532

THE COLLIERY GUARDIAN.

March 16, 1917.

the car. Two 1’adlefuls are usually taken from a car, one
from one side and the other from the other side at the
opposite end, thereby obtaining portions from different
parts of the car. Gare is observed not to collect por-
tions of the first or last coal spilling from the car, for
the moisture content or proportions of foreign matter in
such coal may render the sample unrepresentative. If
circumstances permit, the ladle is shifted and filled from
different sections of the stream of falling coal. At one
of the three railroad terminals loading at Hampton
Roads, Virginia, the Bureau has installed a crusher for
crushing the gross samples to in. mesh and finer,
and parting devices for reducing the samples in quantity,
thereby eliminating the hand preparation of samples.
It is proposed to instal crushers and equipment at the
other two points.

Though the collector may use the shovel or ladle to
the best of his ability, these tools may collect portions
of coal that do not contain lump coal in the same pro-
portion that exists in the car. Especially may this occur
f the coal contains a large proportion of lumps of con-
siderable size. In that event, the collector should collect
portions of lumps from time to time, and add them to the
sample. Necessarily, the collector must be relied upon
to collect a sample under these conditions that will fairly
represent the proportions of lump and slack coal con-
tained in the coal sampled, and it follows that the
collector must have experience in sampling, and be able
to judge the coal and the sample.

In collecting samples from coal as it is unloaded from
a ship, the same general instructions apply: the cargo
being systematically sampled during the entire period
of unloading, so that samples will be collected which
represent the quantity as a whole. If unloaded by grab
buckets, shovelfuls should be collected at regular
intervals from the buckets or barrows. If the coal is
crushed immediately after it is unloaded, it is prefer-
able to collect samples from the crushed coal.

Sample Receptacle.

As the wagons or railroad cars may arrive irregularly
at the building or plant and the coal be intermittently
unloaded, a metal receptacle or wooden box of a size to
hold a gross sample of at least 1,0001b., with a tight-
fitting lid which can be locked, is required for holding
the portions of coal taken from each wagon or car until
the gross sample is completed. In sampling cargo
deliveries, buckets holding 60 to 701b. may prove more
satisfactory to use for receiving the portions making up
a gross sample, as the samples are usually worked down
as the loading progresses, and the buckets are convenient
for carrying the coal to the space available for preparing
the gross samples. If the gross samples are stored, a
box should be provided, or else a sufficient number of
buckets with tight-fitting lids and locks should be avail-
able in order to preserve the integrity of the sample.
The buckets, boxes, or receptacles should be inspected
each time before using and thoroughly cleaned to remove
the coal dust remaining from previous samples and any
foreign matter that may by chance be in them.

Special Moisture Samples.

Special moisture samples must be, in a sense, grab
samples, and must be collected, prepared, and placed in
a sealed container with as little delay as possible. If a
gross sample is collected during a period of a few hours
or a very few days, and the sample is collected and
stored under conditions that will preserve its moisture
content, a special moisture sample may be collected from
the gross sample after it has been rapidly crushed, so
that it will all pass through a 1 in. screen (the fineness to
which the gross sample is reduced by the first crushing).
It should be collected in a place comparatively cool and
protected from rain, snow, wind, and the sun’s rays. A
small scoop may be used, having a capacity of about lib.
of coal—a scoop with bottom about 2J in. wide and 8J in.
long and vertical sides about 2 in. high is about the right
size. As the crushed coal is shovelled into a conical
pile, scoopfuls should be regularly and systematically
collected so that approximately one scoopful will be
collected to every two shovelfuls (about 30 lb.) deposited
on the cone, thereby collecting a special moisture sample
weighing from 30 to 50 lb. As the scoopfuls are collected
they should be placed in a receptacle which can be
tightly closed. After the gross sample has been formed
into a conical pile, and the special moisture sample
weighing 30 to 501b. has been accumulated, the special
moisture sample should be immediately and rapidly
crushed so that no pieces of coal or impurities are larger
than i in.; and it should be rapidly coned, flattened, and
quartered, and a mailing can filled by taking portions
from each quarter by use of the scoop (each portion only
partly filling the scoop). The mailing can should be
properly sealed at once, and forwarded to the laboratory.'

Preparation of the Gross Sample.

The- portions taken in making up the gross sample
should be immediately placed in a box or a receptacle
having a tight-fitting cover and a lock, for storage in
order to preserve its integrity until it is reduced to a
quantity convenient for transmitting to the laboratory.

The proper preparation of a gross sample for shipment
to the laboratory involves three operations :—(1) Crush-
ing, (2) mixing, and (3) reduction in quantity. The
operations proceed in stages until the final sample is
obtained.

The crushing may be done by a mechanical crusher
or by hand with an iron tamping bar or sledge on a
smooth, clean sheet iron plate, of suitable dimensions,
or on a solid floor—in the absence of a sheet iron plate
or smooth tight floor, the' crushing may be done on a
heavy canvas—to prevent the accidental admixture of
any foreign matter. The mixing and reduction may be
done by hand with a shovel, or mechanically by means
of riffles or sampling machines.

It is obvious that if the gross sample is reduced in
quantity without crushing, the effect of the selection or
rejection of one or more of the large pieces of slate or

other impurities in the portion of the sample retained
multiplies rapidly as the sample becomes smaller. To
illustrate : A sample of 1,000 lb. contains a piece of slate
weighing 1 lb., which is one-tenth per cent, of the weight
of the gross sample. If the sample is halved in quantity
without crushing, the half of the sample retained for
further reduction will contain two-tenths per cent, ash
more or less than the rejected half, according to whether
the. piece of slate went into the retained half or into the
rejected half. In halving the 5001b. sample, the lib.
piece of slate would have an effect of four-tenths per
cent, on the ash content of either the retained or rejected
half. If, in continuing the reduction of the sample by
halving each time, the lib. piece of slate by chance
should fall into the retained half on each successive
halving, it would have an effect of 12-8 per cent, on a
7if lbsample—that is, in halving the 15flb. sample
the 1 lb. piece of slate would cause the ash content of
one-half of the sample to be 12-8 per cent, higher than
the other; in other words, if the average ash of the coal
is 10 per cent., one of the 7f|lb. samples would show an
ash content of 22*8 per cent. This fundamental prin-
ciple that the weight of the largest piece of impurities
should be relatively very small in ratio to the weight of
the sample at each halving is recognised in the instruc-
tions for sampling issued by the Bureau of Mines, which
specify that the sample should be successively crushed,
mixed, and reduced.

AVhen prepared by hand, the pieces of coal and
impurities should be crushed to sizes not greater in any
dimension than the sizes indicated in the following
table before each reduction of the sample into two
approximately equal parts :—

Size of Coal and Quantity required for each
Reduction.

Weight of

Largest size of coal and impurities sample to
allowable in sample before division. be divided.

One inch ............................ 1,000	or	more.

Three-quarters of an inch ............ 500

One-half inch ........................ 250

Three-eighths of an inch ............. 125

One-quarter of an inch ................ 60

Three-sixteenths of. an inch, or 4-mesh

screen................................ 30

Diagram Showing the Treatment of a 1,000-lb. Sample.
l,0r0-lb. gross sample, crush to 1 in. mesh ; mix
by coning and long-pile method ; halve by
alternate shovel method.

500	5<’O lb , crush to % in. mesh; mix by coning-and long pile method; h alve by alternate shovel method.
250	250 lb , crush to | in. mesh ; mix by coning method ; halve by quartering method.
125	125 lb., crush to fin. mesh; mix 1 y rolling on blanket; halve by quarte>ing method.
62|	62|lb., crush to fin. mesh; mix and halve by blanket and quartering method.
31|	31f lb , crush to in. or 4-mesh ; mix and halve by blanket and quartering method.
i5i	15s lb.: mix and halve by blanket and quarter- ing method.

------7H lb.

I	Fill 5-lb. container and mail to laboratory.

lb.

Fill 5-lb. container
for reserve sample.

Care should be exercised to crush finely pieces of
foreign matter before each reduction, so that the crushed
impurities can be distributed through .the sample, and
when crushing to keep pieces of slate and other
impurities from flying out of the sample. In crushing
the coal on wood, brick, cement, or on floors of such
materials, splinters or small fragments may be broken
from the floor and be mixed with the sample. Such
floors, if used, should be thoroughly clean and free from
cracks. If a sheet iron plate is used, it should be free
from rust.

After each crushing, the sample should be thoroughly
mixed before reduction in quantity. The method which
gives generally satisfactory results is as follows :—The
crushed coal is formed into a conical pile by depositing
each shovelful of coal on top of the preceding one. As
the shovelfuls are deposited, the fine material forms the
apex of the cone, while the coarse particles roll down
toward the base. By walking around the cone, and
systematically depositing shovelfuls on the apex of the
cone from every side, care being taken to maintain the
original form, the sampler will properly distribute the
fine and coarse coal. A new, long pile is then formed
by taking a shovelful at a time (as the sampler fills the
shovel he should walk around the cone, thus systematic-
ally removing the coal from the base of the cone) and
spreading it out in a straight line or ribbon the width of
the shovel; the length is 5 to 10 ft. for a shovel holding
about 15 lb. Each new shovelful is spread over the top
of the preceding one, beginning at opposite ends, and so
on until all the coal has been formed into one long pile.
The sample is then halved in quantity by shovelling the
long pile to one side, alternate shovelfuls being discarded
while the retained shovelfuls are formed into a new cone.
In shovelling the coal from the long pile, the sampler
takes the shovelfuls of coal systematically around the
pile, advancing at each shovelful a distance about equal
to the width of the shovel, thereby preserving the
symmetry of the form of the pile. If the pile should be
reduced by shovelling all of the coal from either end, and
if the alternate shovelfuls discarded contained coal
mainly from the sides of the pile, the rejected half of
the sample would contain a preponderance of coarse coal,
while the retained half would contain relatively too much
fine coal. This is because the coarse coal rolls down the
sides of a pile or cone, while the fine coal builds up, so

that the .relative proportions of coarse and fine coal in
outer and inner portions of the pile are quite different.
The alternate shovelfuls of coal which are retained are
formed into a new cone.

In coning, care should be observed to deposit each
shovelful so that the centre of the cone as started will
not be drawn to one side, for in quartering a cone, the
centre of which has been drawn, two opposite quarters
will contain an excess ratio of fine material, while the
other two quarters will contain a deficiency. This will
be apparent when it is considered that when a cone is
formed, the fines build up the apex while the coarse
particles roll down the sides.

After the gross sample has been reduced by the coning,
long pile, and alternate shovel methods to approximately
2501b., the sample is further reduced in quantity by the
quartering method. Before each quartering, the sample
is thoroughly mixed and made into a conical pile, as
follows :—Quantities of 125 to 250 lb. are shovelled into
a new conical pile by depositing each shovelful of coal
on top of the preceding one; quantities less than 125 lb.
are placed on a suitable cloth, measuring about 6 ft. by
8 ft., and mixed by raising first one end of the cloth and
then the other, rolling the coal back and forth. After
the coal is thoroughly mixed, it is formed into a conical
pile by gathering together the four corners of the cloth.

The conical pile is quartered as follows :—The cone is
flattened, its apex being vertically pressed down with a
shovel or a board, so that each quarter contains the
material originally in it. The flattened mass, which
'should be of uniform thickness and diameter, is then
marked off into quarters with a board held edgewise, or
a piece of sheet iron, along two lines that, intersect at
right angles directly under the apex of the original cone.
The diagonally opposite quarters are shovelled away and
discarded, and the spaces they occupied brushed clean.
The coal remaining is successively mixed, coned, and
quartered on the canvas until two opposite quarters are
about equal to the quantity (approximately 5 lb.) required
to fill the sample container for shipment to the labora-
tory. If after two opposite quarters are placed in the
sampling container, it is found that the container is not
compactly filled, the other two quarters should be mixed,
coned, flattened, and quartered, and the remaining
space in the container then filled by taking equal seg-
ments from opposite quarters, using a sampling scoop.
The two rejected quarters are not thrown into the discard,
but are placed in a sampling container, hermetically
sealed, and held in reserve at the delivery point until
report of analysis of the regular sample is received and
settlement made for the coal.

Accuracy in reducing the gross samples requires that
the coal be crushed as directed, thoroughly and syste-
matically mixed, formed in piles, and accurately divided,
either by the alternate shovel method or by quartering,
so that the rejected portions and the retained portions
will be uniform in character and weight. Thorough
cleanliness must be maintained during the entire opera-
tion.

If the contract amounts to a considerable quantity,
necessitating several samples in relatively short periods,
the installation of a crusher has been found in some cases
expedient and economical for reducing the gross samples
to -f^in. mesh, or finer, and in such case reducing
buckets or a mixing and reducing machine are used.
Even though the contracts are relatively small and the
samples are crushed by hand, the use of the reducing
bucket or machine is recommended. These devices are
generally used after the gross sample has been mixed,
and has been reduced by the “ alternate shovel ” and
quartering method to about 60 lb.

After the gross sample has been reduced to less' than
250 1b., a shovel takes too large a proportion of the coal,
making further reduction by alternate shovelfuls unre-
liable. The quartering method is used after the sample
has been reduced by alternate shovels to approximately
250 1b., as the capacity of an ordinary shovel is out of
proportion to the size of the sample. It may prove
desirable in sampling coal containing considerable quan-
tities of free impurities of uneven size to use small
shovels of 101b. and less capacity in reducing the gross
sample by alternate shovels, for as the size of the shovel
is diminished the number of fractional parts into which
the sample is divided is increased. As the sample
becomes smaller, greater precision in quartering is
required, and, consequently, refinements in the manner
of mixing and reducing should be introduced. The use
of buckets or the machine makes thorough mixing
possible, and the riffles ensure accurate division.

When mechanical crushers are used, the sample 'should
be inspected before or while being fed to the crusher to
make certain that the sample does not by chance contain
a piece of iron, such as a tie spike or some other highly
abrasive substance, accidentally loaded with the coal in
the mine and undetected in collecting the sample, other-
wise the abrasion of the iron may introduce errors which
would alter appreciably the final results.

Hull Coal Trade. — The coal brought into Hull during
February amounted to 213,644 tons (200,315 tons by rail
and 13,329 tons by river). The quantity a year ago was
265,063 tons. No figures relating to exports, coastwise or
foreign, are available.

Coal Contracts. — The Controller of Coal Mines Iras
addressed a special note to coal owners, factors, and mer-
chants, pointing out to them the necessity of refraining at
the present time from making forward contracts for longer
periods than three months. “It is becoming urgently
necessary,’’ he says, “ that special efforts should be made
to relieve the congestion of transport on the railways, and,
with this in view, the need for limiting the scope of future
commitments will be obvious to all concerned.” Great
benefit would result from sustained efforts to ensure that
all descriptions of coal be purchased from collieries situated
as near as possible to the consuming points, thus securing
the minimum of haulage and resultant economy in the use
of both wagons and locomotives.