EC Directive 97/23/EC NWEA Order no. 743/99 Order on the design of pressure equipment Harmonised standards: Incl.: EN 378 parts 1* to 4 EC Directive 97/23/EC Annex I Essential safety requirements 2.2.4 Design based on experimental       design method 2.2.3 Design based on calculation method Figure 5: Principle for order compliance