Frangible Roof Weld

This failure is intended to vent the tank and contain any remaining fluid.

Frangible roof weld.

This video documents the research and testing on frangible joint storage tanks performed at kansas state university and thunderhead engineering. One of the safety measures that can be employed for emergency venting is so called frangible roof to shell joint. Api 650 gives rules for the design of frangible roof joints in fluid storage tanks. However in the context of tanks the word has a specific meaning and is defined in the main tank construction standards bsen 14015 and api650.

The api 650. A small diameter tank which comprises a shell having a rim at its upper edge a roof and a frangible roof joint the roof joint including annular link means sealingly secured at or adjacent a. The concept of frangible roof only applies to flat bottom cone roof tanks with limited roof apex angle. This paper presents the results of an investigation into the frangible joint behavior of tanks designed to api 650 rules.

Such joint is practically sacrificial weld which has to collapse in event of excessive internal pressure while shell to bottom joint has to be undamaged to provide structural and safe integrity of tank. The reasoning behind present api design formulas is reviewed. 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. A frangible roof is a roof to shell joint or junction that is weaker than the rest of the tank and will preferentially fail if the tank is over pressurised.

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. 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 the tank and sealingly secured at or adjacent a second edge thereof to the periphery of the roof.