AIR COMPRESSORS 83 



Pc.No.Ref.No. Name nf Part 



2.034 17 Check-nut. 



2.035 18 Regulating nut. 



2.036 19 Regulating spring. 



2,043 20 Diaphragm, complete, includes 32 to 36, 



inclusive. 



1,064 21 Diaphragm ring. 



6,868 22 Vent-port screw. 



2,046 29 Strainer. 



5,384 30 Union swivel, f-in. O. D. copper pipe. 



15,291 31 Union nut. 



2.041 32 Diaphragm nut. 



2.039 33 Diaphragm valve. 



2.040 34 Diaphragm washer 



2.042 35 Diaphragm- valve spring. , 

 2,038 36 Diaphragm, 2 pieces, each. 



2,045 40 Union swivel, i-in. iron pipe. 



Operation of Governor. The operation of the duplex gov- 

 ernor is exactly the same as that of the S-4 governor, since only 

 one diaphragm portion operates at a time. Both the dia- 

 phragm portion and the steam portion of the duplex governor 

 are exactly the same as the corresponding parts of the improved 

 single governor. The only difference is that the duplex gov- 

 ernor is provided with the Siamese fitting and an extra dia- 

 phragm portion. This valve is merely a combination of two 

 ordinary governors, and it operates in exactly the same way 

 as the ordinary governor, since one or the other of the dia- 

 phragm bodies is always cut out. The description of the 

 improved single governor applies to this governor also. The 

 pipe connections between the duplex governor and the engi- 

 neer's brake valve are shown in Fig. 3. 



The duplex pump governor is necessary on engines equipped 

 with the high-speed brake and the high-pressure control or 

 special apparatus, for loaded freight trains, and it is also neces- 

 sary on many engines not used in this special service. It pro- 

 vides a means for carrying two pressures in the main reservoir; 

 a moderate one while running with brake released and a much 

 higher one while the brake is applied, so as to provide a high 

 excess pressure for the prompt release of the brake. This is 

 done by piping the low-pressure side of the governor to the 

 feed-valve port / in the F-6 brake valve shown, a hole being 

 drilled through the bottom case of the valve through the lower 



