How is the fire boundary determined for vertical fire-tube boilers?
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How is the fire boundary determined for vertical fire-tube boilers? If the fire level cannot be determined, the position of the water gauge cannot be determined either. I seek advice from those who are more experienced.
For the LSG type, it is determined by comparing the top of the furnace chamber with the upper end of the curved water pipe in the smoke box, taking the higher of the two values; the lowest safe water level is 100 mm above the highest fire level.
In shell-and-tube boilers, the lowest water level must be 100 mm above the highest fire boundary. For flue tubes such as those used in stack vents, there is no clear definition for the highest fire boundary; generally, it is considered to be the seam around the stack vent.