High Purity Alumina Ceramic Capillary for Thermocouple and Gas Analysis Systems

Alumina Ceramic Capillary Applications

• Industrial Temperature Measurement and Thermocouples

  ✅Key Advantages

  1. Precise Lead Insulation in High-Temperature Probes
  Alumina ceramic capillary keeps thermocouple legs separated and insulated up to around 1,600–1,700 °C, helping temperature probes maintain stable output and service life in industrial furnaces.

  ✅ Problem Solved

  In continuous heat-treatment furnaces and aluminum melting lines, thermocouples often fail when lead wires shift or short in metal or glass tubes. By switching to multi-bore alumina ceramic capillary with defined ID and controlled straightness, one OEM reduced probe failure rates in a furnace line from about 12% per year to below 3%, while extending typical replacement intervals from a few months to more than half a year. This reduced emergency shutdown events and spare probe consumption for end users.

• Gas Analysis and Emission Monitoring Equipment

  ✅Key Advantages

  1. Clean and Stable Capillary Path for Gas Sampling
  Alumina capillary tube provides a chemically inert and thermally stable channel for sample gas in analyzers and emission monitoring systems, limiting adsorption and drift over long operating periods.

  ✅ Problem Solved

  In flue gas analyzers, metallic or polymer capillary tubing can introduce adsorption or reaction with aggressive components, which increases calibration effort and causes signal drift. Using alumina ceramic capillary with a defined small inner diameter allowed one analyzer manufacturer to maintain stable flow rates and signal baselines over many months of field operation, reducing site recalibration frequency and warranty service costs across several installed systems.

• High-Voltage and Fiber-Optic Insulation

  ✅  Key Advantages

  1. Combined Mechanical Support and Electrical Insulation
  Small-ID alumina ceramic capillary supports and insulates thin wires or fibers in compact high-voltage assemblies and fiber-optic sensors, improving dielectric clearance within limited space.

  ✅  Problem Solved

  A producer of high-voltage measurement modules had recurring corona and partial discharge issues when using plastic and glass tubing in compact layouts. After redesigning the critical insulation paths around alumina ceramic capillary with appropriate wall thickness and creepage distance, the modules passed endurance testing at the required kilovolt level, and production returns linked to insulation failure dropped significantly over several production batches.

Alumina Ceramic Capillary Usage Instructions

• Installation

  1. Check the outer and inner diameters of the alumina ceramic capillary against your drawing before installation, and match bore count to the number of wires or legs used.
  2. Insert wires, thermocouple legs or fibers gently, avoiding sharp bends or sudden pushing that may chip the bore entry.
  3. For closed-end capillary designs, align the closed end toward the hot zone or probe tip as specified in the design.

• Operation

  1. Ensure that the alumina capillary tube is fully supported by the surrounding protection tube, metal sheath or fixture to reduce mechanical vibration and bending.
  2. Use the alumina ceramic capillary within the specified continuous temperature range and atmosphere; avoid rapid thermal shock beyond the design limit.
  3. For gas analysis applications, confirm that the capillary ID and length match the desired flow rate and response time.

• Storage

  1. Store alumina ceramic capillary in dry, clean shelves or drawers, keeping tubes separated to prevent mutual impact.
  2. Avoid stacking long and thin capillary tubes without support to prevent bending or accidental breakage.

• Cleaning

  1. For light contamination, blow the inner channel with clean compressed air or inert gas.
  2. For more demanding cleaning, use suitable solvent or deionized water and dry the alumina capillary completely at moderate temperature before reuse.
  3. Avoid strong mechanical tools inside the bore that can scratch or enlarge the ID.

• Common Misuse Points and Handling

  1. Issue: Cracks from Sudden Heating or CoolingCause: Alumina ceramic capillary exposed to direct flame or quenched in liquid without controlled ramp.
  Handling: Implement slower heating and cooling ramps; avoid immediate immersion or removal from very hot zones.

  2. Issue: Wire Insulation Failure at Entry Area

  Cause: Wires or thermocouple legs bending sharply at the capillary entrance or rubbing against unfinished edges.
  Handling: Use chamfered or deburred alumina capillary ends when possible and route wires with larger bend radius.

  3. Issue: Blocked Bore or Reduced Gas Flow

  Cause: Powder, oxides or sealant ingress during installation or operation.
  Handling: Inspect bore visually before use, keep the process side filtered, and clean or replace the capillary when pressure drop increases beyond design limits.

FAQ – Alumina Ceramic Capillary

1. Q: Where is alumina ceramic capillary used?
   A: An alumina ceramic capillary is a small-bore Al₂O₃ tube used to route and insulate wires, thermocouple legs, fibers or gases in high-temperature, high-voltage and chemically aggressive environments such as furnaces, analyzers and sensors.
2. Q: What is the typical working temperature of an alumina ceramic capillary?
   A: Depending on the alumina grade and design, an alumina ceramic capillary can usually be used up to around 1,600–1,700 °C in suitable atmospheres, as long as mechanical load and thermal cycling are within design limits.
3. Q: Which inner and outer diameters are available for alumina ceramic capillary tubes?
   A: Common dimensions include outer diameters from about 1 mm to 10–12 mm and inner diameters from around 0.2–0.3 mm up to several millimeters, with other sizes available on request for custom alumina ceramic capillary designs.
4. Q: Can I order multi-bore alumina ceramic capillary for multiple wires?
   A: Yes, alumina capillary tubes can be produced with single or multiple bores, allowing you to separate two, three or more conductors in one ceramic component while keeping each path insulated.
5. Q: How precise are the dimensions of alumina ceramic capillary tubes?
   A: For small-ID alumina ceramic capillary tubes, OD and ID tolerances can typically be controlled to around ±0.05–0.10 mm depending on size and length, with straightness and bore position specified in the drawing.
6. Q: Is alumina ceramic capillary compatible with corrosive gases or flue gas?
   A: High-purity alumina ceramic capillary has good chemical stability in many industrial gases and flue gases; suitability for specific media should be checked case by case, especially for strongly reducing or highly reactive atmospheres.

Alumina Ceramic Capillary Reviews

• ⭐️⭐️⭐️⭐️⭐️
  We have used alumina ceramic capillary tubes from ADCERAX in several thermocouple probe designs and the dimensional consistency helped reduce assembly time and scrap in our production line.
  -- David M., Purchasing Manager, HeatPro Furnace Systems
• ⭐️⭐️⭐️⭐️⭐️
  The engineering team at ADCERAX supported a custom multi-bore alumina ceramic capillary for our gas analysis module, and the parts met the specified ID and straightness needed for stable flow and signal response.
  -- Elena S., R&D Engineer, EnviroSense Analytics
• ⭐️⭐️⭐️⭐️⭐️
  ADCERAX as a factory supplier adjusted alumina capillary tube sizes and lot quantities to fit our project schedule, keeping sensor development on track without forcing us into oversized minimum orders.
  -- Kenji T., Technical Buyer, Nippon Process Controls
• ⭐️⭐️⭐️⭐️⭐️
  For our temperature sensor product line, alumina ceramic capillary from ADCERAX delivered the required high-temperature insulation with stable quality at a cost level that fits our long-term OEM program.
  -- Laura G., Product Manager, EuroTherm Sensors