Originally Posted by Matt A:
Rich - Approximately what boiler pressure were you operating at?
Maximum working pressure of the NKP 700 class was 245psi. Thus with at least one safety open, 765 would have been at no less that 246psi. Remember that the steam locomotive is essentially a heat machine, i.e. the higher the temperature of the steam entering the valves/cylinders then the higher the horsepower. It may not sound like much, but an extra one, two, or three psi boiler pressure, and the increasing steam temperature through the superheater units, would provide measurable higher temperature steam into the valves/cylinders. Thus, higher horsepower!
