EFRT-Emergency drains

[dkf]

We have some 30000 m³ tanks with diesel that, during storms, permit water draining via the emergency drains. The tanks are double deck external floating roof concept. Main drain is not capable in draining storm intensities, and roof cannot cope with heavy water loads.
The water that crosses the product in its way to bottom ends up mixing/dispersing to an undesirable degree.
There is a local idea to use a hose in these emergency drains, diverting the water directly to tank bottom. It is expected that this procedure will decrease water dispersion in product.
A test is mandatory, but there are some concerns that this new hose could get entangled with the main flexible drain.
I know that the best procedure would be to increase draining capacity, but this can be done only during tank maintenance.
The hose to divert water directly to bottom ( with supposed decrease in water dispersion) can be installed right away.
Comments are welcome.
TIA
dkf

 

[siamak60]

AS you know emergency drains are intended to save external floating roof from being immersed. I believe that you can redirect water from some adjacent deck support by drill a hole in their body and then place a short hose in each one, in this way your hose will not interfere with flexible drain pipe.

 

[dkf]

Thank you for your comment siamak60!
We have not considered this idea yet.
I will check the supports located in central area that are outside the main flexible drain movement area.
If feasible we will be able to increase emergency drain flow, that is clearly not sufficient.
Estimates show that during storms we can have water retention peaks reaching 60 cubic meters for 15 to 30 minute periods.
One 6" main drain and two 6" emergency drains for a 54 meter diameter tank is not sufficient in tropical sites.