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GEFR-SP 130
DATE April 1979
TITLE:
Minimizing Unbalance Response
of the
CRBRP Sodium Pumps
AUTHORS:
Viney Gupta and R. G. Marrujo
Prepared for presentation at:
Interaction Meeting Structural Mechanics
S
Reactor Technology
Conference
- NOTICE-
TTiis report
was
prepared
as an
accounr
of
work
sponsored
by the
Unrted Stales Government Neither
the
United States
nor the
United States Department
of
Energy,
nor any of
then employees
nor any of
their
contractors, subcontractors,
or
their employees, makes
any warranty, express
or
implied,
or
assumes
any
legal
liability
or
responsibdlty
for the
accuracy, completeness
or usefulness
of
any information, apparatus, product
or
process disclosed,
or
represents that
its use
would
not
infringe pnvately owned nghts
Held In; Berlin, Germany
City, State
on:
13/17 August 1979
Date
This article discusses work performed
under Contract
No.
5^-7A0-192908BP
and
5^-7A0-192909BP
with Westinghouse,
who
has contracted with
the U.S. DOE
under
Contract
No.
DE-AC15-76CL02335
S
Contract
No.
EV^-76-C-15-0003.
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DISCLAIMER
This report was prepared as an account of work sponsored by an
agency of the United States Government. Neither the United States
Government nor any agency Thereof, nor any of their employees,
makes any warranty, express or implied, or assumes any legal
liability or responsibility for the accuracy, completeness, or
usefulness of any information, apparatus, product, or process
disclosed, or represents that its use would not infringe privately
owned rights. Reference herein to any specific commercial product,
process, or service by trade name, trademark, manufacturer, or
otherwise does not necessarily constitute or imply its endorsement,
recommendation, or favoring by the United States Government or any
agency thereof. The views and opinions of authors expressed herein
do not necessarily state or reflect those of the United States
Government or any agency thereof.
DISCLAIMER
Portions of this document may be illegible in
electronic image products. Images are produced
from the best available original document.
MINIMIZING UNBALANCE RESPONSE OF THE CRBRP SODIUM PUMPS
V.K. Gupta
E.G.
Marruj o
Byron Jackson Pump Division
Borg-Warner Corp.
ABSTRACT
The unbalance response characteristics of the vertical pumps
for the Clinch River Breeder Reactor Plant are investigated.
Finite-element shell and beam models representative of the pump-
motor structure including the rotating assembly are developed to
assess structural stiffnesses of dominant joints as well as the
foundation support stiffness so as to exclude the danger of
resonant excitation during normal operation. Less than four mils
peak-to-peak vibration amplitude at the pump tank discharge
nozzle results from just 10% frequency separation between the
first rocking mode and the maximum operating speed of 1116 RPM,
based on 0.5% modal damping ratio and balance quality grade of
_
ISO/ANSI G2.5 for the rotating components: motor rotor, pump
shaft,
Bendix diaphragm-type flexible coupling, and centrifugal
double-suction impeller.
Several design options are explored for raising shaft
critical speed beyond 125% of maximum operating speed. NASTRAN
complex eigenvalue solution is performed to take credit for
damping in bearings to help meet this requirement. The
miti-
gating effect of increasing shaft critical speed on both un-
balance response and seismic response is evaluated. The influence
of horizontal foundation stiffness on shaft whip is demonstrated,
apart from staggering lateral modes in an effort to minimize
dynamic coupling between them; higher the stiffness, less the
shaft whip expressed as the peak lateral response along the
vertical shaft.
Parametric curves are presented illustrating the extent to
which the fundamental rocking mode frequency is influenced by the
combined rotational stiffness of the pump foundation and closure
flange assembly. The fundamental rocking mode is raised high
enough to become less sensitive to the foundation stiffness.
Acknowledgement: This work was sponsored by the U.S. De-
partment of Energy through Genera! Electric Company under Contract
No.
AC-0003.
1. Introductlon
Excessive vibration can cause structural fatigue of components in
pumps (I), helicopters (2), alrcrafts
(3,^),
rotating machinery
(5-8),
reactors
(9-12),
and foundations (13). The major source
of vibration particularly in large vertical pumps Is the rotor
unbalance. Whirling deflections of the rotating shaft due to
unbalance cause the otherwise
static pump-motor structure to vibrate laterally, most frequently
In an elliptical orbit, displacing the hot liquid sodium in the
annular space between the lower Inner structure and the pump
tank. The resulting fluid-solid interactions coupled with the
turbulent squeeze-film action In the annular region are a major-
contributor to hydrodynamic (modal) damping, 2-5% according to
some investigators
(10-12),
while the structural design Includes
oil-film tlltlng-pad bearings (I't) to dampen the transmission of
vibration from the motor rotor to its support structure.
With the objective of balancing flexible rotors, several
papers (5,15-19) In recent years have advanced new methods of
which some have approached the subject via analytical methods or
have employed equivalent geometrical considerations. Standards
for rigid and flexible rotor balancing are being developed
(20-22).
1