Investigation and Case Study of Composite Repair Performance at Low Temperatures on Buried Pipelines

ABSTRACT

Composite repair systems composed of carbon fiber/epoxy composite materials can be affected by exposure to harsh environments. The vast majority of testing on composite repair systems to date has been to investigate the effects of high temperatures on composite performance. However, depending on the location and time of year, low temperatures can also play a big role in the performance of coatings and composite repairs on pipelines. Therefore, the effects of low temperature should also be tested to prove the reliability of the composite repair systems in low temperature environments. In response to this concern, the impact of exposure to a low temperature environment below -30°C (-22°F) was investigated on a carbon fiber and epoxy composite repair system that had previously been qualified to the ASME⁽¹⁾ PCC-2¹ Article 4.1 nonmetallic repair standard. Tensile tests were performed in accordance with ASTM⁽²⁾ D3039², and 5 J impact and burst tests were performed in accordance with ASME PCC-2¹ Article 4.1 at temperatures below -30°C (-22°F). Based on the results of the testing, it can be concluded that the specific composite repair system can be employed for low temperature applications on buried pipelines and that there is no degradation in the repair system performance. To prove that the results of the testing apply to the field, the composite repair systems were successfully applied to buried transmission pipelines in cold temperatures, the details of which will be presented.

INTRODUCTION

Cold temperatures regularly have a severe impact on existing infrastructure around the world. For example, concrete is more likely to prematurely fail in areas where there are frequent freeze/thaw cycles or constant cold temperatures. In pipeline transportation, the freeze/thaw cycles or constant cold temperatures can lead to premature coating failure if a coating is not correctly sourced or applied per manufacturer’s instructions for the specific environment. The introduction and fluctuation of cold temperatures can also lead to formation of various defects on buried pipelines, depending on a multitude of factors.