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Sheath Materials

What sheath material is thebest for my application?

DescriptionSheath Material

In mild corrosive environments andgeneral purpose applications, 304 SS and 316 SS are usually thebest choice when considering cost versus performance. Choose Alloy 600 over 304 SS or 316 SS when temperatures exceed 899°C (1650°F).When using acids at temperaturesbelow 250°C (482°F) PFA coatingsshould be used.Use the chart provided as a quickreference for determining the bestsheath material for your applicationor consult a corrosion guide for the best choice based on yourenvironmental conditions.

304 SSMaximum temperature: 899°C (1650°F). 304 SS suitsMost widely used low temperature sheath most applicationsmaterial. Extensively used in food, beverage, and is readily chemical and other industries where corrosion available. resistance is required. Subject to damaging carbide precipitation in 482-871°C(900-1600°F) range. Lowest cost corrosion resistant sheath material available.316 SSMaximum temperature: 899°C (1650°F). Best 316 SS has morecorrosion resistance of the austenitic stainless nickel than 304 SS steel grades. Good corrosion resistance in H
2 S. and is used forWidely used in the food and chemical industry. food applications. Subject to damaging carbide precipitation in 482-871°C (900-1600°F) range.Alloy 600Maximum temperature: 1176°C (2150°F). Alloy 600 has theMost widely used thermocouple sheath most nickel andmaterial. Good high temperature strength, the highest temp- corrosion resistance, resistance to chloride ion erature rating. stress corrosion cracking and oxidationresistance to high temperatures. Do not use insulfur bearing environments. Good in nitriding environments.310 SSMaximum temperature: 1150°C (2100°F). 310 SS has aMechanical and corrosion resistance, similar to higher temperature but better than 304 SS. Very good heat resist-than 304 SS orance. This alloy contains 25 percent Cr, 316 SS but is not20 percent Ni. Not as ductile as 304 SS.very common.PFA over Maximum temperature: 250°C (482°F) PFA over 304 SS304 SScontinuous. Thermocouple sheath O.D. is works well in mostCoating*encapsulated in a black PFA, allowing the acid environments.thermocouple to be used in applications Strong bases canwhere corrosive fluids and gases, strong corrode PFA.mineral, oxidizing and organic acids and alkalies are present. Examples: food andbeverage, pharmaceutical, labs,electroplating, semiconductor processing.Nominal wall thickness of the PFA is 0.010 inch.

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