A vibration cavitation sensitivity parameter based on spectral and statistical methods

Cavitation is one of the main problems reducing the longevity of centrifugal pumps in industry today. If the pump operation is unable to maintain operating conditions around the best efficiency point, it can be subject to conditions that may lead to vaporisation or flashing in the pipes upstream of the pump. The implosion of these vapour bubbles in the impeller or volute causes damaging effects to the pump. A new method of vibration cavitation detection is proposed in this paper, based on adaptive octave band analysis, principal component analysis and statistical metrics. Full scale industrial pump efficiency testing data was used to determine the initial cavitation parameters for the analysis. The method was then tested using vibration measured from a number of industry pumps used in the water industry. Results were compared to knowledge known about the state of the pump, and the classification of the pump according to ISO 10816

Detection of Cavitation through Acoustic Generation in Centrifugal Pump Impeller

The most common device which transport fluid in industries, agriculture as well as domestic water supply is the centrifugal pump. Based on fluid transfer conditions, several let-downs are occur in the centrifugal pump, cavitation is one among them. The flow pattern at the eye of impeller deviates from the ideal case with the occurrence of cavitation. Due to cavitation, vibration occurs on blades that generates noise in pump. In this study, the acoustics generated in centrifugal pump impeller due to cavitation is detected with the sound pressure by using 3-Dimensional, steady and unsteady state computational fluid dynamics (CFD) analysis of an industrial centrifugal pump impeller. Harmonic force analysis with blade row model helps in finding the sound pressure. The acoustics generated with unsteady-state is compared with cavitation at steady-state CFD analysis. The Reynolds averaged Navier-Stokes equations model as well as Shear Stress Transport (SST) turbulence model are used for the CFD simulation. The results show that the sound pressure calculated increases with the increase in cavitation (i.e. formation of vapour bubbles and sudden drop in head) which shows that high noises are generated by centrifugal pump impeller at lower net positive suction head (NPSH) at a particular discharge

A Method for Automated Cavitation Detection with Adaptive Thresholds

Hydroturbine operators who wish to collect cavitation intensity data to estimate cavitation erosion rates and calculate remaining useful life (RUL) of the turbine runner face several practical challenges related to long term cavitation detection. This paper presents a novel method that addresses these challenges including: a method to create an adaptive cavitation threshold, and automation of the cavitation detection process. These two strategies result in collecting consistent cavitation intensity data. While domain knowledge and manual interpretation are used to choose an appropriate cavitation sensitivity parameter (CSP), the remainder of the process is automated using both supervised and unsupervised learning methods. A case study based on ramp-down data, taken from a production hydroturbine, is presented and validated using independently gathered survey data from the same hydroturbine. Results indicate that this fully automated process for selecting cavitation thresholds and classifying cavitation performs well when compared to manually selected thresholds. This approach provides hydroturbine operators and researchers with a clear and effective way to perform automated, long term, cavitation detection, and assessment

Optimal diagnostic set of parameters for cavitation detection in centrifugal pumps

Кавитација један од главних проблема који угрожавају рад центрифугалних пумпи, пре свега због последица које је прате: ерозија материјала, нестабилан рад, бука, вибрације итд. Познато је да кавитацијски индуковане вибрације кућишта пумпи показују карактеристичан тренд са повећањем интензитета кавитације. Експериментална истраживања урађена у оквиру дисертације, показала су да је у реалним радним условима могуће из мерног сигнала виб-рација издвојити оне параметре који указују на развој кавитације у центри-фугалним пумпама. Посебно добре резултате дала је нормирана укупна ефективна вибрацијска брзина, која је у оквиру дисертације предложена као параметар за детекцију кавитације у центрифугалним пумпама.Kavitacija jedan od glavnih problema koji ugrožavaju rad centrifugalnih pumpi, pre svega zbog posledica koje je prate: erozija materijala, nestabilan rad, buka, vibracije itd. Poznato je da kavitacijski indukovane vibracije kućišta pumpi pokazuju karakterističan trend sa povećanjem intenziteta kavitacije. Eksperimentalna istraživanja urađena u okviru disertacije, pokazala su da je u realnim radnim uslovima moguće iz mernog signala vib-racija izdvojiti one parametre koji ukazuju na razvoj kavitacije u centri-fugalnim pumpama. Posebno dobre rezultate dala je normirana ukupna efektivna vibracijska brzina, koja je u okviru disertacije predložena kao parametar za detekciju kavitacije u centrifugalnim pumpama.Cavitation is one of the main problems which could jeopardize the operation of centrifugal pumps, primarily due to its consequences: material erosion, unsteady operation, noise, vibrations, etc. It is known that cavitation induced vibrations of the pump casing shows characteristic trend with increasing cavitation intensity. Field measurements and carried out within the thesis, showed that it is possible to extract from the measured vibration signal specific parameters which points to cavitation inception and intensification in pumps. Particularly good results were obtained using normalized effective vibration velocity, which is proposed within the thesis as the parameter for the cavitation detection in centrifugal pumps