mechengineer
Mechanical
Hi Code experts,
Quote from UCS-66 (a),
"… … and attachments that are essential to the structural integrity of the vessel when welded to pressure-retaining components, shall be treated as separate components. Each component shall be evaluated for impact test requirements based on its individual material classification, governing thickness as defined in (1) and (2) below, and the minimum design metal temperature."
Point 1,
How to understand "attachments that are essential to the structural integrity of the vessel"? How to define the "essential" and "the structural integrity of the vessel"? Different people will have different view. If code does not clear give what the "essential" and "the structural integrity of the vessel" are, users will consider all pads weld on the vessel shall comply with the MDMT/impact test requirement of UCS-66, even if the rib, web, and base plates because whole saddle support is the "structural integrity of the vessel". I think at least that code may need to use more strictly words, such as "the pad/component directly weld to the vessel".
Point 2,
MDMT/impact test requirement has 3 basis points for pressure vessel design. 1, load/stress shall be a pressure load with primary membrane TENSILE stress. 2, The ratio of actual stress to the allowable stress. 3, Thickness of the component.
The isolation pads (shell and the support materials are different) for piping/platform support/lifting lug and the wear plate of saddle support do not meet the points 1 & 2 above. Thus, there is no way to use UCS-66 (b) to evaluate the reduction of MDMT due to the stress’s ratio for the isolation pads. How does code consider or give a solution on this point if the attachment pads shall be evaluated as per UCS-66?
Regards
Quote from UCS-66 (a),
"… … and attachments that are essential to the structural integrity of the vessel when welded to pressure-retaining components, shall be treated as separate components. Each component shall be evaluated for impact test requirements based on its individual material classification, governing thickness as defined in (1) and (2) below, and the minimum design metal temperature."
Point 1,
How to understand "attachments that are essential to the structural integrity of the vessel"? How to define the "essential" and "the structural integrity of the vessel"? Different people will have different view. If code does not clear give what the "essential" and "the structural integrity of the vessel" are, users will consider all pads weld on the vessel shall comply with the MDMT/impact test requirement of UCS-66, even if the rib, web, and base plates because whole saddle support is the "structural integrity of the vessel". I think at least that code may need to use more strictly words, such as "the pad/component directly weld to the vessel".
Point 2,
MDMT/impact test requirement has 3 basis points for pressure vessel design. 1, load/stress shall be a pressure load with primary membrane TENSILE stress. 2, The ratio of actual stress to the allowable stress. 3, Thickness of the component.
The isolation pads (shell and the support materials are different) for piping/platform support/lifting lug and the wear plate of saddle support do not meet the points 1 & 2 above. Thus, there is no way to use UCS-66 (b) to evaluate the reduction of MDMT due to the stress’s ratio for the isolation pads. How does code consider or give a solution on this point if the attachment pads shall be evaluated as per UCS-66?
Regards
