Analysis of a HDPE flanged connection with a time and temperature dependent constitutive behavior. (June 2021)

• Record Type: Journal Article
• Authors: Shahin, A.; Barsoum, I.; Korkees, F.
• Is Part Of: International journal of pressure vessels and piping. Volume 191(2021)
• Publication Date: 2021-06
• Subjects: Bolted flange -- HDPE -- Three network model -- Flanged connection -- FEA -- Temperature -- Leakage -- Torque; Pressure vessels -- Periodicals; Pipe -- Periodicals; Récipients sous pression -- Périodiques; Tuyaux -- Périodiques; Pipe; Pressure vessels; Periodicals; 681.76041
• DOI: 10.1016/j.ijpvp.2021.104375
• Languages: English
• ISSNs: 0308-0161

Abstract

Abstract: High density polyethylene (HDPE) piping systems are used extensively in both industrial and societal infrastructure. However, their performance is sometimes impacted due to leakage through flanges, especially HDPE pipes with large diameters. Many factors affect leakage, including stress relaxation in the HDPE material and ambient temperature effects. Hence, this study investigates the effect of temperature on the leakage of a HDPE flanged connection with steel backing rings. It incorporates the effects of stress relaxation and temperature on the HDPE material and assesses the degradation of performance of the connection with time by means of finite element analysis (FEA). The temperature and time dependent mechanical properties of the HDPE material are determined experimentally through tensile, compression and relaxation testing conducted at various temperatures under isothermal conditions. The constitutive behavior of the HDPE material is modeled using the nonlinear visco-elastic plastic three network model (TNM), which predicts the mechanical behavior of HDPE markedly well. The calibrated TNM is used in the FEA study to investigate the leakage performance of the HDPE connection at various temperatures (23, 40, 60 and 80 °C) at isothermal conditions over a service time of one year. The FEA results reveal that the flanged connection can experience leakage at all temperatures due to insufficient bolt preload. It is also found that leakage occurs prematurely as temperature increases. To simulate a realistic scenario resembling an above ground piping system, an annual temperature profile for a selected geographic location was prescribed to the model to simulate leakage over a one year period. Based on the results, several bolt re-torqueing plans were explored and suggestions are made on the best bolt re-torqueing practice for preventing leakage over the service life of the HDPE connection. Highlights: The temperature effect on the short and long term response in tension and compression of HDPE is investigated experimentally. Experiments are used to calibrate the three network viscoelastic-plastic constitutive model (TNM). The calibrated TNM model is used to simulate the time and temperature dependent behavior of a bolted HDPE flange. Results show that temperature and time has a significant effect on leakage in the HDPE flange, and the need for bolt re-torqueing.