Maximum velocity in pipes

[ChemEng84]

i'm a new commer in process engineering and i want to know what's the maximum velocity of any fluid in pipes? i heard that 80 ft/s is the maximum velocity of gases in pipes without any choking happening is this right and what about liquids.

 

[Artisi]

There will be an upper limit to velocity - but is something I have never concerned myself with establishing as it is a purely academic number and bears no useful purpose in fluids handling. What you should be concerned with is the friction loss which is a function of flow per unit of length, this in turn dictates the energy needed to maintain that particular flow.

My suggestion is get some tables on friction losses thru pipe or use any of the formula available to calculate the friction losses. As a process engineer this will be of more use to you than theoretical and useless maximums.

 

[PEDARRIN2]

If you have a fluid with any particulates, you could have a shorter lifespan due to erosion at higher velocities. Now what those velocities are will be a matter of experience - which you don't have at present. But at least now you will ask the question again.

While not in the process field, I limit domestic water to 8 ft/s - but always looking at the friction loss as well.

 

[moltenmetal]

There are services where erosion or erosion/corrosion is a real and serious concern- one that dominates sizing. But erosion is a minor concern with MOST normal fluid services. Think of the velocities inside the trim of a control valve and ask yourself if you're going to encounter anything CLOSE to that in the piping itself?!

Piping is sized for an economic optimum between pump and compressor energy input and pipe/fitting cost and labour. The optimum velocity shifts depending on circumstances. Pressure drop rather than velocity is the key deciding factor.

 

[Fackler]

I typically use 5 ft/s as an opening ballpark for my flow and friction loss calculations. I do allow up to 10 ft/s but this is rare. For reference I'm typically working on 1/2" to 6" pipe sizes.

 

[metalonis]

Check out API RP 14E, and "An alternate to API 14E Erosion Velocity Limits for Sand-Laden Fluids", Mamdouh M. Salama, Journal of Energy Resources Technology, June 2000

 

[BigInch]

5 to 10 fps max is for longer pipelines where particle erosion and no water hammer problems are expected.

For shorter segments of pipe, fluid velocities of 20-30 fps or more might be tolerated, but once again check that waterhammer effect.

"Less than 1% of the energy moving a car goes towards the driver."
Amory Lovins - The Oil End Game

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

 

[ChemEng84]

thanks alot for your most helpful answers, i'm concerned also with max velocity in valves, for both gases and liquids.

 

[BigInch]

Valves are another story. Control valves have special patterns to select from when needed, otherwise use full ports, if you think its going to be a problem.

"Less than 1% of the energy moving a car goes towards the driver."
Amory Lovins - The Oil End Game

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

 

[MJCronin]

Chem...

The "Piping Handbook" by Nayaar and "Crane Technical Paper #410" both carry recommended velocities for the economic design of piping systems.

As noted above, the tradeoff always is less capital cost (with the use of smaller pipe) versus higher operating costs (pumping costs.)

Saturated steam and superheated steam require more of a detailed evaluation than liquids, especially in cases where the piping goes long distances ( commonly called district heating systems)

Slurry systems are perhaps the most tricky, because the liquids must stay within a certain velocity range to ensure solids movement. A specific study of the proposed slurry is sometimes made by a lab to ensure a proper design.

Good luck

-MJC

)

 

[ChemEng84]

thanks alot for you all.

 

[kmpillai]

Hi,
Normally 3 to 12 fps is used for Water
100 to 200 fps for steam in the power in the industry.

KMP