Experimental and Simulation Investigation on Failure Mechanism of a Polyethylene Elbow Liner Used in an Oilfield Environ
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TECHNICAL ARTICLE—PEER-REVIEWED
Experimental and Simulation Investigation on Failure Mechanism of a Polyethylene Elbow Liner Used in an Oilfield Environment . Xin Fan . Nan Ding . Han Ding . Lushi Kong Xiaodong Shao . Houbu Li . Dongtao Qi . Qingshan Liu . Yanyan Xu . Pengli Ge
Submitted: 25 August 2020 / Accepted: 20 September 2020 Ó ASM International 2020
Abstract Internal collapse of a polyethylene (PE) liner in the steel elbow between furnace and manifold of a secondstage separator occurred during the operation of the crude oil treatment system in a certain factory. To analyze the causes and prevent such cases from happening again, macroscopic and microscopic observation, FTIR, density and hardness measurements, thermogravimetric analysis (TGA), tensile test, and thermal stress simulation were conducted. The results show that the PE liner was swelled by the conveying medium, resulting in a decrease in yield strength and module. Moreover, high operating temperature leads to softening and expansion of the swelled liner pipe. Finally, the stress caused by the PE liner’s inability to expand freely due to the external constraints of steel elbow increased dramatically and induced the liner pipe collapse inward, resulting in pipe blockage. Failure mechanism is further verified by computer simulation.
L. Kong (&) N. Ding H. Ding X. Shao H. Li D. Qi State Key Laboratory for Performance and Structure Safety of Petroleum Tubular Goods and Equipment Materials, Tubular Goods Research Institute, China National Petroleum Corporation, Xi’an 710077, China e-mail: [email protected] X. Fan Natural Food Macromolecule Research Center, School of Food and Biological Engineering, Shaanxi University of Science& Technology, Xi’an 710021, China Q. Liu Y. Xu P. Ge Key Laboratory of Enhanced Oil Recovery in Carbonate Fractured-vuggy Reservoirs, CNPC and SINOPEC Northwest Company of China Petroleum and Chemical Corporation, Urumqi 830011, China
Keywords Collapse
Polyethylene Elbow liner Swelling
Introduction In recent years, polymeric pipes are being considered as suitable candidates to substitute for metallic pipes in the transportation of oil and oil derivatives. Carbon steel is still the main material used to manufacture pipelines, but corrosion and a fairly high internal roughness are two main drawbacks of steel pipelines [1, 2]. Therefore, the substitution of old steel grids by new ones using polymers or steel tubes with an inner polymeric layer, instead of an allsteel pipe, is a common trend, since polymers are corrosion resistant and can also be manufactured with very small surface roughness [3]. Among the many available polymeric materials, polyethylene (PE) is a promising choice due to its good properties, availability, and cost [4–6]. PE pipes are mainly used in the protection of steel pipes in two fields: corrosion protection in the transportation of corrosive chemical reagents and repair of damaged steel pipes [7]. Trenchless interpenetration technology for repairing damaged pipelines was originally d
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