Head Straight Flange Thickness
Head Straight Flange Thickness
(OP)
In designing the same vessel using several different PV softwares a question has arose.
Compress is designing the head straight flange using the total design length. It is just a small piece and it is attached to the head. So, the head will provide support. If you consider the analogy of a cylinder under external pressure it would fail in the middle of the unsupported design length. This is the weakest point.
The straight flange length should be considered when analyzing the attached cylinder for vacuum condition.
The head is also checked for external pressure. The straight flange thickness is more than the thinner formed thickness of the head.
Can you clarify Codeware's interpretation or code reference that justifies the procedure you are implementing?
Thanks.
Compress is designing the head straight flange using the total design length. It is just a small piece and it is attached to the head. So, the head will provide support. If you consider the analogy of a cylinder under external pressure it would fail in the middle of the unsupported design length. This is the weakest point.
The straight flange length should be considered when analyzing the attached cylinder for vacuum condition.
The head is also checked for external pressure. The straight flange thickness is more than the thinner formed thickness of the head.
Can you clarify Codeware's interpretation or code reference that justifies the procedure you are implementing?
Thanks.
Brian





RE: Head Straight Flange Thickness
Unfortunately the Code does not seem to define "h" but they refer to the "bendline" in examples in Appendix L (Bednar text uses same term), which is the tangent line.
Consider this, what analysis would you perform on a vessel whose head had no straight flange (the vendor forgot it), a short 1.5" long cylindrical shell, and then several normal shell courses, then another shorty cylinder and misfabricated head. What is the difference if that shorty cylinder is separate or is integral with the formed head? Once it's all welded up there is no difference from the standpoint of structural response to external pressure.
"Although this forum is monitored by Codeware it is not intended as a venue for technical support and should not be used as the primary means of technical support."
Tom Barsh
Codeware Technical Support
www.codeware.com
RE: Head Straight Flange Thickness
Presumably "h" is the corresponding height on the inside surface.
"Although this forum is monitored by Codeware it is not intended as a venue for technical support and should not be used as the primary means of technical support."
Tom Barsh
Codeware Technical Support
www.codeware.com
RE: Head Straight Flange Thickness
Or if one can justify a "line of support" at a change in thickness (I imagine this would be difficult to do) then in COMPRESS one could specify a "pseudo-stiffener ring" to model that line of support.
"Although this forum is monitored by Codeware it is not intended as a venue for technical support and should not be used as the primary means of technical support."
Tom Barsh
Codeware Technical Support
www.codeware.com
RE: Head Straight Flange Thickness
"Although this forum is monitored by Codeware it is not intended as a venue for technical support and should not be used as the primary means of technical support."
Tom Barsh
Codeware Technical Support
www.codeware.com