==========================+=========+==========+=========+========
NUMBER OF TEST. | No. 1. | No. 2. | No. 3. | No. 4.
--------------------------+---------+----------+---------+--------
Steam pressure—high | 70 | 120 | 125 |
steam cylinder | lbs. | lbs. | lbs. | --
| | | |
Steam pressure—low steam | | | |
cylinder | 20 lbs. | 40 lbs. | 45 lbs. | 50 lbs.
| | | |
Vacuum in condenser |27-1/2in.| 27in. |26-1/4in.| 25in.
| | | |
Double strokes per minute | | | |
—high side | 37 | 61 | 82 | --
| | | |
Double strokes per minute | | | |
—low side | 35 | 60 | 82 | 88
| | | |
Temperature of hot well— | 106 | 105 | 108 | 112
Fahrenheit | deg. | deg. | deg. | deg.
| | | |
Water pumped per hour— | 13,500 | 22,700 | 30,000 |
high side | lbs. | lbs. | lbs. | --
| | | |
Water pumped per hour— |12,700 |22,300 |30,200 |36,000
low side | lbs. | lbs. | lbs. | lbs.
| | | |
Total water per hour | 26,200 | 45,000 | 60,200 | --
| lbs. | lbs. | lbs. |
| | | |
I. H. P. of high steam | | | |
cylinder | 0.60 | -- | -- | --
| | | |
I. H. P. of low steam | | | |
cylinder | 0.58 | -- | -- | --
Total I. H. P. | 1.18 | -- | -- | --
--------------------------+---------+----------+---------+------
[Illustration: FIG. 350.]
_The Deane Vacuum Pump._ There are a number of novel features exhibited
in the construction of this pump; the cylinder has four ports, that is
to say _two steam or admission ports and two compression or cushioning
ports_.
Referring to the engraving, page 42, Fig. 6, shows the main valve to
be a plain ^D^ slide,—directly under it the same valve is shown in
section. The projection on the back of this valve fits into the valve
piston. The secondary valve, 5, surrounds the main valve and contains
two plain slide valves, one on each side. Referring to 3, it will be
noted that one of these valves admits steam while the other allows the
steam to escape after having done its work of moving the valve piston.
A longitudinal section of this secondary valve and steam cylinder are
shown, in 2.
In the engraving, 1, it is shown that the cylinder for each end of the
valve piston is jacketed with live steam so that the cylinder itself
heats up as quickly as the valve piston, hence the piston cannot stick
in the cylinder due to unequal expansion of valve and seat.
The supplemental valve ports are shown in section 4.
_To set the valve of this pump_: Remove the steam chest, place the
piston at mid stroke with the lever, plumb, then set the stem at its
mid position with the secondary valve in place. See that the tappets
measure equal distances either side of the tappet block.
NOTE.—These small ports are not liable to fill with oil and dirt in
practice, on account of their direct connections. If through leakage
or any other reason the valve piston should fail to throw the main
slide valve, the projection B (see 1) on the valve stem (of which it
is a part) compels the valves to move mechanically. So when steam is
turned on, this pump is certain to begin its work.
[Illustration: FIG. 351.]
The water end of this pump consists of a cylinder with valve chambers
as shown. The piston rod has two stuffing-boxes, which makes a water
seal around the rod so that no air can enter the cylinder, as the
chamber between the two stuffing-boxes is kept constantly filled with
water. It will be noticed that the suction pipe enters the pump
in such a position in relation to the valves that both suction and
discharge valves are perpetually immersed in water.
When this pump is pumping air only, there is sufficient water left
within the valve chambers to provide a water seal under all working
conditions. The valves in this pump are easily reached for inspection
or repairs, a hand-hole being provided for each valve, with proper
covers, which are easily and quickly replaced.
_The Worthington Vertical Beam Vacuum Pump_ with condenser attached is
shown in Fig. 351.
This is a pump of great simplicity and strength. The figure shows _a
compound engine_ for using high pressure steam; these machines can be
built with simple steam cylinders of equal diameters, but they are
not recommended except in special cases; for example where the steam
pressure is very low. Each side of the pump end is single-acting, the
buckets being of the form used for years in detached air pumps in
marine service. The two sides are connected together by a beam and
links attached to the cross-heads. As one side comes down and does
little work, the other side makes an up-stroke and does full duty in
emptying the condenser to which the suction is attached.
The condensing chamber is usually placed at the rear and connects
directly with the channel plate at the bottom of the pump. The opening
shown in front is for the discharge water.
The steam cylinders are so arranged that either piston may be examined
by removing its cylinder head, without disturbing the other cylinders.
The valves are of the Corliss, or semi-rotative, type and the
high-pressure cylinders are provided with cut-off valves to assure the
desired ratio of expansion.
The interior of each air cylinder may be inspected by removing the
plates shown in front, near the middle. There are also two plates at
the top for inspection of the discharge valves. The four machinery
steel columns form a light but very strong frame allowing free access
to the working parts.
[Illustration: FIG. 352.]
The next four cuts show Dean Brothers’ twin cylinder air pumps with
their special steam valve gear. They are made for and supplied with
either surface or jet condensers. See Fig. 352.
The arrangement of the valve gear is such that steam will be applied at
the upper end of one piston at the same instant that it begins to act
on the lower end of the other. By this device steam is so controlled in
the steam chests that no pressure comes on the main pistons, until the
moment that both are ready to move, after having reached the full limit
of their stroke, thereby securing an exactly uniform, but opposite,
motion of the pistons. Fig. 354 is a sectional elevation of the steam
cylinder and steam chest; Fig. 353, a front elevation; Fig. 355, a
section of the air cylinder, and Fig. 352, an exterior perspective view
of the pump.
Each steam cylinder has its own steam piston, piston rod, valve
movement, steam chest, etc. A sleeve, _a_, is rigidly attached to each
piston rod, and connected to this sleeve is a lever, _b_, the outer
end of which connects with a link, _c_, which in turn is connected to
a sleeve, _d_, loosely mounted upon the valve rod between collars,
_e_. The valve rod, _f_, operates the auxiliary slide valve and admits
the steam from above and below the auxiliary piston. This piston has
attached thereto the main slide valve, which admits and exhausts steam
alternately from above and below the main steam pistons. Any movement
of the main piston communicates movement in the opposite direction to
the sleeve, _d_, which moves the valve rod only when it strikes one or
the other of the collars. As there is considerable lost motion between
the sleeve and the collars, the main steam piston will be nearing the
end of its stroke when the valve rod begins to move.
[Illustration: FIG. 353.]
Extending through the ends of the steam chests are short piston rods,
_g_, which are connected to a centrally pivoted vibrating lever, _h_,
mounted on a pivot. When the main steam piston has moved from the top
to the bottom of the steam cylinder, the corresponding valve rod has
moved in the opposite direction and the auxiliary slide valve has
moved upward, opening the port, _i_, to steam and the port, _k_, to
the exhaust port. At the moment the main steam piston has completed
its downward stroke the auxiliary piston is forced upward and carries
with it the main slide valve, _l_. This opens the main steam port and
exhaust port, which reverses the movement of the main piston. When the
main piston reaches the upward limit of its stroke the auxiliary valve
has moved downward, opening the port, _k_, to steam and the port, _i_,
to the exhaust, causing the auxiliary piston to move downward, thus
reversing the movement of the main valve and piston.
By this arrangement the valve operating piston, _m_, is held at all
times immovably at one end of the stroke, except when the main piston
is nearing the end of its stroke and is ready to reverse. Supposing
the left-hand main piston has not quite reached the upper limit of the
stroke, the steam would still be on the lower side of its auxiliary or
main valve operating piston and the exhaust open to the other side. We
now have steam on the bottom side of both auxiliary pistons, and as
they are of equal diameters and are connected by the lever, _h_, they
are balanced and cannot move the main steam valves. The right-hand main
steam piston must wait until the left-hand piston has completed its
stroke before it can reverse, and consequently the movement of the main
pistons will always be in opposite directions, and neither can reverse
until both have completed their stroke.
[Illustration: FIG. 354.]
[Illustration: FIG. 355.]
There are three ways that this apparatus may be operated: First,
the pumps may be operated in conjunction with each other, as is
hereinbefore described. Second, the lever, _h_, may be detached from
the auxiliary or main valve operating pistons, and the two pumps may
then run independently of each other or in the ordinary and well-known
manner, each performing its own independent work. Third, by further
detaching the link, _c_, on one of the valve gears the auxiliary slide
valve, _n_, will remain at rest and the corresponding pump will not
move while the other pump continues to operate. These are important
features, because, as in case of accident, it may be necessary to
use one pump while the other is disabled, and in some cases it may
be desirable to operate the pumps independently. The engineer will
appreciate this feature, as the stoppage of an air pump is a serious
matter.
The piston rods are separable at the crossheads. The crossheads are
of steel. The steam cylinders and pump cylinders are connected by
six heavy steel stretcher rods. Adjusting valves are fitted to steam
cylinders for controlling motion of pistons. The valve gear is provided
with a special lever adjustment by which the length of stroke of
pistons may at any time be changed, even while the pump is running.
In Fig. 356 is shown a form of independent vacuum pump, with its
condenser, built by the Conover Mfg. Co.
This apparatus consists of a jet condenser with air pump, boiler feed
pump, and engine to drive both, combined as one machine. The air pump
is a single acting bucket plunger pump, driven by a crank shaft, turned
by the engine, which is a single cylinder compound automatic cut-off
engine, and also drives the boiler feed pump; it is of the trunk
pattern, and the small space around the trunk on the top side of the
piston forms the high pressure cylinder. Steam is admitted to the high
pressure side, at boiler pressure, and is cut off and expanded and
exhausted into the receiver, whence it is admitted under the bottom
side of the piston, where it is again cut off and expanded, finally
exhausting into the condenser.
_The piston makes the down stroke when the air pump makes the up
stroke_; and it will be seen by referring to the cut that the engine
does nearly all its work when making the downward stroke. When steam is
acting on the top side of piston at high pressure, the vacuum at the
same time is pulling on the full area of the piston underneath.
[Illustration: FIG. 356.]
When the engine makes the up stroke, the steam at low pressure from the
receiver acts to push the piston up; and as the air pump is doing no
work then, being on its down stroke, the only work of the engine is to
keep the machine up to speed.
[Illustration: FIG. 357.]
It will thus be seen that the engine is suited to meet the demand of
the large power on one stroke, and very little on the other, thus
adapting itself admirably to its requirements.
The valves are of the Corliss type, and do not trip; the cut-off being
set by hand, does not require to be changed or altered, as the speed is
controlled by a throttling governor.
Fig. 357 shows a cross section through the steam cylinder of this
vacuum pump.
[Illustration: FIG. 358.]
_The Edwards air and vacuum pump_ is shown in Figs. 358, 359 and 360,
in which it may be perceived that both foot and bucket valves are
dispensed with; the only valves used are those which in other pumps are
known as head or discharge valves.
The following brief description of its leading features will be
understood by reference to the illustrations: Fig. 358 is a sectional
view through the center of the air pump, but the piston and rod are
shown as a full view.
The action of this pump is as follows: the condensed steam flows
continuously by gravity from the condenser into the base of the pump,
and is there dealt with mechanically by the conical bucket working in
connection with a base of similar shape. Upon the descent of the bucket
the water is projected silently and without shock at a high velocity
through the ports into the working barrel (see Fig. 359). The rising
water is followed by the rising bucket, which closes the ports, and,
sweeping the air and water before it, discharges them through the valve
at the top of the barrel.
[Illustration: FIG. 359.]
It may be said that however slowly an ordinary air pump with foot
and bucket valves may be running, the pressure in the condenser has
to be sufficiently above that in the pump to lift the foot valves,
overcome the inertia of the water, and drive the water up through the
valves into the barrel where the water is dealt with mechanically. The
higher the speed of the older type of pump the greater is the pressure
required to overcome these resistances owing to the very short space
of time available, and as any increase of pressure in the condenser is
accompanied by a corresponding increase of back pressure in the low
pressure cylinder, hence the absence of the valves referred to allows a
higher speed of the plunger. The elimination of the foot valves it is
claimed gives from 1/2 to 1 inch better vacuum.
[Illustration: FIG. 360.]
Another advantage claimed for this pump is that clear air inlets are
maintained—see Figs. 359 and 360. Under ordinary working conditions,
when the bucket descends and the ports open, there is no obstruction
between the condenser and the pump; the air has a free entrance while
immediately afterward the water is injected into the barrel at a high
velocity. Thus, instead of obstructing the entrance of the air, the
water tends to compress that already in the barrel, and to entrain or
carry in more air with it.
The bucket or piston is a hollow casting with water grooves instead of
packing rings.
The valve seat is constructed with a rib between each valve and a lip
around the outer edge, so that each valve stands in its own water and
is separated from the others. This forms a ready means of testing the
relative tightness of each valve.
The cast iron working barrel is lined with brass.
The pump rod is Tobin bronze, and valve plate and valves of
composition. These pumps are either single, twin, triplex, and are
steam, electric or belt driven, for stationary, marine or sugar
plantation service.
The steam driven pumps are built with either single or compound steam
cylinders, fitted with new and improved valve gear, and with their
arrangement of fly-wheels, insures smooth running, making full strokes
free from vibration.
[Illustration: FIG. 361.—See page 70.]