Jet Pumps for Gases

Jet Pumps for Gases
Jet Pumps for Gases

NCI jet pumps for gases can use Steam, Air or Liquid as the operating medium.  Typical applications include: (A) Jet Pumps for gases (Exhausting): This application involves removing gases at a continuous rate from an area while maintaining the pressure at a stable level. These applications often involve removing gases or fumes that are continuously recurring. An example would be removing smoke from a welding or machining area. This process also could be used for injecting oxygen into a liquid stream. If the gases being removed have undesirable characteristics, it is possible in some cases to neutralize them by using a reactive motive fluid. (B) Jet Pumps for gases (Evacuation): This application involves pulling gases (using jet pumps) from a defined volume by pumping the tank down from a starting pressure to a final lower pressure. It is generally sized by determining the amount of time it takes to reduce the pressure in the vessel to the desired final pressure. Examples of this application would be reducing the pressure in a reaction vessel to purge it of detrimental gases, or removing steam from a vessel before opening it to increase operator safety. A variation of this type of application is the use of eductors to prime piping or a system with liquid. Priming evacuations may be used to bring the level of liquid up to pump level to avoid the pump being started dry or to establish a siphon.


  • Improved suction flow and discharge pressure capabilities
  • Designed for gas handling and evacuation applications
  • Low cost solution for general vacuum service
  • Utilize steam or air as a motive force to create vacuum levels to 5 in Hg Abs
  • Enhanced Performance
  • Investment Cast Body (available)
  • Standard Material 316 SST
  • NPT Connections
  • Special Sizes with Fabricated Construction
  • PVC Construction Available


NCI jet pumps (eductors) operate on the basic principles of flow dynamics. This involves taking a high pressure motive stream and accelerating it through a tapered nozzle to increase the velocity of the fluid. Gas Motives are compressible fluids and are put through a converging-diverging nozzle. The gas can exceed the speed of sound. This fluid is then carried on through a secondary chamber where the friction between the molecules of it and a secondary gas (generally referred to as the suction fluid) causes this secondary gas to be pumped. These fluids are intimately mixed together and discharged from the eductor.

NCI (uniquely) has more than 50 years of experience with jet pumps and in tank mixing applications.  Our tank mixing experience covers both tank mixing eductors and propeller type side entry mixers involving tanks in sizes up to one million barrel (42 million gallons) capacity.

related: how does an eductor work?

Cutaway of Pipeline Steam Heater


There are three connections common to all NCI jet pumps (venturi eductors).

MOTIVE Connection: This connection is where the power for the eductor is generated, by increasing the velocity of the motive fluid. The eductor nozzle in this section takes advantage of the physical properties of the motive fluid. Eductors with liquid motives use a converging nozzle as liquids are not generally compressible. Eductors with gas motives utilize converging-diverging nozzles to achieve maximum benefit from the compressibility of the gas. All nozzles for eductors have smooth flow paths. Flow paths with sudden steps or roughness on these high velocity surfaces cause jet pumps to operate less efficiently.

SUCTION Connection: This connection of the eductor is where the pumping action of the eductor takes place. The motive fluid passes through the suction chamber, entraining the suction fluid as it passes. The friction between the fluids causes the chamber to be evacuated. This allows pressure in the suction vessel to push additional fluid into the suction connection of the jet pump. The high velocity of the motive stream in this section of the eductor directs the combined fluids toward the outlet section of the eductor.

Discharge Connection: As the motive fluid entrains the suction fluid, part of the kinetic energy of the motive fluid is imparted to the suction fluid. This allows the resulting mixture to discharge at an intermediate pressure. The percentage of the motive pressure that can be recovered is dependent upon the ratio of motive flow to suction flow and the amount of suction pressure pulled on the suction port. The mixture then passes through the diverging taper that converts the kinetic energy back to pressure. The combined fluid then leaves the outlet.

General Performance Table

Jet Pumps for Gas

Using Air, Liquid or Steam as Operating Medium
ModelModel ML/LMModel MLE/ELLModel SG/GLModel GH/HG
Operating mediumLiquidLiquidSteam, AirSteam, Air
Operating medium pressure range20-250 PSIG20-250 PSIG60-120 PSIG20-80 PSIG
Maximum Vacuum 29 IN. HG.29 IN. HG.24 IN. HG.24 IN. HG.
Outlet Pressure (PSIG)20201220


Jet Pumps for Steam

Using Steam as Operating Medium
Discharge Head LevelLowHigh
Operating Steam Pressure Range60-150 PSIG35-150 PSIG
Oper. Steam Press. to Elevate Liquid 50 FT.150 PSIG75 PSIG
Suction Lift (with Water Temp to 120°F)to 20 20 FT.
Minimum NPSH13 FT.13 FT.

Total customer satisfaction comes from the combination of quality products purchased at a reasonable price and delivery quickly and when promised.

Jet Pumps are in stock from 1/2″ up to 3″ sizes.  Jet Pumps are stocked in Carbon Steel, 316SS and Bronze. Tanks Eductors are stocked in sizes from 3/8″ up to 3″ in both Carbon Steel and 316SS.   We stock PPL & PVDF materials in sizes from 1/4″ thru 1-1/2″.