The PED (Pressure Equipment Directive – 97/23/EC of the European Parliament and of the Council of 29 May 1997 on the approximation of the laws of the member States concerning pressure equipment) is applicable in Europe since December 1999 and mandatory since end of May 2002.
This directive applies to the design, manufacturing and conformity assessment of pressurised equipment or assemblies with service pressure of more than 0.5 bar and a PV (Pressure water capacity) of more than 50 bar l (10 bar = 1 MPa).
In the case of the hydrogen energy applications, it is particularly relevant for all pressure vessels (e. g. cylinders) and safety accessories (valves, flexible hoses, connectors) used for hydrogen refuelling station.
This pressure equipment Directive allows to use everywhere in the EU the same design for the pressure vessels and associated accessories.
Since this Directive is mandatory in Europe, a number of “Notified Bodies” have been notified to Brussels by the authorities of each EU member state. These notified bodies can make the “evaluation of conformity” of the pressure equipment ; this evaluation is confirmed by the “CE” mark applied onto the equipment. Any notified body (from every country) can approve a CE marked equipment to be used in every country of the EU.
This Directive only defines the “essential requirements” which are given in its Annex 1. Detailed requirements are given in the harmonized standards (e.g. prepared by CEN). These EN-Standards are not mandatory, other procedures or “state of the Art” can be used by the manufacture in order to demonstrate to the notified body that the essential requirements are fulfilled.
Contrary to the TPED, this European Directive doesn’t cover the use of the equipment (operational requirement, periodic inspection, …) which are still under national regulations. This may create difficulties if such equipment are to be moved from one country to another.
Essential safety and health requirements given in the Annex 1 of the Directive are summarised below.
General requirements
The manufacturer has to apply the general safety principles given in the Directive. It concerns especially the risks assessment of its system.
Design
- The manufacturer must ensure the safety of its equipment throughout its intended life;
- Pressure vessel must be designed for adequate strength (internal/external pressure, traffic, wind, corrosion, fatigue, …). It shall be properly designed using comprehensive calculation methods and experimental design method;
- Provisions are given to ensure safe handling and operation (especially related to closures and openings, dangerous discharge of pressure relief blow-off, …);
- Pressure equipment shall be designed and constructed so that all necessary examinations to ensure safety can be carried out;
- Adequate means must be provided for the draining and venting of pressure equipment where necessary (during operation ad during cleaning, inspection and maintenance);
- Where necessary, adequate allowance or protection against corrosion or other chemical attack must be provided;
- Where severe conditions of erosion or abrasion may arise, adequate measures must be taken to minimise effects and/or to replace the parts which are most affected.
- Assemblies must be so designed so as to not create a hazard;
- Where appropriate, the pressure equipment must be so designed and provided with accessories, or provision made for their fitting, as to ensure safe filling and discharge in particular with respect to hazards from filling (overfilling, overpressure) and discharge (uncontrolled release of the pressurised fluid) and unsafe connections or disconnections;
- Protection against exceeding the allowable limits of pressure equipment must be provided (adequate protective devices);
- Safety accessories must be reliable and suitable for their intended duty, be independent of other functions, comply with appropriate design principles (in particular fail-safe modes, redundancy, diversity and self-diagnosis);
Manufacturing
- Preparation of the component parts must not be detrimental to the safety of the pressure equipment (due to defects, cracks, changes);
- Permanent joints and adjacent zones must be free of any surface or internal defects detrimental to the safety of the equipment. Non-destructive tests of permanent joints must be carried out by suitable qualified personnel. ;
- Heat treatment must be applied when there is a risk that the manufacturing process will modify the material properties impacting on the safety ;
- The material making up the components of the equipment must be identified through suitable procedures ;
- Pressure equipment must be subjected to final assessment : final inspection, proof test, inspection of safety devices ;
- The CE marking and the required information (as listed in the Annex 1 of the Directive) must be given on the pressure equipment;
- When pressure equipment is placed on the market, it must be accompanied, as far as relevant, with instructions for the user, containing all the necessary safety information (for mounting and assembling, putting into service, use, maintenance).
If appropriate, these instructions must also refer to hazards arising from misuse.
Materials
- Materials used for the manufacture of pressure equipment must be suitable for such application during the scheduled lifetime unless replacement is foreseen. The possibility of hydrogen embrittlement must be taken into account.
Specific pressure equipment requirements
- Fired or otherwise heated pressure equipment with a risk of overheating (steam and hot-water generators and process-heating equipment for other than steam and hot water generation) must be calculated, designed and manufactured so as to avoid or to minimise risks of a significant loss of containment from overheating.
- Piping must be designed and manufactured so that to ensure safety of the system (e.g. pay attention to the potential damage from turbulence and formation of vortices and to the risk of fatigue due to vibrations in pipes).
Specific quantitative requirements for certain pressure equipment
- Provisions given in this section apply as a general rule for: allowable stresses, joint coefficients, pressure limiting devices particularly for pressure vessels, hydrostatic test pressure and material characteristics.
<< | Content | >>
