How Does an Eductor Work

How Does an Eductor (Jet Pump) Work ?

Eductors are a kind of jet-type pump that do not require any moving parts to be able to pump out a liquid or gas from a certain area. These pumps make use of their structure to transfer energy from one fluid to another via the Venturi effect. The structure of the pump is such that it has an injector chamber with a narrow shaped nozzle or tapered jet that is located inside the chamber and points axially towards the exhaust chamber to increase the pressure of the motive fluid as it enters the eductor. At the bottom of this nozzle is an opening that is used to suck in any form of fluid or other substance that needs to be extracted from a certain environment. The suction happens due to Venturi effect that creates a drop in pressure at the tip of the nozzle due to the fast flowing motive fluid which has gained kinetic energy due to the tapered shape of the nozzle. This difference in pressure causes the desired fluid to be sucked into the eductor and mixed into the flow stream to be guided out of the eductor.

Cutaway of Pipeline Steam Heater

The purpose of such pumps is to be used in applications that are vulnerable and could cause explosions when exposed to standard electric or internal combustion powered pumps. They also can be used for applications involving extraction of high volumes of debris. These solid debris particles could damage the screw or blades of regular conventional pumps. Therefore as eductor jet pumps do not make use of any moving components, they can be an ideal choice to extract the debris. The source of the motive fluid can be a fire hose to which the eductor can be connected to. Other forms of motive fluids can be a gas, a dust-laden gas stream or slurry.

After the motive fluid has been mixed with the substance to extract, the shape inside the eductor get narrow once again just before the exhaust hole. This narrow shape causes the kinetic energy of the fluid to drop while causing a change in the pressure. This causes a continuous motion of suction of the fluid to be extracted into the eductor. This is known as the Venturi effect and it is responsible for the operation of this device.

example of a jet pump
example of a jet pump

These pumps are able to carry out dewatering in circumstances where other pumps might not be able to function and that too at a very fast rate. Liquids that cannot be pumped using other pumps can be extracted through eductors such as liquid that may contain particles of solid or foreign matter. The portability of these pumps allows them to be used in various applications. However, an important thing to note would be that not all of the fluid that an eductor discharges comes from the compartment that is being dewatered. As the eductor may be activated by water and also by extracting water, only a certain portion of its discharge would be the distracted water as the motive fluid would have mixed with it and discharged through the exhaust. Another important thing to note is that the pressure of the motive fluid that is supplied to extract another fluid from a certain area should always be higher as compared to the fluid that has to be extracted. If this is not the case, the eductor would instead simply end up flooding the area, instead of distracting any fluid or substance.

Jet Pump Application
Jet Pump Application

Before and while utilizing these pumps, the user should ensure that the pressure of the motive fluid is higher than the fluid to be extracted; the hoses should be free of kinks, the eductor should only be charged with a motive fluid when it is fully submerged in the fluid to be extracted and keep the eductor submerged while the fluid is being extracted.

Eductors have several advantages over other types of pumps that may use electricity or fuel to pump out water. Also the fact that these pumps are portable makes them very much versatile and usable in applications where other pumps may prove useless.

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