Variable list
Different stress evaluation according to rules and regulations or WRC
The internal pressure creates high stresses at one edge of the opening. These are sometimes significantly higher than the allowable stress:
But these stresses are of a secondary nature, i.e. they limit themselves through the deformation of the material. Therefore, they are ignored in a pure internal pressure analysis.
However, if additional stresses are applied, for example by nozzle loads, these stresses can no longer be classified as secondary stresses, since they overlap with the primary stresses from the nozzle loads. Now you must no longer ignore these stresses!
These stresses must also not be ignored in fatigue considerations, since the material can deform plastically. This is taken into account by the corresponding factors in the fatigue calculations in addition to the weld seam influences.
They therefore have the following effect. You calculate a nozzle according to AD 2000, ASME or EN 13445 etc. This design is in order and permissible according to the respective regulations.
Now calculate the same nozzle according to WRC without nozzle loads.
Now the stresses can be clearly above 100%, since the stress evaluation changes.
This can best be seen in AD 2000 Merkblatt S3/6 Section 4.2.1:
AD 2000 S3/6 - 4.2.1 Stress due to compressive load
Individual stresses from internal or external compressive loads can be taken from e.g. [4] or [5]. If the application limits allow, [4] should be preferred. The curves given in [5] for the stress increase by compressive loading can be approximated according to [6] by the following equations:
The stress extended by the factor α from the global stress due to internal pressure (boiler equation) results in the total tension in the intersection area. It contains the global and also all local parts.
[4] Sicherheitstechnische Regel des Kerntechnischen Ausschusses: KTA 3211.2. Carl Heymanns Verlag KG, Köln, Berlin, 1993
[5] Bickell, M.B., and C. Ruiz: Pressure Vessel Design and Analysis. Macmillan and Co., London 1967
[6] Becker, M.: Berücksichtigung von Kräften und Momenten auf Behälterstutzen nach WRC 107 und WRC 297 und die Überlagerung mit Innendruck. RWTÜV e.V., Essen
Depending on the geometry, alpha is 2-10, i.e. the stresses at the opening are higher by this factor than in the undisturbed area.
Different stress evaluation according to rules and regulations or WRC
The internal pressure creates high stresses at one edge of the opening. These are sometimes significantly higher than the allowable stress:
But these stresses are of a secondary nature, i.e. they limit themselves through the deformation of the material. Therefore, they are ignored in a pure internal pressure analysis.
However, if additional stresses are applied, for example by nozzle loads, these stresses can no longer be classified as secondary stresses, since they overlap with the primary stresses from the nozzle loads. Now you must no longer ignore these stresses!
These stresses must also not be ignored in fatigue considerations, since the material can deform plastically. This is taken into account by the corresponding factors in the fatigue calculations in addition to the weld seam influences.
They therefore have the following effect. You calculate a nozzle according to AD 2000, ASME or EN 13445 etc. This design is in order and permissible according to the respective regulations.
Now calculate the same nozzle according to WRC without nozzle loads.
Now the stresses can be clearly above 100%, since the stress evaluation changes.
This can best be seen in AD 2000 Merkblatt S3/6 Section 4.2.1:
AD 2000 S3/6 - 4.2.1 Stress due to compressive load
Individual stresses from internal or external compressive loads can be taken from e.g. [4] or [5]. If the application limits allow, [4] should be preferred. The curves given in [5] for the stress increase by compressive loading can be approximated according to [6] by the following equations:
The stress extended by the factor α from the global stress due to internal pressure (boiler equation) results in the total tension in the intersection area. It contains the global and also all local parts.
[4] Sicherheitstechnische Regel des Kerntechnischen Ausschusses: KTA 3211.2. Carl Heymanns Verlag KG, Köln, Berlin, 1993
[5] Bickell, M.B., and C. Ruiz: Pressure Vessel Design and Analysis. Macmillan and Co., London 1967
[6] Becker, M.: Berücksichtigung von Kräften und Momenten auf Behälterstutzen nach WRC 107 und WRC 297 und die Überlagerung mit Innendruck. RWTÜV e.V., Essen
Depending on the geometry, alpha is 2-10, i.e. the stresses at the opening are higher by this factor than in the undisturbed area.