09-11-2012, 06:06 PM
Different types of pumps
2895-Different types of Pumps.pdf (Size: 61.51 KB / Downloads: 51)
T IKE MANY OTHER m e c h a n i c a l a flat-seating metal valve. Once the water has been lifted into the pump
barrel the flap valve prevents backflow,
and as the plunger descends the
valve in it permits water to be displaced
above-and on the next stroke
it is lifted and flows out of. the spout.
L devices, pumps have become
largely of established design
according to particular functions
-a state which is likely to continue,
except for detail alterations arising
either from changes in layout,
or from introduction of new
materials. Always keeping in
mind the necessity to limit complication
and expense, the reason
why such and such a pump is
preferred, or is more practical in
particular circumstances, is generally
obvious when conditions are
analysed.
For raising a fluid like water from
a shallow well, the ordinary handoperated
“ lift ” pump, A, can be
employed. The rising pipe has a
flange on which the body of the pump
is bolted, the joint washer between
them, usually of pliable leather, in-
Eorporating a flap valve.
The pump plunger comprises an
inverted cup leather or “ bucket ” and
LEATHER
15 NOVEMBER 1956 691
Limit of lift, set by atmospheric
pressure and weight of water, is
about 30 ft. For greater depths the
pump must be down the well and the
body extended upwards by a pipe.
Alternatively, when the pump is a
force type the plunger is mounted on
a round rod which passes through a
gland in the top cover, where there is
generally another valve to hold the
column of water above the plunger.
The ordinary cycle or motorcycle
pump (and the type used on small
blowlamps) also employs a cup leather
plunger, B. Because air is the fluid
pumped it is possible to dispense with
a valve on the plunger, this function
being taken over by the cup leather
being flexible enough to’permit air to
pass on the return stroke.
Small plunger pumps
A small force pump, as may be
used on a model to feed a boiler, is
usually to a design resembling that at
C. The plunger has a packing gland
to obviate leakage and two ball valves
are arranged one above the other.
For convenience in reaming or
lapping the pump bore in small sizes,
it can go right through the body and
be blanked off by a screw-in cap.
The valves should rest on flat seatings,
and their lift be limited. Saw nicks
across the faces above the valves
prevent flow being stopped by the
balls covering the holes.
When the fluid pumped is oil, and
operation is slow, an oscillating type
of pump can be used-oil feed on
some motorcycle engines.