Eductor-jet pump

Eductor-jet pumps are useful for draining areas which may contain combustible fluids (which could ignite if exposed to the workings of a standard electric or internal combustion powered pump) or high levels of debris (which could damage screws or blades in conventional pump designs).

Additional recommended knowledge

Don't let static charges disrupt your weighing accuracy

Recognize and detect the effects of electrostatic charges on your balance

Better weighing performance in 6 easy steps

A source of pressurized fluid (e.g. 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.

What is an “Eductor” ?

A device that uses the energy from one fluid to create a pressure differential in a confined space. This pressure differential allows a second fluid to flow toward this lower pressure area or simply to be pumped. Either “fluid” may be a liquid, gas, or steam.

Key Terms: (Motive)

Motive: The operating or pumping fluid. The smallest connection on the eductor. Motive Pressure: Fluid pressure at the Eductor. Typically between 20 and 250 psig. Sources: Pumped liquid, city water supply, static head (water tower), air compressor, blower, steam, and waste steam.

Key Terms: (Suction) Suction: The secondary fluid that will be pumped or evacuated. Size matches the size of the unit. Suction Lift / Pressure : When pumping liquids, the distance a fluid needs to be raised is the lift. When pumping gases, a suction pressure is given, often in inches of Mercury. Values may not exceed 27’ of lift or 27” of Mercury vac.

Key Terms: (Outlet) Size matches the size of the unit. Outlet Head / Pressure: When pumping liquids, the distance a fluid needs to be moved above the eductor is the outlet head. When pumping gases, an outlet pressure is given, often in psig. Only in rare instances will the outlet be greater than 50% (25%) of the motive pressure when pumping liquids(gases).

Elements of a Reliable Eductor • Smooth flow paths designed to maximize efficiency • Scaled geometry relating size 1/2” to 12” • Consistent design and quality relates to product performing as calculated. • Mechanical integrity to eliminate additional variables that may adversely affect performance. (Full ASME Rating)

Applications: Eductors are used in a wide variety of applications • Remove water from gas wells as deep as 220’ [liquid pumping liquid application (L-L)] • Add / Remove contents to / from railroad tank cars [L-L, liquid or gas pumping gas (L-G), (G-G)] • Add gasses to purify process(H2Otreatment) [L-G} • Evacuate refrigeration system before start-up [G-G] • Add / remove water to bilge tanks shipboard [L-L] • Remove rain water/silt from sumps w/ steam or water [L-L]

Sizing: Key Elements (Pressure)

Pressure boundaries are the most important items to obtain first.

Examples: How much pressure do I have at the eductor? How far do I have to lift the fluid? How far does the fluid have to travel after leaving the eductor? What vacuum do I need to reach, maintain? What devices are after the eductor?

Sizing: Key Elements (Capacity) Next most important are the required capacities. Suction capacity is an absolute must. Motive capacity is a must only if it is a limiting factor. Capacity may be in the form of time required / desired to evacuate a vessel and hold a certain pressure.

Sizing: Key Elements (Heating) The one notable application that is more concerned with temperature than capacity, though it may still be a limiting factor, is heating. Starting temperature, BTU’s available, and desired temperature are the key elements to consider.

In-Tank (Mixing) Eductor

TLA (Tank Liquid Agitator)- designed for in-tank applications Applications: - Mixing - Blending - Solid suspension - Heating (Sparging)

The TLA is an eductor that operates on all the same principles as the in-line unit. • The difference lies in the suction, which is open to the tank fluid in which the unit is submerged instead of being a connection. • Primary use: mixing, the unit acts as a “pump application device” • TLA “pulls in” 4 gallons of liquid for every gallon of liquid supplied • Tank volume equivalent “moved” through the eductor in 20% the time of a nozzle alone.

-(c)Jacoby-Tarbox Eductors Guide. - [1]

See also

• Aspirator
• Coandă effect