During full-load shop tests under natural gas, two multistage centrifugal compressors exhibited subsynchronous vibrations. Both of them are low-flow, high-pressure, high rotational speed compressors, and are fitted with tilting pad bearings and dry gas seals. A rotating stall problem was first eliminated by a modification of the diffuser geometry. Then, aerodynamic excitations caused the rotors to operate at their stability limit, and high vibration levels were observed at the first natural frequency. A complete rotordynamics analysis was performed in order to model precisely all the fluid–structure interactions. Modifications of the rotor designs were implemented, consisting in optimizing conveniently the bearing pads, replacing the toothed labyrinth seals of the balance pistons by damping honeycomb seals, fitting them with improved shunt hole systems. In addition, the dry gas seals were found to have been damaged, due to thermal effects, and further modifications were implemented to eliminate this problem. Final full load tests demonstrated a satisfactory behavior of both centrifugal compressors.

Issue Section:
Gas Turbines: Structures and Dynamics
Topics:
Compressors, Natural gas, Rotordynamics, Stress, Testing, Bearings, Rotors, Vibration, Damping, Diffusers, Excitation, Fittings, Flow (Dynamics), Fluid structure interaction, Geometry, High pressure (Physics), Honeycomb structures, Pistons, Stability, Temperature effects
1.
American Petroleum Institute, 1995, “Centrifugal Compressors for Petroleum, Chemical and Gas Service Industries,” API Standard 617, 6th ed., Feb.
2.
American Society of Mechanical Engineers, 1974, “Compressors and Exhausters,” Power test code 10, (1965 reaffirmed 1979), ANSI PTC 10 (1974).
3.
Childs, D. W., 1993, Turbomachinery Rotordynamics, Wiley, New York.
4.
Dawes
W. N.
,
1995
, “
A Simulation of the Unsteady Interaction of a Centrifugal Impeller With Its Vaned Diffuser: Flow Analysis
,”
ASME Journal of Turbomachinery
, Vol.
117
, pp.
213
–
222
.
5.
Fatsis
A.
,
Pierret
S.
, and
Van den Braembussche
R. A.
,
1997
, “
3D Unsteady Flow and Forces in Centrifugal Impellers With Circumferential Distortion of the Outlet Static Pressure
,”
ASME Journal of Turbomachinery
, Vol.
119
, pp.
94
–
102
.
6.
Frene, J., Nicolas, D., Degueurce, B., Berthe, D., and Gaudet, M., 1990, Lubrification Hydrodynamique, Eyrolles Editions.
7.
Fulton, J. W., 1984, “The Decision to Full Load Test a High Pressure Centrifugal Compressor in Its Module Prior to Tow-Out,” presented at the IMechE Second European Congress on Fluid Machinery for Oil, Petrochemical, and Related Industries, The Hague (Netherlands), Mar.
8.
Kuzdzal, M. J., Hustak, J. F., and Sorokes, J. M., 1994, “Identification and Resolution of Aerodynamically Induced Subsynchronous Vibration During Hydrocarbon Testing of a 34,000 HP Centrifugal Compressor,” presented at the IFToMM, Fourth International Conference on Rotordynamics, Chicago (Illinois), Sep. 7–9.
9.
Lalanne, M., and Ferraris, G., 1990, Rotordynamics Prediction in Engineering, Wiley, New York.
10.
Scharrer, J. K., and Pelletti, J. M., 1995, “Gasseal™ Software Operating Manual,” Rotordynamics-Seal Research, North Islands, CA.
11.
Wachel, J. C., and Von Nimitz, W. W., 1981, “Ensuring the Reliability of Offshore Gas Compression Systems,” presented at the European Offshore Petroleum Conference and Exhibition, EUR 205.
12.
Zeidan, F. Y., Perez, R. X., and Stephenson, E. S., 1993, “The Use of Honeycomb Seals in Stabilizing Two Centrifugal Compressors,” Proc. 22nd Turbomachinery Symposium, Dallas, TX, pp. 3–15.
This content is only available via PDF.
Copyright © 1997
 by The American Society of Mechanical Engineers
You do not currently have access to this content.