Frangible Roof Documentation

[Olidin]

Hello,

I'm a new process engineer and I'm considering a emergency venting for a storage tank (200ft diameter). The tanks have open vents that are okay for normal venting (guided by API 2000). However, in case of fire or emergency venting, the open vents will not be enough. Then I proceed to consider frangible roof as mean of emergency venting.

I have no idea how a frangible roof tank is constructed. I read through API 650 12th Ed. 5.10.2.6 where they layout 5 conditions for compliance. However, would the designer indicate that roof is frangible anywhere? I found no documentation that explicitly state that the roof is frangible. Where do the engineer typically document these things?

I could go through the drawings and see if tank construction meets API 650 5.10.2.6, though I'm no expert in tank construction, and some information might not be available.

Any advice how to can find out if a roof is frangible?

Thanks

 

[fegenbush]

Roof frangibility is specified by the purchaser. One place to look to see if it was specified or provided is the data sheet. Section 11 of the data sheet relates to the details of the roof.

If it is not specified there, the only way to determine if the roof is frangible is by checking the drawings or tank. Since your tank is 200ft diameter, is is very likely that the roof will have sufficiently small reinforcement area to be considered frangible. The details of welding may dictate the final result.

 

[IFRs]

I'd have a hard time believing that your tank does not have a frangible joint. Go get the details of the shell-to-roof joint, either drawings or go there with a tape measure. If it is a 3x3x3/8 top angle with a 3/16 thick roof plate on a 3/4 in 12 slope and the weld between the roof plate and top angle is 3/16 fillet you are good to blow.