C-DRONE GUIDE · 7 SEPTEMBER 2026

Drone and oilseed crushing plant: silos, hexane extraction, ATEX and roofs

An oilseed crushing plant is three sites in one: a seed store in silos, where rapeseed or sunflower dust turns explosive as soon as it is put into suspension; an extraction building where hexane circulates, a solvent that boils at 68.7°C and whose explosive range starts at 1.1%; and a farm of crude-oil tanks, often lagged, where a leak through a corrosion pit can go unnoticed for a long time. The fatal explosion at Dieppe on 17 February 2018, during maintenance work on a shut-down extractor, reminded the sector what that configuration costs when it goes wrong. It is also why the simplest climb onto a silo walkway or a distillation column requires a work permit, scaffolding or a lift, and sometimes a unit shutdown. Here is what a drone survey, flown from outside the classified zones, documents on this kind of site — and what it never replaces.

Published on 7 September 2026, reviewed on 11 September 2026 — regulations in force as of September 2026.

One crushing plant, three families of risk and as many classifications

France is the European Union's leading oilseed producer, and most of its harvest goes to crushing. Over the 2023/24 season, French plants crushed 4.36 million tonnes of rapeseed, up 3.5% on the previous season, and 1.47 million tonnes of sunflower seed, yielding more than 737,000 tonnes of sunflower meal for animal feed (source: Terres Univia, oil-meal quality observatory). The interbranch organisation works on the basis that one tonne of rapeseed gives 560 kg of meal and 420 kg of oil, and one tonne of undehulled sunflower 540 kg of meal and 440 kg of oil. That tonnage is concentrated on a small industrial base: the French agriculture ministry's sector briefing on vegetable oils and proteins counts « around fifteen » crushing plants in France, belonging mainly to the two leaders, France's Avril and America's Cargill. Few sites, but very large, tall and equipment-dense ones.

In regulatory terms, an oilseed crusher does not fall under one classification but under a stack of them. Crushing itself falls under ICPE heading 2240 (extraction or treatment of oils and fats of animal or vegetable origin). The decisive point: sub-heading A, « extraction using flammable solvents », is classified under authorisation, with no tonnage threshold — as soon as you extract with hexane, you are under authorisation. Other installations fall under sub-heading B, in registration above 10 t/day of production capacity (20 t/day for plants operating no more than 90 days a year) and in declaration with periodic inspection below that, down to 200 kg/day; general requirements are set by the order of 5 December 2016 for declaration and by the order of 24 April 2017 for registration, a regime created by decree no. 2017-594 of 21 April 2017. Upstream, bulk storage of seeds and meal falls under heading 2160 (silos and bulk storage of organic products giving off flammable dust): authorisation above 15,000 m³ for silos other than flat ones, registration above the same volume for flat silos, declaration with periodic inspection between 5,000 and 15,000 m³, under the orders of 29 March 2004, 26 November 2012 and 28 December 2007 depending on the regime. This is exactly the dust risk covered in our guide to flour mill inspection and dust explosion, transposed here to oilseeds.

Then there is the solvent. n-Hexane (CAS no. 110-54-3) is a flammable liquid whose identity card the French industrial accident bureau (BARPI) sets out: boiling point 68.7 °C, density 0.66, explosive range 1.1 to 7.5%, high toxicity. A review published in 2024 in the journal OCL — Oilseeds and fats, Crops and Lipids by a team led by Patrick Carré is devoted entirely to hazard control for solvents used to extract edible oils and proteins in a shifting regulatory landscape (see the study on Google Scholar). Under the French classified-installation nomenclature, category 2 or 3 flammable liquids fall under heading 4331, whose Seveso thresholds are set at 5,000 t (lower tier) and 50,000 t (upper tier). A site may therefore be Seveso, or not: it depends on the quantities actually held and on the substance-aggregation rule, and never follows from the mere presence of hexane. It is the site's prefectoral order, not a general rule, that gives the answer.

Flying on an ATEX site: what that actually means

This is the constraint that shapes the whole mission, and it deserves saying plainly: a standard professional drone is not equipment certified for explosive atmospheres. Site zoning derives from Directive 1999/92/EC, transposed into articles R. 4227-42 to R. 4227-54 of the French labour code: the operator divides its installations into zones 0, 1 and 2 for gases and vapours, 20, 21 and 22 for dust, and records it all in the explosion protection document (DRPCE) required by article R. 4227-52. Directive 2014/34/EU, for its part, governs equipment and protective systems intended for use in those zones. A handful of aircraft claim certifications or attestations for classified zones, but they remain rare, expensive and payload-limited: presenting « the ATEX drone that flies anywhere » as a universal answer would be a sales lie.

In practice the question is settled beforehand, around a table, with the operator. The sequence is always the same: a prior risk assessment run with the HSE department and the ATEX coordinator, based on the site's actual zoning plan; a written prevention plan with a joint prior site walk, as for any outside-contractor job; the definition of a flight corridor that holds agreed distances from classified zones, with take-off and landing points outside those zones and clear of truck traffic lanes; and finally the choice of slot — some views are only available during a unit shutdown, after purging and inerting, or during a production phase when a given installation is stopped. Optical zoom and long focal lengths do the rest: a silo vent or a column head is inspected from several tens of metres away, without ever entering the zone. The logic matches the one detailed in our guide to flare stack drone inspection at a refinery, where the aircraft stays in remote observation of equipment it cannot approach.

The subject is now documented by research. A systematic review by Sairul Safie and Raudhah Khairil, published in 2025 in the journal Transportation Research Interdisciplinary Perspectives, surveys the literature published between 2013 and 2023 on drone-based inspection of chemical process plants: benefits, limits, national and international regulatory frameworks, and the safety challenges specific to hazardous chemical environments (see the study on Google Scholar). The authors note in particular the absence of detailed sector-specific standards for drones in these facilities — which, on the ground, translates into a simple reality: the flight framework is not handed down by an off-the-shelf reference document, it is built site by site with the operator.

What the survey documents, and what it does not measure

The argument fits in one sentence: at an oilseed crusher, the points to inspect are high, numerous and inside a hazardous area. Sending a technician there means scaffolding or a lift, a work permit, sometimes a unit shutdown — heavy resources nobody mobilises just to take a look. An aerial survey flown from outside the classified zone exists precisely to establish where to commit them. The coverage is broad:

• the very large roofs of the crushing halls and meal stores, often several hectares of steel decking and waterproofing membrane, with their dust-extraction ducts, cyclones and gutters;
• the vertical silos and their headhouses: walkways, bucket elevators, handling towers, and clearance of the explosion relief vents — all checked from a distance, without climbing;
• the extraction and distillation columns, the desolventiser-toaster, their platforms and caged ladders;
• the piping and racks, supports, low points and penetrations, following the logic of our guide to industrial pipe-rack and piping drone inspection;
• the heat exchangers and air coolers at height, stacks, ducts and cladding;
• the oil storage tanks and their bunds: shell and roof condition, staining, apparent cleanliness and integrity of the containment;
• the bulk seed and meal stockpiles, under a shed or in the open, whose volume a photogrammetric survey computes rather than eyeballs.

The uses follow: spotting corrosion and lagging damage on columns and racks, thermal imaging of tanks and exchangers, visual checks on vent condition and silo walkways, volume measurement of seed and meal piles, a roof condition report ahead of re-roofing, and a dated photographic file usable both for the environmental inspectorate and for the site's insurer.

The limits must be stated just as plainly. The drone does not measure residual wall thickness: that is a contact non-destructive test, ultrasonics first among them. It does not see corrosion under insulation — and that is precisely the sore point at an oilseed crusher: BARPI notes that leaks on crude-oil tanks are often linked to ageing vessels with corrosion pits, and that when those tanks are lagged to keep the product warm, a leak is not necessarily detected quickly. An aerial survey spots open lagging, a torn band, staining under a cladding jacket, an abnormal thermal gradient: all clues pointing to a spot to strip and check, never a diagnosis. Nor does it replace statutory pressure-equipment inspections, the testing of explosion relief vents by the competent body, or any atmosphere measurement: a camera reads a surface temperature, it quantifies no hexane vapour concentration. The drone documents and prioritises; the technical decisions stay with the inspection body and the maintenance department.

Who commissions this kind of mission, method and 2026 prices

Requests come from oilseed crushers and vegetable-oil refiners, from sites producing meal and biodiesel, from their maintenance, QSE and HSE departments, from the ATEX coordinators and consultants who keep the explosion protection document up to date, from inspection bodies preparing a survey campaign, and from industrial insurers wanting a dated condition report before renewing a policy. The typical run: one to two days on site depending on the footprint, preceded by a joint prior site walk and a prevention plan settled in advance — as on any job at a sensitive site, following the logic of our guide to pharmaceutical and fine chemical plant drone inspection. The flight runs a photogrammetric pass over roofs and buildings for the orthophoto and 3D model, close zoom shots of silo headhouses, columns and racks, a thermal pass over tanks and exchangers where included, and a survey of the seed or meal piles if volume measurement is requested.

Ranges observed in France in 2026, excl. VAT:

A travel charge applies beyond a 30 to 50 km radius, and a standby day may be charged where the slot depends on a postponed unit shutdown. These amounts cover the flight, image processing and report delivery; they include neither non-destructive testing, nor pressure-equipment inspection, nor atmosphere measurement. For a crushing plant, an oil refinery or a meal production site, request a quote stating the roof area, the height of the silos and columns, the applicable ATEX zoning plan and the goal (regulatory file, maintenance campaign preparation or condition report for insurance).

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