Introduction to Mini-Eductors

Fox Mini-Eductors for Gas-Sampling, Liquid Mixing, Aspirating and Vacuum Generation


What are Fox Mini-Eductors?

Fox Mini-Eductors are small venturi eductors that use compressed air or water to generate suction for a variety of sampling, pumping, mixing, or vacuum-generation applications. Fox stocks a broad range of off-the-shelf mini-eductors in 316 Stainless, Teflon, CPVC, Monel, Hastelloy, and Brass that can ship in 2 days. These off-the-shelf corrosion-resistant eductors are installed in hundreds of applications ranging from venting toxic hydrazine from fuel lines on the Space Shuttle after landing to circulating refrigerants in chiller systems at start-up.
Motive gas flow rates range from 0.25 to 2 SCFM. Motive liquid flow rates range from 0.1 to 2 GPM. Fox Mini-Eductors are capable of achieving vacuum levels of -28″ Hg (1 psia or 0.07 bar abs.)

What’s in a name?

Industry uses many different names for the products we supply as Fox Mini-Eductors. A few include: aspirators, vacuum-generators, mixing tees, venturi vacuum pumps, sampling jets.

What materials are available off-the-shelf?

  • 316 Stainless Steel
  • Monel
  • Hastelloy C276
  • Teflon
  • Brass

What end connections are available?

  • NPT Threads
  • SAE – 45° flared tube fittings
  • AN/JIC – 37° flared tube fittings
  • Stub Ends of 1/4″, 3/8″, and 1/2″ OD tubing, for use with flareless tube fittings
  • Stub Ends of 6mm, 8mm, and 12mm OD tubing, for use with flareless tube fittings

How Do Fox Mini-Eductors Work?

Mini-Eductors are used in the same way as a pump in a process or system. However, instead of using electricity to drive a rotating impeller or compressor, the mini-eductor uses fluid mechanics to create suction with the energy stored in your motive fluid. This enables pumping or mixing to occur with no moving parts, and therefore with no maintenance.

How do they work? The ‘motive’ fluid available to drive the eductor (compressed air, N2, water, etc.) is discharged through a precision-machined nozzle. The resulting high velocity jet creates vacuum and can pull in another liquid or gas through the ‘suction’ port. These two fluid streams are mixed and discharged.

Gas Sampling Mini-Eductors

For decades, many of the largest global integrators of analyzer and instrumentation systems have included Fox gas sampling mini-eductors in their analyzer solutions.

For a quote on a Fox Mini-Eductor for a gas sampling application, please submit our Application Data Sheet.

Hydrogen Mini-Eductors for Fuel Cells

Fox has supplied hundreds of Hydrogen ejectors to dozens of companies in over ten countries for use in fuel cells. Please visit our Fuel Cell Ejector page for more information.

Three Fox Mini-Eductors in Fuel Cell
Three Fox mini-eductors are installed in parallel in a Hydrogen Management System of a fuel cell. The ejectors are sized at 20%, 30%, and 50% of max flow, allowing the solenoid valves to select a set of operating points that correspond to required power output.

Liquid-Driven Mini-Eductors

Liquid-driven mini-eductors are used in a huge variety of industrial applications – especially for replacing and eliminating expensive small pumps in corrosive, explosive, high purity, or toxic applications – including:

  • Gasoline, Jet fuel, Biodiesel blending
  • Removing leaked liquids – fuel, hydraulic oil, lubricants from sumps, trays, etc.
  • Acid dilution
  • Hydraulic fluid recirculation
  • Mixing chemical solutions
  • Refrigerant recirculation: R-134A, CFC’s, etc.
  • pH control solutions

In order to quote the right mini-eductor, we need you to complete a Fox Application Data Sheet and define flow rates, fluid properties, and pressures at all three connections: Motive, Suction, and Discharge. Please note that the eductor accomplishes work by compressing or pressurizing fluid from the suction port up to a higher pressure at the discharge. Discharge pressure, discharge pipe size, and discharge pipe geometry are therefore critical to performance. Discharge piping cannot be reduced after the eductor – and spray nozzles to create a high velocity jet cannot be installed downstream of a mini-eductor.

Liquids Pumping Gas – Liquid driven mini-eductors are capable of entraining small amounts of gasses, but only if the discharge pressure is below about 2 psig.

Conveying Powders with Mini-Eductors

Fox mini-eductors can be used to convey very small amounts of fine powders, over short distances, in carefully engineered systems – usually pilot or bench-top research applications. Powders must be trickle-fed or dosed by a feeder – they cannot be dumped or batch fed into such a small opening.

Customized/Optimized Mini-Eductors for Special, Prototype, or OEM Applications

Fox’s off-the-shelf mini-eductors, although ideal for hundreds of common applications, are not perfectly suited to every possible application. However, Fox can quickly deliver optimized mini-eductors, with internal dimensions modified to meet your operating conditions in just 1 – 2 weeks. Our proprietary computer models can enable us to design internal geometry per your fluids, flow rates and pressures, and then quickly modify existing stock components to assemble an optimized mini-eductor or prototype. Such internal modifications are particularly important when handling light or dense liquids, like gasoline or refrigerants; light or dense gasses, like hydrogen, natural gas, or argon; or when handling fluids at high or low temperatures.

This approach has often enabled Fox to produce, in a matter of days, what we call a B+ ‘proof of concept’ prototype, which may then lead to a uniquely-designed A+ production design. This rapid response of quickly produced prototypes, working closely with R & D and development departments has lead to Fox supplying many thousands of production mini-eductors – every year – for refrigerant systems, instrumentation, and fuel cell applications.

Not only can internal geometry be changed to suit design conditions, but additional features can be added such as two to four suction ports, mounting holes, special end connections, electropolishing, UL-approval, passivation, oxygen cleaning, etc.


This highly customized 316 ss mini-eductor began as a quick-proof-of-concept prototype, with NPT ends, that Fox supplied in 2 days using modified stock components. Successful testing then lead to supply of this electropolished mini-eductor with VCR and tube stub ends, for use in high-purity semi-conductor gas applications.


R & D Mini-eductors – To facilitate research and testing, Fox often supplies ‘R & D Eductors’ – where a set of interchangeable motive nozzles with different orifices – and hence flow rates – can be threaded into one fixed mini-eductor body. This enables trials with varying motive flow rates, eventually yielding an optimized final design.
Custom 316SS R&D Mini-Eductor with a removable motive nozzle
Cartridge Inserts – Fox supplies many mini-eductors that do not have discrete end connections. These are precision machined eductor pairs or cartridge inserts that are installed in pre-drilled holes within a customer’s manifold. Eductor inserts are sealed with O-rings. The motive, suction, and discharge passageways connecting to the eductor are machined in the valve block.
A Fox Cartridge insert venturi ejector. The outside diameter is machined to within +/-0.001″ of the machined bore in our customer’s pre-drilled manifold block. Such insert ejectors enable multiple venturi ejectors to be installed in a small assembly, which can also contain check valves and selector on/off valves.

UL Approval can be obtained for specific Fox Mini-Eductors used by specific OEM’s.

Does Fox sell through distributors?

No – all orders are placed with Fox Valve in New Jersey, USA. Call us at 973-328-1011. An order placed with a credit card can ship in 1 – 2 days. No matter where you are, FedEx, UPS or DHL can have it to you in a few days.