Eductor Nozzle - The Motive Connection

An eductor nozzle 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.

Eductor Nozzles

Eductor Design

There are three connections common to all venturi eductors.

Eductor MOTIVE Connection: This connection (aka eductor nozzle) 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 NCI eductor 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.

Eductor Connections - Cut-a-Way

Eductor CutaWay

Converging Mixing Tube

Manufactured to specified finish and concentricity, assuring performance vastly superior to that of competitive units.

Models for Moving Solids

  • Models for Solids Transport SL ML HL ULJ SG
    Operating Media Liquid, Air Liquid, Air Liquid, Air Air Air
    Operating Pressure (psig) 5-100 5-100 3-100 15-50 20-100

Models for Pumping Liquids

Models for Pumping Liquids SL ML HL SG HG
Operating Media Liquid Liquid Liquid Steam Steam
Operating Pressure (PSIG) 15-200 15-200 15-200 30-150 20-150
Pressure Recovery % 10-15 30-35 40-50 15-20 30-35
Maximum Suction Lift 27 ft 27 ft 27 ft 20 ft 20 ft
Maximum NPSH Required 3 ft 3 ft 3 ft 13 ft 13 ft


Models for Pumping Gases

Models for Pumping Gases ML HL SG HG
Operating Media Liquid Liquid Steam, Air Steam, Air
Operating Pressure (PSIG) 20-200 15-200 30-150 20-150
Maximum Vacuum 29 in Hg 29 in Hg 24 in Hg 23 in Hg
Discharge Pressure 15 15 12 35
Applications Evacuate, Exhaust, Prime


Models for Heating Liquids

Models for Heating Liquids MLE ML MLH ULJ ULH TLA
Heating Process In-Line In-Line In-Line In-Line In-Line In-Tank
Max Temp Rise 180 200 215 200 200 125
Maximum GPM Heated 5000 5000 5000 700 700 2000
Steam Press Range Vac-45 Vac-100 Vac-120 0-150 0-150 10-140


More Productive Than Electric Pumps- With Lower Initial & Upkeep Costs

NCI Eductors offer many advantages over electric pumps. They feature design simplicity, without rapidly rotating parts that are subject to leakage, wear and breakage. Eductors are generally small in relation to the work they do, and they are low in cost. They are easy to install and require few adjustments. They are easy to inspect and clean, and never require lubrication. In addition, they are ideally suited for use in hazardous locations, without the need for explosion proofing as may be required with electrical equipment.

Advanced Design... Full ANSI Ratings

NCI Eductors feature an advanced design to assure flows better than those of other eductors. Unlike typical cast units, which meet only a nominal pressure rating, NCI Eductors meet rigorous ANSI specifications.

All of our eductors have a smooth specified finish for critical flow paths. In comparison, sections of the flow paths in competitive cast units may be left rough to keep production costs down. Also, the mixing tube section of NCI Eductors has been designed to withstand the stress to which it will be subjected. This is the point at which many other makes are weak and subject to breakage during installation. All units have wrench flats to prevent damage during installation.

Providing a smooth flow path is critical to optimum eductor perfformance. As a result of this feature, the motive fluid achieves more velocity through the eductor body, and this means more energy is used for pick-up of the suction fluid. Also, better flow paths in the diverging section of the eductor allow it to achieve better discharge pressures.