Other names are derived from peculiar shape, application, mode of
actuation, etc.
_A cock_ is a faucet or rotary valve usually taking its name from its
peculiar use or construction, as:—
Blow-off cock,
Cylinder-cock,
Feed-cock,
Four-way cock,
Gage-cock,
Oil-cock,
Self-closing cock,
Steam-cock,
Stop-cock,
Three-way cock,
Try-cock,
Water-cock, etc.
NOTE.—The above classification is that made by E. H. Knight, Civil
and mechanical Engineer, etc., and author of Knight’s Mechanical
Dictionary. He adds: “The heart is created upon the principles
of hydraulics, and is furnished with a valve. Harvey deduced the
circulation of the blood from Aquapendente’s discovery of the _valves
in the veins_.”
As may be judged by the preceding paragraphs, giving the names derived
from their mechanical and other uses of several only, of a great
many varieties of valves, it were vain to attempt a complete list of
these devices; it may be said however that the whole system of modern
mechanism would be, almost, if not quite, a failure, if they were not
used.
Hence, the student will do well to familiarize himself with the valve
movements sure to be found in every combination of industrial and
mechanical forces.
A few illustrations of the adaptation of valves of various designs to
useful purposes now follow.—
_A combined throttle and quick closing trip valve_ is shown in Fig.
609, page 336; this is made by Schutte & Koerting Co., Philadelphia;
this apparatus is designed to fill the requirements of _an emergency
shut-off; the valve is balanced_ and operates as stop and throttle. The
object of balancing the valve is to remove the strain from the spindle,
so that its operation can be effected quickly and with the least
effort. The piston above the valve is not tight fitting, and contains
_a small auxiliary or pilot valve_ attached to the spindle, which opens
in advance of the opening of the main valve; thus the pressure above
the piston and below the valve is equalized; little effort is now
required to lift the main valve, at the same time the pilot valve, E,
answers the purpose of a by-pass.
The several proportions are such that a slight over-pressure is
maintained above the piston to give the valve, at all times, a tendency
to close. This over-pressure should be but slight, and to regulate it
at will there is (besides the leak around the piston) _a separate steam
admission above the piston, regulated by the plug, C_.
Depending on the fit of the piston, this plug is opened more or less,
or entirely closed, when valve is first put in operation, and then
locked in that position.
Ordinarily the construction of this valve demands the application of a
screw-spindle to actuate it; _it is also made in angle form and can be
placed with spindle upward or horizontal_. In all positions, globe,
inverted and angle valves, steam must always enter above the disc,
viz., in the direction of the arrows.
[Illustration: FIG. 633.]
_The operation by lever is demanded when a valve is used as a quick
emergency shut-off_, either by hand or in connection with automatic
appliance of governor, electrical cut-off or auxiliary, steam, air or
hydraulic cylinder.
The valve itself is of the balanced form, except that in this valve
_the spindle carries at the bottom a small piston or sleeve, F_, shown
in the figure. The valve is locked open by moving hand lever up till
the catch on same engages with the lever, G, supported on the upright
bar.
The valve being then open, steam pressure acts on the area of the
piston, F, with continuous downward force, which will cause the valve
to close as soon as the latch is released. Thus, by connecting the
rod on the outer end of lever, G, with a hand lever, at any desired
location, the operation is had without effort and promptly.
_A pressure reducing valve_ is shown in outline and a side view in
Figs. 633 and 634; this is in effect a (Mason) pump pressure regulator
and it is applicable for fire, tank, elevator, air and water works
pumps, or any class of pumping machinery where it is necessary to
maintain a constant pressure. The regulator may be quickly adjusted to
any pressure desired by turning the key as shown in Fig. 633.
The especial feature of this regulator is that the pressure chamber
into which the water enters is entirely removed and separate from the
steam and all working parts.
The long cylinder at the bottom of the regulator is a dashpot, the
piston of which is connected with the main valve of the regulator,
thereby preventing sudden and violent “jumping” of the pump when the
pressure suddenly changes. These valves are made in all the pipe sizes;
those up to and including 2-inch of the best steam metal; the largest
sizes of cast iron, lined with steam metal. _The springs are made of
the finest tool steel, tempered._
[Illustration: FIG. 634.]
The Mason Regulator Co., Boston, are to be credited with the following
directions:
The regulator is placed in the steam pipe leading from the boiler
to the steam pump and as near the pump as possible. The connection
with the water system is made either from the tank or from the water
system, at some little distance from the pump. Brass pipe should be
used if possible, for this connection. The drip should be connected
to some pipe where there is no back pressure. The steam from the
boiler enters at the point marked “steam inlet from boiler,” and
thence through the passage, X, through the port, which is kept
open by the tension of the spring, 79, upon the auxiliary valve,
80. It continues down through the passage, Z, to the under side of
the differential piston, 70, and raises the valve, 16, so that the
boiler pressure is admitted to the pump through the passage marked
“steam outlet to pump.” This starts the pump, which continues in
motion until the required water pressure is obtained in the system
and acts through the connection marked “water pressure inlet” on
the diaphragm, 74. This diaphragm is raised by the excess of water
pressure, and carries with it the auxiliary valve, 80, which closes
the port for steam pressure. By the closing of this valve, the boiler
pressure is shut off through the passage, Z, from the differential
piston, 70, and the steam pressure from the boiler immediately
closes the main valve, 16, so that no more pressure is admitted to
the pump, which remains inactive until the water pressure in the
system drops below the normal joint and relieves the water pressure
in the chamber, O, which causes the auxiliary valve, 80, to open
again, and starts the pump as before described. The check valve, 71,
which is placed in the bottom of the piston, 70, allows the pressure
regulator to open easily, but stops the pump quickly. This is a great
advantage, as the pump will not start with a jump, the moment the
water drops. By changing the tension of the spring, 83, through the
key stem, 85, the amount of water pressure can be regulated.
[Illustration: FIG. 635.]
_Mason water reducing valve._ Fig. 635 is designed to reduce the water
pressure from the street water mains to a low pressure, for houses
and buildings. The body or valve portion is fitted with couplings, so
that it may be easily attached to a pipe. That part of the valve above
the diaphragm, and which comes in contact with the water, is made of
the best steam metal, thus preventing corrosion. The long spring case
is made of heavy iron pipe, at the end of which is an iron bracket,
suitably drilled, so that the valve may be securely bolted either to
the floor or to a beam overhead. The tension of the main spring is
adjusted by means of a small rod inserted in a nut at the end of the
spring case. The diaphragm is very strong and will hold several times
the pressure required. The working of this regulator is very simple.
The water enters through the inlet coupling, 45, and passes through
the chamber, 68, into the low pressure side of the regulator, the
valve, 43, being held open by the tension of the spring, 53. When the
low pressure has attained the desired limit, which is also felt in the
diaphragm chamber through the hole which communicates with the chamber,
68, it forces down the diaphragm and seats the valve, 43. When the
pressure again drops in the system, the diaphragm is forced up by the
spring, 53, and the valve, 43, again opens.
_An automatic throttle valve_ for a boiler feed pump is shown
perspective and outline in Figs. 636 and 637; this is a governor for
the pump, controlled by the relative pressures of steam and water. It
is known as _Mullin’s automatic controller_ and is made at Seattle,
Wash., and has the following features:
[Illustration: FIG. 636.]
It is simply a balance valve and differential piston; it is in a class
by itself, both as to its construction and operation in regulating feed
water pressure in connection with steam boilers.
[Illustration: FIG. 637.]
The initial steam pressure being on the ends of the valve, has access,
through the neck, to the full area of the piston, and will force it
into a position that gives the full valve opening, where it will remain
until overcome by water pressure from the pump, acting against the
opposite side, which is of reduced area.
It is necessary in operating this valve to have _an excess of water
pressure over the steam pressure_ in the boiler. The excess of the
water pressure is obtained by the reduction of the area of the water
side of the piston—thus to illustrate—if the total area were 10 square
inches, and the reduction was one inch or 10 per cent., it would
require that the water pressure should be 10 per cent. greater than
steam pressure, to give the same thrust on the piston, then until the
water has reached a pressure 10 per cent. in excess of the steam, the
valve would be held open, but thereafter it is held open only wide
enough to admit steam to the pump to keep up this 10 per cent. excess
pressure. Should the excess pressure attempt to rise above this, it
immediately forces the steam valve nearly shut, thus nipping the cause
of the rise, namely, too great a piston speed.
NOTE.—“In starting the pump, ‘stand by’ until it has caught suction,
and accumulated nearly the correct water pressure, now open the
valve on the pulse, or pressure pipe to the controller and open pump
throttle wide, thus giving the controller free action.
“Suppose the boiler pressure is 100 pounds, the water pressure will
be 10 per cent. higher or 110 lbs. Carrying an even fire, with
water at second gauge, feed valves properly set, the load suddenly
increases, which pulls steam down to 99 pounds, the water does not
remain at 110 lbs. as before, but is now 10 per cent. in excess of 90
lbs. or 99 lbs., thus in place of 10 lbs. excess water pressure there
is but 9 lbs., which means there will be less water delivered through
the feed valves, which will hardly ever have to be touched.
“Next the load will lighten—steam will rise, and the excess pressure
will automatically increase, thus restoring the water used at a time
when it was most necessary to lighten the feed to temporarily favor
the fire.
“Suppose the load continues light, with good fires, steam rises to
110 pounds, the water will rise to 10 per cent. more pressure or 121
pounds, thus automatically giving more pressure to ‘feed up’ on high
steam, and store away the heat that would be wasted by radiation,
absorption, or perhaps blowing off.”
The water pressure will vary only as the steam pressure varies, always
keeping the same per cent. of excess. The results are directly opposite
to what would or does occur where feed water is delivered at a stated
pressure. On a battery of boilers, during the cleaning of fires, the
closing of feed valves on one, two or more boilers, does not affect the
feed of those already set in the least, the pump will simply make less
strokes necessary to properly feed the others.
The regulating is done by the feed valves at the boilers; if it is
desired, all feeds may be closed, and the pressure will not rise, the
pump will stop; if its plungers need packing it will be detected by the
fact that the pump will creep, to keep up the required pressure. When
feed valves are once regulated to admit the required amount of water,
to replace the evaporation, _they may be marked_, and when in this
position, they, with an even steam pressure, will always admit the same
amount of water to the boilers.
It is understood that this valve is placed between the ordinary
throttle valve and the pump.
[Illustration: FIG. 638.]
[Illustration: FIG. 639.]
_The Bordo blow-off valve_ is shown in Figs. 638 and 639; it consists
of a brass or iron body which resembles the shell of a plug-cock,
but with this difference, it has a sharper taper than the regular
plug-cock; in this device the plug is usually made of brass—tinned on
the outside. In process of making and while hot a sheath of babbitt
metal or its equivalent is cast upon the plug; the metals amalgamate
and practically become one casting.
The parts of valve are as follows, 1, the body, 2, the plug, 3, the
packing and lifting gland, 4, the lifting cam, 5, lock-nut, 6, two
brass rings of equal size, with a special gasket between them—all as
shown in the engravings.
_The valve is operated_ with a wrench on the square of the plug. The
lifting gland when adjusted is permanently held by a lock-nut. By
releasing the lock-nut with the wrench and turning the gland to the
left, the plug is lifted so that it will turn easily. When the lock-nut
is moved up, the lifting cam (which couples the packing gland to the
plug) can be pulled out; the gland is then free to be removed for
repacking. In use the best method of handling is to open and close the
valve slowly—never with a jerk.
[Illustration: FIG. 640.]
_The tendency toward higher pressure_ steam boiler installation has
made apparent the need of a blow-off, like this one described,
made of strong material and correct in principle; in fact the high
steam pressures now carried have almost made a revolution in boiler
appliances.
The Fig. 640 represents two valves applied to the end of a blow-off
pipe. The valve next to the boiler is open at all times excepting
when the operating valve, next to the sewer is to be attended to for
repairs, etc.
_The table below is_ intended to correspond with the letters to be seen
in the illustration, Fig. 640.