Photo AI
An optical pyrometer is used to accurately measure the temperature of a furnace when a range of different heat treatment processes is being carried out - Leaving Cert Engineering - Question c - 2020
Question c
An optical pyrometer is used to accurately measure the temperature of a furnace when a range of different heat treatment processes is being carried out. (i) Explain... show full transcript
Worked Solution & Example Answer:An optical pyrometer is used to accurately measure the temperature of a furnace when a range of different heat treatment processes is being carried out - Leaving Cert Engineering - Question c - 2020
Step 1
Explain the importance of accurately measuring furnace temperature when heat treating steel.
Answer
Accurate measurement of furnace temperature is critical during the heat treatment of steel for several reasons.
Firstly, various heat treatments require specific temperature ranges to achieve desired mechanical properties. For instance, quenching, tempering, and annealing processes all rely on precise temperatures to ensure the steel attains properties like hardness and ductility.
Secondly, different compositions of steel react differently to temperature changes. Therefore, accurate temperature monitoring is necessary to avoid adverse effects such as warping, brittleness, or incomplete heat treatment.
In summary, precise temperature measurement is vital to ensure that the furnace operates within the required specifications, leading to consistent and reliable steel properties.
Step 2
Describe, with the aid of a diagram(s), the operation of an optical pyrometer.
Answer
The optical pyrometer functions by comparing the intensity of light emitted from the filament of a lamp with that from the furnace. Here's a description of its operation:
- Light Source: A filament lamp is used as the light source. The current flowing through the lamp can be adjusted using a variable resistor, allowing control over the light intensity.
- Viewing Mechanism: The optical pyrometer has an optical lens that focuses the light from the filament and the furnace onto a viewing door.
- Filament Monitoring: The filament's brightness is adjusted to match the colour of the light from the furnace. There are three potential outcomes:
- Filament too bright: Indicates the furnace temperature is higher than desired.
- Filament not bright enough: Suggests the furnace temperature is lower than required.
- Brightness matches: Confirms the temperature is correct.
- Temperature Scale: The optical pyrometer includes an adjustable power scale that allows the user to read the temperature of the furnace as the filament brightness is matched.
The process ensures a quick and accurate temperature reading, which is crucial for effective heat treatment.