Page 36 - Uninterruptible Power Supplies

Standby Power Generating Sets
34 Chapter One

The openings should be protected by a wire mesh to prevent the
entry of birds or other wild life; if the mesh is on the outside of the lou-
vers, birds are prevented from nesting and, if the openings are at street
level, persons passing by are prevented from depositing litter within
them.
The pressure drops across the inlet and outlet louvers must be taken
into account when calculating the fan duties, if acoustic louvers are fit-
ted the pressure drops will be higher and the effect on the fan duties
will be greater.

Exhaust Systems
Gas Turbines
It has already been stated that the layout of gas turbines is constrained
by the design of the air inlet and exhaust outlet arrangements. Gas tur-
bines discharge their exhaust to atmosphere; there is no system of
exhaust pipework and silencers as there is with diesel engines. The
requirements of the Clean Air Act do not apply to gas turbines, which
require special consideration by the local authority.
For these reasons the remainder of this section applies only to diesel
engine exhaust systems.

Within the Diesel Engine Room
Pipe work will be fixed within the engine room to carry the exhaust
gases from the engine outlet flange, through the wall or ceiling, to the
outside of the building. The pipe work is fixed to the building structure,
either from hangers fixed to the walls or ceiling or supported from the
floor; to allow for the inevitable movement of the engine on its vibra-
tion dampers, a flexible section of pipe is provided between the engine
outlet flange and the fixed pipe work. Where the pipe passes through
walls or ceilings, precautions should be taken to avoid cracking of the
structure due to heat and vibration. A sleeve or wall plates with clear-
ance holes should be considered.
The exhaust gas temperature at the engine outlet will be of the order
of 600°C and the exhaust pipe work will be subject to thermal expan-
sion. Expansion is usually permitted by incorporating stainless steel
bellows type couplings in pipe runs. Wherever the pipe is within reach
of personnel, inside or outside of the engine room, it is a source of dan-
ger and must be thermally insulated to reduce the surface temperature
to a safe value. To reduce the heat radiated within the engine room the
entire internal exhaust system may be thermally lagged, this also
reduces the noise transmitted to the room. Both these features make
the working environment more tolerable.

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