Frangible Roof Requirements

Evaluate the strength of the roof joint versus the shell to floor joint.

Frangible roof requirements.

This paper presents the results of an investigation into the frangible joint behavior of tanks designed to api 650 rules. 4 2 3 2 areas that are pitted. This failure is intended to vent the tank and contain any remaining fluid. Other means of providing emergency venting are recommended for small tanks.

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. Frangible roof design for tanks under 50 does not work without tank specific design. 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. Api 650 paragraph 5 10 2 6 c was revised to discourage the use of frangible roof design on small diameter 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. 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. Holes through roof plates shall be repaired or replaced.

Api 650 gives rules for the design of frangible roof joints in fluid storage tanks. 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. What is claimed is.

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 is a word that means easily broken. The reasoning behind present api design formulas is reviewed. The securement of the annular link mechanism to the rim and the roof is such as to permit.

However experience shows that the frangible joint may not always perform as intended. 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.