Session: 02-06 MATERIAL - Qualification & Design

Paper Number: 132914

132914 - Field and Laboratory Assessment of High-Density Polyethylene Slabs 

Abstract: 

This paper focuses on field and laboratory assessments conducted on High-Density Polyethylene (HDPE) slabs as an alternative solution for protecting oil and gas pipeline systems from external interference for use in northern climates.

External interference is defined as external activities causing damage to the pipe or its components as per Canadian Standards Association (CSA) Z662. It is one of the primary causes of failure for oil and gas pipeline systems. One of the mitigative methods to reduce the number of incidents resulting in damage and likelihood of failure due to external interference, is the installation of a physical barrier. Traditionally, concrete slabs, steel plates, or casings have been used as physical barriers to provide mechanical protection. In recent years, HDPE slabs have been chosen as an alternative product for mechanical protection by various pipeline operators around the world, including TC Energy. The effectiveness of these slabs to protect pipelines from excavator strikes was demonstrated previously in Europe by the Pipeline Safety Group (PSG). Details of the PSG test results and other historical tests results, as well as success story of TC Energy’s implementation of HDPE slab will be presented in a companion paper in the International Pipeline Conference (IPC) 2024.

Canadian pipeline operators install pipelines year-round even in winter at temperatures well below freezing. According to the historical ground temperature data for Northern Alberta, the soil temperature at a depth of 1 m below ground remains above 0°C, even when the air temperature is below -20°C. Academic literature denotes the glass transition temperature for HDPE is well below -50°C (generally lower than -100 °C). While the HDPE slabs are acknowledged as effective to protect pipelines even in cold winters in northern climates, TC Energy recognizes the importance of testing the HDPE slabs at low temperatures to confirm the material performance at such conditions. Hence, TC Energy has partnered with Overpipe (a HDPE slab company) to conduct field impact tests at -23°C. Six (6) HDPE slabs with different formulations were tested. All tests displayed success at preventing and obstructing excavator strikes with minimal damage to the slabs, with no indications of rapid crack propagation. One slab did show a minor crack at the point of contact, but no significant propagation was noted. In addition to the field impact testing, laboratory material tests have also been completed on these slabs. Based on Overpipe’s field impact and material tests, one of the slab formulations was recommended to be used in cold conditions.

To further confirm the material properties, TC Energy is completing material testing on the recommended slab formulation. The tests, which include Charpy-V-Notch (CVN) testing, tensile testing and Dynamic Mechanical Analysis (DMA), are currently in progress. The results are expected by the end of 2023. Once the results are received, TC Energy will thoroughly evaluate all the information, and will plan next steps. If necessary, further tests will be planned and conducted. Otherwise, if the results return positive indications, TC Energy will update the existing processes to install the qualified HDPE slabs system-wide including cold weather conditions.

Presenting Author: Jonathan Law TC Energy

Presenting Author Biography: Jonathan Law is a Civil Engineering graduate from the University of Calgary who joined TC Energy in 2014. He has experience in the Crossings, Land-use Monitoring, and Damage Prevention roles in both technical and program management capacities. Jonathan continues to contribute to the ongoing development of TC Energy’s Damage Prevention programs, seeking new engineering methodologies, tools, and process improvements. He has also supported in past IPC papers such as IPC2018-78633 and IPC2020-9478.

Authors:

Christina Tran TC Energy
Jonathan Law TC Energy
Frank Cox TC Energy
Kathy Escalante TC Energry
Fernando Puello Acuren