The large convective heating surface area in the 2nd and 3rd pass tubes ensures maximum heat transfer. Large water holding and steam holding space are extremely helpful in overcoming the fluctuating steam demands needed for the process. High dryness fraction of the steam increases the usable heat. Dry steam generated, helps in reducing the processing time, saves steam and improves the quality of processed goods.

Three-pass steam boilers are so-called because the combustion gases that are produced inside them in the burner go round a circuit that has three parts before leaving it:
• The first pass of gases takes place when they leave the burner for the combustion chamber.
• The second pass of gases is through the inversion chamber, which is completely cooled by water.
• The third pass of gases sends them back in the opposite direction towards the rear gas chamber.