5 replies to this topic

[aditi]

Hello Everyone,

I am new to pumping systems and need some inputs on various aspects of pump control.

 

I am working on a process where a new pump is added in parallel to the existing 3 parallel pumps.

The fourth pumps is 300HP where as the existing pumps are 150HP.

The objective is to control the discharge pressure at the common header by throttling the control valve on the discharge of the new pump.

These pumps are charge pumps and there are 3 pumps on the discharge and suction of these pumps.

 

My concern is:

1. Can the discharge pressure be controlled effectively by throttling only one valve?

2. What is the effect of this control valve on the discharge of the other 3 existing pumps.

3. Any other concerns that you all might see by trying to control the  discharge pressure by throttling the valve.

 

Any help is appreciated. The initial design was to add new pump with VFD however the client wants to check if we can add a fixed speed pump and achieve the same with Control Valve.

Attached Files

•  pumps.docx   124.62KB   20 downloads

Edited by aditi, 15 April 2014 - 04:58 PM.

[Ajay S. Satpute]

Hi,

 

Please provide system P&ID and pump curves (of existing and new pumps).

 

 

Regards.

 

Ajay S. Satpute

[pdender]

aditi,

by putting a control valve on the discharge of a pump you can modify the curve (i.e. flow vs. dP)

but there are disadvantages as higher power consumption etc. which you should consider,

generally one selects a suitable pump given the operating conditions,

the manufacturer can evaluate the flow vs. dP curve in your pumping system and propose

a suitable solution,

btw are you purchasing a new pump or using a stock ?

[aditi]

Ajay,

I have uploaded the diag showing how the pumps are connected. At this point we do not have pump curves for existing pumps. This is a new pump which we haven't bought yet. It is to be decided yet if the VFD works best or the control valve modulation' 

[Bobby Strain]

You need the existing pump curves. The solution may be as simple as providing a restriction orifice at the discharge of the new pump so that its curve is approximately the same as the existing pumps.

 

Bobby

[Ajay S. Satpute]

Aditi,

 

You may contact the existing pump vendor requesting pump curves. I see no reason why vendor would decline the request.

 

For the new pump, vendor must provide the pump curves. It is a part of technical quotation.

 

Without the needed data, it is all speculations and not the solutions.

 

Regards.

 

Ajay S. Satpute