gas piping

[johngerhart]

dies anyone know a good reference for sizing natrual gas pipelines starting with either 90 or 600 psi, we will be tieing into a new main for a prposed plant expansion

 

[gr2vessels]

johngerhart,
The tie-in piping has to be the same class as the main line, you don't need additional calculations for that. The sizing as diameter concerns, that's the local code requirements, fluid dynamics and configuration, pressure losses, etc...I guess the mentioned plant is somewhere in Europe, hence you should look for the locally applicable gas transmission pipeline code, the American or Japanese code might not suit your needs. I can help with some Australian codes for reference if you can use them...
cheers,
gr2vessels

 

[johngerhart]

thank you , but I was looking for a diameter / pressure drop sizing std , if there is one specifically for gas and/or pipeleines . I have the ASME designation for the installation

 

[PEDARRIN2]

There are standards but you have to use the one that pertains to where you are building your pipeline. In the US, it would probably be NFPA 54 which gives you the equations/tables for loads, pressure drops, etc. These tables are based upon compressible gas equations with a typical maximum pressure drop of 10%. If you want larger pressure drops, you have to use other equations. Crane Technical Paper No 410 has excellent information for doing this.

 

[BigInch]

NFPA ain't it.

johngerhart are you just needing an equation for diameter and flowrate? If so, you can use any one you like, there's no "standard" equation and no standard for sizing. If you need a flow-diameter-length equation, there is Colebrook-White or a number of others. Some equations have application ranges. Weymouth is for larger diameter lines. There are others for very low pressures (in-water column). Choose a formula that suits your application. I'd suggest Churchill as it works well for any type of flow, laminar, transition or turbulent.

http://virtualpipeline.spaces.msn.com

"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain

 

[PEDARRIN2]

BigInch

NFPA might not apply, but it all depends on where the piping is located. At the pressures he mentioned it probably would not be applicable.

What is the Churchill equation?

I have not seen that one before - just the ones in Crane 410.

 

[BigInch]

Here's a spread that I use for liquids. It should work for gas using specific gravity relative to water, but you'll have to calculate the density and viscosity of the gas at flowing pressures and temp. Then limit the lengths of pipe so the overall pressure drop is less than 10% of inlet pressure, or if you have a long line, break it up into segments where dP < 10% and it should be fine.

I put it at rapidshare. Just follow the steps to download, selecting the free option.

http://rapidshare.com/files/96794990/pipe_churchill.xls.html

http://virtualpipeline.spaces.msn.com

"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain

 

[PEDARRIN2]

Big Inch,

I haven't done a lot of higher pressure or longer pipelines with gases, so forgive my ingnorance.

I understand that as long as the dp<10%, you can assume ideal gas and don't have to be concerned with the change in density of the gas.

But I don't understand why you would break the pipe into segments where the dp<10% just so you can use the same equations.

According to Crane 410, if 10%<dP<40%, you use darcy with the average of the initial and final conditions.

If the dP>40%, you have to use compressible gas equations.

I understand this happens on long pipelines.

What am I missing here?

 

[BigInch]

Crane was written before the advent of spreadsheets. I don't go to 40% unless the gas can be considered very ideal, z ~ 1.0

With spreadsheets its pretty easy to recalculate density and viscosity (using the compressibility factor at average conditions of the segment), so whenever dP >= 10%, I recalculate.

BTW, you do know that the average is not (Pi+Po)/2, right?

http://virtualpipeline.spaces.msn.com

"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain