Rim Vent for External Floating Roof

[Chance17]

I am involved with evaluation of a 70-ft dia by 45-ft tank with external floating roof.
When originally built (1978), the roof rim area has a 6" pallet vent with 1/2 oz set pressure.
Today the pallet vent is removed and the connection blinded.
The Client feels the pallet device was only window dressing - not serving a significant function.
Reference literature indicates the device vents gas accumulations which could lift the roof away the the liquid surface.
The references claim at extremes, too much accumulated gas could cause the roof to sink.
Question: On a scale of 1-10, how important is having a rim vent.

 

[IFRs]

in my opinion zero or less

 

[tankerator]

Agreed. On our site, they have blinded all rim seal vents as they were only used for the foam log type seals that they no longer use.

The only case where gas build up would be a possibility would be with something like oil spiked with methane. Hopefully this would be degassed before entering the storage tank.