What are eductors (jet pumps)?
Eductors, also known as jet pumps, Venturi pumps, or ejectors, are reliable fluid-handling devices that convert motive fluid energy (from liquid, steam, or compressed air) into a high-velocity jet. This jet entrains and moves a second fluid, gas, slurry, or even solids — all without any moving parts.
How does an eductor work?
An eductor operates on the Venturi effect and fluid dynamics principles. High-pressure motive fluid accelerates through a nozzle, creating a low-pressure zone that draws in (entrains) the suction fluid or gas. The two streams mix in the throat and diffuser, recovering pressure to discharge at an intermediate level. No moving parts are involved — just motive inlet, suction, and discharge connections.
Why choose eductors over conventional pumps?
They offer extreme reliability (no shafts, seals, bearings, impellers, or mechanical failure modes), minimal maintenance (no lubrication, alignment, or rotating wear parts, resulting in very low lifetime costs), simple installation (no foundations, motors, or couplings — just piping), and versatility (self-priming; handle liquids, vapors, gases, slurries, solids, corrosives, abrasives, or hazardous fluids).
What are eductors used for in liquid pumping applications?
They provide dependable pumping for condensate recovery, sumps and pits, wells and tanks, circulation loops, and transferring corrosive, abrasive, or hot liquids — especially where conventional pumps fail due to priming problems, solids handling, vapor lock, or reliability issues.
How do eductors handle gases and vapors?
Using liquid, steam, or compressed air as motive, they evacuate tanks/vessels, purge piping/chambers, remove vapors, prime liquid systems, and create controlled vacuum. They tolerate condensables, corrosives, and particulate-laden gases without losing reliability (unlike many mechanical vacuum pumps).
What are eductors used for in heating and circulation?
Steam jet heaters and liquid eductors enable in-line water heating, tank heating, pasteurization, sterilization, and cleaning-solution circulation. They deliver fast heat transfer, uniform temperature, and zero moving parts, making them ideal for process and sanitation applications.
How do eductors handle mixing, blending, and solids?
Jet pumps and tank eductors blend chemicals into liquid streams, mix granular solids into liquids, circulate tank contents, and move powders/granules (using air or steam). They enable simultaneous pumping and mixing, often eliminating the need for separate agitators or mechanical mixers.
What are tank mixing and heating eductors, and what advantages do they offer?
These specialized eductors circulate tank contents using fluid energy (no rotating blades). Benefits include full-tank mixing with no dead zones, uniform temperature distribution, no mechanical seals or motors inside the tank, and availability in polypropylene/PVDF (for corrosives), 316 stainless steel, or sanitary designs (for food, pharma, biotech). Ideal for chemical tanks, cleaning baths, plating lines, and process vessels.
What materials, sizes, and availability are offered?
Stocked in carbon steel, bronze, and 316 stainless steel; specialty alloys like Hastelloy® and Alloy 20 for demanding services. Standard sizes from ½″ to 3″ are typically available for same-day shipment.
How is the right eductor selected/sized?
Selection uses engineering-driven methods considering motive pressure/flow, suction lift/NPSH, discharge backpressure, fluid density, temperature, vapor pressure, and gas composition (when applicable). This ensures real-world performance in your specific application, not just theoretical matches.
1. Liquid-Motive Eductor for Pumping Liquid (General Sizing Factor Method)
For liquid motive (e.g., water or process liquid) pumping another liquid:
- Use performance tables based on a standard 1½″ eductor as reference.
- Calculate a Sizing Factor (S.F.) = Desired capacity / Tabulated capacity for the reference size.
- Select the eductor size whose S.F. meets or exceeds the calculated value, then determine motive consumption from tables.
- Example sizing factor table (typical values for scaling from 1½″ reference unit, water at ~68°F):
| Eductor Size | Typical Sizing Factor (S.F.) |
|---|---|
| ¾″ | ~0.25 |
| 1″ | ~0.40 |
| 1¼″ | ~0.60 |
| 1½″ | 1.00 (reference) |
Steps involve gathering data for motive liquid, suction liquid, and outlet conditions (pressures, flows, NPSH), then applying the catalog’s 5-step procedure using unified performance maps/tables. No specific flow/pressure numerical example is quoted, but suction lift can reach up to 27 ft with minimum NPSH as low as 3 ft.
General performance categories for liquid-motive liquid jet pumps:
- Low discharge head models (SL/LL): Optimized for higher entrainment ratios.
- Medium (ML/LM).
- High (HL/LH).
Motive pressure typically 15–200 PSIG.
2. Liquid-Motive Eductor for Exhausting Gases (Quick Sanity Check Example)
For evacuating/exhausting air or gases using liquid motive:
- Key inputs: Suction pressure (Psuction, e.g., vacuum level in psia or inHg), gas temperature, discharge pressure (often atmospheric, 14.7 psia), required gas flow (SCFM).
- Convert SCFM to actual cubic feet per minute (ACFM) at suction conditions to get true ingestion volume.
- Use performance tables/curves to find tabulated suction flow, then compute sizing factor and select unit.
Quick example from the site (illustrating the process):
- Required: 200 SCFM of air at 10 psia suction pressure, 80°F, discharging to atmosphere (14.7 psia).
- Convert to ACFM at suction conditions: ~305 ACFM (the eductor must handle this actual volume, not just the standard 200 SCFM).
- Proceed to tables to find the eductor size that can ingest ≥305 ACFM at those conditions, then check motive liquid requirements.
Workflow includes defining the 3 pressures (suction, motive, discharge), gas properties, and possibly staging multiple units for varying demand.
3. Tank Heating Eductor (Steam Motive) – Performance Chart Example
For steam jet heaters/tank heating eductors (gallons heated per minute, GHPM, based on temperature rise and steam pressure):
- Example from TLM performance chart (partial excerpt for a common size):
| Size | Temp Rise °F | 20 PSIG | 40 PSIG | 60 PSIG | 80 PSIG | 100 PSIG | 120 PSIG | 140 PSIG |
|---|---|---|---|---|---|---|---|---|
| 3/8″ | 10 | 24 | 37 | 51 | 64 | 77 | 90 | 103 |
| 3/8″ | 20 | 12 | 19 | 25 | 32 | 38 | 45 | 51 |
| 3/8″ | 40 | 6 | 9 | 13 | 16 | 19 | 22 | 26 |
| 3/8″ | 80 | 3 | 5 | 8 | 8 | 10 | 11 | 13 |
- Higher steam pressure increases heating capacity; larger sizes scale up accordingly.
- Avoid exceeding limits where uncondensed steam evolves (e.g., excessive temperature rise).
Additional Notes
- Tank mixing eductors: Sizing requires tank shape/dimensions, purpose (blending, solids suspension, heating), contents (specific gravity/viscosity), operation (batch/continuous), and blend cycle time (e.g., three turnovers). Location is as critical as size.
- Stock sizes: ½″ to 3″ for jet pumps (carbon steel, 316SS, bronze); tank eductors from ¼″/⅜″ up in various materials (including plastic like polypropylene/PVDF).
- For best efficiency: Motive pressure often 20–70 PSIG for tank eductors.
- No moving parts mean low maintenance, but correct sizing ensures performance without issues like cavitation or low entrainment.
Tank mixing eductors (often Model TLM series or similar, including plastic versions in polypropylene/PVDF) use fluid energy (typically liquid motive from a pump recirculating tank contents or an external source) to circulate and mix tank contents without moving parts. They provide full-tank mixing, no dead zones, uniform temperature (if heating is involved), and high entrainment ratios.
Sizing is engineering-driven and not purely formulaic on the site — we stress submitting details via our Tank Eductor Sizing Request Form (available at https://eductors.net/tank-eductor-application-sheet/) for a tailored recommendation, including model, size, price, and availability. However, the site provides key guidelines, performance tables, rules of thumb, and required inputs.
Key Required Inputs for Sizing (from Jet Pump Sizing and Tank Eductor Pages)
To properly size tank mixing eductors, provide:
- Tank shape: Cylindrical (preferred), rectangular (less ideal for side-entry setups), bottom style (flat, dished, etc.).
- Tank dimensions: Diameter/width/length and height (to calculate volume and determine circulation patterns).
- Tank volume: In gallons or cubic feet (critical for turnover calculations).
- Purpose: Blending liquids, solids suspension (e.g., granular solids into liquid), steam heating (uniform temperature), cleaning baths, plating, chemical processing, or other.
- Tank contents: Specific gravity (density relative to water), viscosity (e.g., Newtonian like water/mineral oil vs. non-Newtonian), and any abrasives/corrosives.
- Operation: Batch (defined blend cycle time) or continuous.
- Blend cycle time: Often defined as achieving three full turnovers (complete circulation of tank volume 3 times) for uniformity.
- Motive fluid details: Pressure (optimal 20–70 PSIG for best efficiency), flow available, and source (recirculated tank contents or external).
- Other: Desired turnover rate (e.g., turnovers per hour), temperature, and any constraints (e.g., no dead zones, sanitary requirements).
Location/placement is equally critical: Install for optimal plume coverage (e.g., bottom entry angled toward opposite walls, multiple units for large/irregular tanks to eliminate dead zones). Flow plume length scales with pressure drop (~1 ft per 1 PSI or 1 m per 23 kPa).
Entrainment and Circulation Ratios (Rules of Thumb)
- Circulation ratio: Supply (motive) to discharge is typically 1:5 (i.e., 1 gallon motive entrains 4–5 gallons of tank contents).
- Most efficient range: Inlet pressure 20–70 PSIG (140–480 kPa) → 3–5 gallons of tank contents mixed per gallon of operating fluid (discharge volume ~4–5× motive flow).
- Outside optimal range: Ratio drops to ~2.6:1 (lower mixing efficiency).
- Turnover rate determination: Total eductor discharge flow must achieve the required turnovers. Example: For a 10,000-gallon tank needing 3 turnovers in 1 hour → require ~30,000 gallons/hour total discharge flow from all eductors.
Performance Tables (from Site Excerpts)
Model TLM Operating Fluid Flow – GPM (m³/min) at Various Pressure Differentials (Inlet to Tank Pressure)
(Partial table for common sizes; higher pressures increase flow)
| Size | 10 PSI (69 kPa) | 20 PSI (138 kPa) | 30 PSI (207 kPa) | 40 PSI (276 kPa) | 50 PSI (345 kPa) | 60 PSI (414 kPa) | 70 PSI (483 kPa) | 80 PSI (552 kPa) | 90 PSI (621 kPa) |
|---|---|---|---|---|---|---|---|---|---|
| 3/8″ | 7 (0.027) | 11 (0.042) | 13 (0.049) | 15 (0.057) | 16 (0.061) | 18 (0.068) | 20 (0.076) | 21 (0.079) | 22 (0.083) |
| 3/4″ | 15 (0.057) | 22 (0.083) | 27 (0.10) | 31 (0.12) | 35 (0.13) | 38 (0.14) | 41 (0.16) | 44 (0.17) | 47 (0.18) |
(Larger sizes like 1″, 1-1/2″, up to 3″ scale up significantly; max total mixed capacity per unit can reach ~12,730 GPM in some configurations.)
TLM Nozzle Flow (GPM) at Various Motive Pressures (PSI) – Plastic Models Example
(For PPL/PVDF versions; free passage indicates max particle size)
| Model | Free Passage (in) | 10 PSI | 15 PSI | 20 PSI | 25 PSI | 30 PSI | 35 PSI | 40 PSI | 50 PSI |
|---|---|---|---|---|---|---|---|---|---|
| TLM00MP | 0.188 | 3.2 | 3.9 | 4.5 | 5.0 | 5.5 | 5.9 | 6.3 | 7.1 |
| TLM0MP | 0.288 | 7.5 | 9.2 | 10.6 | 11.9 | 13.0 | 14.0 | 15.0 | 16.8 |
Sizing Process Overview (Step-by-Step from Site Guidance)
- Calculate required total discharge flow: Tank volume × desired turnovers per unit time (e.g., 3 turnovers/hour → flow = volume × 3 / 60 min for GPM).
- Determine motive pressure available (aim for 20–70 PSIG for max entrainment ~4–5:1).
- Use tables to find eductor flow: Select size(s) where motive flow at your pressure provides sufficient discharge (discharge ≈ motive × 4–5 in optimal range).
- Calculate number of eductors: Total required discharge / discharge per eductor. Use multiples for coverage in large tanks.
- Account for fluid properties: Higher viscosity or specific gravity reduces effective entrainment — derate accordingly.
- Verify placement: Ensure plumes cover the tank (e.g., angled installations, avoid short-circuiting).
- Submit for confirmation: Use the Tank Eductor Sizing Request Form with all details for exact model/size.
Materials and Sizes
- Stocked: ½″ to 3″ (carbon steel, 316SS, bronze); plastic (PPL, PVDF, PVC) in ¼″, ⅜″, ¾″, 1″, 1½″ MNPT.
- Specialty: Hastelloy®, Alloy 20, sanitary designs.
- Same-day shipment common for standards.
For a specific tank (e.g., provide volume, dimensions, contents, motive pressure, desired mix time), we recommend our request forms for precise sizing.