The back pressure produced by a control valve (or throttling valve) imposes a variable amount of loss on the system. The difference between the head developed by the pump and the head required by the system head curve is usually lost energy. Many pumps use control valves at their discharge for control and operation. Therefore, throttling is the only practical method of regulating the flow and head. Most small or medium centrifugal pumps are driven by constant-speed electric motors. The shutoff pressure determines the pressure rating of downstream equipment and piping, particularly the rating of flanges and vessels, and the class of piping required. This metric is important for downstream facilities as it is the maximum pressure that can be experienced downstream. It is the pressure at the left side of the performance curve equivalent to a near zero flow rate. It is the maximum pressure a pump can produce. Shutoff pressure (shutoff head) is also important. Large multistage pumps may deviate from their theoretical curves. The actual pump performance curve should be obtained during a performance test (at the shop or on site). Note that many pump curves are purely theoretical.

A different set of curves for the same casing and impeller are for different speed. The bottom curve shows the smallest diameter impeller for that pump casing. This has the highest head pressure of any of impellers. The top curve is for the largest diameter impeller that can be used in the pump casing. flow rate (capacity).There are usually several sets of curves for each pump model for various impellers and speeds. These curves show the head (pressure) vs. Pump manufacturers have different performance curves for each standard pump. Most should have a positive inlet pressure to prevent cavitation, which is caused by lack of enough positive inlet pressure to prevent liquid vaporization. But in some applications, special requirements such as low weight, compact configuration, and low net positive suction head (NPSH) might result in the selection of vertical pumps.Ĭentrifugal pumps usually receive less attention than they deserve. Horizontal pumps are usually more desirable than vertical pump configurations.

They are usually drive by electric motors although steam turbine-driven centrifugal pumps have been used in certain applications. Courtesy of Sulzer.Ĭentrifugal pumps are widely used in plants and facilities. Centrifugal pumps are widely used in industrial and oil & gas applications.

Sulzer pump selection tool