MARC Steam Turbines The Modular Steam Turbine Generation

Turbine module
In industrial turbines, part of the steam
often is extracted for production purposes,
heating steam systems or generative
feed water heating. In that case,
in addition to several bleedings, two
controlled extractions can also be provided.
The MARC concept allows an
individual and optimized design of the
different turbine elements, according to
specific requirements, such as the pressure
level and the extraction steam
quantity.
Depending on the live steam conditions
and the specified operation mode, either
a nozzle group control with or without
bypass or a throttle control may be se-
8
lected. The control stage, either single
or two-row type, and the number of reaction
stages are especially adapted to
the specific requirements. For all reaction
stages the low-loss round-head
profile is used.
The HP blades are provided with milled
shrouds, whereas the last blade rows
are mostly designed with conically twisted
blades, the blade ends of which
being tip-thinned on one side.The rotor
blades of the last rows are grouped by
means of damping and bind-ing wires in
conformity with the results of vibration
calculations. Due to the small flow
volume, steam admission of the im-
pulse wheel is only necessary in the
upper casing half, how-ever, the lower
half can also be utilized, if required. In
that case, a bypass leads to the lower
nozzle group.
The exhaust casing is a welded construction
and may either be fitted facing
upward or downward, depending on
the site conditions. MARC steam turbines
have been designed for highest
operating security and utmost reliability.
As the highest thermal impact on the
steam carrying parts occurs at load
changes, the casing, guide blade carrier
and inner casing have been developed
for a high thermal elasticity.