The standard model for FB-D is 3-pass, wet-back, and corrugated furnace boiler. In the first pass, the flame and high temperature flue gas flows from the front to the back of the furnace; Through the second pass pipes, high temperature flue gas flows from the combustion furnace to the front chamber; In the third pass, the flue gas passes through the third pass pipes to the back of the boiler stack and vents out. Corrugated furnace highly increases the heat exchange area, heat transfer efficiency and reduces the possible damage to the boiler durability caused by heat expansion and cold contraction.

The factory also supplies 4-pass, wet back corrugated furnace boiler upon customer's request.