Internally Coated pipe Repairing Techniques

[GustavoR]

Hello Everyone;
In our company, O&G Exploration and Production, we use internally coated injection water lines for Secondary Recovery. These lines range from 6 to 12 inches in diameter and have been in service for more than 10 years. The system handles highly corrosive and scale forming fluid. In addition to process chemicals, biocide and scale preventing products are incorporated into the system. However, no corrosion inhibition is in place at the moment. We have been experiencing recurring pipe failures related to internal corrosion during the last year and a half more or less. These failures are in part related to the previously described circumstances and to badly performed repairs (e.g. patching) in the past. Although we are in the process of developing an Integrity Management System for these lines, we are at the same time concerned with the fact of performing sound repairs from now on, to avoid or at least mitigate the high rate of failures, as the complete replacement of the lines is not an option. As the pipes are internally coated, we may not use traditional repairs in the form of metal sleeves which require welding. As my experience in repairing techniques is limited, i researched the current status of repair systems and three alternatives appear to be appropriate for this case:
a.Composite cold repairing systems.
b.Complete replacement of the damaged segment by installing new pipe using internal sleeves at welded joints.
c.Polymer internally filled Bolted Clamps.

As all three systems appear to have their pro and con’s comparing technical and cost-effectiveness points of view, I would very much appreciate your comments and suggestions regarding the aforementioned techniques or any other you have applied successfully in the field.
Thank you.

 

[SJones]

Think about this: the pipelines are failing from internal corrosion and options a and c are repairs from the outside. So, you make the repairs and, 3 months later, lo and behold another leak right next to your grouted sleeve! Option b will give the highest reliability repair; but, until there is focus on treating the cause rather than the symptoms, the replacement material will go the same way. Since the injection is for recovery, there is a risk that corrosion inhibitors could impair injectivity. Assuming that it's onshore, that operating conditions are not beyond polyethylene and the rest of the pipe has sufficient pressure retention, think hard about PE lining the pipelines as the repair/corrosion control option.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[GustavoR]

SJones, thank you for your reply. The option of polyethylene lining was among the considered alternatives at first. We ruled it out because:
_The HDPE Liner Contractor advised us that, as the pipelines have internal sleeves for coating protection at welded joints, these sleeves created strained points for the liner which could lead to failure by collapsing.
_The lines present significant scaling and deposits which make the internal bore cleaning (previous to liner installation) very difficult and costly.
_At the same time the presence of internal sleeves make difficult the passage of the cleaning pig.
Have you had any experience regarding these points?

Consequently, the composite sleeves and bolt-on clamps were later considered as options. I agree with your comment in regard to the corrosion process to continue degrading the pipe internal wall, more so if no inhibition is present. But these two alternatives were considered as a substitute for the Type B Pressure Containing Sleeve, which was out of the question because it requires welding. We expect at a near future to determine the root causes of this failures (as a part of our in-progress Integrity Management Program) and be able to implement mitigation and monitoring measures.

Although ASME B31.4 precludes the use of composite sleeves for repairing leaking defects, a more recent publication (ASME PCC2) establishes the applicability of the technique provided some design conditions are met. Bolt-on Clamps are permitted to repair leaks according to both standards. In both cases, internal corrosion defects (either leaking or non-leaking) are included under the corresponding repair technique. These aspects were what led me to consider these as possible choices (keeping in mind the mid term application of mitigating actions), in spite of the fact of the corrosion advance as you pointed out.
In addition it is very true what you observe about new failures occurring next to a previously repaired section. In fact, it has been frequently (and painfully) happening near to patches installed not too long ago. Because patches are considered as temporary repairs by standards (and have to be welded), I thought of using these permanent-non-welding techniques, instead.
Thank you again.

 

[SJones]

The pipeline construction is clearer now and the PE lining contractor's view on the use of the internal Thru-Kote weld sleeves and pipe wall cleanliness is absolutely correct. I have had experience with internally coated pipelines such that we set a maximum pipeline design life of 10 years which runs coincident with what you are experiencing. Looking at your scenario, if the HSE risks of leaks are tolerable, it would appear that the only course is to keep up clamp type repairs until either there is nothing left to repair or somebody does the economics to examine the value of complete pipeline replacement with the correct corrosion control option.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[GustavoR]

OK, thank you very much!