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A close-up of the superheater header sitting on its temporary "test rig" with the elements attached.
For those unfamiliar with the principle of superheating, saturated steam from the regulator enters the header through the open flange in the centre. From there it is distributed to one of the 28 elements, each one of which is located in the large flue tubes in the boiler. Each element consists of 4 tubes interconnected by return bends to maximise the exposure of the steam within them to additional heat. On returning to the header, the temperature of the steam at 73129's boiler pressure of 225 psi, has been raised from around 400 to 600 degrees Fahrenheit and its volume has increased by around 35%. From the header, the superhaeated steam goes directly to the cylinders via one of the two pipes (seen blanked off in the photo until after the test) on the back of the header. The consequence of superheating is that the demand on the locomotive's boiler to supply steam to the cylinders is considerably reduced, resulting in a saving in fuel and water.
Photograph by Steve Huson
Copyright © Standard Five Fund - 2004