LPG pipeline is damaged 2

[nesamani05]

We are operating a cross country LPG pipeline system. One above ground spurline of 8'' dia & 60 mtr lenght, is corroded at 72 points.Paint is in damaged condition, when we tried to remove paint, it started leaking.We tried in the blowdown line, so the line is isolated.
Spurline is un-piggable. What could be the best and least cost solution to safely
1) Finding the thickness of the Pipeline.
2) Improving the thickness, wherever required

Any other idea also welcomed.

 

[BigInch]

That's some good paint. Get some more of it. Lots of it and paint that pipe like there is no tomorrow.

So, you have serious corrosion at every 800 mm? Not much hope for that pipeline if you chip off the paint and it leaks. Lay a parallel line and take that one out of service PERMANENTLY, and as quickly as possible.





We are more connected to everyone in the world than we've ever been before, except to the person sitting next to us. Lisa Gansky

 

[blacksmith37]

Pull a poly liner into it. ...Is corrosion internal ot external ?
Replace it with corrosion protected steel pipe (lined and/or coated. OR, depending on pressure replace with FRP pipe.

 

[Duwe6]

It is possible that the U/G portion is OK. Dig some bellholes and give the line a standard evaluation. If the bellholes show possible problems, either add enough pigtraps to smart-pig the line or just replace it.

Just because pipe lasts a long, long time U/G, it is not immortal. Replacements are required from time to time. This may be your time.

See the SanBruno thread # 378-281116

 

[BigInch]

Polyliner works in paint pipe?
I believe he said no pigging was possible, as if that mattered.
I urge you guys to reconsider those answers.

We are more connected to everyone in the world than we've ever been before, except to the person sitting next to us. Lisa Gansky

 

[nesamani05]

Thank you all.

My question is
what is the best NDT method to find the thickness along the pipeline...?

How to improve the thickness, wherever required...?

 

[BigInch]

ultrasonics.

We are more connected to everyone in the world than we've ever been before, except to the person sitting next to us. Lisa Gansky

 

[BigInch]

I do agree with the replacement suggestions, but I think you're kidding yourself with inserts on 60 meters of junk pipe.

If you can't pig it, that's the way I know, except in this case a small wooden hammer might be better. What's your solution?



We are more connected to everyone in the world than we've ever been before, except to the person sitting next to us. Lisa Gansky

 

[hydromarine]

I think on this one I would have no hesitation in replacig this section of line its not a huge amount to replace, and I would be doing this ASAP.

 

[brimmer]

To repeat - ultrasonics best method to determine thickness.
60 m of pipe is not very expensive to replace, just replace it, line is blown down anyway. I want to ask about your statement "Improving the the thickness wherever required". How would you improve the thickness? I am curious to know what you are thinking or what they do in your part of the world?
If you need to reactivate before replacement, put temporary sleeves on leaking or thin sections, watch pressure ratings, though I don't know if your code will allow this.

 

[BigInch]

I thought if he sleeved one, he'd just blow another hole somewhere else.


We are more connected to everyone in the world than we've ever been before, except to the person sitting next to us. Lisa Gansky

 

[dcasto]

you could use a clockspring

http://www.clockspring.com/

 

[Eddycurrentguy]

Clockspring is a great product, but to insure integrity, you would have to apply over the entire to avoid the problem Big Inch mentioned in his post.

Cheaper and less labor intensive to just replace the segment. As a bonus, you might be able to sleep better at night knowing that the line integrity has been restored.

 

[brimmer]

Don't use clocksprings over leaks & only if non-leaking area corrosion <80%.

Nesamani05 - how would you personally improve wall thickness in these areas? What are your thoughts on how to do this?

 

[BigInch]

It's just as important for an engineer to be able to decide when a device reaches the end of its useful life as it is to know how and when to repair it. Making endless repairs on anything is seldom cost effective and often dangerous. I just have a feeling that this is one of those cases.

We are more connected to everyone in the world than we've ever been before, except to the person sitting next to us. Lisa Gansky

 

[Duwe6]

Gotta concur with BigInch on Repair vs. Replacement. It sounds like multiple repairs + constant, vigilant inspection + risk of a catastrophic leak will cost *much* more than just replacing the section.

The problem is, without putting the costs on paper, management always wants to mandate "Repair", because is sounds cheaper than "Replacement". You have to show them the costs for:

Multiple repairs, some of which will overstress adjacent areas and cause further repairs.

Weekly inspections of the thin, rapidly corroding sections, to project when this line will go below the minimum thickness required for pressure.

Calculations of pipe stress of the suspended portions, and the minimum thickness required for structural integrety. Pipe may be thick enough to hold pressure, but too thin to spen the distances between its supports.

And the big one; the cost of insurance for the greatly increased risk of a catastrophic leak. If this area, and everything downwind for 100+ meters, is not "Intrinsic Safe" [no sparks, engines, open motors, etc.] that risk includes a Fuel-Air explosion and fire.

Just replace the pipe.

 

[vpl]

This morning when reading the newspaper I saw the article about the pipeline explosion and fire in Kenya. I don't know where your pipeline is, Nesamani05, but a pipe "held together" by paint is not one that should be repaired.

I vote for replacement.

Patricia Lougheed

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Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.

 

[Duwe6]

Kenya shows what "benign neglect" REALLY costs.

Everything had an End-of-Useful-Life. Ignoring it, or using 'bandaids' when major repairs [or replacement] is required has Major consequences.

 

[ornerynorsk]

Ditto what other posters have answered.

When one begins to wrestle with the supposed pros and cons of whether to repair or replace a piece of transmission line that has become akin to swiss cheese, you've got to do a gutcheck and just come to the realization that it is not an issue of economics or inconveniences. I cringe whenever I hear the phrase "least costly solution to safely . . . ."

If you are the operator or the inspecting authority, you have nothing less than an obligation to decommission immediately and write it up for replacement if you find that the line can no longer be operated safely and repairs would be an exercise in futility.

This is why people die and pipelines explode because people try to justify and rationalize away good common sense. Not trying to lay a guilt trip or be judgemental, it's just that when you're in a position where you know the truth and possible consequences of a situation, and fail to act in your fullest capacity to rectify the situation, you are responsible.

I hope the pipeline is not in my neighbourhood.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[stanweld]

nesamani05,
How did you determine that the pipe is ONLY "corroded at 72 points"? Were they leakage points? Were they seen throughout the 60 m length? If so the whole pipe should be considered scrap and replaced as others have stated.