6 replies to this topic

[ma7ersi]

Hi,

 

Below, in green, is a request that I  got from a client:

 

Line packing: pipeline to be considered as a buffer, time sufficient to fill the pipeline to MOP, to be determined; during start up, gas flow from pipeline outlet will be used as a fuel gas for the equipment (2500 Nm3 per hour), time to be determine for the consumption till pressure equalization from pipeline both ends.

 

Can someone help me to understand this request.

 

Regards,

 

[Pilesar]

Ask the client to translate that sentence into English. I think the question is 'how long will it take to bring the line up to operating pressure while simultaneously withdrawing gas at a fixed amount?' Make a guess at what you think is meant including all necessary assumptions for a complete design basis and send it to the client for written confirmation.

[ma7ersi]

Ask the client to translate that sentence into English. I think the question is 'how long will it take to bring the line up to operating pressure while simultaneously withdrawing gas at a fixed amount?' Make a guess at what you think is meant including all necessary assumptions for a complete design basis and send it to the client for written confirmation.

 

Many thanks Pilesar

[ma7ersi]

Hi Pilesar,

 

Can you please advise if the below calculation makes sense?

 

Inputs:

 

MOP=28 bar

T=45°C

Q (pipeline inlet)=25000 NCMH

Withdrawal Gas Flow =2500 NCMH

Pipeline length / diameter= 94 km / 12"

 

In order to calculate the line pack volume, i used the following formula:

 

Variable Description

LP

Calculated natural gas volume (in MCF) in a pipeline segment; the line pack.

T_b

Base temperature (in degrees Rankine) for line pack. The base temperature is specified as a system input (not per pack segment), but is user-configurable. The default value is 60° F, or 519.67° Rankine.

T_av

Average flowing temperature (in degrees Rankine) in the pipeline segment. See Average Temperature below.

P_av

Average pressure (in psia) in the pipeline segment. See Average Pressure below.

P_b

Base pressure (in psia) for line pack. The base pressure is specified as a system input (not per pack segment), but is user-configurable. The default value is 14.73 PSIA.

V_seg

Volume (in MCF) of the pipeline segment based either on the segment’s configured length and diameter or a user-configured volume. See Pipe Volume below.

F_pv

Supercompressibility factor for the pipeline segment. The supercompressibility factor is user-configurable for each pipeline segment. See Supercompressibility Factor below.

C_f

Volume correction (conversion) factor. The correction factor is user-configurable for each pipeline segment.

 

Results:

 

LP=185 MCM

 

Time = 185000/(25000-2500)= 8.22 hours

 

Regards,

Edited by ma7ersi, 19 April 2022 - 06:54 AM.

[Pilesar]

I don't do many pipeline calcs and I've never seen that line pack equation before. If I were the client given this, I would say 'it looks like that engineer knows what he is doing' and I would be happy. I think that if later it actually took 24 hours to pack the line, no one would really care what these calcs show. There is not a safety consequence and you cannot speed up the actual packing time with your calculations, so this seems just a planning estimate. Congratulations.

[breizh]

Hi,

take a look at this link , there are  examples covering the topic.

http://marineman.ir/...-Press-2005.pdf

 

Page 132 

 

Good luck

Breizh 

[ma7ersi]

Thank you Pilesar and Breizh