Mechanical design fundamentals (1/13)
97/23/EC - European Pressure Equipment Directive
Applications
All equipment that is pressurised 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 pressurisation of fluids, heat exchanger equipment, pipework, 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 categorised
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 oxidising 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 categorisations available to us. The
fluid must be categorised as a gas or liquid:
- If the fluid is a gas or vapour or if it is a liquid whose vapour pressure at the maximum allowable temperature is greater than 0,5 Barg it is categorised as a
gas.
- If the fluid is a liquid whose vapour pressure at the maximum allowable temperature is less than 0,5 Barg it is categorised 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.