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Have you ever sunk an EFR (External Floating Roof) tank roof due to heavy rain or snow loads?

Last fall we were observing MTG (Multi-function Tank Gauge) data from five EFR Tanks of a customers during heavy rainfall over three straight days. Typical Gulf Coast weather during Hurricane or storm season.


The MTG (Multi-function Tank Gauge) provided ambient and vapor pressure, temperature, density, as well as level and Mass. We then used the trending in the TG SOFT SERVER to go back and observe the history of these tanks prior to the rainfall, during the rainfall, as the rainfall slowed down, and finally when the rainfall stopped.


First, we monitored (trending) the level increase in the tank. This was in relationship to the increased weight on the roof (rainfall) pushing the measured level higher in the gaugewell. Finding that the increase in level was proportionate to the amount of water on the EFR roof. That a level measurement of water on an external floating roof is possible from a tank gauge (MTG).


We were told by our customer that a EFR roof would sink if 2 – 1/2″ of rainfall accumulated on the roof. All the EFR tanks were around 2” of water on the roof. The drain hoses are designed to manage the rainfall drainage, but not to this volume of water due to days of continual heavy rains.


On three of the five EFR tanks the trend of the roof water level showed a steady decline with the slowdown and stoppage of rain. On the two other tanks the trend showed erratic drainage, not steadily draining. It was determined from the trend and later at the tanks that the drain hoses were fully clogged or partially clogged. Those two tanks drain hoses were immediately cleaned by the customer.


So, a tank gauge (MTG) can be used to prevent the possible sinking of an EFR by measuring and calculating the amount of water on the roof (Level and Mass) and the monitoring (trending) of the drainage rate.


MTG “Multi-function Tank Gauge” provides Loss Control for Liquid Bulk Storage Tanks, does your gauge?