Pump minimum flow calculation

[ChemMom]

I'm new to the site. I was trying to find information on how to calculate/determine minimum flow for a pump and ended up here. Can anyone tell me how to calculate minimum flow for a pump or direct me to help?

 

[ash9144]

For min flow you want to be sure to not dead head the pump. So look at the pump curve the flat part at to the left side of graph is the min flow.

 

[Latexman]

The pump vendor usually supplies the minimum flow. It should be stated on the pump curve for the specific pump and its impeller.

Good luck,
Latexman

 

[25362]

This subject has been discussed many times in the past. Some examples:

thread407-136129
thread407-145754
thread407-156557
thread407-163975
thread407-167783

 

[ChemMom]

Thanks for the help

 

[twobits]

To perform an analysis of a pump and know what it's capabilities and limitations you need your pump curve. You will be given the rpm and impeller size. You probably know this but your x axis is your flow rate with your y axis you TDH or total dynamic head. For your impeller at zero flow you will have your maximum TDH. If you take this number and divide it by 2.3 you will have the psig the pump will register when it is dead headed. If you are able to share with me the need for the minimal flow that would help.

Once your minimal flow is established you are able to verify the flow using the pump curve and a pressure gauge on the discharge of the pump. Read the pressure gauge, multiply it by 2.3 and that is the TDH you are imposing on your pump. Find that TDH on the y axis and run horizontally until you intersect the impeller curve. From here move vertically down to the x axis and that is the flow you have.

Of course if you have a positive displacement pump it is a different case. You cannot, cannot, cannot deadhead the pump. Positive displacement pumps almost always have either an integral or installed separately a pressure relief valve. The rating of the pressure relief valve will give you the maximum pressure or minimum flow the pump is designed for. This pressure rating multiplied by 2.3 will give you the TDH. As mentioned above find the TDH on the y axis and run horizontally to the impeller curve you have, run down to the x axis and that is the bare minimum flow you will ever have. Soooo, run a higher flow (less pressure) than that other wise the pressure relief will be going off.

I hope this helps.

 

[BigInch]

Note: "Pump Minimum Flow" is NOT pump minimum CONTINUOUS flow!

http://virtualpipeline.spaces.msn.com

 

[twobits]

Gee Inch,

In the Chemical Process Industries I have worked we were usually interested in a continuous minimum flow. I found minimum flow was needed for several applications. That is why I gave the explanation I did.

I have trained operators in plants to use a pump curve. They found using the pump curve a valuable tool in trouble shooting. The information also helped them in situations other than normal operating conditions. I always found the dynamics of operations always demanding and challenging. Excuse me if I confused anyone.

 

[BigInch]

2bits,

No worries. I also think your explanation is very good. I just saw that nobody mentioned min-continuous in the context of centrifugals and I thought it was worth another $2 input.

http://virtualpipeline.spaces.msn.com

 

[BigInch]

http://img210.imageshack.us/img210/6060/pumpcurveopsandreliabilrq0.th.png

http://virtualpipeline.spaces.msn.com

 

[saeedguldurrani]

I am new to forum. can somebody tell me, how to convert thermodynamic activity into molarity.
Thanks in anticipation

 

[BigInch]

It works best if you first find the right forum. Locate the "Heat Transfer and Thermodynamics Forum" and post this question there.

http://virtualpipeline.spaces.msn.com

"We can't solve problems by using the same kind of thinking we used when we created them." -Albert Einstein

 

[BigInch]

Thought we were in pump forum. Maybe you'll find your answer here, but you should start a new thread in any case.

http://virtualpipeline.spaces.msn.com

"We can't solve problems by using the same kind of thinking we used when we created them." -Albert Einstein