, it will be noted that the cold nitrogen
flows through the exchanger which is cooling, and
then, having picked up the heat of the air, instead of
being discharged into the atmosphere, goes through
the exchanger whose air line is clogged with ice and
melts this ice. The drain valves of the frozen ex-
29
changer should be open to allow the water to flow away
and free the air line. There are three red and three
blue drain valves for each bank. When all three valves
of any one bank are open and air comes out in force,
that particular bank is ready for use.
29. RECEIVER AND LIQUEFIER a.
The receiver and liquefier are found only in the Independent
plant. The Air Products plant does not have
a separate piece of equipment as the receiver. It incorporates
the principle in its heat exchangers, which
have seven large air tubes. Neither does the Air
Products plant have a separate liquefier, but instead
incorporates the principle in its boiling coil.
b. As the cold air leaves the exchangers of the Independent
plant, it goes into a small high-pressure
cylinder known as the receiver. The construction of
the receiver is much like that of the water trap previously
discussed. The cylinder is about the same size
and design as the water trap on the compressor. The
cold, high-pressure air enters at the top of the receiver
and leaves at the side. The temperature of the air
leaving the exchangers is about —80° C. Referring
to the discussion of carbon dioxide (see par. 6), it
will be remembered that this gas turns into dry ice at
about —56° C. at a pressure of 73 atmospheres (about
1,000 pounds per square inch). The pressure in the
exchangers is about 800 pounds per square inch
(about 55 atmospheres) at a temperature of —80° C.
From this it can be seen that the conditions in the
exchangers are just right for the carbon dioxide in
the air to change into dry ice. Probably this actually
occurs in the last exchanger of the bank. The dry
ice does not stick to the tubes of the exchangers as
readily as the frozen water, but is carried along with
the stream of air into the receiver. As the air comes
into the top of the receiver and takes a sudden turn
to the side and out, some of the solid carbon dioxide
drops down and can be blown out the drain line.
However, a large part of the carbon dioxide passes by
the receiver and over into the control valve. Nevertheless,
the receiver should be blown once or twice
during the day.
C. Perhaps a more useful purpose of the receiver
is its use as an air cushion. It tends to act as a surge
tank in smoothing out the flow of air. Since the air
is compressed by a compressor with pistons, pulsations
are inevitable. The receiver holds a small reservoir
of high-pressure air, and though it receives pulsations,
it delivers a fairly smooth stream of air to
the column and expansion engine. After the air leaves
the receiver it is split, about one-half going to the
expansion engine and the other half to the liquefier.
d. The liquefier is a piece of equipment which looks
very much like a heat exchanger; in fact, it is a heat
exchanger, but it operates at a much lower temperature
than the exchangers just discussed. The nitrogen
comes directly from the top of the column at a temperature
of about —196° C. and flows inside the tubes
of the liquefier countercurrent to the air, which is at
a temperature of about —80° C. The oxygen comes
from the side of the pot of the column at a temperature
of about —183° C., and flows in tubes wrapped
around the liquefier. The air is cooled down to approximately
—145° C. At this low temperature and
the high pressure of about 800 pounds it liquefies. At
atmospheric pressure, air liquefies at about —192° C.,
but in the liquefier the pressure is about 55 times
atmospheric pressure; hence the liquefying at the
higher temperature.
e. Having been liquefied, the air is ready to enter
the expansion valve and pass into the rectifying column
for the first step in the process of separating the
oxygen and nitrogen. If the liquid is drawn off
from the liquefier faster than it is made, as the liquid
level gets low, the solid particles of carbon dioxide
also will be drawn off and will pass over into the
expansion valve and block the air passage.
30
Section VI
Expansion Devices
30. PRINCIPLES OF THE EXPANSION
VALVE a. In nearly all oxygen plants
liquid air first is produced at some high pressure
ranging from 600 to 1,000 pounds per square inch.
The actual process of separating oxygen from nitrogen
takes place in the rectifying column, which generally
operates at the relatively low pressure of from 3 to 60
pounds per square inch. The pressure of liquid air
is reduced to a low column pressure for two reasons:
first, to allow the use of light mobile equipment;
second, to make possible a more efficient separation
of oxygen and nitrogen.
b. The expansion valve is so named because of the
action of the air in the valve. The air expands from
a pressure of from 600 to 1,000 pounds per square
inch to a pressure of from 3 to 60 pounds per square
inch. Many years ago it was observed that when
pressure on a gas suddenly was reduced, the gas was
cooled considerably. A simple experiment can be
performed to show this. Open the valve of a charged
oxygen cylinder and feel the gas coming from the
valve; notice that it is considerably cooler than the
cylinder. If the gas is allowed to escape with great
force, the temperature may drop so low that the water
in the air freezes on the valve. Thus, the air in passing
through the expansion valve is cooled from about
— 145° C. to about —175° C.
C. An important point is that if liquid air just at
its boiling point is expanded to a lower pressure, it is
converted in part to the gaseous state. This phenomenon
is known as “flashing off.” Unless the liquid first
is supercooled to a temperature below its temperature
of liquefaction, this “flashing” or vaporizing action
will occur. In the following discussion of rectification,
the undesirability of this action will become
apparent.
31. TYPES OF EXPANSION VALVES
a. Air Products valve The valve used by the
Air Products plant is a long, pointed needle valve.
The high-pressure liquid air expands against a pinpoint
valve stem. A desirable feature of the stem is
that if the valve is opened a half-turn of the stem,
the pressure does not surge through the valve, because
the stem and seat are designed so that the needle point
receives only gradually. Also, the stem is made with
27 threads per inch, which helps to make possible the
fine regulation necessary to take care of the expansion
from 800 to 3 pounds per square inch. Some air will
tend to leak by the valve stem and out to the handwheel.
To prevent this, the stem is packed with some
soft material, such as flax or waxed yarn. To prevent
loss of refrigeration along the valve stem a “thermal
break” is built into the stem. This break is simply
a solid disk of an insulating material, such as bakelite,
connected between two flanges. Also, a similar thermal
break is built into the main valve body for the
same purpose. The threads on the stem are located
beyond the two thermal breaks; therefore, they will
not bind, due to the freezing of atmospheric moisture.
Because of the thermal breaks and the location of the
threads, the latter can be lubricated with oil. An oil
cup is provided for this purpose. These features make
possible a fine-regulating, easy-turning valve. This
plant has only one expansion valve, located in the
liquid air line from the bottom to the top of the column.
With this design the air does not rush into the
column in a heavy blast, thus disturbing the rectification
process.
b. Independent valve The expansion
valve used in the Independent plant consists essentially
of a seat, stem, and handwheel. The stem is relatively
short, and has a flat tip. When operating this valve
the handwheel cannot be rotated more than a degree at
a time without causing a sudden pressure drop. This
valve is located near the top of the column; therefore,
should an operator attempt to open it more than just
a small amount, he would seriously disrupt the rectifying
process. No thermal break is provided on either
the valve stem or the valve body; therefore, the threads
on the stem will often bind as a result of the freezing
of atmospheric moisture. When the stem becomes
hard to turn, the operator usually is tempted to use
a pipe wrench to regulate the valve. The result is
often a broken stem or stripped threads. When the
threads freeze, heat should be applied by a welding
torch or blowtorch. The packing of the stem is similar
to that used in the Air Products plant.
31
32
HANDWHEEL
BAKELITE
THERMAL BREAK / n il CD PACKING NUT PACKING
U I L_ t r\ > |f— IR /X vZw zvl 1 \ / \ U l M s t . \ / - | \ | _________________________ \ ™
l b - pe r - s q in -
1L V7p|Sijilj
OIL SEA| _ ^ Lx^ ^ ^ ^ ^ ^ ™ = = = = = 2ZZZZZZZZZZZZZZZZZZ2=ZZZZ=Z=32ZZ=ZZZ==ZZZ2Z2=ZZ2Z=ZZaZZZZZZZZZZZZZZZ2ZZ2ZZ=Z^^ \ VALVE STEM
\ AIR OUTLET 3 LB. PER. SQ. IN.
EXPANSION VALVE
Figure 23. Expansion valve, cross-sectional view (Air Products plant).
Figure 24. Expansion valve assembly (Air Products plant).
33
VALVE SEAT
/ VALVE STEM PACKING
/ / PACKING NUT
HIGH \fyj» ,„. -----
lb per
SQ IN L0W PRESSURE AIR -------- •1 4 5 * C V A 5 LB PER SQ IN W
VHA / — 190° C W J ® GASE0US A'R H A N D W H E E L ^"
V ’ ▼ \ / LIQUID AIR X .
EXPANSION VALVE
Figure 25. Expansion valve, cross-sectional view (Independent plant).
34
32. EXPANSION ENGINE a. General
(I) The expansion engine is used only on
the Independent plant. This engine is probably the
most vital and sensitive piece of apparatus in the oxygen
plant. It is essentially a refrigerating machine.
It operates just like a steam engine on a locomotive,
except that compressed air replaces steam. The highpressure
air enters the expansion engine, pushes the
piston, becomes colder, and is exhausted.
(2) In moving the piston, the high-pressure air
does work. Since work done requires the expenditure
of energy, the air thus loses energy. Heat, measured
by temperature, is a form of energy present in air.
In doing work, in this case driving a piston, the air
gives up some of its heat. Therefore, the temperature
of the air decreases. In passing through the
expansion engine, the air goes from a pressure of about
55 atmospheres and —80° C. to a pressure af about
5 atmospheres and —175° C. Thus, the cooling effect
in the expansion engine is much greater than in the
expansion valve.
1». Operation (1) General The piston,
impelled by the high-pressure air, turns a crankshaft
which in turn rotates a flywheel. To prevent
the engine from operating at too great a speed, the flywheel
is connected by a belt to an electric generator.
When rotated, the armature of the generator produces
an electric current which passes through a resistance
box or heating coil. The more resistance put into
the circuit, the harder the expansion engine must work
to rotate the armature in the generator. This furnishes
an excellent way of controlling the work output
of the engine.
(2) Cooling process As the work output
of the engine increases, the cooling effect of the air also
increases. During the first cooling process the engine
is operated at full load so that the temperature of
the air is about —200° C. As this air is sent directly
to the liquefier and back to the exchangers, the incoming
air will be cooled faster. During normal operation,
the engine can be shut off for periods of 16 to 20
hours and operated only when more refrigeration is
necessary to build up a liquid level.
( 3 ) Piston action The expansion engine is
a single-stage, single-acting engine. In a single-stage
engine the air expands just once and then is exhausted.
In a double- or two-stage engine the air, after being
exhausted from one cylinder, goes into another cylinder,
where it drives a second piston and is exhausted.
In a single-acting engine the air comes in on only one
side of the piston, thus driving the piston in only one
direction. In a double-acting engine the air is introduced
into the top of the cylinder and drives the piston
down; when the piston reaches the bottom of its stroke,
another jet of air enters the bottom of the cylinder and
forces the piston upward. In the expansion engine,
the momentum of the flywheel drives the piston upward.
(4) Cups and packing' The piston does
not have piston rings as do the pistons of automobiles.
Instead, inserted around the piston are two leather or
fiber cups, called “crimps,” which act like piston rings
in an automobile to prevent the leaking of the highpressure
air. However, some air does leak by these
leather cups. If this air were allowed to escape, production
would decrease. Hence, the air after escaping
by the piston, enters a blow-by chamber, from which
it passes into the engine exhaust line to the liquefier.
To prevent air in the blow-by chamber from leaking
by the piston rod, the rod is packed with leather, which
remains partially flexible at low temperatures.
(a) Packing* leaks Packing leaks must be
corrected immediately. Otherwise, the low temperature
of the escaping air will condense and freeze the
atmospheric moisture outside the cylinder, thus forming
ice on the piston rod. The ice may tear the packing
so severely that the engine must be stopped and
new packing inserted. If tightening the packing nut
does not stop the leak, new packing must be used. In
replacing packing, it is important that the engine be
turned over to top dead center, that is, with the piston
as high as it will go. The old packing then is removed
and new packing inserted. Failure to have the piston
at top dead center results in ice forming on the portion
of the rod below the packing. When the engine again
is started, the packing will be torn by the ice. It is
not necessary to shut down the compressors when
changing packing, since replacement takes little time.
(I») Worn cups Since the piston is continually
moving, the piston cups will wear occasionally.
To change the cups the engine must be stopped and
the insulation removed, exposing the cylinder. The
four bolts holding the cylinder to the frame are removed
and the cylinder is lifted carefully, to protect
the gasket seat between the cylinder and the frame.
The cups can be removed by unscrewing the piston
sections, and new ones inserted in reverse manner.
(5) Valve assembly The valves of the engine
are similar to the intake and exhaust valves of
an ordinary automobile engine. Just below the valve
stem is a valve push rod. The push rod rests on a
cam which rotates with the crankshaft of the engine.
The cam is so placed that when the piston is at the
height of its stroke, the cam strikes the push rod
which forces up the intake valve and thus allows the
air to enter the engine. The exhaust valve operates
similarly. The length of time the valve is open is
regulated by the clearance or space between the valve
stem and the push rod: the greater the clearance, the
shorter time the valve will be open, and the less air
comes in or out.
(6) Valve clearance The valve clearance
can be adjusted. By removing the small %-inch plug
located alongside the engine, the ends of the stem and
rod are exposed. The engine flywheel is turned over
35
by hand until lhe valve to be adjusted is entirely
closed. A feeler gauge is inserted between the stem
and rod and the clearance measured. The push rod
should be adjusted to give a 0.037-inch clearance.
To make the adjustment, the crankcase cover is removed
and the nut locking the rod to the cam follower
loosened. The rod is turned into or out of the follower
to obtain the proper clearance.
( 7 ) Pusli-ro. The oxygen and nitrogen are separated in a
rectifying column about 7 or 8 feet high and 1 to iy2
feet in diameter. First, liquid air under high pressure
is reduced to the pressure in the column by means
of an expansion valve. If liquid air is to leave this
valve, it is necessary that the air be liquid before expansion,
for even though air cools readily in an expansion
valve, it is a thermodynamic impossibility for
gaseous air to liquefy upon expansion under the conditions
in the oxygen plants. In most plants liquid
air enters the upper or very top part of the column and
drops down onto bubble-cap trays. These are copper
plates equipped with small caps about the size of a
thimble. Their purpose is discussed in c below. The
liquid spills onto the first tray under the liquid inlet
to the column, and having filled it, spills over the side
and down to the next and so on until all trays are
filled. A receptacle called a pot, located at the very
bottom of the column, receives the liquid which spills
from the last tray. In this pot is the boiling coil; its
temperature is regulated between the boiling points of
oxygen and nitrogen. (Nitrogen boils at —196° C.
and oxygen at —183° C., at atmospheric pressure.)
Nitrogen liquefies less easily than oxygen; hence it
tends to boil away first. However, the molecular attraction
between these two gases is so great that nitrogen
will not boil away without taking some oxygen
along. The gaseous mixture, rich in nitrogen, leaves
the boiling coil and rises through the column by passing
through the small bubble caps.
C. Bubble caps are devices for bringing the liquid
and vapor in the column into close contact for efficient
scrubbing action. Their construction is illustrated in
figure 29. A cap is essentially two caps, one over
the other, as shown. A tray may contain as many
as 75 or 100 of these caps. The vapor comes up from
the tray below into the caps, passes through the series
of small holes in the top of the center cap, and then
passes through, striking the baffle cap, after which it
is forced downward and made to bubble through the
liquid on the tray. The liquid tends to exchange its
nitrogen for the oxygen in the gaseous mixture. A
detailed knowledge of the thermodynamics of this
process is not necessary to an understanding of the
function of the caps. All that is necessary is to understand
that the liquid gives up some of its nitrogen as
gas and, in turn, captures some of the oxygen which
enters the cap in the gaseous state. Consequently, as
it spills from tray to tray on down the column, the
liquid becomes richer and richer in oxygen.
34. SINGLE RECTIFICATION—AIR
PRODUCTS PLANT a. In the Air Products
plant single rectification is used. The air under a
pressure of approximately 1,000 pounds per square
inch leaves the last heat exchanger and enters a coil
in the pot of the column. This coil serves a double
purpose: it liquefies the air and creates a boiling
action in the pot. As was pointed out in paragraph
33, the pot contains a liquid mixture of oxygen and
nitrogen. Since the pressure in the column is only
3 pounds per square inch, the temperature in the pot
is about —183° C., the temperature of pure oxygen.
The pressure inside the coil is approximately 1,000
pounds per square inch; therefore, only a temperature
of —145° C. is required to convert this highpressure
gas into a liquid. In liquefying in the coil,
the air gives up some heat to the liquid in the pot,
thus creating the boiling action. The high-pressure
liquid leaves the pot and enters the high-pressure expansion
valve, which is located on the line from the
pot to the receiver of the nitrogen sidearm column.
The sidearm column makes it possible to produce nitrogen
99.99 percent pure. Essentially, it is a section of
copper pipe about 4 feet long, packed with small pieces
of ceramic material and equipped at the lower end with
a receiver and at the upper end with an outer jacket.
40
WASHED VAPOR TO NEXT TRAY .
^C. i ; LIQUID - J ~
VAPOR FROM TRAY BELOW
Figure 29. Flow of liquid and vapor through bubble cap.
I>. In the high-pressure expansion valve, liquid air
is expanded from a pressure of about 1,000 pounds
per square inch to the sidearm pressure of about 25
pounds per square inch. In expanding through the
valve the liquid air partially vaporizes, the gaseous
element rising up through the sidearm column, and
the liquid element dropping into the receiver and then
entering the low-pressure expansion valve where the
pressure drops to about 3 pounds per square inch.
From this valve the air passes through the oxygen
recondenser (to be discussed later) and enters the
outer jacket around the upper section of the sidearm.
It is important to emphasize that in expanding through
the low-pressure valve from a pressure of 25 pounds
per square inch to a pressure of 3 pounds per square
inch, the air is cooled several degrees; therefore, the
outer jacket around the upper section of the sidearm
must be colder than the gases in the sidearm itself.
Ihis fact is significant in the production of pure nitrogen.
The air which vaporized upon entering the receiver
of the sidearm column proceeds upward through
the ceramic material until it reaches the upper section
around the jacket containing liquid air. Since this
section is cooler than the rising air, the oxygen and
nitrogen start to liquefy and drop down through the
column. The ceramic packing brings this liquid mixture,
known as the reflux, into intimate contact with
the rising air. The result is that almost all of the
oxygen in the rising air is scrubbed out by the countercurrent
liquid, leaving almost pure nitrogen to pass
from the top of the column. A valve located on the
line from the top of the column determines the quantity
of the gas withdrawn. As the opening of the
valve is increased, more gas leaves the column and
the purity of the nitrogen accordingly decreases. With
this apparatus at least 100 cubic feet of nitrogen at
99.99 percent purity can be produced per hour. As
the desired purity of nitrogen is decreased, the pro-
41
LIQUID OVERFLOWS
/ TO TRAY BELOW \
/ SCRUBBED VAPORS \
/ ( RICH IN NITROGEN) \
' / +1 II II | ff ff tt f1 f \
; fl i t .1 i. i i
; /SSSSSS553 ES55J EJX^z-- = --- = --r=g&5S3 fcssa ESSSSSSSa CSS3 LxssssssS; ;
\l I If II fl ft I ......... J II II II II I 11
7, ill ill Sjffl ill f jft iii ih ill \\
:QI u J.:—il:—I.:—Il I—j i.... ;------- --------- :i—t —:? M 1^:I
; 01 r o 1 ° r ° 1 ' ' O o 1 o o A
i fZl ro row Ji ------ ; —t n fttfl n I "J A ; , . The Air Products plant is powered by a Continental
six-cylinder, twin-ignition, gasoline engine.
This engine uses from 7 to 8 gallons of gasoline per
hour. An 85-gallon tank is located underneath the
trailer. On the main panel board is a gasoline gauge,
which should register “full” before the plant is started.
The engine in the Independent plant is an RXLD
Hercules six-cylinder engine. The skid-mounted plant
has a 75-gallon gasoline tank mounted near the skids,
whereas the trailer plant has two 55-gallon tanks located
near the front of the trailer. This plant uses
approximately 8 gallons of gasoline per hour. The
oil in both of these engines should be changed at
least every 200 hours, or every 100 hours if the oil
is available. When the temperature is over 40° F.,
SAE 50 oil should be used; at temperatures from 0° F.
to 40° F., SAE 30 oil should be used; and below 0° F.,
SAE 10 oil should be used. The crankcase of these
engines holds approximately 6 quarts of oil and may
use from 1 to 3 quarts a day. The dipper stick should
register “full” when the engine is started up, and
approximately “% full” when the engine is running.
The Hercules engine in the Independent plant uses a
cylinder-lubricating oil to help cool and lubricate the
cylinder valves, since this engine runs particularly hot.
The oil generally used is known as Marvel Mystery
Oil. The sight feed oiler will give the valves the desired
regulation of 8 to 12 drops per minute. The
clutches and the transmission of both engines must
be greased at least once a day.
C. All pumps on both plants, such as the engine
water pumps, the compressor water pump, and the
caustic pumps, must be greased regularly with ordinary
cup grease. Lubrication of the main line shaft
on the Independent plant must be checked at least once
a day. The batteries on both engines must be checked
frequently to make sure that the plates are covered
with the right amount of electrolyte and distilled
water.
<1. The lubrication of the Nordberg three-stage
compressor is described in paragraph 13. The Curtis
V-type air compressor, however, is slightly different.
Its crankcase holds 6 quarts of oil, which not only
lubricates the crankshaft but also the pistons. About
a quart of oil a day is used; therefore, the plant must
be checked constantly. Above 0° F. SAE 30 oil is
used; below 0° F., SAE 10. The oil in the crankcases
of both the Curtis and Nordberg compressors is
changed about every 500 hours. Also, the air filters
of all types of compressors should be cleaned once or
twice a month.
e. The liquid oxygen pump requires little maintenance.
The bearings on the electric motor should
be checked for lubrication. The oxygen compressor
on the Independent plant, however, requires considerable
checking and maintenance. It is lubricated
with a soap-water solution, as described in paragraph
37f. Only distilled water should be used in making
this solution, since foreign matter, which could enter
with ordinary water, may cause an explosion within
the oxygen compressor. A still is provided on the
gasoline engine to produce distilled water. Water is
permitted to flow in a thin stream from the water tank
to the heater on the engine manifold. Steam from
the heater enters a condenser mounted on the engine
radiator, where it is converted into water and collected
in a glass jug. The still will produce about 3 gallons
of water per hour. The soap-water solution should
be carefully mixed; about 1% ounces of a high-grade
liquid soap should be used with 2% gallons of water.
The only soap used for lubricating the oxygen compressor
should be that recommended by a compressor
manufacturer. Most common soaps are hazardous
when used as an oxygen compressor lubricant. A
measuring cup is provided with the necessary markings
to give the correct amount of liquid soap. If
59
only a 1-gallon container is available, fill this fivesixths
full and add )/> ounce of soap. The container
should be checked to make sure that it is clean and
free from oil or any combustible matter. A sight feed
lubricator is provided on the compressor, through
which 70 or 80 drops of solution per minute should
pass. In freezing weather the radiators on both engines
should contain an antifreeze solution of 50
percent Prestone and 50 percent water.
46. DRYING PROCESS a. General
After a plant has been standing idle for several days
it accumulates water from the air which passed through
it during the warming-up process. Small deposits of
condensed water vapor line the inside tubes of the heat
exchangers and the bubble cap trays in the column.
It is important that this water be removed before the
plant is cooled down prior to normal operation. If
the water is not removed, particles of ice form from
the condensed vapors. These particles clog the control
valves and may clog the air stream itself. The
method of removing this condensed water vapor is
described in c below.
I». Starting procedures Standard procedures
must be followed to get the compressor, pumps,
and heaters into operation.
( I ) After routine checks have been made, the engine
is started and then idled at 500 revolutions per
minute for about 5 minutes. The Continental engine
of the Air Products plant is directly connected to a
5-kilowatt electric generator which furnishes power
to the caustic pump motor, freon condenser fan motor,
silica gel heater, liquid oxygen pump motor, and the
lighting system.
(2) All of the drain valves at the bottom of the
main panel board, the condensate trap drain of the
No. 1 exchanger, and the three air compressor trap
drains should be open before the air compressor is
started.
(3) The valves on the regenerative air driers
must be adjusted so that the air will go through the dry
silica gel and the waste nitrogen through the wet
silica gel. After this setting has been made, the air
inlet to the drier is closed. Then the No. 1 exchanger
bypass valve is opened about one turn and the nitrogen
exhaust valve closed, so that during operation there
will be a 2-inch reading on the manometer located on
the right side of the driers.
(4) The high- and low-pressure expansion valves
and the pure nitrogen outlet valve are opened one turn.
(5) After the engine throttle valve is opened to
an engine speed of 750 revolutions per minute the air
compressor is engaged and the throttle opened to a
governor speed of 1,800 revolutions per minute. The
voltage is adjusted to 120 volts and the circuit breaker
closed. The caustic pump switch is closed and the air
drier timing switch set for the correct number of hours
of silica gel reactivation.
(6) The air inlet to the driers is opened gradually,
and the three compressor trap drains are closed.
C. Drying* After the plant is started all the
drain valves from the heat exchangers and column
are opened about a half turn, and the expansion valves
opened a full turn. This allows the air to pass freely
through all parts of the equipment. With the valves
open in this manner the head pressure will not develop,
but will remain between 100 to 200 pounds per square
inch. The air passes through the caustic scrubber, or
caustic cylinders, and through the silica gel cylinders
before entering the heat exchangers or column. This
is necessary so the air will not deposit additional carbon
dioxide or water in the plant; instead, the dry
air, as it sweeps through the equipment, picks up the
condensed water vapor. After a period of approximately
2 to 3 hours, the air is dry enough for coolingdown
operations. This method of drying out an
oxygen plant applies equally well to the Air Products
and the Independent plants. The only difference is
that more valves must be opened when drying the
Independent plant. If the head pressure drops too
low (about 50 pounds per square inch) enough drain
valves are closed off to bring the pressure up to 150
to 200 pounds per square inch. On the other hand,
if the pressure becomes too high, the same valves are
opened. It is undesirable to allow the head pressure
to build up above 300 pounds per square inch, since
high-pressure air will cool rapidly as it expands in
the low-pressure throttle valves. Instead of drying the
plant, this rapid cooling condenses the water vapor.
47. INITIAL COOLING PROCESS
AIR PRODUCTS PLANT a. All trap drain
valves, including the three compressor traps and the
two exchanger drains, are closed. If the plant is
being started after a temporary shut-down, the drying
process as discussed in paragraph 46 is omitted and
the air inlet valve to the drier closed. Immediately
after all the drain valves have been closed, the inlet
valve is opened gradually. A sudden release of pressure
through this valve would send silica gel into
the exchangers.
I>. The low-pressure expansion valve is opened
about five turns, the pure nitrogen valve closed, and
the high-pressure expansion valve closed until the head
pressure is maintained at 3,000 pounds per square
inch. When the nitrogen column pressure reaches 60
pounds per square inch, the pure nitrogen bypass
valve is partially opened. It is closed again as soon
as the pressure decreases below 60 pounds per square
inch.
C. The freon king valve on the lower right-hand
side of the panel board is opened, the condenser
started, and the clutch of the compressor immediately
engaged.
<1. After about 3% hours from the time the cooling
process was started, 6 inches of oxygen at a purity of
«O
99.5 percent will have been deposited in the pot. This
oxygen is ready to be pumped; but, before pumping,
it is desirable to reduce the head pressure to approximately
1,000 pounds per square inch, a pressure permitting
continued operation at high purity.
e. Full resistance on the slide wire rheostat of the
oxygen pump motor should be put in the circuit, and
the pump started by closing the push-button switch.
The pump will start slowly at first, but can be speeded
up by adjusting the rheostat to reduce the resistance.
The speed of the pump is governed by the rise or fall
of the liquid level in the pot. The desirable stroke
of the plunger is 1%6 inches. This can be varied by
loosening the nut which fastens the cross head to the
slotted fitting on the cam of the motor and then sliding
the cross head one way or the other.
f. For pure nitrogen production the nitrogen column
pressure is increased to about 25 pounds per
square inch by partially closing the low-pressure expansion
valve. The pure nitrogen valve to the storage
bag is then opened until a reading of 6 inches appears
on the pure nitrogen flow meter. After the storage
bag is partially or entirely full, the nitrogen compressor
may be started and the gas compressed into
the cylinders.
£• The charging rack will hold four oxygen and
two nitrogen cylinders, but only half of these are filled
at a time. Within an hour three cylinders of oxygen
and one of nitrogen can be filled to 2,200 pounds per
square inch. Once the plant is stabilized to the correct
pressures and pump speed, no additional adjustment
should be required for several days of continuous
operation. It is important to emphasize that this
particular plant is designed to produce both oxygen
and nitrogen simultaneously at a purity of not less
than 99.5 percent.
48. INITIAL COOLING PROCESSINDEPENDENT
PLANT a. As soon as
the plant is dry, all the drain valves on the side of the
column-assembly box are closed. Either the red or
the blue bank of heat exchangers may be used, since
both are warm and dry. Assume that the red bank
of heat exchangers is to be used. All that is necessary
is to close all the blue valves and to open all the
oxygen valves and two high-pressure air valves. Three
nitrogen valves, one oxygen valve, and one highpressure
air valve are painted blue and the other valves
red, each color indicating a separate set of heat exchangers.
The next step is to close the drain valves to
the pot and to the receiver; these valves are located
on the bottom of the main panel board. Then close
the expansion valve and observe the gauge pressure
rise. The pressure will rise quickly, but should not
exceed 900 pounds per square inch. To keep the
pressure below 900 pounds per square inch, the expansion
valve is opened. This adjustment of the expansion
valve should be slight, as it takes a minute or two
before any noticeable change in the head pressure is
indicated on the gauge. When the head pressure rises
to about 500 pounds per square inch, open the expansion
engine inlet throttle valve about a quarter turn.
At the same time, turn the rheostat knob on the center
of the dynamometer control board counterclockwise
as far as it will go, then move the slide-bar rheostat
to the right about two-thirds of its travel.
1*. Since the expansion engine is single-acting, it
may not start immediately; therefore, it may be necessary
to turn over the flywheel by hand. Then immediately
open the exhaust valve, which is directly
below the throttle valve to the expansion engine, and
observe the engine speed registered on the tachometer.
It should not exceed 240 revolutions per minute. The
speed is regulated by the throttle air valve to the
engine. After a steady engine speed is obtained, the
head pressure will drop considerably and the correct
adjustment on the expansion valve is made to return
the head pressure to 850 or 900 pounds per square
inch. At the same time observe the column-gauge
pressure. If it is above 10 pounds per square inch,
it indicates that the nitrogen exhaust valve to the
atmosphere was not opened all the way, and should
be opened. With the valves set in this manner, the
exhaust from the expansion engine goes directly back
through the liquefier and travels countercurrent to the
air entering the system. As the temperature drops in
the expansion engine it is recorded by the pyrometer
on the front of the panel board. The output of the
generator is rated as 24 amperes and 125 volts. It is
desirable that the resistance load on the expansion
engine be so adjusted that this rating is not exceeded,
although a 10-percent overload for a period of a few
hours is not harmful. Whether the overload is harmful
may be determined by feeling the temperature of
the generator shell; if it does not burn the hand,
though the gauges show an overload, it will not harm
the engine. If the generator is so hot that it burns
the hand, the resistance must be lowered, or the
generator soon will burn out.
C. With the valves set to maintain the head pressure
between 850 and 900 pounds per square inch and
the speed of the engine maintained for 4 hours, there
is a rise on the liquid level gauge, or manometer, indicating
that liquid has begun to collect in the pot.
After a level of about 4 or 5 inches of liquid appears
in the pot, head pressure drops. As soon as the liquid
covers the boiling coil in the pot, more of the incoming
air is liquefied and the expansion valve must be
readjusted to maintain a head pressure of from 850
to 900 pounds per square inch. After making this
adjustment the rate of rise of liquid in the pot will
appear to stop, and a noticeable rise in column pressure
will be shown on the gauge. Then it is necessary
to slow the engine speed to between 150 and 160
revolutions per minute. This should be done slowly
in order to change the column pressure gradually. By
61
closing the throttle valve to the expansion engine a
little at a time, over a period of about ten minutes,
there should be no effect on the liquid on the trays.
Soon after this change of engine speed has been made
the liquid level in the pot will start to rise slowly.
After 1 to 2 hours there should be a liquid level of 14
inches in the pot. When this occurs the pure oxygen
outlet valve should be opened to three-fourths of a
turn, and the oxygen outlet valve to the atmosphere
opened wide. The oxygen outlet valve to the nurse
bag should be closed tightly. Now it is necessary to
start taking a series of purity tests. The purity percentage
will rise and, as soon as it reaches 99.5 percent,
the oxygen outlet valve to the atmosphere is closed
and the inlet valve to the nurse bag opened. After
these valves have been changed, the liquid level in the
pot will continue gradually to rise above the 14-inch
level. This indicates more oxygen can be taken out
of the pot. This is done by opening the pure oxygen
outlet valve a little at a time until the level in the pot
appears to stay the same. After this phase of operation
has been reached the plant will produce from
500 to 600 cubic feet per hour. This production can
be increased by slowly closing the throttle valve to
the expansion engine until it has stopped. At this
point all the air from the air compressors is liquefied
and should produce from 100 to 150 cubic feet per
hour more pure oxygen. If the operator holds the
head pressure within the range of 850 to 900 pounds
per square inch, the plant will continue constant production
for approximately 18 to 20 hours, or until the
liquid level in the pot has dropped to about 9 inches.
Then it will be necessary to start the expansion engine
again, as pointed out in paragraph 35.
«2
Section XI
Oxygen Cylinders
49. NOMENCLATURE AND DESIGNATION
a. There are many types of cylinders which
handle gases or liquids under high pressure. It is
important that an operator of an oxygen plant be able
to recognize not only ozygen cylinders but also
cylinders containing combustible gases. Oxygen by
itself will neither burn nor explode, but when under
high pressure in the presence of a combustible substance,
such as hydrogen, acetylene, or propane, it will
explode violently. A cylinder which has previously
contained an unknown gas should never be put on
an oxygen manifold, regardless of the emergency. A
seemingly empty hydrogen cylinder, for instance, if
put on the charging manifold and filled with oxygen,
would explode with enough violence to destroy the
equipment and personnel in the near vicinity of the
plant.
b. The oxygen cylinders used by the U. S. Government
are clearly marked, but occasions will arise when
operators will be forced to use foreign cylinders.
Therefore, foreign cylinder markings are discussed in
this section. All United States Army oxygen cylinders
are built to rigid Interstate Commerce Commission
specifications. On the neck of the cylinder is stamped
the allowable filling pressure (2,015 pounds per square
inch). In addition to these standard cylinders, there
are many smaller, and some larger, cylinders used by
the Army Air Forces and the Medical Corps. An example
of the stamp marks found on standard oxygen
cylinders is: “ICC-3A2015.” This indicates the specifications
to which the cylinder was built, and that
2,015 pounds per square inch is the allowable pressure.
At the present time the cylinders marked for
2,015 pounds are filled to 2,200 pounds per square
inch because of the critical shortage of cylinders.
There are two other numbers stamped on the cylinders:
below the specification number usually is
stamped the serial number of the cylinder; also on
the cylinder will be a number which may look like
“4-40,” which means that the cylinder was last tested
in April 1940. According to Interstate Commerce
Commission requirements, a cylinder must be tested
once every 5 years to five-thirds its working pressure.
In other words, a cylinder stamped for a pressure of
2,015 pounds per square inch is tested hydrostatically
to 3,360 pounds per square inch.
C. Most oxygen cylinders have the word “oxygen”
painted on them, and on many Government cylinders
the word “oxygen” is stamped on the brass cylinder
valves. Oxygen valves have a right-hand external
thread, usually of 0.903 inches outside diameter, 14
threads per inch. These can be distinguished easily
from a nitrogen valve by the left-hand thread on
the latter.
50. TESTING AND HANDLING a. The
first thing that should be done when an oxygen cylinder
arrives is to check the valve. First, look carefully
for signs of oil on or near the valve. When oil is
noticed on the cylinder valve, the valve must be taken
apart to determine whether oil has entered, in which
case it may be necessary to wash the entire cylinder
and replace the valve. When a cylinder is received
which contains signs of oil, the unit commander must
be notified immediately. Also, if the contents of a
cylinder are doubtful, the cylinder should be set aside,
marked, and referred to the commanding officer.
Carefully examine each cylinder as it arrives and look
for external damage such as deep scratches or bullet
marks.
b. The hammer test gives a rough estimate of the
strength of the cylinder. Strike the cylinder at its
midpoint with a hammer and listen carefully to the
sound. If the cylinder sounds “dead,” it should be
examined to see if water or other foreign material is
inside; if not, the cylinder should be scrapped. Another
method of checking the cylinder is to examine
the gas which comes from the cylinder upon opening
the valve. If the gas has an unrecognizable, foreign
odor, it should be set aside for action by the unit
commander. In case of doubt, the gas may be tested
by the purity-test apparatus. It is important that the
condition of all doubtful cylinders be carefully
recorded and marked so that they will present no
hazard to operating personnel. This action always
should be reported to the unit commander.
63
51. RECOGNITION OF FOREIGN CYLINDERS
a. At present, information is available
only on the German and Italian cylinders. The markings
on these cylinders differ radically from those on
American cylinders. Since the oxygen plant operator
probably will be required to operate foreign cylinders,
he must know them well. It must be stressed that
ignorance in recognizing foreign cylinders may be the
cause of violent explosions resulting in high casualties
and the loss of vital equipment.
!». The Germans imprint the name of the gas into
the metal of the cylinder, since they realize the great
danger in handling by inexperienced or careless operators.
In addition, a color code also is used. (See
table III for information on the types of German
cylinders.)
Table III. German cylinders
Color of cylinder German name English name
Red _ _ Wasserstoff Hydrogen.
Oxygen.
Nitrogen.
Acetylene.
Propane.
Compressed air.
Carbon dioxide.
Sulfur dioxide.
Methyl chloride.
Blue _ __ _ Sauerstoff
Green _ _ _ Stickstoff
Yellow___________
Grey with red
bands.
(Unknown)_______
(Unknown)_______
(Unknown)_______
(Unknown)_______
Azetylen (Acetylen).
Propane__________
Pressluff__________
Kohlen Satire_____
(Kohlen dioxid.)
Schwefel dioxid
(Stamped S02.)
Chlormethyl______
C. The Italians use a colored band on their cylinders.
Although the cylinder usually is not stamped,
the Italian name of the gas is given. (See table IV
for Italian markings.)
Table IV. Italian cylinders
Color of band Italian name English name
White_________ Ossigeno _.__________ Oxygen.
Blue__________ Aria compressa_____ Compressed air.
Yellow________ Anidride carbonica__
(Anidr carbon)
(Acido carbonico)
Carbon dioxide.
Orange________ Acetilene______ Red___________ Acetylene. Idrogeno____________ Hydrogen.
Green_________ Azoto_____ Nitrogen.
Black_________ Cloro_________ Chlorine.
Grey__________ Ammoniaca_________ Ammonia.
<1. The plant operator should devise some method
of learning the foreign names of these gases. Fortunately,
in most cases the foreign name looks very
much like the English name. When literally translated
Wasserstoff,” the German name for hydrogen,
means “water stuff.” “Stickstoff,” the German name
for nitrogen, means “choking stuff,” which is appropriate
since it cannot be breathed and will not support
combustion. “Sauerstoff,” the German name for
oxygen, means “sour stuff.” The word “oxygen”
comes from the Greek word meaning “acid former,”
and acids generally are recognized by their sour
taste.
64
ind ex
Paragraph Page
Accessories.______________________________ 39-44 56
Air:
Components__________________________ 1-10 1
Liquefaction_______________ 11-12 7
Purification___________________________ 18-22 14
Air compressor____________________________ 13 8
Air products plant:
Flow of fluids_________________________ 25 26
Freeze-ups_________________ 26 27
Initial cooling process_________________ 47 60
Single rectification_________________________34 40
*
Carbon dioxide____________________________ 6 3
Caustic scrubbing towers_________________ 19 14
Checking equipment.______________________ 45 59
Chemicals:
Formulas_____________________________ 9 5
Symbols___ :_________________________ 9 5
Components of air________________________ 1-10 1
Compression_______________________ 13-17,36-38 8,49
Cooling process, initial____________________ 47, 48 60
Cylinders, oxygen__________________________ 49-51 63
Definition:
Nitrogen_____________________________ 5 3
Oxygen________________________ 3 2
Dehydrating heat exchanger_______________ 22 23
Designation, oxygen cylinders_____________ 49 63
Driers, regenerative_______________________ 22 23
Drying process____________________________ 46 60
Engine, expansion_________________________ 32 35
Evaporative condenser____________________ 15 11
Expansion devices________________________ 30-32 31
Flash point of oil___________________ .______ 16 13
Flow of fluids:
Air products plant____________ ___________ 25 26
Independent plant____________________ 27 28
Foreign cylinders__________________________ 51 64
Formulas, chemicals_________________________ 9 5
Freeze-ups:
Air products plant____________________ 26 27
Independent plant____ _______________ 28 29
Freon precooler___________________________ 24 24
Gaseous compression______________________ 37 49
Gaseous nitrogen compression_____________ 38 50
Gases, inert_______________________________ 8 5
Gauge:
Liquid level__________________________ 40 56
Pressure______________________________ 43 57
Handling, oxygen cylinders_______________ 50 63
Heat exchangers_______________________ 22, 23-29 23
Paragraph Page
Heating coil______________________________ 41 56
High pressure removal:
Carbon dioxide_______________________ 20 15
Oil___________________________________ 20 15
Water__________________________ 20 15
Independent plant:
Flow of fluids_________________________ 27 28
Freeze-ups_______________ 28 29
Initial cooling process___________ 48 61
Rectification__ ___________ 35 42
Inert gases___________________ 8 5
Liquefaction of air_______________________ 11-12 7
Liquefier______________ 29 30
Liquid level gauge_________________________ 40 56
Liquid pump system______________________ 36 49
Nitrogen:
Compression__ ___________ 36-38 49
Definition__________________________ . _ 5 3
Nomenclature, oxygen cylinders___________ 49 63
Oxygen:
Compression__________________________ 36-38 49
Cylinders____________________________ 49-51 63
Definition________________ ____ L______ 3 2
Production____________________ 12 7
Pressure____________ ____ .________________ 11 7
Pressure gauge____________________________ 43 57
Precooler, freon___________________________ 24 24
Purification of air_________________________ 18-22 14
Purity testing apparatus__________________ 44 57
Pyrometer________________________________ 42 56
Radiator, compressor______________________ 14 11
Receiver_____________________________ 29 30
Recognition of foreign cylinders________ ,__ 51 64
Rectification_______________________ 33-55 40
Scales, temperature________________________ 4 2
Setting-up and starting procedures______ 45-48 61
Symbols, chemicals________________________ 9 5
Tachometer_______________________________ 39 56
Temperature:
Critical___________________ 11 7
Scales_______ ______________________ 4 2
Testing:
Apparatus_____________________ 44 57
Oxygen cylinder_____ ________________ 50 63
Valve, expansion..________________________ 30 31
Water __________ 7 5
Water traps_______________________________ 17 13
o
65

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U. S. GOVERNMENT PRINTING OFFICE : 1944 O - 563566

2955-1-I6| I | Soop Woter Lubricator 12955-1-34 I Snop Lever Sight Drip Valve Lunk 1/8" 343___________________
2955-1-15 I Pure Oxygen Outlet Valve 962 M R.orequol_______________________ 2955-1-33 I No 1 Expansion Valve IIS-46 Independent Engineering Co ea°g| Comm
2955-1-14 “ 1/4" Outlet Volve 222 X Crane or equal Comm. 2955-1'31 I 3/4"Pure Oxygen Outlet Control Volve-14-1/2P Crone or equal Comm
2955-~3 ~Purity Test Valves H8-162 Independent Engmeermg Ca Comm 2955'1-29 I l-l/2'Outlet Throttle Volve 20 Line MO. Nelson OB or equal________ Comm _
z' -------------------------------------- ------------------------------------------------------------- 2955-1 -1 2 5 Water Separator 2955 I 28 I Inlet Throttle Volve-118-284 Independent Engineering Ca equal Comm
/s' 2955 -1 -11 i 1/4" Blow Down Valve - 222 X Crone or equal Comm. 2955'1-27 6 1-1/2" Nitrogen Switch 20 Line N.O.Nelson O B. or equal__________ Comm
COOLING TOWER V \ 2955 -1 -10 "T" Thermocouples " 2955 -l~26 2 3/4" Oxygen Switch 25 Line N.O. Nelson O B or equal___________ Comm
/■'------- F"T ( NURSE BAG ) 7='~A\ 2955-1-9 ~i~ Liqu.d Level Gage -A 275 Meriam or equal ~ Comm. 2955-1'25 2 3/4" HP Air Switch 3640 X Crone or equal____________________ Comm.
f''——------- ------- - ----- ---------- \ \ 2955-1-8 4 Pressure Gage 12-137 Star or equal______________________ Comm 2955-1-24 I Tachometer 252 Weston Elec, or equal (0-400 R PM.)__________ Comm
|=7 | ) ‘ /) // 2955-1- 7 I 1/8" Drain Volve 12* Consolidated or equal________________ Comm 2955-1~23 I Flow Meter 22 P--------------------------------------------------------------------------Cornm..„
[=^|=-{ 1/ : // 2955-|-6 8 Prom Valves-118-172 Independent Eng.neering Co or equal Comm 2955-1-22 I Thawing Out Connection For Heat Interchanges I/81 Crane e&gl Com_m_
1 .jj Lt =i ) ________________________ // 2955'1-5 I Drain Valves-118-283 Independent Engineering Co or equal Comm 2955-1-21 I Drain Valve 1/4 -222 Crone or equal-------------------------------------------Cornm —
[ _____ (EXPANSION TANK // 2955-1-4 2~ l“ Drain Volve - 449-1/2 Crane or equal Comm. 2955-1-20 I 1/4" Gos Shut Off Volve 38* Consolidated or equal_____________ Comm_
//< 3/4" Drain Valve -3640X Crane or equal Comm 2955^19, _2_ Tachometer 252 Weston Elec or equal (0-1000 RPM}----------------- Comm_
) llg955;1-1*) /// 2955-1-2 "T 3/4" Dram Valve-449-1/2 Crane or equal________________ Comm 2955-1-18 _l_ 3/4" Water Inlet Valve Connection-449-1/2 Crone or equo.---------- Comm_
ft ,** [ ,-WATER LEVEL GAGE /// 2955-1-1 2 3/8" Drain Volve 232~H Crane or equal___________________ Comm 2955-1-17 2 3/4 Oxygen By Poss Volves 2^ Line NO Nelson OB eqw)------------------------
WATER RESERVOIR FILLER. ,(X [r=T=T=pZ| X //' NUMBER DESCR.PT.ON |mATER.Al | _____________________ DESCRIPTION_____________________ [MATERIAL
// HEAT INTERCHANGERS _____ COLUMN
-M-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------]|~ LIQUEFIER |]--------------------- 7 2955-l-8(0*-30»)
----------------------------------------------------------- ZT _______ ?| DRYING CYLINDERS .............. ..... ...... _ __________ ... ■ . f ^.6 LB_SAFETY VALVE
PUMPs W/ ♦ | /TO CHARGING I f, _ A i X. j I
lb /// 2955-1-4 .DRAIN I 2955-M5-*&/ MANIFOLD Z ~* \ W- - Z \ 2955-1-13 , 1
/// n i1 ,-U-) ii ii Mil rec ei ver ;MM --------------------I Ml iiT* w nr 0XY6EN ~ fl hl K l=n t—J t—J Ml $ f—J t— Hr loop LB. safety valve , a QS --------------- ll
GAS TANK 1 i | I (COMPRESSOR ------- , ------- -------- 1 1J D | ELj] T ,, - I . J--- Mfrl -------- --------- -x 4V E, 2955133
U—'J COMPRESSOR I ,------- h « "t -4- ----------------------A > i |M . J —I 1 I Qh2955-'-16 zM (0 hjiHlli " L MiRlil!! !d
2M5-.-2o “‘snsri.n^rra i ® ii ■■'it' ifli' h t wh-i ___ 1 ii । T- w  i| yJ ~I ||'ll irk \ h I (yipH
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PO’E,'U“T bn™™ 1 1 6^1 A ■” •”{■ 11 fl| |i MG/1 111 II — l < U Ss
1600R.P.M. L zr V x r l .) jo / io»-ioo*>a | | ‘|g (j±i!< J® HH J | -------------- vQ I I t»| If
GOVERNOR [ PUMP-4 | I U' & '?( ~ ' Bl 111 “ J, _ M ■ | II _____ . MV 5 |( |
................ 7 ,g--X- <1 29H-I-I2II [I V KI IrfuM ■ = ■ «8 Lrf------ ------------z\ z Wgw-I-,) J) I __ X*__ _ .. L7-=-' X “ [}, =‘ X■? ■tlit r753-^!M( z\\\\ ; a«ss-i->oJ'I IKI 1 | '
@ )T DRAIN - — I 2955-1-11_______ 111 >©=: “= “=« W ' ~ I CJ) 11 1 I ■ f tl
DRAINS 2955-1’7 i 2955-1-19 m L »__________ I-------------------------------J I____J [r____ b- - Fl -------- -------- & ) ‘ l( I ;_________2955-1-13j W*T
DRAIN PLUGS - ■ ■ --------- ------- 'J II II S ------- . 2955-1-26 !J I ------------------i *-------- । (!(
DRAIN PLUG < V...... " - 1(1 —- I----------------------- ---------------------------- K '2955-1-31 v*" 2955-1-13 |] ! ; _______-j ‘ili ’ ":
-jury50*1?; •> lT°aiiRl 955 *1 iB H FIELD gene rati ng PLANT IfMql
(1^4] S X 0XY6EN-NITR0GEN GAS pyro meter
\ b—d [111 IIL—--J KLr—-J V—J/ ® jd || /, MODEL 0,B
“®’*R compr es sors 955’"'2 । 29=5IZcom ppes so ^5''"2 £ ! L U FLOW DIAGRAM (SCHEMATIC)
2955-1-II 11 _____________________________ __________________ (H} I n____
------1 —I 1 INDEPENDENT ENGINEERING CO.
2955-1-3'
Figure 44. Flow diagram (Independent plant). u. s. gov er nme nt pr inting off ice ; 1944 0 - 563566




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