Hi
I've been trying to rationalise applying the Kellog method to trunnions on elbows [duckfoot, base elbow or whatever you call them]. Obviously a trunnion attached to a stright piece of pipe, must behave differently to one on a curved piece of pipe i.e. and elbow.
I have been trying a method based on the local load calculations fron BS EN 13445 [Pressure Vessels] considering the circumferential loads as acting on a shell with diameter equal to the pipe OD and the longitudinal loads acting on a semispherical head of crown radius equal to the centerline radiius of the elbow plus half the OD of the pipe. Axial loads are included in both cases. The method calculates a bending stress limit in each direction and then calculated maximum allowable forces and moments from there which can be compared via a unity check against your applied loads.
So far the results seem more conservative than applying the Kellogg method to the elbow as if it were a straight piece of pipe. [I generally factor calculated stresses by a SIF of 2.1 as an attempt to include what is happening to the elbow itself in the calculation].
Does anybody else have anything to say about calculating trunnion loadings on elbows as opposed to striaght pipe?