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Thermocouple Engineering Data
Enviromental Limitations of Thermoelements

JP
For use in oxidizing, reducing, or inert atmospheres or in vacuum. Oxidizes rapidly above 540°C (1000°F). Will rust in moist atmospheres as in subzero applications. Stable to neutron radiation transmutation. Change in composition is only 0.5 percent (increase in manganese) in 20-year period.

JN, TN, EN
Suitable for use in oxidizing, reducing, and inert atmospheres or in vacuum. Should not be used unprotected in sulfurous atmospheres above 540°C (1000°F).

Composition changes under neutron radiation since copper content is converted to nickel and zinc. Nickel content increases 5 percent in 20-year period.

TP
Can be used in vacuum or in oxidizing, reducing or inert atmospheres. Oxidizes rapidly above 370°C (700°F). Preferred to Type JP element for subzero use because of its superior corrosion resistance in moist atmospheres.

Radiation transmutation causes significant changes in composition. Nickel and zinc grow into the material in amounts of 10 percent each in a 20-year period.

KP, EP
For use in oxidizing or inert atmospheres. Can be used in hydrogen or cracked ammonia atmospheres if dew point is below -40°C (-40°F). Do not use unprotected in sulfurous atmospheres above 540°C (1000°F).

Not recommended for service in vacuum at high temperatures except for short time periods because preferential vaporization of chromium will alter calibration. Large negative calibration shifts will occur if exposed to marginally oxidizing atmospheres in temperature range 815 to 1040°C (1500 to 1900°F).

Quite stable to radiation transmutation. Composition change is less than 1 percent in 20-year period.

KN
Can be used in oxidizing or inert atmospheres. Do not use unprotected in sulfurous atmospheres as intergranular corrosion will cause severe embrittlement.

Relatively stable to radiation transmutation. In 20-year period, iron content will increase approximately 2 percent. The manganese and cobalt contents will decrease slightly.

RP, SP, SN, RN, BP, BN
For use in oxidizing or inert atmospheres. Do not use unprotected in reducing atmospheres in the presence of easily reduced oxides, atmospheres containing metallic vapors such as lead or zinc, or those containing nonmetallic vapors such as arsenic, phosphorus, or sulfur. Do not insert directly into metallic protecting tubes. Not recommended for service in vacuum at high temperatures except for short time periods.

Type SN elements are relatively stable to radiation transmutation. Types BP, BN, RP and SP elements are unstable because of the rapid depletion of rhodium. Essentially, all the rhodium will be converted to palladium in a 10-year period.

NP, NN
Proprietary alloys suitable for use in applications cited for KP and KN.

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