In a wetback design the chamber where gases turn from the furnace into the second pass is water-cooled, so there is little refractory to crack and maintain, and more of the heat goes into the water. A dryback boiler instead uses a refractory-lined rear door that swings open for easy access to the tubes and tube sheets, at the cost of periodic refractory repair.
Rear door refractory is falling apart again, next boiler we buy is going to be a wetback.
Also heard as
- wet back
Related terms
Scotch marine boiler
A horizontal packaged firetube boiler with a large internal furnace tube and two to four gas passes.
Pass
One run of combustion gases from end to end through a boiler before they turn or leave.
Furnace
The part of a boiler where the fuel actually burns, such as the big flame tube of a firetube or the water-walled box of a watertube.
Tube sheet
The thick flat plate at each end of a firetube boiler shell that the tube ends are rolled or welded into.