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TOPIC: Two-phase flow

13 years 2 weeks ago #8736

  • don_okotoks
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I'm laying out a plant and pipe rack and am faced with several lines indicated on PIDs as two-phase flow. The two-phase is shown to exist after going through a heat exchanger and continues on through three stages of separation where the vapours and liquids are piped to flare and storage respectively.
Are there certain piping considerations that I should be aware of for this type of system?
Don

Don, Considering the little information you 13 years 2 weeks ago #3793

  • Jop
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Don,
Considering the little information you have given us I will try.
First- if possible make sure that the line(s) from the heat source to the separation vessel continues to step up and is not pocketed.
Second- This may also be one of the places you would want to consider sloping these lines up in the direction of flow.
Do it once and Do it Right

Its hard to visualize your 13 years 2 weeks ago #3794

  • hc
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Its hard to visualize your situation.
It sounds like the heat exchanger is a line heater off a wellhead to a 3 phase separator (separating gas/oil/water). The water is metered and sent to a storage tank and the gas/oil is metered and put back together and sent down a pipeline to somewhere. The vapours are the PSV off the separator. Sorry dude.....but it sounds like your laying out a wellsite. Is that correct. I need more info.

How's life in Calgary? I just left there 6 months ago. Way to retarded for me. I would have road raged and killed someone sooner or later.

two-phase flow 13 years 2 weeks ago #3795

  • don_okotoks
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Jop and hc,
Sorry for lack of info. A little new to this concept of forums.
Yes, coming from a wellhead, the facility is to separate the oil from the muli-phase fluid, recover the vapours for re-injection and send the oil to storage.
The multi-phase comes from wellhead>inlet heater>inlet sep and is then pumped through another heater>hp sep>lp sep>vertical gas boot. All along the way (except at hp sep) the vapours are sent to compression for re-injection. The oil is sent to storage.
My question, more specifically I guess, is/was should the line carrying the multi-phase be sloped and/or not pocketed. Jop, you have basically answered that (even with the little info I gave). I will probably have to go back and forth across a central rack (up to rack>over and back down into equipment). As long as the line(s) are drainable back to major equipment would this be cause for great concern?

hc ... calgary is hoppin' (as you know).
Don

Don, I think you will have 13 years 2 weeks ago #3796

  • Jop
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Don,
I think you will have problems if you "High Point" the line over the pipe way the same as if you were to "Pocket" the line between the heater and the separator.
High Pointing may cause the accumulation of vapors in the high part of the line until the liquid "burps" over.

Low pointing (or pocketing) the line may tend to cause a slug of liquid in the pocket until the gas builds up enough pressure to "burp" a bubble through the pocket.

Either way this is not a good start.

You should do all you can to make this system "step" up in elevation from the heater to the separator.
Regards,
Jop
Do it once and Do it Right

Your emulsion from the wellhead 13 years 2 weeks ago #3797

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Your emulsion from the wellhead is at a pretty high pressure. Prolly 2500#1500, 900# after the PCV. Based on my experience with wellsite design and what I'm visuallizing your project to look like high points are not an issue. I'd avoid pockets and keep your piping so that it drains into the equip and has no place to sit and freeze in those cold Alberta winters. Like Jop says step it up. I've never sloped my high line piping that I can remember. Alot of the time Separator inlet connections are pretty high compared to your wellhead piping and you never truely know the real life elevations of your wellhead conn's. We always used a standard. Your worrying to much about the gas vapours also on the upstream side of the separator. They're mixed in a slurry with gas and oil called emulsion. Not an issue until after the separator.
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