336

THE COLLIERY GUARDIAN.

August 16, 1918.

Rescue Work.

All the rescue stations continued the work of train-
ing brigades and keeping in practice those already
trained.

Treatment of Animals.

Horses were employed at 303 mines, and 361 inspec-
tions were made, 5,524 horses being examined out of a
total of 6,239 employed below ground. The general con-
dition was fairly satisfactory, though in some cases they
were found in rather poor condition, due to inferior
food and the reduction in the quantity of cereal food
stuffs. There were two outbreaks of glanders during
the year.

Supply of Materials.

The difficulty in obtaining adequate supplies of
materials has become more acute. Reinforced con-
crete props are now being used extensively in several
parts of the division, and generally the results have
been satisfactory. The use of timber bars, strengthened
by means of old wire rope, has been adopted at some
of the pits, with excellent results.

Timber Committees.

The problem of providing sufficient pit timber has
at times been fairly acute, but the collieries have all
been kept going. The Birmingham Pitwood Associa-
tion has been formed to serve the northern part of the
division. In the Somerset, Bristol, and Gloucester-
shire area there is a good supply of standing timber
near to the collieries. An association is in process of
formation for that district.

Accidents.

There were 121 fatal accidents causing 124 deaths, as
compared with 131 accidents and 137 deaths in 1916;
a decrease of 10 accidents and 13 deaths. No firedamp
explosion was attended by loss of life, but there were
9 non-fatal explosions, resulting in injury to 11
persons. There were 66 accidents from falls of roof
and sides, with 68 deaths, as against 69 accidents and
74 deaths in the preceding year. Attention is directed
to the question of setting foresets or temporary sup-
ports until there is room for the permanent timber.
Seven accidents, resulting in 8 deaths, occurred in
shafts, an increase of 2 accidents and 3 deaths over
the figures for 1916. There were 30 miscellaneous
accidents, causing an equal number of deaths, as com-
pared with 42 accidents and 43 deaths in 1916. The
practice of horse drivers riding on the chains or walk-
ing between the horse and the tub was responsible for
no less than 3 fatal and 12 non-fatal accidents. On
the surface 18 accidents, causing 18 deaths, occurred,
compared with 15 accidents and 15 deaths in 1916.

Dangerous Occupations.

Eighty-two dangerous occurrences were reported,
including 4 ignitions of firedamp, 1 outburst of gas
which fouled the workings, 6 overwindings, 45 under-
ground fires, 20 breakages of ropes and other parts of
winding gear, 6 inrushes of water. Of the 45 under-
ground fires, 42 were due to spontaneous combustion,
27 of which were in the Staffordshire thick coal. Of
the 20 breakages reported, 6 were breakages of wind-
ing ropes.

Prosecutions.

Proceedings against owners, managers, etc., num-
bered 8, and Convictions were secured in each case.
There were 68 prosecutions against employees, and
convictions were obtained in 66 cases.

COKE AND EXCESS PROFITS DUTY.

After consideration of an application made by Sir
Thomas Ratcliffe-Ellis, as secretary to the Mining
Association of Great Britain, for an increase of the
statutory percentage as respects the business of pro-
ducing in the United Kingdom metallurgical coke
by the high temperature process, with or without the
recovery of by-products, but excluding the manufac-
ture of coke and by-products by manufacturers whose
primary object is the production for sale to the public
of gas, the Board of Referees has ordered that the
statutory percentage as respects the class of trade or
business in question shall be increased—

1.	In the case of any trade or business carried on
or owned by a company or other body corporate to
8 per cent.

2.	In the case of any other trade or business, (a) for
accounting periods ending prior to January 1, 1917,
to 8 per cent, plus 1 per cent.; (b) for accounting
periods ending after December 31, 1916, to 8 per cent,
plus 2 per cent., except that, for the purposes of sub-
section (2) of section 41 of the principal Act, the statu-
tory percentage shall be 8 per cent, plus 1 per cent.,
with the addition, in cases 1 and 2 (b) for accounting
periods ending after December 31, 1916, of 3 per cent,
for the purposes of sub-section (1) of section 41 of, and
paragraph 4 of Part II. of the Fourth Schedule to,
the principal Act.

Coal Controller's Advice to Householders.—The Con-
troller of Coal Mines, when he addresses the recently
elected executive of the Miners’ Federation of Great
Britain at Southport, next Wednesday, will make a full
statement as to the coal position of the country and its
Allies. South Wales is already responding to the Prime
Minister’s appeal, and very satisfactory reports are to
hand from Northumberland, Durham, and some Midland
districts. The Coal Controller makes the following sugges-
tions to householders: Order your coal now, if you can
store it; mix coke with it; consider how many fires you
can do without; cook fewer hot meals; reduce the number
of hot baths; put firebricks in grates where possible ;
never use a gas stove for boiling water if there is a fire
in any room in the house; see that all kettles and sauce-
pans are free from soot; try and do with three-quarters
of the ration allowed; remember that every pound of coal
saved helps to keep our soldiers warm and assists our
French, Italian and American comrades to beat the Huns.
Over 40,000,000 forms for private coal consumers have
already been distributed, and are now available in most
districts of England.

EXAMINATION OF STEAM BOILERS
AT COLLIERIES.

By Edward Ingham, A.M.I.Mech.E.

According to the Coal Mines Act of 1911, every steam
boiler used for generating steam in or about a mine
must, whether separate or one of a range, be examined
thoroughly by a competent person at least once in
every fourteen months. The object of such examina-
tion is, of course, to ascertain whether or not the boiler
is quite safe to continue working at the stipulated
working pressure.

Owing to the great demand for steam at most
collieries, large ranges of boilers are common, and
the question of efficient inspection is a highly im-
portant one, since it not only safeguards the boiler
against explosion, as required by the Act referred to,
but it serves to discover defects in their early stages,
so that a suitable remedy may be applied with little
expense to the owner of the boiler. In the past this
question has been treated too lightly, with the result
that the cost of maintenance and upkeep of the boilers
has been excessive in many instances, whilst explosions
have occurred more frequently than they otherwise
would have done.

Most steam users nowadays have their boilers in-
sured with a recognised boiler insurance company,
whose inspectors are regarded by the Board of Trade
as “ competent ” for the work, and whose inspections
comply in every way with the requirements of the
Act. It is, however, a fact not generally recognised
that the insurance inspections may be supplemented
by examinations made by the firm’s engineer, with
great advantage to the boiler owner, particularly if
the engineer is acquainted with the various defects
from which boilers suffer. Unfortunately, many engi-
neers are not familiar with these defects, and for
this reason the following remarks should prove useful.

For general power purposes at collieries, the Lan-
cashire boiler is undoubtedly the most suitable. It con-
tains large steam and water spaces, and is in conse-
quence well adapted for supplying intermittent and
heavy supplies of steam, as required by winding

\

Fig. 1.

Fig. 2.

engines; it is very accessible for cleaning and inspec-
tion, is economical in fuel, and, when the conditions
of working are satisfactory, seldom requires repairs.
Hence, notwithstanding the rapid advance made by
the water-tube boiler, it is not surprising that the
Lancashire boiler is the one generally adopted at
collieries, and in what follows we shall therefore con-
fine ourselves principally to this type of boiler.

A thorough inspection comprises an internal and an
external examination, the object of the former being
to examine the plates on the water and steam side,
and of the latter to inspect the fire side of the plates.

Internal Examination.

Internal defects comprise corrosion, or wasting of
the plates, grooving and fractures. Internal corrosion
occurs in different forms. A common form, known
as “ pitting,” is illustrated in fig. 1. Small dish-shaped
holes are eaten into the metal to varying depths. The
holes may be scattered widely apart, or they may be
crowded closely together; in the former case, the
defect is termed “ isolated pitting,” and in the latter,
“ close pitting.”

In making an examination it is necessary first to
discover the defects, and then decide whether or not
they are important. It should be obvious that isolated
pitting is net a serious defect, even when the pittings
are deep, because only a comparatively small propor-
tion of the plate is affected. Close pitting is more
important, but still, not as a rule very serious; it
should, however, be watched, since after a time the
holes may become gradually merged into one another,
so that most of the original surface of plate, locally,
disappears (see fig. 2). This is “confluent pitting,”
or “ irregular wasting,” and whether or not it is
of a serious nature will depend upon the depth
of the wasting, the thickness of plate, and the area
of plate surface affected. Some experience is required
before one can ascertain with any degree of certainty
the depth of the wasting. In serious cases the best
plan is to drill a hole through the plate, so that the
actual thickness of the metal remaining may be
correctly determined. Hammer testing will often serve
to show if a plate is deeply wasted, since a thin plate
will ‘‘yield ’ ’ somewhat under the blow from the
hammer.

A very dangerous form of corrosion is that known
as “ smooth wasting,” where the plates become wasted
uniformly and smoothly over a large area. This de-
fect, which occurs both internally and externally, is
difficult to detect, because the plate surface does not
appear to have suffered in any way. It may best be
discovered by making a careful examination of the
riveted seams, when it will be observed that the plate
under the rivet heads stands up above the general
surface of plate, the rivet heads having served to
protect it from the action of the water. (See fig. 3.)

Grooving is another internal defect, commonly re-
garded as a dangerous form of internal corrosion,
although, as will be explained, it is originally quite a
different defect from internal corrosion. It may develop
as a fine fracture or as a rounded groove, and in Lan-
cashire boilers is mostly found at the front end, either
in the end plate round the flanges of the tubes, or
in the roots of the flanges or the angle rings. It may
also occur in the end plate adjacent to the circum-
ferential joint of the shell and the end plate.

Occasionally the defect occurs at the circumferential
and the longitudinal seams. At the longitudinal
seams it is a particularly dangerous defect, because
the boiler is weakest in the direction of its length,
being only one-half as strong longitudinally as
circumferentially.

Examples of grooving are shown in figs. 4, 5, 6 and 7.
Fig. 4 illustrates grooving in the end plate round the
furnace tube flange.

In modern high-pressure boilers, the grooving often
occurs in the root of the flanges of the tubes, at the
front end, and takes the form of a fine fracture,
as illustrated in fig. 5.

Fig. 6 shows a fine groove at the longitudinal seam
of the shell, and fig. 7 a rounded groove in an end
plate flanged outwards to receive the furnace tubes.

Fractures in Lancashire boilers are nowadays far less
common than they were at one time, but as they
occasionally develop, even in boilers of the most
modern construction, it is well to keep a sharp look-
out for them. A magnifying glass will be found very
useful in discovering fine grooves and fractures.
Perhaps the most common type of fracture is that
which extends from a rivet hole to the edge of the plate;
it is known as a “ lap-edge’’fracture, and is mostly
met with at lap-riveted seams which are exposed to
intense heat. At one time it was a common defect in
the lap-riveted furnace tubes of Lancashire boilers.

Sometimes the fracture will extend into the solid
plate on the other side of the rivet hole. It is then
of a more serious nature, and should receive early
attention. The insertion of a stop rivet at the end
of the fracture will generally prevent any further
extension.

A single lap-edge fracture is not a serious defect,
but if a number occur close together they may impair
the strength of the joint to an objectionable extent.

A far more serious defect is a fracture which extends
through a number of rivet holes round the circular
seams of the shell. This is known as a seam rip, or
rent, and although rarely met with in Lancashire
boilers, is common in egg - ended externally - fired
boilers, a most objectionable type of boiler, which,
unfortunately, is still used at collieries. When a seam

Fig. 3.

rent occurs, it is liable, under working conditions, to
extend completely round the shell; and in the case of
an externally fired boiler, there being no internal tubes
to lash the end plates securely together, as in the
Lancashire boiler, a most disastrous explosion may
result.

In dish-ended boilers, more particularly those not
of recent construction, fractures are occasionally met
with in the root of the flange connection to the shell,
the result of improper treatment in the manufacture
of the plate, and a close examination of the flange
should always be made. If the boiler is of the water-
tube type, such a fracture may lead to a violent ex-
plosion, as there are no internal tubes to stay the ends.

External Examination.

The principal defect to be looked for at the external
examination is wasting of the outer surfaces of the
plates—i.e., external corrosion.

Of all the troubles from which steam boilers suffer,
there is perhaps none which has in the past led to
so many explosions as external corrosion. At collieries,
in particular, this defect has generally been the prin-
cipal cause of deterioration, the reason being that at
these places the conditions are often such that the
defect has every opportunity of developing.

External corrosion is mostly caused by damp in con-
tact with the plates. Large numbers of colliery boilers
are unhoused, and are thus exposed to the weather.
Many of them are not only set on unnecessarily broad
seatings, but are covered over with brickwork, with
the object of preventing loss of heat by radiation.
Now, there is nothing so favourable to external corro-
sion as damp brickwork in contact with the plates.
When water is allowed to reach the setting, it is readily
absorbed by the brickwork, which is porous, and may
be thus spread over large areas, with the result that
the boiler plates are liable to become extensively
corroded. To make matters worse, the plates cannot
be examined until the brickwork bearing against them
is removed, and hence there is a risk that the wasting
will continue undetected until the condition of the
boiler becomes dangerous.

In making an external examination, therefore, the
parts which should receive particular attention are
those which bear against the setting—i.e., the plates
at the seatings, the flue covers, the front cross and
blow-out recess walls, and, if the boiler is covered by
brickwork, the whole of the shell crown. If a thorough
inspection is to be made, the plates must, of course,
be bared of all brickwork, but firms will rarely go
to so much trouble and expense. In all cases, however,
where boilers are unhoused, and where the boilers are
set on wide seatings and covered with brickwork, it
is strongly recommended that the whole of the plates
be bared at least once every four or five years.

If the boilers are satisfactorily housed, set on narrow
seatings and covered with composition, it will generally
be sufficient to plough through the seatings and the
flue covers at the rivetedz seams every two or three
years, since it is at the seams where the wasting is
most important. The composition should, of course,
be removed at intervals of a few years.

External corrosion is, in most cases, easily detected,
since the plates affected usually present a roughened
appearance. It should be particularly looked for at
the lower parts of the front end plate and about