A. When the automatic brake valve is in any one of its first three positions; namely, release, running and holding positions.
6. Q. With the automatic brake valve in release, running or holding position, what pressure is in chamber "f" above the diaphragm? In chamber "d" below the diaphragm?
Fig. 1: The SF-4 Compressor Governor.
Connections: FVP, Feed Valve Pipe. ABV, Automatic Brake Valve. MR, Main Reservoir. B, From Boiler. P, To Air Pump.
A. Air, at feed valve pipe pressure, enters at the connection marked "FVP" and flows to chamber "f" above the diaphragm; this pressure acts in conjunction with the regulating spring 27 in creating the total pressure on the diaphragm. Air at main reservoir pressure flows through the automatic brake valve to the connection marked "ABV" to chamber "d" under the diaphragm.
7. Q. At what pressure is the regulating spring in the excess pressure head adjusted?
A. Usually twenty pounds.
8. Q. With the spring adjusted at twenty pounds, what will be the total pressure on the upper side of the diaphragm?
A. Twenty pounds, plus the pressure in the feed valve pipe.