What determines the dew point reading actually measured in the hot zone of a sintering furnace?
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Sr. Principal Applications Engineer
The dew point in the hot zone of a sintering furnace is a result of different sources of O2 reacting with the available hydrogen, creating moisture. Assuming there are no cracks in the muffle, water leaks in the cooling sections, or contaminated supply gases, then the following are some known sources of O2:
- Diffusion of outside air through the front and exit ends of the furnace, which is influenced by the atmosphere flow rates, door height, exhaust hood designs, flame curtains and plant pressure conditions.
- Air entrapped in the part, which is a function of part geometry.
- O2 content of the powder used, which is usually a known quantity as measured by the H2 loss number of the powder.
- Reduction of belt oxides.
- Reduction of metallic oxides present in brick-lined furnaces.
Once the dew point (H2O %) is measured, we then can control the oxidation/reduction potential by controlling the amount of H2 in the atmosphere, thereby adjusting the H2/H2O ratio as per the requirements of the material that is being sintered.
If you are having a process issue that you think may be related to dew point, please call Air Products at 800-654-4567.