The most common cause of overheating and failure of boiler tubes is the formation of hard scale on the boiler tube surfaces. This is caused by calcium and magnesium in the boiler water. When untreated boiler water is heated, this calcium and magnesium will precipitate from the solution to form hard scale on the tube surfaces.
In addition to the overheating and eventual failure of the boiler tubes due to scale, efficiency is also decreased in the short-term because of the scale’s insulating effect on the heat transfer surfaces. A layer of scale just 1/8 inch thick can cause as much as 20-25 percent loss in efficiency – heat lost up the boiler stack.
So our test your knowledge question is: In addition to chemical treatment, which of the following is a devise for reducing scale buildup?
- system filter
- blowdown control
- descaling snake
- burner flame diffuser
The answer: 2. blowdown control
Boiler blowdown is the removal of water from a boiler. Its purpose is to control boiler water parameters within prescribed limits to minimize scale, corrosion, carryover, and other specific problems. Blowdown is also used to remove suspended solids present in the system.