Heat transfer

Thermodynamics is the branch of physics that studies thermal energy and is based on the so-called laws of thermodynamics that describe its properties and how energy is transferred and converted into other forms.

The laws of thermodynamics are as follows:

  • First Law of Thermodynamics (Principle of Conservation of Energy): The total energy of a physical system is constant, and the difference between the initial and final energy is equal to the amount of energy that is transferred or which becomes work.
  • Second Law of Thermodynamics (Principle of Entropy): In a thermodynamic transaction, the total amount of entropy of a system and its surroundings always increases or remains constant.
  • Third Law of Thermodynamics (Zero Entropy Principle): At absolute zero temperature, the entropy of a perfect pure system is zero.

Some of the main factors we have to keep in mind when we talk about thermodynamics are temperature, pressure, amount of substance and entropy.

In this section we talk about thermal equilibrium, temperature, the kinetic theory of gases, heat capacity, sensible heat, latent heat, phase changes, the heat capacity of a solid, the heat capacity of a gas, adiabatic systems, types of heat exchange, convection, conduction, radiation, psychrometric diagram, etc.

How heat exchangers contribute to EU 2030 targets and the Energy Efficiency Directive 2023/1791

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How heat exchangers contribute to EU 2030 targets and the Energy Efficiency Directive 2023/1791 | BOIXAC Technical blog › Sustainability and energy efficiency How heat exchangers contribute to EU 2030 targets and the Energy Efficiency Directive 2023/1791 The EED 2023/1791 and the Fit for 55 package have turned industrial energy efficiency into a legal obligation. We analyse the regulatory framework and the role of heat recovery systems as a verifiable efficiency measure. BOIXAC Tech SLDirective (EU) 2023/1791 · Fit for 55 · EU 2030Technical read — 8 min Important notice — informational content onlyThe contents of this article, including references to dates, thresholds and regulatory obligations, are strictly informational and for general guidance only. European regulations and their national transposition are subject to changes. BOIXAC Tech SL accepts no liability arising from decisions taken based on this article. Always consult a qualified legal or energy adviser. Table of contents The context: energy efficiency as a legal obligation Corporate obligations under the EED 2023/1791 The Energy Efficiency First principle The Fit for 55 package and the EU Taxonomy Heat recovery as a verifiable efficiency measure Industrial waste heat: the available potential The energy audit as a starting point The convergence of the EED 2023/1791, the Fit for 55 package and the EU 2030 climate target creates a framework in which recovering waste heat from industrial processes is no longer an optional improvement but a priority measure that mandatory energy audits will systematically place on the agenda. 55%EU GHG emission reduction by 2030 (vs 1990) 11.7%EU final energy consumption reduction by 2030 1.9%Mandatory annual energy savings 2028–2030 10 TJConsumption threshold for mandatory energy audit The context: energy efficiency as a legal obligation For decades, energy efficiency in industry was a voluntary decision. The adoption of the Fit for 55 package in 2021 and the entry into force of Directive (EU) 2023/1791 of 13 September 2023 — the new Energy Efficiency Directive (EED), recast — have turned energy efficiency into a legal obligation for a significant number of European industrial companies. The central objective is clear: to reduce the EU’s final energy consumption by at least 11.7% by 2030 compared to reference projections, as an essential contribution to the climate target of reducing emissions by 55% compared to 1990 levels (Regulation (EU) 2021/1119). Corporate obligations under the EED 2023/1791 The main novelty of the EED 2023/1791 is that obligations no longer depend on company size but on actual energy consumption. Key deadlines and thresholds of the EED 2023/1791 11 October 2025: deadline for transposition of the Directive into national legislation of EU Member States. 11 October 2026: first mandatory energy audit for companies with average annual consumption exceeding 10 TJ (≈ 2.78 GWh) over the three preceding years. Minimum frequency: every four years. 11 October 2027: mandatory implementation of a certified Energy Management System (EnMS) (ISO 50001) for companies with consumption exceeding 85 TJ (≈ 23.6 GWh). ℹ️ Dates are from the Directive text published in the OJ EU. National transposition may introduce variations. Always consult the applicable national regulations. The ‘Energy Efficiency First’ principle The EED 2023/1791 elevates for the first time to legal status the Energy Efficiency First principle. Recovering waste heat from one’s own processes must be the first option to evaluate before installing new heat generation. Practical implication for industry An industrial process with flows of hot gases, cooling water or thermal effluents is, under the EED 2023/1791 framework, an internal energy resource that must be systematically evaluated. Failing to recover it is a missed opportunity that the mandatory energy audit will bring to light. The Fit for 55 package and the EU Taxonomy The EED 2023/1791 is part of the Fit for 55 package, which includes the revision of the EU ETS, the Renewable Energy Directive (RED III), the EU Taxonomy Regulation and the EED itself. Financing opportunity: EU Taxonomy and green finance Investments in industrial heat recovery may qualify as EU Taxonomy-aligned activities. This qualification facilitates access to green financing, sustainable bonds and European programmes such as InvestEU or Next Generation EU funds — particularly relevant for companies operating in or exporting to the EU. Heat recovery as a verifiable efficiency measure Technically measurable and verifiableSavings are obtained using Q = ṁ · cp · ΔT, where all variables can be continuously measured and independently verified. Compatible with the M&V protocols required by the EED to certify savings. Eligible for support mechanismsIn France (CEE), Spain (CAE) and other EU countries, industrial heat recovery installations have standardised operation sheets enabling financial incentives based on kWh saved over equipment lifetime. Directly reduces CO₂ emissionsBy recovering heat that would otherwise require burning fuel, direct CO₂ emissions are reduced (Scope 1, GHG Protocol / ISO 14064). Compatible with EU ETS and CSRD 2022/2464/EU reporting requirements. Industrial waste heat: the available potential According to estimates from various European energy agencies, the total potential of industrial waste heat in the EU stands at around 300–400 TWh/year. Nearly half corresponds to temperatures above 100 °C. Where recoverable waste heat can be found Combustion gases (furnaces, boilers, turbines): typical temperature 200–600 °C. Process steam and condensate: temperature 100–200 °C. Compressor and machinery cooling water: temperature 30–90 °C. Hot process effluents: variable. The energy audit as a starting point Inventory of available waste heat flows: flow rate, temperature, gas composition, intermittency. Estimate of recoverable thermal power and associated annual energy. Study of potential uses for recovered heat. Techno-economic analysis with estimated investment, annual fuel savings and ROI. Identification of applicable support schemes and available grants in the country of operation. Difference between an indicative estimate and a formal audit A simplified estimate is useful as an initial screening. For EED 2023/1791 obligations, a formal energy audit by a qualified independent expert is required, compliant with EN ISO 50002 or EN 16247-1. Legal notice, limitation of liability and regulatory referencesStrictly informational and general guidance article. Regulatory references have been compiled from official published sources (OJ EU, EUR-Lex). BOIXAC Tech SL accepts no liability arising from the … Read more

Energy saving and CO₂ reduction calculator for industrial heat recovery

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    Technical blog › Energy efficiency Energy saving and CO₂ reduction calculator for industrial heat recovery Indicative tool to estimate recoverable thermal power, fuel savings and approximate CO₂ emission reduction from installing a heat recovery heat exchanger. Enter your process data and get an estimate in seconds. BOIXAC Tech SL GHG Protocol reference factors · User-editable values Indicative tool — estimative results with no regulatory value Important notice — please read before using this tool This tool is strictly indicative. Results are simplified estimates based on the thermal balance Q = ṁ · cp · ΔT · η and reference emission factors. They have no technical, legal or regulatory validity whatsoever. BOIXAC Tech SL accepts no liability arising from the use of this tool or its results for any purpose. 🌍 1 · Select territory — Select a territory —International (generic) 📊 Reference emission factors — user-editable ↺ Restore The values shown are GHG Protocol generic references. You may edit them to match the actual conditions of your process or energy supply contract. Click “Restore” to revert to the original values. Fuel Emission factor Reference source These are generic GHG Protocol reference values. Apply the official emission factors published by the competent authority in your country for any formal purpose. 2 · Process data Hot fluid or gas flow rate kg/hm³/h (gas)kg/s Mass flow rate of the hot stream available for heat recovery. Typical values: industrial furnaces 2,000–50,000 kg/h; steam boilers 1,000–20,000 kg/h; cogeneration engines 500–5,000 kg/h. Inlet temperature°CTemperature at the process outlet, before the heat exchanger. Target outlet temperature°CMinimum outlet temperature of the hot fluid. For combustion gases, never go below the acid dew point (typically 120–150 °C for natural gas, 140–160 °C for diesel). Specific heatkJ/(kg·K)Dry air ≈ 1.006 · Combustion gases ≈ 1.05–1.15 · Steam ≈ 2.0 · Water ≈ 4.18 kJ/(kg·K) Annual operating hoursh/yearContinuous operation: 8,760 h/year. 2-shift, 5 days: ≈ 4,000 h/year. Estimated heat exchanger efficiency%Typical industrial heat recovery: 65–85%. Default conservative value: 75%. 3 · Fuel Fuel replaced — Select the fuel. The emission factor is taken from the table above. Fuel price€/kWhAdapt the price to your actual contract. Boiler / heat generator efficiency%Conventional boiler: 85–90%. Condensing: 95–105%. Steam: 80–88%. Reference CO₂ price (optional)€/t CO₂Indicative carbon market price. Set to 0 to ignore this factor. 4 · Investment (optional — for ROI) Estimated equipment and installation cost€Includes equipment, installation and commissioning. Leave blank to skip ROI. Note: ROI may appear very short (months) for high flow-rate, high ΔT processes — always verify against a real quotation and actual process conditions. Additional annual maintenance cost€/yearCleaning, inspection, spare parts. Typically 0.5–2% of equipment cost per year. Calculate estimate ↺ Reset Indicative estimate Calculation detail (estimative) Parameter Estimative value Limitation of results These results are purely estimative. They have been obtained using the simplified thermal balance Q = ṁ · cp · ΔT · η, without considering radiation or pipe conduction losses, seasonal load variations or the acid dew point. They do not represent the actual behaviour of any specific equipment or installation. For a rigorous technical estimate, please contact the BOIXAC technical office. Legal notice and limitation of liability Strictly informative and indicative tool. Results have no technical, legal or regulatory validity and may not be used for any official, contractual or regulatory purpose. The emission factors shown are indicative reference values. BOIXAC Tech SL accepts no liability for decisions taken based on the results of this tool. Do you need a real technical estimate for your process? The BOIXAC technical office analyses the actual conditions of your process and proposes the optimal heat recovery solution with a detailed thermal balance. Contact our technical office

Heat exchanger parameter glossary and unit converter

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    Technical tools › Heat exchangers Heat exchanger parameter glossary and unit converter Select any parameter from a heat exchanger calculation datasheet to view its definition and convert the value between the most common industrial units. Parameter: — Select a parameter —Thermal capacityHeat transfer surface areaOverall heat transfer coefficient (U)Log Mean Temperature Difference (LMTD) Volumetric air flow rateMass air flow rateFace velocity on the coilInlet air densityInlet air temperatureOutlet air temperatureInlet relative humidityOutlet relative humiditySpecific humidityInlet air enthalpyOutlet air enthalpyPressure drop — air sideFouling factor — air sidePartial heat transfer coefficient — air side Volumetric fluid flow rateMass fluid flow rateFluid velocityInlet fluid temperatureOutlet fluid temperatureTotal pressure drop — fluid sidePartial heat transfer coefficient — fluid sideFouling factor — fluid side Number of rowsNumber of tubes per rowCoil lengthFin pitchNumber of circuitsTube outer diameterTube inner diameterFin thicknessCoil internal volumeAtmospheric pressure / Altitude 🔍 Select a parameter from the dropdown to view its definition and the unit converter. Note on conversions Converted values are obtained by applying international standard conversion factors. Temperature conversions (°C, °F, K) include the origin offset where applicable. Results have up to 4 significant figures. This tool is for guidance only; for engineering calculations, always verify against applicable reference standards. Do you need a detailed calculation for your process? The BOIXAC technical office analyses the actual conditions of your process and proposes the optimal heat exchanger solution. Contact our technical office

Pillow plate for fermentation and thermal control in wineries and breweries

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Pillow plate heat exchangers in breweries and wineries: fermentation cooling and tank temperature control | BOIXAC Technical blog · Food industry › Breweries and wineries Pillow plate heat exchangers in breweries and wineries: fermentation cooling and tank thermal control Why dimple plate technology outperforms conventional jackets for fermentation tank cooling: heat transfer coefficient analysis, CIP cleaning and design criteria for beer and wine production. BOIXAC · Technical OfficeUpdated: 2026Reading: ~11 min Note on the scope of this article This article is of a general technical and informational nature. Heat transfer coefficient values, temperature ranges and design criteria given are indicative; the definitive sizing of a pillow plate heat exchanger for a specific application requires analysis of the actual process conditions by qualified engineers. BOIXAC assumes no liability for decisions taken on the basis of this article. Temperature control during fermentation is one of the technical parameters with the greatest influence on the organoleptic profile of the final product in breweries and wineries. The difference between a fermentation proceeding at 12 °C and one that peaks at 18 °C may be the difference between a clean product and one with undesirable ester and fusel alcohol profiles. Pillow plate technology — also known as dimple plate — has progressively replaced half-pipe jackets and conventional annular jackets on next-generation stainless steel fermentation vessels, thanks to thermal, hygienic and constructional advantages that become especially evident in tank volumes exceeding 5,000 litres. 1. Operating principle of the pillow plate (dimple plate) A pillow plate is a heat exchanger formed by two stainless steel sheets joined at their perimeter and by a regular matrix of resistance spot welds, creating an internal labyrinthine cavity with a very narrow cross-section. When a refrigerant fluid (typically aqueous glycol) circulates through this cavity, the dimple geometry induces local turbulent flow — even at low volumetric flow rates — maximising the internal convection coefficient. The outer sheet of the pillow plate is welded directly to the surface of the fermentation vessel, so that the tank wall simultaneously serves as the load-bearing structure and the heat transfer surface. The embossed geometry of the dimples distributes the refrigerant pressure uniformly across the entire plate surface, allowing operation at relatively high internal pressures (up to 10–15 bar depending on design and sheet thickness) with minimal material thickness. 2. Technical comparison: pillow plate vs. conventional jackets Parameter Pillow plate (dimple plate) Half-pipe jacket Conventional annular jacket Internal convective coefficient (hi) High: dimple geometry induces local turbulence. Typical values: 3,000–8,000 W/m²·K. Moderate-high: tubular flow. 2,000–5,000 W/m²·K. Low-moderate: wide annular flow, often laminar. 500–2,000 W/m²·K. Cooling distribution across tank surface Excellent: continuous, uniform coverage of all covered surface. Good along the pipe length; zones between pipes lack direct contact. Variable: risk of dead zones in large-section annular circuit. Refrigerant fluid volume in circuit Very low: narrow flow passage (typically 3–6 mm). Reduced glycol volume in circuit. Moderate. High: large annular cross-section. Thermal response time Very fast: low fluid volume, reduced thermal inertia. Rapid control system response. Fast-moderate. Slow: large fluid volume, high thermal inertia. Slow response to setpoint changes. Cleanability — product side Excellent: smooth external surface in contact with product, suitable for CIP cleaning. Good. Good. 3. Specific applications in breweries and wineries 3.1. Fermentation vessel cooling in brewing In bottom-fermentation (lager) beer production, temperature control is especially critical because the yeast working window (typically 8–14 °C for standard lager strains) is narrow and the heat generated by alcoholic fermentation is significant: approximately 2.3 kJ are released per gram of fermented sugar. In a 50-hl fermenter with 12 °P wort, the cooling duty required at peak fermentation activity can be between 3 and 8 kW depending on the fermentation rate. Pillow plates welded to the cylindrical tank wall (and, in some designs, to the cone) allow this heat extraction to be distributed homogeneously, avoiding radial temperature gradients that could create localised sub-cooling zones where yeast activity is inhibited or premature precipitation occurs. The fast response of the system — due to the low refrigerant circuit volume — facilitates the use of PID control systems that maintain temperature setpoints within ±0.5 °C, difficult to achieve with high-inertia conventional jackets. 3.2. Must temperature control in wine fermentation In white and rosé winemaking, fermentation temperature control (typically between 12 and 18 °C) is critical for preserving volatile varietal aromas that are lost through volatilisation if temperatures are exceeded. Pillow plates on AISI 304 or 316L stainless steel tanks allow low fermentation temperatures to be reached and maintained with modest refrigeration systems. The ability to reach temperatures close to 0 °C uniformly and in a controlled manner — the so-called cold tartrate stabilisation — is an application that highlights the thermal performance of pillow plate technology over less efficient alternatives. 3.3. Craft breweries and microbreweries In craft breweries with smaller fermenters (100–2,000 litres), pillow plate technology offers additional advantages due to its compatibility with relatively small glycol systems and the ease of integration on cylindroconical stainless steel tanks. The typical configuration consists of one or two independent pillow plate zones (cylindrical and conical sections) connected to a glycol circuit with independent zone control valves, allowing programmable temperature profiles throughout fermentation. 4. Pillow plate sizing criteria for fermentation vessels Peak fermentation thermal duty (Qmax): estimated from fermentation rate, wort concentration (°P or °Brix) and tank volume. In beer production, indicative reference values range from 50 to 150 W per hl of fermenter capacity at peak activity, depending on the recipe and yeast used. Available temperature differential (ΔT): difference between fermenting product temperature and refrigerant inlet temperature to the plate. Minimum refrigerant temperature: in aqueous glycol circuits, glycol temperatures of -2 to -5 °C are generally sufficient for most standard fermentation applications; lower temperatures are used for tartrate stabilisation. Tank surface coverage: the proportion of the total tank surface covered with pillow plate (typically 40–70 % of the lateral surface) must be sufficient to ensure cooling uniformity and avoid vertical temperature gradients in the product. Refrigerant circuit working pressure: pillow plate … Read more

Economizer sizing for OEM industrial boilers

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Economiser sizing for industrial boiler OEM manufacturers | BOIXAC Technical blog · OEM integration › Industrial economisers Economiser sizing for industrial boiler OEM manufacturers Technical criteria for thermal sizing, mechanical integration and regulatory documentation for boiler manufacturers incorporating economisers as an integral component of their equipment. BOIXAC · Technical OfficeUpdated: 2026Reading: ~10 min Note on the scope of this article This text is exclusively technical and informational in nature. It does not replace the specific analysis of a concrete project by qualified engineers. The values and ranges given are indicative; the definitive sizing of any economiser requires a detailed study of the actual process conditions, the regulatory classification of the equipment and, where applicable, the intervention of a Notified Body. BOIXAC assumes no liability for decisions taken on the basis of this article. For an industrial boiler OEM manufacturer, the economiser is not an optional accessory: it is a critical component that defines the overall efficiency of the assembly, conditions the structural design of the boiler and, to a large extent, determines the regulatory category of the final equipment. Integrating it correctly demands going well beyond a simple calculation of the heat transfer surface area. 1. Function and positioning of the economiser in the boiler assembly An economiser is a gas-to-liquid heat exchanger located in the final section of the flue gas circuit, typically between the last boiler pass and the stack. Its function is to recover the enthalpy contained in the outlet gases — which in conventional natural gas boilers ranges between 150 and 280 °C — to preheat feedwater before it enters the steam generator, or to heat a secondary service fluid. The thermal gain is directly proportional to the temperature drop of the flue gases across the economiser. As an indicative reference, every 20 °C drop in flue gas temperature in a natural gas boiler represents an approximate 1 % improvement in the overall plant efficiency. In boilers burning diesel, heavy fuel oil or biomass the margins may be greater, but the risk of acid condensation on the tubes demands careful analysis of the acid dew point, particularly when the gases contain SO₂. Key term: acid dew point In flue gases containing sulphur dioxide (SO₂), present in sulphur-bearing fuels such as heavy fuel oil or certain biogases, the acid dew point occurs at temperatures significantly higher than the water dew point. Operating below this point causes condensation of sulphurous and sulphuric acid on tube surfaces, severely accelerating corrosion. Economiser sizing must ensure that tube wall temperatures always remain above this critical threshold, the determination of which depends on the sulphur content of the fuel and the excess air used. 2. Thermal sizing variables Thermal sizing of an economiser is based on forced convection heat transfer between the flue gases and the fluid to be preheated, separated by the tube wall. The variables the OEM engineer must define to initiate the sizing process are as follows: Variable Description and OEM considerations Flue gas mass flow rate (ṁg) Expressed in kg/h or Nm³/h. Must correspond to the rated boiler output and, if required, to partial load conditions (50 %, 75 %). Flow variation affects the external convection coefficient on the tubes. Gas inlet temperature (Tg,in) Temperature of the gases at the economiser inlet, i.e. at the outlet of the last boiler pass. May vary with load conditions. Gas outlet temperature (Tg,out) Target gas temperature at the economiser outlet. Constrained by the minimum allowable temperature to avoid condensation (acid dew point or water dew point). Fluid flow rate and inlet temperature Feedwater or service fluid flow rate and its inlet temperature. In steam boilers, feedwater typically arrives between 60 and 105 °C from the deaerator. Fluid outlet temperature (Tf,out) Target fluid temperature at the outlet. Must maintain an adequate margin below the saturation temperature at working pressure to avoid local boiling in the tubes. Gas composition Content of CO₂, H₂O, SO₂, NOₓ, ash and particulates. Determines the corrosion risk, the fouling factor and the tube material selection. Allowable pressure drop (ΔP) Pressure drop limitation on both the gas and fluid sides, imposed by the overall boiler design and available fan capacity. Fundamental sizing equation Q = U · A · ΔTlm Where Q is the thermal duty (W), U is the overall heat transfer coefficient (W/m²·K), A is the heat transfer area (m²) and ΔTlm is the log mean temperature difference between the two fluid streams. The value of U results from the detailed calculation of the interior and exterior convective coefficients, the wall resistance and the fouling factors on each side, and is highly dependent on the specific geometry of the economiser. 3. Economiser construction types for OEM integration Type Characteristics for OEM integration Preferred application Helically finned tubes Maximum surface density per unit volume. High U coefficient with clean gases. Prone to progressive fouling if gases contain fine particles or ash. Natural gas or LPG boilers. Clean gases without particulates. Continuous (plate) fins High heat transfer area. Compact design. Air-blowing or sootblower cleaning integrable. Diesel-fired boilers. Gases with moderate particulate content. Bare tubes (no fins) Lower surface density but maximum robustness against gases with high abrasive particle content, fly ash or corrosive condensates. Easy mechanical cleaning. Biomass boilers, heavy fuel oil, process gases with particulates. Gases with elevated SO₂. Condensing economiser Operates below the water dew point, recovering the latent heat of condensation. Requires corrosion-resistant materials (316L stainless steel) and management of the generated condensate. High-efficiency natural gas boilers. Projects targeting efficiency ≥ 107 % (LHV basis). 4. Mechanical integration into the boiler assembly 4.1. Differential thermal expansion Economiser tubes and the casing undergo thermal expansions of different magnitudes and rates during boiler start-up and shutdown cycles. Inadequate management of thermal stresses can cause fatigue at welded joints or irreversible deformation of the headers. Common solutions include floating header designs, expansion compensators in the connecting pipework and defined maximum heating rates (heat-up rates) in the operating procedures. 4.2. Fluid connections Water circuit connections must be compatible with … Read more

Heat exchanger for lime and calcium carbonate industrial minerals plant

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Heat exchangers in calcination plants: lime, calcium carbonate and industrial minerals | BOIXAC Technical blog · Minerals industry › Calcination and industrial minerals Heat exchangers in calcination plants: lime, calcium carbonate and industrial process minerals Technical criteria for heat recovery from rotary kiln flue gases with abrasive dust, high temperatures and CO₂ content: typology selection, materials and cleaning strategies. BOIXAC · Technical OfficeUpdated: 2026Reading: ~11 min Note on the scope of this article This article is of a general technical and informational nature. The temperature values, gas compositions and material ranges indicated are orientative and are based on process references from the industrial minerals industry. Definitive sizing and equipment selection for a specific application requires a detailed analysis of the actual plant conditions by qualified engineers. BOIXAC assumes no liability for decisions taken on the basis of this article. Plants producing quicklime, hydrated lime, precipitated calcium carbonate and other industrial process minerals operate with rotary kilns that generate considerable volumes of combustion gases at temperatures typically between 300 and 600 °C at the preheater outlet. Recovering this residual thermal energy represents one of the best cost-benefit energy efficiency improvements available in the sector, but the nature of the gases — with high concentrations of abrasive dust, significant CO₂ content and, occasionally, sulphur compounds — demands very specific selection and technical design. 1. Production context: rotary kiln and calcination gases The calcination of calcite (CaCO₃) to produce quicklime (CaO) is an endothermic reaction requiring process temperatures between 900 and 1 100 °C inside the kiln. The resulting combustion gases — enriched with CO₂ released by the mineral’s decarbonation — leave the kiln at temperatures that depend on the kiln type and preheating system used: Kiln type / process Typical flue gas temperature at outlet Particularities for the heat exchanger Long rotary kiln without preheater 350–600 °C High fine lime dust load (CaO/CaCO₃). High abrasivity. Large gas flow rate. Rotary kiln with cyclone preheater 200–350 °C Dust partially separated in cyclones. More moderate temperature. Risk of condensation if excessively cooled. Shaft kiln 150–280 °C Gases with very high CO₂ (up to 30–40 % v/v). Moderate dust. High CO₂ concentration may influence the selection of the receiving fluid. Rotary kiln for dolomite / magnesite 400–700 °C Dust containing MgO and CaO components. Very high abrasivity. High gas temperature. 2. Degradation mechanisms specific to this industry 2.1. Mechanical abrasion by particle impact CaO, CaCO₃ or dolomite particles in kiln gases present a Mohs hardness of 3 to 5 and a particle size distribution that, despite passage through pre-collection cyclones, includes fractions up to 200–500 µm. When they impact tube surfaces at typical gas velocities (8–15 m/s), they cause erosive wear that is particularly severe at fin edges in finned tubes and at bends in gas direction-change zones. The erosion rate is proportional to particle concentration, particle hardness, the third or fourth power of the impact velocity and the cosine of the impact angle. Minimising it requires design action: reducing gas velocities in the exchanger ducts (typically below 10 m/s in heavily abrasive applications), avoiding geometries that generate direct impingement on surfaces and selecting high erosion-resistant materials for maximum exposure points. 2.2. Fouling and blockage by dust deposition CaO particles progressively depositing on tube and fin surfaces form an insulating layer that reduces the overall heat transfer coefficient (U) proportionally to its thickness. Under high dust-loading conditions without active cleaning, accumulation can reduce the economiser’s thermal performance by 30–50 % within weeks or months. Dry CaO or CaCO₃ dust deposits are generally relatively soft and friable, and can be removed by mechanical vibration, steam blowing (sootblowing) or rapping, provided the equipment design includes adequate access and cleaning systems. Specific risk: hydration of quicklime in the presence of moisture Under conditions of elevated moisture in the gases or during start-up and shutdown cycles with partially cooled gases, CaO (quicklime) particles can hydrate by reacting with moisture in the gases to form Ca(OH)₂. This exothermic reaction can generate hard and expansive deposits on tube surfaces, significantly more difficult to remove than dry dust deposits. Exchanger design and management of minimum wall temperatures during start-ups and shutdowns must account for this risk, especially in kilns processing quicklime without an efficient dust pre-collection system. 3. Heat exchanger typology selection Typology Advantages for calcination gases Limitations and risks Recommended application Bare tubes (no fins) Maximum abrasion resistance. No preferential wear point due to fin geometry. Direct mechanical cleaning. Lower tendency for dust retention. Lower surface density per unit volume than finned tubes. Gases with high dust loading (>5 g/Nm³) and elevated abrasivity. Helically finned tubes High surface density. Good U coefficient. Compactness. Dust accumulation in inter-fin channels. Difficult mechanical cleaning. Risk of irreversible blockage. Clean gases (<1–2 g/Nm³). Not recommended for calcination gases without efficient post-collection. Continuous (plate) fins Better cleaning access than helical fins. Dust accumulation in channels. Moderate dust loading (1–5 g/Nm³). Post-collection cyclones of good efficiency. 4. Material selection for abrasive-corrosive environments Material Abrasion resistance Wall temperature limit Remarks Carbon steel S235/P235GH Moderate ~450 °C Suitable for moderate temperature zones with reasonably clean gases after pre-collection. Susceptible to SO₂ near the acid dew point. Cr-Mo low-alloy steel (13CrMo4-5, P91) Good ~550 °C Improved high-temperature oxidation and erosion resistance compared to carbon steel. Stainless steel AISI 310S Good–very good ~1 050 °C Excellent high-temperature oxidation resistance. For the first tube rows exposed to the hottest gases (>500 °C). High wear-resistant cast iron (Ni-Hard, white iron) Excellent ~400 °C Maximum impact abrasion resistance. Used for deflectors and shell liners. Brittleness limits use; not suitable for pressure-bearing tubes. Nickel-base alloy (Inconel 625, Alloy 800H) Very good ~1 000 °C For extreme conditions: very high temperature combined with corrosive gas. High cost; application justified on a case-by-case basis. Common strategy: material zoning In heat exchangers for calcination gases, it is common practice to apply a material zoning strategy: the first tube rows, exposed to the hottest gases and highest particle velocities, are built with more resistant materials (310S stainless steel … Read more

Heat exchanger for fish meal rendering plant

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Heat exchangers in rendering and fish meal plants: design guide for EPC engineers | BOIXAC Technical blog · Food industry › Rendering and fish meal Heat exchangers in rendering and fish meal plants: design guide for EPC engineers Thermal sizing criteria, material selection and equipment specification for engineering firms designing animal by-product rendering plants and fish meal and fish oil processing facilities. BOIXAC · Technical OfficeUpdated: 2026Reading: ~12 min Note on the scope of this article This article is technical and informational in nature, intended for engineering professionals. Process data, coefficients and temperature ranges given are industry reference values; definitive values for a specific project must be determined from actual process data and require the analysis of specialist teams. BOIXAC assumes no liability for design decisions taken on the basis of this article. Animal by-product rendering plants and fish meal and fish oil processing facilities present some of the most demanding thermal and mechanical challenges in the food industry: proteinaceous fluids with a high tendency to fouling through denaturation, animal fats with highly temperature-dependent viscosity, condensable vapours with high volatile organic compound content, and strict cleaning and hygiene requirements. For an EPC engineering firm designing or upgrading one of these facilities, the correct specification of heat exchangers is a critical decision affecting process efficiency, operational availability and maintenance costs throughout the plant’s service life. 1. The rendering process and its critical thermal stages Process stage Heat exchanger function Typical conditions Raw material preheating Heating the raw material before entry into the continuous or batch cooker, to reduce viscosity and facilitate phase separation. Fluid: aqueous fraction + fat. T: 40–80 °C. Suspended solids. Continuous cooking (cooker) Maintaining cooking temperature. Heat transfer from steam to the animal slurry. Cooking T: 120–140 °C. Steam as heating medium. High viscosity. Stick water evaporation Concentration of the aqueous phase (stick water) by evaporation to recover soluble proteins and reduce effluent volume. Fluid: proteinaceous aqueous phase. Evaporation T: 60–90 °C (vacuum). High fouling tendency. Animal fat (tallow) cooling Cooling molten tallow to storage or dispatch temperature. Heat recovery to service fluid. Fluid: animal fat. Inlet T: 80–100 °C. Outlet T: 30–45 °C. Viscosity increasing as it cools. Cooker and dryer vapour condensation Condensation of organic vapours generated during cooking and drying. Saturated vapour with VOCs and H₂S. Corrosive condensates. Resistant materials required. Dryer exhaust gas heat recovery Heat recovery from dryer exhaust gases to preheat inlet air or service fluid. High-moisture gases with fine meal particles. Condensation fouling risk. 2. Protein denaturation fouling: the central design challenge Strongly wall-temperature dependent: deposition rate accelerates exponentially when the wall temperature exceeds the denaturation temperature of the proteins present. In rendering stick water, critical temperatures for the main protein groups range between 70 and 90 °C. Keeping wall temperatures below these thresholds is the key to fouling control. Barely reversible by conventional chemical cleaning: layers of denatured and carbonised protein on tube surfaces require aggressive CIP procedures (high-temperature NaOH, enzymatic) or direct mechanical cleaning. The design must guarantee full access to all heat transfer surfaces for cleaning. Progressive and cumulative: sizing must incorporate an adequate fouling factor for proteinaceous fluids, significantly higher than conventional TEMA values for clean fluids. Fouling factor for proteinaceous fluids — design consideration For rendering and fish meal proteinaceous fluids, TEMA standard fouling factor values for “industrial liquids” typically underestimate actual long-term fouling resistance. Conservative sizing of a heat exchanger for proteinaceous stick water should incorporate fouling factors specific to high-concentration biological fluids, which can be 2 to 5 times higher than standard TEMA values for clean fluids. The precise determination of the fouling factor for a specific fluid is critical design data that should be obtained from prior experience with similar fluids or from pilot tests. 3. Recommended heat exchanger types by process stage Stage / Fluid Recommended type Technical justification Proteinaceous stick water — heating/evaporation Fully removable shell-and-tube or concentric tube heat exchanger. Protein fouling demands direct mechanical cleaning. Full removal of the tube bundle is essential. Plate heat exchangers are unsuitable for fluids with solids or severe fouling tendency. Animal fat (tallow) — cooling Concentric tube (coaxial) or large-bore shell-and-tube heat exchanger. Increasing tallow viscosity on cooling demands wide flow passages to avoid excessive pressure drop and facilitate controlled laminar flow. Cooker organic vapour condensation Shell-and-tube heat exchanger with corrosion-resistant materials. Vertical orientation preferred. Cooker condensates contain fatty acids, H₂S and organic compounds. 316L stainless steel minimum. Vertical orientation facilitates condensate drainage. Dryer exhaust gas heat recovery Bare tube gas-to-air or gas-to-liquid heat exchanger with sootblower or air-blow cleaning. Dryer exhaust gases carry fine meal particles. Bare tubes facilitate cleaning. Fish oil preheating Plate or shell-and-tube heat exchanger depending on fluid solids content. Clean, filtered fish oil is suitable for plate heat exchangers. If it contains solids or protein fines, opt for a fully removable shell-and-tube unit. 4. Material selection for rendering and fish meal fluids Material Application in rendering / fish meal Specific considerations AISI 304 (1.4301) Surfaces in contact with animal fats and low-aggressivity proteinaceous fluids. Susceptible to pitting corrosion in the presence of chlorides. Cl⁻ concentrations above ~200 ppm may require 316L. AISI 316L (1.4404) Surfaces in contact with cooker vapour condensates, fish stick water (frequently with chloride content). Better chloride resistance than 304. Recommended as the minimum standard for any fluid in direct contact in fish meal plants due to the natural salinity of fish. Duplex 2205 (1.4462) Zones of high chloride concentration and temperature. Excellent resistance to chlorides and stress corrosion cracking. Higher yield strength than 316L. Titanium Gr.2 Condensers in contact with highly aggressive marine effluents or fluids with very high chloride content. Exceptional marine corrosion resistance. Recommended when 316L or Duplex cannot guarantee the desired service life. 5. Specific design criteria for EPC engineers Thermal and hydraulic data sheet: mass flow rates, inlet and outlet temperatures, working and test pressures, maximum allowable pressure drops on both sides. Fluid composition and properties: dynamic viscosity as a function of temperature (η-T curve), density, specific heat, thermal … Read more

ATEX: Explosive atmospheres in industrial installations

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ATEX: Equipment Selection in Explosive Atmospheres for Chemical, Pharmaceutical and Food Industries | BOIXAC Technical guide › Industrial regulation ATEX: Zone Classification, Equipment Categories and Marking for Explosive Atmospheres in Industrial Installations Technical reference guide on ATEX directives 2014/34/EU (equipment) and 1999/92/EC (worker safety): Ex zones, equipment categories, gas groups, temperature classes and implications for manufacturers and operators of industrial installations with explosion risk. BOIXAC Tech SLUpdated: 2026Reading time: ~9 min Safety warning and limitation of liability — Mandatory reading This page is intended for general information and reference purposes only. ATEX regulations directly affect the safety of people and installations. No content in this guide constitutes technical, safety engineering or legal advice. Zone classification, equipment selection and the preparation of the Explosion Protection Document (EPD) require the involvement of a qualified technical professional with accredited experience in explosive atmosphere safety. BOIXAC Tech SL assumes no liability arising from the use of this information. For any real installation, consult an accredited notified body or an engineer specialised in ATEX. Explosive atmospheres represent one of the industrial hazards with the most potentially severe consequences. For manufacturers and operators of installations in sectors such as chemicals, pharmaceuticals, food, oil and gas or waste treatment, understanding the ATEX framework is not optional: it is a legal requirement and an unavoidable responsibility. 1. The two ATEX directives: manufacturers and operators ATEX 2014/34/EU — Equipment directive (manufacturers) Applies to manufacturers of equipment, protective systems, control devices and components intended for use in potentially explosive atmospheres. Establishes design, manufacturing, conformity assessment and CE marking requirements for Ex equipment. Replaced Directive 94/9/EC from 20 April 2016. ATEX 1999/92/EC — Workplace directive (operators) Applies to operators of installations where explosive atmospheres may be present. Establishes the obligation to classify Ex zones, prepare the Explosion Protection Document (EPD), select equipment appropriate for each zone and ensure worker training. Intersection with PED 2014/68/EU and Machinery Directive 2006/42/EC When a pressure equipment item is installed in an ATEX zone, PED (pressure risk), Machinery Directive (if part of an actuated assembly) and ATEX directives (ignition risk) apply simultaneously. When in doubt, the precautionary principle requires applying the most restrictive requirement. 2. Zone classification: the starting point Gas / Vapour / Mist (ATEX 1999/92)Zone 0Permanent hazardExplosive atmosphere present continuously, for long periods or frequently. Requires Category 1G equipment. Gas / Vapour / Mist (ATEX 1999/92)Zone 1Occasional hazardExplosive atmosphere that may occasionally form during normal operation. Requires Category 1G or 2G equipment. Gas / Vapour / Mist (ATEX 1999/92)Zone 2Unlikely hazardExplosive atmosphere not normally present and, if it does occur, only for a brief period. Requires Category 1G, 2G or 3G equipment. Combustible dust (ATEX 1999/92)Zone 20Permanent hazardCombustible dust cloud present continuously or frequently. Requires Category 1D equipment. Combustible dust (ATEX 1999/92)Zone 21Occasional hazardCombustible dust cloud that may occasionally form during normal operation. Requires Category 1D or 2D equipment. Combustible dust (ATEX 1999/92)Zone 22Unlikely hazardCombustible dust cloud not normally present or, if it occurs, only for a brief period. Requires Category 1D, 2D or 3D equipment. Frequent critical error — Zone classification is not optional A common shortcoming in existing installations is the absence of formal zone classification or its inadequate updating when production processes change. In the event of an accident, lack of classification and an up-to-date EPD results in direct criminal and civil liability for those responsible for the installation, regardless of whether the installed equipment was ATEX-certified. 3. Equipment categories, groups and temperature classes Category Group Suitable zones Max. permitted zone Main industrial applications Cat. 1G II Zone 0, 1, 2 Gas/vapour · Zone 0 Refineries, chemical plants, solvent storage. EPL level Ga — very high protection. Cat. 2G II Zone 1, 2 Gas/vapour · Zone 1 Chemical and pharmaceutical plants, flammable liquid loading/unloading areas. EPL level Gb. Cat. 3G II Zone 2 Gas/vapour · Zone 2 Food industry, chemical plant perimeter areas, flammable product warehouses. EPL level Gc. Cat. 1D III Zone 20, 21, 22 Dust · Zone 20 Flour, sugar and high-combustibility metal dust processing facilities. EPL level Da. Cat. 2D III Zone 21, 22 Dust · Zone 21 Food industry (spray areas), pharmaceutical, biomass processing. EPL level Db. Cat. 3D III Zone 22 Dust · Zone 22 Perimeter areas of combustible dust installations, silos, warehouses. EPL level Dc. Gas groups and subgroups: IIA, IIB, IIC Group II (surface) equipment is subdivided according to the minimum ignition energy of the gas or vapour present: IIA (propane, butane — high minimum ignition energy), IIB (ethylene — intermediate energy) and IIC (hydrogen, acetylene — very low minimum ignition energy, maximum risk). IIB-certified equipment is suitable for IIA and IIB gases, but not for IIC. Incorrect subgroup selection is one of the most common causes of non-conformity in ATEX audits. Maximum surface temperature classes (T1–T6) The maximum surface temperature of the equipment must be below the ignition temperature of the gas or vapour present, with a safety margin. Classes range from T1 (450°C max.) to T6 (85°C max.). For example, a T3 device (200°C max.) is suitable for gases with an ignition temperature above 200°C (acetone: 465°C ✓ / hydrogen sulphide: 270°C ✓ / diethyl ether: 160°C ✗). 4. The ATEX marking: how to read it ⟨Ex⟩ II 2G Ex d IIB T3 Gb ⟨Ex⟩ATEX markingIIEquipment group (surface)2GCategory / gas environmentEx dProtection type (flameproof enclosure)IIBGas subgroupT3Temperature class (200°C max)GbEPL level Most common protection types: Ex d (flameproof enclosure), Ex e (increased safety), Ex ia/ib (intrinsic safety), Ex p (pressurised enclosure), Ex n (non-sparking equipment, zone 2), Ex t (dust ignition protection by enclosure). The ATEX certificate is not permanent: any unauthorised modification to the equipment — including replacement of components with non-certified parts — invalidates the certificate and protection category. Maintenance in ATEX zones: maintenance operations must be carried out by trained and qualified personnel, with procedures appropriate for the classified zone. All interventions must be documented. 5. The Explosion Protection Document (EPD) Minimum EPD content: identification and classification of all Ex zones, inventory of installed equipment with verification of suitability, … Read more

Machine Directive 2006/42/CE industrial boiler manufacturer

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Machinery Directive 2006/42/EC for Boiler and Thermal Equipment Manufacturers | BOIXAC Technical guide › Industrial regulation Machinery Directive 2006/42/EC: Technical Guide for Boiler and Industrial Thermal Equipment Manufacturers Analysis of the essential health and safety requirements, conformity assessment and CE marking for OEM manufacturers integrating thermal components —economisers, heat exchangers, heat recovery units— into boilers and industrial machinery assemblies. BOIXAC Tech SLUpdated: 2026Reading time: ~8 min Note on the scope of this guide This page is intended for general information and reference purposes only. It does not constitute legal or engineering advice. The interpretation and application of Directive 2006/42/EC may vary depending on the specific product, the country of commercialisation and the individual circumstances of each manufacturer. BOIXAC Tech SL does not provide regulatory or legal advisory services and assumes no liability arising from the use of this information. For any conformity decision, consult an accredited notified body or a legal adviser specialised in product law. For OEM manufacturers of boilers, steam generators and industrial thermal equipment, the Machinery Directive 2006/42/EC is the legal framework that governs the conditions for placing products on the European market. Integrating third-party components —economisers, heat exchangers, heat recovery units— into a machinery assembly is not a minor technical detail: it determines the risk assessment scope, the technical documentation and the liability of the integrating manufacturer. 1. Scope: when does the Machinery Directive apply? Directive 2006/42/EC applies to machinery, defined as an assembly of linked parts or components, at least one of which moves, fitted with an appropriate actuating system. Industrial boilers with burners, automatic control systems and electrically or pneumatically actuated auxiliary components clearly fall within the scope of the directive. 🔥Industrial boilers with burnerAssemblies with automatic ignition, safety controls and actuated auxiliary components. ⚙️Industrial steam generatorsEquipment with automatic pressure, level and temperature regulation systems. 🏭Thermal machinery assembliesInstallations where several machines are assembled to perform a combined function. ⛔Passive components without moving partsHeat exchangers, economisers and recuperators without their own actuating system generally fall outside the direct scope. Intersection with PED Directive 2014/68/EU When a boiler integrates pressure-bearing components, two directives apply simultaneously: 2006/42/EC for mechanical and operational risks of the assembly, and PED 2014/68/EU for pressure-specific risks. The integrating manufacturer is responsible for managing both conformity frameworks. 2. Essential Health and Safety Requirements (EHSR) General safety principles (§1.1): Machinery must be designed so that, when used as intended, it does not endanger persons. Safety by design takes priority over protective devices and operating instructions. Materials and products (§1.3.2): Materials must be suitable for the working fluids, temperatures and pressures involved. The integrating manufacturer must verify that the materials of external components meet the requirements of the boiler’s working fluid. Surface temperature (§1.5.5): Accessible hot surfaces capable of causing burns must be insulated or guarded. Especially relevant for high-temperature economisers. Design pressure and temperature (§1.5.7): Machinery must withstand the anticipated loads with adequate safety margins, including maximum operating pressures of hydraulic and steam circuits. Control systems and emergency stop (§1.2): The boiler must be equipped with control systems enabling safe shutdown in the event of a failure, including integrated components. Instructions (§1.7.4): The instruction manual must include information on all integrated components, including maintenance instructions for third-party supplied components. 3. Conformity assessment: applicable procedures Procedure Notified body Application for boilers Resulting documentation Annex VIIISelf-assessment Optional Machinery not listed in Annex IV. Standard boilers where the manufacturer applies harmonised standards (e.g. EN 12952, EN 12953). Internal technical file + CE Declaration of Conformity Annex IXEC type-examination Mandatory Annex IV machinery or where harmonised standards are not applied. High-power boilers or non-standard configurations. EC type-examination certificate + Technical file + CE Declaration Annex XFull quality assurance Mandatory Alternative to Annex IX for manufacturers with a quality system approved by a notified body. Suitable for series OEM manufacturers. Approved quality system + CE Declaration Harmonised standards: the safest route to conformity Applying harmonised standards published in the OJEU confers a presumption of conformity with the corresponding EHSR. For fire-tube boilers, the reference standard is EN 12953. For water-tube boilers, EN 12952. For general machinery risk assessment and reduction, EN ISO 12100 is the central reference. 4. Integrating manufacturer liability for third-party components Integrating manufacturer liability — critical point If a third-party component does not meet the technical requirements needed for safe integration, liability for the non-conformity of the assembly rests with the integrating manufacturer, not with the component supplier. Supplier qualification diligence is a conformity requirement, not merely a commercial best practice. PED Declaration of Conformity (where the component exceeds Article 4 thresholds of Directive 2014/68/EU), indicating risk category and conformity assessment module applied. Technical datasheet with design parameters: PS (maximum allowable pressure), TS (maximum design temperature), DN, materials of construction, design fluid and use limitations. Installation and maintenance instructions in the official language of the country of commercialisation. Material traceability for components in contact with pressurised or high-temperature fluids. 5. CE Marking and Declaration of Conformity The CE marking is not a quality mark or an external approval certificate: it is the manufacturer’s declaration that the product meets all applicable legal requirements. CE marking is mandatory for placing on the European market (EEA). Its absence constitutes a legal violation. The technical file must remain accessible to market surveillance authorities for a minimum of 10 years from the date of manufacture of the last unit. The CE Declaration of Conformity must accompany each unit and be available in the official language of the destination country. 6. New Machinery Regulation 2023/1230/EU: the upcoming change Regulation (EU) 2023/1230 is scheduled to replace Directive 2006/42/EC from 20 January 2027 (subject to confirmation in the Official Journal of the EU). The shift from directive to regulation means direct application without national transposition. Key changes introduced by Regulation 2023/1230 The most significant changes include: requirements for control systems incorporating artificial intelligence, new cybersecurity requirements for connected machinery, extended scope to partially completed machinery, and reinforced sustainability and ecodesign requirements. OEM manufacturers should begin reviewing their technical files well ahead of the … Read more

Pressure Equipment Directive PED 2014/68/UE

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Directive 2014/68/EU (PED): regulatory framework for pressure equipment | BOIXAC Technical blog › Regulations & certification Directive 2014/68/EU (PED):the regulatory framework for pressure equipment in the EU A technical guide to the scope of application, risk category classification and conformity assessment modules established by the Pressure Equipment Directive. BOIXAC Tech SL Updated: 2026 Reading time: ~8 min Note on the scope of this article This text is exclusively informational and educational in nature. It does not constitute legal, technical or engineering advice, and cannot under any circumstances replace the specific analysis carried out by a qualified professional on a particular piece of equipment. The correct application of Directive 2014/68/EU — including equipment classification, determination of the assessment module and obtaining CE marking — always requires the involvement of competent engineers and, for higher categories, a duly notified Notified Body. BOIXAC assumes no liability arising from decisions made based on the content of this article. Directive 2014/68/EU of the European Parliament and of the Council, of 15 May 2014, on the harmonisation of the laws of Member States relating to the making available on the market of pressure equipment — commonly known as the Pressure Equipment Directive or PED — is the European regulatory instrument governing the design, manufacture and conformity assessment of pressure equipment intended for the internal market. For any manufacturer or industrial user of pressure equipment — heat exchangers, vessels, boilers, process pipework and fittings — understanding the scope and logic of this Directive is a prerequisite for operating safely and in legal compliance within the European Economic Area. 1. Background and regulatory context Directive 2014/68/EU repealed and recast the previous Directive 97/23/EC, which ceased to apply on 19 July 2016. The recast did not substantially modify the essential safety requirements or the conformity assessment tables, but aligned the legislation with the New Legislative Framework (NLF) of the European Union — in particular Regulation (EU) No 765/2008 and Decision 768/2008 — introducing explicit obligations for all economic operators in the supply chain: manufacturers, authorised representatives, importers and distributors. Key regulatory reference Directive 2014/68/EU of the European Parliament and of the Council, of 15 May 2014 (OJ L 189, 27 June 2014, pp. 164–259). Full entry into force: 19 July 2016. 2. Scope of application The Directive applies to the design, manufacture and conformity assessment of pressure equipment and assemblies with a maximum allowable pressure (PS) greater than 0.5 bar gauge. Element Description under the Directive Vessels Housings designed and built to contain fluids under pressure, including shell-and-tube heat exchangers. Piping Piping components intended for the transport of fluids, including pipes, piping systems, fittings, expansion joints and hoses. Safety accessories Devices protecting against the exceedance of allowable limits: safety valves, pressure relief devices, automatic control systems, etc. Pressure accessories Devices with an operational function subject to pressure: non-return valves, regulators, steam traps, filters, etc. Assemblies Several items of pressure equipment assembled by a manufacturer to constitute an integrated functional installation. Notable exclusions The Directive expressly excludes from its scope, among others: simple pressure vessels covered by Directive 2014/29/EU; aerosol generators; equipment intended for vehicle operation; certain water distribution networks; nuclear equipment; and well-control equipment for the extractive industry. 3. Fluid classification and its significance One of the Directive’s central pillars is the classification of the fluids contained in the equipment, which determines — together with the pressure and volume or nominal diameter parameters — the applicable risk category. Directive 2014/68/EU updated the classification relative to the previous legislation, aligning it with Regulation (EC) No 1272/2008 (CLP) on classification, labelling and packaging of substances and mixtures. Group Fluids included (simplified criterion) Group 1 Fluids considered hazardous: explosive, extremely or highly flammable, toxic, very toxic, oxidising and corrosive under the CLP Regulation, as well as any fluid at a maximum allowable temperature (TS) above its flash point. Group 2 All fluids not included in Group 1, commonly referred to as “non-hazardous fluids”. Key technical consideration The Directive establishes that thermal oils are classified as Group 1 when the maximum allowable temperature of the equipment exceeds the flash point of the oil in question, regardless of its CLP classification. This specific criterion, set out in Commission Guideline B-41, has direct implications for the resulting category of the equipment. 4. Risk categories The Directive establishes four risk categories (I to IV) for pressure equipment. Category assignment is determined using the tables in Annex II, which cross-reference fluid parameters with equipment parameters (PS, volume V or nominal diameter DN). Category IMinimal risk Low-pressure or small-volume equipment. The manufacturer may self-certify via Module A (internal production control). Category IILow risk Requires involvement of a Notified Body in the production phase. Available modules: A2, D1, E1. Category IIIModerate risk Notified Body involvement in design and/or production. Modules: B+D, B+F, B+E, B1+D, G, H. Category IVHigh risk Maximum requirements. Notified Body required at all stages. Permitted modules: B+D, B+F, G, H1. 5. Conformity assessment modules Module Name NB required Summary A Internal production control No Manufacturer’s self-declaration. Applicable to Category I only. A2 Internal production control with supervised checks Yes The NB performs random inspections of the finished product. B EU-type examination (production type) Yes The NB examines a representative specimen. Must be combined with a production-phase module (D, E or F). B1 EU-type examination (design type) Yes The NB examines the design technical documentation without a physical prototype. D / D1 Production quality assurance Yes The NB approves and supervises the manufacturer’s quality system in the production phase. E / E1 Product quality assurance Yes The NB approves and supervises the quality system for final inspections and testing. F Product verification Yes The NB verifies each produced unit by examination and testing. G Unit verification Yes Individual assessment of each item by the NB, both in design and production. Common for one-off equipment. H / H1 Full quality assurance Yes The NB approves and supervises the complete quality management system. H1 adds design examination and special surveillance. 6. Economic operator obligations Manufacturer Ensure the equipment … Read more