Page 14 - Steam Turbines Design, Applications, and Rerating

Preface

In order to efficiently and reliably drive compressors and other fluid
movers, virtually every industry depends on steam turbine drivers.The
various types of fluid movers often require variable input speeds, and
steam turbines are capable of providing these without too much diffi-
culty.
Situations may arise using applications during which a process
plant needs large quantities of heat. The modern mechanical drive
steam turbine proves capable of adding to plant efficiency by allowing
the motive steam to first expand through a series of blades and then be
used in the process of heating elsewhere in the plant, or as utility
steam for heating buildings on-site or in the community.
The economy and feasibility of these and a multitude of related
applications depend on the reliability of steam turbines. There is also a
strong dependency on the capability of the selected models and geome-
tries of steam turbines to handle a given steam condition at the desired
throughput or output capacity.
Similar considerations will prompt the engineer to survey the field
of available drivers for process and/or utility duty. We note that in
most large, complex petrochemical plants, particularly plants where
steam is either generated or consumed by the process, mechanical
drive steam turbines have been the prime mover of choice. These large
variable-speed units are a critical component in continuous-flow chem-
ical processes and, in most cases, are placed in service without backup
capability. This kind of application demands the highest reliability and
availability performance. These two requirements form the corner-
stone of the development programs under way at the design and man-
ufacturing facilities of the world’s leading equipment producers.
More than ever before, petrochemical and other industries are facing
intense global competition, which in turn has created a need for lower-
cost equipment. Global competition has also created a demand for the
modification of existing steam turbines to gain efficiency, that is, an

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