Trenchless installation that used a high-density polyethylene (HDPE) liner has expedited rehabilitation of nearly 8 miles of a 6-in. crude-oil pipeline in Oklahoma operated by Sun Pipeline.
The project originated at the Doyle gathering field and ended at Sun's Velma, Okla., station.
The 33-year-old high tensile-strength steel pipeline, running west of the Arbuckle Mountain range, had deteriorated in recent years from internal corrosion.
With an average pull length of 2,500 ft, construction progressed at 0.750 miles/day and was completed in 11 days. The project used Pipe Rehab International's "UltraPipe" lining system, "Form-A-Flange" connections, along with trenchless construction for the 41,866 ft of pipe.
Pipe Rehab is a subsidiary of Insituform Technologies Inc. of Memphis.
OD REDUCTION
Pipe Rehab said Sun needed a solution that would enhance the pipeline's integrity, protect the area's environment, and reduce the burden on landowners.
This pipeline passes near a water supply reservoir for Duncan, Okla., raising the potential for contamination from the pipeline.
Sun also sought to lessen the inconvenience and degree of property damage to easement landowners.
After property owners approved the procedure, Sun made excavation cuts in 2,500-ft sections. HDPE pipe, 6.5-in. OD, was inserted into a roller reduction system that temporarily reduces the liner's OD.
The liner was then inserted into the host pipeline at 60-80 fpm. During the following 12 hr, the liner progressed through its natural reversion process, resulting in a virtually annulus-free compressive-fit liner and providing improved product flow (Fig. 1).
In addition to the UltraPipe lining system, each section of pipe received a Form-a-Flange end seal, formed from the liner material through a thermoforming, compressive mold process.
The Form-a-Flange machine is bolted to the steel flange (Fig. 2). The PE liner is heated, then pressed back into the mold formed by the blowout prevention ring, where the PE fuses with the reinforcing disk under high pressure.
Excess PE is extruded through the blowout prevention ring. The resulting seal is homogenous with the liner.
According to Pipe Rehab, the seals are 150% thicker than the liner itself, making them the strongest part of the system.
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