The illustrations, Figs. 302 and 303, are sectional views of one side,
or half, of the Worthington steam pump, showing two different designs.
They illustrate the interior arrangement of the pump. The valve, as may
be seen at, E, is an ordinary slide valve; the motion of this valve is
controlled by a vibrating arm, F, which swings through the whole length
of the stroke. The moving parts are always in contact, which ensures
smooth and even motion.
_This valve motion is the prominent and distinguishing characteristic
of the Worthington duplex pump._ Two steam pumps are placed side by
side and so combined that one piston acts to give steam to the other,
after which it finishes its own stroke and waits for its valve to be
acted upon by the other pump before it can renew its motion. This pause
allows the water valves to seat quietly, and removes any harshness of
motion. As one or the other of the steam valves is always open, there
is no dead point, and therefore the pump is always ready to start when
the steam is admitted.
[Illustration: FIG. 304.]
_In the plunger and ring pattern_, Fig. 302, there is a double-acting
plunger, B, working through a deep metallic ring bored to fit the
plunger. The plunger is located some inches above the suction valves,
leaving a _settling chamber_, into which any foreign substance may
fall out of the way of the wearing surfaces. Both the plunger and ring
can be taken out and either refitted or, when necessary, renewed. The
valves consist of small discs of rubber, or other suitable material,
and are easily accessible through convenient handholes. This pattern is
recommended where the liquid to be pumped contains small quantities of
grit or foreign material, or where there is an unusually long or high
suction lift.
_In the piston-pattern pump_, Fig. 303, there is a packed water piston,
G, working in a brass-lined cylinder, H. Both the suction and the
discharge valves are located above the water pistons, so that the
pistons may be at all times submerged. This pattern is recommended
where the liquid to be pumped _contains no grit or foreign material_.
Fig. 304 _shows the Worthington Admiralty pattern boiler feed pump_
which is designed to meet the requirements of the United States Bureau
of Steam Engineering for steam boiler pressure up to 250 lbs. to the
square inch. The ordinary slide valves are replaced by piston valves
with outside, adjustable, lost-motion links, making it possible to
readily adjust the stroke. The water end is made of composition, gun
metal, or cast-iron, as desired. When made of cast iron the water end
is brass-fitted throughout.