Why does the outer diameter of the furnace tube in a heating furnace increase?
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Does the furnace tube in a heating furnace expand during operation? If so, why does it expand? By what percentage can it expand at most, and how much expansion is acceptable?
Thermal expansion, as well as thinning due to corrosion
It gradually grows larger due to the formation of bulges
It mainly refers to the change in the outer diameter of the furnace tube
Thermal expansion, as well as thinning due to corrosion by 5%
There is vaporization, to prevent exceeding the critical flow velocity, therefore the diameter needs to be increased.
With a higher flow rate, turbulence should allow for better heat transfer, right? Why is it necessary to prevent the flow rate from exceeding the critical value?
This is high-temperature creep: when the furnace tube remains in a high-temperature state for an extended period, its microstructure deteriorates, and the structure of the grain boundary carbides changes. The durability, strength, and ductility of the furnace tube decline, and in severe cases, axial cracks occur in the furnace tube. It is necessary to regularly check the creep amount of the furnace tubes; a value exceeding 5% indicates that they meet the criteria for disposal.
I’ve learned it; you’re right. But I still want to ask whether there is a situation where the diameter of the furnace tube increases
The diameter of the furnace tube increases due to creep, and when this increase exceeds 5%, it meets the criteria for scrapping. The creep strain measures the deformation of the diameter of the furnace tube
With creep, does the diameter generally decrease?