Samia Italia utilizes buoyancy and velocity seals to keep air from flowing back into the flare header and to reduce the amount of required purge gas.
Buoyancy seals are separate, larger drums which use the difference between the buoyancy of air and the buoyancy of purge gas to seal the flare from the air.
Velocity seals increase the velocity of purge gas within the seal thus that air is pushed out and prevented from entering the system below the seal. Compared to a gas seal, a velocity seal is less complex, needs less maintenance, and has a lower impact on the stack design; though, the gas seal offers a greater reduction in purge gas requirements than the velocity seal.