In many cases, springback is more of an issue than cracking and necking when forming high strength steels because it is very difficult to predict springback. While all steels experience some degree of springback, the phenomenon is most severe in high strengths steels. The riser will have a transition piece at this location to mirror the platform batter. Above the waterline (typically 10–15 ft), the platform supports change from battered to vertical. Typically, this aspect of geometry must be checked carefully, particularly when the jacket has different batters for different faces. If the pipe approaches parallel to the face, the bend will be 90°. For example, if the platform batter is 1:12, or 85.24°, and the pipe approaches normal to the jacket face, the riser bend will subtend an arc of 85.24°. The angle of the bend must be such that the riser follows the platform batter in the plane of the riser and pipeline. pipe designed with a 3D radius will have a radius to centerline of 54 in. The MBR depends on diameter and wall thickness, but is generally 3 to 5 times the pipe diameter. For typical inspection pigs of diameters larger than 4 in., a minimum bend radius (MBR) is required. The elbow at the base of the riser is normally designed for inspection pigging. Tian Ran Lin, in Offshore Pipelines (Second Edition), 2014 7.8 Riser Bends
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