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.
