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          UNITED STATES FUEL ADMINISTRATION
                BUREAU OF CONSERVATION

              Engineering Bulletin No. 1

                  BOILER AND FURNACE
                       TESTING

                     Prepared by

                   Rufus T. Strohm
               Associate Editor, Power

         [Illustration: Maximum Production

                        Minimum Waste]

                     WASHINGTON
             GOVERNMENT PRINTING OFFICE
                        1918

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MAXIMUM PRODUCTION.

MINIMUM WASTE.


The United States Fuel Administration is making every effort,
through the producers and transportation lines, to obtain an
adequate supply of fuel for the industries of the country.

Twenty-five to fifty million tons of coal a year can be saved by
the improved operation of steam-power plants without changing their
present equipment and without abating their production the
slightest.

It is absolutely necessary that this saving be realized, if our
overburdened railroads are to be relieved and our industries kept
in full operation.

The extent to which it will be realized depends upon the
cooperation of the owners, engineers, and firemen of every power
plant of the country.

YOUR FIRING LINE IS AT THE FURNACE DOOR.

                                        DAVID MOFFAT MYERS,
     _Advisory Engineer to United States Fuel Administration_.

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BOILER AND FURNACE TESTING.

By RUFUS T. STROHM.


NECESSITY FOR TESTING BOILERS.

A boiler test is necessary in order to determine how well the
boiler is doing the work expected of it; that is to say, we must
find out whether we are wasting coal in making steam and how much
this waste may be. Such a test may be made to discover the
efficiency of the boiler, or the quantity of water it is
evaporating, or the cost of evaporating 1,000 pounds of water.

The United States Fuel Administration recommends that every boiler
plant have some means of daily checking the efficiency of the
boiler and furnace. The simplest and best way of finding out how
efficiently the boiler is working is to make an evaporation test,
as described in this bulletin. All the necessary records can be
made automatically with suitable instruments, although in many
small plants the coal must be weighed on ordinary scales. The
efficiency of the furnace can be found by making analyses of the
flue gases. (See Bulletin No. 2 of the United States Fuel
Administration.)

Too many engineers and firemen have the idea that they are not
fitted to make boiler tests. This is altogether wrong. Any man who
can weigh water and coal and read steam gages and thermometers is
able to do the work required in making a boiler test for
evaporation or efficiency. Such a test requires a knowledge of the
following:

  1. The total weight of coal used.

  2. [1]The total weight of water fed to and evaporated by the
  boiler.

  3. The average temperature of the feed water.

  4. The average steam pressure in the boiler.

If these four items are known, a series of simple calculations will
show how much water is being evaporated per pound of coal, and the
efficiency of the boiler and furnace.

To make a test, the following apparatus and instruments are
necessary:

  1. Scales to weigh the coal.

  2. Apparatus to weigh or measure the feed water.

  3. Thermometers to take feed-water temperature.

  4. Gages to indicate steam pressure.

A boiler test to be of value should extend over a period of at
least eight hours. The longer the test the more accurate the
results.

[Footnote 1: For the sake of simplicity, only the essential
elements of boiler and furnace testing are treated in this
bulletin. For rules covering the refinements for an exhaustive
test, the reader is referred to the boiler test code of the
American Society of Mechanical Engineers. Copies of this code can
be obtained from the secretary, 29 West Thirty-ninth Street, New
York City.]


WEIGHING THE COAL.

The weight of coal used during a test may easily be found by using
an ordinary wheelbarrow and a platform scales, arranged as in
figure 1. At each side of the scales build an incline with its top
level with the top of the platform, but take care not to have
either one touch the platform. Set the empty wheelbarrow on the
scales, run the movable weight or poise out until it exactly
balances the weight of the barrow and lock it in position with the
thumbscrew.

Next, put weights on the scale pan _A_ to correspond to a net
weight of 250 or 300 pounds of coal. Fill the barrow with coal, run
it on the scales, and add coal or take off coal until the scales
balance. This is easily done by having a small pile of coal _B_
beside the scales. If the weights on the scale pan represent, say,
300 pounds, the net weight of coal in the barrow is exactly 300
pounds. This coal is wheeled in front of the boiler and dumped on
the clean floor, and the barrow is returned for another load.

[Illustration: _Fig. 1._

1 _Set to balance tare of wheelbarrow_
2 _Add to balance net weight of coal_]

Each time the barrow of coal is weighed on the scales and taken to
the boiler being tested, a tally mark should be made on a board
nailed to the wall beside the scales. Each tally mark represents
300 pounds of coal, since the amount of coal in the barrow is
adjusted at each weighing, so that the scales just balance. At the
end of the test, therefore, the number of tally marks is multiplied
by 300, and the product is the weight of coal used, provided it has
all been fired; but if any coal remains in front of the boiler at
the close of the test, it must be gathered up and weighed, and its
weight must be subtracted from the total weight indicated by the
tally marks to get the number of pounds of coal actually fired. You
should, of course, start the test with no coal in front of the
boiler.

Care must be taken not to forget to make a tally mark each time a
barrow of coal is run off the scales. By setting the scales so as
to show any net weight, such as 250 or 300 pounds, and making each
barrow load exactly this weight, much time is saved, as it is
unnecessary to change any of the weights or the position of the
rider on the scale beam.

If the coal used in the test is to be analyzed, take a sample of
from 4 to 6 pounds from each barrow and throw it into a box near
the scales. Do this _before_ the coal is weighed. These small
amounts from the various barrow loads will then give a fair average
sample of the coal used during the test.

The condition of the furnace should be the same at the end of the
test period as at the start. Therefore, at the moment the test is
begun, observe the thickness of the fuel bed and the condition of
the fire. If the fire was cleaned, say, an hour before the test
began, see that it is cleaned an hour before the time when the test
is scheduled to end. If the coal was fired, say, eight minutes
before the test started, the last coal used during the test should
be fired eight minutes before the end of the test. The object of
these precautions is to insure the same conditions at start and
finish, as nearly as possible; otherwise, the coal weighed will not
be the same as the coal consumed.


MEASURING THE FEED WATER.

The quantity of water fed to the boiler during the test may be
found by metering or by weighing. A reliable water meter is
recommended for this work. There are a number of good makes, of
different types, such as:

  1. Venturi meter.

  2. Weir or V-notch meters.

  3. Diaphragm meters.

  4. Displacement meters.

  5. Water weighers.

The best form of meter to use in any particular case depends on the
local conditions in the plant; but _every plant should be provided
with a permanently installed meter of some type_. The displacement
form of meter should be used only with cold water, however.

If there is no meter or water weigher in the plant, the feed water
used during the test can be measured by the three-barrel
arrangement illustrated in figure 2.

Obtain three water-tight barrels, and set two of them close
together on a platform directly over the third, leaving about 12
inches above barrel 3 in which to fit the valves _V_ and the
nipples in the bottoms of barrels 1 and 2. Near the top of each of
the barrels 1 and 2 screw a 1-inch overflow pipe _O_.

Run a pipe _P_ from the city main or other source of supply above
barrels 1 and 2, and put a valve _A_ on the pipe leading to each
barrel. From barrel 3 run a suction pipe to the feed pump that is
to pump water to the boiler to be tested. It is best to have a
by-pass from the usual water supply direct to the feed pump, or to
another pump connected to the boiler, so that in case of any
trouble with the testing barrels, the regular operation of the
boiler may be resumed without shutting down.

The next step is to fill barrels 1 and 2 with water until they
overflow at _O_. This water should be of practically the same
average temperature as that which is to be used during the test.
Barrel 3 should be high enough above the feed pump so that the pump
will handle hot water. Put barrel 3 on a scales, before connecting
it to the feed pump, and weigh it. Then let the water from barrel 1
run into barrel 3, and weigh again. The second weight minus the
first weight is the net weight of water run in from barrel 1 and is
the weight of water contained in barrel 1 when filled to the
overflow. The weight of water in barrel 2 when it is filled to the
overflow can be found in like manner. Mark these weights down.

[Illustration: _Fig. 2._]

When the net weights are found and barrel 3 is removed from the
scales and connected to the feed pump, the apparatus is ready to
begin the test. Start with the level of the water about 1 foot
below the top of the barrel 3, and drive a nail into the barrel to
mark this level. When the test is finished, the level should be
brought to the same point, so that the water that has passed
through barrels 1 and 2 will accurately represent the weight of
water fed to the boiler during the test.

When the test is to begin, stop the feed pump and tie a string
around the gage glass on the boiler to mark the height of the water
level in the boiler. Then start the pump connected to barrel 3.
Fill barrels 1 and 2 up to the overflow before the test is started.
Then open the valve _V_ on barrel 1 and let the water run into
barrel 3 as fast as the feed pump draws water from barrel 3. When
barrel 1 is emptied close its valve _V_ and open its valve _A_ so
as to refill it.

While barrel 1 is filling empty barrel 2 into barrel 3 in the same
way, and continue to fill and empty barrels 1 and 2 alternately. In
this way barrel 3 will be kept supplied with water that has been
measured in barrels 1 and 2, the net weights of which were found
before the test began. Keep a separate tally of the number of times
each of the barrels 1 and 2 is emptied into barrel 3. At the end of
the test the number of tallies for each barrel multiplied by the
weight of the water that barrel will hold will be the weight of
water measured in that barrel. The sum of these weights for barrels
1 and 2 will be the weight of water used in the test.

With a three-barrel arrangement like this, water can be weighed
rapidly enough to supply 300 boiler horsepower.

Before starting a test make sure that there is no chance for water
to leak into or out of the boiler. See that the blow-off is tight,
that there is no drip from gage cocks, and that the feed-line
connections are tight, so that all the water fed to the boiler will
represent accurately the amount evaporated during the test.

If a meter is used instead of the three-barrel method, make
absolutely sure that the meter is correct, as the accuracy of the
test depends on the accuracy with which the water measurements are
made. _After a meter is installed, test it to see that it operates
correctly under the plant conditions._

The water level in the boiler should be the same at the end of the
test as at the beginning. As the time for stopping the test draws
near, therefore, try to bring the conditions the same as at the
start. Do not, however, run the feed pump rapidly in the last few
minutes for the test in order to obtain the same water level. If
there is a slight difference in level, calculate the weight of
water it represents and make the necessary correction to the total
weight of water fed.


TEMPERATURE OF FEED WATER.

Every plant should have a thermometer on the feed line, so as to
find the temperature of the feed water. Preferably, this
thermometer should be of the recording type. If such a form of
thermometer is used during the test, it is unnecessary to take the
feed temperature at stated intervals, as the record will show the
varying temperatures, and so the average feed temperature during
the test can easily be found.

If there is no thermometer in the feed line, take the feed-water
temperature by means of a thermometer hung in barrel 3 (figure 2)
by a hook over the edge of the barrel. Read this thermometer every
half hour during the test if the feed-water temperature is fairly
uniform; but if it varies considerably, read the thermometer every
15 minutes. The object is to obtain the average feed-water
temperature during the test period. Therefore, mark down the
temperatures as read at the stated intervals. At the close of the
test add the readings and divide their sum by the number of
readings and you will have the average temperature of the feed
water.


STEAM PRESSURE.

Every boiler is fitted with a steam gage by which the pressure is
indicated. It is important that the pressure gage be accurate. What
is wanted in a test is the average pressure of the steam in the
boiler, therefore, observe the pressure at regular intervals, just
as with the feed-water temperature, and mark down these gage
readings. The sum of the readings divided by the number of readings
taken will be the average steam pressure during the test.

A recording steam gage is best and makes its own readings.


WORKING UP THE TEST.

After the boiler test has been made, so as to find the weight of
coal burned, weight of feed water used, feed-water temperature and
steam pressure, the efficiency, the horsepower, and the economy
must be obtained by calculation from the test results. The process
of figuring the desired results from the test data is called
"working up the test."

To illustrate the method used in finding the efficiency, etc.,
suppose that the data obtained from the test are as follows:

  Length of test                                       hours      10
  Total weight of coal fired                          pounds   5,000
  Total weight of water evaporated                       do.  35,000
  Average temperature of feed water                       °F     180
  Average steam pressure, gage        pounds per square inch     100

The efficiency of any process is always a comparison, or ratio, of
the output to the input. In the case of a steam boiler the
efficiency is the percentage of the heat supplied in the coal that
is usefully employed in making steam. The output of the steam
boiler is the heat represented by the quantity of water evaporated
by a pound of coal, taking into account the feed temperature and
the steam pressure, and input is the amount of heat contained in a
pound of the coal used. The efficiency of the boiler is the output
divided by the input.

The heat contained in a pound of coal is called the "calorific
value" or "heating value" of the coal. It can be found by taking a
fair average sample of the coal used during the test, as explained
in connection with weighing the coal, and sending the sample to a
chemist, who will make a calorimeter test to determine its heating
value.

At the end of the test the sample fuel should be spread out on a
clean floor and all lumps broken up, so that no pieces are larger
than 2 inches maximum diameter. Then the gross sample should be
very thoroughly mixed by shoveling, after which it should be spread
out in the form of a square of uniform depth and quartered down
until a final average sample is obtained for shipment to a
competent chemist, experienced in fuel analysis. (See Bureau of
Mines Technical Paper No. 133.)

About 2 quarts of the chemist's sample should be put in air-tight
tins or jars for the determination of moisture; the balance of the
sample (the total weight of which should be from 10 to 50 pounds,
depending on the total weight of coal used in the test) may be
packed in a wooden box lined with paper to prevent splinters from
mingling with the sample. A duplicate coal sample should be kept at
the plant to be used in case of loss of the sample sent to the
chemist.

The Bureau of Mines has published a bulletin or pamphlet giving the
analyses and heating values of the various kinds and grades of coal
from all parts of the United States. (Bureau of Mines Bulletin No.
22.) This bulletin can be used to learn the approximate heating
value of the coal. Simply find out what district the coal used in
the test came from, and its grade, and then refer to the bulletin
to obtain the heating value of the coal. If a chemist can be
obtained to make a heat test, however, it is better to use the
heating value he determines.

Suppose that during the test the coal used was run-of-mine
bituminous having a heating value of 13,500 B. t. u. Every pound of
coal fired, then, carried into the furnace 13,500 heat units, and
this value therefore is the _input_ to be used in calculating the
boiler efficiency.

During the test 5,000 pounds of coal was fired and 35,000 pounds of
water was fed and evaporated. This means that 35,000 ÷ 5,000 = 7
pounds of water was evaporated per pound of coal burned. This is
the "actual evaporation," and the heat required to evaporate this 7
pounds of water is the output to be used in calculating the
efficiency.

Every fireman knows that it takes more coal, and therefore more
heat, to make steam with cold feed water than with hot feed water;
also, that it is somewhat easier to make steam at a low pressure
than at a high pressure. So it is plain that the heat required to
evaporate 7 pounds of water into steam depends on two things,
namely, (1) the temperature of the feed water and (2) the pressure
of the steam in the boiler. From the data of the test, both the
average feed-water temperature and the average steam pressure are
known, and so it is a simple matter to find out the amount of heat
needed to evaporate 7 pounds of water from the average temperature
to steam at the average pressure.

A pound of water at 212° F. must have 970.4 B. t. u. added to it to
become a pound of steam at 212° F., or zero gage pressure. This
value, 970.4 B. t. u., is called the latent heat of steam at
atmospheric pressure, or the heat "from and at 212° F." It is the
heat required to change a pound of water _from_ 212° F. to steam
_at_ 212° F., and is used by engineers as a standard by which to
compare the evaporation of different boilers.

In a boiler test the temperature of the feed water is usually
something less than 212° F., and the steam pressure is commonly
higher than zero, gage. In the test outlined previously, the
feed-water temperature was 180° F. and the pressure was 100 pounds
per square inch, gage. It must be clear, then, that the amount of
heat required to change a pound of water at 180° to steam at 100
pounds gage pressure is not the same as to make a pound of steam
from and at 212° F.

To make allowance for the differences in temperature and pressure,
the actual evaporation must be multiplied by a number called the
"factor of evaporation." The factor of evaporation has a certain
value corresponding to every feed-water temperature and boiler
pressure, and the values of this factor are given in the
accompanying table. Along the top of the table are given the gage
pressures of the steam. In the columns at the sides of the table
are given the feed-water temperatures. To find the factor of
evaporation for a given set of conditions, locate the gage pressure
at the top of the table and follow down that column to the
horizontal line on which the feed-water temperature is located. The
value in this column and on the horizontal line thus found is the
factor of evaporation required. If the feed water has a temperature
greater than 212° F., obtain the proper factor of evaporation from
the Marks and Davis steam tables.

Take the data of the test, for example. The average steam pressure
is 100 pounds, gage. The average feed-water temperature is 180° F.
So, in the table locate the column headed 100 and follow down this
column to the line having 180 at the ends, and the value where the
column and the line cross is 1.0727, which is the factor of
evaporation for a feed-water temperature of 180° F. and a steam
pressure of 100 pounds, gage.

This factor, 1.0727, indicates that to change a pound of water at
180° F. to steam at 100 pounds requires 1.0727 times as much heat
as to change a pound of water at 212° F. to steam at atmospheric
pressure. In other words, the heat used in producing an actual
evaporation of 7 pounds under the test conditions would have
evaporated 7 × 1.0727 = 7.5 pounds from and at 212° F. Hence, 7.5
pounds is called the "equivalent evaporation from and at 212° F."
per pound of coal used.

As already stated, it takes 970.4 B. t. u. to make a pound of steam
from and at 212° F. Then to make 7.5 pounds there would be required
7.5 × 970.4 = 7,278 B. t. u. This is the amount of heat required to
change 7.5 pounds of water at 212° F. to steam at zero gage
pressure, but it is also the heat required to change 7 pounds of
water at 180° F. to steam at 100 pounds gage pressure, because 7.5
pounds from and at 212° F. is equivalent to 7 pounds from 180° F.
to steam at 100 pounds. Therefore, the 7,278 B. t. u. is the amount
of heat usefully employed in making steam per pound of coal fired,
and so it is the _output_. Accordingly, the efficiency of the
boiler is--

                          Output    7,278
          ~ Efficiency =  ------ = ------ = 0.54, nearly.
                          Input    13,500

In other words, the efficiency of the boiler is 0.54, or 54 per
cent, which means that only a little more than half of the heat in
the coal is usefully employed in making steam.

The chart shown in figure 3 is given to save the work of figuring
the efficiency. If the equivalent evaporation per pound of coal is
calculated and the heating value of the coal is known, the boiler
efficiency may be found directly from the chart. At the left-hand
side locate the point corresponding to the equivalent evaporation
and at the bottom locate the point corresponding to the heating
value of the coal. Follow the horizontal and vertical lines from
these two points until they cross, and note the diagonal line that
is nearest to the crossing point. The figures marked on the
diagonal line indicate the boiler efficiency.

Take the case just worked out, for example. The equivalent
evaporation is 7.5 pounds and the heating value of the fuel is
13,500 B. t. u. At the left of the chart locate the point 7.5
midway between 7 and 8 and at the bottom locate the point 13,500
midway between 13,000 and 14,000. Then follow the horizontal and
vertical lines from these two points until they cross, as indicated
by the dotted lines. The crossing point lies on the diagonal
corresponding to 54, and so the efficiency is 54 per cent.


BOILER HORSEPOWER OR CAPACITY.

The capacity of a boiler is usually stated in boiler horsepower. A
boiler horsepower means the evaporation of 34.5 pounds of water per
hour from and at 212° F. Therefore, to find the boiler horsepower
developed during a test, calculate the evaporation from and at 212°
F. per hour and divide it by 34.5.

Take the test previously mentioned, for example. The evaporation
from and at 212° F. or the equivalent evaporation, was 7.5 pounds
of water per pound of coal. The weight of coal burned per hour was
5,000 ÷ 10 = 500 pounds. Then the equivalent evaporation was 7.5 ×
500 = 3,750 pounds per hour. According to the foregoing definition
of a boiler horsepower, then--

                                   3,750
               Boiler horsepower = ----- = 109.
                                    34.5


The "rated horsepower" of a boiler, or the "builders' rating," is
the number of square feet of heating surface in the boiler divided
by a number. In the case of stationary boilers this number is 10 or
12, but 10 is very commonly taken as the amount of heating surface
per horsepower. Assuming this value and assuming further that the
boiler tested had 1,500 square feet of heating surface, its rated
horsepower would be 1,500 ÷ 10 = 150 boiler horsepower.

It is often desirable to know what per cent of the rated capacity
is developed in a test. This is found by dividing the horsepower
developed during the test by the builders' rating. In the case of
the boiler tested, 109 horsepower was developed. The percentage of
rated capacity developed, therefore, was 109 ÷ 150 = 0.73, or 73
per cent.


HEATING SURFACE.

The heating surface of a boiler is the surface of metal exposed to
the fire or hot gases on one side and to water on the other side.
Thus, the internal surface of the tubes of a fire-tube boiler is
the heating surface of the tubes, but the outside surface of the
tubes of a water-tube boiler is the heating surface of those tubes.
In addition to the tubes, all other surfaces which have hot gases
on one side and water on the other must be taken into account. For
instance, in a fire-tube boiler from one-half to two-thirds of the
shell (depending on how the boiler is set) acts as heating surface.
In addition to this, the surface presented by both heads, below the
water level, has to be computed. The heating surface of each head
is equal to two-thirds its area minus the total area of the holes
cut away to receive the tubes.


COST OF EVAPORATION.

The cost of evaporation is usually stated as the cost of fuel
required to evaporate 1,000 pounds of water from and at 212° F. To
find it, multiply the price of coal per ton by 1,000 and divide the
result by the product of the equivalent evaporation per pound of
coal and the number of pounds in a ton.

Suppose that the cost of the coal used in the foregoing test was
$3.60 per ton of 2,000 pounds. The equivalent evaporation per pound
of coal was 7.5 pounds. Therefore the cost of evaporating 1,000
pounds of water from 180° F. to steam at 100-pound gage, is--

               $3.60 × 1,000
               ------------- = $0.24, or 24 cents.
                7.5  × 2,000


TABLE OF TEST RESULTS.

After the test has been made and properly worked up, as heretofore
described, collect all the results of the test on one sheet, so
that they can be kept in convenient form for reference and for
comparison with later tests. A brief form of arranging the results
is as follows:

  1. Date of test                                        May 20, 1918
  2. Duration of test                             hours            10
  3. Weight of coal used                         pounds         5,000
  4. Weight of water fed and evaporated             do.        35,000
  5. Average steam pressure, gauge                  do.           100
  6. Average feed-water temperature                 °F.           180
  7. Factor of evaporation                                     1.0727
  8. Equivalent evaporation from and at 212° F.  pounds        37,545

  EFFICIENCY.

  9. Efficiency of boiler and furnace           per cent           54

  CAPACITY.

  10. Boiler horsepower developed                                 109
  11. Builders' rated horsepower                                  150
  12. Percentage of rated horsepower developed  per cent           73

  ECONOMIC RESULTS.

  13. Actual evaporation per pound of coal        pounds            7
  14. Equivalent evaporation from and at 212° F.
      per pound of coal as fired,                 pounds          7.5
  15. Cost of coal per ton (2,000 pounds)                       $3.60
  16. Cost of coal to evaporate 1,000 pounds from and at
      212° F.                                                   $0.24


HOW TO USE THE TEST RESULTS.

The object of working up a test is to obtain a clear idea as to the
efficiency of operation of the boiler or its operating cost.
Consequently, after the calculations have been made, they should be
used as a basis for study with the idea of improving the boiler
performance.

Take the matter of boiler efficiency, for example, as found from
the test mentioned. Its value was 54 per cent. This is altogether
too low and indicates wasteful operation. The efficiency of a
hand-fired boiler ought not to be less than 65 per cent, and it can
be increased to 70 per cent by careful management under good
conditions.

The chart in figure 3 can be used to indicate the evaporation that
should be obtained in order to reach a desired efficiency. Suppose,
for example, that it is desired to know how much water per pound of
coal must be evaporated to produce a boiler efficiency of 65 per
cent with coal having a heating value of 13,500 B. t. u. per pound.

Locate 13,500 at the bottom of the chart, follow the vertical line
until it meets the diagonal marked 65 per cent, and then from this
point follow the horizontal line to the left-hand edge, where the
figure 9 is found. This means that the equivalent evaporation from
and by 212° F. per pound of coal must be 9 pounds of water. If the
steam pressure is 100 pounds gauge, and the feed-water temperature
is 180° F. the factor of evaporation is 1.0727, then the actual
evaporation must be 9 ÷ 1.0727 = 8.36 pounds per pound of coal. In
other words, to increase the efficiency from 54 per cent to 65 per
cent under the same conditions of pressure and feed-water
temperature, it would be necessary to increase the actual
evaporation from 7 pounds to 8.36 pounds. This would mean
practically 20 per cent more steam from the same weight of coal
used.

[Illustration: _Heating Value of Coal, in B. t. u. Per Pound_

FIG. 3.]

How to do this will require some study and experimenting on the
part of the fireman or engineer. The three most common reasons for
low-boiler efficiency are (1) excess air, (2) dirty heating
surfaces, and (3) loss of coal through the grates. _The first of
these items is the most important of the three._ In most cases the
greatest preventable waste of coal in a boiler plant is directly
due to excess air. Excess air simply means the amount of air which
gets into the furnace and boiler which is not needed for completing
the combustion of the coal. Very often twice as much air is
admitted to the boiler setting as is required. This extra or excess
air is heated and carries heat out through the chimney instead of
heating the water in the boiler to make steam. There are two ways
in which this excess air gets into the furnace and boiler setting.
First, by a combination of bad regulation of drafts and firing. The
chances are your uptake damper is too wide open. Try closing it a
little. Then, there may be holes in the fire. Keep these covered.
The second way excess air occurs is by leakage through the boiler
setting, through cracks in the brickwork, leaks around the frames
and edges of cleaning doors, and holes around the blow-off pipes.
There are also other places where such air can leak in.

Take a torch or candle and go over the entire surface of your
boiler setting--front, back, sides, and top. Where the flame of the
torch is drawn inward there is an air leak. Plaster up all air
leaks and repair the brickwork around door frames where necessary.
You should go over your boiler for air leaks once a month.

In regard to best methods of firing soft coal, see Technical Paper
No. 80 of the Bureau of Mines, which may be obtained from your
State Fuel Administrator.

Dirty heating surfaces cause low efficiency because they prevent
the heat in the hot gases from getting through into the water.
Therefore, keep the shell and tubes free of soot on one side and
scale on the other. Soot may be removed by the daily use of
blowers, scrapers, and cleaners. The problem of scale and pure feed
water is a big one and should be taken up with proper authorities
on the subject.

There are many things that may be done to increase the efficiency
of the boiler and to save coal. For convenience a number of these
points are grouped in the following list:

      WHAT TO DO.                      |    WHY.
                                       |
   1. Close up all leaks in the boiler | To prevent waste of heat due to
      setting.                         | excess air admitted.
                                       |
   2. Keep shell and tubes free from   | To allow the heat to pass easily
      soot and scale.                  | into the water.
                                       |
   3. Use grates suited to the fuel    | To prevent loss of unburnt coal
      to be burned.                    | through air spaces.
                                       |
   4. Fire often, and little at a      | To obtain uniform conditions and
      time.                            | better combustion.
                                       |
   5. Cover all thin spots and keep    | To prevent burning holes in bed
      fire bed level.                  | and admitting excess air.
                                       |
   6. Do not allow clinkers to form    | Because they reduce the effective
      on side or bridge walls.         | area of the grate.
                                       |
   7. Keep the ash pit free from ashes | To prevent warping and burning out
      and hot clinkers.                | of the grates.
                                       |
   8. Do not stir the fire except when | Because stirring causes clinker
      necessary.                       | and is likely to waste coal.
                                       |
   9. Use damper and not ash-pit doors | Because less excess air is
      to control draft.                | admitted by so doing.
                                       |
  10. See that steam pipes and valves  | Because steam leaks waste heat
      are tight.                       | and therefore coal.
                                       |
  11. Keep blow-off valves tight.      | Because leaks of hot water waste
                                       | coal.
                                       |
  12. Cover steam pipes and the tops   | To prevent radiation and loss of
      of boilers.                      | heat.

Make a boiler test under the conditions of operation as they now
exist in your plant. Then make all possible improvements as
suggested in this bulletin, make another test afterwards and note
the increase in the equivalent evaporation per pound of coal used.

Remember that the _firing line_ in the boiler room can be just as
patriotic and helpful as the _firing line_ at the front.


_Table of factors of evaporation._

 ============================================================================
     Feed    |        Steam pressure in pounds per square inch, gauge.
 temperature,|---------------------------------------------------------------
     °F.     |   30  |   50  |   70  |   80  |   90  |  100  |  110  |  120
 ------------+-------+-------+-------+-------+-------+-------+-------+-------
  32         | 1.2073| 1.2144| 1.2195| 1.2216| 1.2234| 1.2251| 1.2266| 1.2279
  35         | 1.2042| 1.2113| 1.2164| 1.2184| 1.2203| 1.2219| 1.2235| 1.2248
  38         | 1.2011| 1.2082| 1.2133| 1.2153| 1.2172| 1.2188| 1.2204| 1.2217
  41         | 1.1980| 1.2051| 1.2102| 1.2122| 1.2141| 1.2157| 1.2173| 1.2186
  44         | 1.1949| 1.2020| 1.2071| 1.2091| 1.2110| 1.2126| 1.2142| 1.2155
  47         | 1.1918| 1.1989| 1.2040| 1.2060| 1.2079| 1.2095| 1.2111| 1.2124
  50         | 1.1887| 1.1958| 1.2009| 1.2029| 1.2048| 1.2064| 1.2080| 1.2093
  53         | 1.1856| 1.1927| 1.1978| 1.1998| 1.2017| 1.2033| 1.2049| 1.2062
  56         | 1.1825| 1.1896| 1.1947| 1.1967| 1.1986| 1.2002| 1.2018| 1.2031
  59         | 1.1794| 1.1865| 1.1916| 1.1937| 1.1955| 1.1972| 1.1987| 1.2000
  62         | 1.1763| 1.1835| 1.1885| 1.1906| 1.1924| 1.1941| 1.1956| 1.1970
  65         | 1.1733| 1.1804| 1.1854| 1.1875| 1.1893| 1.1910| 1.1925| 1.1939
  68         | 1.1702| 1.1773| 1.1823| 1.1844| 1.1862| 1.1879| 1.1894| 1.1908
  71         | 1.1671| 1.1742| 1.1792| 1.1813| 1.1832| 1.1848| 1.1864| 1.1877
  74         | 1.1640| 1.1711| 1.1762| 1.1782| 1.1801| 1.1817| 1.1833| 1.1846
  77         | 1.1609| 1.1680| 1.1731| 1.1751| 1.1770| 1.1786| 1.1802| 1.1815
  80         | 1.1578| 1.1650| 1.1700| 1.1721| 1.1739| 1.1756| 1.1771| 1.1785
  83         | 1.1548| 1.1619| 1.1669| 1.1690| 1.1708| 1.1725| 1.1740| 1.1754
  86         | 1.1518| 1.1588| 1.1638| 1.1659| 1.1678| 1.1694| 1.1710| 1.1723
  89         | 1.1486| 1.1557| 1.1608| 1.1628| 1.1647| 1.1663| 1.1679| 1.1692
  92         | 1.1455| 1.1526| 1.1577| 1.1597| 1.1616| 1.1632| 1.1648| 1.1661
  95         | 1.1424| 1.1495| 1.1546| 1.1566| 1.1585| 1.1602| 1.1617| 1.1630
  98         | 1.1393| 1.1465| 1.1515| 1.1536| 1.1554| 1.1571| 1.1586| 1.1600
 101         | 1.1363| 1.1434| 1.1484| 1.1505| 1.1523| 1.1540| 1.1555| 1.1569
 104         | 1.1332| 1.1403| 1.1453| 1.1474| 1.1492| 1.1509| 1.1525| 1.1538
 107         | 1.1301| 1.1372| 1.1423| 1.1443| 1.1462| 1.1478| 1.1494| 1.1507
 110         | 1.1270| 1.1341| 1.1392| 1.1412| 1.1431| 1.1447| 1.1463| 1.1476
 113         | 1.1239| 1.1310| 1.1360| 1.1382| 1.1400| 1.1417| 1.1432| 1.1445
 116         | 1.1209| 1.1280| 1.1330| 1.1351| 1.1369| 1.1386| 1.1401| 1.1415
 119         | 1.1178| 1.1249| 1.1299| 1.1320| 1.1339| 1.1355| 1.1370| 1.1384
 122         | 1.1147| 1.1218| 1.1269| 1.1289| 1.1308| 1.1324| 1.1340| 1.1353
 125         | 1.1116| 1.1187| 1.1238| 1.1258| 1.1277| 1.1293| 1.1309| 1.1322
 128         | 1.1085| 1.1156| 1.1207| 1.1227| 1.1246| 1.1262| 1.1278| 1.1291
 131         | 1.1054| 1.1125| 1.1176| 1.1197| 1.1215| 1.1232| 1.1247| 1.1260
 134         | 1.1023| 1.1095| 1.1145| 1.1166| 1.1184| 1.1201| 1.1216| 1.1230
 137         | 1.0993| 1.1064| 1.1114| 1.1135| 1.1153| 1.1170| 1.1185| 1.1199
 140         | 1.0962| 1.1033| 1.1083| 1.1104| 1.1123| 1.1139| 1.1154| 1.1168
 143         | 1.0931| 1.1002| 1.1052| 1.1073| 1.1092| 1.1108| 1.1124| 1.1137
 146         | 1.0900| 1.0971| 1.1022| 1.1042| 1.1061| 1.1077| 1.1093| 1.1106
 149         | 1.0869| 1.0940| 1.0991| 1.1011| 1.1030| 1.1046| 1.1062| 1.1075
 152         | 1.0838| 1.0909| 1.0960| 1.0980| 1.0999| 1.1015| 1.1031| 1.1044
 155         | 1.0807| 1.0878| 1.0929| 1.0950| 1.0968| 1.0985| 1.1000| 1.1013
 158         | 1.0776| 1.0847| 1.0898| 1.0919| 1.0937| 1.0954| 1.0969| 1.0982
 161         | 1.0745| 1.0817| 1.0867| 1.0888| 1.0906| 1.0923| 1.0938| 1.0952
 164         | 1.0715| 1.0786| 1.0836| 1.0857| 1.0875| 1.0892| 1.0907| 1.0921
 167         | 1.0684| 1.0755| 1.0805| 1.0826| 1.0844| 1.0861| 1.0876| 1.0890
 170         | 1.0653| 1.0724| 1.0774| 1.0795| 1.0813| 1.0830| 1.0845| 1.0859
 172         | 1.0632| 1.0703| 1.0754| 1.0774| 1.0793| 1.0809| 1.0825| 1.0838
 174         | 1.0611| 1.0683| 1.0733| 1.0754| 1.0772| 1.0789| 1.0804| 1.0817
 176         | 1.0591| 1.0662| 1.0712| 1.0733| 1.0752| 1.0768| 1.0783| 1.0797
 178         | 1.0570| 1.0641| 1.0692| 1.0712| 1.0731| 1.0747| 1.0763| 1.0776
 180         | 1.0549| 1.0621| 1.0671| 1.0692| 1.0710| 1.0727| 1.0742| 1.0756
 182         | 1.0529| 1.0600| 1.0650| 1.0671| 1.0690| 1.0706| 1.0721| 1.0735
 184         | 1.0508| 1.0579| 1.0630| 1.0650| 1.0669| 1.0685| 1.0701| 1.0714
 186         | 1.0488| 1.0559| 1.0609| 1.0630| 1.0648| 1.0665| 1.0680| 1.0694
 188         | 1.0467| 1.0538| 1.0588| 1.0609| 1.0628| 1.0644| 1.0660| 1.0673
 190         | 1.0446| 1.0517| 1.0568| 1.0588| 1.0607| 1.0623| 1.0639| 1.0652
 192         | 1.0425| 1.0497| 1.0547| 1.0568| 1.0586| 1.0603| 1.0618| 1.0632
 194         | 1.0405| 1.0476| 1.0526| 1.0547| 1.0566| 1.0582| 1.0597| 1.0611
 196         | 1.0384| 1.0455| 1.0506| 1.0526| 1.0545| 1.0561| 1.0577| 1.0590
 198         | 1.0363| 1.0435| 1.0485| 1.0506| 1.0524| 1.0541| 1.0556| 1.0570
 200         | 1.0343| 1.0414| 1.0464| 1.0485| 1.0504| 1.0520| 1.0535| 1.0549
 202         | 1.0322| 1.0393| 1.0444| 1.0464| 1.0483| 1.0499| 1.0515| 1.0528
 204         | 1.0301| 1.0372| 1.0423| 1.0444| 1.0462| 1.0479| 1.0494| 1.0507
 206         | 1.0281| 1.0352| 1.0402| 1.0423| 1.0441| 1.0458| 1.0473| 1.0487
 208         | 1.0260| 1.0331| 1.0381| 1.0402| 1.0421| 1.0437| 1.0453| 1.0466
 210         | 1.0239| 1.0310| 1.0361| 1.0381| 1.0400| 1.0416| 1.0432| 1.0445
 212         | 1.0218| 1.0290| 1.0340| 1.0361| 1.0379| 1.0396| 1.0411| 1.0425
 ----------------------------------------------------------------------------


_Table of factors of evaporation_--Concluded.

 ============================================================================
     Feed    |        Steam pressure in pounds per square inch, gauge.
 temperature,|---------------------------------------------------------------
     °F.     |  130  |  140  |  150  |  160  |  170  |  180  |  190  |  200
 ------------+-------+-------+-------+-------+-------+-------+-------+-------
  32         | 1.2292| 1.2304| 1.2315| 1.2324| 1.2333| 1.2342| 1.2351| 1.2358
  35         | 1.2261| 1.2273| 1.2283| 1.2293| 1.2302| 1.2311| 1.2320| 1.2327
  38         | 1.2230| 1.2242| 1.2252| 1.2262| 1.2271| 1.2280| 1.2288| 1.2296
  41         | 1.2199| 1.2211| 1.2221| 1.2231| 1.2240| 1.2249| 1.2257| 1.2265
  44         | 1.2168| 1.2180| 1.2190| 1.2200| 1.2209| 1.2218| 1.2226| 1.2234
  47         | 1.2137| 1.2149| 1.2159| 1.2168| 1.2178| 1.2187| 1.2195| 1.2202
  50         | 1.2106| 1.2118| 1.2128| 1.2137| 1.2147| 1.2156| 1.2164| 1.2171
  53         | 1.2075| 1.2087| 1.2097| 1.2107| 1.2116| 1.2125| 1.2133| 1.2141
  56         | 1.2044| 1.2056| 1.2066| 1.2076| 1.2085| 1.2094| 1.2102| 1.2110
  59         | 1.2013| 1.2025| 1.2035| 1.2045| 1.2054| 1.2063| 1.2072| 1.2079
  62         | 1.1982| 1.1994| 1.2005| 1.2014| 1.2023| 1.2032| 1.2041| 1.2048
  65         | 1.1951| 1.1963| 1.1974| 1.1983| 1.1992| 1.2002| 1.2010| 1.2017
  68         | 1.1920| 1.1933| 1.1943| 1.1952| 1.1961| 1.1971| 1.1979| 1.1986
  71         | 1.1889| 1.1902| 1.1912| 1.1921| 1.1931| 1.1940| 1.1948| 1.1955
  74         | 1.1859| 1.1871| 1.1881| 1.1890| 1.1900| 1.1909| 1.1917| 1.1924
  77         | 1.1828| 1.1840| 1.1850| 1.1860| 1.1869| 1.1878| 1.1886| 1.1894
  80         | 1.1797| 1.1809| 1.1820| 1.1829| 1.1838| 1.1847| 1.1856| 1.1863
  83         | 1.1766| 1.1778| 1.1789| 1.1798| 1.1807| 1.1817| 1.1825| 1.1832
  86         | 1.1735| 1.1748| 1.1758| 1.1767| 1.1776| 1.1786| 1.1794| 1.1801
  89         | 1.1704| 1.1717| 1.1727| 1.1736| 1.1746| 1.1755| 1.1763| 1.1770
  92         | 1.1674| 1.1686| 1.1696| 1.1705| 1.1715| 1.1724| 1.1732| 1.1739
  95         | 1.1643| 1.1655| 1.1665| 1.1675| 1.1684| 1.1693| 1.1701| 1.1709
  98         | 1.1612| 1.1624| 1.1635| 1.1644| 1.1653| 1.1662| 1.1671| 1.1678
 101         | 1.1581| 1.1593| 1.1604| 1.1613| 1.1622| 1.1632| 1.1640| 1.1647
 104         | 1.1550| 1.1563| 1.1573| 1.1582| 1.1592| 1.1601| 1.1609| 1.1616
 107         | 1.1519| 1.1532| 1.1542| 1.1551| 1.1561| 1.1570| 1.1578| 1.1585
 110         | 1.1489| 1.1501| 1.1511| 1.1521| 1.1530| 1.1539| 1.1547| 1.1555
 113         | 1.1458| 1.1470| 1.1481| 1.1490| 1.1499| 1.1508| 1.1515| 1.1524
 116         | 1.1427| 1.1439| 1.1450| 1.1459| 1.1468| 1.1478| 1.1486| 1.1493
 119         | 1.1396| 1.1409| 1.1419| 1.1428| 1.1437| 1.1447| 1.1455| 1.1462
 122         | 1.1365| 1.1378| 1.1388| 1.1397| 1.1407| 1.1416| 1.1424| 1.1431
 125         | 1.1335| 1.1347| 1.1357| 1.1366| 1.1376| 1.1385| 1.1393| 1.1400
 128         | 1.1304| 1.1316| 1.1326| 1.1336| 1.1345| 1.1354| 1.1362| 1.1370
 131         | 1.1273| 1.1285| 1.1295| 1.1305| 1.1314| 1.1323| 1.1332| 1.1339
 134         | 1.1242| 1.1254| 1.1265| 1.1274| 1.1283| 1.1292| 1.1301| 1.1308
 137         | 1.1211| 1.1224| 1.1234| 1.1243| 1.1252| 1.1262| 1.1270| 1.1277
 140         | 1.1180| 1.1193| 1.1203| 1.1212| 1.1221| 1.1231| 1.1239| 1.1246
 143         | 1.1149| 1.1162| 1.1172| 1.1181| 1.1191| 1.1200| 1.1208| 1.1215
 146         | 1.1119| 1.1131| 1.1141| 1.1150| 1.1160| 1.1169| 1.1177| 1.1184
 149         | 1.1088| 1.1100| 1.1110| 1.1120| 1.1129| 1.1138| 1.1146| 1.1154
 152         | 1.1057| 1.1069| 1.1079| 1.1089| 1.1098| 1.1107| 1.1115| 1.1123
 155         | 1.1026| 1.1038| 1.1048| 1.1058| 1.1067| 1.1076| 1.1085| 1.1092
 158         | 1.0995| 1.1007| 1.1018| 1.1027| 1.1036| 1.1045| 1.1054| 1.1061
 161         | 1.0964| 1.0976| 1.0987| 1.0996| 1.1005| 1.1014| 1.1023| 1.1030
 164         | 1.0933| 1.0945| 1.0956| 1.0965| 1.0974| 1.0984| 1.0992| 1.0999
 167         | 1.0902| 1.0914| 1.0925| 1.0934| 1.0943| 1.0953| 1.0961| 1.0968
 170         | 1.0871| 1.0883| 1.0894| 1.0903| 1.0912| 1.0922| 1.0930| 1.0937
 172         | 1.0850| 1.0863| 1.0873| 1.0882| 1.0892| 1.0901| 1.0909| 1.0916
 174         | 1.0830| 1.0842| 1.0853| 1.0862| 1.0871| 1.0880| 1.0889| 1.0896
 176         | 1.0809| 1.0822| 1.0832| 1.0841| 1.0850| 1.0860| 1.0868| 1.0875
 178         | 1.0789| 1.0801| 1.0811| 1.0820| 1.0830| 1.0839| 1.0847| 1.0854
 180         | 1.0768| 1.0780| 1.0791| 1.0800| 1.0809| 1.0818| 1.0827| 1.0834
 182         | 1.0747| 1.0760| 1.0770| 1.0779| 1.0788| 1.0798| 1.0806| 1.0813
 184         | 1.0727| 1.0739| 1.0749| 1.0759| 1.0768| 1.0777| 1.0785| 1.0793
 186         | 1.0706| 1.0718| 1.0729| 1.0738| 1.0747| 1.0756| 1.0765| 1.0772
 188         | 1.0685| 1.0698| 1.0708| 1.0717| 1.0727| 1.0736| 1.0744| 1.0751
 190         | 1.0665| 1.0677| 1.0687| 1.0697| 1.0706| 1.0715| 1.0723| 1.0731
 192         | 1.0644| 1.0656| 1.0667| 1.0676| 1.0685| 1.0694| 1.0703| 1.0710
 194         | 1.0623| 1.0636| 1.0646| 1.0655| 1.0664| 1.0674| 1.0682| 1.0689
 196         | 1.0603| 1.0615| 1.0625| 1.0635| 1.0644| 1.0653| 1.0661| 1.0669
 198         | 1.0582| 1.0594| 1.0605| 1.0614| 1.0623| 1.0632| 1.0641| 1.0648
 200         | 1.0561| 1.0574| 1.0584| 1.0593| 1.0602| 1.0612| 1.0620| 1.0627
 202         | 1.0541| 1.0553| 1.0563| 1.0572| 1.0582| 1.0591| 1.0599| 1.0606
 204         | 1.0520| 1.0532| 1.0542| 1.0552| 1.0561| 1.0570| 1.0579| 1.0586
 206         | 1.0499| 1.0511| 1.0522| 1.0531| 1.0540| 1.0550| 1.0558| 1.0565
 208         | 1.0478| 1.0491| 1.0501| 1.0510| 1.0520| 1.0529| 1.0537| 1.0544
 210         | 1.0458| 1.0470| 1.0480| 1.0490| 1.0499| 1.0508| 1.0516| 1.0524
 212         | 1.0437| 1.0449| 1.0460| 1.0469| 1.0478| 1.0487| 1.0496| 1.0503




PUBLICATIONS ON THE UTILIZATION OF COAL AND LIGNITE.

A limited supply of the following publications of the Bureau of
Mines has been printed and is available for free distribution until
the edition is exhausted. Requests for all publications can not be
granted, and to insure equitable distribution applicants are
requested to limit their selection to publications that may be of
especial interest to them. Requests for publications should be
addressed to the Director, Bureau of Mines.

The Bureau of Mines issues a list showing all its publications
available for free distribution, as well as those obtainable only
from the Superintendent of Documents, Government Printing Office,
on payment of the price of printing. Interested persons should
apply to the Director, Bureau of Mines, for a copy of the latest
list.


PUBLICATIONS AVAILABLE FOR FREE DISTRIBUTION.

BULLETIN 58. Fuel briquetting investigations, July, 1904, to July,
1912, by C. A. Wright. 1913. 277 pp., 21 pls., 3 figs.

BULLETIN 76. United States coals available for export trade, by
Van. H. Manning. 1914. 15 pp., 1 pl.

BULLETIN 85. Analyses of mine and car samples of coal collected in
the fiscal years 1911 to 1913, by A. C. Fieldner, H. I. Smith, A.
H. Fay, and Samuel Sanford. 1914. 444 pp., 2 figs.

BULLETIN 89. Economic methods of utilizing western lignites, by E.
J. Babcock. 1915. 74 pp., 5 pls., 5 figs.

BULLETIN 119. Analyses of coals purchased by the Government during
the fiscal years 1908-1915, by G. S. Pope. 1916. 118 pp.

BULLETIN 135. Combustion of coal and design of furnaces, by Henry
Kreisinger, C. E. Augustine, and F. K. Ovitz. 1917. 144 pp., 1 pl.,
45 figs.

BULLETIN 136. Deterioration in the heating value of coal during
storage, by H. C. Porter and F. K. Ovitz. 1917. 38 pp., 7 pls.

BULLETIN 138. Coking of Illinois coals, by F. K. Ovitz. 1917. 71
pp., 11 pls. 1 fig.

TECHNICAL PAPER 34. Experiments with furnaces for a hand-fired
return tubular boiler, by S. B. Flagg, G. C. Cook, and F. E.
Woodman. 1914. 32 pp., 1 pl., 4 figs.

TECHNICAL PAPER 50. Metallurgical coke, by A. W. Belden. 1913. 48
pp., 1 pl., 23 figs.

TECHNICAL PAPER 76. Notes on the sampling and analysis of coal, by
A. C. Fieldner. 1914. 59 pp., 6 figs.

TECHNICAL PAPER 80. Hand-firing soft coal under power-plant
boilers, by Henry Kreisinger. 1915. 83 pp., 32 figs.

TECHNICAL PAPER 97. Saving fuel in heating a house, by L. P.
Breckenridge and S. B. Flagg. 1915. 35 pp., 3 figs.

TECHNICAL PAPER 98. Effect of low-temperature oxidation on the
hydrogen in coal and the change of weight of coal in drying, by S.
H. Katz and H. C. Porter. 1917. 16 pp., 2 figs.

TECHNICAL PAPER 123. Notes on the uses of low-grade fuel in Europe,
by R. H. Fernald. 1915. 37 pp., 4 pls., 4 figs.

TECHNICAL PAPER 133. Directions for sampling coal for shipment or
delivery, by G. S. Pope. 1917. 15 pp., 1 pl.

TECHNICAL PAPER 137. Combustion in the fuel bed of hand-fired
furnaces, by Henry Kreisinger, F. K. Ovitz, and C. E. Augustine.
1916. 76 pp., 2 pls., 21 figs. 15 cents.

TECHNICAL PAPER 148. The determination of moisture in coke, by A.
C. Fieldner and W. A. Selvig. 1917. 13 pp.

TECHNICAL PAPER 170. The diffusion of oxygen through stored coal,
by S. H. Katz. 1917. 49 pp., 1 pl., 27 figs.

TECHNICAL PAPER 172. Effects of moisture on the spontaneous heating
of stored coal, by S. H. Katz and H. C. Porter. 1917. 25 pp., 1
pl., 8 figs.


PUBLICATIONS THAT MAY BE OBTAINED ONLY THROUGH THE SUPERINTENDENT
OF DOCUMENTS.

BULLETIN 8. The flow of heat through furnace walls, by W. T. Ray
and Henry Kreisinger. 1911. 32 pp., 19 figs. 5 cents.

BULLETIN 11. The purchase of coal by the Government under
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TRANSCRIBER'S NOTES:

Page 5: Added period to the sentence: "If the coal used in the test
is to be analyzed, take a sample of from 4 to 6 pounds from each
barrow and throw it into a box near the scales.".

Page 11: Changed typo "calcuate" to "calculate."

Page 18: Changed typo "1.1854" to "1.0854", see intersecting
columns 184° F and 200 psi.

Page 19: Changed typo "Samuel Sandford" to "Samuel Sanford."