WRC 107 Stress Calculations - PV Elite - Help

WRC 107 Stress Calculations - PV Elite - Help - Hexagon

CodeCalc Help

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The software calculates stress intensities according to WRC 107 and includes the effects of longitudinal and hoop stresses due to internal pressure. If the geometry includes a reinforcing pad, CodeCalc performs two analyzes on the geometry. The first analysis calculates stresses at the edge of the nozzle. The second stress analysis is at the edge of the reinforcing pad.

CodeCalc uses the Lamé equation to determine the exact hoop stress at the upper and lower surface of the cylinder around the edge of the attachment. The hoop stress equations, as well as the longitudinal stress equation are as follows:

For spherical shells the program uses the following equation:

For each run performed, a table of dimensionless stress factors for each loading is displayed for review. Any table figure followed by an exclamation point (!) means that the curve figure for that loading has been exceeded.

Why are the stresses at Edge of the Pad the same as at Edge of the Nozzle?

Because the stress is a direct product of the stress factor, the stresses calculated at the edge of the pad may be same as those at the edge of the nozzle if the curve parameter for that type of stress has been exceeded.

What are the Allowable Stresses?

The stress intensities calculated should typically be between 1.5 and 3.0 times the hot allowable stress for the vessel material at operating temperature. If the results are less than 1.5 Sa then the configuration and loading are acceptable. If the load is self-relieving — that is, if it relaxes or disappears after only a small rotation or translation of the attachment — the allowable stress intensity increases to 3.0 Sa. Since many geometries do not fall within the acceptable range of WRC 107, it may be necessary to use a more sophisticated tool to solve the problems where the diameter of the vessel is very large in comparison with the nozzle, or where the thickness of the vessel or nozzle is small. An example of a more sophisticated tool would be Finite Element Analysis (FEA).


Figure C - WRC 107 Module Geometry for a Sphere	Figure D - WRC 107 Axis Convention for a Cylinder

Spherical Shells	Cylindrical Shells
To Define WRC Axes: P-axis: Along the nozzle centerline and positive entering the vessel. M1-axis: Perpendicular to the nozzle centerline along convenient global axis. M2-axis: Cross the P-axis into the M1 axis and the result is the M2-axis.	To Define WRC Axes: P-axis: Along the nozzle centerline and positive entering the vessel. MC-axis: Along the vessel centerline and positive to correspond with any parallel global axis. M2-axis: Cross the P-axis with the MC axis and the result is the ML-axis.
To Define WRC Stress Points: u: Upper, means stress on outside of vessel wall at junction. l: Lower, means stress on inside of vessel at junction. A: Position on vessel at junction, along negative M1 axis. B: Position on vessel at junction, along positive M2 axis. C: Position on vessel at junction, along positive M2 axis. D: Position on vessel at junction, along negative M2 axis.	To Define WRC Stress Points: u: Upper, means stress on outside of vessel wall at junction. l: Lower, means stress on inside of vessel at junction. A: Position on vessel at junction, along negative MC axis. B: Position on vessel at junction, along positive MC axis. C: Position on vessel at junction, along positive ML axis. D: Position on vessel at junction, along negative ML axis. Shear axis VC is parallel, and in the same direction as the bending axis ML. Shear axis VL is parallel, and in the opposite direction as the bending axis MC.

Spherical Shells

Cylindrical Shells

To Define WRC Axes:

P-axis: Along the nozzle centerline and positive entering the vessel.
M1-axis: Perpendicular to the nozzle centerline along convenient global axis.
M2-axis: Cross the P-axis into the M1 axis and the result is the M2-axis.

To Define WRC Axes:

P-axis: Along the nozzle centerline and positive entering the vessel.
MC-axis: Along the vessel centerline and positive to correspond with any parallel global axis.
M2-axis: Cross the P-axis with the MC axis and the result is the ML-axis.

To Define WRC Stress Points:

u: Upper, means stress on outside of vessel wall at junction.
l: Lower, means stress on inside of vessel at junction.
A: Position on vessel at junction, along negative M1 axis.
B: Position on vessel at junction, along positive M2 axis.
C: Position on vessel at junction, along positive M2 axis.
D: Position on vessel at junction, along negative M2 axis.

To Define WRC Stress Points:

u: Upper, means stress on outside of vessel wall at junction.
l: Lower, means stress on inside of vessel at junction.
A: Position on vessel at junction, along negative MC axis.
B: Position on vessel at junction, along positive MC axis.
C: Position on vessel at junction, along positive ML axis.
D: Position on vessel at junction, along negative ML axis.

Shear axis VC is parallel, and in the same direction as the bending axis ML. Shear axis VL is parallel, and in the opposite direction as the bending axis MC.