Heat-treat furnace Troubleshooting

Symptoms: Uniformity survey fails, properties scatter by basket position, rework or re-test of loads. Likely causes: Failed or drifting heating elements and zones; Damaged insulation or door seals; Load and fixturing beyond qualified pattern. Fixes: Test elements and zone control loops; replace weak elements and retune loops after element changes. Repair refractory and seals; cold air ingress kills corner uniformity. Respect the qualified load pattern; dense loads shade thermocouple zones. Prevention: Scheduled uniformity surveys, element and loop PM, load-pattern discipline.

Symptoms: Surface defects after treatment, hardness fall-off at the surface, sooty deposits inside the furnace. Likely causes: Atmosphere composition off; Air ingress; Wrong burnout or recovery procedure. Fixes: Verify carbon potential or protective atmosphere flow and analysers; calibrate probes on schedule. Fix door seals, fan shaft seals and sample ports; tramp air oxidises parts and burns atmosphere. Follow soot burnout procedures; running dirty changes surface chemistry unpredictably. Prevention: Probe calibration cadence, leak checks in PM, atmosphere trend logging per recipe.

Symptoms: Energy per tonne climbs quarter on quarter, longer heat-up, burners cycling hard. Likely causes: Insulation degradation; Burner tuning drift; Underloaded cycles. Fixes: Survey shell temperatures with a thermal camera and repair hot spots in the lining. Tune air-fuel ratios and check recuperator performance; rich or lean burn wastes fuel. Schedule full loads where the recipe allows; half-empty furnaces burn the same energy. Prevention: Energy per load trending, shell thermal surveys, burner tuning cadence, load planning.