CIP Liner rehabilitation technology for high-pressure pipelines

As its latest product, the company Karl Weiss has successfully completed the development of the starline^®20000 procedure within the project "Rehabilitation of High-Pressure Gas Pipelines up to 30 bar Operating Pressure using Fabric Hose Relining" (Cured-In-Place [CIP] lining) led by E.ON Ruhrgas AG. This completely new special composite (linerresin) system is certified by DVGW (German Technical and Scientific Association for Gas and Water) in accordance with VP 404. The starline^®20000 high-pressure liner, in short HPL, represents a worldwide new generation of HPL materials and is already successfully used.

With the completion of stress/time-torupture tests conducted for 10 000 hours (almost 14 months), DVGW certifies that the starline^®20000 special composite system is suitable for operating pressures up to 30 bar with a service life of at least 50 years even at corrosions of up to 50 mm in diameter.

Such holes are to be expected no earlier than after 40 years, based on initial leakages, according to a study conducted by E.ON Ruhrgas AG on the corrosion behavior of gas transmission pipelines outside of stray current impact and operated at least with reduced cathodic corrosion protection. Existing corrosion holes, which especially in high-pressure gas pipelines pose a substantial hazard, are eliminated efficiently, fast and permanently using the starline^®20000 technology. This restores the required safety standard and in addition minimizes the risk of welding seam fractures.

Thus, Karl Weiss with its starline^® liner products and complementary installation procedures covers the entire scope of rehabilitations, from gas service connections with nominal diameters from 20 mm up to high-pressure gas pipelines with an operating pressure of 30 bar. Using materials approved for drinking water applications, water distribution pipelines can be rehabilitated with the starline^®1000 procedure up to 10 bar. Water pipelines with an operating pressure up to 40 bar can also be rehabilitated using materials with the appropriate material strength. This technology is designated starline^®10000.

However, only the completely new rehabilitation technology for high-pressure and transmission pipelines, its required procedures and technical equipment made it possible to provide the adequate rehabilitation process for the first time. With this unique technology unknown so far, a practical and economic procedure is available for improved operational safety and reduction of risks associated with maintaining older pipelines. In combination with the efficient and long-lasting HPL, this results in great benefits for operators and manufacturers of natural gas pipelines as well as a new field of work with a promising future for Karl Weiss. Vision has become reality (Figure 1).

starline^® fabric hose relining system

Description of the rehabilitation of high-pressure pipelines
Although the starline^®20000 material development was completed within the framework of the E.ON Ruhrgas project, the installation process itself was not part of the project. This installation process is based upon the starline^®2000 procedure for rehabilitation of gas distribution pipelines, which has been performed successfully in over 600 km. Here, the liner filled with resin is inverted into the cleaned pipeline section to be rehabilitated by applying air pressure. This, however, is the only common ground between the starline^®20000 technology and the wellestablished fabric hose relining system because completely new technical solutions have become necessary in order to realize the installation objectives for highpressure gas and water transmission pipelines.

Using starline^®20000, gas transmission pipelines with an operating pressure up to 30 bar are rehabilitated in individual installation lengths up to 600 m in order to restore the required safety standard fast and permanently. The materials employed are a fabric hose consisting of seamless, circularly woven, highstrength polyester yarns and a special cold-curing epoxy resin especially for long installation lengths. For rehabilitation of water pipelines, liner and resin comply with the sanitary requirements and fulfill KTW guidelines for drinking water compatibility as well as microbiological requirements of DVGW Worksheet W 270. Prior to the installation, the pipeline is taken out of operation and cleaned thoroughly – depending on the degree of contamination – using the ultra-high water jet method. It is subsequently roughened up using the sand-blasting process.

The liner is cut to the length required, saturated with the required amount of the appropriate starline^® epoxy resin and wound up in a pressure vessel where the resin is evenly distributed in the liner through a roller pair with a predefined gap. The liner's end is attached to the inversion head at the pressure vessel's output. Then the vessel is pressurized whereby the liner being unwound inverts into the pipeline, i.e. the liner's inside saturated with resin is turned out and pressed onto the pipeline wall. Despite the high-strength material, the lining is achieved without wrinkles because the liner's diameter is dimensioned to the internal diameter of the pipeline to be rehabilitated. The inversion speed is controlled by the winding revolutions of the pressure vessel shaft; at first, by the liner itself, and once it has left the pressure vessel, by the retention belt which was earlier attached to one liner end and the reel shaft. Figure 2 shows the inversion process. If the entire liner is in contact with the pipeline, the pressure is maintained at ambient temperature until the resin has cured. The cold-curing resin system with a very long pot life eliminates thermally induced tensions in the pipeline, which will inevitably occur during the warm-curing process and cause welding seam fractures in particular in bitumen-coated transmission pipes. Due to the liner's complete and migration-tight bonding to the pipe wall it is not necessary to seal the liner's ends.

Tasks of fabric hose relining
The starline^®20000 system is a reliable and safe rehabilitation technology in order to:

• restore operational safety in the event of corrosion damage,
• limit localized damages, and
• in particular, with drinking water pipelines it permanently restores sanitary requirements.

The fabric hose relining system is also the appropriate method to restore operational safety in the following situations:

• Prevent corrosion: In the vicinity of underground gas storage systems, natural gas may become humid. In gas transmission pipelines, fabric hose relining prevents internal corrosion.
• Seal inaccessible locations: Pipeline leakages in locations difficult to access, such as culverts, railway underpasses or nature reserves, which could only be repaired at great expense using the open-cut method.
• Tightness after welding seam fractures: Other problems are high-pressure gas pipelines in earthquake and submergence of ground areas (e.g. mining areas, etc.). The earth movements may cause welding seams to break. With fabric hose relining, the pipelines' safety is assured for a certain period of time until the pipeline can be depressurized and the damage repaired.

After the pipeline's rehabilitation, the original operating pressure can be applied again. Pipelines with rust perforations of 50 mm in diameter continue to be safe to operate.

Excavation work is reduced by 95 % compared to the open-cut method because liner installation pits are required only every 480 m to 600 m – depending on the diameter, of course.

In order to use CIP lining procedures, the host pipe must be able to take up the internal and external pressure. The pipeline must be calibrated prior to rehabilitation. Furthermore, it also has to be cleaned (white metal). Bends can also be lined through using this procedure. However, the number of bends that can be relined is limited and depends on pipe diameter and curvature.

New technical equipment for liner installation

Karl Weiss focused on three specific areas relating to the installation during the starline^®20000 HPL development: inspection procedure prior to and after lining up to 1000 m; extended inversion procedure up to 600 m; resin mixing/supply and application system for resin batches of more than 2 t/h. The equipment used so far only allows for inspection lengths up to max. 180 m, inversion lengths up to max. 240 m and manually handled resin batches up to max. 0.5 t/h.

The technical equipment consists of:

• Inspection system for visual and metrological inspection of the pipeline. This process is designed for inspection lengths up to 1000 m and nominal diameters from 200 mm – 1200 mm. Prior to rehabilitation (inspect degree of cleaning) and after liner installation and curing (quality control of full bonding and installation of liner), the pipeline is visually inspected and the internal pipeline diameter is measured using a caliper. The result of the caliper measurement is recorded to determine the internal diameter profile. It also indicates: inadmissible deviation automatically.
• Resin mixing and measuring system. The system processes up to 2 tons resin per hour without bubbles. For these resin batches, the equipment must be air-conditioned (Figure 3).
• Liner application with resin filling and distributing system. This system consists of a height-adjustable liner holder as well as an air-conditioned transport and unwinding unit. The filling process of the resin is also performed without bubbles.
• Inversion equipment. In order to extend the inversion sections to 600 m, the pressure drum had to be designed completely new and ancillary equipment had to be changed fundamentally. The pressure drum is designed such that the maximum diameter for intake of the maximum liner length is utilizable in relation to the minimum height of the flat-bed trailer as well as the maximum possible bridge clearance (i.e. for pipes up to 600 mm diameter, the liner inversion length is up to 600 m, with pipes ≥ 600 mm – 1200 mm diameter, the inversion length is reduced accordingly by folding the liner longitudinally). The pressure drum is equipped with all-terrain caterpillar tracks.

The first field installation of the starline^®20000 HPL together with the new installation equipment took place in the U.S. in October of 2004. Using these innovative tools and equipment, sections of a steel pipeline with 300 mm in diameter with individual inversion lengths up to 300 m have been relined successfully and the technology’s efficiency has been demonstrated (Figure 4). In 2005, further projects will follow where the entire potential will be fully tapped.

Summary

The starline^®20000 procedure is a CIP liner system certified by DVGW for rehabilitation of potentially corroded highpressure pipelines for pressures up to 30 bar in gas pipelines. The system has a tested service life of at least 50 years and bridges corrosion damage with diameters up to 50 mm. Using materials certified for use in drinking-water applications with the appropriate material strength, water pipelines with an operating pressure up to 40 bar can be rehabilitated. Such rehabilitation considerably extends the remaining useful life of potentially corroded high-pressure pipelines and thus markedly reduces material and energy consumption. It also leads to an increase or restoration of the pipelines' operational safety. Furthermore, the number of pits as well as construction noise, emissions caused by machinery and traffic and other adverse effects on people and the environment are considerably reduced.

Applying the starline^®20000 system to rehabilitate high-pressure pipelines has the following benefits:

• Seal all leakages in the pipe section lined and increase or restore operational safety
• Restore sanitary condition required in drinking water pipelines
• Prevent internal corrosion
• Seal welding seams
• Seal leakages at inaccessible locations and road crossings, in ecologically sensitive areas, on rocky ground, etc.
• No problem with access rights and no need to work under cramped conditions
• Support utility in adhering to safety regulations
• Cost-effective procedure reduces risks and improves pipelines' state of preservation.

The first practical installations have shown that this technology is a practicable maintenance method for sealing existing and future leakages, which reduces the risks associated with operating older pipelines in particular.

Karl Weiss has completed the development of procedures for inspection and profile recording prior and after lining of pipeline sections up to 1000 m, for extended inversion up to 600 m and for a resin mixing/supply and distributing system up to 2 t/h in a highly ambitious project with competent partners.

The starline^®20000 procedure expands the starline^® product range by another significant component. With the increased efficiency of these procedures, these technologies have an edge over laying new pipelines. Using only one set of starline^®20000 rehabilitation equipment, rehabilitations of more than 50 km can be achieved annually in one-shift operation. This new inversion equipment has been used for the first time for commercial projects in the U.S. in 2004. Further projects follow in 2005. In Europe, a project for the rehabilitation of water pipelines using this new technology is in preparation.