Mechanical design fundamentals (1/13)
97/23/EC - European Pressure Equipment Directive
Applications
All equipment that is pressurized to more than 0,5 Bar above atmospheric pressure must be assessed in accordance with the European Pressure Equipment Directive 97/23/EC and if necessary designed and manufactured in accordance with the requirements contained within the Directive.
This equipment can be vessels for storage or pressurization of fluids, heat exchanger equipment, pipe work, safety accessories, pressure accessories or assemblies.
From May 2002 the Directive MUST be applied to all equipment defined in the Directive that is to be sold and installed within the European Community. If categorized I, II, III or IV the equipment MUST be CE marked.
From May 2002, if equipment that should be manufactured within the regulations contained in the Directive is not assessed correctly or is not manufactured within the specified requirements, a Government appointed authority can force the manufacturer of the equipment to withdraw it from use and in extreme cases could force the manufacturer to stop manufacturing equipment of this type.
It is essential therefore that everyone involved with the design, sales and manufacturing of equipment that is affected by the new regulations are aware of the procedures needed for assessment of the equipment and the effects of the Directive on the design and manufacturing processes.
Assessment of requirements
The assessment is carried out in four stages.
Stage 1: For vessels
An assessment of the fluid contained within the system must be carried out. If a fluid is explosive, flammable, toxic or oxidizing it is classified as dangerous and is classified as a Group 1 fluid. All other fluids are classified as Group 2 fluids. We have a published list of fluid categorizations available to us. The fluid must be categorized as a gas or liquid:
- If the fluid is a gas or vapor or if it is a liquid whose vapor pressure at the maximum allowable temperature is greater than 0,5 Barg it is categorized as a gas.
- If the fluid is a liquid whose vapor pressure at the maximum allowable temperature is less than 0,5 Barg it is categorized as a liquid.
- The volume of fluid contained within the equipment must be calculated.
- The product of the vessel volume multiplied by the design pressure for the vessel must be calculated.
These four factors allow a classification of the vessel in accordance with Article 3 of the Directive which refers to a graph in Annex 2 that allows the manufacturer to see what assessment procedures are required for the vessel.