Multiphase flow pumped in parallel? 1

[kalizzy]

Hey everyone!

I am very grateful for the support I've found in this group. Again, I am here with an operational question.



The situation is, when I am helping in sizing a multiphase pump, manufacturer offers only one twin screw option for handling about 35,000 bepd, but this configuration is out of economic range, so there is another option.

What would happen if the customer decides to use two progressive cavity pumps in parallel to provide the total flow I need?
What are the electrical requeriments or problems I might find in this arrangement?
What are the operational, efficiency, or mechanical problems that might result?
I have been searching for information in similar situations, but I cannot find anyone, I mean, when we talk about centrifugal pumps parallel arrangement is often seen, but when I am talking about a multiphase flow in which I cannot know the real amount of gas each time, I am not sure.
The idea is not mine, but I would like to get some feedback in this situation because there is a lack of information.
Any reference literature to read about this topic?

The pump should be API 676 standard. The amount of gas is max 85% GVF.

Thank you in advance.

 

[innovativepumps]

Hi Kalizzy,

My take on your application is that multiphase pumping is generally incompatible with positive displacement pumps; a quick consultation with Chat GPT explained the merits of a twin screw pump for your application. I've worked on projects which involved a pair of positive displacement pumps and it is doable, best to have one pump running a bit faster than the other to minimize discharge pulsations.

 

[LittleInch]

Well contrary to innovative pumps (welcome!), PD pumps are the only ones I am aware of for multiphase pumping.

Progressive cavity are ok if the vendor says so.

Each pump can work independently or together, but both need to be rated to the same discharge pressure.

Pressure though is driven not by the pump, but by the downstream system. A PD pump will pump a continuous volume per second with pressure dependant on frictional and static pressure downstream. Ultimately the PD pump will just take whatever power it needs to pump your volume up to a pressure but in theory, without pressure relief or bypass, the motor could eventually stall.

Generally speaking two pumps will be less efficient than one larger one, but each is different so you need to look at your options.

This is a relatively simple multi-phase flow issue. Multiphase, by its nature is a complex and variable thing as the GVF can change rapidly and hence the pumps need to be robust enough to cope with more or less gas or liquid in a short time frame.

 

[innovativepumps]

My understanding has been that most PD pumps rely on pumping non-compressible liquids and that, specific with PC pumps, gas can compress within the stator/rotor cavities, leading to a loss of efficiency or complete loss of flow. Admittedly my experience has not been with multi-phase pumping (mostly separation). I'd also inquire with the PC pump OEM about the potential for accelerated wear of the stator/rotor due to the multiphase aspect of the application.