Frangible Roof Storage Tank

That is of course if the tanks are built according to the rules for frangible roofs.

Frangible roof storage tank.

A frangible roof joint forming a flexible gastight connection between a tank shell and a roof comprising an annular link mechanism sealingly secured at or adjacent a first edge thereof to a rim of. In such tanks the roof to shell joint is intended to fail in the event of overpressurization venting the tank and containing any remaining fluid. Frangible roofs are normally specified as a means of providing emergency relief venting in the situation when a tank is engulfed in fire or the adjacent tank is on fire causing rapid vaporisation of the stored product such that the normal venting system cannot cope and the pressure in the tank rises to a point where the roof to shell joint fails. This paper presents the results of an investigation into the frangible joint behavior of tanks designed to api 650 rules.

See figures 7 and 8. In the event of over pressurization the frangible roof to shell joint is designed to fail before the tank shell or the shell to bottom joint.