5 furnace setups, Steam Methane Reformer Tubes: Type K or N, φ0.5–1.0 mm
| Application | Typical conditions | Recommended wire |
|---|---|---|
| Steam Methane Reformer Tubes | Catalyst tube wall temperature in hydrogen and syngas plants. 800-950 °C, hydrogen-rich atmosphere. Accuracy directly affects tube life prediction. | Type K or N, φ0.5–1.0 mm |
| Distillation Columns | Tray and overhead temperature in crude oil and petrochemical fractionation. Multiple measurement points per column for composition control. | Type K or J, φ0.5–2.0 mm |
| Reactor Vessels | Exothermic reaction temperature control in polymerisation, alkylation and hydro-processing units. Safety-critical — thermocouple failure can lead to thermal runaway. | Type K, φ0.5–1.5 mm, dual redundant |
| Pipeline Monitoring | Buried and above-ground pipeline temperature for flow assurance and leak detection. Long cable runs — consider extension wire voltage drop. | Type K or T, φ1.0–2.0 mm |
| Flare Stack | Continuous flare pilot flame verification and stack gas temperature. Exposed to weather, corrosive gases and thermal radiation from the flare. | Type K with sheath, φ1.5–3.0 mm |
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Corrosion resistance
H₂S, HCl and sulphur compounds attack standard thermocouple alloys. For reformer and cracker service, specify MI cable with INCL600 sheath. For chlorine-containing streams, Type J is preferred over Type K.
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Safety integrity
Many petrochemical temperature measurements are safety-critical (SIL-2 or SIL-3). Dual redundant thermocouples with independent cable runs are standard practice for reactor over-temperature protection.
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Long cable compensation
Pipeline and tank-farm runs can exceed 500 m. Use extension-grade compensating cable with heavier conductors (φ0.8 mm or larger) to minimise loop-resistance error at the instrument input.
Frequently Asked Questions
Which thermocouple wire is used in steam methane reformer tubes?
Type K or N, φ0.5–1.0 mm, at 800–950 °C in a hydrogen-rich atmosphere. Reformer tube wall temperature drives tube-life prediction, so measurement accuracy has a direct cost consequence.
How is corrosion from H₂S and HCl handled?
MI cable with an Inconel 600 sheath for reformer and cracker service. For chlorine-containing streams, Type J is preferred over Type K.
What is standard practice for safety-critical reactor measurements?
Dual redundant thermocouples with independent cable runs. Many reactor over-temperature loops are SIL-2 or SIL-3 rated, so a single sensor is not acceptable.
How do you handle cable runs of several hundred metres?
Use extension-grade compensating cable with heavier conductors — φ0.8 mm or larger — to minimise loop-resistance error at the instrument input.
Bottom line: Petrochemical service punishes the wrong alloy quickly: H₂S, HCl and sulphur compounds attack standard thermocouple alloys, so specify MI cable with an Inconel 600 sheath for reformer and cracker work, and Type J for chlorine-containing streams. Where the measurement protects against thermal runaway, dual redundant thermocouples on independent cable runs are the baseline.