Boiler tip of the month – Monitoring of the water quality
Water hardness/limescale
In addition to other harmful ingredients, freshwater also contains alkaline earths, often referred to as “hardness”. We are also familiar with this from the deposits in the kettle or the coffee machine. A limescale layer of only 1mm can significantly reduce heat transfer on the water side. This can lead to significant damage, particularly to components that are subject to high thermal stresses such as the flame tube or the tube plate of the internal reversing chamber.
In this case, the existing softening system has been consistently overloaded by additional in-plant consumers. There was no hardness monitoring and the overloading was therefore not detected.
As a result, residual hardness also ended up in the boiler in which layers had formed on the water side.
These layers reduced the heat transfer which in turn caused local overheating and cracks in the tube plate between the holes.
Damage:
- Cracks in the ribs of the tube plate of the smoke tube due to overheating in this area
Cause:
- Hardness invasion and deposits in water space
Remedy:
- Keeping of a boiler log book with regular entries on the water quality and check of adherence to water quality guideline
- Use of residual hardness monitoring