| 摘要 |
A pipe elbow has an access opening provided with a marginal frame which is undercut to seat the elbow wall and is recessed to receive a closure plate so that the bottom surface of the closure plate and the frame are flush with the inner surface of the elbow wall in a smooth continuity. A flange on the upper surface of the closure plate inside the recess supportingly abuts a gasket which seals against the top wall of the recess when the closure plate is held in position by external clamping means. The supporting abutment of the flange with the gasket is directly opposite to the line of force of any fluid entering the recess from the interior of the elbow.
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