| 摘要 |
<p>PURPOSE: To prevent contamination of the inspection window of an inspection window mechanism by arranging a separate heater at the upper area in the heated area of a pipe body to which an inspection window joint is coupled for permanently heating the upper area to a higher temperature compared with the other parts of the heated area. CONSTITUTION: An inspection window mechanism 20 comprises a case 21 which is mounted on a cross adjacent part 14 and has an inspection window 22. The adjacent part 14 is provided, on its periphery partially on the side opposite to a joint pipe 23 coupled to the case 21, with a heating coil 25 laid which is adapted to be electrically heated up by a heat source 26 controlled by a controller 27. The controller 27 generates heat by means of the heating coil with the minimum power. The heating coil 25 heats up the space of a heating coil area as a measuring area to a higher temperature as compared with the other parts of the heating area. In such a way, a temperature gradient is caused over the upper and lower portions of the heated area to thereby prevent contaminant particles resulting from thermally decomposed products from moving into the measuring area and contaminating the inspection window mechanism 20 or inspection window 22, and fogs from being generated in the measuring area.</p> |
