Effect of temperature on the relaxation of polyvinyl chloride flanges

Abstract

After a comparatively short half century, PolyVinyl Chloride (PVC) has invaded almost all applications of traditional materials, such as clay, cast iron, steel and asbestos cement, and becomes the premier pipe material. PVC is popular due to its advantages of immunity to corrosion and biological resistance. Convenient installation and handling are also two contributing factors to its popularity. PVC Piping systems have been widely used for fluids conveyance in industrial and building sites and household. Bolted flange joints are important components of piping systems. They are mainly used as dismountable connections between pressure equipment ensuring structural integrity and leakage tightness. Meanwhile, the flange is a recommended mean to connect equipment of different materials. As other plastic materials, PVC also experience creep over time, the rate of which is influenced by load and temperature. Polyvinyl Chloride bolted flange joints undergo relaxation under compression for which the creep properties are different from those under tension. The sealing performance of a flange connection is impacted by its capacity to resist relaxation. For the purpose of improving the load currying capability and reduce leakage failures of PVC flange joints, it is important to properly understand and predict their creep-relaxation behavior. The first objective of this work is to develop a PVC creep model based on creep test data obtained at various compressive loads and temperatures. The second objective is to simulate PVC flange relaxation using the developed creep model using a real NPS 3 class 150 bolted flange joint of dissimilar materials one made of SA105 and the other one of PVC materials. This study provides a fundamental understanding on how compression creep data obtained from the UGR fixture may be used to predict the short-term creep-relaxation behavior of PVC flanges under various operating conditions.

Date	5 Jun 2017
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Hakim A. Bouzid (Supervisor)