Size Steam Motive Eductors for Pumping Liquids

To determine the correct eductor for a specific application, follow the steps in this section, using the performance tables (pages 3-4) provided to achieve your desired results. (NOTE: All Jacoby-Tarbox eductor tables use the 1-1/2 inch unit as the standard, and eductors are sized using a Sizing Factor (S.F.) based on this standard unit.) Larger View of Eductor Image

 

  1. If the suction fluid is not water, adjust the suction and outlet head Hs and Ho by multiplying by the specific gravity of the fluid.
  2. Find the suction lift (Hs) that is nearest to or exceeds your desired suction lift.
  3. Use the motive pressure (Pm) closest to or less than your actual motive pressure.
  4. Locate the outlet head (Ho) that is nearest to or exceeds your desired outlet head.
  5. Use the temperature column that is nearest to or exceeds the temperature of the suction fluid.
  6. The table will give the suction flow for Jacoby-Tarbox eductor models SG, HG. Divide the Desired Suction Flow (Qs) by the Tabulated Suction Flow for each of the models found in the performance table. This will give the Desired Sizing Factor (S.F.) for each unit.
  7. Pick a unit with a Tabulated S.F. that meets or exceeds the one found in Step 6. (Use table below.)
  8. Determine the motive flow required for each unit by multiplying the Tabulated S.F. for each model by the Tabulated motive flow (Qm). Repeat to find actual Suction Flows.
  9. Pick the unit that most closely matches the desired flows for the motive and suction.
 
Example:
Desired Suction  
Flow Rate (Qs) 17 GPM
Suction Lift in Feet (Hs) 15 Ft
Outlet Pressure (Ho) in feet of water 20 Ft
Motive Steam Pressure (Pm) 100 PSIG
Motive Flow Available(Qm) 500 Lb/Hr
Suction Temperature (Ts) 100"F

 

After working through the first 4 steps of the sizing directions, we find the tabulated suction flows for the two models in 1-1/2" size are:

  • SG..................... 30 GPM
  • HG.................... 21 GPM

The Desired Sizing Factors are as follows:

  • SG: 17 GPM Desired/30 GPM tabulated= 0.57 Desired S.F.
  • HG: 17 GPM Desired/21 GPM tabulated 0.81 Desired S.F.
For the model SG this will require a unit with a Desired Sizing Factor of approximately 0.57. A 1-1/4" unit has a Tabulated S.F. of 0.61. This unit will have an actual suction flow (Qs) of [30 GPM x 0.61 Tabulated S.F.] or 18.3 GPM. The motive flow (Qm) will be [333 Lb/Hr x 0.61 Tabulated S.F.] or 203 Lb/Hr.
 
For the model HG this will require a unit with a Desired S.F. of approximately 0.81. A 1-1/2" unit has a Tabulated S.F. of 1.00. This unit will have an actual suction flow (Qs) of [21 GPM x 1.00 Tabulated S.F.] or 21 GPM. The actual Motive Flow (Qm) will be [750 Lb/Hr x 1.00 Tabulated S.F.] or 750 Lb/Hr.
 
For this application we can see that the model SG 1-1/4" has performance that is the closest to the desired performance for the application. The HG unit uses more steam than is available.
 
SL, ML, HL, SG, HG --- Sizing Factors (S.F.)
Unit Size 1/2" 3/4" 1" 1-1/4" 1-1/2" 2" 2-1/2" 3" 4" 6" 8" 10" 12"
S.F. 0.12 0.21 0.34 0.61 1.00 1.82 3.17 5.92 11.8 24.0 49.0 71.0 123.0
 
 
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