[Footnote 1: Built by the Southwark Foundry and Machine Company,
of Philadelphia.]
By H.R. CORNELIUS.
In December, 1883, bids were asked for by the United States government
on pumping machinery, to remove the water from a dry dock for vessels
of large size.
The dimensions of the dock, which is situated on San Pablo Bay,
directly opposite the city of Vallejo, are as follows:
Five hundred and twenty-nine feet wide at its widest part, 36 feet
deep, with a capacity at mean tide of 9,000,000 gallons.
After receiving the contract, several different sizes of pumps were
considered, but the following dimensions were finally chosen: Two 42
inch centrifugal pumps, with runner 66 inches in diameter and
discharge pipes 42 inches, each driven direct by a vertical engine
with 28 inch diameter cylinder and 24 inch stroke.
These were completed and shipped in June, 1885, on nine cars,
constituting a special train, which arrived safely at its destination
in the short space of two weeks, and the pumps were there erected on
foundations prepared by the government.
From the "Report of the Chief of Bureau of Yards and Docks" I quote
the following account of the official tests:
"The board appointed to make the test resolved to fill the
dock to about the level that would attain in actual service
with a naval ship of second rate in the dock, and the tide at
a stage which would give the minimum pumping necessary to
free the dock. The level of the 20th altar was considered as
the proper point, and the water was admitted through two of
the gates of the caisson until this level was reached; they
were then closed. The contents of the dock at this point is
5,963,921 gallons.
"The trial was commenced and continued to completion without
any interruption in a very satisfactory manner.
"In the separate trials had of each pump, the average
discharge per minute was taken of the whole process, and
there was a singular uniformity throughout with equal piston
speed of the engine.
"It was to be expected, and in a measure realized, that
during the first moments of the operations, when the level of
the water in the dock was above the center of the runner of
the pumps, that the discharge would be proportioned to the
work done, where no effort was necessary to maintain a free
and full flow through the suction pipes; but as the level
passed lower and farther away from the center there was no
apparent diminution of the flow, and no noticeable addition
to the load imposed on the engine. The variation in piston
speed, noted during the trial, was probably due to the
variation of the boiler pressure, as it was difficult to
preserve an equal pressure, as it rose in spite of great
care, owing to the powerful draught and easy steaming
qualities of the boilers.
"After the trial of the second pump had been completed the
dock was again filled through the caisson, and as both pumps
were to be tried, the water was admitted to a level with the
23d altar, containing 7,317,779 gallons, which was seven feet
above the center of the pumps; this was in favor of the pumps
for the reasons before stated. In this case all the boilers
were used.
"Everything moved most admirably, and the performance of
these immense machines was almost startling. By watching the
water in the dock it could be seen to lower bodily, and so
rapidly that it could be detected by the eye without
reference to any fixed point.
"The well which communicates with the suction tunnel was
open, and the water would rise and fall, full of rapid swirls
and eddies, though far above the entrance of these tunnels.
Through the man hole in the discharge culvert the issuance
from the pipes could be seen, and its volume was beyond
conception. It flowed rapidly through the culvert, and its
outfall was a solid prism of water, the full size of the
tunnel, projecting far into the river.
"During a pumping period of 55 minutes, the dock had been
emptied from the twenty-third to two inches above the sixth
altar, containing 6,210,698 gallons, an average throughout of
112,922 gallons per minute. At one time, when the revolutions
were increased to 160 per minute, the discharge was 137,797
gallons per minute. This is almost a river, and is hardly
conceivable. After the pumps were stopped, on this occasion,
tests were made with each in succession as to the power of
the ejectors with which each is fitted to recharge the pumps.
"The valves in the discharge pipe were closed and steam
admitted to the ejector, the pump being still and no water in
the gauge glass on the pump casing, which must be full before
the pumps will work. The suction pipe of the ejector is only
two and a half inches in diameter, the steam pipe one inch in
diameter. To fully charge the pumps at this point required
filling the pump casing and the suction pipe containing about
2,000 gallons; this was accomplished in four minutes, and
when the gauge glass was full the pump operated instantly and
with certainty, discharging its full volume of water.
"I went on several occasions down in the valve pits on the
ladder of the casing, and to all accessible parts while in
motion at its highest speed, and there was no undue
vibration, only a uniform murmur of well-balanced parts, and
the peculiar clash of water against the sides of the casing
as its velocity was checked by the blank spaces in the
runner.
"The pumps are noisy while at work, due to the clashing of
the water just mentioned, but it affords a means of detecting
any faulty arrangements of the runner or unequal discharge
from any of its openings. While moving at a uniform speed,
this clashing has a tone whose pitch corresponds with that
velocity of discharge, and if this tone is lacking in
quality, or at all confused, there is want of equality of
discharge through the various openings of the runner. To this
part I gave close attention, and there was nothing that the
ear could detect to indicate aught but the nicest adjustment.
The bearings of the runners worked with great smoothness, and
did not become at all heated. Through a simple, novel
arrangement, these bearings are lubricated and kept cool.
There is a constant circulation of water from the pumps by
means of a small pipe, which completes a circuit to an
annular in the bearings back to the discharge pipe while the
pump is in motion, requiring no oil and making it seemingly
impossible to heat these bearings.
"The large cast steel valves placed in the embouchement of
the casing, it was thought, might act to check the free
discharge, and arrangements were provided for raising and
keeping them open by a long lever key attached to their axes
of revolution, but, to our great surprise, at the first gush
from the pumps these valves, weighing nearly 1,500 pounds,
were lifted into their recessed chambers, giving an
unobstructed opening to the flow, and they floated on its
surface unsupported, save by the swiftly flowing water,
without a movement, while the pump was in operation.
"The steam-actuated valves in the suction and discharge pipes
worked very well, and the water cushion gave a slow, uniform
motion, and without shock, either in opening or closing them.
"The engines worked noiselessly, without shock or labor. At
no time during the trial was the throttle valve open more
than three-eighths of an inch.
"The indicator cards taken at various intervals gave 796
horse power, and the revolutions did not exceed 160 at any
time, though it was estimated that 900 horse power and 210
revolutions would be necessary to attain the requisite
delivery. So that there is a large reserve of power available
at any time.
"The erection of this massive machinery has been admirably
done. The parts, as sent from the shops of the contractor,
have matched in all cases without interference here; and,
when lowered into place, its final adjustment was then made
without the use of chisel or file, and has never been touched
since.
"The joints of the steam and water connections were perfect,
and the method of concentrating all valves, waste pipes, and
important movements at the post of the engineer in charge
gives him complete control of the whole system of each engine
and pump without leaving his place, and reduces to a minimum
the necessary attendance. All the parts are strong and of
excellent design and workmanship; simple, and without
ornamentation.
"Looking down upon them from a level of the pump house
gallery, they are impressive and massive in their simplicity.
"The government is well worth of congratulation in possessing
the largest pumping machinery of this type and of the
greatest capacity in the world, and the contractors have
reason to be proud of their work."--_Proc. Eng. Club._
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