FRANGIBLE ROOF AND COOLING RING 2

[judge503]

I am using a frangible roof for emergency vent and their is a water cooling ring for the roof.
In the case of exposure , the failure will in the roof to shell joint .
how can this failure happens with the existance of the cooling water system which will prevent the roof due to connection with the riser and on roof plates

please advise

thanks in advance

 

[Duwe6]

Short Answer: It won't work.

Long Answer: It has been proven by MANY tank explosions that it is hard to get the roof-seam to fail. Flat-bottom tanks 'want' to burst at the floor-to-shell joint. And it is essentially impossible to have a frangible roof on a 10-metre/35-ft tank or smaller.

If your tank is 20m / 70-ft or larger, a carefully designed and built frangible roof is possible. The roof-to-compression ring weld must be kept small and 'cold'. A nice 'hot' bead that penetrates both pieces is the last thing you need.

Any restraints or roof reinforcement, like your cooling ring, or a roof platform, or numerous piping attached to roof-mounted nozzles will help hold the roof on, and try to put the failure into the floor-to-shell joint. I would add anchor bolts with 'chairs' to help keep the shell attached to the floor.

With anchors & chairs, and a tiny, 'cold' roof weld, and the cooling ring supported by the shell and unconnected to the roof, a frangible roof may be possible.

 

[MJCronin]

Duwe6 gives sage advice...

Frangible roofs don't exist for smaller tanks. Emergency vents may be the only way for you to go...

For a detailed evaluation of the subject, consider:

http://www.thunderheadeng.com/wp-content/uploads/downloads/2010/09/Zhi_Lu_Thesis.pdf