Eductor-jet pumps are useful for draining areas which may contain volatile fluids (which could ignite if exposed to the workings of a standard electric or internal combustion engine powered pump) or high levels of debris (which could damage screws or blades in conventional pump designs).
A source of pressurized fluid (eg, a firehose) is connected to a chamber which is open on one end, and leads to an exhaust hose on the other end. The pressurized fluid is forced through nozzles (called eductor jets) mounted axially on the inside of the pump chamber, pointed in the direction of the exhaust hose. The passage of the pressurized fluid through the chamber and into the exhaust hose creates a suction on the open end of the chamber (Venturi effect), such that any fluid the pump chamber has been submerged in will be drawn into the chamber and thence into the exhaust hose along with the fluid from the eductor jet nozzles.
Some coal fired Thermal power stations may also use the jet pumps to pump out coal dust from dust hoppers to storage yards. In this case a seperate high pressure pump is used as a driving force required for the pressurised fluid at the inlet of the jet pump.
In low pressure boilers this principle is also being used for pumping chemicals to boiler feed pump suction in early days.
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