Piping design 1

[titiz]

Hello
I'm an engineer student in my last year and in my project i need to do some process piping design

I already choosed the materiel and a have as inputs the flow rate, pressure and temperature.
But i'm stuck at finding how to calculate the minimum diameter of the pipe.
I used the fact that the velocity equal the ration of the flow rate and area to find the diameter but i don't know when this formula is considered correct.
So if you can help me find out how to design the diameter with some precise formulas or norms i would be gratefull.

Thank you.

 

[zdas04]

"I already choosed"??????? If this is an English-as-a-second language choice of words then you might want to use the Translation Assistance forum. If not, then you can expect to have your work seriously discounted by other engineers simply for choosing inappropriate word constructions. I know this sounds pedantic, but I've seen good engineers get shunted to lousy jobs because of communications skills, that really sucks.

You didn't say if your fluid was gas or liquid. Makes a big difference. You can handle much higher velocities with gas than liquid. If it is gas, you need to be VERY careful to convert your flow rate from standard to actual conditions prior to calculating velocity, velocity at standard conditions is a meaningless value. If your fluid is liquid then the API has some guidance (I can't remember the API document number, but Google can find it for you).

If it is gas then you are pretty much on your own. Some companies have a velocity limit in their internal standards, these values tend to be around 100-120 ft/s, but if the line is very long those values result in too much pressure drop and many engineers use 5-15 psi/mile dP as their upper limit (I use 15 psi/mile for pipes 12 inch and smaller operating below 1000 psig and 5 psi/mile for bigger pipe and all pipe operating over 1000 psig, but that is just me and 50 engineers on this site will have 50 other numbers).

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[LittleInch]

You should have tools at your disposal to do this, but a simple on line search will give you many online calcuators to establish pressure drop for pipes.

If you know, or can guess, your density, pipe length, pressure at start and finish, any elvation difference, fluid viscosity at your temperature, then a bit of trail and error will get you your line size.

As Dave says, start at about 2 m/sec for a liquid and maybe 8-10 m/sec for gas (actual velocity).

Or consult a few text books.

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

 

[titiz]

Thank you for your answer, and no English is not my second language, I used for research and I’m still working on it. Thank you for your help.
My fluids are: Mp steam, treated water and boiler feed water; I don’t want to use values without reasonable considerations or based on experience. We are not allowed to use them in our project that’s why I’m trying to find the some theory background.

 

[LittleInch]

Search "fluid flow in pipes" or "Hazen williams" and you'll get some more ideas and formula.

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