Pressure drop at pipe damage 1

[Dario2002]

Is there any resource how to estimate preasure drop when gas line gets some damage (hole, pinhole, gilotine, large hole) ?

Ex.
Pipe line with natural gas at 30 bar. Length cca 10 km.
Which hole size is neccesery to have preassure drop of 1 bar/min.
Or vice versa: for some hole (type) how much is pressure drop.

 

[Dario2002]

Diameter of pipe in example above should be 20"

 

[BigInch]

The easy way is to assume the pipe is a closed container with Vol = pipe segment volume, Pressure = P1, Temp = T1.
Decrease the volume by a given amount, dV
Calculate the new pressure using P2=ZRT2/T1/(V1-dV)
That's the pressure drop you will experience over the time it takes to lose volume dV. If the line is flowing, you will have to add the gas going into the segment and subtract the gas leaving the segment.

You can then correlate that leak flowrate to an equivalent hole diameter using a thorough an orifice equation with P2 on the inside and atmospheric pressure on the outside.

The easier way is to use a gas transient program and simulate various leak rates and watch the actual pressure drops you'll get for each one.

Going the Big Inch!

http://virtualpipeline.spaces.msn.com

 

[Dario2002]

Thank You for reply BigInch.

The first part I understand.

The other part with "equivalent hole diameter" and "orifice equation" I have problem right now. Can You point me on some page or other resource (not paper books) for help on this calculations.

Or even better, "gas transient program" recomendation (possibly small for donwload).

 

[BigInch]

Gas Leak Flow

http://www.air-dispersion.com/feature2.html

Going the Big Inch!

http://virtualpipeline.spaces.msn.com