Rim Vent Requirment

Dear All;

The stabilized condensate "8 psia RVP" is stored in external floating roof tank with double seal "Primary Mechanical shoe plat seal
and rim mounted secondary seal".

The tank is fitted with two 6" rim vents "set point 2.2 mmbarg" to release any pressure exist in the vapor space between the liquid surface and the seal. To protect rim seal that have design pressure 3.5 mmbarg as per attached sketch.

Now the two rim vent are opening all the time and there are continuous release of vapor to ATM. Although, RVP of the condensate is measured regularly and it is value around 7.5 psia.

 Rim vent requirment.png   65.95KB   8 downloads

Does rim vents are needed in this case or not? and if it is needed is it normal that rim vent is open all the time.

RVP is measured by a gauge. The units of measurement are not psia. Vents are needed to protect the floating roof.

 

The stabilized condensate "8 psia RVP" is stored in external floating roof tank with double seal "Primary Mechanical shoe plat seal
and rim mounted secondary seal".

 

The tank is fitted with two 6" rim vents "set point 2.2 mmbarg" to release any pressure exist in the vapor space between the liquid surface and the seal. To protect rim seal that have design pressure 3.5 mmbarg as per attached sketch.

 

 

Now the two rim vent are opening all the time and there are continuous release of vapor to ATM. Although, RVP of the condensate is measured regularly and it is value around 7.5 psia.

 

Rim vent requirment.png

Does rim vents are needed in this case or not? and if it is needed is it normal that rim vent is open all the time.

Hi,

The external floating roofs need protection mostly within fill and empty activities. Hence although the most external floating roofs are equipped with rim vent to release the vapor below the tank's peripheral seal, they are actually a source of emission...