BB71 and BB72 (5.6m2 and 6.9m2)
LP Turbine Modernization
Scope of supply
When it’s time to modernize your
steam turbine, we know that improving
performance at the highest reliability is
the top priority. The Siemens BB71 and
BB72 modernization is designed to meet
this goal. Our fully integrated, monoblock
rotor uses an advanced design blade path
with an increased annulus area to help
increase your plant’s output.
The Siemens BB71 and BB72 LP
Turbine modernizations are based on a
common, proven design. The replacement
LP ­turbines for both the BB71 and BB72
share the same design features, but vary in
blade sizing and staging. The modernized
turbines are designated by their nominal
annulus exhaust areas: BB71 exhaust area
measures 5.6m2, and the BB72 exhaust
area measures 6.9m2.
Both LP designs feature:
Fully integral, monoblock rotor
Free-standing design L-0 rotating blades
with a nominal 29.5” and 32” blade
height and standard side-entry roots
of the robust Siemens design. Blade
roots are 2 to 3 times larger than
original LP turbine blades
Drum stages with rotating blades that
are integrally shrouded
Optimized exhaust flow guides
Bladepath seals on integral shrouds
are a tip-to-tip design for improved
efficiency and long-term thermal
performance
Fabricated single-piece inner cylinder
(two halves) designed for easier
installation and maintenance.
Please note the 5.6m2 modernized turbine
also applies to the BB271, BB371 and
Performance Enhancement - Steam Turbine
Answers for energy.
Typical LP turbine modernization
BB471 variants, and the 6.9m2
modernized turbine also applies to
prior BB72 and BB272 variants.
Customer benefits
The modernization of your LP turbine can
be one of the most cost effective ways
to improve the long-term performance
of your steam turbine plant and to help
reduce maintenance costs.
Benefits of the 5.6m2 and 6.9m2 LP turbine
modernizations can include:
Increased output
Improved efficiency
Improved integrity and reliability
Improved long-term thermal
performance
Reduced maintenance costs
100,000 equivalent operating hours
(EOH) outage inspection interval
Optimal installation time
Improved resistance to stress corrosion
cracking and high-cycle fatigue
Potential to increase system output
without increasing emissions.
Features
Bladed LP rotor
The Siemens advanced monoblock rotor
is manufactured from a single forging
with no thru-bore. This design significantly
reduces rotor body stresses, and boresonic
exams are no longer required. Material
selection and detailed design features help
avoid stress corrosion cracking that may
be found on other LP rotor designs in fossil
applications.
New, single-piece inner cylinder
fabrication
The single-piece LP inner cylinder is constructed of a combination carbon steel
casting and steel plate fabrication split at
the horizontal joint. The improved cylinder
was designed with the latest finite element
tools to help improve reliability and reduce
maintenance costs.
Advanced technology blading
Optimized 3-D rotating and stationary
blading with enhanced sealing
Fully integrated monoblock rotor features an advanced design blade path with
increased annulus area.
Additional features
Integrally shrouded, high-efficiency
blading in the front-end stages/drum
stages
Reduced exhaust losses
Free-standing 29.5” and 32” last stage
blades, giving an exhaust area of
approximately 5.6m2 and 6.9m2
respectively
Compatible with existing rotor train to
ensure system integration.
Leading edges of the LP free-standing
rotating blades are flame or laser
hardened to help reduce moisture
erosion.
8.7” HgA exhaust pressure limits at high
loads
Moisture removal features incorporated
in the design to minimize erosion.
This improved design has been
successfully installed and is in operation.
For more information, please contact
your local Siemens representative.
Published by and copyright © 2010:
Siemens AG
Energy Sector
Freyeslebenstrasse 1
91058 Erlangen, Germany
Siemens Energy, Inc.
4400 Alafaya Trail
Orlando, FL 32826-2399, USA
www.siemens.com/energy
For more information, contact our
Customer Support Center.
Phone: +49 180/524 70 00
Fax:
+49 180/524 24 71
(Charges depending on provider)
E-mail: support.energy@siemens.com
Energy Service Division
Order No. E50001-D520-A257-X-76US
Printed in USA
BU 2009917132620872F IN 0110.2
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Trademarks mentioned in this document are
the property of Siemens AG, its affiliates, or
their respective owners.
Subject to change without prior notice.
The information in this document contains
general descriptions of the technical options
available, which may not apply in all cases.
The required technical options should therefore
be specified in the contract.