What type of pumps are commonly used as priming pumps?

Priming pumps are designed to remove air from the pump casing and create a vacuum that allows the main pump to draw in fluid. Among the types listed, rotary gear pumps are particularly well-suited for this function. They work by using interlocking gears to move fluid, which creates a vacuum that can efficiently clear air from the lines and allow the main pump to begin operation smoothly.

Rotary gear pumps are able to maintain a constant flow rate and effectively handle the necessary suction to prime other pumps, making them a common choice in fire apparatus where reliable priming is essential for effective water delivery during emergency situations. This characteristic is vital for systems that need to operate quickly and efficiently, as is often the case in firefighting scenarios.

The other types of pumps mentioned, while useful in various applications, do not have the same efficiency or reliability in priming applications as rotary gear pumps.