By way of example for a tank having a diameter of 20 feet 6 lm a shell of 3 16 in.
Frangible roof tanks.
This paper presents the results of an investigation into the frangible joint behavior of tanks designed to api 650 rules.
Even when using a frangible roof however some owners still.
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.
This failure is intended to vent the tank and contain any remaining fluid.
Such relatively weak roof to shell joints are known as frangible.
Frangible roof tanks are also vulnerable to damage if overfilled.
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.
The concept of frangible roof only applies to flat bottom cone roof tanks with limited roof apex angle.
Frangible roof tanks are also vulnerable to damage if overfilled.
The reasoning behind present api design formulas is reviewed.
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.
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 is a word that means easily broken.
4 8mm thick plate a.
Api 650 gives rules for the design of frangible roof joints in fluid storage tanks.
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.
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.
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.
