Resolving Structural Vibration Issues On a Multi Stage Pump

Case StudiesThere are three multistage pumps supplied as part of a new project for transporting diesel from one location to another. Earlier, the transportation of diesel was carried out using trucks for this facility. The availability of these pumps are critical to ensure that the diesel transportation is smooth without the needing the truck services. The machine train is equipped with online vibration monitoring & protection system with online diagnostic software. During the commissioning, it was noticed that the pumps were not able to reach the maximum continuous speed of 50.7 Hz (Max rated speed is 53.8 Hz) and were tripping on high vibration at the pump casing. The operation of these pumps were limited with the speed restrictions using the Variable Frequency Drive (VFD) system. The data review from the online diagnostics system revealed that these pumps were tripping on high vibration due to the excitation of pump vane pass frequency (195 Hz), when the pump was reaching the speed of 39Hz. Further tests concluded that the pump casing natural frequency was matching with the vane pass frequency of 195 Hz. This case study is designed to outline how the high vibration issue was successfully diagnosed, the root cause for the high vibration defined and finally how the problem was mitigated using some of the structural analysis techniques (modal analysis, Operating Deflection Shape etc). Lessons learned are also discussed in view of the discovery methodology using expert system available on site, from the project point of view as well as from design point of view

Steam Whip Phenomenon in Steam turbine

Case StudiesThis case study is designed to outline how the high vibration issue was successfully diagnosed, the root cause for the high vibration found and correction actions recommended. The source of mentioned high vibration - sub synchronous excitations is steam induced instability – steam whip, detected in HP/LP turbine seals, closer to Drive End bearing. This turbine was initially equipped by Antiswirl packages. It was confirmed that this system is installed or operated not properly, non-original spare parts were installed during last overhaul

Resolving Structural Vibration Issues On a Water Flood Pump

Case Stud

Resolving Structural Vibration Issues On a Multi Stage Pump

Case StudiesThere are three multistage pumps supplied as part of a new project for transporting diesel from one location to another. Earlier, the transportation of diesel was carried out using trucks for this facility. The availability of these pumps are critical to ensure that the diesel transportation is smooth without the needing the truck services. The machine train is equipped with online vibration monitoring & protection system with online diagnostic software. During the commissioning, it was noticed that the pumps were not able to reach the maximum continuous speed of 50.7 Hz (Max rated speed is 53.8 Hz) and were tripping on high vibration at the pump casing. The operation of these pumps were limited with the speed restrictions using the Variable Frequency Drive (VFD) system. The data review from the online diagnostics system revealed that these pumps were tripping on high vibration due to the excitation of pump vane pass frequency (195 Hz), when the pump was reaching the speed of 39Hz. Further tests concluded that the pump casing natural frequency was matching with the vane pass frequency of 195 Hz. This case study is designed to outline how the high vibration issue was successfully diagnosed, the root cause for the high vibration defined and finally how the problem was mitigated using some of the structural analysis techniques (modal analysis, Operating Deflection Shape etc). Lessons learned are also discussed in view of the discovery methodology using expert system available on site, from the project point of view as well as from design point of view

Self excited torsional vibration in single shaft combined cycle turbine-generator train

Case StudyThis case history describes the investigation of the source of unstable behavior of a newly commissioned single-shaft, combined cycle, power generator unit. The source was found to be nonlinear operation of the flexible coupling between the generator and steam turbine, causing self-excited parametric torsional oscillations, transferred into radial vibration, detectable in monitoring system

How to detect Electrostatic discharge (ESD) using proximity probes on rotating machines

Case StudyIn this session, a brief introduction about electrostatic discharge phenomena will be done. Then three historical cases with Electrostatic Discharge (ESD) issue will be analyzed in order to explain how to detect Electrostatic Discharge using proximity probes. It will point out that the vibration behavior in case of ESD is not always the same

Gas Turbine With Rotor Crack Vibration Diagnostics

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Case Study on Resolving Cyclic Vibration on an Instrument Air Compressor Train

Case StudyInstrument Air Compressors are considered critical equipment in the plants, supplying compressed air to the instrumentations in the field. This case study focuses on cyclic vibration phenomena observed in the 2nd and 3rd stages of an Instrument Air Compressor, part of an Integral Gear Compressor train driven by a motor. The machine train is equipped with an online vibration monitoring and protection system with online diagnosis software, which was used to diagnose the phenomena & forward path for the resolution

COMPRESSOR ROTOR CRACK CASE

Technical BriefsThe case study describes rotor crack detection using vibration measurements, documented on real case of Induction Motor driven Compressor Unit. The study highlights the complexity of rotor crack diagnostics as the primary problem as it can be often masked by other existing machine malfunctions. In this case indication of the possible rotor crack, led to the Compressor bundle removal and rotor inspection. The rotor problem was confirmed, but not due to rotor crack but luckily only due to rotor thrust collar fit found to be worn and locating pin to be bent. Thrust collar had become eccentric (radial run out measured) causing a mass unbalance on the rotor in one direction, with similar symptoms as rotor crack. The gradual radial vibration increase on the compressor NDE bearing was observed on an export gas Compressor and the increase continued for several weeks. The vibrations were purely synchronous (1X) with a constant unidirectional phase angle. Following transient data comparisons, Lube Oil supply temperature checks, compressor feet / bearing housing vibration measurements and a NDE bearing inspection (no findings) the BN team diagnosed a rotor issue and insisted the compressor rotor was inspected. BN remotely witnessed the compressor inspection where it was discovered the thrust collar to rotor fit was worn and oversized, antirotating pin bended, causing the thrust collar to be eccentric resulting in an unbalance. This was proven on the high-speed balancing machine when the thrust collar eccentricity values could then be correlated with the rotor vibration response using an influence vector from installing a test weight at the thrust collar. Following the initial diagnosis and continued monitoring by the BN SSA team the machine was able to be safely operated for 6 months allowing for a replacement compressor bundle to be prepared and installed minimizing the operational and business impact

High Vibration Due to Steam Turbine Deposits

Case StudyThis presentation provides a case study how to correctly deal with increased vibration on a steam turbine that drives a compressor. After the machine had not operated for a week, vibration level increased 5 times during its re-startup. The vibration was dominantly composed of 1X component. An in-depth review of vibration data as well as possible root-causes is demonstrated, to rule out some possible malfunctions. Balancing would be a quick fix to let this machine back in service, based on vibration data. What actions should we take, and is balancing would work in this case