A chromatography column is a pressure vessel. It has a defined maximum allowable pressure, contains fluid under pressure, and in the European market falls within the scope of the Pressure Equipment Directive 2014/68/EU. That regulatory fact shapes how columns are designed and documented, and understanding it is essential for anyone specifying, procuring, or qualifying downstream processing equipment.
This article is written for downstream engineers, MSAT professionals, and EPC project teams. It explains what the PED requires of manufacturers, how those requirements affect the equipment you specify, and what documentation you should expect to receive.
Directive 2014/68/EU replaced its predecessor 97/23/EC in July 2016. It applies to stationary pressure equipment with a maximum allowable pressure (PS) exceeding 0.5 bar. A chromatography column falls under the directive's definition of a vessel: a housing designed and built to contain fluid under pressure.
Annex I defines Essential Safety Requirements (ESRs) covering design, manufacture, materials, and testing. Manufacturers demonstrate compliance through conformity assessment before placing equipment on the market, after which it carries CE marking and a Declaration of Conformity. Chromatography columns are also subject to the Machinery Directive 2006/42/EC, which addresses operational and mechanical safety. Both declarations are issued together when a column is placed on the market.
The directive is a legal framework for market access, not a technical specification. It does not prescribe how to design a column or what materials to use. Instead, it defines a set of safety requirements that must be met, and conformity assessment procedures that must be followed, before equipment can be placed on the European market and CE marked.
The directive uses two parallel classification systems that are worth distinguishing clearly, because confusion between them is common even among experienced engineers.
The first is fluid group classification under Article 13. This divides fluids into Group 1 and Group 2 based on chemical hazard, not physical state. Group 1 covers dangerous substances: flammable, toxic, oxidising, or explosive fluids, whether liquid or gaseous. Group 2 covers everything else. A flammable gas and a flammable liquid both fall in Group 1. A non-hazardous buffer solution and a non-hazardous compressed gas both fall in Group 2.
The second is risk category classification under Annex II. This assigns equipment to Category I, II, III, or IV based on fluid group, equipment type, and a calculated parameter: PS x V for vessels, or PS x DN for piping. The categories determine the conformity assessment route and the level of notified body involvement required.
"Group 1" and "Category I" sound related but refer to entirely different things. A vessel containing a Group 1 fluid is not automatically in Category I. It is more likely to sit in a higher category, precisely because of the hazard the fluid represents.
For chromatography columns, the fluid group classification depends on what the column is designed to contain across its full operating envelope. A column used exclusively with aqueous buffers would qualify as Group 2. However, columns designed to handle organic solvents, whether as process mobile phases in preparative HPLC or as cleaning agents, must be classified as Group 1, since those solvents are flammable. Where a column is rated for organic solvents, Group 1 applies regardless of what fluid is present in any specific application. Risk category classification then follows from the PS x V product, as described in Annex II, Table 3 for Group 1 liquids.
For a Group 1 liquid vessel, classification follows Annex II, Table 3. The scope threshold is a PS x V product greater than 200 bar*L. Below that threshold, the column falls under Article 4(3), Sound Engineering Practice, and cannot carry CE marking under PED. Above it, the column enters the category system and must follow a formal conformity assessment route.
At the production scales typical for preparative chromatography, columns consistently exceed this threshold across all pressure ranges. A low-pressure column at 5 bar with an internal volume of 1,000 litres gives PS x V = 5,000 bar*L. A medium pressure column at 30 bar with 1,000 litres gives 30,000 bar*L. A high pressure column at 80 bar with 500 litres gives 40,000 bar*L. In each case the product is well above 200 bar*L, and the column falls within the category system.
What changes with pressure is not the threshold but the absolute PS x V value, which determines which category within Table 3 the column lands in. At the volumes and pressures typical of preparative chromatography columns, equipment consistently falls in Category II, which requires involvement of a notified body. The conformity assessment module applied determines the nature of that involvement: under Module A2, a notified body performs random product checks rather than inspecting every unit individually.
Regardless of category, a manufacturer placing a column on the EU market must maintain a technical file and issue a Declaration of Conformity. What varies with category is the extent of notified body involvement, not the fundamental design requirements, which apply across the board.
The technical file covers design basis, pressure calculations, materials traceability, and test records. The applied harmonized standard for unfired pressure vessels is EN 13445, which defines the calculation methods and material requirements in detail. The pressure calculations use formulas with a defined safety factor built in. The same factor applies at 5 bar as at 80 bar, so the margin is consistent across the pressure range. What changes at higher pressures is the absolute magnitude of the forces involved, and the calculations must reflect that. Hydrostatic test pressure is set as a multiple of the maximum allowable pressure and scales accordingly.
Weld procedures and welder qualifications must be documented and approved as a general requirement under the directive. This applies at every pressure range. It is a baseline, not an escalation.
For manufacturers without an externally certified quality management system, Module A2 is the conformity assessment route. Under Module A2, the manufacturer maintains the technical file and issues the Declaration of Conformity internally, but a notified body performs random product checks on manufactured units to verify that the design and documentation are accurate.
When a column is integrated into a chromatography skid with valves, sensors, pumps, and process piping, Article 2 introduces an additional layer. An assembly is defined as several pieces of pressure equipment forming an integrated and functional whole, and the manufacturer of the assembly is responsible for the conformity of the whole. Individual CE-marked components do not satisfy this requirement on their own. The category of the assembly is set by its highest-classified element, and the technical file must cover the integration as a system.
This means that even if each component in a skid is individually CE-marked, the system as a whole must be assessed as an assembly. Connection points, pressure ratings across the flow path, and any interactions between components that affect the pressure boundary all fall within scope. The Declaration of Conformity issued for the assembly must cover the integrated system, not just the collection of its parts.
PED compliance for a chromatography column manufacturer is built on three foundations: correct fluid group classification, which determines which Annex II table applies; accurate PS x V calculation, which determines the category and conformity assessment route; and a complete technical file, which is the documented evidence that the design meets the Essential Safety Requirements of Annex I.
For customers in regulated pharmaceutical environments, the Declaration of Conformity and the technical file behind it form part of the design history that supports equipment qualification. A complete technical file reflecting the actual pressure range and fluid classification of the column reduces open questions at the IQ stage, and that is a practical benefit on both sides.
The PED (2014/68/EU) regulates the pressure-bearing components and assemblies of equipment. It focuses on the vessel, piping, safety accessories, and pressure accessories, and sets Essential Safety Requirements for design, materials, manufacture, and testing. The Machinery Directive (2006/42/EC) regulates the machine as a whole, including operational hazards, control systems, guards, and user safety. Both apply to chromatography columns. A column will carry CE marks for both directives.
Group 1 fluid classification means the fluid is hazardous in some way: it is flammable, toxic, oxidising, or explosive. For chromatography columns, the relevant fluids are flammable organic solvents. A column is classified as Group 1 if it is designed to contain such solvents, even if the solvent is not present during a particular use. The classification is based on the design intent, not the actual contents at any moment.
Category II is a risk classification that sits between Category I (lowest risk) and Category III/IV (highest risk). A column in Category II requires involvement of a notified body in the conformity assessment process. The exact nature of that involvement depends on the module applied (for instance, Module A2 means random product checks, not unit-by-unit inspection).
A notified body is an independent third-party organization designated by an EU Member State to perform conformity assessment activities under the directive. Notified bodies have technical expertise and are accredited to verify that manufacturers' designs and documentation meet the Essential Safety Requirements. They are listed in a public NANDO database.
No, but PED compliance helps your qualification. The Declaration of Conformity and the technical file are part of the design history that you can use in your IQ/OQ documentation. A manufacturer's technical file should contain the design basis, pressure calculations, materials certifications, and test records. Having this documentation upfront reduces the number of questions you will need to ask during design phase qualification.
Check that it covers the specific column you have ordered, including the correct pressure rating (PS) and volume (V). Verify that the fluid group is stated (Group 1 for columns rated for organic solvents, Group 2 for buffer-only columns). Check that a notified body is listed if the column is in Category II or higher. Make sure the harmonized standard referenced is EN 13445. The document should also state the conformity assessment module used (typically Module A2).
Yes, but only if they fall below the scope threshold. A column with a PS x V product below 200 bar*L for Group 1 liquids falls under Sound Engineering Practice (Article 4(3)) and is not within PED scope. However, such columns are rare in preparative chromatography. Any column at significant scale and pressure will exceed this threshold. A manufacturer may still choose to design and document such a column to PED standards even if not required, which gives you better documentation for qualification.
If the column is placed on the EU market, it must carry a CE mark and be compliant with PED. The manufacturer is responsible for compliance, not the importer. Before accepting delivery, verify that the Declaration of Conformity is present and complete. If you are working with a non-EU supplier, ensure in your purchase order that the column will be supplied with full PED documentation including the technical file abstract or relevant sections.
Module A2 is a conformity assessment module under PED. It is the route available to manufacturers without a certified quality management system. Under Module A2, the manufacturer maintains the technical file and issues the Declaration of Conformity themselves. A notified body then performs random checks on manufactured units (not every single unit, but a statistical sample) to verify that the actual product matches the design documentation. This is less costly than full quality system certification, but still provides third-party verification.
Because the column may be used with different fluids across its lifetime. If the column is designed to be compatible with organic solvents for cleaning or alternative mobile phases, it must be rated for Group 1 from the start. Changing the fluid group after manufacture is not possible under PED. Therefore, most commercial chromatography columns are designed for and classified as Group 1, giving users maximum flexibility in what they can run through them.
The technical file is the manufacturer's documented evidence that the design meets the Essential Safety Requirements. It typically includes the design basis (what pressure, temperature, and materials the column is designed for), pressure calculations confirming that the vessel can withstand the specified pressure with a safety margin, materials certifications showing that the materials used match the design specification, and hydrostatic test results confirming that the finished column holds pressure without leakage or permanent deformation. This documentation can be referenced in your IQ/OQ as part of the design history, saving you from having to generate that evidence yourself.
Understanding the regulatory framework for your equipment early in a project saves time and reduces the risk of surprises during qualification. If you are specifying chromatography columns for a downstream processing system, or if you have questions about PED classification, documentation requirements, or how to use the technical file in your qualification, we are happy to discuss it.
Peak Biotech A/S designs and manufactures chromatography columns and systems for biopharmaceutical processing, covering low, medium, and high pressure applications. Our columns are certified under both PED 2014/68/EU and Machinery Directive 2006/42/EC, and we provide complete technical files with every unit.
1. Directive 2014/68/EU of the European Parliament and of the Council of 15 May 2014. Official Journal of the European Union, L 189, 27 June 2014. https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A32014L0068
2. Directive 2006/42/EC of the European Parliament and of the Council on the harmonisation of the laws of the Member States relating to machinery. Official Journal of the European Union, L 157, 9 June 2006.
3. European Commission — Guidelines related to the Pressure Equipment Directive 2014/68/EU. https://ec.europa.eu/DocsRoom/documents/23181
4. EU-OSHA — Directive 2014/68/EU: Pressure Equipment. https://osha.europa.eu/en/legislation/directive/directive-201468eu-pressure-equipment
5. EN 13445: Unfired Pressure Vessels. European Committee for Standardization (CEN).
6. EN ISO 12100: Safety of machinery. Basic concepts and general principles for design. International Organization for Standardization (ISO).