Heating and transfer in ATEX process environments
The zone classification defines how the work must be done — every component involved must be engineered for it before equipment is selected.
A classified process environment is not a special category of facility. It is a facility where a flammable atmosphere may occur — determined by the substances handled, their flash points, vapour pressures and the way they are stored, processed and transferred. Petroleum terminals, chemical plants, paint and coatings manufacturing, solvent-based adhesive production, pharmaceutical API manufacture and a wide range of other industries operate routinely in classified areas.
The process requirements in those environments are the same as anywhere else. What changes is the engineering of the systems that meet them. Drum heaters, IBC heaters, pipe trace heating, pump heating and heated transfer lines all exist in ATEX-rated versions. The ATEX version differs in element construction, control architecture, certification route and, in some cases, fundamental system architecture — but it performs the same process function.
The most common difficulty in ATEX process heating projects is not finding certified equipment. It is integrating that equipment correctly into a classified installation — with the right T-class for the substances present, the right certification category for the zone, and a complete certification chain from individual components to the installed system.
Process environments where ATEX heating is required
ATEX zone classification arises wherever flammable substances are stored, processed or transferred. The following environments represent the most common contexts for ATEX-rated heating and transfer systems.
- Petroleum product handling. Fuel storage and distribution terminals, lubricant blending plants and tanker loading facilities. Zone classification covers pump and valve areas, loading connections and drum and IBC filling stations. Heating requirements include heavy fuel oil tank heating, viscous lubricant drum heating and trace heating on transfer pipework. T3 is the most common temperature class requirement for petroleum product environments; IIB gas group is typical for most fuel handling areas.
- Chemical processing. Solvent-based production, specialty chemical manufacturing and chemical distribution facilities. Flash points below 60°C are common, generating Zone 1 and Zone 2 areas across much of the production floor. Heating tasks include drum and IBC heating of raw materials, heated transfer lines for viscous chemical intermediates and process vessel temperature maintenance. Substances with low AITs — ethers, aldehydes, some ketones — may require T4 or T5 classification.
- Paint and coatings manufacturing. Solvent-based and reactive systems. Resin raw materials, solvents and finished products frequently require heated storage and temperature-maintained transfer. The production area classification depends on the specific solvent portfolio — aromatic hydrocarbons and esters are typically Zone 2; more volatile solvents may generate Zone 1 conditions at mixing and transfer points.
- Pharmaceutical API manufacture. Active pharmaceutical ingredient synthesis frequently uses flammable solvents — ethanol, isopropanol, acetone, ethyl acetate and others. Reaction vessels, solvent storage and recovery areas are classified zones. Heating requirements include reactor jacket heating, solvent drum and IBC heating, and trace heating on transfer lines. Pharmaceutical environments typically impose additional documentation requirements beyond ATEX — GMP validation and equipment qualification frameworks apply alongside safety compliance.
- Adhesive and sealant production. Hot melt adhesive manufacturing, polyurethane component blending and reactive sealant production. Classified areas arise from isocyanate vapour pressures, solvent-based formulation processes and reactive monomer handling. Drum and IBC heating is a core process requirement; the temperature sensitivity of many reactive adhesive components means control precision and over-temperature protection are as important as ATEX compliance.
- Biogas and renewable fuel facilities. Biogas upgrading, biomethane production and certain biofuel processing operations. Classified areas arise from methane and other flammable gas handling. Heating requirements include digestate and process liquid temperature maintenance, trace heating on gas handling pipework and heated storage of bio-based viscous products.
Integrating heating systems into a classified process installation
The process heating requirement defines what needs to be done — target temperature, container or vessel type, transfer route, duty cycle. The zone classification defines how it must be done — equipment category, T-class, gas group, control architecture, certification chain. In practice, these two sets of constraints must be resolved together from the start.
The zone classification drawing must exist before any equipment is specified. Without it, T-class, gas group and equipment category cannot be determined. Specifying equipment without those parameters produces either over-specification or non-compliance — both of which are discovered late and corrected expensively.
The zone classification drawing is the starting point for equipment selection, not an afterthought. It defines which areas are Zone 1 and which are Zone 2, where zone boundaries run, and what substances govern the T-class and gas group requirements for each area. Without this drawing, it is not possible to specify compliant equipment — and in practice, many projects attempt to do so anyway, resulting in either over-specification (Zone 1 equipment installed throughout because the zone boundary was not checked) or non-compliance (Zone 2 or unrated equipment installed in Zone 1 areas).
A recurring integration difficulty is the control panel location. A temperature controller installed inside the zone must carry ATEX certification appropriate to the zone. An Ex d or Ex p enclosure for a Zone 1 area is substantially heavier, larger and more expensive than a standard industrial enclosure, and limits what can be installed inside it. The practical alternative — locating the controller outside the zone boundary and running intrinsically safe sensor circuits into the zone — is almost always preferable. This decision must be made at the design stage; relocating a control panel after installation is a significant rework.
For process environments with multiple heating loads — several drums or IBCs, multiple trace heating circuits, pump and valve body heating — a centralised control panel outside the zone with individually controlled circuits per load is the standard architecture. Each load within the zone still requires ATEX-certified heating elements; the controllers, displays and safety cut-outs can all be located outside.
Integration decisions that must be made before procurement:
- Zone boundaries confirmed on drawing — which loads are in Zone 1, which in Zone 2
- T-class determined from substance AIT data for each zone area
- Gas group determined from substance properties
- Controller and cut-out location — inside zone (ATEX-rated enclosure) or outside (preferred)
- Certification category for each heating load — Category 2 (Zone 1) or Category 3 (Zone 2)
- Custom items requiring Notified Body involvement identified and lead time built into project schedule
Related resources
If the installation involves Zone 1 areas, multiple heating loads or a requirement to integrate heating with existing process equipment, system design should be defined before procurement. Retrofitting compliant solutions into an already installed system is significantly more complex and costly.
Process heating for classified environments — built in-house
HeatXperts designs and manufactures ATEX-certified heating systems for classified process environments across chemical, petroleum, pharmaceutical and manufacturing industries. System design starts from the zone classification drawing and substance data — not from catalogue selection followed by compliance verification.
Where the process requires non-standard configurations — custom drum dimensions, high wattage at restrictive T-class, integrated multi-load control panels — we work through the engineering and certification from the start.