Download Minimum Safe Flow for a Centrifugal Pump

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minimum safe flow centrifugal pump

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Minimum Safe Flow for a Centrifugal Pump

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asade abiodun

Jul 19 2012 07:48 AM

Good Ankur,

Please, how can one determine the pump efficiency at shut-off for a pump when the efficiency at zero flow and shut-off is zero when read on the pump performance curve.

vamsi

Oct 10 2012 03:42 AM

sir,
miminum safe flow flow for centrfugal pump apart from temperature rise,
do we need specify minimum safe flow based on mechanical vibrations(safe limit) of rotating equipment ?

venkisowji

Jan 28 2013 01:38 AM

Dear Ankur,

Good Day...Its a very good blog and thanks for sharing the same.

Regards,

VENKI.

ayush

Mar 20 2013 11:30 AM

Sir,

Please reply with answers to above queries

ankur2061

Mar 21 2013 12:03 AM

Sir,

Please reply with answers to above queries

Ayush,

I had already answered your question in the main blog entry. I will repeat my answer here:

Your statement is incorrect. The pump efficiency will be low but it cannot be zero. The pump is still running against a blocked discharge and the mechanical energy from the driver of the pump is being lost by generating heat in the pump casing instead of overcoming the head as change in the potential energy of the liquid being pumped

This can be proven through the power equation for any pump:

P = Q*H*ρ*g / 3600*η*1000

where:

P = power, kW
Q = volumetric flow rate, m3/h
H = head, m
ρ = density, kg/m3
g = 9.81 m/s2 (grav. constant)
η = efficiency, %

If η becomes zero the power required at shut-off would be infinity which is not correct. Hope it is clear now that efficiency is not zero at shut-off.

Regards,
Ankur.