Onshore pipeline repair

Alexander, C., Ochoa, O.O., 2010. Extending onshore pipeline repair to offshore steel risers with carbon-fiber reinforced composites. Composite Structures 92, 499—507. 

Offshore pipeline risk It is more difficult to repair an offshore pipeline than an onshore pipeline. It is therefore associated with an increased risk, or lower security of supply, to receive your gas from an offshore pipeline compared to an onshore pipeline. 

Before conducting a repair on a corroded pipe, analysis must be done to determine whether a repair is sufficient to restore the strength of the riser. This can be evaluated using the codes provided in ASME B31G (1991). The standard used here is compliant for onshore pipelines where the equations are only functions of the corrosion dimensions and internal pressure. Nevertheless, it provides a basis for determining the required thickness of the composite laminate. 

There are two typical types of fiber reinforcement used in repair of onshore pipelines carbon fiber and glass fiber. The selected materials are discussed in Section 9.6.2.2. The model discussed here uses a repair laminate with a 30° wrap angle with varying material. 

Stress Engineering, Inc. is one of the major companies that has run multiple full-scale tests to validate the performance of numerous onshore pipeline composite repair products that are available in the market. Full reports documenting the vahdation of composite repair products are available (Alexander, 2005 Worth, 2005 Francini and Kiefner, 2006). Various publications on the development of the CRS for offshore riser application are also available under Chris Alexander of Stress Engineering, Inc. A program cosponsored by the Pipeline Research Council International, Inc. (PRCI) involves the full-scale testing of corroded risers with a CRS placed in a seawater test facility for 10,000 h subjected to combined pressure, tension and bending loads (Alexander, 2012). 

Composite repairs have been utilized in onshore transmission pipelines for the past decade. These repairs are used on pipe sections that have been weakened due to corrosion and mechanical damage. A survey conducted by the US Department of Transportation showed that the overaU costs can be reduced by 24% using composite repair instead of welded pipe sleeves. Compared to replacement of the whole defective pipe section, the cost has been redueed by approximately 73% (RSPA, 2000). 

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