And don’t get me started about dirt in the bark and chips. It will eat a boiler up. The dust and sand act just like sandblasting on the boiler tubes. They will erode and begin to leak.
How do you get dirty fuel? First you drag the logs out of the woods with a skidder and collect dirt. Then pile it on the ground at the mill prior to burning. The sand and dirt that doesn’t go up into the hot gas stream turns to glass on the boiler grates and cause a mess. Grates have to be constantly raked.
Its also amazing to see a year-old induced draft fan with blades made of hard surface weld overly that have been completely destroyed by the dirt and sand.