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Flow velocity

Flow velocity

(OP)
I'm asking about the eligibles values of the velocity in water pipeline (drinking water) (discharge pipes and aspiration pipes). I need references of these information.

RE: Flow velocity

Make sure you consider the Reynolds number or you could get turbulent flow.

RE: Flow velocity

plazma: ALL water flowing in properly sized pipe is in turbulent flow, so what's your point?

Remember that velocity rules of thumb for line sizing are all based on an economic optimization between two competing factors: pumping energy and the cost of purchasing and installing pipe. If the water is clean rather than being an aqueous slurry or sulphuric acid, erosion is seldom a consideration unless you're designing infrastructure with a 50+ yr design life.

RE: Flow velocity

Quote (moltenmetal)

erosion is seldom a consideration unless you're designing infrastructure with a 50+ yr design life

For potable water sytems it is actually a major concern, especially in copper pipe. That is why cold water is kept to a velocity of 5-8 fps while hot water is kept to 4-5 fps. A well designed plumbing system will easily last more than 50 years.

RE: Flow velocity

Ouahmed,

Can you provide a bit more guidance on what you're trying to do.

As you've probably discovered, there are no fixed velocity limits in any document , AFAIK, which can be referenced for clean potable water, only guidelines in various documents / websites / forums.

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

RE: Flow velocity

(OP)
plazma,
i'm not asking about turbulence , thx
littleInch,
i want to evaluate the velocity of the flow in pump station, so i ask if there is limits for the velocity (to not damage the pipes for example ...), i hope you get my point
thx for all replies

RE: Flow velocity

No limits.

Practical / good practice is somewhere between 1.3 to 3 m/sec, but in particular locations could be higher or lower. As MM says, the issue is a balance between pressure drop and cost of the pipe.

Velocity inside piping / pump stations is usually a lot higher than in a long pipeline due to much smaller lengths.

Rather vague question so rather vague answer.

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

RE: Flow velocity

if we are just talking about a pump station than suction header / lines should have very low velocity and discharge header / lines can have much higher. the transmission line should be sized for economical pumping and designed to minimize transients.

RE: Flow velocity

cvg - depends what the PS is doing - booster pump stations or those fed with fluid from a booster pump or a system with a lot of head wouldn't need "very low" velocities.

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

RE: Flow velocity

Fluid velocity is determined by the economics of pumping, not some arbitrary factor. A fluid velocity higher than 15 ft/s is possible. However, you can be sure that high fluid velocities and long pipe runs will not be economical.

Reasonable pipe velocities depend on the application. There is no correct velocity for all applications. Here is a general guideline.

Reasonable Velocities for the Flow of Water through Pipe (from Cranes Technical Paper 410):

Boiler Feed.............8 to 15 ft/sec
Pump Suction ............4 to 7 ft/sec
General Service.........4 to 10 ft/sec
City.......................to 7 ft/sec
Transmission Pipelines...3 to 5 ft/sec

Go to a basic hydraulics book. Try Cranes Technical Paper 410 as a reference for the above velocities.

http://www.eng-tips.com/viewthread.cfm?qid=111206

http://www.eng-tips.com/viewthread.cfm?qid=348061

http://www.amazon.com/Fluids-Through-Valves-Fittin...

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