656

THE COLLIERY GUARDIAN’.

October 6, 1916.

CURRENT SCIENCE

Pulverised Fuel for Locomotives.

J. E. Muhlfeld states that the use of pulverised fuel
for locomotives enables firebox temperatures and sus-
tained boiler capacities to be attained equivalent to and
exceeding those obtainable with crude or fuel oil. It
eliminates waste products of combustion and fire
hazards, and permits the enlargement of exhaust steam
passages, thus producing increased efficiency of the
cylinders. Pulverisation permits of the use of such fuel
as cannot readily be disposed of by mine operators in
the commercial trade, and provides for the utilisation of
existing refuse, and of lignite and peat. It renders
possible the elimination of smoke, soot, cinders, and
sparks, and increases the time available for transporta-
tion use. It dispenses with the necessity for grates,
ashpans, and trailing trucks, thereby increasing the
percentage of total locomotive weight available for the
development of drawbar pull.

The first steam railway locomotive of any considerable
size to be fitted up in the United States or Canada and,
so far as is known, in the world, with a successful self-
contained equipment for the burning of pulverised fuel
in suspension, was a 10-wheel type on the New York
Central. This locomotive has 22 by 26 in. cylinders,
69 in. diameter drivers, 200 lb. boiler pressure, 55 sq. ft.
grate area, 2,649 sq. ft. heating surface, and has a
tractive effort of 31,0001b. It is equipped with a
Schmidt superheater and Walschaert valve gear, and
was first converted into a pulverised fuel burner during
the early part of 1914. The general features of the feed
device used are shown in the illustration.



Steam Turbine Feed for Pulverised Fuel.

In the application of the arrangement to existing types
of steam locomotives, the diaphragm, table, and
deflector plates, nettings, hand holes and cinder hoppers
are removed from the smoke-box and the exhaust nozzle
opening is enlarged. The grates, ashpan, firedoors and
operating gear are removed from the firebox, and a fire-
brick-lined firepan, slagpan, and primary arch, together
with the fuel and air mixers and nozzles, are fitted. The
usual arch tubes and brick arch are utilised. In the cab
the firedoor is replaced with a furnace and the fuel and
air supply regulating levers are installed. The tender
equipment includes the enclosed fuel container and the
apparatus for feeding, mixing, and discharging the fuel
and air, together with the steam turbine or motor
operating mechanism. The engine and tender connec-
tions consist of one or more hose from the fuel and
pressure air outlets on the tender to the nozzles on the
engine. Flexible metallic conduits are used to convey
the fan and fuel feeding motive power.

For firing up a locomotive the usual steam blower is
turned on in the funnel, a piece of lighted waste is then
entered through the firebox door opening and placed on
the furnace floor, just ahead of the primary arch, after
which the pressure fan and one of the fuel and pressure
air feeders are started. From 45 to 60 min. is ordinarily
sufficient to get up 2001b. steam pressure from boiler
water at 40 deg. Fahr.

The prepared fuel, having been supplied to the
enclosed fuel tank, gravitates to the conveyor screws,
which carry it to the fuel pressure air feeders, where it is
thoroughly mixed with and carried by the pressure air
through the connecting hose to the fuel and pressure air
nozzles and blown into the fuel and air mixers.
Additional induced air is supplied in the fuel and air
mixers, and this mixture, now in combustible form, is
induced into the furnace by the smoke-box draught. The
flame produced at the time the combustible mixture
enters the furnace obtains its average maximum
temperature, from 2,500 to 2,900degs. Fahr., at the for-
ward combustion zone under the main arch, and at this
point auxiliary air is induced by the smoke-box draught
to finally complete the combustion process. The
uniformity with which locomotives can be fired is indi-
cated by the fact that the regularly assigned firemen can
maintain the steam within a variation of 2 lb. of the
maximum allowable pressure without blowing off. As
each of the fuel and pressure air feeders have a range in
capacity of from 500 to 4,0001b. of pulverised fuel per
hour, and as from one to five of these may easily be
applied to the ordinary locomotive tender, there is no
difficulty in meeting any desired boiler and superheater
capacity.

The smoke-box gas analysis will average between 13
and 14 per cent, of CO2, when coal is fired at the rate of
3,0001b. per hour, between 14 and 15 per cent, at the
rate of 3,5001b. per hour and between 15 and 16 per cent,
at the rate of 4,0001b. per hour, so that as the rate of
combustion increases there is no falling off in the
efficiency, as obtains when coarse coal is fired on grates.
The waste of fuel from the stack, where coal having a
large percentage of dust and slack is used; the lowering
of the firebox temperature and draught, due to opening

AND TECHNOLOGY.

of the firedoor, and the resultant variation in steaming
and general results under high rates of burning fuel on
grates, where all the foregoing factors are involved, are
eliminated.

The liquid ash runs down the underside of the main
arch and the front and sides of the forward combustion
zone of the furnace, and is precipitated into the self-
clearing slagpan, where it accumulates and is air-cooled
and solidified into a button of slag which can be dumped
by opening the drop-bottom doors.—Railway Gazette.
Spontaneous Ignition of Coal.

A. P. Bruigum rejects the ordinary explanation that
spontaneous ignition of coal is due to the presence of
iron pyrites, because if iron pyrites, in small grains and
moistened with water, be exposed to a stream of oxygen,
there is hardly any appreciable rise of temperature, even
when the oxygen is charged with ozone. Indirectly, the
presence of iron pyrites may assist a reaction primarily
due to other causes, through the production of a layer of
ferrous oxy-sulphate; but the main cause must be sought
for elsewhere. After extracting coal with benzol, to
remove bitumen, and with caustic soda, to eliminate
humic acid, the residue consists of humin (made up more
or less of cellulose), to which is due the weathering and
deterioration of coal, with loss of carbon and hydrogen
and increase in the percentage of oxygen and of ash, and
a fall off in the heating value. This weathering is most
pronounced in the layers most exposed to the air. If the
coal be dry the weathering is very slow, but if damp is
greatly accelerated. The yield of tar from weathered
coal is much less than from fresh coal, but is richer in
paraffins. During weathering the humin undergoes
gradual combustion, and the humic acid undergoes
changes in presence of oxygen, under the action of
microbes, with formation of CO2. This acid takes up
ozone, with which it forms ozonides, which are decom-
posed-in presence of moisture, liberating heat and
carbon dioxide. In the absence of ozone coal absorbs a
good deal of oxygen, but holds it simply as an absorbed
gas. The process of chemical combination is very slow
at ordinary temperatures, but becomes rapid when the
temperature is raised; concurrently the absorption of
oxygen is greater. The reaction therefrom tends to pro-
duce progressively rising temperatures, culminating in
some cases in spontaneous combustion. For an effective
start, however, ozone is essential, and this is formed
wherever evaporation of water takes place. A damp
heap of coal is, therefore, bound to start weathering; and
if the circumstances are favourable to this the tempera-
tures will begin to rise, and the inactive oxygen begin to
fall in the process of destruction. This explains why
warm weather after rain is dangerous to coal in heaps,
and why sea air, laden with ozone, is dangerous to the
coal in ships’ bunkers; and it would appear that ventila-
tion of the coal may import its own special risks. There
is never any risk of spontaneous combustion of coke or
of anthracite, the humic acid and humin of coal causing
the phenomena of weathering, heating, and spontaneous
ignition.—Coal Trade Bulletin.

INDUSTRIAL FATIGUE.

The second interim report on an investigation of
industrial fatigue by physiological methods, by A. F.
Stanley Kent, M.A., D.Sc. (Oxon), Professor of
Physiology in the University of Bristol, has just been
issued.* The report describes a continuation of former
experiments on industrial fatigue undertaken on behalf
of the Home Office and described in & previous report.f
Seven factories in all were visited. Investigations were
carried on at one of these for a period of three and a half
months, shorter periods being devoted to most of the
others. Many of the results presented were obtained
during investigations at two factories. The first of these
employed about 2,000 hands, and was engaged princi-
pally in the manufacture of surgical dressings for the
Army in the field. The whole of the processes required
to produce the finished article from raw material are
carried out in this mill, from the opening of the bales of
cotton to the packing of the completed dressings ready
for despatch to the front. These operations include,
besides opening and packing, carding, spinning,
winding, warping, sizing, weaving, bleaching, drying,
impregnating with antiseptic, re-drying, examining,
winding, cutting into bandages, weigh in e. and com-
pressing. The- second factory was an engineering works
employing about 600 men, besides many women, and
engaged in the manufacture of war material, from
turbines for large ships to the steel shields used in the
trenches. Male and female labour was employed in
both factories, and examples of both are given in the
results. A special investigation was carried out in order
to ascertain whether members of the office staff suffered
from undue fatigue. It is, perhaps, unnecessary to
emphasise the importance of any means which is
capable of giving reliable indications of the development
of fatigue in munitions factories, where it is desirable to
secure maximum output, but where it is also essential
to conserve the health and energies of the workers.

Section I. draws attention to the progressive develop-
ment of fatigue throughout the week, and to the con-
comitant diminution in the power of recovery, to the
development of extra fatigue as a result of overtimed to
the disadvantage of working consecutive overtime days,
to the development of fatigue during day and night
shifts, with arguments for their less frequent reversal,
to the process of ordinary recovery from fatigue, to
recovery during rest intervals, and to recovery compli-
cated by illness.

-*CU 833.5r_pric7,~isr6ffi	~

f Cd. 8056. See Colliery Guardian, October 1, 1915, p. 672.

| “ Overtime ” here means generally the hours 6 p.m. to
8 p.m. worked at the end of a day commencing at 6 a.m.

Section II. deals with the existence of periods of high
and of low output, especially where overtime is worked.
Attention .is called to the gradual change in the period
of lowest output as fatigue develops during the week, to
the fact that in certain cases overtime invariably pro-
' duced the lowest output, and that this may be traced to
fatigue, to the inability of the workers to respond
efficiently to a call for extra overtime on a Saturday,
after a week's work, to the differences with regard to
output between two groups of workers (lint packers and
boracic lint packers) doing similar work, but differing as
regards overtime, to the evidence that the working of
overtime may lead, not to an increase, but to an actual
diminution of output, to the occasional appearance of
special circumstances affecting the output of individuals,
and, generally, to the important influence of home con-
ditions upon the development of fatigue and upon the
consequent diminution of output. The value of rest
intervals also must be emphasised. An interesting,
though perhaps less important, matter is the curious
condition of lower efficiency exhibited by workers on
Monday morning.

With reference to these phenomena, it will be recog-
nised that a progressive diminution of the power of the
worker to resist fatigue, or to recover from it, if present,
affords a strong argument against the practice some-
times adopted of employing Sunday labour. For in
normal times the lessened efficiency found towards the
end of the week is remedied by the rest obtained on
Saturday afternoon and Sunday, but where Sunday
labour is introduced, the rest is inadequate, and the con-
dition of fatigue becomes permanent. Even this is not
the full extent of the evil, since the fatigue produced
by a full week’s work, added to that already existing,
will produce a condition at the end of the second week
worse than at its beginning. The process will continue
from week to week, until either the worker breaks down
under the strain, or, a more probable result, equilibrium
is brought about. The manner in which such equili-
brium may be produced is described. In either case,
the result will be disastrous from the point of view of
output, and frequently from the point of view of health
also. The case is very similar when daily overtime is
considered, though, owing to the interruption of work
which the necessary experiments would entail, it has
not been, shown directly that the power of recovery from
fatigue becomes progressively less during the day. It
has, nevertheless, been proved that the output of workers
during the overtime period is far less than the output
during the hours of normal labour. And the results of
experiments seem to indicate that this lessening of
output in the period of overtime is due to fatigue.

It should, perhaps, be pointed out that in factories
where the output depends almost entirely upon the
number of hours the machinery can be kept running,
and the direct influence of the operatives is small, it
may be desirable to preserve overtime, though even
here a better arrangement would be the introduction of
a fresh shift. The fact that certain workers who were
placed under observation were found to lose 25. 18, and
27 per cent, of their time in different periods of the day
is significant. This loss of time is a factor in the process
referred to as “balancing.”

Another point to which attention is directed is the
practice which exists amongst some individuals of going
to their work in the early morning without having taken
food. Results bearing upon this point are shown, where,
of five workers, one who came breakfastless to the mill
proved to be inferior as regards output during the early
morning hours to the others who had taken food;
similar results were obtained in other experiments.

Consideration is given to the means by which maxi-
mum output may be obtained, whilst the influence of
overtime upon the general health of the worker is
treated in the report.

The work has been in progress for some years. It is
now occupying the whole time of three investigators.
Not only have the circumstances of labour been studied,
but also the home conditions of the workers, their general
health, and other factors which seem likely to influence
their reaction to the present abnormal conditions.

The report is divided into three sections, the first
dealing with fatigue as a result of overtime, the second
dealing with the influence of fatigue and of overtime
upon output, whilst the third section de-als with more
general matters. In this section is -included also a
reference to a question of especial interest at the present
time, viz., the general effect of long-continued overtime
upon the worker (exhaustion and ultimate breakdown,
recovery in spite of inadequate rest periods, equilibrium
and “ balancing ”).

Fatigue as a Result of Overtime.

Fatigue indicates a state of diminished efficiency
occurring after labour, and partly dependent upon it.
The degree of fatigue is determined partly by the dura-
tion and character of the labour performed, and partly
by a variety of circumstances outside the mill, amongst
which the home conditions of the worker are important.
Labour is not the sole cause of fatigue. Illness, indis-
position. and lack of food may be contributory. Illness
and indisposition may greatly diminish the power of
recovery. Existing industrial conditions lead to an
increase of the normal development of fatigue and to a
diminution of the normal power of recovery. Members
of the office staff may show signs of fatigue and over-
strain equally with the factory hands. Development of
fatigue and recovery are concomitant processes. The
rates of the accumulation and disappearance of fatigue
are- determined by the relative activity of production and
recovery. Ordinary tests give the resultant of these two
processes, which is useful practically, as indicating the
existing state, or “ fitness,” of the worker.

Development of fatigue preponderates during labour,
recovery preponderates during rest. During the day
fatigue accumulates. During the night the accumulation
is dissipated. The effect, however, of the recovery may
not show itself on Monday, when co-ordination is dis