Alumina Crucibles & Thermocouple Tubes
Alumina crucibles and closed-end protection tubes in 99% and 99.7% grades for melting, sampling and temperature measurement up to 1,700 °C.
Crucibles and sheaths fail from thermal shock and chemistry far more often than from temperature. Specifying them well means knowing the heating rate and the melt, not just the peak temperature.
Where it is used
- Metal melting, sampling and analysis crucibles
- Thermocouple and RTD protection sheaths in furnaces and kilns
- Laboratory and pilot-scale high-temperature processing
- Glass and frit melting and sampling
- Catalyst and powder calcination
- Sample boats and combustion ware
Sizes and formats
| Format | Range | Grade |
|---|---|---|
| Crucible, low form | 10 – 1,000 ml | AL-99 / 99.7 |
| Crucible, tall form | 20 – 5,000 ml | AL-99 / 99.7 |
| Crucible with lid | to match | AL-99 / 99.7 |
| Thermocouple tube, closed end | Ø6 – 40 mm, length to 1,500 mm | AL-99 / 99.7 |
| Tube, open both ends | Ø6 – 80 mm | AL-99 / 99.7 |
| Stepped or flanged tube | to drawing | AL-99.7 |
| Sample boat / combustion ware | to drawing | AL-99.7 |
Wall thickness is chosen for the thermal cycle, not only for mechanical strength. A thin wall resists shock better; a thick wall resists load and chemical attack longer.
The thermal cycle is the specification
Two applications at the same peak temperature can have completely different outcomes. A crucible held at 1,500 °C for eight hours survives; the same crucible plunged into water at 1,500 °C fails immediately. Send us the ramp rate, the dwell, the cooling rate and the number of cycles expected, and we will specify the wall thickness and grade around the cycle.
Chemical compatibility
- Suitable for most mineral and organic acids, neutral salts, and steam
- Suitable for molten metals that do not reduce alumina
- Not suitable for hydrofluoric acid or hot concentrated phosphoric acid
- Not suitable for strong alkalis above about 100 °C
- Tell us the melt or the process chemistry and we will confirm before quoting
Tell us the cycle, not just the temperature
Ramp rate, dwell, cooling and the chemistry involved. We will confirm grade, wall thickness and expected life.
Send us your drawing — get a quotation with a firm lead time
PDF, DWG, STEP, IGES or a photo with the critical dimensions marked. Engineering review within one working day.