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| Structure and Aging Performance of Electro-fusion Welded Interfaces in Urban PE Gas Pipelines under Long-term Service Conditions |
| Received:October 26, 2024 Revised:November 21, 2024 |
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| DOI：10.7643/issn.1672-9242.2025.02.013 |
| KeyWord:electro-fusion welding interface aging PE pipeline soil environment urban gas |
| Author | Institution |
| QIU Di |
Beijing Gas Group Co., Ltd., Beijing , China |
| LI Mengyin |
Beijing Gas Group Co., Ltd., Beijing , China |
| ZHONG Wanchen |
Beijing Gas Group Co., Ltd., Beijing , China |
| NI Zhiguo |
Beijing Gas Group Co., Ltd., Beijing , China |
| WANG Fei |
Beijing Gas Group Co., Ltd., Beijing , China |
| XIN Yan |
Beijing Gas Group Co., Ltd., Beijing , China |
| LI Yichong |
Beijing Gas Group Co., Ltd., Beijing , China |
| GAO Jin |
Institute of Advanced Materials Technology, University of Science and Technology Beijing, Beijing , China |
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| Abstract: |
| The work aims to study the aging performance and its changing law of the electro-fusion welded interfaces under long-term service. With the electro-fusion welded pipeline fittings and new welded pipeline fittings of PE gas pipeline in service for 30 years as samples, the structural performance of the welded interface was analyzed by ultrasonic phased array nondestructive testing and dissection, and the aging behavior of the middle part and welded interface of the PE pipeline was compared by oxidation induction time test, infrared spectrum test and crystallinity test. By analyzing the soil near the welded pipeline fittings in service, the chemical medium that affected the aging of the pipeline fittings in service was determined. The PE electro-fusion welded interface had different degrees of structural defects under long-term service, especially the obvious performance weakening at the welded interface. The thermal oxygen stability and crystallization properties of the welded interface were lower than those of the middle part of the pipeline, while the properties of the middle part of the pipeline were lower than those of the new welded interface. Compared with the new welded pipeline, the electro-fusion welded interface of PE in service for 30 years had C—O— aging peak, which led to a certain degree of aging. After testing, amines, ketones and alcohols (such as dodecyl dimethyl tertiary amine) existing in the soil had obvious chemical activity and caused aging effect on PE materials. The temperature of soil and chemical medium bring about the generation of C—O aging groups in the electro-fusion welded part of PE gas pipeline, which will destroy the structural regularity of polyethylene, lead to the decrease of its crystallinity, and affect the mechanical bonding performance of the electro-fusion welded interface. This study confirms the negative impact of soil environment on PE, affecting its service life and safety, so more attention should be paid to the long-term service safety of PE gas pipeline. |
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