Frangible Roof Requirements

Frangible roof joints by zhi lu b s tianjin university 1982 m s tianjin university 1984 a dissertation submitted in partial fulfillment of the requirements for the degree doctor of philosophy department of mechanical engineering college of engineering kansas state university manhattan kansas 66506 1994 approved by.

Frangible roof requirements.

4 2 api s tandard 653 tank roof to shell joint modification such as reinforcement of the joint attachment of handrail or other frangible joint area change. Evaluate the strength of the roof joint versus the shell to floor joint. Other means of providing emergency venting are recommended for small tanks. 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.

4 2 3 2 areas that are pitted. However experience shows that the frangible joint may not always perform as intended. This failure is intended to vent the tank and contain any remaining fluid. Frangible roof design for tanks under 50 does not work without tank specific design.

The reasoning behind present api design formulas is reviewed. 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 fact the frangible roof design fulfills the venting requirements due to deflagrations inside tanks for most tank sizes greater than about 35 feet in diameter.

In the event of over pre ssurization the frangible roof to shell joint is designed to fail before the tank shell or the shell to bottom joint. The concept of frangible roof only applies to flat bottom cone roof tanks with limited roof apex angle. 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 american petroleum institute api has developed a standard for the design and construction of welded steel storage tanks.

Frangible is a word that means easily broken. 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. Holes through roof plates shall be repaired or replaced. This standard provides for the design of a frangible roof joint but in 1978 the standard was amended to limit applicability of the frangible roof design to tanks having a diameter of fifty feet 15 2m or more.

That is of course if the tanks are built according to the rules for frangible roofs. The securement of the annular link mechanism to the rim and the roof is such as to permit.