A method of assembling a synthesis gas (syngas) cooler for a gasification system includes positioning a dip tube within a shell of the syngas cooler. The dip tube is configured to quench the syngas flowing through the shell and/or at least partially channel the syngas through the dip tube. The method also includes coupling an isolation tube to the dip tube such that the isolation tube is substantially concentrically aligned with, and radially outward of, the dip tube. The isolation tube is coupled in flow communication with a purge gas source and is configured to at least partially form a dynamic pressure seal. The method further includes coupling at least one of the isolation tube and the dip tube in fluid communication with a fluid retention chamber. The method also include at least partially filling the fluid retention chamber with fluid, thereby further forming the dynamic pressure seal.