1032

THE COLLIERY GUARDIAN.

November 19, 1915.

CURRENT SCIENCE

Conveyor Belt Calculating Chart.

In a paper read before the American Institute of
Mining Engineers, J. D. Mooney and D. L. Darnell
give a convenient chart as a, means of quickly deter-
mining the correct number of plies of conveyor belts
operating under specific conditions. The calculations
are based on the average safe strength (factor of safety,
15) of the various standard rubber conveyor belts. The
calculations assume maximum loading conditions—that
is, the belt is considered as carrying the greatest load
that it will handle without spillage at ordinary belt

IIX)_

9	8	7

NUM8ER OF PLIES

speeds. The chart is a graphical representation of the
formula:—

p = kg W (L + 10 H).

Where p = the correct number of plies; k = a
constant, depending on the type of drive; g = the
weight in pounds per cubic foot of material handled;
W = the width of the belt in inches; L = the length
of the belt in feet (approximately twice the centre
distance); H = the difference in elevation between
the head and tail pulleys, in feet. For a simple drive,
with a bare pulley, k =	; for a simple drive,

2o0,000

with a rubber-lagged pulley, k =	; for a tandem

OVVjOOO

drive, with bare pulleys, k =	for a tandem

r J 375,000

drive, with rubber-lagged pulleys, k = -7=^1^ ; the
chart is drawn for a simple drive, with a bare pulley
(k = 25o"()0q) ’ ^ere^ore, the number of plies
obtained from the chart should be multiplied by the
factor 0'83 or for simple, lagged drive ; the factor 0’67
or f for tandem, bare; and the factor 0’55 or for
tandem, lagged.

The formula p = k g W (L 10 H) has been developed
mathematically from the following formulae, which
have been found to work very satisfactorily in average
good practice:—

U = O’O8W2S0

5,000

■rrp_ Z0’02Z . 0‘01H\tt

HP-(lkF + “To~JU

rp _ C X HP X 100

S

_ T

P 24 W

Where U = capacity in tons per hour; W = width of
belt in inches; S = belt speed in feet per minute;
g = weight per cubic foot of material handled; HP =
horse-power developed in driving conveyor belt; I =
length of the conveyor, in feet (approximately | L);
H = the difference in elevation between the head and
tail pulleys, in feet; T = the total tension in the belt,
in pounds; p = correct number of plies; C = the
constant of the drive. For a simple drive, bare pulley,
C = 600 ; for a simple drive, rubber-lagged pulley,
C — 500; for a tandem drive, bare pulleys, C = 400 ;
for a tandem drive, rubber-lagged pulleys, 0 = 330.
The length factor, / = (L 4 10 H), represented on the
chart by the lines 500, 600, 700, etc., is a developed
factor equal to the sum of the length of the belt and
10 times the difference in elevation between the head
and tail pulleys.

To find the correct number of plies for a conveyor
belt, knowing the width, the length, the difference in
elevation between the head and tail ends, and the kind
of material to be handled:—Start from the width given
at the top of the chart and move down until this line
intersects the line corresponding to the proper length
factor; then move either right or left until the line
corresponding to the given material is met, then move
down again to the scale of plies, where the next largest
figure will give the correct number of plies. For
example: To find the correct number of plies for a
conveyor belt 36 in. wide and 300 ft. long, with 20 ft.
difference in elevation, handling sand and gravel,
follow the line from the 36-in. width downward until it
intersects the 500 length factor line; then follow to the

AND TECHNOLOGY.

right until the sand and gravel line is intersected ; then
down to the ply scale, where the ply will be found to
be 7.

Production of Ammonia by the Gasification of Coke.

Salmang (Dissertation, Aachen Technical HighSchool)
finds that the combined hydrogen in coke does not go to
form ammonia when that fuel is gasified, it being
necessary, for this purpose, to make use of steam, which
at the same time protects the ammonia from decom-
position at high temperature. With steam alone (water-
gas process), 36 yer cent, of the nitrogen in coke can be
converted into ammonia during gasification; but if air
be admitted at the same time (mixed gas process), and
the operation be conducted at 900 degs. Cent., the
amount converted attains 59 per cent. In both systems
the addition of lime (5 per cent, of chalk) increases the
yield of ammonia considerably—up to 96 per cent, in
the mixed process—whilst ferric oxide has a similar, but
less effective influence, upto 70per cent, of the nitrogen
being converted. On the other hand, the presence of
an excess of air, in association with steam, at 900 degs.
Cent., greatly lessens the effect, only 8 per cent, of the
nitrogen being converted, or 17 per cent, if lime be
present. Peat coke gives a smaller yield of ammonia
than ordinary coke; bu^ here, also, lime is beneficial
In all cases where coke is gasified at 900 degs. Cent.,
the gasification of the nitrogen progresses in the same
degree as that of the carbon, a circumstance indicating
that the nitrogen is combined with the whole of the
carbon and cannot be gasified without the latter at the
temperature in question.

A Steam-Actuated Shaft Gate.

The shaft gate shown in the accompanying drawings,
for which we are indebted to Coal Age, has been
designed by Thomas H. Tudor and Uriah M. Lenhard,
two officials of the Pittsburg-Westmoreland Coal
Company. This gate is so arranged that the cage on
coming to the landing throws the lever of the controlling
valve, admitting steam or compressed air to the cylinder.
This forces the piston down, lifting the gate through the
medium of a cable passed over suitable guide pulleys.
Suitable springs placed in the cylinder above and below
the piston prevent it from striking the lower head when
the gate is being hoisted, or the upper head when the
steam is exhausted.

When the cage is raised or lowered from its normal
position at the landing, the lever of the control valve is
thrown in an opposite direction and the steam or air

'Lubricator

Fig. 1.—Valve Mechanism Controlling Gate.

i

I
s>

Fig. 2.—Arrangement of Cylinder
and Gate.

exhausts from the cylinder, allowing the gate to return
to its normal position.

The time required to raise the gate or to allow it to
settle to its normal position may be controlled by the
action of two valves, one in the steam supply and the
other in the exhaust pipe. These are adjusted until the
desired time of raising and lowering has been secured,
when they are allowed to remain in this position and by
their throttling effect govern the speed of travel of the
piston in the cylinder and the gate to which the piston
is attached.

The device is so constructed that if the cage is
raised or lowered 12 in. from the landing position the
gate immediately closes. This renders it practically
impossible for an accident to occur at the ground
landing.

Liquid Air as an Explosive.

Prof. Linde appears to have been the first success-
fully to introduce an explosive consisting of ground
charcoal and liquid air. Since then Claude and
d’Arsonval, in France, have further developed these
processes, and finally Kowatsch and Bald us, in Ger-
many, have lately worked it out still more fully, partly
under the pressure of the present demand for an
explosive exclusively of German manufacture.

In order to avoid excessively rapid evaporation of the
liquid air, Kowatsch, who uses a cardboard cartridge,
introduces first a cartridge with dry carbon into the drill
hole separately and without any liquid air, which is put
in only just previous to ignition. The process permits
reducing to a minimum the period of evaporation, and
also increases the factor of safety of operation.

The cardboard cartridge contains a perforated pipe in
which there is a mixture of infusorial earth with oil and
asphaltum or lamp black and paraffin, neither of which
is explosive in itself. This centre pipe contains another
cardboard tube over which a third cardboard tube is set,
serving as an exhaust pipe for the products of evapora-
tion of liquid air. If several drill holes have to be
exploded simultaneously, the electric connections are
made accordingly.

The liquid air which has to be used for each hole is
kept in a precisely determined quantity in a small
bottle, the opening of which is provided with a metal
tube and conical nozzle, connected with the central
tube of the cartridge. To load the cartridge, all that is
necessary is to lift the rear end of the bottle. The
liquid air is raised by the pressure of its own products
of evaporation and gradually passes into the cartridge.
At the instant when the charge is ignited by the electric
spark, the liquid air combines with the charge and
there follows an explosion of exceptional violence.

Among the advantages of this method of explosion is
the fact that, in the first instance, the materials used are
not explosive in themselves, and the exp'osive mixture
is formed only at the very last moment in the borehole
itself. In the second place, should an explosion be
missed, the liquid air will evaporate and the remaining
cartridge is perfectly harmless.

THE GERMAN AND AUSTRIAN COAL
AND IRON TRADES.

We give below further extracts from German
periodicals that have reached us, showing the course of
the coal and iron trades in Germany and Austria :—

The Steel Union and the Thyssen Group.

The report that the Deutsch er Kaiser works, belonging
to the Thyssen group, had given notice to terminate
its membership of the Union, requires some amplifica-
tion, inasmuch as the notice contains a clause that it is
not to come into operation until two months after the
conclusion of the war, and not on March 31 next, as
was originally assumed.

Fuel Shipments from Ruhr Harbours in September.

The total shipments of coal, coke, and briquettes to
Coblenz and places higher up river were 561,282 tons
(587,891 tons, September 1914); to places below Coblenz,
18,274 tons (14,000 tons); to Holland, 139,459 tons
(158,889 tons); to Belgium, 45,738 tons (nil); and to
other destinations, 9,699 tons (10,044 tons). Shipments
from Duisburg-Ruhrort totalled 618,995 tons (611,856
tons); Rheinpreussen, 66,739 tons (47,276 tons);
Schwelgern, 25,173 tons (57,746 ton); and Walsum,
63,544 tons (53,955 tons); a grand total of 774,451 tons
(770,824 tons).

German Wire and Wire Nail Convention.

It has been decided that prices are not to be raised
for deliveries during the current quarter.

German Steel Union.

The deliveries for October are estimated at:—Semi-
manufactured goods, 68,000 tons (67,220 tons in
September); railway superstructural material, 126,000
tons (117,426 tons); and sections, 58,000 tons (62,194
tons); a total of 252,000 tons (246,840 tons), based on
weight of raw steel.

Ruhr Coal Market.

The output in October was lower than in the previous
month, owing to the great scarcity of railway wagons,
and the concurrent unfavourable condition of the Rhine
for traffic; and consequently the situation of the market
was unsatisfactory. The distribution of coke receded
by about 100,000 tons, and, at the same time, the
requirements of the iron industry were smaller, so that
little progress was made in the lightening of coke stocks.
The scarcity of fuel in Berlin has been relieved by large
consignments of coal and coke from the Ruhr.

Coal and Iron Market in Upper Silesia.

The situation of the coal market during October was
satisfactory, in so far that the demand was greater than
the pits could cope with fully, more especially in view
of the diminished output as compared with pre-war
times; but the position was further complicated by the
shortage of railway wagons, which delayed delivery all
through the month, and necessitated stocking. There
is, however, little prospect of a coal famine, since, as
soon as wagons can be obtained again, these stocks will
be available. Meanwhile, consumers have been press-
ing for delivery, especially of gas and coking coal to dis-
tricts formerly supplied by England. The cokeries are
taking unusually large quantities, in order to supply the
heavy demand for coke and by-products. The delivery
of coke has been retarded by the scarcity of wagons, but
sufficient stocks have been available to tide over the
delay.

The iron industry is now amply supplied with ore and
slag, so that the blastfurnaces are able to meet the
increased demand up to the end of the year. Though
these raw materials have advanced considerably in price,
there wrill be no scarcity of pig iron in the near future.
Deliveries of finished goods to neutral countries and
Poland have been restricted in favour of customers in
the home market, export being, moreover, retarded by
the existing prohibitions and by congestion on the lines
of traffic. In commercial iron, business is dull, though
the requirements of wagon builders, railway shops, and
makers of small articles like screws, nuts, horseshoes,