Investigation of Hydraulic Problems in Pumping Station; Case Study

Pumping stations play an important role in agriculture development projects. Performance of the pumping stations should satisfy water requirements, and management. There are many problems face these pumping stations affecting their reliability and stability. Hydraulic problems are the most important item in the field of pumping station operation and design. Motivation of this research was presence of wear and pitting impellers and casing of double suction volute casing centrifugal pumps for Ahmed Orabee Pumping Station. Vibration level, hydraulic performance test and visual inspection of impeller wear and pitting show that cavitation problem is the cause of damage. Cavitation normally occurs when liquid at a constant temperature is subjected to vapor pressure either by static or dynamic means. If the local pressure somewhere in the fluid drops to or below vapor pressure and nuclei are present, vapor cavities can be formed. As long as the local pressure stays at vapor pressure and cavity has reached a critical diameter, it will continue to grow rapidly. If the surrounding pressure is above vapor pressure, the bubbles become unstable and collapse. The collapse can be violent and is accompanied by noise, vibration and possible erosion damage to the solid surface. In this paper a field investigation for hydraulic problems in Ahmed Orabee Pumping Station is presented. The objective of the research is to determine the source of hydraulic problems and to evaluate suction side and operating conditions of the pumping units. Discharge and suction pressures, flow rates, as well as vibration level were recorded simultaneously at different conditions. The data acquisition system is used to monitor cavitation problem as a dynamic signal. The dynamic signal analysis software is used to analyze dynamic signals. The results indicated the importance of continuous monitoring suction pressure, suction intake, and assuring that no more than three pumping units to be operated simultaneously to avoid operating pumps at low efficiency region and obtain high flow rate. Also, the results indicated that, cavitation occurs in the pumping units due to inadequate physical dimension of the suction sump and suction side condition. The current suction sump is not suitable for project development with introducing more pumping units. Double suction volute casing centrifugal pumps are more sensitive to suction and inlet flow conditions than other pumps. The suction conditions according to the original sump design do not fulfill the Paper 7