A category of pumps suitable for applications where a large amount of liquid is transferred.

Such devices have the following characteristics.

• Low self-priming ability (priming required)
• Excellent ability to transfer large amounts of liquid continuously
• Because non-positive displacement pumps are greatly influenced by pressure at the discharge destination and the head, their metering characteristics (ability to deliver a fixed amount of liquid in a fixed time) are less than positive displacement pumps.

The principle behind non-positive displacement pumps is the conversion of the kinetic energy of a rotating device into kinetic energy in the transferred liquid, which is then converted into potential energy that includes liquid pressure energy.

As with centrifugal pumps, the transferred liquid is continuous inside the pump, and the lack of a partition results in backflow from the discharge side to the suction side when the pump stops. On the other hand, high-speed operation is possible because there is no sliding of partitions or the like, and efficiency is very high.