Background: Electric Submersible Pumps (ESPs) are widely used in agricultural fields, petroleum, and various other industries. These pumps are mostly driven at a constant speed since an A.C. motor is normally used as the drive. However, ESPs can also be operated at various speeds by employing a Variable Frequency Drive (VFD). Several patents have been published in ESP. Normally these pumps are started with the discharge valve at its closed position in order to control the starting current. When the ESP runs at its shut-off position, it will develop a higher head and an increase in fluctuating pressure. In order to evaluate the effects of pressure fluctuation, its characteristics must be investigated. Objective: Experimentally investigate the characteristics of pressure pulsation which are generated at each stage of a multistage ESP during shut-off condition at various speeds. Methods: An ESP with five stages was selected for conducting experiments. A VFD was used for operating the ESP at five speed settings from 80 to 120 % of its rated speed. Piezoresistive transducer was placed at the delivery side of the pump to acquire the signals of unsteady pressure. The pump was operated at closed valve condition at each speed, and unsteady pressure signals due to pressure pulsation were captured. Results: Obtained results have indicated the presence of fundamental frequency pertaining to vane passing frequency and harmonics of higher frequencies. Conclusion: Study of pressure fluctuations at shut-off will help to analyze the failures of ESP due to vibration which occur when the pump runs at closed valve position for a prolonged length of time and stability of these pumps at lower flow rates.

No abstract

No abstract

No abstract

Fluctuating pressures can induce vibration in the Electric Submersible Pump (ESP) and severely affect the pump components. The installation depths of ESP systems are varying from a few meters to several hundred meters. Once installed ESPs are not accessible for diagnostic measurement and maintenance activity, so it becomes necessary to obtain detailed information of mean and fluctuating pressures to attain an optimal pressure distribution inside the pump. In this paper the results obtained from an experimental investigation of stage-wise pressure pulsation at Best Efficiency Points at various speeds are presented. Tests were conducted on a five stage ESP having impellers of 121 mm diameter and 14 mm width at outlet with impeller of 8 vanes and a diffuser-return channel of 6 vanes which delivers 7 lps (litres per second) and develop 60 m total head at various speeds. Unsteady pressure signals were captured by mounting piezoresistive transducers at each stage of ESP. Captured pressure signals were converted into frequency domain to analyze the characteristics of pressure pulsation. The results have indicated that the maximum amplitude of pressure pulsation was obtained at the highest operating speed setting of 60 Hz at stage 4. The normalized frequency at which this amplitude was maximum was highest at stage 2 at all the speeds.