الفهرس 
INTRODUCTION AND LITERATURE REVIEWOnly 14 pages are availabe for public view
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Abstract
Unexpected pump failure is expensive and potentially catastrophic, resulting in unplanned downtime of engineering systems, costly replacement of broken parts and environmental concerns. Therefore, maintenance is the only solution to avoid such failures. There are many types of maintenance one of them is the predictive maintenance which is the main concern of the present work. Predictive maintenance is a process of monitoring of the machine condition in order to identify any deterioration, enabling maintenance to be planned according to data obtained from the vibration analysis. Vibration based condition monitoring is used to detect and diagnose machine faults and form the basis of predictive maintenance program. Vibration of rotating machinery is the most significant restriction which controls the lifetime and may cause the disastrous failure of the entire mechanical system. Therefore, vibration monitoring is the main component of any customized maintenance program to guarantee power plant availability and minimize the danger of unexpected failures. The present work is a numerical and experimental study on a small centrifugal pump running in healthy and intentionally defected conditions to show the difference in the vibration spectrum and time domain for booth cases. Tri-axial acceleration measurements are made at the shaft of the pump and presented as vibration amplitude versus time. The most dangerous case of vibration is denoted by
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the highest amplitude as well as its corresponding frequency according to many international standards (ISO). The software used in the numerical work is ANSYS CFD and STAR-CCM+. The mechanical system (pump and piping) is modeled by SOLIDWORKS. Operating and running the system under different flow rate for the pump and obtaining the vibrations on time domain represent the main goal of the numerical analysis phase of the present work. Steady-state simulation is chosen, the solver uses a threedimension incompressible Reynolds-Averaged-NavierStokes equation for a single-phase analysis which obtains the time-averaged state of the flow around the impeller. The “time-averaged” moment due to the flow acting on the impeller is obtained. The software calculates the moment around the impeller via the resolution of pressure and shear forces exerted on the impeller due to the water flow. Harmonic analyses are used to determine the steady-state response of a linear construction to loads that vary sinusoid ally (harmonically) with time, thus enabling to verify whether or not the designs will effectively overcome resonance, fatigue, and other damaging effects of forced vibrations. Numerical and experimental investigation demonstrates that the amplitude exceeds the permissible operation limit in unbalance modes, due to the system is on verge to collapse. Measurements of vibration were made on the test rig (mechanical system) which was built in British University lab in order to carry out this experimental work. This
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mechanical system was equipped with accelerometers and data acquisition system as well as the appropriate software to obtain and show the data required. Comparison between the experimental results and the numerical calculation were made. The conventional balance mode proves that when the pump impeller is broken, the frequency amplitude reached the maximum permissible values according to the number of defected blades. The most severe case is the pedestal looseness with a full flow rate which causes vibration of the amplitude of (0.104g) at a frequency (47Hz). The unacceptable vibration, as classified according to ISO 10816, is to have an amplitude of (0.5g) for small machines. Within this range of acceptable vibration, it is not difficult to predict the artificial defects made in the pump and to demonstrate the capability of condition monitoring technique as a powerful tool for predictive maintenanc