Thermowell Materials

Carbon Steels :-

Low cost materials with little corrosion resistance. Used in low temperature and stress applications where the measured medium protects it from corrosion, oils, petroleum, tars etc. 
Maximum tenpertaure : 530 oC.

Chrome/Moly Steels :-

High strength steels used in pressure vessels and industrial boiler plant. Resistant to chloroform, cleaning agents, food products and carbon disulphide.
Maximum temperature : 600oC

304 Stainless Steel :-

Low cost corrosion resistant material, used extensively used in food, beverage and chemical processing where good corrosion resistance is required. A low carbon grade, 304L is available which can be welded without impairing it's corrosion resistance.
Maximum temperature: 900 oC.

321 Stainless Steel :-

Similar properties to 304SS above, except that this grade is titanium stabilized to prevent intergranular corrosion when welded.

316 Stainless Steel :-

Best corrosion resistance of the austenitic stainless steels due to the addition of molybdenum, widely used in chemical processing, offers useful resistance to H2 S. As with 304, a low carbon grade, 316L is available for welded applications. 
Maximum temperature: 900o C.

310 Stainless Steel :-

Heat resistant material, which can be used up to 1150 C with useful resistance in sulphur bearing atmospheres. Corrosion resistance is slightly better than 304SS, but not as good as 316SS. Can be welded with caution.

446 Stainless Steel :-

Ferritic stainless steel with excellent resistance to sulphurous atmospheres at high temperature, however due to its low strength at high temperature, thermowells made from this material should be mounted vertically. Used in heat treatment processes, iron and steel furnaces, gas production plant and it has some useful resistance to molten lead. Good corrosion resistance to nitric acid, sulphuric acid and most alkalis gives it some limited use in chemical plant. 

Maximum temperature: 1150 oC.

Inconel 600 :-

A very widely used nickel-chromium-ion alloy with excellent high temperature strength and oxidation resistance, however it is very vulnerable to attack in sulphurous atmospheres above 500 C. Good resistance to chloride-ion stress corrosion cracking and nitriding environments. Use extensively in chemical industries for its strength and corrosion resistance. Easily welded, can normally be used without post weld heat treatment. 
Maximum temperature: 1212 oC.

Inconel 625 :-

A nickel-chromium alloy with excellent resistance to pitting and crevice corrosion, unaffected by radiation embrittlement, widely used in aerospace applications and in marine environments. Good weldability, can be used in the as-welded condition. 

Maximum temperature: 1093 oC.

Incolloy 800 :-

Superior to alloy 600 in sulphur, cyanide salts and neutral salts. Extensively used in steam/hydrocarbon reforming plants for pigtail piping, manifolds and waste heat boilers and in the internal components of secondary reformers. Widely used in heat treatment equipment and as a heater sheath material. Maximum temperature: 1093 oC.

Incolloy 825 :-

A nickel-iron-chromium alloy with exceptional resistance to many corrosive environments, it is superior to almost all metallic materials for handling sulphuric acid and shows excellent resistance to phosphoric acid. It is widely used in chemical processing, oil and gas recovery, acid production, pickling operations, nuclear fuel reprocessing and handling of radioactive wastes. 
Maximum temperature: 540 oC.

Hastelloy C276 :-

Nickel-molybdenum-chromium alloy with excellent corrosion resistance, especially in chlorinated environments. Widely used in chemical plant where it tolerates ferric and cupric chlorides, solvents, chlorine, formic acid, acetic acid, brine, wet chlorine gas and hypochlorite. Can be easily welded and maintains its properties in the as-welded condition. 
Maximum temperature: 1093 oC.

Hastelloy B3 :-

A development of the well-established B2 alloy with improved thermal stability, fabricability and stress corrosion cracking resistance. It is the alloy of choice for handling hydrochloric acid in all concentrations and temperatures; it also withstands hydrogen chloride, sulphuric, acetic, hydrofluoric and phosphoric acids. Maximum temperature: 538 oC, up to 816 oC in reducing or vacuum environment.

Hastelloy C22 :-

A nickel-chromium-molybdenum-tungsten alloy with outstanding resistance to pitting, crevice corrosion and stress corrosion cracking. It shows exceptional resistance to a wide range of chemical process environments, such as ferric and cupric chlorides, chlorine, hot contaminated solutions, formic and acetic acids and seawater or brine solutions. The material has superior weldability, and retains its properties in the as-welded state. chlorine gas. Its good resistance to seawater and salt spray, allows it to be used in off-shore installations. Can be welded with special precautions to protect from atmospheric contamination.

Hastelloy X :-

A high temperature alloy with excellent resistance to oxidizing, reducing and neutral atmospheric conditions, widely used in aircraft jet engine components. Very good high temperature strength makes it ideal for furnace applications. Resistant to stress corrosion cracking in petrochemical applications. Maximum Temperature: 1204 oC.

Titanium :-

A lightweight material with good strength in the 150 to 470 C range. Excellent resistance to oxidizing acids such as nitric or chromic, it is also resistant to inorganic chloride solutions, chlorinated organic compounds and moist chlorine gas. Its good resistance to seawater and salt spray, allows it to be used in off-shore installations. Can be welded with special precautions to protect from atmospheric contamination.

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