Page 74 - Introduction to Marine Engineering

-Steam turbines and gearing 61

by an air pump or air ejector to the gland steam condenser. Any air
which leaks in from the machinery space will also pass to the gland steam
condenser (Figure 3.9).
At very low speeds or when starting up, steam is provided from a
low-pressure supply to the inner pocket. The outer pocket operates as
before.
The gland steam sealing system provides the various low-pressure
steam supplies and extraction arrangements for all the glands in the
turbine unit.

To gland
steam
condenser

Figure 3.9 Giand steam sealing system

Diaphragms
Only impulse turbines have diaphragms. Diaphragms are circular plates
made up of two semi-circular halves. A central semi-circular hole in each
is provided for the shaft to pass through. The diaphragm fits between
the rotor wheels and is fastened into the casing. The nozzles are housed
in the diaphragm around its periphery. The central hole in the
diaphragm is arranged with projections to produce a labyrinth gland
around the shaft.

Nozzles

Nozzles serve to convert the high pressure and high energy of the steam
into a high-velocity jet of steam with a reduced pressure and energy