Someone helpme, we should to make elbow in 36", but we dont have bending diameter for that, i can make mitred elbows , we are manufacturing under b31.11
B31.11 is superseded/withdrawn and currently falls under B31.4 scope.
Are you sure your design should be acc. B31.11? If so, refer to paragraphs 1134.7.2 and 1106.2.2 for more info on fabrication and limitations of mitered bends for B31.11 applications.