12
(6).
Protector
The diameter of smokebox door and opening is to be
retained the same, provided all the tubes can be withdrawn
easily from the boiler. The smokebox door is to be of
the dished type with a small radius, to bear on an angle
ring rivetted to the smokebox front plate, and lipped on
the outer face with a small clearance for the door. The
smokebox is to be the cylindrical type, with a saddle
casting underneath fitted between the frames.
plates are to be fitted on the inside of the wrapper plate
at the bottom and up the sides as far as necessary. The
smokebox door details are shown on Drg. No.Z. 4472/33, Regn.
No. 251/1. Dogbolts as shown on the Contract Drawing are
to be fitted to the smokebox door to ensure an air-tight
fit and all round the bearing surface. A central dart and
crossbar fastening is not required.
18. Main Steam Pipes. The main steam pipes in the smokebox are
to be of solid-drawn steel, grooved and expanded into
flanges of "B" class steel, the ends of the pipes being
rivetted over in the flanges. All joints are to be made
with lens rings, of "B" class steel. Care must be taken to
see that the pipes are arranged with easy leads to the
steam-chests, and that where the pipes pass out through
the smokebox wrapper plate an air-tight joint is made, with
suitable provision for expansion and contraction of the
pipes.
19. Spark Arrester & Ash Ejector. The same type of spark
arrester is to be fitted as shown on Drg. No. 4472/35, Regn.
No. 251/1. An ash ejector, steam operated, is to be fitted
at the smokebox bottom, as shown on Drg. No.Z.4472/38, Regn.
No.251/1. It is desired to remove the ashes without opening the smokebox door, and special consideration should be
given to the design so that the jet of steam is sufficiently
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