NG pipeline packing calculation improve
NG pipeline packing calculation improve
(OP)
Hi Everybody:
I would like to know about Linepack calculation, In 408 km natural gas pipeline 34 inches in diameter, there are stations every 30 Km with PT's and TT's, I did the calculation in segments, I would like to improve this standar volume calculation adding gas composition.
Thanks in advance
I would like to know about Linepack calculation, In 408 km natural gas pipeline 34 inches in diameter, there are stations every 30 Km with PT's and TT's, I did the calculation in segments, I would like to improve this standar volume calculation adding gas composition.
Thanks in advance





RE: NG pipeline packing calculation improve
When I've done line pack calcs I:
1. Determined the total volume of the pipe
2. Assumed that my lowest allowable compressor suction pressure was the "line pack pressure"
3. Determined the gas density at the line pack pressure
4. Multiplied the gas density times the volume determined in #1 to get mass.
5. Divided the mass by the density of the gas at the contract STP to get volume at standard conditions. The answer is line pack.
Breaking the line into segments is a waste of time since that is only useful in dynamic calcs like compressor performance or fluid friction. Line Pack is a static calculation.
David
RE: NG pipeline packing calculation improve
I'd use the average gas pressure in each segment, if each were "short", and note that average pressure is not (P1+P2)/2, but more closely follows,
Pavg = 2/3 * (P1 + P2 - (P1 * P2)/(P1 + P2))
Then calculate the compressibility using that pressure and the average temperature (T1+T2)/2
Pressures and temperatures must be absolute.
Just to see if I've been wasting my time talking about this, take only 1 segment of 408 km and using the max and min pressures, calculate the line pack. Then calculate it again using each of your segments and tell us what the difference is. I think you'll easily have a difference of 10% or more.
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"The problem isn't finding the solution, its trying to get to the real question." BigInch
http://virtualpipeline.spaces.live.com/
RE: NG pipeline packing calculation improve
I'm not sure we have the same definition of line pack. The definition that I've always used is the amount of gas that must be present in the line to begin operations. It sounds like you are talking about the amount of gas that is in the line for steady state operations.
With my definition, if every compressor station has the same minimum suction pressure then that pressure represents the minimum amount of gas that must be present to begin operations. If the various compressors have different minimum suction pressures then you have to treat each segment upstream of a compressor as its own line pack.
With the other definition you must use segments and average pressures. Typically you would start with compressor discharge and run the segment to compressor suction. If outlet is less than 90% of inlet, then the segment is too big and should be further reduced so you get a meaningful compressibility.
David
RE: NG pipeline packing calculation improve
RE: NG pipeline packing calculation improve
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"The problem isn't finding the solution, its trying to get to the real question." BigInch
http://virtualpipeline.spaces.live.com/
RE: NG pipeline packing calculation improve
David, I assumed 100% of Methane density, I have the compossition now and I've found this for Z-Factor Calculation:
http://w
How is your Density Calculation?
Biginch, the diference is 2.5% without segments, I would like to know about your compressibility calculation.
Thanks!
RE: NG pipeline packing calculation improve
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"The problem isn't finding the solution, its trying to get to the real question." BigInch
http://virtualpipeline.spaces.live.com/
RE: NG pipeline packing calculation improve
Best regards
Morten
RE: NG pipeline packing calculation improve
Thanks in advance.
RE: NG pipeline packing calculation improve
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For determining density see, http://en.wikipedia.org/wiki/Equation_of_state
Any one of these will do for starters 4.1, 4.2, 4.3, 4.4
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"The problem isn't finding the solution, its trying to get to the real question." BigInch
http://virtualpipeline.spaces.live.com/
RE: NG pipeline packing calculation improve
Tc =169.01+314.001*Spgr
Pc = 708.75-57.5*Spgr
Pr = PSIA / Pc
Tr = T rankin / Tc
z = 1 + (0.0703 *Pr / Tr) * (1 - 6 / Tr ^ 2)