How to reduce flow rate?

[rmme17]

What is a common way to reduce the flow rate and increase the back pressure on a pump driven by an electric motor? Are flow rate limiting valves a good choice or are there better methods to use? Flow rates in the pipe of aprox. 8 USGPM, 50 psi to 60 psi. If more specific information is needed, let me know. Thanks,

 

[BigInch]

A flow control valve should do the trick.

**********************
"Pumping systems account for nearly 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[MikeHalloran]

Big has clearly assumed that you are talking about a centrifugal pump. If that is not the case, other schemes would be more appropriate.

With any kind of pump, reducing the shaft speed or the size of the pump will reduce the flow without increasing the pressure, and waste less energy, at higher upfront cost.



Mike Halloran
Pembroke Pines, FL, USA

 

[chicopee]

You can always increase the discharge head. It may work depending on pump characteristic curve.

 

[IFRs]

Add a restriction after the pump - control valve, orifice plate, etc. Not the most efficient use of electricity however...

 

[JLSeagull]

Centrifugal pump impellers can be changed. Variable frequency drives are a consideration for a new installation; much harder to sell for an existing installation. Control valves are common on pump outlets. The level measurement can be used for pump start/stop control if the motor hp is sufficiently low to tolerate frequent starts.

 

[aswilson87]

A flow control valve on the discharge piping would meet both of your requirements. Also you could have the impeller trimmed down instead of buying an entirely new one.

 

[Artisi]

I can understand the need to reduce flow but why do you want to increase back pressure on the pump?

 

[MikeHalloran]

Uh, "...just let me know".

Via telepathy, I guess.



Mike Halloran
Pembroke Pines, FL, USA

 

[rmme17]

The idea to increase the backpressure is because the motor is overheating due to the pump impellers rotating too fast (making the motor run too fast, driving up the amps). This is the understanding anyways, certainly open to suggestions. The ideal pressure on the system we are shooting for is 50psi to 60psi, but it drops to about 15 psi due to problems with the pipeline set-up (which is connected to couple of other pumps, preventing us from changing the pipe diamter to a more suitable size).

 

[Artisi]

How can the motor run too fast - assume you are using a 50 or 60 hz AC motor which will only vary by a few RPM depending on the load - also increasing the head (pressure)reduces the power input.

The best way is to reduce the impeller diameter - this will reduce flow and also reduce the power requirement.

 

[BigInch]

Artisi, I think e's too far out on the curve for his motor power rating.

**********************
"Pumping systems account for nearly 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[Artisi]

BigInch - more crystal ball gazing - we should be experts by now

 

[BigInch]

How's your crystal ball work? Mine's very foggy.

Opps. Did you like my Birmingham accent?
When I was in the train station they kept asking me if I needed 'elp? I couldn't figure out who/what "elp" was. I wanted to go to John Brown's office in Sheffield. I kept looking at 'im asking "what"... probably 3 times before I figgured it out.

**********************
"Pumping systems account for nearly 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[Artisi]

From memory if you come from Birmingham (Bir/min/am) you're a "brummie" (spelling). I guess I'm lucky being an Aussie as we understand most of the pommie lingo as well as a lot of US slang.

 

[BigInch]

Uh.. right... thought you were the transplant.


**********************
"Pumping systems account for nearly 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[Artisi]

Nope - 100% dinky-di true blue Aussie.

 

[Artisi]

Forgot to add - fair-dinkum to the list.

 

[MikeHalloran]

Rmme... the folks who've been trying so hard to help you have been assuming that you're talking about pumping water with a centrifugal pump.

Inspection of your other questions suggests it is at least equally likely that you are pumping heavy oil with, e.g. a screw pump, in which case restricting the pump discharge is a REALLY bad idea.

You seem also to be reporting some layman's conclusions as data, and/or are a little fuzzy on those electric motor things and those pump things.

Why don't you start over, and describe:
- the piping topology
- what fluid you're pumping under what conditions
- what _exact_ pump you're using
- what exact motor is driving the pump
- what you have measured
- what YOU, PERSONALLY have measured
- why you think increased pipe pressure is a good thing
- what exact problem you are trying to solve







Mike Halloran
Pembroke Pines, FL, USA

 

[MJCronin]

Amen.... Mike.... Amen

How many times must we engage into "twenty questions" with the newbie who doesn't understand the fundamentals of centrifugal pump runout and the real need for a reasonable motor service factor..?

I am so sick of those who demand immediate answers from strangers...

-MJC