Expanding Pipeline Repair/Replace Options
Developed countries face an aging pipeline infrastructure with an increasing need for more and more maintenance. At the same time, burgeoning development places limits on access and restricts working areas, making maintenance more difficult and expensive. The natural gas industry is no exception to the challenges of aging infrastructure and choking development. The natural gas industry faces an additional challenge⎯population sprawl that converts formerly rural areas to Class 2, 3, and even 4, reducing Office of Pipeline Safety (OPS) Maximum Allowed Operating Pressures (MAOP). All the while, increasing demands require more throughput and higher MAOPs to satisfy it. The industry is desperate to maintain the infrastructure at the very time open trenching to repair or replace pipe is becoming more difficult and expensive. While not a panacea, technology transfer has over the years given the industry valuable tools to improve safety, reliability, and efficiency. Advanced inspection devices and pipe-boring equipment are just two examples of improved tools, but more are needed to allow the natural gas industry to keep pace with demands. Pipe expansion technology, in the guise of solid tubulars developed and actively used in the well drilling industry, is a likely candidate for transfer to the pipeline industry. Solid expandable tubular technology uses proven well drilling methods to insert a specially designed and manufactured steel pipe inside an existing pipe. The inserted pipe is then expanded to mate against the existing pipe. In the ultimate iteration, both the new and the old pipe are expanded until the final composite of old and new pipe has no loss of the original pipeline’s inside diameter (ID). Initially, the refurbished pipe would use only the new wall thickness to calculate a new MAOP. Additional testing could result in using the combined wall thickness for pressure calculations. While expansion practices and required metallurgies are well understood, several technical and economic hurdles must still be overcome. Some of the technical challenges include cathodic protection of the newly installed and expanded pipe, corrosion prevention of the annular space between the two pipes (if any), and how to install taps to the internal pipe. The primary economic issue is cost⎯can the technology be deployed in a cost-effective manner. As with past technology transfer, these issues must be overcome through multiple parties working collaboratively.