LPG Pipeline flush w/ Water

[BCG1]

In an application, we are planning to flush 891 bbls (37,414 gallons) of LPG through a 10" pipeline using water. Our initial investigation indicates that we will need roughly 500 psig discharge pressure to achieve the desired 150-180 psig downstream pressure. To inject water, we hope to utilize a a pumper truck that can flow up to 550 gpm. Our ultimate goal is to cut-into the line to do hot work. We determined that flushing is our preferrable option in lieu of stoppling, and unfortunately the line is not currently piggable. Flaring doesn't work for our timeframe either.

There is one area on the line where we have an elevation change due to a river crossing, but otherwise it's relatively flat. Also, there is minimal dead legs -maybe one 10' section.

My question is, what guideline can we follow to ensure that we get a complete flush of the LPG? We don't want to flow a huge amount of excess water through there if possible. Our procedure includes cracking a downstream bleeder to monitor LPG levels until acheiving 0% LPG. We'd have to move to a contingency plan if water injection volumes get excessive.

My initial thought is to ensure a turbulent flow throughout the flush. I have been told this would help prevent hydro-skimming and any residual LPG. I'm not a hydraulics guy but hoping that someone out there may have some experience performing this type of procedure.

Thanks,
BCG

 

[dcasto]

Then, how do you get the water out? I'd use a nitrogen from LIN through a pump truck and vaporizer. a small bob tail load and you inerted the line, so a safe cutting atmosphere, it'll be dry and clean, no rust or water, and no environmental disposal problems.

 

[gr2vessels]

BCG1,
Do you mean displacing the LPG with 37,414 gallons of water?? In 2 miles of pipe?
Surely you should have some isolation valves for sections of that pipe, don't you? Please note that there are many specialised people for your "hot-tapping" job, ask them also. You'll be surprised..All the water they'll use will be to damp some cleaning cloth.
cheers,
gr2vessels