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Jet Mixers Versus Side Entry Propeller Mixers For Tank Blending / Mixing
25 December 2010
Recently we were asked to evaluate the merits and demerits of jet mixers versus side entry propeller mixers for tank blending mixing specially for tanks containing crude oils with BS&W.
Some investigation into the matter led us to the following information which might be slightly biased considering that the information has been provided by a SEPM supplier. However, the arguments presented seem quite logical and make sense:
Some arguments that go against jet mixers are:
1. Jet mixers are more power intensive due to the significant energy losses at the pump, in the pipework and most significantly in the nozzles
2. Jet Mixer nozzles are susceptible to clogging particularly if the tank contains solids and BS&W.
3. Jet Mixers may not provide very effective mixing in case the tank diameters are very large due to the fact that jet energy dissipates very rapidly as the distance form the nozzle tip increases.
4. Pumping equipment associated with jet mixers has to be extremely reliable in handling corrosive and viscous tank products on a continuous basis, in particular the pump mechanical seals integrity and reliability has to be very high.
5. Since jet mixer nozzles are projecting to quite an extent into the tank, they are less maintenance friendly compared to the SEPM's.
6. Due to the pumping infrastructure required for jet mixers installation and maintenance costs are higher in comparison to SEPM's.
I am attaching an article from SPX Flow Technology which corroborates what I have mentioned above and also gives further insight into the working of Side Entry Propeller Mixers (SEPM's).
Enjoy reading and don't forget to share your experiences with regards to tank blending / mixing in general and crude oil tanks in particular.
Regards,
Ankur
References: Tank Storage Magazine
Attached Files
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tankstorage_plentymixers_pr.pdf (389.5KB)
downloads: 4659
Few Points came in mind (but may not be limited to these) remain valid to consider For large diameters tanks need multiple(quite a few) side entry openings; increasing Risk of Leakage in lower most shell area(1st tier) under liquid head all times. The Leakage susceptibility of propeller shaft sealing is to be thoroughly taken care-off For corrosive/ solid containing contents/dryer petroleum products more leakage risks. Tanks have to be kept at low levels or out of service if any SEPM's taking out maintenance is involved.