Experimental and Numerical Study of Expanded Graphite Packing Ring for Fugitive Emissions Applications in Valves

Abstract Nowadays, environmental protection and the energy transition are at the heart of global concerns and are driving action and efforts at every level. In this context, the nuclear, petrochemical and chemical industries are working thoroughly to control and reduce fugitive emissions from their valves in order to minimize their impact. Reduction of these emissions can be achieved through improvements in the sealing of stuffing boxes. The aim of this work is to develop the knowledge of stuffing boxes and more precisely the mechanical behavior of flexible graphite rings. First, an experimental study was conducted, based on the results of free compression tests and compression tests of a flexible graphite ring in a special apparatus imitating the operation of a valve stuffing box. Axial stress-strain curves are extracted from the free compression tests and from the compression tests of the packing in the casing as well as radial stress distribution in the special apparatus. Then, a finite element model reproducing the packing was performed. Material parameters of an original Hyper-Hysteresis behavior model [1] were determined to fit the stress-strain behavior of a single packing ring under load. Finally, experimental and numerical data was compared in order to determine the validity of the model.