Engineering Bulletin No 1: Boiler and Furnace Testing | Page 2

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