certified ASME Boiler Water Tube Membrane Water Wall for recycling water are membrane walls that are made of tubes welded together with or without a strip of metal in between. These walls form the enclosure of the coal combustion chamber. Water wall tubes are also referred to as the evaporator section; they contain water mostly in liquid form which gradually evaporates as it rises in the boiler. Application certified ASME Boiler Water Tube Membrane Water Wall for recycling water  are membrane walls that are made of tubes welded together with or without a strip of metal in between. These walls form the enclosure of the coal combustion chamber. Water wall tubes are also referred to as the evaporator section; they contain water mostly in liquid form which gradually evaporates as it rises in the boiler.