DIN - AD 2000-MERKBLATT S 1
Simplified analysis for cyclic loading
| Organization: | DIN |
| Publication Date: | 1 February 2005 |
| Status: | active |
| Page Count: | 36 |
| ICS Code (Pressure vessels): | 23.020.30 |
scope:
The following rules on simplified analysis for cyclic loading1) apply to pressure-bearing parts of pressure vessels made of
- ferritic and austenitic rolled and forged steels,
- spheroidal graphite cast iron grades as specified in Annex 3
manufactured and tested according to the W and HP series of the AD 2000-Merkblätter.
The calculation only applies for components dimensioned on the basis of non-time-dependent design strength values (see 6.2 and 6.3 of AD 2000-Merkblatt B 0) and subjected to cyclic loads only in the form of pressure fluctuations. Additional cyclic loadings, for example loads due to rapid changes in temperature during operation or from external forces and moments, are to be assessed within the framework of the calculation according to AD 2000- Merkblatt S 2.
The analysis for cyclic loading shall only be considered a lifetime expectancy calculation to reasonably determine test and inspection intervals so that fatigue cracking which may occur can be detected in time.
The number of load cycles to be withstood may attain a multiple of the design load cycle number if the scatter band of the fatigue values is taken into account and in the case of boundary conditions for design, manufacture and loading that are more favourable than those on which design approval is based.
If the number of pressure fluctuations to be expected during operation exceeds the allowable number of load cycles calculated according to this AD 2000-Merkblatt, it is necessary to change the design or conduct a detailed calculation according to AD 2000-Merkblatt S 2 to satisfy the cyclic loading conditions.
This AD 2000-Merkblatt assumes that there are no influences from the fluid which may reduce the fatigue life (see clause 8).
A reduction in the permitted number of stress cycles is not required at low operating temperatures within the application limits of Stress Categories II and III in accordance with AD 2000-Merkblatt W 10.
1) The term "cyclic loading" is meant here in a comprehensive sense as the variation over time of a loading regardless of the magnitude and arithmetic sign of the mean value.
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