What is ΔT in thermography?

ΔT (delta T) is the temperature difference between the measured component and a reference point (typically a similar component under the same load, or ambient temperature). It is the primary severity indicator in thermographic inspections.

What severity levels are used?

Common severity classification uses four levels: Minor (monitor), Intermediate (plan repair), Serious (repair soon), and Critical (immediate action). The ΔT thresholds vary by component type and industry standards.

What ΔT thresholds apply to electrical panels?

For electrical connections (ΔT over ambient): 1-10°C = Minor, 11-20°C = Intermediate, 21-40°C = Serious, >40°C = Critical. These thresholds are based on NETA MTS standards and are widely used in electrical thermography.

How does load affect thermography readings?

Temperature rise is approximately proportional to the square of the current (I²R heating). When equipment is not at full load, findings may be worse at full load. Always record the load percentage during inspection and extrapolate to full load conditions.

What are the main standards for thermography?

Key standards include ISO 18434 (condition monitoring by thermography), NETA MTS (electrical maintenance testing), ASTM E1934 (IR building surveys), and IEC 62446 (PV systems). ISO 18434 provides the overall framework for machine condition monitoring using IR.

Ferramenta de Engenharia Gratuita

Limites de temperatura de termografia

Classifique os resultados da inspeção infravermelha conforme a ISO 18434. Insira o tipo de componente e o ΔT medido acima da referência para obter a classificação de severidade e a ação recomendada.

ISO 18434NETA MTSInspeção IR

Classificação

Severidade

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ΔT medido

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Prioridade

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Ação Recomendada

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Limiares de temperatura para este componente

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Indicador de temperatura

Componentes Elétricos (NETA MTS, ΔT acima da ambiente)

ΔT (°C)	Severidade	Prioridade	Ação
1–10	Menor	4	Monitorar, reparar quando conveniente
11–20	Intermediário	3	Planejar reparo na próxima parada programada
21–40	Grave	2	Reparar o mais rápido possível
>40	Crítico	1	Ação imediata — risco de falha/incêndio

Componentes mecânicos

Componente	Menor	Intermediário	Grave	Crítico
Carcaça do motor	<10°C	10–25°C	25–40°C	>40°C
Caixa do rolamento	<10°C	10–20°C	20–35°C	>35°C
Acoplamento	<5°C	5–15°C	15–25°C	>25°C
Desidratador de vapor	<20°C	20–40°C	40–60°C	>60°C
Isolamento	<5°C	5–15°C	15–30°C	>30°C