Any quick method to estimate MCSF in different speed?

[billbusy]

I have a pump with VFD. Currently the vendor provided the MCSF on a pump curve at a rated speed.

I am just thinking if there is a quick method I can estimate the MCSF at different speeds? similar as affinity law?

Thanks.

MSc. Mechanical Engineering;
5 years EPC experience;
Oil & Gas industry in Canada.

 

[1gibson]

Affinity law for flow is to scale 1:1 with speed, whether it is BEP or MCSF. Ok your operating parameters with the vendor.

 

[BigInch]

Provided your system curve cooperates.

Independent events are seldomly independent.

 

[DubMac]

This is a cut and paste job from earlier response to similar question.


MCSF is determined by maximum permissible temperature rise in the pump. This number typically comes from pump manufacturers empirical data.

The old equation for Temperature rise in a pump (don't know why a new one would be any better) is:
Temp Rise, DegF= (TDH,ft./778) * ((1/Efficiency at point considered) - 1)

If a manufacturer of a certain pump says the max permissible temp rise is 20 degrees, then you can backcalculate your minimum flow using the performance curve.

 

[Artisi]

"if there is a quick method I can estimate the MCSF at different speeds?"
Not that I am aware of, however lacking any further detail I would draw a line from the MCSF given by the manufacturer at the rated speed to the 0,0 point of the H/Q graph and use that as a guide. Bear in mind as you slow the pump radial loads on the shaft see a rapid reduction and hydraulically, without testing at all speeds and reduced flows the MSCF becomes guess work.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[TenPenny]

According to Goulds, you can use the affinity laws to adjust MCSF for changes in speed or impeller diameter, but if you have a sensitive application, check minimum thermal flow as well.