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Centrifugal Pump Sizing Considering MCSF

Centrifugal Pump Sizing Considering MCSF

Centrifugal Pump Sizing Considering MCSF

(OP)
As per my understanding pump vendors size centrifugal pumps (consider an API 610, OH2) for the rated flow(Rf). However, if the MCSF flow is through an orifice, this flow needs to be added to the rated flow, and the new flow (Initial rated flow + MCSF) becomes the rated flow (New rated flow: Rf_N). However, MCSF also depends on rated flow. Minor changes observed. (Consider the same pump selection at both flows).

Can this be ignored in sizing both the pump and min recirculation line? Since this goes into a loop while selecting.

Please do correct if my understanding is wrong.

MCSF:Minimum Continuous Stable Flow

Thanks in advance.
Stay Curious!!

RE: Centrifugal Pump Sizing Considering MCSF

I think your understanding is correct.

A continuous min flow recirc line though is not great. Consider either an automatic recirculation valve (ARV) or a controlled valve to only flow the min flow when you need it and not when you don't.

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

RE: Centrifugal Pump Sizing Considering MCSF

(OP)
@LittleInch: Thank you for the response.

However for low kW pumps (<20kW), as per my understanding, it is economical to go with the orifice.

Also, my query was regarding pump selection, in vendors' software. Since MCSF changes with Rated flow, how do finalize a pump model? (Since it can lead to a loop).

Thanks in advance.

RE: Centrifugal Pump Sizing Considering MCSF

Hi,
Better not to use acronym !
Vendors are working based on a specification sheet you are supplying with min , normal ,max flow rate . In other words it's your responsibility to supply a sketch with information on how you want to operate your pump.
Probably good to read : links underneath
https://www.pumpsandsystems.com/follow-these-steps...
http://www.liquiflo.com/v2/files/pdf/applicationno...


my opinion only.
Pierre

RE: Centrifugal Pump Sizing Considering MCSF

(OP)
@pierreick: Thank you for the response. Acronym reference updated in the original query.

I understand it is the client's responsibility on deciding the operational philosophy.
My query is regarding, how the vendor is selecting the pump. ie we can have access to the selection program of M/s Flowserve, M/s ITT etc.

RE: Centrifugal Pump Sizing Considering MCSF

Yes it could lead to a loop but it would be a decreasing one. Mcsf is a bit vague for many pumps with a band. Around 25 to 30% commonly.

So if you wanted a pump to do 100m3/hr forward flow, they know this is 70%, so would size it for 142. Then 30% mcsf is taken off to get back to 100.

Now if this pump is used infrequently then maybe a constant drain is OK, but I just hate wasting energy and with the cost of it escalating the impact of an ARV or similar would pay for itself faster than before.

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

RE: Centrifugal Pump Sizing Considering MCSF

(OP)
@LittleInch: Thank you for the response.

RE: Centrifugal Pump Sizing Considering MCSF

(OP)
@pierreick: Thank you for the additional references shared.

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