Pump parallel operation-dissimilar pumps 1

[Meshry]

What are the constrains running dissimilar pumps in parallel?
Why should they have the same suction and same discharge pressure? what if one pump has different friction losses at the suction or discharge side from the other one?

Thanks

 

[MFJewell]

http://www.eng-tips.com/viewthread.cfm?qid=429711

 

[Meshry]

Thanks MFJewell for the link,
I could not find answer for the friction losses issue. can you explain?

 

[MFJewell]

Why should they have the same suction and same discharge pressure? what if one pump has different friction losses at the suction or discharge side from the other one?

Check the NPSHa versus the NPSHr for each pump. As long as that is good, you should be fine on the suction side. If the discharge pressure are different, you could deadhead the pump with lower discharge pressure. I would make a system curve and use the pump curves for each pump to confirm that application is correct. If the discharge pressures are close to the same, but the friction losses are higher in one discharge line versus the other, you will get more flow from one pump than the other.