C‑DRONE
Tiled rooftops seen from above during a drone inspection

C-DRONE GUIDE · 25 AUGUST 2026

Industrial Glassworks Drone Inspection: Hall Roofs, Furnace, Chimney and Cullet Yard

A glass furnace never stops. Once lit, it melts continuously for a whole furnace campaign — several years — until the scheduled cold repair, and the entire building lives under that constraint : a structure that is never cold, vents permanently open to shed heat, a production line running 24/7 beneath the roof, and no shutdown window in which to send someone up to check the steel decking. As a result, in many container-glass, float-glass or technical-glass plants, the site's outer envelope only gets a serious look at rebuild time — roughly once a decade. The drone fills that gap : in a single campaign it documents the hall roofs, the furnace casing and chimney as seen from outside, and the cullet and raw-material yards. Here is what it brings, what it emphatically does not replace, and the prices.

Published on 25 August 2026, reviewed on 25 August 2026 — regulations in force as of August 2026.

The ICPE framework of a glassworks: heading 2530, IED regime above 20 t/day

In France, glass manufacturing falls under ICPE heading n° 2530, "manufacture and working of glass", whose classification is based on the production capacity of the melting and softening furnaces rather than on finished-product tonnage. For soda-lime glass — the family covering container and flat glass — the installation is subject to declaration between 500 kg/day and 5 t/day and to authorisation above that ; for other glasses, including technical and special compositions, the thresholds drop to 50 kg/day for declaration and 500 kg/day for authorisation, reflecting the specific constraints of those melts. The order of 14 February 2007 sets the general requirements of the declaration regime ; authorised sites come under the order of 12 March 2003 on the glass and mineral-fibre industry, supplemented by their prefectural operating order.

A typically sized industrial glassworks is far above those thresholds : a container-glass furnace routinely produces several hundred tonnes of molten glass a day. It therefore falls into the IED regime under heading 3330, "manufacture of glass, including glass fibre, with a melting capacity exceeding 20 t/day" — the neighbouring heading 3340 covering the melting of mineral substances and the production of mineral fibres above the same threshold. At European level, the sector's best available techniques are set by Commission implementing decision 2012/134/EU of 28 February 2012, establishing the BAT conclusions for glass manufacturing under directive 2010/75/EU.

None of that regulatory architecture — emissions, energy, processes — is drone territory. Emissions monitoring remains the job of the operator's continuous instrumentation and periodic checks by an accredited body. What the drone documents is the outer condition of the buildings and structures, on exactly the logic already described for drone inspection of a foundry : a dated visual record between two technical shutdowns, never a substitute for a measurement obligation.

Furnace and production hall roofs: a structure that is never cold

What sets a glassworks apart from almost every other classified industrial site is the permanence of the thermal load. Where a foundry takes shocks in rhythm with its pours, and a cement kiln has maintenance shutdowns, a glass furnace runs without interruption for its whole campaign — industry sources quote five to fifteen years depending on design, refractory quality and operating practice. Under the furnace hall roof the atmosphere is therefore permanently hot and dry, with a continuous upward flow escaping through large-section lanterns and vents kept open all year to shed heat. Those openings are the first weak points : upstand waterproofing, corrosion of the kerbs, control mechanisms that age badly in a loaded atmosphere.

Two quieter aggressors add to the thermal load. First mineral dust : fines of sand, soda ash and limestone escaping the batch house, cullet fines, local fallout. It builds up on the roof, traps moisture against the steel deck and eventually blocks gutters and rainwater downpipes — the classic route to ponding and then infiltration. Second, sulphur oxides from the fuel and from sulphate fining agents : they make the local atmosphere mildly acidic and accelerate corrosion of sheeting, fixings and seals, particularly downwind of the chimney outlet. The contrast between the indoor climate and a winter night also produces condensation in the cooler parts of the building — packing, palletising, finished-goods store — with the damp-insulation problems that follow.

The difficulty is not knowing what to look at, it is getting there. An uninterrupted line runs beneath that roof : forming machines, annealing lehr, quality control, palletisers. A foot inspection requires fall protection, ground marking beneath the work zone and coordination with a production line that will not stop for the occasion — hence how rarely these rounds happen, often only after the fact, once a leak has already appeared above a machine. A flight combining high-resolution orthophoto and a thermal pass returns the full condition of the roof slopes, vents and rooftop equipment in half a day, without tying up a single square metre of floor.

Furnace and chimney from outside: what thermal imaging shows, and what it does not

A tank-type glass furnace is a bath of molten glass topped by a refractory superstructure — crown, breast walls, casing — clad in insulation and held by a steel binding frame. Downstream of the tank, the flue gases give up their heat in a regenerator (chambers of stacked brick checkerwork, alternately heated and returning their heat to the combustion air at the rhythm of the flame reversals) or, on smaller furnaces, in a metallic recuperator. They then pass through the ducting and the flue-gas treatment before reaching the chimney. That whole circuit is insulated, and that whole circuit ages without any possibility of shutting it down.

An external thermal pass by drone sees useful things there : a localised hot spot on the superstructure casing, the sign of an open joint or local refractory thinning ; an insulation defect on the flues, the regenerator chambers or the duct run, which translates directly into quantifiable energy loss ; parasitic air ingress or a hot-gas leak on a pierced section ; abnormal heating of a steel anchorage on the furnace binding ; the outer condition of the chimney shaft, cracking, corrosion, expansion joints, caged ladder and aviation marking. On that last structure the approach matches exactly what our guide to drone inspection of industrial chimneys and silos describes, and the thermal maps are read with the same method as for thermography of a cement plant rotary kiln.

Three limits must be stated plainly. The drone measures no emissions — no dust, no nitrogen oxides, no sulphur oxides : that monitoring belongs to the operator's analysers and to statutory checks. It gives no residual refractory thickness : an outer-skin temperature only converts into thickness through a thermal model calibrated on the furnace's operating data, and assessing tank-block wear is the refractory supplier's and the furnace engineering firm's job. It does not replace the operators' surveillance rounds, nor the permanently installed fixed cameras and thermocouples. Its contribution is narrower and more precise : a complete external map, dated, comparable from one campaign to the next. A study by Méndez Bohórquez and co-authors, presented in 2022 at the European Workshop on Structural Health Monitoring (Springer, Lecture Notes in Civil Engineering), compares exactly that — thermograms of an electric melting furnace's refractory walls before and after refurbishment : the twenty-two-year-old walls show higher and, above all, more scattered temperatures than the new ones, making thermography a good non-destructive indicator of how wear evolves — an indicator, not a thickness measurement (see the study on Google Scholar).

Cullet yard, batch silos and ancillaries: the quantitative side

Cullet — recycled glass returned to the furnace — is no longer a top-up : according to the decarbonisation roadmap published by the French glass industry, it accounts for around 65% of the raw materials in container glass produced in France, and some coloured-glass furnaces run above 90%. The stake is as much energy as material, since an extra 10% of cullet in the batch cuts furnace consumption by roughly 2.5 to 3%. A cullet yard is therefore a strategic stock, trucked in from processing centres, stored in open-air piles or bays, and whose real volume drifts quickly from the theoretical figure : settling, moisture, partial reclaims by loader. A drone photogrammetric volume survey resets that figure in a single flight. A study by Tucci, Gebbia, Conti, Fiorini and Lubello, published in 2019 in Remote Sensing, validated the approach on bulk-material stockpiles against conventional topographic surveys, and confirms that a properly calibrated flight protocol yields a volume usable for industrial monitoring (see the study on Google Scholar).

The same flight documents the rest of the ancillaries. The raw-material silos — sand, soda ash, limestone, dolomite — often form a vertical battery fifteen to thirty metres high, topped by venting filters and linked to the batch house by enclosed conveyors. These mineral silos do not fall under heading 2160, which is reserved for storage releasing flammable organic dust ; their issues lie elsewhere : corrosion of the shell and stiffeners, condition of the filters and vents, powder leaks at a loading spout, state of walkways and ladders. All of which a close-in flight records without scaffolding or a platform.

That leaves the flue-gas treatment plant — electrostatic precipitator or bag filter, reagent injection, possibly a nitrogen-oxide reduction unit — whose housing and ducting read well in thermal imaging ; and, where the site has them for its mould-cooling circuits or compressors, the cooling towers, classified under heading 2921 covering evaporative cooling by water dispersion in an air stream and, on that basis, subject to a maintenance plan against legionella risk : their drone inspection has its own dedicated guide on this site.

Organising the mission on a site running 24/7

Preparation matters more here than the flight itself. Like any intervention by an outside company on an industrial site, the mission sits within a prevention plan drawn up with the operator after a joint preliminary visit, backed by a safety briefing and the usual induction : site rules, protective equipment, traffic routes. Our guide on hosting a drone mission on an industrial site sets out that formal process and the management of coactivity with other contractors, which is intense in a glassworks where mechanical maintenance, refractory specialists and pallet logistics all overlap.

Two specifics are worth anticipating. The first is the absence of any shutdown window : the mission is not timed against a production break but against a period of lower vehicle traffic, often around a shift change. The second concerns the ground exclusion zones, which the pilot must know before arriving : the immediate surroundings of the furnace and the charging machine, the cullet reclaim area where loaders manoeuvre, loading docks and forklift aisles, and any oxygen or fuel-gas storage station. The take-off point and the fallback landing area are chosen clear of all of these, and validated during the preliminary visit.

Then there is the site's own air behaviour. Above the roof vents and the chimney outlet, the heat plume creates a turbulent rising column that destabilises a light multirotor and corrupts the thermal image. The remedy is simple but must be written into the flight plan : no vertical crossing of the plume, a systematic lateral margin, and thermal passes flown in stabilised hover at sufficient distance, compensating with a longer lens if needed. Mineral dust also calls for a lens check between battery swaps, on pain of degrading the photogrammetric mosaic.

Method, flight framework and prices

The sequence is a settled one. Remote reconnaissance and airspace analysis first — a glassworks is almost always sited in an industrial zone, sometimes under an aeronautical easement or close to an aerodrome, which drives the flight altitude and the clearances required. The flight is conducted in the open category where the configuration allows, with the drone kept away from uninvolved people and inside the site's fenced perimeter ; a prior declaration applies if the plant borders a populated area, which is common in older industrial fabric. Then come the preliminary visit and the prevention plan, and finally the campaign itself : half a day to a full day of flying for a typically sized site, in two passes — vertical photogrammetry for the orthophoto and the stockpile model, oblique close-in thermal passes for the furnace, the ducting and the chimney.

The deliverable pairs a georeferenced orthophoto of the whole site with a radiometric thermal mosaic of the roof and hot structures, a schedule of defects ranked by zone and located on plan, and, if the mission includes it, a volume survey of the cullet yard and outdoor stocks with its method note. Allow one to two weeks between the flight and delivery of the report. 2026 prices (excl. VAT) : €1,000 to €2,200 for a typically sized glassworks (hall roofs plus a thermal pass over the furnace, ducting and chimney), rising to €2,500-3,800 with the cullet yard volume survey, the batch silos and the ancillaries included ; an annual follow-up campaign, reflown on the same flight plan, typically costs 20 to 30% less than the initial one — and it is the year-on-year comparison that gives the exercise its full value.

To settle the internal business case, our guide on calculating the return on investment of a drone industrial inspection offers a method for comparing against the full cost of a platform or rope-access intervention, line downtime included. The drone thermography page sets out the service in detail ; request a quote stating the type of glass produced, the furnace melting capacity, the year of the last rebuild and the scope you want (roofs only, roofs and hot structures, or a full campaign with volume survey).

Frequently asked questions

Do we have to stop the furnace or the line for the drone to fly?

No — and that is the main point of the service : the mission runs on a fully operating site, since the drone stays outside the buildings and flies over neither occupied workstations nor vehicle traffic areas. We simply time the flight for a window of lower logistics activity, often a shift change, and keep a lateral margin above the vents and the chimney outlet to avoid the heat plumes.

Can thermography tell us how much refractory is left in the furnace?

No. An outer-skin temperature map flags an abnormal gradient — that is, an area to look at closely — but it does not convert into remaining thickness without a thermal model calibrated on the furnace's operating data. Assessing wear on the tank blocks and the superstructure remains the job of the refractory supplier and the furnace engineering firm, with their own inspection means. The drone provides an entry point and a dated record ; it replaces neither that expertise nor the furnace operators' surveillance rounds.

Can the drone be used to check our air emissions?

No : statutory emissions monitoring at a glassworks — dust, nitrogen oxides, sulphur oxides — rests on the operator's continuous analysers and on periodic checks by an accredited body, under the conditions set by the prefectural order and the applicable ministerial requirements. The drone measures no concentration. What it does spot are indirect thermal anomalies on the flue ducting and the filter housing, which point the maintenance department toward the right check.

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