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Ref. needed for vortexing calculations for a fuel oil eductor system

Ref. needed for vortexing calculations for a fuel oil eductor system

Ref. needed for vortexing calculations for a fuel oil eductor system

(OP)
We utilize a centrifugal pump, that draws suction from a day tank, and pumps #2 Fuel Oil through an eductor located in an underground storage tank to refill the day tank.  The Day tank supplies FO to a Nuclear Standby Diesel Generator.  The drive flow is approximately 100 GPM and the draw from the storage tank is approximately 45 GPM.  I have tried to find information on the effects of vortexing on an eductor.  The eductor nozzel is directed upwards and the suction inlet is on the side of the assembly.  There are no vortex suppressors installed on this system.  The eductor vendor indicates that vortexing is a concern for an eductor however has no data to determine minimum submergence.  Being used in a Nuclear application, it is critical to assure that the usable volume is adequately predicted in the storage tank so that a Technical Specification 7 Day volume can be specified.  As we have accounted for fuel oil density, instrument accuracy, vortexing etc. on our required capacity, the calculated 7 day value is approaching the capacity of the tank.  We are at a point that we will need to add FO after every monthly 2 hour test run to maintain a required 7 day minimum storage level.

The Pump is located at elev 620, the eductor is 18" above the bottom of a 14 Ft diam. storage tank.  Eductor level is at approx. 604 Ft.  The return line to the daytank is at approx Elev. 635 Ft.  The eductor inlet is a 3" threaded brass pipe fitting.

Thank you for any information or references that you can supply.






RE: Ref. needed for vortexing calculations for a fuel oil eductor system

There is a formuula in this thread. Check whether this applies to your model. It is basically minimum submergence required for tanks to reduce vortexing.

Thread407-19111

And the formula given there is

S = D + ((0.574Q)/D1.5)

    Where    S = Minimum submergence required in inches
        D = Suction bell diameter in inches
        Q = Flow rate in USGPM
If the equation is useful to you, then thank butleja

Regards,

and the reference is ANSI/HI 9.8 – 1998, Section 9.8.7


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