The liquid seal drum is a specially designed vessel containing a predetermined level of water in the base of the drum. The main purpose of the liquid seal drum is to stop flame propagation in the unlikely event of flashback. The liquid seal also acts as a large check valve so that gas can not travel upstream for any reason. A third function of the liquid seal is to disentrain liquid droplets. Liquid seals can be designed as independent vessels or as an integral part of flare risers.
The dynamic (velocity) seal is a simple innovation which ensures significant cost savings over time. The reverse conical baffle design reduces flow area in the flare tip while simultaneously increasing purge gas velocity. In combination with the dynamic seal, a constant flow of purge gas will maintain a seal in flare system, ensuring that air infiltration does not occur. A vortex effect is created as the exiting purge gas inspirates intruding air. This intruding air is drawn out of the boundary layer and into the exiting purge gas flow column, thus purging the flare tip. This technology is a standard on various flares.