1188

THE COLLIERY GUARDIAN.

June 23, 1916.

erected on the bottom of the shaft, and connected with
the freezing plant at the surface by two pipe lines. The
result was not as anticipated. The gravel bed between
the two concrete blocks absorbed mud during the boring,
so that the injected cement did not set properly.
Furthermore, the coils in the concrete fissured in
freezing, so that the method of lengthening the tubes to
the surface had to be employed. Similar measures have
been adopted in the Gampine (Belgium), but precautions
have been taken so that probably only a very small
quantity, of guide and freezing tubes will be necessary.

Measuring Deviation of Boreholes.

It .is important that the deviations of boreholes for
shaft sinking by the freezing process, and also by the
cementing process, should be ascertained. The amount
of deviation may be obtained either by (a) the surface
of a liquid contained in a box, (5) a plumb line or
pendulum placing itself in a vertical line, or (c) a
pendulum moving round the vertical line; while the
bearing may be determined either by (a) a special
suspension guide, (b) a compass, or (c) a gyroscope.

The Plumb Line.—The plumb line method is exceed-
ingly simple, and it has the great advantage that all its
measurements are related to the suspension point in the
centre of the guide tube, therefore each one is entirely
independent of the other. The readings are easy down
to a depth of 330 ft., but then they become more
difficult, because the difference of the similar triangles
to be compared become greater and greater, and the
smallest error is multiplied by large coefficients. Thick-
ness and bends of the wire are also important factors,
and the likelihood of fhe wire touching the side of the
borehole continually increases with the depth. The
plotting of the deviation must be made with the greatest
care. In spite of this, very good results have been
obtained down to a depth of 660 ft., and it is acknow-
ledged that this system of plumbing has greatly
contributed to the success which has attended the
adoption of the freezing process.

Tele clino graph.—The complete apparatus is made up
of two parts : a transmitter, which is inserted in the
borehole, and a receiver, which remains at the surface.
The transmitter consists of a copper tube fitted inside
the steel watertight tube, which adapts itself to the
direction of the inclination of the borehole. This box
is suspended by a system of rods, the joints of which
are made so that the apparatus always points in the
same direction with regard to the north point, at what-
ever level it is. The inside is suspended by a Cardan
joint, which is a conical pendulum receiving a circular,
or, rather, elliptic, oscillatory movement from the
mechanism. At its lower end the pendulum carries a
style running with a slight contact on a spherical hollow
cap. The receiver contains a mobile organ with a
tracing pen revolving round a vertical axis, the move-
ment synchronising as much ais possible with that of the
conical pendulum.

Like all apparatus with mechanism inserted in the
borehole the teleclinograph gives only the inclination at
a fixed point. Therefore it needs the total result of the
measures in order to make the plotting or calculate the
position at a given depth. Also such an operation can
only really give practical results if a very large number
of measurements can be made in a short time. That is
possible with the teleclinograph; it allows observations
to be made at intervals of 16 ft., but it has been found
that distances of 33 ft. were sufficient. With these
lengths it is possible to make a double series of measure-
ments in a depth of 1,850 ft. in less than three hours,
once going down and once returning after having turned
the box through 180 degs. This, however, is only
possible because the results are directly registered, and
it is not necessary to withdraw and open the box after
each measurement is taken.

LAW INTELLIGENCE.

SUPREME COURT OF JUDICATURE.

COURT OF APPEAL.—June 21.

Before Lords Justices Swinfen Eady, Phillimore, and
Bankes.

Rating of Collieries.

D. Davis and Sons Limited v. The Assessment Committee
of Pontypridd Union.—Judgment was-given unanimously in
favour of the respondents, Messrs. D. Davis and Sons
Limited, colliery proprietors, in the appeal of the Pontypridd
Union Assessment Committee against the decision of the
Divisional Court, which had reversed the decision of the
Glamorgan Quarter Sessions. At the Quarter Sessions, the
Cambrian Collieries and the Glamorgan Coal Company were
also associated with Messrs. D. Davis and Sons Limited as
apoellants. It was then arranged to hear Messrs. D. Davis
and Sons’ appeal as governing all the cases. The case arose
out of an agreement made 'between the Assessment Committee
of the Pontypridd Union and a number of the colliery owners
within the Pontypridd area in 1902, when the assessments of
the collieries were largely increased, but were reduced as the
result of successful appeals undertaken upon the advice of
Messrs. Humphreys-Davies and Company, rating surveyors,
London. Following the appeals, and with a view to avoiding
litigation in the future, the agreement referred to was con-
cluded by which the collieries were to be assessed on a
tonnage basis, subject to notice to terminate.

In 1907 a new power station was erected to replace a
number of smaller stations, and in the supplemental valua-
tion list for the spring rate of 1913 an additional assessment
was. placed upon the new station. This assessment was the
subject of an objection, and, failing to obtain relief, Messrs.
D. Davis and.Sons carried an appeal to the Quarter Sessions.
It. was there contended, on behalf of the Assessment Com-
mittee, that the court could not take cognisance of the agree-
ment, and that the overseers were entitled to rate the elec-
trical generating station as a separate hereditament. The
Quarter Sessions accepted this contention, and the appeal was
dismissed. The decision of the Quarter Sessions was, how-
ever, reversed by the Divisional Court, and the decision of
that court has now been upheld by the Appeal Court.

THE BETTiNGTON BOILER*

This type of boiler, which has been installed at the
Johannesburg Municipal Electric Power Station, is
essentially a coal dust fired boiler, and is of relatively
new design. The chief pioneering and experimental
work was carried out on the Witwatersrand by the late
Lieut. Claude Bettington and Mr. Robeson. The
particulars of the boiler are as follow :—Evaporative
capacity, 34,0001b. per hour; heating surface, 240 tubes,
3{-in. diameter, 22 ft. long, 4,480 sq. ft.; heating surface
of boiler shell, 460 sq. ft.; heating surface of superheater
tubes, 1,200 sq. ft.; heating surface, 75 economiser tubes,
3| in. diameter, 22 ft. long, 1,400 sq. ft.; heating surface,
188 air-heater tubes, 3|in. diameter,, 10 ft. 10 in. long,
1,730 sq.ft.

The illustration shows the arrangement of the boiler.
It consists briefly of solid drawn steel vertical tubes
connected at the top and bottom to mild steel annular
headers. The top header is fitted with doors for drawing
out the tubes whenever necessary. The steam drum is
fitted into the annular space of the top header, large
holes being made in the periphery of the steam drum to
form one common water and steam space at the top of
the boiler. The top and bottom headers, together with
the vertical tubes, form a circular structure like a huge
cage. The interior part of this structure forms the com-
bustion chamber, where the fuel is burned. The coal is
placed in the coal bunker, fed into the coal hopper, and
falls by gravity on to a worm gear, which forces the coal
into a combined pulveriser and blower. This latter
arrangement is simply an ordinary centrifugal fan with
heavy blade or beater tips and with a
constricted space between the ends of
the beaters and the casing. The
boiler under review is fitted with two
sets of combination blower pul-

verisers, each directly driven by
100 horse-power motors at approxi-
mately 1,400 r.p.m. Each pulveriser
is capable of giving the full rated
output of the boiler. In. this way
the coal is driven outwards by centri-
fugal force, and is crushed to fine dust
and blown into the dust chamber.
The heavy particles fall back again
into the pulveriser to be further
crushed to fine dust. This is carried
upwards to the air and fuel pipe,
which terminates in a large tuyere,
and the coal dust when ignited burns
like a large Bunsen burner. The
ignited coal dust forms a mushroom-
shaped flame within the closed
ring of vertical tubes which form
part of the steam-producing plant.
The flame strikes the bottom of the
steam drum, is deflected downwards,
and passes over the interior row of
lubes, which are protected from the
high temperature of the combustion
chamber by specially shaped fire-
bricks. The hot gases are then
deflected upwards and pass over the
outer rows of vertical water tubes
and the superheater tubes, and finallv
round the economiser tubes through
which the boiler feed passes before it
gets to the boiler. There is also
another set of tubes through which
the gases pass before entering the
chimney and passing to the atmo-
sphere. This latter set of tubes
forms a separate air heater, and is
connected to the pulveriser blower,
which draws the air around the hot
tubes, thus heating the air before
it passes into the boiler and
enables the pulveriser to deal with
fairly wet coal. The superheater tubes

are connected to the upper part of the steam space
of the top header by means of a steel expansion pipe, and
the superheated steam is led away to the mains in the
usual way. The firing of the boiler when cold is done at
the municipal station by inserting a 2-in. gas pipe into a
4-m. air pipe to form a large Bunsen burner, the whole
being placed inside the tuyere, and the boiler is started
up instantly by simply lighting up the large gas jet.

The Bettington boiler was installed in 1911, and a
thermal efficiency of 85 per cent, was guaranteed. The
boiler, as depicted in the figure, had to be somewhat
modified. At first it was fitted- with a parallel chimney
60 ft. high and 4 ft. 6 in. diameter. It was expected that
the pulveriser, which acts as a fan and produces a
pressure of 1 in. to 1J in. in the combustion chamber,
would be sufficient to force the hot gases around the
boiler tubes, the economiser and air heater tubes, and
thence up the chimney. In practice, however, the gases
were somewhat choked and cooled to such an extent that
additional draught had to be provided to get the full
capacity out of the boiler. It wras impossible to1 modify
the air pressure at the pulveriser, as it interfered with the
combustion of the coal dust. The economiser and air
heater were considerably reduced, and a more direct path
for the gases to the chimney was provided, by raisin»
the air heater about 26 ft. In addition, the boiler was
fitted with a Schwabach indirect induced draught plant,
and the height of the chimney in the new anrano-ement
is 86 ft., the draught at the bottom of which is about
Jin.. In this way the rated capacity of the boiler was
obtained, but its efficiency was somewhat lowered; the
figures below are those obtained from the modified
boiler. No doubt in the future design of this boiler its
efficiency can be somewhat improved by a proper relation
between, the pulveriser pressure, the boiler tubes, and the

* Journal of the South African Institution of Engineers.

magnitude and arrangement of the economiser and air
heater system without the necessity of an additional
mechanical draught system at the base of the chimney.

After these alterations and certain adjustments at the
pulverisers were made, the boiler, whilst not attaining
the high efficiency of 85 per cent, as guaranteed, was
considered thoroughly reliable for the purposes for which
it is used at the municipal power station. Practice
shows that the water tubes are practically self-cleaning.
The inner row of water tubes do not appear to show any
unusual evil effects by being close to the combustion
chamber. During a period of four years very few tubes
have been replaced. The boiler can be, and is, usually
put on the steam mains from cold in about twenty
minutes to half an hour from lighting it up by gas. The
boiler is usually run to take the evening peak load, but
has been run regularly day and night on occasions for a
period of over a week, during which time it is necessary
to rake out the pebbles of slag every 12 hours, and there
was no particular trouble experienced through slag
depositing on the brick lining. This boiler has been of
great service when part of the other boiler plant has been
suddenly put out of action. Its ability to get up steam
quickly is regularly taken advantage of, especially
during the rainy season, when sudden large increases of
load arise in a very short time. As it is fitted with two
pulverisers, each.of which can give the full rated output,
its overload capacity has ofttimes proved exceptionally
useful. Needless to say, the boiler was paid for and
taken over, and it forms a valuable portion of the boiler
plant, working on conditions of large and sudden power
demands.

ECONOMISER

Results of Tests.

Duration of test, 9*8 hours; gauge pressure, 173-7lb.
per sq. in.; feed temperature, 65-5 degs. Fahr.; steam
temperature, 510’3 degs. Fahr.; water evaporated per
hour, 31,5611b.; coal consumed per hour (no allowance
made for carbon value of ashes), 4,4771b.; lbs. of water
evaporated per lb. coal (as fired), 7’050 lb.; gross
calorific value of coal as received, 11’50; net calorific
value of coal as received, 11-10; heat transmitted to feed
by boiler per lib. dry coal, 1,240 British thermal units;
evaporative equivalent from and at 212 degs. Fahr, (as
fired), 9’049; evaporative equivalent from and at
212 degs. Fahr, (dry), 9’464; efficiency on gross calorific
value, 78’6; percentage auxiliary power, 3-8; net
efficiency on gross calorific value, 75’6; efficiency on net
calorific value, 81’4; net efficiency on net calorific value,
78-3.

The late Mr. G. Greatorex, colliery cashier, Lay ton-
avenue, Mansfield, left £5,063.

The state of the late Mr. R. R. Penman, boiler maker
and engineer, Glasgow, has been valued at £43,514.

New proposals relating to petrol and income tax are
embodied in the Finance Bill. In the case of petrol official
permits will be tissued for the purchase of limited supplies.
Commercial cars and doctors’ cars will pay half rates.
Regarding income tax, the limit within which the allowance
for children may be claimed is raised from £500 to £700.
The difficulty of collection at the source is to be mitigated.
A concession is made to soldiers and sailors by the reduced
rate of income tax, now limited to incomes up to £300 being
extended to incomes up to £1,500. Thus Is. 3d. will be
paid on incomes between £300 and £500; Is. 9d. between
£500 and £1,000; and 2s. 3d. between £1,000 and £1,500.