Pressure equipment can store substantial energy. Failure involving compressed gas, steam, hot liquid or hazardous process fluid can lead to rupture, fragmentation, uncontrolled release, fire, explosion or serious injury.
Directive 2014/68/EU — commonly known as the Pressure Equipment Directive or PED — establishes the European conformity framework for stationary pressure equipment and assemblies with a maximum allowable pressure greater than 0.5 bar.
Unlike many other CE marking regimes, PED uses a graduated risk-based classification system. The required compliance route depends on equipment type, maximum allowable pressure, vessel volume or piping nominal size, fluid characteristics and fluid group.
These parameters determine whether equipment is subject to Sound Engineering Practice or falls into Category I, II, III or IV. Classification then determines the available conformity assessment modules and level of independent involvement required.
This GAR Insight provides manufacturers, fabricators, engineering companies, exporters and project stakeholders with a practical understanding of how PED classification, engineering and conformity assessment work together.
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Explore PED scope, classification, fluid groups, materials, welding, inspection, NDT, conformity assessment, technical documentation and CE marking.
Understanding the Pressure Equipment Directive
Directive 2014/68/EU establishes requirements for the design, manufacture and conformity assessment of stationary pressure equipment and assemblies with a maximum allowable pressure greater than 0.5 bar.
PED does not impose one identical conformity assessment procedure on every pressure product. Equipment is classified according to increasing risk, and the resulting category determines which conformity assessment modules may be used.
Which Products Fall Within the PED?
The PED covers several forms of stationary pressure equipment. Correctly identifying the product type is important because vessels, piping and other pressure products can follow different classification rules.
Pressure Vessels
Housings designed and built to contain fluids under pressure.
Piping
Piping components intended for transport of fluids when connected together as part of a pressure system.
Pressure Accessories
Devices having an operational function and containing pressure-bearing housings.
Safety Accessories
Devices intended to protect pressure equipment against allowable limits being exceeded.
Fired or Heated Equipment
Certain equipment used for generation of steam or superheated water and presenting a risk of overheating.
Assemblies
Several items of pressure equipment assembled by a manufacturer into an integrated and functional whole.
The Parameters That Drive PED Classification
PED classification cannot be determined from pressure alone. Several technical parameters work together to determine the applicable Annex II classification table and resulting category.
PS
Maximum allowable pressure specified by the manufacturer.
V
Internal volume used in classification of applicable pressure vessels.
DN
Nominal size used particularly for piping and certain pressure accessories.
Fluid Group
The process fluid is classified into Group 1 or Group 2.
Fluid State
Classification differs according to whether the relevant fluid is treated as a gas/vapour or liquid.
Equipment Type
Different PED classification tables apply to vessels, piping, fired equipment and other pressure products.
Identify Equipment
Vessel, piping, accessory or assembly.
Determine PS
Establish maximum allowable pressure.
Determine V / DN
Identify the relevant size parameter.
Classify Fluid
Determine Group 1 or Group 2.
Determine State
Gas/vapour or liquid.
Select Table
Use the applicable Annex II table.
Determine Category
SEP or Category I–IV.
Select Module
Choose a permitted conformity assessment route.
Understanding PED Fluid Groups 1 & 2
PED divides fluids into two groups. This distinction is important because fluid classification can materially influence the resulting pressure-equipment category.
Fluid Group 1
Includes substances and mixtures falling within specified hazardous classes and categories referenced through the applicable CLP framework.
Fluid Group 2
Consists of substances and mixtures not included within the PED definition of Group 1.
Depending on the applicable classification, Group 1 can include substances presenting hazards associated with explosivity, flammability, oxidising properties, acute toxicity and other specified hazard classes.
Sound Engineering Practice & Categories I–IV
Once the appropriate PED classification table has been selected, the combination of pressure, size and fluid characteristics determines the applicable regulatory level.
| Classification | General Regulatory Position | PED CE Marking |
|---|---|---|
| Sound Engineering Practice | Equipment falling under Article 4(3) must be designed and manufactured according to sound engineering practice. | No |
| Category I | Lowest PED conformity assessment category. | Yes |
| Category II | Increased level of regulatory conformity control. | Yes |
| Category III | Higher-risk pressure equipment requiring more extensive conformity assessment. | Yes |
| Category IV | Highest PED conformity assessment category. | Yes |
Essential Safety Requirements
Pressure equipment subject to the PED category requirements must satisfy the applicable Essential Safety Requirements established in Annex I.
Pressure Design
Design should consider pressure, temperature, appropriate design methods and suitable safety factors.
Design Loadings
Supports, reactions, external loads, thermal effects and foreseeable operating conditions should be considered.
Corrosion & Erosion
Expected loss of material and foreseeable degradation should be addressed within the design.
Fatigue
Repeated pressure, thermal and mechanical loading can require fatigue evaluation.
Overpressure Protection
Suitable protective measures should prevent allowable pressure or temperature limits from being exceeded.
Safe Operation
Filling, draining, maintenance and foreseeable operating conditions should be considered during design.
Materials for Pressure Equipment
Material selection is a fundamental part of pressure-equipment safety. Pressure-bearing materials must possess characteristics appropriate to the intended operating and design conditions.
Material Properties
Strength, toughness, ductility and temperature capability should be suitable for the intended service.
Fluid Compatibility
Materials should be suitable for the contained fluid and foreseeable corrosion, erosion or degradation mechanisms.
Traceability
Appropriate material identification should be maintained throughout fabrication.
Approval Route
Material conformity may involve harmonised materials, European Approval for Materials or Particular Material Appraisal as applicable.
Welding & Permanent Joining
Permanent joints contributing to the pressure resistance of equipment are safety-critical manufacturing operations.
Welding Procedures
Procedures should be appropriately specified, qualified and controlled.
Welding Personnel
Welders and welding operators should possess appropriate qualifications.
Joint Preparation
Fit-up, preparation, cleanliness and consumable control can directly influence joint integrity.
Heat Treatment
Preheat, post-weld heat treatment and other thermal controls should be applied where required.
NDT, Final Assessment & Pressure Testing
Inspection and testing provide objective evidence that the manufactured equipment corresponds to the technical design and that safety-critical fabrication has been completed satisfactorily.
Visual Examination
Workmanship, geometry, dimensions and visible fabrication condition.
Radiographic Testing
Volumetric examination of suitable pressure-retaining welded joints.
Ultrasonic Testing
Volumetric examination of appropriate welds and materials.
Surface NDT
Liquid penetrant or magnetic particle examination where applicable.
Pressure Testing
Final assessment normally includes suitable pressure-strength testing.
Final Inspection
Verification that completed equipment corresponds with the applicable technical documentation.
PED Conformity Assessment Modules
Once the pressure-equipment category has been determined, the manufacturer selects one of the conformity assessment procedures permitted for that category.
| PED Category | Available Conformity Assessment Routes | General Assessment Level |
|---|---|---|
| Category I | Module A | Internal production control |
| Category II | Modules A2, D1 or E1 | Independent involvement according to the selected module |
| Category III | B (design type) + D, B (design type) + F, B (production type) + E, B (production type) + C2, or H | Higher-level conformity assessment |
| Category IV | B (production type) + D, B (production type) + F, G or H1 | Highest PED conformity assessment level |
Pressure Assemblies & Complete Systems
PED also applies to assemblies consisting of several items of pressure equipment assembled by a manufacturer into an integrated and functional whole.
Component Status
Individual pressure items should possess the appropriate conformity status for their intended application.
Integration
The interaction and connection of pressure components must be considered at assembly level.
Protection
Safety accessories and protection against exceeding allowable limits should be evaluated for the complete system.
Assembly Conformity
The complete assembly can require its own PED conformity assessment.
PED Technical Documentation
Technical documentation provides the evidence supporting the manufacturer’s demonstration that the pressure equipment satisfies the applicable PED requirements.
EU Declaration of Conformity & CE Marking
Once pressure equipment within Categories I–IV has successfully completed the applicable conformity assessment procedure, the manufacturer prepares the EU Declaration of Conformity and affixes the CE marking.
Manufacturer Identification
Manufacturer and relevant economic-operator information should be appropriately provided.
Equipment Identification
Type, model, serial number and other relevant traceability information.
Applicable Legislation
Identify the PED and other applicable European harmonisation legislation.
Standards & Assessment
Identify applicable standards and relevant conformity assessment information.
Depending on the product and its functions, additional European legislation can apply alongside the PED. The complete conformity strategy should therefore consider all applicable Union requirements rather than treating pressure equipment compliance in isolation.