Open topped water tank, question about wind generated wave action

[robsalv]

Hi Folks,

Currently tyre kicking API 650 and various forums regarding whether there might be any specific issues to be concerned about in respect of wind generated waves inside a 100 ft diameter, 48ft high, all welded carbon steel open topped tank. The tank construction is circa 1960 with the wind girder design based on API 12C of the era.

We are expecting some decent winds - however it's already quite gusty. I was just up the top of the tank looking in and in addition to the obvious ripples and roughened water surface, there is a noticeable wave like movement in the surface of the water - quite shallow at this stage. The water is not sloshing. The water level is some 4ft from the top of the tank with the wind girder is about 2ft from the top of the tank.

FWIW, the tank used to have a wave breaker raft many years ago which long since broken apart and been disposed of.

I suspect the tank will be ok given that it must have seen strong winds many times before, but now that the question has entered my mind and the answer is not immediately leaping to hand as a result of my reading, I thought I'd put it out to the community.

Any thoughts?



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"Life! No one get's out of it alive."
"The trick is to grow up without growing old..."

 

[Nawfal]

The most dangerous effect of gusty wind is manifested in empty tanks rather than full tanks. Even for domed roof tanks, it is noticeable that the most critical region affected by wind loads can be observable at dome-cylinder intersection corner of the cylindrical storage tank, which is attained as result to the impressive action of uplifting force applied to the dome roof.

 

[LittleInch]

It's a fair question.

Wave height for open water can be calculated - see sites like this

http://woodshole.er.usgs.gov/project-pages/coastal_model/Tools/fetch_limited.html

When you put in 22m/sec ( close on 50 mph) and 30m, you get a wave height of about 9cm.

The issue is probably one of wave splash once it hits the far wall. So probably need double the wave height before the splash over tops the wall - say 20cm / 8 inches or maybe a tadge more.

any splashing is though likely to be blown by the wind beyond the tank, so maybe a bit of caution is good.

I can't see it doing anything to the tank though - not enough energy.

Depends on your wind velocity.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[robsalv]

Thanks for the replies.

After trawling standards and codes, I figured that wind assisted wave action wasn't a huge issue. So it's reassuring to get your replies. Naturally, so long as the tank was designed to structurally withstand design wind loads and remains fit for purpose, this tank should be ok from a wind point of view.

There's plenty of concern in the codes about water sloshing and wave height in respect of earth quakes - and rightly so. Fortunately, my work place is in a low risk earthquake zone.

Cheers gents.

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"Life! No one get's out of it alive."
"The trick is to grow up without growing old..."