Sensor tubes (also known as thermocouple protection tubes) are primarily used to provide protection for thermocouples from corrosive and abrasive atmospheres present in industrial processes. Hexoloy® alpha silicon carbide (Hexoloy) is a single-phase silicon carbide product that is extremely pure and uniform. Silicon carbide has been mass produced since 1893 because of its hardness, but purity and porosity have always been limiting factors. Saint-Gobain Performance Ceramics & Refractories has been a major contributor to the Silicon Carbide thermocouple protection tube industry for over 30 years. Improvements in the sintering process have led to unprecedented levels of purity, which have improved upon the material’s performance. In the harshest, most corrosive and abrasive environments, Hexoloy SiC will outperform traditional commercially available ceramics and metal alloys.
Hexoloy SiC is produced by pressure-less sintering of submicron silicon carbide powder in a proprietary extruding process. The sintering process results in a self-bonded, fine grained (less than 10 μm) SiC product. Densities of fired parts are consistently in excess of 95 percent of the theoretical density of silicon carbide (3.21 g/cm3). Extremely hard and lightweight, Hexoloy silicon carbide has a high resistance to corrosion, high temperatures and thermal shock while also having a high thermal conductivity. This makes Hexoloy an ideal material for temperature sensor tubes in a variety of traditionally challenging environments such as incinerators, chemical processing and furnaces.
Due to its high density, low porosity and chemical purity, Hexoloy SiC has universal corrosion resistance, meaning that it is suitable for almost all chemically corrosive environments. It has superior oxidation resistance due to a silicon dioxide film that forms after sintering. It can be used in the presence of hot liquids or gases, strong acids, bases or oxidizers. Since it is made without binders, Hexoloy thermocouple protection tubes will not contaminate process media making it suitable for high purity processing applications.
A high thermal conductivity, five times that of alumina, means that small temperature changes can be accurately captured with high sensing speed and no hysteresis. Hexoloy SiC also has a low coefficient of thermal expansion enabling its use in extremely high temperatures up to 1,950º C (dependent on application). It can withstand sudden temperature changes with a resistance to thermal shock more effectively than tungsten carbide, aluminum oxide and Reaction Bonded silicon nitride. In general, these thermal properties make Hexoloy a promising alternative to ductile metals in high temperature applications.
In addition to its excellent chemical and thermal properties, Hexoloy SiC has exceptional hardness of 2,800 kg/mm2. This makes it 50 percent harder than tungsten carbide. With a specified wear rate (pin on disc) of SiC versus SiC 1x10-9 mm2/kg, coefficient of friction (pin on disc) SiC versus SiC 0.2, Hexoloy material is excellent for applications involving high abrasion or sliding wear. Even at temperatures as high as 1,650º C in air, or up to 1,950º C in argon/nitrogen, Hexoloy SiC can withstand abrasion, making it ideal for waste incinerators, gas, oil, coal or biomass fired chambers. Yet, Hexoloy SiC is also light, weighing 40 percent as much as steel and about the same as aluminum.
|Custom Length-L (+1/8")||OD||ID||Tolerance|
|6" - 27"||3/8"||1/4"||± 0.015|
|>27" - 54"||3/8"||1/4"||± 0.015|