I.

Abstract

In this laboratory experiment the group was to develop an understanding of centrifugal pump performance characteristics, determine the centrifugal pumps’ performance curve, understand the concept of finding a duty point for a fluid delivery system, and understand the concept of a net positive suction head. The group also learned to operate the pump and record data manually and electronically.
Members of the group measured the locations and distances of lengths of pipe between the reservoir, the pump, the fittings, and the level of the water surface in the reservoir. They also noted the types and sizes of pipes and fittings. The group leader used the information to draw a schematic diagram of the system using Microsoft Visio. The diagram was used to make several calculations outside of the laboratory.
The group first operated the pump at a motor speed of 1750 rpm. The position of the control valve of the pump system was adjust using the computer control system at openings of 0,
20, 40, 50, 60, 80, and 100% flow. At each of the selected control points the following data was recorded: pump discharge and inlet pressures, flow rate measured by the orifice plate of the control system, flow rate determined by gravimetric measurement, rpm and torque of the motor, and the level of water surface in the reservoir tank. After data was collected at these settings the motor speed was increased to 2700 rpm and the process was repeated. The group used this data to obtain a pump curve at each speed. Next, the group kept the valve opening set at 50% open and varied the pump speed at 1000, 1500, 2000, 2500, and 2700 rpm. At each of these settings the aforementioned data was collected in order for the group to measure a system curve.
Data was collected and used to calculate hydraulic power, actual power, pump efficiency, and NPSH. This and other data was used for calculations to plot pump curves and system curves, which in turn was used to predict duty points for the system.
Analyzing the data brought the conclusion that the pump performed at greater efficiency at the lower speed setting, even though the measured pump head loss was consistently higher at the greater motor speed. This trend was anticipated as the difference between torque and motor speed in the trials made the 2700 rpm curve lower in efficiency than the larger pressure differential at 2700 rpm raised the efficiency. The points where required pump head and available head, or duty points, were estimated to be located at 0.0005 m3 and 5.5 m of pump head for the 1750 rpm setting and at 0.006 m3 and 10.5 m of pump head for the 2700 rpm setting.
Cavitation was not observed during the operation of the pump and uncertainty was calculated and noted for discussion of results.
.

II.

Introduction
Pumps are used in every industrial process, whether being used in the synthesis of

chemicals or the treatment of wastewater. Pumps are also used in the civilian life to do everyday things like moving water out of a flood basement. Any way you look at it pumps are incredibly important to daily life. What is more important than the pump itself is making sure the pump is working at peak performance. Pump performance can be stated simply as checking that the pump is working as efficiently as possible. Another part of the performance of a pump is to make sure that cavitation is not occurring. Cavitation occurs when a combination of the pump moving very fast and the pressure drop at the end of the fins inside the pump results in the liquid being pumped to boil, which in turn contributes to erosion of the pump. This is a serious problem that can cause mechanical failure of the pump if gone unchecked. The occurrence of cavitation can be monitored by the magnitude of Net Positive Suction Head (NPSH). The NPSH measures how much pressure is required to cause cavitation in a specific liquid (NPSHR) and how much pressure is being applied to the liquid by the pump to show how close the (NPSHA)