6 replies to this topic

[Venkat @89]

Hello all,

I am very much interested to know when should we go for pumps in series and parallel?

How exactly it makes sense to go for them instead of single big pump? Thank you.

Very much welcome if some good material or pdf is attached to understand it.

[fallah]

Chalapathi,

 

In brief:

 

Parallel for additional flow rate

 

Series for additional head

 

Good materials can be obtained by "Googling"...

[samayaraj]

For a fixed flow & speed, head can be increased by increasing the diameter of impeller. For higher head requirement, you need a very big size impeller. As per the affinity law, head H₁/H₂ = (D₁/D₂)² and power P₁/P₂ = (D₁/D₂)⁵ for doubling the head, you need bigger dia impeller and need to supply more power. In addition, mechanical stability, fabrication etc need to be focused for such a big pump. Hence, its efficient to connect two or more impeller of smaller diameter to the same shaft where the discharge of first impeller is sent to the suction of next impeller and so on.

Edited by samayaraj, 28 July 2015 - 05:05 AM.

[thorium90]

It could be for the following reasons:

Operational flexibility: Production fluctuations. The maximum and minimum plant load cannot be easily handled by one pump. Splitting the load across 2 pumps allows to run 2 pumps at high load and one pump at low load.

Redundancy: Having 2x100% configuration might be more risky than 3x50%. Assume in 2x100%, one pump trips. There will be a moment whereby there is nothing running. In 3x50%, if one pump trips, at least one pump is still running.

Operational costs: Sometimes one large pump might not operate near its BEP and having 2 smaller pump which operate very near its BEP and at a higher efficiency may make better sense. For example, the manufacturer may have on its catalog one large pump with an efficiency of 50% at the duty point but they can also provide 2 smaller pumps but at 80% efficiency for a total for the same duty point. In that case, it might make more sense for 2 smaller pumps.

[Venkat @89]

Thank you all for your valuable responses.

[Zauberberg]

Here you have some great info on pumps in series and in parallel: 

 

http://www.pumped101...llel part 1.pdf

http://www.pumped101...llel part 2.pdf

http://www.pumped101...series_parallel

[Padmakar Katre]

Hi,

Few tips,

- it's just a capacity and head (higher capacity requirement, parallel and higher head then to be in series)

- replacement cost (parallel configuration subject to availability of plot space)

- variation in flow requirement (auto start of standby which is parallel e.g. fire water system)

- variation in head requirement (quite unlikely but also a case to consider)

 

Hope this helps.