April 27, 1917.

THE COLLIERY GUARDIAN.

819

sible; the other known as the generator, which is
practically a boiler, heated by steam, in which the
ammonia is driven off. The capacity for absorbing
ammonia gas is highest when the temperature of the
water is lowest; so that the temperature of the
absorber into which the gas passes from the evaporator
is maintained as low as possible, whilst heat is applied
to the generator so as to drive off the gas that is held
in the water. Both absorber and generator contain a
certain amount of water, and there is a continual
exchange going on between them, the liquor from the
absorber being pumped over to the generator as soon
as it acquires a certain strength, and the weak liquor
from the generator being constantly pumped back to
the absorber.

Auxiliary apparatus are required to free the gas
delivered from the generator from the accompanying
water and steam derived from the water in the
generator. The action of the generator is, however,
practically the same as that of the steam boiler: as the
ammonia -gas is driven off, the pressure in the gas
space of the generator rises, thus producing the pres-
sure necessary to force the gas into the condenser and
to raise its temperature.

In the compression system there is a complete cir-
cuit— very similar in many respects to an electric
circuit—consisting of the evaporating coils, the com-
pressor, the condenser, the connecting pipes, and
usually a receiver for the liquid formed in the con-
denser. When the plant is working, the refrigerant
is continually circulating through the system; some of
it is constantly being expanded in the evaporating
coils, some of it is being continually compressed in the
compressor, and some of it is being converted into
liquid in the condenser. The rate of flow is controlled
by an expansion valve between the receiver (or the
condenser where no receiver is used) and the evapor-
ator. The expansion valve is a very accurately con-
structed piece of mechanism, and is so arranged that
a very slight movement either way suffices to increase
or decrease the flow of liquid to the evaporator. The
compressor is sometimes single acting, the gas enter-
ing by a valve at one end of the compressor cylinder
on the suction stroke, and being forced out to the
condenser through another valve at the same end of
the cylinder on the return stroke; and sometimes
double acting, each stroke being a suction and a com-
pression stroke. The compressor is also, particularly
in modern plant, sometimes compounded, the pressure
being raised to a certain figure in the first cylinder,
and then in the second cylinder to the pressure
required for delivery to the condenser. The import-
ance of -the temperature of the cooling water will be
understood .from the following : With cooling water at
55 degs. Fahr, the pressure to which ammonia gas has
to be raised before delivery to the condenser is only a
little over 100 lb. per sq. in.	; with	cooling water	at

60 degs. Fahr, the pressure	of	the	gas is raised	to

115 lb. per sq. in.; and the pressure goes on
increasing till, with the water	at a temperature	of

95 degs. Fahr., the pressure	in	the	condenser has	to

be 2181b. per sq. in. The importance of this will be
appreciated by those who have had to deal with air
compressing plant: the increased pressure means more
work for the engine or motor driving the compressor.
At the other end of the scale, the lower the tempera-
ture to which the gas is expanded in the evaporator,
the greater is the amount of work required to be per-
formed by the compressor to create the necessary
pressure required for the condenser. *

The Nomenclature of Refrigeration.

Refrigeration engineering has produced a nomen-
clature of its own, the principal term used being “ the
ton of refrigeration.” By this is meant the cooling
effect produced by the melting of a ton of ice, at the
freezing point of water (32 degs. Fahr.), in 24 hours.
It is a purely hypothetical figure, as ice is never at
the freezing point of water, stable ice being always at
a temperature at least 15 degs. Fahr, below that point;
but the hypothetical figure answers for calculation,
very much as the horse power does in ordinary engi-
neering work. Like the horse power also with steam
boilers and sometimes with steam engines, the ton of
refrigeration is apt to have a somewhat varied value.
Machines are made to give one ton, two tons, or more
of refrigeration, and to give | ton, J ton, down to
about | ton; and by these figures is meant that the
plant so described will abstract heat from any sub-
stance or any area at the rate per minute or per hour
indicated by the figures in question. It will be
evident, from what has been stated above, that the
work done by any refrigerating plant, apart from the
heat abstracted by the evaporator, depends upon the
temperature of the cooling water ; and so more or less
of a variable has been introduced. In America
attempts are being made to standardise machines; and
in any case where a machine is bought or sold the
temperature of the cooling water at which the given
amount of refrigeration will be accomplished should
be furnished, the buyer being then able to make his
own allowances if he is obliged to use water of a higher
temperature. In addition to this, there is a difference
between what is understood in America and in this
country by the “ton of refrigeration.” In America
the ton is 2,0001b., and as the latent heat that has to
be abstracted from water when ice is formed, or that
ice at 32 degs. Fahr, will absorb when forming water
at the same temperature, is 142 British thermal units
per pound, the American ton of refrigeration means
the abstraction of 284,000 British thermal units in 24
hours, 11,833 per hour, or approximately 200 per
minute. The British ton, on the other hand, is
2,240 lb., so that.the British ton of refrigeration means
the abstraction of 381,080 British thermal units in 24
hours, or approximately 220 per minute. No serious

inconvenience, however, arises from the discrepancy
between the American and British figures.

How the Cooling is Effected.

There are three methods by which the abstraction of
the heat from areas or substances is carried out, viz. :
by what is called direct expansion, by the aid of cold
brine, and by cold air. In the direct expansion
method, the expansion coils are placed in the area to
be cooled, say, in a cold store where meat, etc., is to
be hung. This method, though most efficient, is not
much employed, partly because the effect of a small
leak of ammonia would be very serious upon any pro-
duce held in the store, and partly because the tempera-
ture in the store cannot be so well controlled as by the
other methods. In brine cooling, the evaporator is in
the form of a coil of pipes placed in a tank filled with
brine, pipes connected with the brine tank being fixed
in the cold store or wherever the cooling is to be carried
on, and the brine kept circulating through the tank
and pipes. The cold brine in the pipes abstracts heat
from the cold store, and the gas in the evaporating
coils abstracts that heat from the brine, and delivers
it, after the gas has been compressed, to the cooling
water of the condenser. This is the method employed
in the steamers engaged in the meat transport trade
between America and the United Kingdom. It is
important that the temperature of the chilled meat
should not fall below a certain figure; and by the aid
of thermometers in the return brine pipes, and by
means of valves, the flow of brine in each portion of
the hold where the chilled meat is carried is easily
controlled. This method is also employed, as described
below, for freezing the ground in connection with
shaft sinking; and it was likewise used in the earlier
installations for drying air for the blast furnace.

The reason for employing brine is that a lower tem-
perature can be carried and distributed than by water,
because the freezing point of brine is lower than that
of water. , The presence of any dissolved substance in
water lowers the freezing temperature in direct ratio
to the percentage of substance so dissolved. Calcium
chloride is the substance most commonly employed,
though the firms who carried out most of the sinking
operations in this country used magnesium chloride.
Adding 1 lb. of calcium chloride to a gallon of water
lowers the freezing point to 22 degs. Fahr. ; adding
| lb. lowers it to 27| degs. Fahr.; adding lb. lowers
it to 14*8 degs. Fahr. Care has to be taken not to
employ too strong a solution, as that leads to trouble
from the deposition of the salt upon the inside of the
pipes, and lowers the efficiency of the apparatus. In
air cooling systems, the air that is to circulate through
the cold store is either passed over a grid of pipes, in
which carbonic acid is circulating, or over a grid of
pipes through which cold brine is circulating, or,
again, over a battery of galvanised iron plates over
which cold brine is trickling. Cooling the air also
dries it, the moisture being deposited upon the grids
of pipes where these are used, or in the brine itself
where a battery of plates is employed. This is due to
the fact that the capacity of air for carrying water
vapour varies with its temperature, increasing very
rapidly as the temperature rises, and decreasing very
rapidly as -the temperature falls. Cold air is now
being employed for increasing the output of generators
in electrical generating stations, the air being cooled
either by passing it over cold water or by some similar
arrangement.

The Use of Refrigeration for Shaft Sinking.

Shaft sinking is, so far, the only operation in con-
nection with mining where refrigeration has been
employed, but it has been suggested for cooling the
air in deep mines. This latter problem is a difficult
one, and will probably be expensive, because many
deep mines—particularly those where the atmosphere
is oppressive—are also humid, and provision will have
to be made in the refrigerating plant not only for
cooling the air, but also for condensing the moisture
that will be deposited from the air immediately it
becomes cool.

Shaft sinking refrigeration plant has been employed
with considerable success in Germany and France, and
to a smaller extent in the United Kingdom, where the
sinking has to pass through water-bearing strata. A
ring of boreholes is put down so as to form a cylinder
of frozen ground, of sufficient area to allow of
the sinking operation being carried on inside it.
The boreholes are sunk to a depth a little below the
water-bearing strata, and in each borehole is placed a
pair of concentric tubes. The bottom of the outer tube
is closed, that of the inner one being left open, and
cold brine is kept circulating through the two tubes,
down the inner tube, and up the outer one. The cold
brine abstracts heat from the surrounding strata, and
a cylinder of frozen ground is formed round each tube,
these cylinders uniting to form one large cylinder
enclosing the sinking pit. The concentric tubes are
connected above ground to ring mains connected to a
brine tank, which, as explained above, contains the
evaporating coils forming part of an ammonia com-
pression refrigeration system. Valves are placed at
the top of each pair of tubes, so that any one can be
disconnected in case of accident. Though several
sinkings have been carried out by this process, great
trouble has always been experienced in getting the
boreholes into line, and difficulties often arise while
the sinking is going on, owing to the breaking of
joints between successive lengths of tubes.

The late Mr. R. B. Thomas, managing director of
Richard Thomas and Comoany Limited, steel and tin-plate
manufacturers, South Wales, left estate valued at
£447,588.

Notes from the Coal Fields.

[Local Correspondence.]

South Wales and Monmouthshire.

Monmouthshire, Rescue Station Report—What Colliers are
Earning — South Wales Federation — Patent Fuel
Makers and the Controller—Operation of Limitation
Ifates—Alleged Illegal Expenditure of Miners’ Funds
—Prosecution of Steel Works Owner.

In their seventh annual report, the management com-
mittee of Monmouthshire Collieries’ Rescue Association
state that training operations have been somewhat irre-
gular, and they attribute this to difficult circumstances at
the collieries through the absence of so many officials. As
a result, maintenance practice has not been up to the
average, and to some extent the brigade’s1 standard of
efficiency has been impaired. The number of trained men
has been about the same as during the preceding year—
namely, 350. Two calls were made upon the station
during the year—one. to an underground fire, and the other
to a fire on the surface; and in each case effective service
was rendered. The collieries connected with the associa-
tion had an output of just over 11^ million tons, which is
a decrease of 456,000 tons.

Mr. II. J. Hill, of Cardiff, presided at a conference in
London dealing with the supply of coal to France and
Italy, representatives of the coal trade being present from
all parts of the country. Discussion took place as to the
best method of attaining uniformity of procedure, as far
as possible, at the different ports.

The Board of Trade returns have been utilised in order
to demonstrate that colliers are making large incomes—
an estimate being made that some of the more fortunate
men received between £80 and £100 during the first
quarter of this year, and therefore at the rate of £300 to
£400 per annum. It is, however, quite impracticable to
reach any definite conclusion. Although the estimate may
be well founded, nothing but income tax return would
justify definite conclusion. Certainly the wage rate is
high; and where the men have had the good fortune to
secure anything like regularity of work in a good seam,
they can make a large income; but this applies only to a
part of the coal field, for the anthracite mines, in parti-
cular, have been badly hit by restriction of output due to
shortage of tonnage.

The South Wales miners stood alone at the national
conference held in London last week on the subject- of
“ combing-out ” men for military service. The delegates
at the conference discussed the Coal Controller’s scheme
designed to obtain 20,000 more men, but South Wales
alone made opposition to further withdrawals, their propo-
sition being that no action should be taken to assist the
Government. The resolution was submitted that the
Federation should take part with the Government in con-
sidering the best method of getting the men required, and
this was carried by 111 votes to 22 — only South Wales
voting to the contrary. A demand in the course of the
meeting was that 10,000 miners were required to fell
timber for pit props, etc.

The delegates from South Wales were : Messrs. James
Winstone, G. Barker, V. Hartshorn, W. Abraham
(“ Mabon ”), M.P., T. Richards, M.P. (secretary), Evan
Thomas (assistant secretary), Hubert Jenkins (Caerphilly),
Evan Davies (Ebbw Vale), O. Harris (Tredegar), Enoch
Morrell (Merthyr Vale), and John Williams (Merthyr).

The patent fuel manufacturers of South Wales, at an
interview with the Coal Controller on Monday, pointed
out to him the different conditions operating in respect to
their industry as compared with coal mining. The maxi-
mum price of coal and patent fuel supplied to the Allies
has been limited to 30s., and what the patent fuel makers
requested was that separate consideration should be given
to them (on account of the increased cost of production)
when he was re-considering any scheme dealing with limi-
tation of prices. Emphasis was laid upon the fact that
working costs had greatly increased since the limitation
price of 30s. was fixed. Assurance was given that, in
framing any new scheme, due consideration would be given
to the representations which had been made; and the depu-
tation considered the result of their interview to be satis-
factory.

It is estimated that the action of the Government in
regard to men to be taken from the mines for the Army
will affect at least 80,000 ; but from this total has to be
deducted those who have entered the mines since the war
broke out, and have left the industry since. It is shown
conclusively that there are far more men available than
the Government are as yet calling for, and that should
they act directly against those who had entered the mines
since August 1914, there are ample numbers available. On
the other hand, there is the consideration of the import-
ance of maintaining the output of coal.

Mr. Morgan (secretary of the anthracite collieries) has
drafted a statement showing, for the different collieries in
the district, the number of idle days during February and
March, and this varies- from 45 days at Llwynon Colliery
to only one day at Tirydail. Several are above 30 days,
and as many more above 20 days. The executive council
of the Miners’ Federation, when approached to give out-
of-work pay from Federation funds, decided to make a
grant only to men who had lost 12 days in a month, or six
consecutive turns; but this has occasioned adverse
criticism, especially as in several cases the colliers have
lost 10 or 11 days.

In the course of a speech at Merthyr on Sunday, Mr.
J. Williams (miners’ agent) said that 200,000 days’ work
had been lost in South Wales during February by men
unable to obtain employment. He urged that the Federa-
tion should make a decisive pronouncement with regard to
the war, whether right or wrong. He could not under-
stand men of military age and physical fitness who had
obtained exemption as trade union leaders getting up at a
conference in London, and making it easy for others to
go to the war except themselves. The meeting passed a
resolution calling upon the miners’ executive to summon a
conference in order that a policy might be formulated, it
being. deemed advisable to exert pressure for ending the
war.

At the Beille Glyn Colliery, a second shaft has been sunk,
striking the 2 ft. 9 in. seam ; and when developments are
accomplished, it is expected that employment will be given
for an additional 300 men.

An extraordinary state of things prevails in the
Rhondda : nothing less than a coal famine for ordinary
consumers. There is general complaint in this colliery