Frangible Roof Tanks

Describes research that evaluates the ability of the present api 650 tank design criteria to ensure the desired frangible joint behavior.

Frangible roof 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. 1 evaluation of the area inequality as a method to predict the buckling response of the compression ring 2 effect of roof slope tank diameter and weld size on the frangible joint and 3 effect of the relative strength. By way of example for a tank having a diameter of 20 feet 6 lm a shell of 3 16 in. 4 8mm thick plate a.

By way of example for a tank having a diameter of 20 feet 6 lm a shell of 3 16 in. The reasoning behind present api design formulas is reviewed. Frangible is a word that means easily broken. Api 650 gives rules for the design of frangible roof joints in fluid storage tanks.

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. Thus appropriate measures wellknown to tank designers are required to insure that the liquid level in the tank does not rise above the top straight side of the tank. The concept of frangible roof only applies to flat bottom cone roof tanks with limited roof apex angle. 4 8mm thick plate a.

This paper presents the results of an investigation into the frangible joint behavior of tanks designed to api 650 rules. This failure is intended to vent the tank and contain any remaining fluid. Frangible roof tanks are also vulnerable to damage if overfilled. Such relatively weak roof to shell joints are known as frangible.

For reasons discussed above many tank owners prefer to satisfy emergency venting requirements with a frangible roof particularly for tanks without a floating roof because of the frangible roof s potential to vent deflagrations without substantial damage to the shell or bottom. 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. Frangible roof tanks are also vulnerable to damage if overfilled.