Frangible Roof Requirements

4 2 2 2 when a frangible roof to shell joint is required evaluate for items impacting compliance with requirements under api 650 section 5 10 2 6.

Frangible roof requirements.

This paper presents the results of an investigation into the frangible joint behavior of tanks designed to api 650 rules. The roof plate to curb angle fillet weld must be greater than 5mm. N the roof wall and foundation connections in ac cessory buildings should meet the requirements for connections in primary buildings. That is of course if the tanks are built according to the rules for frangible roofs.

No further reproduction or distribution permitted. A roof to shell joint designed according to api 650 rules is considered to be frangible and in case of excessive internal pressure intended to fail before failure occurs in the tank shell or shell to bottom joint. If nfpa thought it worthwhile to make the code change retroactive so should api and sti in the evaluation of existing tanks. Frangible roof designs are typically not adequate on tanks under 50 diameter therefore alternate solutions are required.

The roof plates must not be welded to the tank roof structure which normally rules out externally stiffened tank roofs from being considered as being frangible. 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. 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 reasoning behind present api design formulas is reviewed.

N accessory buildings below the dfe should be an chored to resist being blown away by high winds or carried away by floodwaters. See figures 7 and 8. Moreover the api frangible roof design standard has been further limited to tanks having a conical roof where the ratio of rise to run of the roof does not exceed two inches 51mm in twelve. Emergency relief venting for asts.

The roof slope must not be greater than 1 5 for bsen 14015 and 1 6 for api 650 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.