Leak Mechanism on High Temperature High Pressure Pipe Flange with Insulation

Flange connection is widely utilized to connect piping, fittings and valves in chemical, refinery and petrochemical industry. However, leakage incidents from gasket surface have been happening at bolted flange connections. The authors experienced an incident that the existence of insulation, which is used to reduce heat loss of process fluids in piping, affected leakage at high temperature-high pressure (HT-HP) piping flange connection. In this paper, leakage mechanism with insulation at HT-HP piping flange connection is explained from the point of view of bolt tension calculated using finite element analysis and relaxation. Consequently, it is recommended that insulation not be used for HT-HP piping flange connection, and a weather seal or a personal protection be used instead.