Using two pipes of same diameter for a pumping pipeline.

[E_D_S]

Hi All,

Could someone please advise me on the following:

I am designing a pipeline to deliver water from a WTW to a reservoir. Static head is 171.1m. I am wanting to use a 4 stage pump, and have one on standby. My question is... How does the system/pump curve get affected if I split the pipe into two parallel pipes (equal diameters) from the pump? Will the flow double?

Any advice is appreciated. Thank you in advance.

Erin

 

[mk3223]

Suggest to search similar topics in the "Pump Engineering" forum or move your post to it.
See the link below for the basic concept of both the series and parallel pump operations.

https://www.engineeringtoolbox.com/pumps-parallel-serial-d_636.html

 

[cvg]

the short answer is probably not unless you have two pumps

https://www.engineeringtoolbox.com/pump-system-curves-d_635.html

 

[bimr]

It depends on the size of the pipes and the headloss through the pipes.

The headloss is resistance to fluid flow plus the static head. The pump doesn't care what type of pipe network you are pumping into.

Use one of the online pipe flow calculators to estimate the flow.

Flow Calculator

 

[katmar]

The best way to see what happens is to go back to the old fashioned manual calculation method and to plot the system curve on the pump curve. When you use two pipes for the same flow as you had in 1 pipe you reduce the frictional losses to only 25% of the single pipe case, but of course in your case you have a relatively high static head which remains the same no matter how big or how many pipes you have. The relative magnitudes of the static and frictional heads will impact on the overall impact.

Katmar Software - AioFlo Pipe Hydraulics

http://katmarsoftware.com

"An undefined problem has an infinite number of solutions"

 

[LittleInch]

E D S

I'm sure you understand your question, but I don't - see below.

I am designing a pipeline to deliver water from a WTW to a reservoir. Static head is 171.1m. What is the total head including friction??

I am wanting to use a 4 stage pump, and have one on standby. My question is... How does the system/pump curve get affected if I split the pipe (Pipe size of ??) - Split what into what??

Split inpliues divide so e.g. a 1m diameter pipe splits into two of 0.5m diam? or 2 x 0.75 m diam??

into two parallel pipes (equal diameters) from the pump? Pipes of size XX???

Will the flow double? Will the capacity of the pump double?
No idea as you have given us virtually zero data. It might, it might not, but yes, change something as basic as the pipe diameter and the flow parameters change. By how much is not possible to say with no data.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[jgailla]

What do you hope to gain by splitting the pipe? It is cheaper to use one pipe than two for the same flow.

 

[E_D_S]

Hi all,

Thank you for your responses. Apologies (LittleInch) for my late response - I am a new member. To clarify: I was proposed this configuration and since I had never dealt with such a situation I asked for some assistance. The configuration would be a DN 700 (as the single discharge pipe from the pump) split into 2 DN350's, where they would both meet at the same reservoir.

Apologies for the vagueness.

Regards,
Erin

P.S. I have decided to go with my original design and scrap the parallel system option.

 

[LittleInch]

Ok - thought it might be something like that.

"Will the flow double?" Errrr no. Same flow rate would double the frictional pressure drop. Same frictional pressure drop would result in about half the flow.

Now how much of your pressure drop is frictional and how much is static lift will change this considerably.

On a very basic level just add up the square area of the pipe to get equal pressure drops.

So a 700mm ID pipeline is area of 490,000. divide by 2 = 245 000. sqr root is approx. 500.

so one 700mm pipeline = 2 x 500mm pipelines





Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[BTJCM]

If you have only one pump the flow will stay the same(if you do not adjust the flow of the pump). If you are using two pipes with the same diameters, the velocity of the stream will fall down. You can check the formulas for the stream.

 

[LittleInch]

BTJCM

Read the OPs post above carefully. He's changing one pipe size (700mm) for two 350 mm diam pipelines.

The flow will not stay the same unless he's using some sort of PD pump, but in that case the frictional pressure will increase.

We still don't have any idea how much of the total pump pressure is static and how much is frictional...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.