SUNKEN FLOATING ROOF

[gfnelson]

We are working for a customer who has a 222' d x 32' h crude oil tank with an internal floating roof. The IFR sunk during an oil movement and is now resting (they think) on its legs. The area below the IFR is full of oil and there is 2' of oil on top of the IFR. Our objective is to strip the 2' of oil off of the roof to remove the weight so they can drain the area below the roof. The work plan is to use King Vacs to pull the oil over the top (approximately 22' up and 32' down), and once a siphon effect is established, divert the flow to a pump and pump the oil downline. We are having problems controlling the vapors in the space between the product and the fixed roof to allow us to strip the oil. Currently, we are injecting nitrogen into the tank and seem to be making slow head way. I am looking to offer the customer some new ideas and/or validate the current plan with case histories.

Does anyone have experience with a similar situation or refer me to someone who does?

Does anyone have any other ideas to;

1. Supress the LEL and create an oxygen deficient environment, and

2. Remove the oil from the top of the roof.

Thanks,

Jerry Nelson
FSS- New Orleans, LA
225-279-0022
nelson.gerard@cleanharbors.com

 

[IFRs]

If this is an aluminum IFR, you could just pump out from under it, let the IFR collapse and then go in and tear it out. The collapse will not damage the tank.

 

[JJPellin]

I assume that the IFR sunk because the tank was filled with a product too light to float it. I also assume that the IFR is likely not severely damaged so you probably don't want to colapse it and cut it out. Based on those assumptions, it sounds like you have the right plan. I am not a tank expert but I am not aware of any better options.

 

[unclesyd]

One method I am aware of being used is cutting a hole just above the liquid level, to get better suction head. This was done on Cyclohexane and Stoddard Solvent storage tanks.