2 replies to this topic

[curious_cat]

We have a centrifugal pump circulating a slurry through an evaporator, basically a long tube vertical shell and tube HEX, which has a tendency to choke with deposited solids every so often. 

 

Would it be reasonable to assume that the pump motor's current will gradually reduce as choking progresses?

 

The pump has a usual curve with a slight droop in the head with flow. My reasoning is that as the downstream HEX chokes, the system curve (Head vs Flow) rises upwards and thus intersects the pump curve at operating points that have gradually lesser flows. i.e. Pump flow reduces over time. 

 

And this reduction in flow ought to manifest as reduced Power drawn and hence reduced motor current.

 

Is this assumption correct? Most composite curves that represent power drawn on CFG pump datasheets seem to show that P increases with Q? 

[fallah]

 

Would it be reasonable to assume that the pump motor's current will gradually reduce as choking progresses?

 

The pump has a usual curve with a slight droop in the head with flow. My reasoning is that as the downstream HEX chokes, the system curve (Head vs Flow) rises upwards and thus intersects the pump curve at operating points that have gradually lesser flows. i.e. Pump flow reduces over time. 

 

And this reduction in flow ought to manifest as reduced Power drawn and hence reduced motor current.

 

Is this assumption correct? Most composite curves that represent power drawn on CFG pump datasheets seem to show that P increases with Q? 

 

curious_cat,

 

You need referring to relevant P-Q curve; but normally yes, the pump's consumed power will be reduced per Q reduction. You should care the reduced flow not to be lesser than minimum flow specified by pump vendor, if the minimum flow facility isn't provided...

 

Edited by fallah, 12 August 2015 - 10:15 AM.

[curious_cat]

Thanks @Fallah

 

Yes, we plan to stop operations & take the HEX for a cleanup far before the minimum flow point is reached.

 

Basically to reach the minimum flow the HEX would need to be very grossly choked up. But long before that point the evaporation efficiency suffers so the HEX must be cleaned up.