Want to know more about Metal-Ceramic Thermocouple Protecting Sheath Grade LT-1?

PyroSheath LT-1® — High-Performance Metal-Ceramic Thermocouple Protection Tubes

PyroSheath LT-1®, often referred to as a “metal ceramic” or cermet sheath, is a high-performance thermocouple protection solution engineered from a composite of chromium and aluminium oxide (alumina). This advanced slip-cast material combines the durability of metal with the stability of ceramics, making it particularly well-suited for extreme high-temperature environments such as industrial furnaces.

Key Features and Benefits

• Superior Oxidation Resistance: Withstands oxidising atmospheres up to 1370°C, providing exceptional longevity in harsh environments.
• Excellent Thermal Conductivity: Comparable to stainless steel, allowing for rapid response to temperature changes—ideal for precise pyrometric measurements.
• Resistance to Wetting: Resists wetting by most molten metals, making it highly effective for immersion applications.

Material Description

LT-1 is a dense, hard, and abrasion-resistant metal-ceramic material manufactured through a controlled slip-casting process. The composite structure harnesses the unique properties of chromium and alumina to offer:

• High thermal conductivity
• High-temperature strength
• Chemical stability
• Excellent resistance to corrosive gases such as SO₂, SO₃, and HF
• Low porosity—minimising gas permeability under standard industrial conditions

Its dual-phase composition forms a tightly bonded chromium oxide layer on the metal phase, which enhances oxidation resistance and extends service life in extreme thermal and chemical environments.

Connector Fittings

Type A

• EMT connector with gland compression
• Zinc-plated steel body with malleable iron nut

Type B

• Cold rolled steel fitting (35 mm Hex)
• Cemented to the tube to provide threaded connections for mounting

Note: To order tubes without connectors, use the same part number without the suffix “F”.
 To calculate the weight of the tube without connector “A”, subtract 45g from the listed weight.

Tube Tolerances and Specifications

• Inner Diameter: Accommodates a 13 mm diameter × 50 mm long probe throughout the full length.
• Straightness: Maximum deviation of 5 mm per 300 mm length (chord-to-arc measurement).
• Usage Notes:
  • Compatible with B & S Wire Gauge 8 or smaller.
  • A ceramic primary tube is recommended when used with noble metal thermocouples.
• Availability: Standard sizes available from stock. Allow up to 10 working days for made-to-order Type B connectors.
• Packaging: Each unit is individually boxed for protection during shipping.

Recommended Applications

LT-1 sheaths perform reliably in a range of demanding thermal processes, including:

• Molten metals:
  • Copper and brass (to 1150°C)
  • Zinc (to 870°C)
  • Lead (to 340°C)
  • Silver solder and tin
• Industrial gases:
  • SO₂/SO₃ (to 1370°C)
  • HF gas (to 1095°C)
• Furnaces:
  • Steel mill soaking pits (to 1370°C)
  • Open hearth furnace checker chambers (to 1345°C)
  • Glass furnace atmospheres
• Chemical and refining environments:
  • Calcining kilns and pelletising chambers (to 1200°C)
  • Taconite refining operations
  • Fluid bed cement processing (to 1315°C)
  • Boiling sulphuric acid – 97%
  • Barium titanate and magnesium oxide kilns
• High-temperature metal processing:
  • Basic steels and slags (up to 1730°C intermittent; 1370°C continuous)
  • Copper matte, borax flux

Non-Recommended Applications

LT-1 is not suitable for the following:

• Molten aluminium
• Cryolite
• Acid and carbide slags
• Tin (stannous) chloride (above 400°C)
• Copper alloys exceeding 1150°C
• Molten glass
• Boiling sulphuric acid – 10%
• Carburizing/nitriding atmospheres
• Barium chloride salt baths
• Sodium nitrate salt baths

Performance Considerations

• Preheating Recommended: To avoid thermal shock, preheat the tube to approximately 480°C before immersion into molten metals at 1095°C or higher. Alternatively, hold the tube just above the molten metal for about 1 minute before immersion.
• Thermal Shock & Impact: While LT-1 outperforms ceramics in resistance to shock and mechanical stress, it is still more fragile than metallic alloys. Handle with care during installation and use.
• Wear Resistance: Excellent resistance to sliding friction and high-temperature abrasion. Rockwell hardness rating of C37.
• Gas Impermeability: Effectively blocks penetration of gases such as SO₂/SO₃ even after prolonged exposure in industrial conditions.

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