Jet pump (eductor)

A jet pump, or eductor, has no moving parts: a high-pressure driving fluid passes through a nozzle, and the resulting low pressure at the throat draws in and entrains a second fluid, which the diffuser then discharges. On ships, sea water or cargo from a centrifugal pump drives the eductor to strip the last residue from cargo tanks, ballast tanks, or bilge wells, where a normal pump would lose suction and cavitate. Efficiency is low, around 20 to 30 percent, but the device tolerates air, slurry, and a dry suction without damage, which is why it is the standard stripping tool. The driving pressure sets the suction lift it can hold.