May 17, 1918.

THE COLLIERY GUARDIAN.

999

REFRACTORY MATERIALS IN GAS-
WORKS.*

By J no. P. Leather.

In a gasworks, profits are said to be made or lost
in the retort house, and the central point in the
retort house is the retort bench constructed of refrac-
tory materials. On the proper quality, disposition
and use of these materials, largely hangs the success
of the whole operations of a gas undertaking.

The main structure and walls, the producer, the
regenerator, the combustion chamber, and finally the
retorts themselves might each be separately con-
sidered. The author proposes, however, to deal first
with certain primary characteristics which are
required in all these situations, and afterwards to
refer to other properties desirable in special positions.

Firstly, capacity to resist deformation by the pres-
sure of the superstructure when exposed to an elevated
temperature. It is not sufficient to speak of the
temperature of fusion or softening. Any test of
fusibility ought to be accompanied by a deforming
force, and in this again the time should be taken
into account. The testing of firebrick as at present
carried out attempts to discount the effect of time
and pressure by requiring the material to stand for
a short time and with very little deforming force a
much higher temperature than appears in practice.
The argument apparently is this :—A gas retort which
sustains for a lengthy period the stress of actual
work at a temperature of, say, 900 degs. Cent., gives
way in a short time with a very small stress at a
higher temperature of, say, 1,400 degs. Cent. There-
fore, if a material does not show signs of fusion in
a short test at, say, 1,700 degs. Cent., it will probably
stand indefinitely in actual work. This argument may
have a certain amount of truth in it, but is not
entirely convincing unless actual experience or experi-
ment discloses some definite relation between these
various elements of temperature, time and stress.
Thus we are driven, if we seek to improve and progress
in our methods, on the old way of using one material,
and if it fails, trying something else. Failures are,
however, so expensive, that we prefer to keep to old
tried materials and leave someone else to experiment.
This is inimical to progress.

Collapse under Pressure.

In the combustion chamber the bricks have to stand
a temperature of at least 1,500 degs. Cent. It would
be better if we could rely on them not yielding at
even 1,600 or 1,650 degs. Cent., as in order to have
a sufficiently high temperature at every point some
parts must be considerably hotter. Often heats have
to . be checked for no other reason than the fear of
damage to the brickwork. In many settings the walls
of the combustion chamber support the upper tiers
of retorts, and it is possible that in places the weight
may exceed one ton per square foot. It requires a
high quality of silica brick to maintain this stress for
an indefinite period at 1,500 degs. Cent.

There is a great difference between a brick wall
heated on both sides to the same temperature and
one which is at a high temperature on one side and
a low temperature on the other. In the latter case
only a part of the brick is at the high temperature,
and a much higher temperature can be withstood with-
out yielding.

Secondly, it is important that the size of the
material should not alter otherwise than by the
unavoidable dilatation with heat and the subseqeunt
resumption of the original size when cooled. The
liability of refractory materials to permanent change
of size, either by expansion or contraction, is very
inconvenient, and particularly so in vertical retort
settings. As some parts of the setting are necessarily
at a much higher temperature than others, irregular
expansion or contraction leads to cracked or leaky
retorts, and in the generator to by-passing of
secondary air with resultant losses difficult to remedy
and costly in their effect. Whether this defect is to
be obviated by increased temperature in the manufac-
turer’s kiln, or by the different choice of materials,
the need of eliminating change of size in use is
imperative. It must be remembered that a contrac-
tion of 0’5 per cent, in a 25 ft. retort amounts to
1’5 in.

Resistance to Chemical Action.

The third desideratum is a material which will be
less affected by the chemical action of dust, slag and
reducing atmosphere. If a material could be found
to resist these influences at a high temperature it
would be very convenient and advantageous to the
gasworks manager. The brick manufacturer, on the
other hand, may reply that it is the duty of the user
to avoid in his furnaces the production of slag, and
so arrange that dust does not come into contact with
bricks at a high temperature. With regard to
reducing atmosphere, apart from the inside of the
retort, the chief reducing agent is carbon monoxide.
Research on this matter is not complete, but the
author is inclined to think that carbon monoxide has
not a great effect on refractory material in the absence
of dust, i.e., in the absence of excessive quantities
of oxide of iron and like substances. A user ought
not to ask the manufacturer to provide a brick with
special qualities to overcome difficulties which may
be avoided by the method of working. It is a well-
known fact that there is little or no direct chemical
action between two solid substances. In order to
bring about such mutual action it is necessary either
to introduce a liquid which has a solvent action on
one or both substances, or else to raise the temperature
until one of the substances begins to fuse. Dust has
little effect on firebrick if the temperature does not
approach its melting point.

If flue passages are of sufficiently large dimensions
to avoid a cutting draught a minimum of dust goes
forward into the parts of the setting where the tem-
perature is high. In the producer dust is unavoid-
able, but it is not in the producer that we require
the heat, but in the retorts. The temperature in

* Paper presented to the meeting of the Ceramic Society.

the producer should be kept so low that the ash does
not melt. This may be brought about either by the
use of sufficient steam, or by introducing waste gases
into the producer with the primary air. Inside the
retort the atmosphere is much more strongly reducing
than in the furnace or flues, and I have yet to see
evidence of the inside of the retort melting under
its influence.

Mechanical Strength.

The crushing stress which firebricks should be able
to stand is seldom as high as two tons per square foot,
and is therefore much less than ordinary red bricks
are regularly subject to. Such a stress is not
important except when combined with elevated tem-
perature. Mechanical strength of another kind is,
however, called for in the producer. Here it is not
always possible to avoid all formation of slag which
melts and corrodes the surfaces of the bricks. The
slag runs down until it reaches a part where the
temperature is lower, and then it clings to the brick-
work and has to be removed by the process of clinker-
ing. The material should therefore have great
tenacity.

In the regenerator and in the walls of the retorts
greater thermal conductivity would be desirable if
it could be obtained without countervailing disadvan-
tage. It would, however, be necessary to guard
against uneven expansion if the' high conductivity
bricks had a different coefficient of dilatation from the
other bricks used in the structure. Such uneven
expansion might lead to cracks or open joints through
which air could pass and neutralise the whole value
of recuperation.

Porosity.

Porosity is desirable. In the intermittently charged
retort the sudden introduction of cold coal into the
retort previously raised to its maximum temperature
introduces a condition which, if the material is too
dense, is liable to cause cracks. To secure that the
retort shall not crack with sudden change of tempera-
ture, the standard specification demands a certain
porosity. Possibly this diminishes conductivity, but
of two evils a leaky retort is worse than low con-
ductivity.

To recapitulate: the chief requirement in a fire-
brick used in a retort setting is that it should not
alter in size or shape under the combined influence
of pressure and high temperature, and for some pur-
poses the desiderata are a better conductivity and
maintenance of integrity under sudden changes of
temperature.

Firebricks are also used in gasworks for carburetted
water gas plants. The chequerwork of superheaters
or fixing chambers are subject to the action of oil
vapour at a varying temperature of from 650 degs.
Cent, to 800 degs. Cent. Some bricks appear liable
to disintegration under these conditions, probably due
to imperfect burning in manufacture.

Lastly, attention may be drawn to the desirability
of regular size and accuracy of shape in fireblocks
and bricks. Probably this is largely a question of
securing an even and sufficient temperature in the
kiln, though possibly sometimes not sufficient care is
taken in the preparation of the clay before moulding.

THE IRISH COAL TRADE.

Thursday, May 16.

Dublin.

Matters are becoming increasingly difficult for the coal
trade, supplies now being very scarce. Bellmen demon-
strated last week as a protest against their inadequate
rations of coal. Later, a conference was held at the
offices of the Shipping Controller. It was decided to
appoint a committee of the merchants to draft proposals.
As a result of a conference at the Mansion House last
week, the probability of serious trouble in the coal carry-
ing trade has been averted, it being agreed to submit the
matters at issue in the dispute at the Dublin General
Steamship Company’s yard to arbitration, pending which
there will be no further cessation of work. Prices of
coal remain unchanged, viz. :—Best Orrell, 51s. per ton;
best Wigan, 49s.; standard coal, 46s. 6d. per ton,
delivered; coke, 49s. per ton. Irish coal at Castlecomer
pits (County Kilkenny):—Best small coal, 30s. per ton;
best large coal, 28s. 4d.; bottom coal, 25s.; breakage,
16s. 8d.; culm, 13s. 4d. per ton. The quantity of coal
discharged upon the quays from cross-Channel ports was
only 18,887 tons, as compared with 30,000 tons the week
previously. It is expected that operations at the Wolf hill
Collieries, Queen’s County, which have been suspended for
some months past, will be resumed at an early date. At
a meeting of the Southern Coal Committee at Limerick
Junction, it was urged, in view of the tonnage shortage,
that peat cutting should be encouraged to the greatest
possible extent, it being probable that it would be impos-
sible shortly to send coal to peat districts. The use of
timber as fuel was also advocated, and merchants were
advised to lay in stocks of peat and timber. Coal is
70s. a ton in Youghal.

Belfast.

Very few coal vessels have arrived at this port for the
past week, but fortunately there is less demand for house-
hold coal owing to fine weather. Prices are unaltered, as
follow :—Best English coal, 51s. per ton; English nuts,
50s.; English kitchen coal, 50s.; best English slack, 47s.;
Scotch house coal, 45s.; standard coal, 44s. per ton net.
From April 14 to May 4, the total number of coal-laden
vessels entering the harbour was 218. Dungannon Rural
District Council, having drawn the attention of the Coal
Control Committee to the difficulty of fixing a uniform
price for coal in country districts owing to the cost of
cartage, received a reply stating that the price should
be fixed as at the railway station or depot, and that a
separate scale should be arranged for the cartage.

To cope with possible lack of coal during the winter
and the spring months, large quantities of peat are being
cut in the bogs in the Midlands and West of Ireland.

President Wilson, at a session of the United States War
Council, decided that all consumers of coal, whether rail-
roads, large manufacturing interests, or householders, will
fare equally in the price they are to pay for coal during
the rest of the war.

SOME RECENT DECISIONS UNDER THE
WORKMEN'S COMPENSATION ACT.

[ Specially Contributed . ]

The Connection between an Accident and Incapacity.

In a claim for compensation the decision may depend
on the answer to the question of the extent to which
total or partial incapacity for work is the outcome of the
accident. The question was raised in an interesting way
in the case of Saddington v. Inslip Iron Company Limited,
which has recently been reported in full (118 L.T.Rep.
751). The workman, a furnace labourer at the company’s
iron ore works, suffered in February, 1917, from chapped
hands. On a certain date he was forking and screening
calcined iron ore, using a fork and a shovel. He forked
it over and took the lumps out, afterwards screening the
material by throwing it up against an upright screen.
Late in the evening of the day referred to, the workman’s
hand began to bleed a little from a crack at the base of
the left thumb, the crack having already been there for
two or three days. While off work for supper, the wound
was painful and a fellow workman assisted to bind it
up. The man continued working during the night until
about 4 a.m., but did not appear next day, though he
worked on the three nights following, his hand being
kept tied up. He then saw a medical man, and afterwards
told a member of the staff that he had blood poisoning,
after which he was off work for about a week. The
evidence of this medical man was to the effect that during
the period in question he attended the workman for
septic poisoning, and that when there was a crack in
the skin, such poisoning would be set up by calcined
dust. • In cross-examination he admitted that if the work-
man’s hand was wrapped up when bleeding first occurred,
and kept wrapped up, while the man was at work, in
a properly dressed bandage, but not at other times, he
would conclude that sepsis occurred when the dressing was
off; that a handkerchief would not be a proper dressing ;
that for a proper dressing the handkerchief would require
to be aseptic, which he did not consider a workman’s
handkerchief to be; and that a handkerchief might be
the cause of the septic poisoning.

The county court judge found that the frost crack
shown to him in court had been caused by the man
working in severe wintry weather, but that he had not
been incapacitated thereby; that the cause of the
incapacity was septic poisoning due to microbes entering
the frost crack while the man was at work on the night
in question, but that the evidence did not permit of a
decision as to the means by which the microbes reached
the open wound, and that three means had been suggested
—'the calcined iron dust, the handkerchief, and the dirt
which would in the ordinary course be on the man’s
hand. On these findings it was held that while the
accident arose “ in the course of ” the employment, it
had not been shown that it also arose “out of ” it. On
appeal it was submitted that the finding of fact that the
frost crack was caused by the man working for the com-
pany in wintry weather, entitled him to an award in his
favour; that the finding that incapacity did not result
from the injury directly, but from the wound becoming
subsequently infected, did not prevent th© injury from
being an injury by accident within the meaning of the
Act; that the breaking of the skin over the frost crack
whilst the man was handling the calcined ore was an
accident arising “out of” the employment; that it was
wrong to hold that the workman was not entitled to an
award because the evidence did not show whether the
microbes producing the infection came from the calcined
ore or from the handkerchief which the man wrapped
round his hand while at work; that the precise source
of the infection was immaterial; and that, in any case,
the finding that the infection occurred during the employ-
ment, and the doctor’s uncontradicted evidence that
calcined dust sets up septic poisoning where there is a
crack in the hand, implied a natural and irresistible
inference that the infection was due to the cause and
arose “out of” the employment.

In the Court of Appeal (Lord Justice Swinfen Eady,
Lord Justice Warrington, and Lord Justice Scrutton) the
decision of the county court judge was reversed and an
award was made in favour of the workman. Lord Justice
Swinfen Eady considered that it was not material to
determine the exact origin of the microbes that entered
the man’s hand. It was sufficient to say that the con-
ditions that were proved were such as to lead to the
inference that the hand was poisoned during the time
when the judge found that it was, and poisoned by the
entrance of the microbes during that time, the result being
that the applicant’s incapacity for work, his poisoned hand,
was the consequence of the injury from the crack opening
and becoming poisoned. His lordship was satisfied that
the county court judge’s findings of fact did establish
that the accident arose “out of” the employment, and
that being so, it was not material to allocate the precise
source from which the microbes started on their journey
and ultimately reached the man’s hand and poisoned it.
Lord Justice Warrington was of opinion that there was
clearly sufficient evidence to justify the two findings of
the county court judge, namely, that while the workman
was at work, the previously existing crack in his hand
became an open wound, the change being occasioned by
the work he was doing, and that the incapacity for work
resulted in the germs getting into the open wound. His
lordship further thought that the first finding meant that
the open wound was a “ personal injury caused by acci-
dent arising out of, and in the course of, the employment,”
but that on those findings the county court judge had
misdirected himself in the concluding part of his
judgment, as he seemed to* have thought that it was
incumbent on the workman to prove the exact origin of
the microbes and the route by which they were enabled
to enter the open wound, which afforded an opportunity
for infection. In his lordship’s opinion that was contrary
to two decisions of that court that appeared to him
to be directly in point :— Dunham v. Clare ([1902] 2 K.B.
292 ; 86 L.T.Rep. 751), and Brown v. George Kent Limited
(6 B.W.C.C. 745), and also to a third, Bower v. Meggitt
(10 B.W.C.C. 146), which was specially directed to the
question of the party on whom the onus rested in such
a case. Lord Justice Scrutton summed up the decision
of the court by saying that it is not necessary for a’
workman to establish that his total or partial incapacity
for work has resulted from the injury, in the sense that
it was the natural and probable consequence of the injury ;
it is enough that the incapacity resulted from the injury,
although it was not the sole and unassisted consequence,
for if the injury has to some extent caused the incapacity
it is immaterial that some other cause has supervened
and increased that incapacity.