Appendix 2 Flange - Pressure
Internal Pressure
Temperature: The maximum mean metal design temperature for the internal pressure case as defined in UG-20(a).
Corrosion Allowance: Corrosion allowance on the inside of the host component (convex side) for loose type flanges, inside of the hub (convex side) for integral type flanges, and inside of the thickness for reverse and blind flanges. This does not affect calculations for certain flange types (such as loose flanges).
Pressure: The internal design pressure (pressure on the concave side). This value is gauge pressure. When “Solve for Thickness” is selected, this value is an input and should not include static head. When “Solve for Pressure” is selected, this value is a result. In the latter case, it represents the total internal pressure (design pressure plus head) that the component can handle and meet code in the absence of any other loadings.
Static Head: The internal pressure (pressure on the concave side) resulting from the static head of the fluid. The user must determine this value and input it accordingly. It will be added to the Pressure input and the sum will be used in the internal pressure calculations for the component. This field will not be present when “Solve for Pressure” is selected.
Include Pass Partition Rib Area: Select this box if the flange should account for the gasket reaction from pass partition plates in shell and tube heat exchanger plates. This field is only available for flanges added to heat exchanger designs.
External Pressure
Ext. Pressure: The external design pressure (pressure on the convex side). This value is gauge pressure. The software will adjust this input for static head.
Ext. Temperature: The maximum mean metal design temperature for the external pressure case as defined in UG-20(a).
Ext. Static Head: The internal pressure (pressure on the concave side) resulting from the static head of the fluid that is present during the external pressure case. The user must determine this value and input it accordingly; it will be subtracted from the "Ext. Pressure" input.
Int. Pressure axial load: Fa is the axial load (if any) that is present on the flanged connection during the internal pressure case. This is not due to internal pressure. This value is positive if the load is pulling the connection apart and negative if it is pushing the connection together. For instance, in a vertical vessel with the bottom head bolted on, the value of Fa might be the weight of the bottom head and the weight of any fluid pushing down on the bottom head; in this case the load would be positive because it is pushing the connection apart. For a horizontal vessel with a bolted on head, Fa might be 0 in that case even though internal pressure exists.
Loads
Int. Pressure moment: M is the overturning moment (if any) that is present on the flanged connection during the pressure case indicated. This is not due to internal pressure. This value is never negative. For example, in a horizontal vessel with the right head bolted on, the value of Ma would be the force of the material and content weight to the right of the bolted connection times the distance to the center of gravity of that weight. For a vertical vessel with a bolted on head, M might be 0 even though internal pressure exists.
Ext. Pressure axial load: Fa is the axial load (if any) that is present on the flanged connection during the external pressure case. This is not due to external pressure. This is positive if the load is pulling the connection apart and negative if it is pushing them together. For instance, in a vertical vessel with the bottom head bolted on, the value of Fa might be the weight of the bottom head and the weight of any fluid pushing down on the bottom head; in this case the load would be positive because it is pushing the connection apart. For a horizontal vessel with a bolted on head, Fa might be 0 in that case even though external pressure exists.
Ext. Pressure moment: M is the overturning moment (if any) that is present on the flanged connection during the pressure case indicated. This is not due to internal pressure. This value is never negative. For example, in a horizontal vessel with the right head bolted on, the value of Ma would be the force of the material and content weight to the right of the bolted connection times the distance to the center of gravity of that weight. For a vertical vessel with a bolted on head, M might be 0 even though external pressure exists.
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