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Pipelines pressure tes - To be or not to be
2

Pipelines pressure tes - To be or not to be

Pipelines pressure tes - To be or not to be

(OP)
Dear mates,
In some oil fields, vandalization of flowlines is very common, some times is the first cause of leaking, spillage, etc., more than corrosion.
The question come out when repair or sectional replacements, with new and duly certified piping, are to be done, after the welding job is completed the criteria some times is about "golden welds", but when the quantity replaced is bigger, normally hydrotest of the complete lenght of the line should be requested.
But, is right to perform this test when the line was previously in operation and even sometimes its integrity condition is not well known.
So, this is te question, thanks in advance for any input you can have.

RE: Pipelines pressure tes - To be or not to be

The purpose of hydrotesting is to check that the pipeline is mechanically sound and that all welds and pipe are good for the pressure. Replacement of sections is normally undertaken by pressure testing the section prior to tie-in and then have two golden welds. If you are replacing more than one section then a complete pressure test would normally be recomended of the entire line to avoid too many golden welds.

An alternative is to strength test the new section (1.5 X dp or whatever code you use) and then leak test the whole line while you can to Design Pressure or 1.1 x DP to prove the entire section.

If you have concerns about integrity then you should deal with this separately, not as part of a replacement section pressure / leak test. An operating company I used to work for did an annual leak test to Design pressure in product as a way of "proving" integrity in the days before intelligent pigs becam small enough to run in lines < 16", but that is not normally undertaken now. Pressure testing in water is a way of proving integrity at the time of the test, but can weaken pipelines if a small secion has corroded and is plastically deformed, but not enough to rupture.

Only you can determine whether the relative risks and knowledge of the pipeline justify the time and expense of a complete pressure test or not.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

RE: Pipelines pressure tes - To be or not to be

So, the integrity condition of your lines is not well known, and you don't want to perform a hydrotest because really, you don't want to know. Do I have this right?

RE: Pipelines pressure tes - To be or not to be

In a very, very wierd sort of way, it kinda makes sense. Doesn't it?

Independent events are seldomly independent.

RE: Pipelines pressure tes - To be or not to be

BigInch..... I believe that you should sit down with LittleInch and have a talk......... a heart-to-heart about denial

RE: Pipelines pressure tes - To be or not to be

Big bro' - I assume you mean that testing the entire line again sounds weird, but right. I tend to agree. So long as the test doesn't go beyond yield, I can't see a real issue. If it breaks because it is corroded then you should have fixed the corrosion, but at least it has broken in water and not product.

MJCronin - sorry but can you explain what we're supposed to be in denial about?

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

RE: Pipelines pressure tes - To be or not to be

(OP)
Brimmer,please read again my thread, you are making affirmations, what I didn't.
My question should be, why to penalize the entire lenght of the flowline, which was in operation before, by making a pressure test, when just a portion of it was replaced by duly certified pipes and the welds joints released as a golden welds.

RE: Pipelines pressure tes - To be or not to be

evaristo,
You were the one who made the comment regarding hydrotesting the whole line and you also noted the integrity may be unknown.
Are you the contractor or the owner of this pipeline ?
If you are the contractor you are probably not concerned with the integrity of the remainder of the pipeline.
If you are the owner of the pipeline you should most certainly be concerned with the integrity.
Both Big Inch and Little Inch make valid points.
As far as I am aware there is no code requirement anywhere that states you must test the complete line if you replace 1, 10 or 100 lengths of pipe.
Perform NDT on all welds, hydrotest the replacement section or sections,remove the end caps, install the section or sections, NDT the two golden welds and then place the line back in service.
As Little Inch noted, Pressure testing the whole line to DP with product to determine integrity is one way of doing it but as also mentioned smart pigs now make that practice pretty much redundant.
Cheers,
Dek Dee

RE: Pipelines pressure tes - To be or not to be

I was simply commenting philosophically on the fact that, if he hydrotests 10 m, 20 m, 100 m, or X m, in a system, say involving 100 X meters, or whatever, amount of pipe in which he has no faith in it's integrity what so ever, testing X meters here and now doesn't really accomplish much in the global framework of things.

Independent events are seldomly independent.

RE: Pipelines pressure tes - To be or not to be

(OP)
DekDee, your remark about "as far as I'm aware ...", was the point I was trying to put in the table, doesn't matter contractor or owner, in my company have other specific methods to check the integrity of the line (intelligent pigging, etc.), it was not the point, but the release criteria to be used after any sectional sectional replacement is done.

RE: Pipelines pressure tes - To be or not to be

2
You used the word yourself, "penalize" the rest of the flowline. You don't want to make a hydrotest of the entire line because you don't know the integrity of the line and you are afraid of a hydrotest failure.

"But, is right to perform this test when the line was previously in operation and even sometimes its integrity condition is not well known." Is it "right"? It is not right or wrong. Pipeline companies make "maintenance" hydrotests all the time as a way to verify the integrity of the line, at that moment, ususally when other options are not avaialable, or to get it operating again after a failure, etc. So yes, operators are hydrotesting lines previously in operation all the time. Hydrotests are not just for commissioning new pipe.

If you don't want to hydrotest the entire line, I don't see what the issue is with hydrotesting the spools prior to installation and then completing full NDT of the golden welds? You may not have to hydrotest, assuming the regulations where you are would be similar to others.

I don't understand how you would be "penalizing" the line, my opinion is that you would not be "penalizing" the rest of the flowline, but helping it. If this scenario came up for me, I would welcome a hydrotest when the integrity condition of the line is unknown. It would demonstrate at least the line can hold a certain pressure today, which is more information than you had before. You can also use the pressure test data to back calculate the size of a remaining anomaly etc. and use this information to help with the integrity assessment moving forward. I don't know why you would want to risk having a product failure as opposed to a hydrotest failure? It is a lot easier to deal with a hydrotest failure from a regualroty perspective than a product failure, at least you can say you were completing some due diligence on the line, whereas before it was a case of neglect.

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