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THE “S-F4" PUMP GOVERNOR.
The duty of any pump governor is to control the steam pressure that operates the air pump so that the pressure in the main reservoir will not exceed a given figure. With the single-top governor that figure is invariable; but with the duplex, or double top, S-F PUMP GOVERNOR, used in the No. 6 E-T equipment and illustrated sectionally in Fig. 45, the action of the pump is so restricted as to permit a pressure being carried in the main reservoir only 20 pounds or so in excess of that in the brake pipe while the automatic brake-valve is in running or holding positions; but when the brake-valve is moved to application, or lap, positions this governor releases the pump to increase the main-reservoir pressure to the figure fixed as the maximum. To accomplish this differential regulation only one steam valve and piston are required, and these comprise the working parts of the bottom section-being exactly similar to the corresponding section of the single-top governor; but there are two tops, or regulating sections, of the S-F
NOTE.-The figure 4 has no reference to the type of valve in connection with which it is used, and is only present to indicate the size, or, rather, the size of the steam pipe in which the governor is placed. The sizes of pipe connections are referred to in fractional fourths of an inch, this being understood, and only the numerator is given. A 3-inch pump governor—that is, a governor with connections for 4-inch steam pipe — if of the S-F type, would be referred to as “S-F 3." "Hence, the “S-F4" means a one-inch governor (4-fourths).
The S-F Pump Governor
PUMP GOVERNOR, and, referring to Fig. 45, the lefthand one--called the "excess-pressure governor top”is adjusted to the lower pressure, and the right-hand one—the “high-pressure top”—is set at the pressure desired as the maximum.
The diaphragm valves in the two tops are exactly alike, are of the pin form, are not numbered specifically, but will be recognized as the long, central pins whose lower ends form the valves that now close ports b. 28 points to the diaphragm, alike in each top; 20 indicates the center piece, in particular, but generally refers to the diaphragm-valve complete—diaphragm, and valve, and centerpiece, etc. The diaphragms, 28, consist of thin discs of brass, the edges of which are tightly held by the rings 21, upon which the regulating-spring boxes seat, and are flexible toward their centers where the valve pins are located, permitting the force of the regulating springs to hold the valves down to their seats. When main-reservoir pressure in chamber a exerts a greater force against the under side of the diaphragm than the spring 19 does on top of it, the center of the diaphragm will be raised slightly, pulling the pin valve from its seat and permitting air pressure from chamber a to flow through ports b, b, to chamber b of the lower portion where it forces the piston downward, closing valve 5 which shuts off steam from the pump. At this time air will be heard blowing from
vent port c.
When the main-reservoir pressure in chamber a becomes less than the figure at which this governor top is adjusted, the superior force of regulating spring 19 bears the diaphragm center downward, reseating the pin valve, and as air supply is now cut off from chamberb, the pressure remaining therein quickly escapes through vent port c; helped by the compressed spring under the piston, steam from the boiler raises and unseats valve 5, the steam supply to the pump is resumed and main-reservoir pressure is again increased.
Boiler pressure is always under steam valve 5, and offers a high resistance to its closure; but the piston that actuates it has such a wide area exposed to air pressure that about 45 pounds per square inch on top of the piston will force the valve down against any ordinary steam pressure; therefore, it becomes the duty of the regulating portion to keep the main-reservoir pressure from flowing to chamber b until it has reached the desired amount. A stuffing-box and packing around the stem that connects the air piston to the steam valve, 5, would be impractical; the stem is turned to a neat fit through the wall of the steam chamber, but a certain amount of steam leaks around and past it, which, if permitted to collect, would result in boiler pressure under the piston that the air pressure above it could not overcome, and the governor would fail to regulate the action of the pump; waste port w allows
Details of Pump Governor
this steam leakage to escape, however, and it should be seen that the small copper pipe connecting thereto is always open, and free from dents or sharp bends.
Reference to any of the colored Piping Diagrams will be a great help in understanding the operation of this governor, and in connection therewith note that MR is the connection of the pipe from the main reservoir; the pipe from ABV leads to the automatic brakevalve; and FVP is the connection with the branch of the feed-valve pipe.
Commonly the regulating spring of the high-pressure governor top is set at 110 pounds; its operation in pump regulation has just been explained, but although main-reservoir pressure is always present in chamber a —through direct communication—it is never high enough to unseat the diaphragm valve while the automatic brake-valve is in release, running, or holding positions, for then the left-hand governor top is receiving main-reservoir pressure in its diaphragm chamber, also, and it is adjusted to stop the pump when that pressure is about 90 pounds.
In the style of duplex governor used in the ordinary automatic brake equipment, the left-hand governor top is exactly like the right-hand one, with the regulating spring adjusted at 90 pounds. But in the E-T equipment, the regulating pressure exerted upon the left-hand diaphragm valve is a combination of forces
-air, at brake-pipe pressure, and a spring, having a resistance equal to the amount of excess pressure that is to be regularly carried; to secure the air pressure a branch of feed-valve pipe (see Piping Diagrams) connects with the regulating-spring box at FVP (Fig. 45); the spring 27, under the adjustment of nut 26, and much lighter than regulating spring 19 in the highpressure top, is used, and commonly set at 20 pounds resistance. This explains why it is called the "excesspressure governor top." Chamber d under the diaphragm has a pipe connection from ABV to the automatic brake-valve, and, as previously explained in connection with the study of the brake-valve, when in release, running, and holding positions a port in the rotary valve supplies main-reservoir pressure through this pipe to the governor (chamber d); when the latter pressure becomes 90 pounds, diaphragm valve 28 is unseated and the main-reservoir pressure from chamber d flows to the lower air-chamber b, forces the piston down and closes steam valve 5 as already explained.
When the automatic brake-valve is moved to lap, service, or emergency positions, the rotary valve cuts off the flow of pressure to chamber d of the excess-pressure governor top; the supply having ceased, vent port c exhausts the pressure from the piston chamber, passages and ports, b, b, b; the piston is relieved, steam valve 5 reopens and the pump starts up. Diaphragm