MgO Tube for Cartridge Heaters and Thermocouples — High-Temperature Electrical Insulation

Application for Magnesia Tubes

• Industrial Heating Equipment (Heaters / Furnaces)

  ✅Key Advantages

  1. Electrical insulation > 10¹⁴ Ω·cm @ RT prevents short circuits in cartridge heaters.
  2. Stable up to 1800 °C with FeCrAl or NiCr alloys.
  3. Low shrinkage (< 0.2 %) ensures dimensional consistency.

  ✅ Problem Solved

  A German industrial-heater manufacturer reported repeated heater failures caused by alumina tubes cracking under rapid heat cycles. After replacing them with ADCERAX MgO tubes, the failure rate dropped from 12 % to < 2 %, and service life extended from 8 months to over 14 months at 900 °C continuous operation. The MgO tubes maintained dielectric integrity even after 500 thermal cycles, enabling 24/7 furnace operation without unplanned maintenance shutdowns.

• Laboratory Thermal Systems (Furnace / Oven / Hot Zone Insulation)

  ✅Key Advantages

  1. Purity ≥ 99 % minimizes sample contamination.
  2. Withstands heating rate > 30 °C / min without cracking.
  3. Smooth bore improves gas flow and thermal uniformity.

  ✅ Problem Solved

  A U.S. university materials-testing lab encountered inconsistent TGA curves due to residual SiO₂ impurities in alumina liners. Switching to ADCERAX high-purity MgO tubes eliminated contamination peaks and stabilized mass-loss readings to within ± 0.1 %. The tubes sustained > 100 heating cycles at 1700 °C without dimensional drift, allowing repeatable calibration of instruments and extending furnace liner replacement intervals by 40 %.

• Sensor and Thermocouple Manufacturing

  ✅Key Advantages

  1. Dielectric strength ≥ 20 kV /mm for precise signal isolation.
  2. Excellent coaxiality for multi-bore alignment.
  3. Thermal expansion matching reduces lead stress.

  ✅ Problem Solved

  A Japanese temperature-sensor OEM previously faced 18 % reject rate in multi-bore thermocouple assemblies due to misaligned cores and cracks after brazing. ADCERAX supplied ± 0.05 mm-tolerance MgO tubes with controlled straightness < 0.2 mm per 500 mm length. The result was a zero-leak seal fit, no bore deformation after 1600 °C brazing, and a 35 % increase in final assembly yield. This improvement directly reduced production scrap cost and optimized sensor signal accuracy in field applications.

Mgo Tube Usage Instructions

• Installation

  1. Handle each MgO tube with clean cotton or nitrile gloves to prevent oil contamination that could lower surface insulation resistance.
  2. Align heating wires or thermocouple leads concentrically before insertion into outer metal sheaths to avoid mechanical stress.
  3. Seal both ends when operating in humid or oxidizing atmospheres using alumina cement or high-temperature sealant to block moisture ingress.
  4. Verify fit clearance (0.1–0.3 mm) between MgO tube and metal housing for thermal expansion compatibility.
  5. For multi-bore tubes, insert wires sequentially and rotate gently to prevent internal scratching or micro-cracking.

• Usage

  1. Recommended continuous working temperature: ≤ 1800 °C, short-term up to 1900 °C under neutral or reducing atmospheres.
  2. Avoid thermal shock exceeding 200 °C/s; a controlled heating ramp (≤ 5 °C/s) extends service life significantly.
  3. Use gradual cooling after shutdown to prevent tensile stress fractures caused by uneven temperature gradients.
  4. When used with electric heaters, ensure dielectric testing ≥ 10¹³ Ω·cm before installation.
  5. In laboratory furnaces, preheat slowly to 150–200 °C for 30 min to remove absorbed moisture before first use.

• Storage

  1. Keep stored MgO tubes in dry environments (< 60 % RH) and away from direct airflow or chemical vapours.
  2. Use silica gel or alumina desiccant packs to stabilize moisture content during long-term storage.
  3. Avoid exposure to acidic or chloride vapors, which may react with MgO to form hygroscopic MgCl₂.
  4. Store tubes horizontally with soft separators (foam or PE sheet) to prevent end chipping.

• Cleaning

  1. Remove surface dust with compressed dry air or nitrogen.
  2. If moisture absorption occurs, bake at 150–200 °C for 1 hour to fully dehydrate internal pores.
  3. Never immerse MgO tubes in water or chemical solvents; moisture will degrade dielectric strength.
  4. For laboratory reuse, gently wipe with alcohol on the outer surface only, then re-bake before reinstallation.
  5. Avoid mechanical cleaning tools or ultrasonic washing that can damage the sintered structure.

• Common User Issues & Solutions

  1.  Problem: Tube cracking after rapid temperature rise.
  Cause: Thermal expansion mismatch or abrupt ramp rate.
  Solution: Extend preheating stage; limit ramp to ≤ 5 °C/s and use insulation sleeves to balance gradients.

  2. Problem: Reduced insulation resistance after storage.
  Cause: Moisture absorption into open pores.
  Solution: Bake at 150 °C for 2 hours to restore resistance to > 10¹³ Ω·cm; seal ends with ceramic adhesive for long-term stability.

  3. Problem: Wire abrasion inside multi-bore tubes during assembly.
  Cause: Sharp edges or improper wire feeding.
  Solution: Chamfer tube edges to 0.3 mm R, use PTFE-coated lead wires or apply alumina lubricant paste during insertion.

  4. Problem: Surface powdering after repeated high-temperature cycles.
  Cause: Reaction with furnace gases or condensation of alkali vapours.
  Solution: Use high-purity (99.5 %) MgO grade and operate under neutral/inert atmosphere; perform surface inspection every 500 hours.

  5. Problem: Fit loosened after long-term service.
  Cause: Minor creep deformation under thermal stress.
  Solution: Use slightly undersized OD (–0.05 mm) at the design stage or switch to a reinforced wall (≥ 1.5 mm thickness).

Magnesium Oxide Tubes FAQ

1. Q: What is the main function of an MgO tube in heaters or thermocouples?
   A: An MgO tube serves as a high-temperature electrical insulator and heat conduit, isolating heater wires or thermocouple leads from the metal sheath. Its 99% magnesium oxide composition ensures dielectric strength above 10¹⁴ Ω·cm and stable thermal performance up to 1800 °C.
2. Q: How is an MgO ceramic insulating tube different from an alumina tube?
   A: MgO tubes provide higher maximum operating temperatures (≈ 1800–1900 °C) and better resistance to alkali vapors and molten metals, while alumina tubes offer slightly higher mechanical strength. For heater cores and sensor insulation, magnesia is often preferred for its superior electrical resistivity and thermal conductivity balance.
3. Q: What purity grades of magnesium oxide tubes are available?
   A: ADCERAX typically supplies 99 % and 99.5 % MgO grades. The high-purity version is used for analytical instruments or semiconductor heating systems where trace SiO₂ < 0.1 % and Fe₂O₃ < 0.05 % are critical to avoid contamination or dielectric drift.
4. Q: What are the standard and custom dimensions of MgO tubes?
   A: Standard inner diameters: 1–30 mm, lengths up to 1000 mm, wall thicknesses 0.5–3 mm.
   Custom machining allows ± 0.1 mm tolerance, multi-bore designs (2–8 holes), and special shapes like tapered or flanged ends.
5. Q: Can MgO tubes operate in oxidizing or humid environments?
   A: Yes, but the ends should be sealed with ceramic cement or a metal cap. Moisture ingress reduces insulation resistance. In oxidizing atmospheres above 1000 °C, MgO forms a thin protective MgO–Mg(OH)₂ layer that remains stable if humidity < 60 %.
6. Q: How should MgO tubes be stored for long-term use?
   A: Store below 60 % RH, ideally 20–25 °C. Use silica-gel packs and avoid chloride environments. Re-bake before use at 150 °C for 2 hours to remove absorbed moisture. Proper storage maintains insulation resistance > 10¹³ Ω·cm for over 12 months.

Magnesium Oxide Tubes Reviews

• ⭐️⭐️⭐️⭐️⭐️
  Our team purchased ADCERAX MgO ceramic tubes for custom cartridge heaters. Dimensional precision was within ± 0.1 mm, allowing direct assembly with no rework.
  --David K., Procurement Manager, ThermoHeat Systems (USA)
• ⭐️⭐️⭐️⭐️⭐️
  We used magnesium oxide tubes for thermal analysis furnaces. They remained stable at 1700 °C and no sample contamination occurred.
  -- Maria H., Lab Supervisor, UniLab Research (Germany)
• ⭐️⭐️⭐️⭐️⭐️
  ADCERAX multi-bore mgo ceramic insulating tubes helped us maintain tight alignment in miniature thermocouples. Delivery was on schedule and specs met ISO tolerance.
  -- R. Ito, Product Engineer,  Kyotronic Sensors (Japan)
• ⭐️⭐️⭐️⭐️⭐️
  As a China magnesium oxide ceramic tube supplier, ADCERAX offered consistent quality and responsive engineering support for custom designs.
  -- Ahmed S., Owner, Global Heat Tech (UAE)