In this study, the integrity of a manhole structure made of a 78 in. high density polyethylene (HDPE) stub-end, steel ring, and blind flange, sealed with a compressed nonasbestos fiber (CNAF) gasket is investigated by means of a parametric finite element analysis (FEA). A coupled thermomechanical nonlinear FEA model is built, comprising of a heat transfer and a structural model, which allows modeling the complex thermal and mechanical loads and their interactions present during the operation of the manhole. The temperature-dependent elastic–plastic HDPE material constitutive behavior and the temperature-dependent nonlinear response of the CNAF gasket are accounted for in the model. Factors influencing the performance and integrity of the manhole such as stud-bolt pretorque level (Tb), internal pressure (Pi), and outer temperature (To) are considered. Based on the results, the integrity and performance of the structure are assessed in view of a leakage through the gasket criterion and a yielding of the HDPE stub-end criterion. The FEA results reveal that both Tb, Pi, and To significantly influence the performance (i.e., leakage) of the gasket and the integrity (i.e., yielding) of the HDPE stub-end. At 40 °C, it is possible to find a safe operational window for a range of Tb and Pi values, where no leakage through the gasket or yielding of the stub-end occurs. However, as the temperature is increased this safe operational window decreases considerably, and at 80 °C safe operation cannot be guaranteed where leakage, yielding, or both simultaneously, will lead to loss in performance and integrity of the manhole structure.
Thermomechanical Evaluation of the Performance and Integrity of a HDPE Stub-End Bolted Flange Connection
Division of Lightweight Structures,
Royal Institute of Technology—KTH,
Stockholm 100 44, Sweden
The Petroleum Institute,
Khalifa University of Science and Technology,
Abu Dhabi, UAE
Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received November 20, 2018; final manuscript received May 21, 2019; published online July 17, 2019. Assoc. Editor: Sayed Nassar.
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Barsoum, I., Barsoum, Z., and Islam, M. D. (July 17, 2019). "Thermomechanical Evaluation of the Performance and Integrity of a HDPE Stub-End Bolted Flange Connection." ASME. J. Pressure Vessel Technol. October 2019; 141(5): 051206. https://doi.org/10.1115/1.4043844
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