Frangible Roof Tanks

Frangible roof joints for fixed equipment and effective frangible shell roof roof storage tanks materials user connections association eemua 183 guide for the prevention of 1999 the engineering uk current guidance on the causes of bottom bottom leakage from vertical equipment and leakage inspection and leak.

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. Frangible is a word that means easily broken. Such relatively weak roof to shell joints are known as frangible. 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.

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. Eemua 180 gives guidance to designers and users of such tanks on the practical steps that can be taken in design operation and maintenance to predispose the roof to shell joint to fail in preference to the shell to bottom joint thereby ensuring retention of the tank s contents. This failure is intended to vent the tank and contain any remaining fluid. 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.

By way of example for a tank having a diameter of 20 feet 6 lm a shell of 3 16 in. Api 650 gives rules for the design of frangible roof joints in fluid storage tanks. Frangible roof tanks are also vulnerable to damage if overfilled. 4 8mm thick plate a.

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. 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. 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.

The reasoning behind present api design formulas is reviewed. 4 8mm thick plate a.