Do not wait for a break. Two of these five signals is enough to schedule a replacement.
A broken element is an emergency. A worn element is a planned maintenance item. The difference is measurement.
Measure cold resistance and compare with the commissioning value.
| Family | Watch | Replace |
|---|---|---|
| FeCrAl | +10% | +15% |
| Ni-Cr | +7% | +12% |
If the rate is accelerating — say 5% in six months then 8% in the next six — you are near end of life.
With the furnace isolated, inspect for:
Same power, longer time to reach temperature means the element is delivering less useful heat. Log the commissioning heat-up curve and compare. A 15% increase is a warning.
Clamp the current per phase. A fall means resistance has risen. In a three-phase furnace, a phase imbalance above 10% needs investigation.
Look for local hot spots, uneven temperature distribution, or terminals running much hotter than the element body. A 50 °C local difference is worth a closer look.
| Check | Interval | Threshold |
|---|---|---|
| Cold resistance | quarterly | +10% FeCrAl / +7% Ni-Cr |
| Surface condition | twice a year | scaling, thinning, distortion |
| Heat-up time | twice a year | +15% |
| Running current | monthly | −8% or 10% phase imbalance |
| Thermal image | quarterly | 50 °C local difference |
Two signals triggered: schedule a replacement. Three or more: replace at the next opportunity.
A customer who used to replace on failure had four unplanned stops a year at roughly 20,000 each. After switching to signal-based replacement, it dropped to one. Element spend rose about 30%; total cost fell about 60%.
