We have a gas pipeline with internal epoxy coating. If methanol swabbing as a drying technique is used could this potentially damage the internal coating?
The gas pipeline is internally coated for hydrauic effeciency? How is that working out for you? How much hp do you figure you are saving? Do the pressure drops match your model? How did you ensure full coating on the weld joints?
When I've done those calculations, the economics have always been on the wrong side of marginal (disregrarding corrosion benefits). I've always found that I got at least an order of magnitude better effeciency from pigging than I got from reducing the surface roughness of the pipe. I'd be really interested to hear more about this application.
Even REALLY REALLY long, if the internal coating reduces your pressure drop from 5 psi/mile to 4.96 psi/mile you are not going to reduce your number of compressor stations very much. That is the kind of changes my modeling suggested.
Sorry. I meant really, really, really, really long.
I've never used epoxy coating for roughness reduction either. That's why I thought it was for corrosion.
I think its probably more like some entity within or near the project that has an interest in using epoxy. You'd be surprized what that kind of pipeline you can wind up with when there are "other considerations" to meet. Remember the story about the blind man meeting an elephant.
"I am sure it can be done. I've seen it on the internet." BigInch's favorite client.
Check out Novembers 'World Pipelines'issue. Article by 3M claims internal coatings increase capacity by 14 - 21%. A 1% improvement in throughput provides the financial justification.
And what fluid, and what temperature, and what viscosity? I don't think that 3M would lie, but I'm pretty sure they would structure their experiments to present their expensive product in the best possible light. I can see those sorts of numbers if you are pumping cryogenic toothpaste, but ground-temp natural gas ain't going to come close to double digit percent improvement (problably won't make integer percent improvements).
Just curious, are you internally coating the joints also? Reason I ask is I am on a project at the moment where the owner has internally coated pipe (epoxy) and is not internal joint coating.
Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:
Sorry to piecemeal, but we are in the process of hydro testing the onshore portions and will be using methanol slugs. We checked with our vendor and no issues with the epoxy, however, you might want to check the valve vendor to make sure the seals are okay with methanol - outside chance, but worth ticking the box.
Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:
methanol doesn't dry pipelines. The water will still be in pipeline. The methanol will prevent hydrating. Big caution here, when you bring the line on, you WILL be offspec for water and most pipeline moisture analyzers detect methanol as water. You'll be lucky to have under 20 pounds H2O/mmscfd reading.
dcasto,
I wondered about that. I didn't know of any "drying" properties of methanol, but there are SO many things I don't know that I kept that one to myself.
If by "drying" he meant to remove liquid water, I don't know of anything that will chemically do that. You could pump in anhydrous ammonia and boil it, but that's pretty exciting and the exhausted gas might spoil your day.
I just assumed it was not translated correctly and he really wanted to prevent hydrate formation. Adding any liquid isn't really going to dry the thing.
"I am sure it can be done. I've seen it on the internet." BigInch's favorite client.
Basically, the existing national transmission system we are working with has internal liquid epoxy lining 40 microns. We are tie-ing in to the system over a relatively short distance and see no benefit of having the coating. The question was raised as it's possible that the operator would specify internal coating as thats what he knows. In this case methanol drying may/ may not be appropriate. I intend to propose desiccant air drying as its always worked for me.
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