How can we reduce the pressure in a pipe?

[cyentist]

Hello

We have a pipe that receives water at a constant rate. This creates pressure in the pipe. Is there a way to reduce pressure downstream?

Which equations describe the factors that affect pressure?

Thanks!

 

[anorlunda]

Can you clarify your question? Do you want to hold flow constant while reducing pressure?

 

[Chestermiller]

Do you really mean downstream, or do you actually mean upstream?

 

[256bits]

Vertical or horizontal pipe

 

[russ_watters]

Pressure regulator...?But I agree more info needed...

 

[Rive]

We have a pipe that receives water at a constant rate

This would mean some kind of forced rate? If so, then to get lower pressure you need a second pipe in parallel.
Or just one but with bigger diameter.
But more information might result in more useful answers...

 

[JBA]

Determining what type of solution is available depends on analysis of not just one pipe section, it must be done based upon the entire piping system from the type of supply pressure source to the final downstream discharge and all components between those points.

 

[jim hardy]

We have a pipe that receives water at a constant rate. This creates pressure in the pipe. Is there a way to reduce pressure downstream?

A question well stated is half answered.

What's the flow rate and do you have control of it ?
What's the size of the pipe?
To what does the pipe supply water ?

The wiseguy but perfectly logical answer to your question would be "Let the water out" .

Which equations describe the factors that affect pressure?

This is a wildly popular reference : "the Crane handbook"

. Most mechanical engineers i know have a copy in their desk drawer. Surely your library has one.

old jim

 

[JBA]

Crane's tech report is definitely considered the bible of piping systems and provides the pressure differential between the inlet pressure and a downstream point in flowing piping system; however, the key element of the pressure at any point in a pipe (system) is what is downstream of that point that is causing the pressure. A pipe with no downstream restrictions will not have a static discharge pressure at its end. That is why a full system analysis is required.

 

[anorlunda]

Sadly, the OP has not returned to PF since posting that question. So we might as well stop speculating what he meant.

 

[jim hardy]

A pipe with no downstream restrictions will not have a static discharge pressure at its end.

How True !
@JBA you surely are a gentleman. That's the polite and civil way to say "Let the water out."
Wish i'd thought of it.

old jim

 

[cyentist]

Sorry I was on an induction for the whole week finishing very late and now I am ill.

We have a horizontal pipe which is connected to a pump and water flows.

At some point of the pipe, the walls are rusty and it may break.

Is there a way to release some pressure at that point? (I suppose downstream the pressure will continue to be lower, but that's fine)

Any ideas?

 

[JBA]

What is the type of pressure supply pump used, i.e positive displacement, centrifugal or what?
What is the fluid you are pumping?

 

[gmax137]

Any ideas?

Replace the rusty part of the pipe
Turn off the pump
Cap the rusty pipe upstream of the rusty part
Tee into the pipe upstream of the rusty part, run new pipe from tee to wherever the water goes
Reduce the pressure in the (tank, whatever) feeding the pump

As others have said, more information is really needed to make appropriate suggestions.

This copy was $8 new.

 

[cyentist]

What is the type of pressure supply pump used, i.e positive displacement, centrifugal or what?
What is the fluid you are pumping?

The pump is centrifugal and the fluid is water, but it should be independent of this information.

I was thinking introducing an obstacle in the pump to convert flow energy into heat, would that reduce pressure as well?

 

[gmax137]

if you add a restriction in the pump discharge piping, the pressure between the pump and the restriction will increase, but the flow will decrease. the pressure downstream of the restriction will likely decrease (if the far end of the pipe is open to atmosphere). all this depends on the pump discharge pipe being just a simple single line. if the discharge piping has branches then it would be a more complicated problem.

 

[jim hardy]

it'll probably spring pinhole leaks long before it fractures.
unless this is a several thousand psi system i think you're suffering much ado about nothing...

 

[Tom.G]

Since the OP doesn't like to supply details, here is another wild guess:
If there is a pressure switch controlling the pump, then turn it down!
If no pressure switch, install one.

 

[Asymptotic]

Install an inverter drive on the pump motor, and reduce speed until flow is reduced to a just barely acceptable value. Line pressure will also fall off as pump speed is reduced.

As @jim hardy pointed out, pinholing is the more likely failure mechanism to observed from internal pipe corrosion, but it can also weaken seam welded pipe and cause a cartoon-style rupture. The only time I've seen either happen with any regularity was when schedule 10 pipe was used as a "cost saving" measure during a production line installation. It was necessary to replace it all within 5 years with schedule 40.

Is this water in a closed loop system? If yes, and corrosion is a problem it pays to design and implement a water treatment strategy tailored to your make-up water chemistry and operating conditions.

 

[Rive]

We have a horizontal pipe which is connected to a ...centrifugal ... pump and water flows.

If that's all and the system itself is not pressurized, then your idea about choking the flow between the pump and the pipe would be a temporary solution as long as the pump still can remain within the limits of acceptable operation.

But, you know, rust needs no rest... At some point that pipe will need some repair anyway.

 

[cyentist]

So, if I have a pipe that divides into two smaller pipes with some angle, and I but an embolus that will sit at the split and partially obstruct the flow, the pressure in the two smaller pipes will decrease?

 

[gmax137]

generalized questions like this cannot be answered. fluid flow is a system problem: you must provide all the details or no one can answer meaningfully.