Frangible Roof Requirements

The securement of the annular link mechanism to the rim and the roof is such as to permit.

Frangible roof requirements.

4 2 3 floating roofs 4 2 3 1 areas of roof plates and pontoons exhibiting cracks or punctures shall be repaired or the affected sections replaced. 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. Frangible roof design for tanks under 50 does not work without tank specific design. Api 650 paragraph 5 10 2 6 c was revised to discourage the use of frangible roof design on small diameter tanks.

Frangible is a word that means easily broken. This failure is intended to vent the tank and contain any remaining fluid. 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. 4 2 3 2 areas that are pitted.

Api 650 gives rules for the design of frangible roof joints in fluid storage tanks. See figures 7 and 8. This paper presents the results of an investigation into the frangible joint behavior of tanks designed to api 650 rules. Other means of providing emergency venting are recommended for small tanks.

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. However experience shows that the frangible joint may not always perform as intended. The american petroleum institute api has developed a standard for the design and construction of welded steel storage tanks. 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.

Evaluate the strength of the roof joint versus the shell to floor joint. 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. Holes through roof plates shall be repaired or replaced. That is of course if the tanks are built according to the rules for frangible roofs.

The concept of frangible roof only applies to flat bottom cone roof tanks with limited roof apex angle. 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.