1. When the nominal diameter of high temperature and high pressure steam pipeline is equal to or less than 250 mm, the inserting depth should be 70 mm; When the nominal diameter of that is greater than 250 mm, the inserting depth should be 100 mm. 

2. When the outer diameter of the general fluid medium pipeline is equal to or less than 500 mm, the inserting depth should be 1/2 of the outer diameter of the pipeline; When the outer diameter is greater than 500 mm, the inserting depth should be 300 mm. 

3. As for the pipeline with medium of fume, air and mixture of air and dust, the inserting depth should be 3/2 of the outer diameter of the pipeline. 

4. The measuring end of the measuring element on the return pipeline must be immersed into the measured medium completely.