March 13, 1911.

THE COLLIERY GUARDIAN.

565

Electric Pumping Plant at Tilmanstone Colliery.

By H. J. WROE.

From a Paper read before the Association of Mining Electrical Engineers (London Branch).

The coal measures at Tilmanstone are buried under a
considerable thickness of secondary strata, and directly
overlaid by a sandbed 22 ft. thick. This sandbed, which
was met with at a depth of 1,150 ft., was found to be
heavily watered, and the water in the first instance was
proved by boreholes carried in advance from the bottoms
o£ two of the shafts. As the pressure of water was con-
siderable, it was decided to make a pumping station in
the hard oolitic limestone immediately overlying the
sandbed and to instal three horizontal - type steam
pumps, each having a capacity of 500 gallons per
minute. The water was admitted to the pump chambers
through a series of boreholes, the flow being controlled
by a valve fitted to a safety boring device.

Boring Apparatus.

This safety boring apparatus, designed by the writer
and illustrated in fig. 1, consists of two tubes sliding
one within the other, the lower ends being fitted with
flanges turning outwards. The upper end of the tubing
is provided with a side tap and a through-way valve.
The diameter of the borehole to admit a 2|-in. bore tube
was 4^ in., and this larger borehole was made specially
for the reception of the boring apparatus. It was
eventually found that the volume of the feeder exceeded
the capacity of the pumps installed, and it was decided
to instal electrically-operated pumps. This decision was
hastened by the bursting of two pipes in the delivery
column, which resulted in the flooding of the shafts as
far up as the pump inset at a depth of 600 ft.

Pumps at 600 ft. Inset.

The arrangements adopted for unwatering the shafts
are shown in figs. 2, 3 and 4. A pump inset with suit-
able waterways and cable ducts was made at the 600 ft.
level, and in it was installed a horizontal stationary Sulzer
pump, direct coupled to an A.E.G. three-phase motor,

fitted with overload and no-volt releases (the latter
being interlocked with the starting transformer), and
further with an emergency stopping switch fixed on the
frame of the sinking pump. Owing to these inter-

Fig. 1.—Safety Boring Apparatus Used at
Tilmanstone Colliery.

Plan tpmuch A-B

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emergency switch fixed on the frame of the sinking
pump. The breaking of the emergency switch trips the
oil switch on the pump-room switchboard.

Cables.

The cables for the sinking-pump motors were carried
from the switchboard along the water ducts to the
cable drums, connection to the latter being made
through slip-rings mounted on the cable-drum shafts.
The pilot cable for stopping either sinking-pump motor
was also carried in a similar manner to a small cable
drum (see figs. 2 and 3). The cable drums have steel
plate sides and laggings, and are mounted on shafts
carried by strong angle-iron frames. Current was led
through slip-rings fixed to the drum shaft, the slip-
rings being totally enclosed in a cast-iron case. Each
cable drum was operated by hand through the medium
of worm gearing, a screw brake being provided for
securing the drum each time the cable was raised or
lowered in the shaft.

The high-tension sinking-pump cables were of the
three-core rubber - insulated and double steel - wire
armoured type, each core having a sectional area of
0’1 square inch. The armouring consisted of specially
fine steel wire to render the cable thoroughly flexible.
-■•;:Each cable passed from the cable drums over the
water ducts, and was carried over a series of hardwood
rollers arranged in such a way as to give as large a bend
as possible at the point where the cable entered the
shaft. Each cable was connected to the pump motor
by a suitable watertight cable-end box, the end of the
cable being brought up from below with a view to
preventing moisture finding its way into the cable box.

Support for both the main and pilot cables was
provided by clams resting on and bolted to the main
clams carrying the pipe column (see fig. 5). A special
feature of the clam is the provision for liberating the
cables without the necessity for removing the main pipe
clams, and this arrangement proved a great advantage
on several occasions.

The delivery columns consisted of 10-in. bore steel
pipes, clammed at intervals of 36 ft. to the pump
suspension ropes, provision being made for the free
movement of the ropes through holes in the clamps.

Sinking Pumps.

The two sinking pumps, supplied by Messrs. Sulzer
Brothers, were of the centrifugal type arranged with



Water Duct

Fig. 2.—Plan showing General
Arrangement of Electric Pumping
Plant at the 600 ft. Inset.

Sinking Pump7>

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wound for 3,000 volts, 50 periods. Two sinking pumps
were suspended in the shaft on steel wire ropes. The
control of the fixed horizontal pump, and of two sinking
pumps was carried out from a switchboard mounted in
the 600 ft. pump room. This switchboard consists of
10 switch pillars built of sheet steel and totally enclosed.
Three of these are feeder pillars, the 0’15 square inch
paper-insulated shaft cables ending in cable end boxes
mounted in the pillars. One pillar was provided for the
horizontal pump motor, and two pillars for each of the
sinking pump motors. The two remaining pillars were
provided for motor drying out, one being occupied by
the necessary switchgear, the other containing a 150-
k.v.a. step-down transformer fitted with tappings on the
low-tension side. This arrangement makesit possible
to dry out any motor if same has been standing for some
time, or after a motor has been submerged. The isola-
ting links on the motor pillars are designed as change-
over switches for this purpose. This transformer is
also available for keeping in perfect working order any
idle motor acting as a stand-by. The three-feeder panels
are fitted with no-volt releases, pilot lamps (in duplicate)
which show when the feeder is connected to the bus-
bars in the power house, and isolating links which are
provided on either side the oil switches, the links being
interlocked with the oil switches to prevent their being
opened when current is on. The horizontal motor pillar
contains an oil switch fitted with overload and no-volt
releases, the latter being interlocked with the liquid
starter, thus preventing the oil switch being closed
unless the starter is in the starting position.

Each sinking-pump motor was started by its own
transformer, contained in a separate pillar, the adjoining
pillar being provided with an oil switch, isolating links
and instrument transformers. The oil switch was also



the

locking connections, it was impossible to close
motor oil switch unless the starting transformer was in
the starting position, but in case of emergency the
motor can be stopped instantly by opening the

vertical spindles. Each was capable of delivering 1,200
gallons of water per minute against a maximum mano-
metric head of 870 ft., with four impellers. An ejector
operated by pressure water from the delivery column
was connected with the top of the pump casing, from
which it evacuated any air taken in by the pump should
the latter be working “ on snore.”

The oil wells for the bearings of the pumps and
motors were water-jacketed, the water being taken from
the first stage of the pump. In order to prevent sand
entering the water-jackets, the cooling water was passed
through a filter.

Each sinking pump was coupled by means of an
elastic coupling to a totally - enclosed three - phase
squirrel-cage motor, each motor being capable of
developing at 3,000 volts, 50 cycles, a continuous output
of 500 b.h.p. at a synchronous speed of 1,500 revolutions
per minute.

The leading characteristic of the motor design is the
combination of air and water cooling, the rotors being
fitted with fans which equalised the temperature in the
interior of the motor, and prevented the formation of
heat pockets. The stator windings were water-jacketed,
the cooling water being obtained from the first stage of
the pump.

Special arrangements had to be made for keeping the
water-jacket of the motor free from accumulations of
sand. The arrangement made by the makers for
removing sediment from the base of the motor-jacket
consisted of a number of screwed plugs which could be
removed when the motor was standing. These were
dispensed with, and were replaced by gunmetal cocks by
means of which the water-jacket could be flushed at
frequent intervals while the pumps were at work,
without interfering with the cooling water supply,