Inspectioneering Journal

The European Pressure Equipment Directive

This article appears in the July/August 2003 issue of Inspectioneering Journal.

The European Pressure Equipment Directive

Note: This information was obtained from the European Pressure Equipment Directive of the European Commission web site. The Inspectioneering® Journal is not responsible for nor does it warrant the accuracy, completeness or validity of information contained in this article. It is the responsibility of readers to confirm the information with their jurisdictional regulatory bodies prior to use.

This document gives an overview about the structure and the contents of the Pressure Equipment Directive. The full text including Annexes is presented in the next sub-sections of the site. References and links are given for easier usability. It should be noted that the Pressure Equipment Directive has been published in the Official Journal of the European Communities and can be ordered from the Office for the official publications of the European Communities via the EUR-LEX site.

The Pressure Equipment Directive (97/23/EC) was adopted by the European Parliament and the European Council in May 1997. It has initially come into force on 29 November 1999. From that date until 28 May 2002 manufacturers have a choice between applying the pressure equipment directive or continuing with the application of the existing national legislation. From 29 May 2002 the pressure equipment directive will be obligatory throughout the European Union.

The directive provides, together with the directives related to simple pressure vessels (87/404/EC), transportable pressure equipment (99/36/EC) and Aerosol Dispensers (75/324/EEC), for an adequate legislative framework on European level for equipment subject to a pressure hazard.

The Directive arises from the European Community’s Programme for the elimination of technical barriers to trade and is formulated under the “New Approach to Technical Harmonisation and Standards”. Its purpose is to harmonise national laws of Member States regarding the design, manufacture, testing and conformity assessment of pressure equipment and assemblies of pressure equipment. It therefore aims to ensure the free placing on the market and putting into service of the equipment concerned within the European Union and the European Economic Area. Formulated under the New Approach the directive provides for a flexible regulatory environment that does not impose any detailed technical solution. This approach allows European industry to develop new techniques thereby increasing international competitiveness. The pressure equipment directive is one of a series of technical harmonisation directives for machinery, electrical equipment, medical devices, simple pressure vessels, gas appliances etc.

The Directive concerns manufacturers of items such as vessels pressurised storage containers, heat exchangers, steam generators, boilers, industrial piping, safety devices and pressure accessories. Such pressure equipment is widely used in the process industries (oil & gas, chemical, pharmaceutical, plastics and rubber and the food and beverage industry), high temperature process industry (glass, paper and board), energy production and in the supply of utilities, heating, air conditioning and gas storage and transportation.

Under the Community regime of the Directive, pressure equipment and assemblies above specified pressure and/or volume thresholds must:

  • be safe;
  • meet essential safety requirements covering design, manufacture and testing;
  • satisfy appropriate conformity assessment procedures; and carry the CE marking and other information.
  • Pressure equipment and assemblies below the specified pressure /volume thresholds must:
  • be safe;
  • be designed and manufactured according to sound engineering practice; and
  • bear specified markings (but not the CE marking).

The introduction of the new legislation related to pressure equipment concerns a large number of industries ranging from small and middle-sized manufacturers to the big chemical industries. Their total European market is estimated at more than 65 billions EURO per year. Both, manufacturers and users will benefit from the new regulatory environment as it will open up markets and, at the same time, facilitate the application of new technologies.

The adaptation to the new directive will however necessitate considerable efforts by the manufacturers concerned. To ensure that the directive is understood and applied in a coherent manner the results of important work carried out on a European level need to be made available to economic operators and in particular to manufacturers.

Terms Used

Essential safety requirements (ESRs) (Annex I) lay down the necessary safety elements for protecting public interest. Essential safety requirements for design, manufacture, testing, marking, labelling, instructions and materials, usually written in general terms, are mandatory and must be met before products may be placed on the market in the European Community.

Conformity Assessment (Article 10) must be undertaken by the manufacturer or notified body, depending on the category of the equipment, in order to demonstrate that the essential safety requirements are met.

Conformity Assessment Modules )(Annex III) The New Approach has introduced a modular approach to conformity assessment, thereby subdividing it into a number of independent activities. Modules differ according to the type of assessment (e.g. documentary checks, type approval, design approval, quality assurance) and the organisation carrying out the assessment (i.e. the manufacturer or a third party).

Sound Engineering Practice (Article 3.3) applies to equipment that is not subject to conformity assessment but must be designed and manufactured in accordance with the sound engineering practice of a Member State in order to ensure safe use. That equipment must ensure that design and manufacture takes into account all relevant factors influencing safety during the intended lifetime. The equipment must be accompanied with adequate instructions for use and must bear the identification of the manufacturer. The responsibility for compliance with the PED lies solely with the manufacturer.

Notified Body (Article 12) is a semi- official or private technical orgnisation appointed by Member States, either for approval and monitoring of the manufacturers’ quality assurance system or for direct product inspection. A Notified Body may be specialised for certain products/product categories or for certain modules.

Recognised Third Party Organisations (Article 13) are appointed by Member States to carry out the approval of welding procedures and personnel and non- destructive testing personnel.

User Inspectorates (Article 14) are appointed by Member States to carry out the tasks of notified bodies within their own companies under Modules A1, C1, F and G only. (The CE marking should not be affixed to pressure equipment and assemblies assessed by user inspectorates).

CE Marking (Article 15 ) declares the completion of conformity assessment and that the equipment or assembly complies with the provisions of the Directive and meets the essential safety requirements.

Published Harmonised (European) Standards (Article 5.2), list are a specific subset of European Standards (EN, produced by CEN and available from the national Standards Institutes) with particular consideration of the Essential Safety Requirements the reference number of which is published in the Official Journal of the European Commission. The use of a Published Harmonised Standard in the design and manufacture of a product will give the presumption of conformity (Article 5.1) to those ESRs listed in Annex ZA of the particular Harmonized Standard.

The Directive

Scope (Article 1)

The Directive applies to the design, manufacture and conformity assessment of pressure equipment and assemblies of pressure equipment with maximum allowable pressure greater than 0.5 bar above atmospheric pressure (i.e. 1,5 bar of absolute pressure)
Definitions (Article 1)

The term pressure equipment includes vessels, piping, safety accessories and pressure accessories. Where applicable, pressure equipment includes elements attached to pressurised parts, such as flanges, nozzles, couplings, supports, lifting lugs etc.

Vessels are defined as a housing designed and built to contain fluids under pressure.

Piping means piping components intended for the transport of fluids, when connected together for integration into a pressure system.

Safety accessories means devices designed to protect pressure equipment against the allowable limits being exceeded.

Pressure accessories means devices with an operational function and having pressure bearing housings.

Assemblies mean several pieces of pressure equipment assembled by a manufacturer to constitute an integrated and functional whole.

Exclusions(Article 1.3)

In a number of cases pressure equipment - although designed for a maximum allowable pressure above the limit - is excluded, for example:

  • equipment which is already regulated at EU level;
  • equipment presenting a minor pressure hazard (category I of the PED) and which is covered by directives on machinery, lifts, low voltage, medical devices, gas appliances and on explosive atmospheres;
  • equipment which does not present any significant pressure hazard, such as for distribution of water, radiators and piping for hot water heating systems, carbonated drink containers;
  • equipment which presents a significant pressure hazard but for which neither the free circulation aspect nor the safety aspect necessitated its inclusion, e.g. high voltage switch gear.

Equipment prototypes to be shown at trade fairs does not have to conform with the requirements of the Directive as long as appropriate safety measures are taken.

Free Movement (Article 4)

Member States of the EU may not, on the grounds of hazards due to pressure, prohibit, restrict or impede the placing on the market and putting into service of pressure equipment and assemblies which comply with the provisions of the PED. Member States are to presume that pressure equipment and assemblies bearing the CE marking and accompanied by the EC declaration of conformity satisfy the provisions of the PED.

Safeguard Procedure

Member States are, however, to perform market surveillance to take all appropriate measures to withdraw from the market pressure equipment or assemblies bearing the CE marking which is liable to endanger the safety of people and, where appropriate, domestic animals or property.

Product Classification (Article 3)

In order to determine how the Directive will apply to specific items of pressure equipment a manufacturer needs to classify the equipment into one of four conformity assessment categories: or Categories I to IV. I relates to the lowest, category IV to the highest, hazard category.

Equipment below Category I comes under “Sound Engineering Practice” (SEP) and is not subject to conformity asessment.

In order to determine which category an item of equipment falls into the manufacturer needs to identify:

  • the type of equipment - vessel / steam generators / piping
  • the state of the intended fluid contents - gaseous or liquid
  • the fluid group of the intended contents - Group 1 or Group 2

Group 1 comprises those fluids classified according to the EC Directive on the classification of dangerous substances as:

  • explosive
  • extremely flammable
  • highly flammable
  • flammable (where the maximum allowable temperature is above flashpoint)
  • very toxic
  • toxic
  • oxidising

Group 2 comprises all other fluids including water/steam.

Depending in the above one of the nine tables in Annex II of the Directive (Table 1) determine the aplicable conformity assessment category (SEP, I, II, III or IV).

See Table 1. Product Classifications and relevant tables

Table 1. Product Classifications and relevant tables.
Table 1. Product Classifications and relevant tables.

On each of these graphs (1-9) maximum allowable pressure (PS) (bar) is plotted against, for vessels, the volume in litres, V(L), and for piping, the nominal size (DN). These tables have up to five bands relating to the different categories (SEP, I, II, III or IV). Demarcation lines on each table indicate the upper limit of maximum allowable pressure and volume or nominal size for each category. The manufacturer has to plot the maximum allowable pressure and volume or nominal size for their piece of equipment on the relevant chart to identify which category the item of equipment falls into. In general the lower the pressure and volume the lower the category for the equipment.

Pressure accessories: Tables 1 to 4 for vessels or tables 6 to 9 for piping in Annex II are applicable depending on whether the volume V or the nominal size DN is considered appropriate for classification of the pressure accessory. Where both the volume and the nominal size are considered appropriate, the pressure accessory must be classified in the highest category.

Safety accessories: These are generally classified under category IV. Safety accessories manufactured for specific equipment may be classified in the same category as the equipment they protect.

Assemblies: Specific provisions (article 10.2) are applicable which are based on the classification of the individual parts of pressure equipment of which the assembly is composed.

Technical Requirements (Article 3)

The Directive requires that all pressure equipment and assemblies within its scope must be safe when placed on the market and put into service. For equipment falling under ‘sound engineering practice’ (SEP) the essential requirements and the certification procedures are not applicable.

Pressure Equipment under categories I, II, III and IV must meet the essential requirements given in Annex I of the Directive. Assemblies which include at least one item of pressure equipment classified in Categories I to IV will also be required to meet the essential safety requirements. These include extensive requirements for design, manufacturing, testing, marking and labelling and materials.

The manufacturer is obliged to analyse the hazards in order to identify those that apply to his equipment. He must design, manufacture and check his equipment to ensure its safety with respect to their use under reasonably foreseeable conditions. In addition, the manufacturer must interpret and apply the essential requirements in such a way as to take account of the state-of-the-art at the time of design. That latter requirement highlights the evolutive character of the essential requirements that is inherent in the new approach.

With respect to materials the manufacturer of pressure equipment must adhere to the essential safety requirements by using appropriate materials:

  • which comply with harmonised standards
  • covered by European Approval of Materials in accordance with (Article 11)
  • evaluated by a particular material appraisal

European Approval of Materials (Article 11) is a technical document defining the characteristics of materials intended for repeated use in the manufacture of pressure equipment the type of which is NOT already covered by a harmonised standard. Notified bodies issue these documents. The notified body shall determine and perform the appropriate inspections and tests to certify the conformity of the types of material with the corresponding requirements of the PED.

Special Requirements are given in addition to the applicable requirements of Sections 1 to 4 (General, Design, Manufacturing and Materials) of Annex I for ‘Fired or otherwise heated pressure with a risk of overheating in Section 5 and Section 6.

Specific quantitative requirements for certain pressure equipment materials are given as general rules in Section 7 of Annex I. The provisions laid down in this section supplement the essential requirements of Sections 1 to 6 for the pressure equipment to which they apply. These give allowable stresses, joint coefficients, hydrostatic test pressures and material characteristics. Values not to be exceeded for the permissible general membrane stress for predominantly static loads and for temperatures outside the range in which creep is significant are given for ferritic steel, austenitic steel, non alloy or low alloy cast steel, aluminium and aluminium alloys. Coefficients are given for welded joints.

Equipment manufactured to Harmonised European Standards is presumed to comply with the Essential Safety Requirements. The European Committee for Standardisation (CEN) is producing a series of Harmonised European Standards in support of the PED. The work programme includes product and supporting standards. Product standards include unfired pressure vessels, shell and water tube boilers, piping and safety valves. Supporting standards include welding, non- destructive testing and materials.

Permanent joining of components which contribute to the pressure resistance of the equipment and components which are directly attached to them must be carried out by suitably qualified personnel according to suitable operating procedures. For pressure equipment in categories II, II and IV operating procedures and personnel must be approved by a competent third party which at the manufacturers discretion, may be a notified body or a third party organisation recognised by a Member State. To carry out these approvals the third party must perform examinations and tests as set out in the appropriate harmonised standards or equivalent examinations or tests.

Conformity Assessment (Article 10): Before putting pressure equipment related to categories I to IV on the market, the equipment has to be subject to the appropriate conformity assessment procedures (modules). According to the category of the equipment, manufacturers will be given a choice of the ‘modules’ shown in Tables 2 and 3.

Manufacturers may chose either a procedure based on product control or a procedure based on quality systems. Furthermore the modules attributed to a higher hazard category may be used in lower categories.

For conformity assessment of assemblies the provisions of article 10.2 apply. This requires, that an item of pressure equipment, which is part of an assembly, is assessed according to the tables in annex II and an assessment is carried out on the integration of each item.

The modules for products in Categories II, III and IV require the involvement of ‘notified bodies’ (Article 12), appointed by Member States, either in the approval and monitoring of the manufacturers’ quality system or in direct product inspection. ‘Recognised third-party organisations’ (Article 13) may also be appointed by Member States to carry out the approval of welding procedures and personnel and non- destructive testing personnel as required for pressure equipment assemblies in Categories II, II and IV. ‘User inspectorates’ (Article 14) may also be appointed by Member States to carry out the tasks of notified bodies within their own organisations under Modules A1, C1, F and G only (the CE marking should not be affixed to pressure equipment and assemblies assessed by user inspectorates).

See Table 2. Modules for each category 

Table 2. Modules for each category.
Table 2. Modules for each category.

See Table 3. Conformity Assessment Procedure for each module 

Table 3. Conformity Assesment Procedure for each module.
Table 3. Conformity Assesment Procedure for each module.

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