Nozzle/Branch pipe sizing

[PantheraX]

Hi all, I'm quite new to piping engineering, and I've been tasked to determine the sizing/diameter of a branch pipe for a reducing tee junction.

Are there any equations that I can use to compute this?

I've seen some of the ASME B31.3/31.4 and I am not sure as how it is governed. for example, the use of the header-branch diameter ratio.

Thanks all in advance.

 

[BigInch]

Theoretically you should start with a required flowrate and the available pressure drop to work with to get the branch diameter, or it becomes a purely mechanical exercise in which you could pick virtually any smaller, or even equal, diameter as the mainline. Generally you can use a stock T for diameters down to 1/3 the mainline diameter. Below that, probably branching from a weld-o-let would be more suitable.

What would you be doing, if you knew that you could not fail?

 

[PantheraX]

do you have any idea for reference that i could use to obtain the flowrate/pressure drop process?

 

[BigInch]

Probably a million on a slow day.

Gas or liquid line?

Google the D'arcy or Darcy equation, or the Churchill equation to get the pressure drop in a pipe running full. Churchill is easiest, no iterations needed to determine friction factor.

What would you be doing, if you knew that you could not fail?

 

[PantheraX]

ok i managed to go to the library and dig out a book "Flow of fluids through valve,fittings and pipe".

They gave the an equation for flow of fluid through nozzle and orifices. There is a diameter term inside, so I'll just use it to compute?

 

[BigInch]

No, that's for flow out of a tank nozzle, across an orifice, or something. You will find that you lack certain information for some of those variables and you won't be able to solve directly. You have a pipe with a pressure drop that will establish the flow rate for a given diameter.

What would you be doing, if you knew that you could not fail?

 

[PantheraX]

oh, so u mean i need to compute the pressure drop first? how do i find the pressure drop for a reducing tee?

 

[BigInch]

you need the pressure difference between 1) the pressure in the mainline at the point where you will place the tee and 2) the pressure at the end of the new branch at wherever it will tie in.

What would you be doing, if you knew that you could not fail?

 

[PantheraX]

i see, so using the pressure difference, i can find the diameter of the branch pipe

 

[BigInch]

YES! If you know what flowrate you want. Otherwise you can assume a diameter and see what flowrate that diameter gives you with your given pressure drop.

What would you be doing, if you knew that you could not fail?

 

[stanier]

PantheraX

You could download the freeware from this site and model the branches with different flow rates and compare the losses.

http://www.pumpsystemsmatter.org/content_detail.aspx?id=110

If you get to engineer systems of greater complexity you could invest in AFTs athom for steady state Impulse for dynamic analysis. The PSIM software is a cut down version of Fathom



"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

http://waterhammer.hopout.com.au/

 

[stanier]

PantheraX

In PSIM sotware the complex tee cannot be defined directly. However the pipes that are conencted to a tee can have a tee's losses defined.

Once drawn select the pipe and go to Fittings and Losses. Then select "Others" go to tees in the drop down menu. There you can add a tees loss, whether straight through or branch, to the pipe losses.

You could draw a system then copy and paste so two ssytems are on the workspace. One could be with losses and one without and you can see the differences.

Pipes could be kept short so losses in fittings mean more than straight pipe.

"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

http://waterhammer.hopout.com.au/

 

[BigInch]

Please let him learn how to do it a little bit before you change him from an engineer into a software operator.

What would you be doing, if you knew that you could not fail?

 

[PantheraX]

thank you so much BigInch and stanier!

will do the manual calculations for this first and attempt the software in awhile!

thanks again guys.

 

[BigInch]

Good plan. I think you have to at least get enough experience to be sure you can spot a garbage in - garbage out problem before you go pushing the buttons.

What would you be doing, if you knew that you could not fail?

 

[stanier]

Biginch is right, again. I got ahead of myself. Learn the basics before using a tool that automates what you are doing.

The AFT manual actually says all results should be checked by basic hand calculations. Sound advice indeed.

I you are member of a professional isntitution such as ASME, IMechE or Engineers Australia you will find that they have access to electronic libraries such as Knovel. there are numerous books on facilities piping that have the data you need to study.

The Crane reference is a classic as are books by Miller (Internal Flow Systems) and Idelchik.

http://www.pumpfundamentals.com/images/tutorial/friction loss-fitting.pdf

http://www.accutech2000.com.au/Flui...delling and Design Note 02 Tees and Wyes.pdf

http://books.google.com.au/books?id...AQ#v=onepage&q=fittings idelchik loss&f=false

"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

http://waterhammer.hopout.com.au/

 

[stanier]

This reference may be of help.

http://www.pumpfundamentals.com/pump_book.htm

"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

http://waterhammer.hopout.com.au/

 

[PantheraX]

hi guys, i've been trying the manual calculations and could i ask, in the equation of headloss (HL) = K(v^2)/2g, where does this headloss represent? between the start of the run pipe to the end of the run pipe? how do i then find the head loss between the section of the branch pipe?

 

[PantheraX]

hi guys, i've been trying the manual calculations and could i ask, in the equation of headloss (HL) = K(v^2)/2g, where does this headloss represent? between the start of the run pipe to the end of the run pipe? how do i then find the head loss between the section of the branch pipe?

and also, for the division of flow for tee fitting, could i just use the ratio of areas to compute?

 

[PantheraX]

let me try to answer my own question, correct me if im wrong guys.

1) the headloss equation for fittings, HL = K(v^2)/2g is for the head loss through the section of the branch pipe.

2) Division of flow for tee fitting, i'm supposed to use ratio of pressure drops. I've read that for reducing tee, flow split ratio may not be equal to ratio of areas.