Considered Local thickness of shell at trunnion pipe OD in WRC
Considered Local thickness of shell at trunnion pipe OD in WRC
(OP)
Dear's,
The trunnion sketch as shown in the trunnion calculation page depicts the tunnion pipe is directly connected to the shell and in the WRC calculation the local thickness at the pipe OD (RM/t)is considered as repad+shell thickness.
My query is shall the trunnion pipe be directly welded to the shell or shall it be welded on the repad. In contrast PVelite uses a different approach. It does not considers the pad thickness in the WRC calculation and shows the sketch in the same way as compress ie the trunnion pipe is directly connected to the shell.
Could someone please provide some clarification on which approach to follow. Till today we have been welding the trunnion pipe on the repad and not directly to shell.
Thanks in advance to all the members who provide their valuable view on the subject matter.
The trunnion sketch as shown in the trunnion calculation page depicts the tunnion pipe is directly connected to the shell and in the WRC calculation the local thickness at the pipe OD (RM/t)is considered as repad+shell thickness.
My query is shall the trunnion pipe be directly welded to the shell or shall it be welded on the repad. In contrast PVelite uses a different approach. It does not considers the pad thickness in the WRC calculation and shows the sketch in the same way as compress ie the trunnion pipe is directly connected to the shell.
Could someone please provide some clarification on which approach to follow. Till today we have been welding the trunnion pipe on the repad and not directly to shell.
Thanks in advance to all the members who provide their valuable view on the subject matter.
RE: Considered Local thickness of shell at trunnion pipe OD in WRC
RE: Considered Local thickness of shell at trunnion pipe OD in WRC
COMPRESS does both!
COMPRESS checks the stresses in the shell at two locations. Each location is checked using the WRC bulletin 107. The bulletin determines stresses in the shell at the outside radius ("rO") of the circular attachment.
This method is consistent with what I have seen done in industry generally, using non-COMPRESS methods (hand calculations, in-house fortran programs, etc.). Which is not to say that everyone in industry has done it this way.
Edited to add: Remember, COMPRESS assumes that the trunnion barrel is directly welded to the shell.
RE: Considered Local thickness of shell at trunnion pipe OD in WRC
There is a wealth of discussion regarding design of trunnions and reinforcing pads on eng-tips if you use the "search" function. It seems there is no consensus on whether the reinforcing pad should be a "donut" ("bagel"?) or a "pita". But certainly if the pad is a "pita" then it must be fully designed for the lifting loads that must be transferred through it (and how is this done without FEA?).
RE: Considered Local thickness of shell at trunnion pipe OD in WRC
Welding the trunnion onto the reinforcement only gives you the reinforcement thickness to use in WRC calculation and this way of the calculation is not reliable, however using the reinforcement thickness only is conservative in compression loads only. Tension and/or bending stresses on shell are greatly underestimated if you use the total thickness in the calculation without welding the trunnion on shell.
Hope it helps.
RE: Considered Local thickness of shell at trunnion pipe OD in WRC