Midland Railway Locomotives: lnwrbns_pg459
Midland Railway 2P 4-4-0 No 498 is seen standing light
engine on the middle road between Platform 5 and 6 having brought in empty
passenger stock on 29th August 1912. Built at Derby works in November 1897 No
498 was later modified by H Fowler to include superheaters and in this form ran
in service until August 1950 when it was withdrawn from Mansfield shed to be
scrapped shortly afterwards by Derby works. A superheater is a device used to
convert saturated steam into dry steam used for power generation or processes.
In locomotive use, by far the most common form of superheater is the fire-tube
type. This takes the saturated steam supplied in the dry pipe into a
superheater header mounted against the tube sheet in the smokebox.
The steam is then passed through a number of superheater
elementslong pipes which are placed inside special, widened fire tubes,
called flues. Hot combustion gases from the locomotive's fire pass through
these flues just like they do the firetubes, and as well as heating the water
they also heat the steam inside the superheater elements they flow over. The
superheater element doubles back on itself so that the heated steam can return;
most do this twice at the fire end and once at the smokebox end, so that the
steam travels a distance of four times the header's length while being heated.
The superheated steam, at the end of its journey through the elements, passes
into a separate compartment of the superheater header and then to the cylinders