cone said:
our tank guys were saying the LNG tanks are designed for 150 mph gusts
no clue if that's really true or where and how it shows up on the design documents, but i'm pretty curious as to what those roofs are going to look like in the morning
also, what are the flare stacks designed for? i assume all the boil off gas from the tanks is getting flared during this event. it's got no place to go and the atmosphere is going below normal pressure. that's no big deal, but still this is something that only gets discussed in HAZOP rabbit holes in my experience.
Flare stacks are usually made for the same wind load as buildings. On projects, we have a Project Design Data (PDD) that will state the design codes and limits for everything (minimum temps, max temps, max air cooler design temps, max wind speed/direction, etc.)
Some of the issues I've seen with brownfield expansions (existing sites with new equipment or expanding current production) is that the old stuff stays the same and the new stuff is designed to new standards. For example, there were only 4 LNG sites from ~1970 to about 2000. So those built then (Trunkline, Cove Point, Southern, can't remember the other) were built to different standards. Wind speeds would be much less (probably Cat 2 or 3 max), storm surge less and design pressures. Once things changed in ~2000, more import sites built, but to different standards after all the storms. So now the older sites are trying to leverage existing equipment, but still handling 'new' design conditions.
Look at Arkema after Harvey. All their generators and chilling equipment was at 5' above the ground (or less). Why? Above what anyone would thought the water could get to. But they didn't listen to refineries and others closer to the coast, who after Ike flooded them, moved equipment higher.
I think a lot of the older sites are going to look like hell; tanks will be partially destroyed. I doubt you'll have loss of containment, but I could see major insulation missing and/or pipes ruptured. If you get flooding and the horizontal pipes going to the tank peeled away with storm waters, you will pull the pipes off the tank. When/where it rips will tell how the tanks will fare. I know on Trunkline, those tanks are single wall containment; ALL new tanks are double wall containment.
At another site I was at, Harvey ripped the roof off a control room building that was fairly new. Destroyed the inside and everything inside (control room, engineering offices, conference room, etc.). Building was designed for explosion and Cat 3. Luckily the computers were wrapped in plastic, so not a lot of hardware was destroyed, but you had the plant running in trailers for 6 months while you fixed the "safe" control room building.
BOG should be compressed unless they shut down everything. When designing for BOG, you'll have a pressure change with max outside ambient temperatures in holding mode. You'll do everything at once to see what the max boil-off rate is; this is what the tank vendor should be doing to ensure it won't go crazy. The RVs might lift for a bit, but that won't be too long. Usually just when the eye goes overhead. But venting the gas in a hurricane should allow for good 'mixing' and diffusion of the gas!
~egon