Structural analysis and sealing capacity of gasketed plate heat exchangers with HNBR and EPDM rubbers

Rubber is an engineering polymer of interest in most industrial sectors. In gasketed plate heat exchangers (GPHEs), these elements comprise gaskets that are responsible for sealing the system under high levels of compression, temperature and pressure. Therefore, it is a necessity to understand how operating conditions affect GPHE structural behavior and sealing performance, regarding rubber materials and features. This work aims at determining GPHE integrity and mechanical characteristics with the aid of sealing performance experiments and strain gauge measurements at critical plate locations in a real equipment and in prototypes consisting of GPHE components. Hydrogenated nitrile butadiene rubber (HNBR) and ethylene-propylene-diene rubber (EPDM) gasket materials were evaluated. Based on compression strength experiments, the system stiffness ranged from approximately 0.3 to 7.0 kN/mm regarding the combined effects of the number of plates and the compression level. The combined effects of compressive strength, compression levels and rubber material on sealing performance were obtained with prototypes comprising at least six gaskets, whose conditions presented stable compressive strength behavior. In critical region on the real-scale heat exchanger, the measured von Mises stress level was 316 MPa and 133 MPa using EPDM and HNBR gaskets during tightening, respectively. It is conjectured that higher operation pressure loads can occur with the harder and stiffer material (EPDM), as showed by hydrostatic tests. Empirical correlations were developed in order to relate sealing capacity based on the system geometry, compression level and gasket material.