Reinforcements and Repairs on a Long Transmission Pipeline

Background

One of the Chinese pipeline operators owns the first long transmission pipeline for petroleum products transmission in China. The entire pipeline extends over 1250km. The pipeline material is X60 and X52 steel. The maximum elevation of the pipeline is 2268.3m. The designed operating pressure of the pipeline is 1500psi. The designed annual average transmission amount is 5 million T of petroleum products. It has been 14 years since the pipeline was first constructed and put into services in 2002. In 2013, the operator of this pipeline contracted with GE PII Pipeline Solutions and performed intelligent pigging along the pipeline. As a number of internal and external corrosion defects and manufacturing defects were identified and evaluated, the operator decided to perform a series of pipeline repair operations from 2013 to eliminate the potential consequences if the pipeline fails. In 2016, a project was decided to treat the K511 section of this pipeline for defects reinforcements and repairs.

It is well accepted nowadays that composite repairs are the most efficient pipeline reinforcement and repair methods for corrosion defected pipeline in terms of costs and performances. There are several established solutions using composite material within the industry.

Solutions	Advantages	Disadvantages
Traditional wet wrap composite repair	1. Relatively cheap 2. Easy to apply 3. Flexible to be applied on all kinds of elbows, flanges or special structures of a pipeline 4. Flexible in stock. For contingency use, one wet warp composite system can be applied onto a pipeline with a different size rather than its designed one	1. The repair performance is highly affected by external factors, i.e. the operating environment; the skills of the installers. The weight ratio between the fiber cloth and the adhesive is nearly impossible to be consistent between installations. 2. The field installation quality of traditional wet wrap composite is hence difficult to be controlled
Full cure composite repair	1. Easy to apply 2. The composite material and adhesive were combined in the factory as a prefabricated standard product, which improves the installation reliability of the product	1. Cannot be applied onto the special structures like elbows or flanges. 2. Lack of stock flexibility. One specification needs to be strictly applied onto pipelines with its designed size.

Challenges

The K551 section of the pipeline is approximately 400km. This section of the pipeline passes through several towns and villages with dense population. The topography along this section is very complex with tightly spread forests, wheat farms, hills and several tunnels. 26 defects were identified along the K551 section, 17 of them require pipeline reinforcements, and most of them were located inside areas with frequent human activities. The main challenges of this project are summarized as below,

1. Due to the downturn of the oil and gas industry, the operator had a very tight budget to perform this project. Cost efficient solutions were strongly wanted.
2. As the K551 section passes a large number of high consequence zones, the requirement for the reinforcements and repair performance was very strict. The solution hence was deemed to be both strong in mechanical properties and stable in installation performances.
3. To minimize the interference with the frequent local human activities, the project was designed to be done within a tight time frame.
4. The pipeline was transmitting a considerable amount of petroleum products daily to supply the nearby urban consumptions, it would be impractical to shut down the pipeline while perform all the designed repairs and reinforcements.
5. There were not only straight pipes, but several elbows to be reinforcements in this project.

Solutions

In order to meet all the challenges presenting in this project, the solution needs to satisfy a variety of criteria. The solution needs to be reliable while cheap; the solution needs to be quick to deploy to minimize the operation time; the solution needs to be flexible for different pipeline structures and consistent in performance under various operating conditions. None of the traditional solutions can satisfy all those criteria as mentioned.

Eventually, the Deyuan vacuum composite, Innovative Deyuan Wrap, was selected for application. Innovative Deyuan Wrap is a patented product developed by Deyuan Petroleum & Gas Engineering Co.,Ltd. It is the world’s first vacuum composite system. It is fully compliant with ASME PCC-2 and ISO-24817 standards. Innovative Deyuan Wrap is essentially a type of wet wrap, while the composite fiber cloth is rolled and sealed in a specifically designed vacuum bag as a standardized product prefabricated in the workshop (Figure Gallery 1). The operators may simply take the prefabricated Deyuan Wrap to the site; connect the vacuum composite kit to the vacuum pump. Under the effect of vacuum negative pressure, the fiber cloth will be fully impregnated by the mixed adhesive automatically. During the process, the embedded air, even the smallest bubbles, in the fiber cloth will be squeezed out. The entire process takes only 5-8 minute. It will not be affected by any of those external factors such as the ambient temperature, the working conditions or the operators’ skills.

The on-site installation performance of Deyuan Wrap is therefore with remarkable stability, great consistency, and exceptional mechanical properties. It is also highly aligned with the laboratory tested result. The operators only need to wrap the soaked fiber cloth onto the defective pipeline to complete the installation. Deyuan Wrap retains the advantages of the traditional Wetwrap technique which is highly flexible. Deyuan Wrap can be applied onto elbows, tees with different diameters. Meantime, Deyuan Wrap is as reliable as Full cure technique which makes the repair quality strictly guaranteed.

Results

As per the pipeline operator’s plan, pipeline reinforcements were done on 17 defects along the K511 section. The section pipeline OD is 12 inch, and based on the defect severity, all those 17 defects were applied with 4 layers of 300mm width Innovative Deyuan Wrap for effective repairs. Glass fiber cloth was used for its good performance in insulation, heat and corrosion resistance and mechanical strength.

100% of the repairs have passed the post job inspection conducted by the operator. 95% of the repairs were evaluated as excellent during the operation quality categorization. Particularly, with Innovative Deyuan Wrap system, the impregnation processes for all 17 repairs were less than 6 minutes from the point when the adhesive was fully mixed to the point the fiber cloth was fully soaked. The visual inspection on the soaked fiber cloth proved that the impregnation process was very stable. Even with the amateur filed workers, a thorough impregnation could be achieved within the given time frame (Figure Gallery 2).

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Summary & Conclusion

This project is a typical application of the Innovative Deyuan Wrap. The project proved that the vacuum approach Deyuan Wrap takes is a cutting-age approach which brings a new and improved option to pipeline reinforcements and repairs.

Innovative Deyuan Wrap is unique comparing to those well established traditional composite approaches. The comparison is shown as in Table 2.

Solution	Traditional wet wrap composite repair	Full cure composite repair	Innovative Deyuan Wrap composite repair
Cheap	√		√
No weld need	√	√	√
No system shut down/No reduce pressure	√	√	√
Application flexibility (elbows,etc)	√		√
Stock flexibility	√		√
Easiness of installation			√
Performance consistency		√	√
Minimum external factor influence		√	√
Shortest operation time			√

As the first vacuum wetwrap system in the market, Innovative Deyuan Wrap is,

• Compatible with all pipe sizes
• Can be applied onto straight pipes, elbows, tees ,valves ,fittings , vessels
• Compatible with carbon steel, stainless steel, alloys, etc.
• The fiber cloth can be glass fiber, carbon fiber and aramid fiber per selection
• Welding free
• Supplied as a standard complete system;
• Stronger in mechanical properties
• Stable in installation performances
• Saving in terms of both time and money.

In conclusion, Innovative Deyuan Wrap has been successfully proved with its effectiveness and great potential in the field application. It is expected that the application of Innovative Deyuan Wrap will be more popular in the near future and it will become an important option for pipeline reinforcements and repairs.

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