A leaking tube is usually a symptom of something else. Replacing tubes without finding the cause can mean the same failure happens again. Most failures trace back to a few causes.
Water-side causes are the most common. Scale forms when hardness deposits on the tubes. It insulates the steel from the water, the metal runs hotter, and the tube can bulge or crack. Dissolved oxygen in the feedwater causes pitting from the inside, often when deaeration isn't removing enough oxygen or make-up water use is high. A low-water condition can overheat tubes in minutes, which is why low-water cutoffs need regular testing. Boiler water chemistry that stays out of range corrodes tubes over months.
Fire-side causes involve combustion. A flame that is misaligned or overfired can impinge on tubes or the furnace wall and overheat one area. Short cycling and low return water temperatures can cool flue gas below its dew point, and the condensate that forms is corrosive. Oil burners running rich leave soot that holds moisture and sulfur against the metal.
Mechanical stress is the third cause. Cold starts and fast changes in firing rate make tubes expand and contract. In firetube boilers, repeated movement can loosen rolled tube ends at the tube sheet.
Signs to watch for: steam or water at the tube sheet or in the firebox, rising make-up water use, white deposits or wet soot at the tube ends, or water in the combustion chamber after shutdown.
We don't replace tubes; that work is done by a qualified boiler repair contractor. We check the combustion side, including flame shape, fuel-air ratio, cycling, and stack temperature, so a burner problem isn't contributing to the failure.
Related reading: What an Out-of-Tune Burner Really Costs, Excess Air and O2 and Boiler Room Combustion Air. See all of our services on the What We Do page.
Request a combustion check, or email service@combustionspecialists.com.
