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Slurry Pipeline Repair 1

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ianmcdz

ianmcdz

Mechanical
Sep 19, 2009
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Hello,

Has anybody repaired a slurry pipeline with an external Fibreglass or Carbon fibre wrap? How did they hold up? The slurry is water with some sand in it.

How do carbon fibre/ Fibreglass work in an erosive service? Would they hole through extremely quickly?

Thanks
 
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How long is a piece of string?

Assuming the repair is sufficient for pressure, actual erosion rates depend on the abrasiveness of the slurry material, amount of abrasive material, flowrate and impingement velocities against the wall. I might expect better performance, if the repair was only on the top of the pipeline too. If those possible effects are limited, long term repair could be possible, if not , well then, of course.. no.

It would also help if you could be more specific. The term "some" is quite subjective, which I would usually consider would present little cause to worry about without specific knowledge of application. If you said 700 kg/m3 at 10 m/s, I'd worry a whole lot more.

In any case, repair of a steel pipeline with fiberglass material I would not generally assume would be adequate for anything more than a quick fix, very temporary repair, to be "put right" at the first available opportunity, and I do mean "first", not waiting for next scheduled maintenance period, but more like the very next time that a semi-emergency shutdown could be fit into the schedule. The urgency of correcting the repair might be decided based on the monetary amount of damage or loss of sales that might result if such a repair failed again.

"I am sure it can be done. I've seen it on the internet." BigInch's favorite client.

"Being GREEN isn't easy." Kermit[frog]
 
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Lets assume 2 situations:

1. It's a slurry so there's a lot of sand. I don't know the concentrations but if flow velocity decreases the line will quickly sand out (fill up with sand). We pump just above the settling velocity of say 2.5-3.5 m/s. Low pressure - 500 - 1000 kPa.

2. The water recovered from the slurry. There's a very small amount of fine sand but a higher velocity, say 7 m/s and the same pressure of 500-1000 kPa. Could this pipeline be permanently repaired with an external wrap type patch? The damage mechanism we usually see in these pipes is corrosion-erosion, the pipe pits which creates an eddy with higher velocity which leads to self amplifying erosion.

Thanks
 
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corrosion-erosion is a chicken vs egg phenomenon. Typcially an abrasive removes a fine coating of rust that has formed on uncoated steel, which allows initial corrosion to progress to the point of creating turublence and deepens the pit.

I think you'd likely be able to stop corrosion due to the noncorrosive material used, but at the same time increase the likelyhood of erosion since grp is considerably softer than steel. You have to answer the question of why grp wasn't used to begin with. I would assume it was not used because of its relative softness and shorter lifespana in that kind of environment when compared with steel.

7 m/s is likely to cause erosion with only a relatively very small amount of fines. If you were down at 3 m/s, your chances for successful avoidance would be much better, but you could still see some, probably at changes of direction and at fittings and valves.

"I am sure it can be done. I've seen it on the internet." BigInch's favorite client.

"Being GREEN isn't easy." Kermit[frog]
 
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Thanks for the response

Any ideas on how a fiberglass wrap or epoxy repair would fare in these two situations? We want to hit our maintenance interval without shutting down...

 
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When's the next scheduled shutdown? Assuming a reasonable repair, constant pressures well under grp allowable, 7 m/s, little fines, I think (well... really just a guess) I'd be willing to give lasting up to 6 months around 95%, a year 90%, 2 years 50%, 3 years 25%, 5 years 10%. Warning: a lot of factors could affect that, temperature ranges, differential coefficients of contraction, surge pressures, possible consequential damages ...

Best way is to try it and keep your eye on it on a regular basis to note any early signs of failure.

"I am sure it can be done. I've seen it on the internet." BigInch's favorite client.

"Being GREEN isn't easy." Kermit[frog]
 
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Our next shut down is in April or May. I forgot to mention that the temperature goes down to -50C in the winter the water return is insulated and heat traced but the slurry line is bare pipe. The operating temperature is usually 30-50C but there could certainly be a case where the line is drained during the winter.
 
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I have no idea if grp is suitable for -50C and if it was, certainly the differential expansion coefficent would be significant enough to cause some sort of trouble. Draining the line would probably lower the temperature of the pipe. It sounds like a good idea to have a permanent repair made before winter.

"I am sure it can be done. I've seen it on the internet." BigInch's favorite client.

"Being GREEN isn't easy." Kermit[frog]
 
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Not claiming much experience in this specific field, but just curious what is size of piping, what kind of joining, what pressure/flow conditions, and is pipe aboveground (either flat on the ground, or on what kind supports etc.) or underground?
 
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30" XS pipe
175 psi
Above ground (40' up) it is supported by pipe shoes and load pads for the section in question
CS A106B
 
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Have you thought about a piece of PolyPipe? Chainsaw it into a half-round and strap it on. Or maybe a 90 or 120 deg arc is all you need.

You can even go more than 180 deg and pry it open a little. If it's real thick wall, you can't pry it much though, so you can't get up to like 270 deg arc or anything. Well I guess if you're real slick you could soften it by heating and get it open that way.

You can buy pre-cut patch segments, but we always had pieces of old pipe lying around.
 
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I found out yesterday that we only have inspection data for two locations 85 meters apart in this line. Both UT readings in these locations were bad - which lead operations to conclude that we need to replace the whole section. I'm not going to get too excited until I get more inspection data.

Frozen waterfalls are very beautiful - we could even chip some ice sculptures for added atmosphere. Then again if it were cold enough it might just steam off. Sometimes colder is better!
 
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Hard particle erosion and erosion-corrosion is sometimes better solved with softer, more resilient nonmetallic materials rather than harder metallic ones. Sand/water slurries can sometimes be handled in rubber-lined pipe for instance. As hokey as it sounds, you may be better off with a layer of a rubber material compatible with your process, overlain by a structural patch of steel. A gigantic split Fernco coupling, after a fashion.

-50 C outside? Might this be an oilsands operation? The presence of any residual bitumen or other oil materials in that slurry would be important info toward understanding the failure, designing a solution and selecting correct materials.
 
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No failure yet :). We have had some success with neoprene lining. Part of the problem was water quality changes. My goal is to find out if I can have a permanent fix installed from the outside without a shut down for a long section of line. I have been hearing that it is possible for a permanent fix using wrap type repairs only if the damage is on the outside of the pipe.

As to understanding the damage it is very complex due to a couple of changes in our water chemistry. Right now the fluid is pretty clean water with a touch of fine sand.
 
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"I have been hearing that it is possible for a permanent fix using wrap type repairs only if the damage is on the outside of the pipe."

yeah . . . think about it. Once you've lost integrity on the ID, it will just keep going through the pipe wall. A wrap type repair is generally intended to shore up the existing material, not completely replace its purpose.

What is your current pipe material?
 
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Obviously you aren’t addressing the root cause with an external repair. We're talking about hitting maintenance intervals here to avoid shutdowns.

You've got some fog on your end too eh?

We've actually strayed far from my original question on slurry pipeline repairs - In some locations in our plant a pipe that lasts 3 months is considered old. Where we see velocity increases, direction changes, or turbulence pipes wear out period. I was hoping that somebody would offer some kind of grout/cement repair that is set around the pipe that we could certify (With proper engineering calcs) for our low pressure situation. Our materials perform well for the service, but like anything else when you're talking about a huge quantity of pipe there are going to be some manufacturing defects which lead faster erosion....
 
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