Heat exchangers in refineries and petrochemicals: PED, ASME BPVC and API standards
The regulatory framework applicable to finned-tube heat exchangers, flue gas recuperators and condensing economisers in refinery and petrochemical installations.
In refineries, petrochemical plants and other process installations, finned-tube heat exchangers, gas recuperators and economisers operate under demanding conditions and are subject to a specific regulatory framework. Understanding how the European Pressure Equipment Directive, the ASME code and sector specifications interact allows the correct conception of each piece of equipment to be established from the basic engineering phase.
1. Equipment operating in this environment
In refining and petrochemical applications, finned-tube heat exchangers and gas recuperators fulfil essential functions in the thermal balance management of installations. The most common applications are heat recovery from combustion gases —where hot gases from the furnace or reformer transfer heat to combustion air or process water— and the cooling or heating of gaseous process streams.
In these services, the conception of the equipment with respect to the acid dew point of the gas is one of the most impactful technical decisions. Operating above the dew point limits recovery to sensible heat; conceiving the unit as a condensing economiser —designed to operate deliberately below the dew point— also recovers the latent heat of the water vapour present in the gases, achieving a higher overall thermal efficiency. Both strategies are technically valid and applicable in process installations.
BOIXAC works in the conception and supply of finned-tube heat exchangers, gas-gas recuperators and economisers —including condensing economisers— for industrial installations in sectors such as refining, petrochemicals, hydrogen production and other high-temperature processes. For each project, the BOIXAC technical team works with the actual process conditions, fluids, temperatures and regulatory requirements to identify the appropriate solution.
2. PED 2014/68/EU: the mandatory framework in Europe
For all pressure equipment placed on the market in the European Union, the Pressure Equipment Directive 2014/68/EU (PED) establishes the essential safety requirements that equipment must comply with before being put into service. Its application is mandatory regardless of whether the project also references international standards such as ASME or sector specifications such as API.
- Scope: the PED applies to pressure equipment with a maximum allowable pressure above 0.5 bar. Finned-tube heat exchangers and gas recuperators in industrial installations typically fall within its scope when they exceed the pressure and volume thresholds set out in Annex II.
- Fluid classification: the PED distinguishes between Group 1 fluids (flammable, toxic, oxidising or explosive under CLP) and Group 2 fluids (all others). In petrochemical installations, process gases containing hydrocarbons or H₂S are Group 1, activating the more demanding categorisation tables and potentially requiring the involvement of a Notified Body.
- CE marking: all equipment subject to the PED must bear the CE marking accompanied by the EU Declaration of Conformity before being put into service in Europe. Reference to other standards in a technical specification does not exempt equipment from this requirement.
- Technical documentation: the equipment's technical file must demonstrate compliance with the PED's essential safety requirements, including pressure calculations, material certificates and inspection records corresponding to the applicable conformity assessment module.
The PED category of a piece of equipment —from I to IV— determines the applicable conformity assessment module and, with it, whether or not a Notified Body must be involved. The category results from the intersection of the fluid Group and the PS×V product (vessels) or PS×DN (piping). In petrochemical installations with Group 1 fluids at elevated pressures, categories III or IV are frequently reached. Defining the category in the basic engineering phase allows the timescales and resources of the certification process to be planned correctly.
3. ASME BPVC: international calculation reference
The ASME Boiler and Pressure Vessel Code (BPVC), published by the American Society of Mechanical Engineers, is the reference code for the calculation and certification of pressure equipment in projects within the North American sphere and in numerous international projects where the process licensor or plant owner contractually requires it. Its knowledge is relevant for export projects and for installations where the client specifies ASME requirements.
When a European project simultaneously requires CE marking (PED) and ASME documentation, the reconciliation of both frameworks must be planned from the basic engineering phase: materials must be qualified under both systems, calculations must demonstrate compliance with both codes, and the inspection process must coordinate the requirements of the Notified Body and the Authorized Inspection Agency. Precisely defining the scope of each code from the outset prevents incompatibilities that could jeopardise the delivery schedule.
The material designation systems of the PED (EN standards) and ASME (SA/SB designations) are not directly interchangeable. An SA-516 Gr.70 material and a P265GH (EN 10028-2) have similar compositions but differ in allowable stress limits, Charpy impact test requirements and supply conditions. Formal equivalence requires case-by-case analysis and explicit acceptance by the inspection body or the client.
4. API specifications in the regulatory context
American Petroleum Institute (API) standards are technical specifications widely used in the refining sector to define requirements for specific equipment types. Their reference in a project specification is common in petrochemical projects, but their nature differs from that of pressure calculation codes.
- API as a specification standard, not a certification code: API standards establish material, inspection and documentation requirements for specific equipment types in the refining environment. They are not pressure calculation codes: they do not replace ASME VIII or EN 13445 but complement them. Reference to an API standard in a technical specification does not exempt equipment from PED compliance in the European market.
- Relevance for recuperators and economisers: in the heat recovery segment for process and combustion gases, the material, dimensional tolerance and documentation requirements applicable to each project may incorporate API specification references alongside PED requirements. BOIXAC works with the technical specifications of each project to identify the solution that meets the applicable regulatory requirements.
- API 571 as a damage reference: the API 571 standard Damage Mechanisms Affecting Fixed Equipment in the Refinery Industry catalogues material degradation mechanisms in process equipment. Its knowledge is relevant for correct material selection in gas recuperators and economisers operating in environments with corrosive gases or risk of acid dew point condensation.
5. Materials for finned-tube heat exchangers in process service
The selection of materials for the tubes and fins of a gas recuperator or economiser in a petrochemical installation determines its behaviour in contact with process gases, the operating temperature and the risk of acid condensation. There is no single solution: the optimum combination depends on the exact gas composition, the temperature range and the operating conditions.
| Component | Typical material | Application condition | Regulatory consideration |
|---|---|---|---|
| Tubes — general service | Carbon steel, stainless steel 304/316 | Process gases without significant H₂S, chlorides or acid condensation | PED: EN-designated approved material. ASME: qualified SA equivalent. |
| Tubes — corrosive gases | Stainless steel 316L, Duplex 2205 | Presence of H₂S, chlorides or controlled acid condensation risk | NACE MR0175 if H₂S under sour service conditions. PED Group 1 if flammable or toxic fluid. |
| Fins — general service | Aluminium (alloys 1100, 3003) | Neutral atmosphere, moderate temperature, no HCl, HF or strong alkalis | Verify galvanic compatibility with tube material in humid environments. |
| Fins — corrosive service | Stainless steel 316L | Gases with acid content, humid atmospheres or corrosive contaminants | Greater resistance than aluminium; lower thermal conductivity. Verify galvanic pair with tube. |
| Condensation zone (condensing economiser) | Stainless steel 316L or higher grade | Deliberate operation below the acid dew point | Acid condensate requires specifically resistant materials. Drainage geometry required. |
6. Acid dew point: two design strategies
In recuperators cooling combustion gases or process gases containing SO₂, SO₃, HCl or other acidic compounds, the temperature at which the gas begins to condense acids on the equipment surfaces —the acid dew point— is a determining design parameter. Two technically valid strategies exist to address it:
The unit is conceived so that the minimum wall temperature remains above the acid dew point at every point, thereby avoiding condensation. Only the sensible heat of the gases is recovered. This is the appropriate strategy when the aggressiveness of the condensate is high or when condensate management is not viable for the project.
The unit is conceived to operate deliberately in condensing mode, also recovering the latent heat of the water vapour present in the gases. The result is a higher overall thermal efficiency. This strategy requires materials suited to contact with the acid condensate, geometry that facilitates drainage and condensate management systems. It is viable for combustion gases from natural gas, diesel, fuel oil and other fuels when the project allows it. BOIXAC can supply condensing economisers for this service.
7. Technical documentation for projects in process installations
In refining and petrochemical projects, the technical documentation associated with heat transfer equipment is as important as the equipment itself. The engineering, procurement and commissioning processes of these installations require specific documentation that demonstrates compliance with the project's regulatory requirements.
- PED documentation: for equipment subject to the PED, documentation includes the EU Declaration of Conformity, the technical file with pressure calculations per EN 13445 or an accepted equivalent code, material certificates (typically EN 10204 type 3.1), inspection records and non-destructive examination results applicable to the equipment category.
- Equipment data book: in process projects, it is common for the client to require a complete equipment data book including drawings, bill of materials, material certificates, qualified welding procedures, NDE records, pressure test reports and other project-specific documents.
- Material traceability: petrochemical projects typically require EN 10204 type 3.1 material certificates (or ASME equivalent) for all pressure-bearing materials. Traceability from the material heat to the final equipment forms part of the technical file.
- BOIXAC provides the technical documentation of supplied equipment required by the project engineering team to complete the certification and approval process in process installations.