6 replies to this topic

[Srinivas Agastheeswaran]

How the decrease in pressure drop in the downstream pipeline affects the pump power consumption for the same flow rate? Pumping fluid may be considered as LPG. How it can be calculated theoretically?

Edited by Srinivas Agastheeswaran, 19 November 2024 - 08:44 AM.

[katmar]

What type of pump is it?  If it is an existing centrifugal pump you cannot maintain the flow rate constant unless you keep the pressure drop constant.  If this is a new installation that is still being designed then having a lower pressure drop would allow you to select a smaller pump.

 

There are many web pages that will explain how to calculate the power consumed in a pump.

[breizh]

Hi,

Consider studying this document related to centrifugal pump.

If you reduce TDH you will reduce the power consumed. TDH being Discharge head- Suction head.

Pay attention also to efficiency, this also an important parameter.

You should prepare a specification sheet and submit it to reputable vendors to get a technical proposal.

Good luck

Breizh 

Attached Files

•  KSB Centrifugal-Pumps-data.pdf   3.47MB   7 downloads

[Srinivas Agastheeswaran]

What type of pump is it?  If it is an existing centrifugal pump you cannot maintain the flow rate constant unless you keep the pressure drop constant.  If this is a new installation that is still being designed then having a lower pressure drop would allow you to select a smaller pump.

 

There are many web pages that will explain how to calculate the power consumed in a pump.

Hi Mr. Katmar,

 

Thanks for responding. It is a 20 year old centrifugal pump of BB5 type with VSD.

 

My objective is to calculate the amount of energy that would be saved in pumping if a certain pressure drop in the downstream line is eliminated. Since, it is equipped with VSD, i believe that after eliminating the pressure drop, at comparative lesser pump speed, the desired flow would be achieved. Please correct me if i am wrong.

Edited by Srinivas Agastheeswaran, 20 November 2024 - 12:44 PM.

[Srinivas Agastheeswaran]

Hi Mr. Breizh,

 

Thanks for responding and for the useful attachment.

 

I can understand that the system curve would be shifted if we reduce the pressure drop. Since, the pump i am referring is equipped with VSD, the change in system curve may be tackled i believe.

 

As the pump input power is (Density*g*Q*H)/ Pump eff., will the decrease in diff head by 2%, reduces input power by 2%? or anything else am I missing? 

 

Hi,

 

Consider studying this document related to centrifugal pump.

If you reduce TDH you will reduce the power consumed. TDH being Discharge head- Suction head.

Pay attention also to efficiency, this also an important parameter.

You should prepare a specification sheet and submit it to reputable vendors to get a technical proposal.

Good luck

Breizh 

[breizh]

Hi,

Regarding VFD, consider the doc attached.

You should find tips .

Breizh

 

Attached Files

•  Variable Speed Pumping_ A Guide to Successful Applications-Elsevier Science (2004).pdf   7.7MB   8 downloads

[katmar]

Having a VSD on the pump makes what you are doing very feasible, and this is really what has made VSDs so popular in the last few decades (along with the significantly reduced cost of these drives).

 

The complication in calculating the power saving is estimating the pump efficiency at the new conditions.  You can use the pump affinity laws to estimate the required speed at the new conditions and if you can get your hands on fixed speed pump curves for a couple of different speeds you should be able to interpolate a reasonable estimate of the efficiency at the new speed.