Selection and installation of thermocouple and thermal resistance points1

A, thermocouple and thermal resistance selection:

1, the normal temperature range of the measured object selection of under 300 ℃ heat resistance

2, the normal temperature range of the measured object in the selection of more than 300 ℃ thermocouple

2, installation and maintenance of the thermocouple and thermal resistance practice

1, to grasp the method of the installation of the thermocouple and thermal resistance;

2, learn how to use the thermocouple, heat resistance temperature measurement;

3, thermocouple, heat resistance and secondary instrument connection

3, thermocouple and thermal resistance of the installation requirements

installation of thermal resistance and thermocouple, thermocouple installation should be paid attention to the use of some of the details; For temperature measurement accurate, safe and reliable and convenient maintenance, and shall not affect the equipment operation and production operation should meet the following requirements, in the choice of thermocouple and thermal resistance of the installation site and insertion depth to pay attention to the following 2 points

1, with a protection casing thermocouple and thermal resistance of heat transfer and heat loss, in order to reduce the measurement error, insertion depth of thermocouple and thermal resistance should have enough

( 1) When measuring the original insertion depth of more than 1 m, shall be installed vertically, as far as possible or add racks and protect casing

( 2) If is need to measure the temperature of flue gas, although the flue diameter of 1000 mm, the thermocouple or heat resistance insertion depth 500 mm

( 3) For thermocouple temperature center fluid, usually should be measuring end is inserted into the pipe center ( Vertical or inclined installation) As the current body of pipe diameter is 100 mm, the thermocouple or heat resistance insertion depth should choose 50 ~ 100 mm ( Should take into account the installed base or flange size) ;

( 4) For high temperature and high pressure and high velocity of temperature measurement, Such as main steam temperature) , in order to reduce the protection to protect fluid resistance and prevent casing pipe break under the action of a fluid, can adopt the mode of protection tube shallow inserted or use hot set of 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;

2、为了使热电偶和热电阻的测量端与被测介质之间有充分的热交换,应选择合理测点位置,尽量避免在阀门,弯头及管道和设备的死角附近装设热电偶或热电阻

四、热电偶与热电阻的安装方法

1、首先应测量好热电偶和热电阻法兰或者螺纹螺牙的尺寸,加工配套好法兰或者螺纹底座

2、要根据法兰或者螺纹底座的尺寸,在需要测量的管道上开孔

3、法兰或者螺牙座的焊接把法兰座或者螺纹底座插入已开好孔内,把法兰座或者螺纹底座与被测量的管道焊接好

4、把热电偶或热电阻用螺栓紧固或者螺纹旋进已焊接好的螺纹底座

5、按照接线图将热电偶或热电阻的接线盒接好线,并与表盘上相对应的显示仪表连接注意接线盒不可与被测介质管道的管壁相接触,保证接线盒内的温度不超过100℃范围接线盒的出线孔应防因密封不良,水汽灰尘等沉积造成接线端子短路

6、热电偶或热电阻安装的位置,应考虑检修和维护方便

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key words: thermal resistance, thermocouple, thermal resistance, platinum resistance, PT100, PT1000, pressure sensor and digital temperature sensor