| 摘要 |
PROBLEM TO BE SOLVED: To facilitate a presence or non-presence of residual oil within a tank truck to be easily checked in which a seep into an inner central hole is taken through an inner seeing pipe passage of a tank truck unloading passage member and then the presence or non-presence of the residual oil at a central hole can be checked. SOLUTION: An inner seeing pipe passage member 21 is provided with a transparent annular member 50 acting as a main body. The transparent annular member 50 has at an opposite outer circumference of the seeing section a white or silver reflecting layer 53 colored with white or silver coating and the like. When an inside part of the central hole 52 is seen from a seeing side of the transparent annular member 50, the white or silver reflecting layer 53 becomes a background or the central hole 52, resulting in that the presence or non- presence of the residual oil within the central hole 52 can be checked.
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