| 摘要 |
A protection assembly comprises two identical rings (10), each having its upper edge (13) shaped to engage with the lower edge (12) of a ring stacked on top of it or to match the under surface (22) of a lid (20). The rings and lid have projections (11, 14, 21) for handling equipment, in opposite pairs on the rings and peripheral on the lid. Each of the rings is made from concentric cylinders (15, 16) of 2 cm steel and filled with preferably barite concrete containing an intermediate thin steel reinforcing cylinder (17).
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