Kiln migration refers to the rotational difference between a kiln shell and tire. It indicates the gap that develops between the two surfaces. Higher or lower values outside the recommended range of 6-8 mm are dangerous. Kiln migration occurs because the shell rotates faster than the tire due to their circumference difference, causing their linear movements to diverge slightly with each revolution. Migration can be calculated by marking lines on the shell and tire and measuring their displacement after several revolutions. Shims of the proper thickness can be used to take up space between the shell and tire and bring migration back within safe limits.

1. KILN MIGRATION
Presented By: Faisal Nadeem
Trainee Engineer

2. KILN MIGRATION
It is relative moment between the kiln shell and kiln tire
Also defined as rotational difference between kiln shell and kiln tire
Migration indicates the gap between kiln shell and the kiln tire
Higher or lower values rather than recommended range of migration is
dangerous

3. KILN MIGRATION
Kiln Shell Outer diameter is always smaller than the inner diameter of Tire
Due to this circumference difference, kiln tire rotates slower as compared to
kiln shell
Difference in the linear movement, of the both surfaces, can be observed in
each revolution of kiln.
Allowable migration is normally 6 mm to 8 mm

4. KILN MIGRATION

5. KILN MIGRATION

6. CALCULATION OF MIGRATION
Migration can be calculated by marking 2 lines, coinciding each other on kiln
tire and shell
Observe both lines after one revolution
To get accurate results, observe both lines after 10 revolutions
Then divide migration value (mm) by 10 (revolutions)
So, migration per revolution can be easily be calculated

7. How to get Migration back in Limit?
Find the Hot Air Gap
• 𝐴𝑖𝑟 𝐺𝑎𝑝 =
𝑀𝑖𝑔𝑟𝑎𝑡𝑖𝑜𝑛 𝑉𝑎𝑙𝑢𝑒 (𝑚𝑚)
𝑃𝑖 (3.14)
Allowable hot air gap is 3mm to 4mm
Find the Shim Thickness which need to be placed between shell and tire
• Sℎ𝑖𝑚 𝑇ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠 =
𝐶𝑎𝑙𝑐𝑢𝑙𝑎𝑡𝑒𝑑 𝐴𝑖𝑟 𝐺𝑎𝑝−𝑅𝑒𝑐𝑜𝑚𝑚𝑒𝑛𝑑𝑒𝑑 𝐴𝑖𝑟 𝐺𝑎𝑝
2

8. How to get Migration back in Limit?
Example: If the kiln is running with migration/rev of 36mm.
• 𝐴𝑖𝑟 𝐺𝑎𝑝 =
36
3.14
= 11.5
• Sℎ𝑖𝑚 𝑇ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠 =
11.5−3
2
= 4.25 𝑚𝑚
• So, the required shim thickness is 4 mm

9. THANKYOU.
.