Dear Pete,

I've been out of pocket a bit and am just catching up.

I noticed something in your later comments that is unrelated to pipe stress. In case you haven't thought of it (apologies if you have), since the tank cone roof has external rafters, the roof/shell joint cannot be considered "frangible." Therefore, there must be adequate emergency venting capacity installed on the tank.

I had a client that ran into this. As I recall, the required venting capacity for their particular applications was so high that it was unrealistic to provide the needed capacity. In some cases, they rethought their "need" to have the rafters outside. In other cases, they did a "risk assessment" to rationalize being OK with the venting capacity they were able to reasonably get in, supplemented by equipment spacing and operational procedure reviews that made them feel comfortable.

Regards,

Vince Carucci

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Vincent A. Carucci
President
Carmagen Engineering
7 Waverly Place
Madison, NJ 07940

Visit our web site at http://www.carmagen.com