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Agitator design

Agitator design

Agitator design

Hi buddies.

I want to install a top mounted agitator in a storage tank for emulsifying process. May I know what type of impeller that I should use and any other parameter that I should consider.

RE: Agitator design

Since you have provided no information...

Things you should consider:

  • Aspect ratio of the tank
  • Viscosity of the separate phases, unless this is pre-emuslified before coming to the storage tank.
  • Viscosity of the emulsion
  • Rheology of the emulsion
  • Relative density difference between the phases
  • Shear sensitivity of the process
  • Foaming potential
  • Mounting arrangement on the tank top - how to support the agitator weight?
  • If this is emulsified elsewhere, the specific power of the other mixing process is a good place to start as a maximum required value. Keeping an emulsion together usually requires less power than creating it, but sometimes the difference might not be much.
  • Criticality of the process? Should mixing software be purchased to validate initial estimates?

RE: Agitator design

Write a performance specification and submit to several reputable agitator vendors. Get a performance guarantee!

Good Luck,

RE: Agitator design

Yes, you may ...

Latexman, as always, is spot on .... mixing performance specifications are certainly the way to go.

But before you can write one you must know all of the details of your process as well as the mechanical details of your tank...

Agitator performance and lifetime depend a lot on the flexibility of the tank mounting .... Have you given this any thought ?

Will you be using a tank rigidly-mounted mixer/agitator "bridge"? ....Or something else.... This has been discussed many times on these fora ...

Open or closed top tank ? ..... Is there space/steelwork above the tank to pull the agitator for maintenance.

On closed top tanks, will there be both shell mounted and topside manways for access ?

Is this a brand new tank, or are you going to mount your new agitator on some old, rusted and very flexible old antique

More details please ...

Sr. Process Engineer

RE: Agitator design

Your description is too vague to get support . What do you mean by emulsifying process? what is the quantity to be stored? I guess your process is a batch process !....

Is it an existing unit or a project ?



More info are needed .
My view.

RE: Agitator design

Agitator design (for economy and performance) is a multi-faceted matter.

The size and proportions of the vessel are critical, as are the properties of the fluid. The best impeller choices may be axial flow, radial flow, high shear … it all depends on the vessel geometry, required shear at the impeller, and circulation strategy chosen by the mixer designer.

Provide the material of construction you require. For tanks greater than 3 diameters high, seriously consider if an in-tank bearing is permitted. In-tank bearings greatly reduce agitator size and loads applied to the mixer mounting nozzle. Batch vs. continuous. Inlets and outlets. For processes where an in-tank bearing aren't practical (abrasive solids in the process fluids for example), keep the vessel height in check.

Make sure your tank supplier receives all structural loads and rigidity requirements from the mixer vendor. Mixers apply heavy bending loads to the mounting nozzle, and your tank needs to be suitably designed for it. Also make sure the anti-swirl baffle geometry is transferred to the tank design.

There is an agitator specification published by PIP. Feel free to read it for reference, however in my experience, one must be extremely selective using that content or else costs and negotiations will skyrocket. Very few agitator designs will benefit from applying all of the PIP standard, and most agitators require very little of it.

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