Protective tubes are used to mechanically and chemically protect thermocouples or resistance thermometer from direct contact with the object being measured or the atmosphere. The following items should be considered as selection criteria for protective tubes. (They are broadly divided into two types:
metallic protective tubes and
non-metallic protective tubes.)
- Must be able to withstand the measurement temperature and pressure.
- Must be resistant to the corrosiveness of the object being measured and the atmosphere.
- High airtightness.
- Withstands thermal shock.
- Resistant to mechanical shocks such as vibration and shock.
- The protective tube itself must not emit any gases that are harmful to the temperature measuring section.
- There is little time delay and fast response.
Metal Protective Tube
| Material | Normal temperature | Maximum temperature | characteristic |
| SUS304 | 900℃ | 1000℃ | 18% chromium, 8% nickel steel. Excellent corrosion and heat resistance. Weak against sulfur and reducing gases. |
| SUS316 |
900℃ |
1000℃ |
Contains molybdenum and has excellent heat, acid and alkali resistance. Better corrosion resistance than SUS304. |
| SUS310S |
1000℃ |
1150℃ |
It has a high nickel and chromium constituent and has excellent heat resistance. It is vulnerable to high-temperature and high-concentration gases that contain sulfur. |
NCF600
(Inconel 600) |
1050℃ |
1150℃ |
Nickel alloy with heat resistance equivalent to SUS310S. Relatively suitable for zinc and city gas, but vulnerable to sulfur. |
SUH446
(Sandvik P4) |
1000℃ |
1200℃ |
Ferritic Cr steel. Excellent heat and corrosion resistance, and resistant to sulfur and reducing gases. |
| Kanthal |
1100℃ |
1350℃ |
High mechanical strength at high temperatures. Resistant to oxidizing atmospheres, sulfide gases and carbon gases. Cr22, Al 5.3%, remaining Fe. |
| titanium |
250℃ |
500℃ |
Its chemical corrosion resistance is superior to that of SUS304. It becomes brittle at high temperatures. |
| SUS316L |
900℃ |
1000℃ |
A steel with a reduced carbon content compared to SUS316. It is a material resistant to intergranular corrosion. |
| Hastelloy C |
1000℃ |
1100℃ |
Excellent resistance to ferric chloride, cupric chloride, and chlorine gas. |
| Teflon Coating |
200℃ |
250℃ |
SUS304 coated with FEP resin. High resistance to chemicals at low temperatures. Maximum length is 2m. |
| KTA-KU50 |
1150℃ |
1200℃ |
Cobalt-based alloy. Excellent heat and wear resistance. Resistant to sulfur gas, vanadium, etc. |
Non-metallic protective tube
| Material | Normal temperature | Maximum temperature | characteristic |
| Hard Vinyl | 60℃ | 100℃ | For low temperatures (but not below -10°C). Suitable for corrosive liquids. |
| Quartz glass |
1000℃ |
1050℃ |
It has a small thermal expansion coefficient and heat capacity, making it resistant to thermal shock. It is weak against alkalis and resistant to acids. It is permeable to hydrogen and reducing gases. |
| At most alumina (PT1) |
1500℃ |
1550℃ |
High airtightness. Resistant to molten metal and combustion gas. Weak against metal oxides and alkali. |
| Pure sintered alumina (PT0) |
1600℃ |
1900℃ |
Resistant to molten metal, glass, and lead slag. Highly airtight. Weak against thermal shock. |
| Silicon carbide |
1400℃ |
1700℃ |
Resistant to thermal shock. Not airtight. Becomes a conductor of electricity at high temperatures. |
| Silicon nitride |
1200℃ |
1600℃ |
Resistant to acids and acid salts, resistant to thermal shock, weak to mechanical shock, and resistant to melting of non-ferrous metals. |
| Teflon Tube |
200℃ |
250℃ |
High resistance to chemicals at low temperatures. (FEP resin) Also available with flange. |
*Please refer to the catalog for other specifications.
