Re: Air pressure to Operate Flangers/Spreaders

The flangers and Jordan spreader operated off main reservoir pressure. In the cab below the automatic brake valve is a a pair of valves plumbed from the main res. line. One is for the pilot truck flanger, the other is for the "auxiliary air line" out the back of the tender where the flanger/spreader air hose is. the hose is on the opposite side of the train line air hose to avoid confusion. The valve in the cab is a bit unique in that when closed it allows the air in the line to vent to atmosphere. The valve is a simple 1/4 turn on/off affair.
The amount of air pressure generated by the compressor is more a matter of steam pressure than anything else. FRA reg require the Main Res/ presure to a minimum of 20 pounds more than the brake pipe pressure. Greater pressure allows the brake pipe to charge at a faster rate on longer trains - certainly a plus in mountain service. Modern DRGW ng power used 125-130 pounds of Main Res. pressure.