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The El Indio gold mine backfill
pump transports a 76% Cw cement based paste fill to the voids left by
the mining operations. The paste mixer discharges into the hopper, which is open and tapered to suit
the feed requirements. South Deep mine in South Africa transports backfill over 1250 metres from the
underground crushing plant to the elevated stopes where the 85%Cw mixture of crushed waste and 15
mm aggregate helps to prevent rock bursts.
DHT – Piston
pump with transfer tube
The model DHT’s
pump water end comprises a
hopper with transfer tube. This S-form
pipe pivots
on the discharge side whilst the inlet is intermediate
between the opening of the paired cylinders.
At the end of a suction stroke it covers the cylinder
opening and isolates the filled cylinder from the
suction hopper. During the subsequent discharge
stroke, the piston forces the product through the
tube into the discharge
pipe. During switch over the
tube partly overlaps and short-circuits the cylinders
for a fraction of a second. When pumping a paste
consistency, the backflow from discharge to hopper
will be minimal and the resulting pressure pulsations,
while not insignificant, will be quite acceptable in an
adequately anchored piping system.
The tube inlet opening is fitted with a nozzle, which
slides over a wear plate. Where the tailings are
particularly abrasive, ceramics improve wear and
galling resistance.
The size SR2 and SR3 hoppers are unique in that a
hydraulic thrust load is generated, which pushes the
tube against the wear plate. The tube nozzle is not
required to move axially, but is flexibly mounted to
compensate for uneven wear and misalignment.
The swivel cylinders are positioned at a slight angle
such that the nozzle to plate contact is maintained
when the
pump is idle. The tube turning lever is
mounted on a tapered polygon, which provides a
long term clearance-free and shock resistant fit.
Municipalities have embraced the DHT
pump for transferring
dewatered biological sludge. The centrifuged sludge or filter cake is
stocked in silos from where it is fed into incinerators. A twin screw
feeder assists in feeding the
pump. Often, water lube is employed
to reduce the friction loss between the plug flow and wall of the
discharge
pipe. It is not uncommon to fit the feed
pump with a
hydraulic activated
valve to reduce pressure pulsations due to flow
fluctuations. These smaller
pumps have a diverging transfer tube,
splined shaft and manual end float adjustment.
Positive tube thrust puts an
end to manual tube end float
adjustment and premature tube
replacement due to washout
of the tube and wear of the
splined shaft.
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