The _theoretical action of_ a pump has already been described and
illustrated;—the _practical operation_ is described in the note below.
The subject is important enough to justify the space it takes to
present these two descriptions of the action of a pump.
[Illustration: FIG. 156.]
The parts of which a pump is composed are: 1, _the barrel or cylinder_;
2, _the plunger or piston_; 3, _the valves_; 4, _the pipes_.
The barrel of a modern pump is a tube of metal having a water tight
plunger or piston which moves freely up and down at the pleasure of the
operator. This plunger is in its simplest form made of cast iron in two
parts. The upper part consists of an arched part having a hole in its
center to receive a bolt which passes through it and a jaw on the lower
end of the pitman or connecting rod. The upper end of this pitman is
attached to the pump handle by means of a bolt. The inside of the upper
part of the plunger is threaded to receive the lower part with a cup
leather packing and contains a valve of metal having a conical seat.
Fig. 156 shows a design of a pump in common use in the 14th century.
NOTE.—The action of a pump is as follows: The piston or plunger by
moving to one end, or out of the pump cylinder, leaves the space it
occupied, or passed through, to be filled by something. As there is
little or no air therein a partial vacuum is formed unless the supply
to the pump is of sufficient force to follow the piston or plunger
of its own accord. If this is not the case, however, as it is when
the water level from which the pump obtains its supply is below the
pump itself, there being a partial vacuum produced, the atmospheric
pressure forces the water into the space displaced by the plunger or
piston, continuing its flow until the end of stroke is reached.
The water then ceases to flow in, and the suction valve of the pump
closes, forbidding the water flowing back the route it came. The
piston or plunger then begins to return into the space it has just
vacated, and which has become filled with water, and immediately
meets with a resistance which would be insurmountable were the water
not allowed to go somewhere. (See next page.)
Its only egress is by raising the discharge valve by its own pressure,
and passing out through it. This discharge valve is in a pipe leading
to the boiler, and in going out of the cylinder by that route the water
must overcome boiler pressure and its own friction along the passages.
Water is inert and cannot act of itself; so it must derive this power
to flow into the feed pipe and boiler from the steam acting upon the
steam piston of the pump. The steam piston and pump piston are at the
two ends of the same rod. Therefore the steam pressure exerted upon the
steam piston will be exerted upon the pump piston direct.
Between the upper and lower parts of the plunger a cup leather is
introduced before these parts are screwed together. This cup leather,
while it allows the plunger to move freely, also makes a water-tight
joint.
The lower valve consists of a piece of cast-iron flat on the bottom
and circular in shape about three-eighths inch thick with a curved toe
at one side. This iron disc is secured to the flat leather valve by a
screw that passes through the valve and is threaded in the disc.
[Illustration: FIG. 157.]
The object of this toe upon the disc is to open the lower valve by
means of raising the pump handle as far as it will go which lowers the
plunger upon the toe and tips the lower valve upon its seat. This same
operation also lifts the valve in the plunger off its seat, so that all
the water in the barrel drains back into the well so the pump is kept
from freezing up in winter.
[Illustration: FIG. 158.]
The leather which forms the lower valve is held in place by clamping
the pump barrel upon it, so that it is held between the barrel and the
base plate.
Hand pumps are primarily divided into: 1, suction or lift pumps; 2,
force pumps, and 3, suction and forcing pumps; 4, also pumps for
exhausting air from vessels.
Of the first class, the common single-acting house-pumps shown in Figs.
157 and 158 are examples; the pumps are simply modifications of the
suction-pump; a common form of lift-pump has a pitman-rod which pushes
the water up instead of lifting it through a spout at or near the top
of the cylinder.
The details of the suction-pump are as follows—at the bottom of the
cylinder is a pipe communicating with the liquid to be raised, and a
valve which opens from beneath. A similar valve is placed in the piston.
A force-pump is shown in Fig. 159; from the two figures the difference
between the lift and the force-pump may be understood; while the
former raises the liquid above its piston from which it flows under
no pressure, the latter forces it out of the barrel under a varying
pressure which depends upon circumstances. When the piston rises
the suction valve opens, and the valve in the piston closes by the
air-pressure. The liquid then enters the barrel beneath the piston. On
the descending stroke the suction valve closes, and the liquid flows
upward into the discharge pipe.
[Illustration: FIG. 159.]
_In Fig. 160 is shown an air-chamber_ attached to a force-pump for the
purpose of preventing shocks in the discharge, and for producing a
steady flow; air-chambers are also frequently attached to suction pipes
for a similar purpose.
According to the underlying principles of action thus far explained
hundreds of thousands of pumps have been constructed and operated. It
is beyond the limits of this volume—or any single book to give the
names and details of these so-called “hand-pumps,” however, three
approved styles are shown in Figs. 161, 162, 163.
Fig. 161 represents a _double acting force pump_ used extensively on
ship-board, wharves, around factories, mills, etc., and in residences,
for tank pumping. On ships these pumps perform the three-fold purpose
of filling boilers when cold, washing down decks and to satisfy
government inspection as to fire protection; in service in mines
they are unaffected by mine water, the working parts being made
non-corrosive. It is claimed that a three-inch diameter cylinder with
a stroke of four and a half inches with a 1-1/4-inch suction pipe and
1-inch discharge pipe will lift and force water 150 ft. high and has a
capacity of ·28 gallons for each stroke, with the water not more than
twenty-five feet below the pump.
[Illustration: FIG. 160.]
Fig. 162 represents _a two cylinder force pump_; this has vertical
single acting pistons actuated by one lever, producing the same
results as a double-acting pump. It is claimed that the total lift
and force, from supply to point of delivery, with the pump not more
than twenty-five feet above water will attain one hundred feet; that a
3-inch × 4 inch cylinder, 1-1/2-inch suction and 1-1/4-inch discharge
will deliver ·24 gallons of water for each stroke.
Fig. 163 represents a widely used type of suction pump, it is
designed for vessels of not more than fifteen to twenty feet deep;
for contractors who wish to pump large quantities of water from
excavations, etc.; for irrigation or any other purpose where a compact
and capacious pump is desired.
The lever may be worked from three different points as shown by lugs on
the illustration. The lever socket is made at such an angle that the
bent wrought iron lever when put in one side up, is right for ordinary
pumping and by simply changing it the other side up, it becomes a
vertical lever. The valves are accessible and removable by hand from
above. It is claimed that with 8-1/2-in. diameter cylinder and 6-in.
stroke that the capacity is 1-47/100 gallons for each stroke, with 20
feet lift—the suction pipe being 3-in. in diameter.
[Illustration: FIG. 161.]
In the illustrations (Figs. 161 and 162) it will be noticed that the
discharge is conveniently arranged to receive either fire hose, or iron
pipe connections for other uses, as in mines and on ship-board.
_Being made in large factories_, there are immense numbers in
world-wide use; every detail of these pumps is carefully considered;
the sizes manufactured range from 2 inches to 6 inches diameter of
cylinders, with strokes 4, 4-1/2 and 5 inches.
_The capacity_ of each pump is also given in the published lists by the
makers; this is given under the heading “Capacity per Revolution” with
the added information as to the best sizes to be used for the suction
and discharge pipes.
[Illustration: FIG. 162.]
NOTE.—It were well for the student to know that in case of breakage
or worn out parts of an otherwise serviceable apparatus that the
makers _have provided for their repairs_ as will be indicated by the
following taken from the catalogue of a well known manufacturer. “In
the following lists will be found descriptions of pieces for all
the staple pumps, which will prove of decided convenience. In this
connection we desire to impress most emphatically on the minds of
dealers that the threads are cut to exact and accurate gauges; all
holes in flanges, etc., drilled to templets; all castings made from
exact metal patterns, similar parts being always the same. Therefore,
repairs will invariably take the place of the broken parts.”
_Fig. 163 represents a Pitcher Spout Pump_, of large size for
contractors, and Fig. 164 the parts of a common house pump. The two
figures show pumps substantially the same.
[Illustration: FIG. 163.]
The smallest size “listed” of this pump has a cylinder diameter of
2-1/2 inches, fitted with 1-1/4 in. pipe and it has a capacity of ·09
gal. per stroke and it takes more than eleven strokes to pump a single
gallon. With a cylinder 4-1/2 inches, with pipe 1-1/2 in. diam., the
pump has a capacity of ·34 gal. per stroke.
[Illustration: FIG. 164.]
The engraving 164 shows a pitcher pump dissected, in which A represents
the lever or handle, B the plunger which contains the discharge valve
and is made tight by a cup leather packing, C is the fulcrum for the
lever, D the barrel or cylinder, E the lower or suction valve, F the
base which supports the pump. The leather which forms the valve E also
makes the joint between the cylinder and the base.
Fig. 165 represents a _Two-Cylinder Suction and Force Pump_ arranged
with extension levers. When these levers are put in place, they afford
room for a large force of men to work, renders this pump a most
powerful engine for throwing water on fires, or supplying it for many
uses about factories, warehouses, wharves, etc.
The discharge hose can be fitted both ends for wrought-iron pipe or
either end for hose. The Table below gives the makers’ numbers, the
diameter of the cylinders, etc., and also distance to which the water
can be lifted or forced.
[Illustration: FIG. 165.]