Explosion-proof thermocouple in petroleum and chemical industry enterprise is widely applied in automatic control system, through the temperature sensor to control the temperature of the object parameters into electrical signals, to the digital display, recorder or adjust instrument, testing, adjusting and controlling of system. 1, in order to make the measurement end of the thermocouple, and had good heat exchange between the measured medium, should choose the observation points, try to avoid the valve, elbow and pipe and equipment near the corner of the furnish 2 thermocouple, thermocouple with a protection casing with heat transfer and heat loss, in order to reduce the measurement error, thermocouple and thermocouple should have enough: (insert depth 1) For the measurement of pipeline fluid temperature thermocouple, generally should be measuring end is inserted into the pipe ( Vertical or inclined installation) , such as the current body of pipe diameter is 200 mm, the thermocouple insertion depth should choose 100 mm; ( 2) For high temperature and high pressure and high velocity of temperature measurement, Such as main steam temperature) , in order to reduce cases of fluid resistance and prevent cases break under the action of a fluid, can take protecting tube shallow inserted way or use hot thermocouple. Shallow inserted type thermocouple protection tube, its depth into the steam pipe should be no less than 75 mm; Heat sets the standard of thermocouple insertion depth is 100 mm; ( 3) If is need to measure the temperature of flue gas, although the flue is 4 m in diameter, thermocouple insertion depth of 1 m ( 4) When measuring the original insertion depth of more than 1 m, explosion-proof thermocouple shall be installed vertically, as far as possible or add racks and protect casing