Pump vs viscosity liquid

[adula29]

hi,
I wonder that is there a rule of thumb of selecting centrifugal pump for viscosity liquid.
How hight can be viscosity for centrifugal pumps.
Perhaps is there a corelation beetwen pump size and cSt value.

 

[rotw]

I think you will find good material here:

https://www.ksb.com/centrifugal-pump-lexicon/viscosity/191478/

 

[adula29]

Thank you, but it shows here how viscosity has an effect on pump characteristics.
I wonder if there is a rule for which the maximum viscosity can be centrifugal pumps.
It is obvious that the relationship should be the smaller the pump, the maximum viscosity should also be lower

 

[rotw]

I think your question is answered in the article.
If - for a given viscosity - the characteristics are affected, for example head is lowered to the point that you may not be able to satisfy the duty point requirement (for a certain flow you have to achieve a certain head) for a given selected pump, that means you have attained some sort of maximum limit for viscosity there.

 

[adula29]

 

[rotw]

Trends are good but can be misleading. Here is one example:

On a multistage pump I can compensate for head loss by adding an impeller without changing discharge nozzle diameter. This means I can accomodate higher viscosity without touching the nozzle size.

I think working through characteristics is more appropriate.

 

[LittleInch]

The ROT figure I heard from a pump vendor when looking at some viscous oil was that standard centrifugals were good up to about 300 cP.

I don't think it's size depeandant.

How accurate this I don't know as I've never had to try and pump anything that viscous, but has a certain ring of truth about it.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[rotw]

It looks like the consideration that there is dependency between maximum viscosity and pump size was put forward in a diagram by C.E. Peterson: "Engineering and system design considerations for pumps systems and viscous services" (1982). Was not able to get the paper in full details. Probably this is where the OP got the diagram from?

I found some further reading here:

http://www.warrenpumps.com/brochures/Fluid Viscosity Effects.PDF