Tile, Brick & Ceramic Manufacturing HVAC Ductwork Guide — Kiln Exhaust, Glaze Line & Silica Dust Capture

Why ceramic-plant ductwork is different

Ceramic manufacturing — bricks, wall and floor tile, sanitaryware, roof tile, refractory shapes — sits at the awkward intersection of three industrial environments that each defeat ordinary HVAC duct in their own way. From the clay-preparation end you get respirable crystalline silica (RCS) at concentrations that exceed the 0.05 mg per cubic metre Safe Work Australia limit within a few metres of any uncontrolled source. From the firing end you get kiln exhaust at temperatures that volatilise zinc galvanising long before the metal itself fails. And from the glaze line you get fluoride and chloride fume that condenses into hydrofluoric and hydrochloric acid at every cold-end joint in the duct. Specify galvanised steel rectangular duct the way a residential or commercial HVAC contractor would, and the system is leaking dust and corroding through within twelve months.

This guide is the playbook our engineers use when we quote a duct fabrication line for a ceramic plant — the kind of plant that builds the bricks for a new Sydney apartment, the porcelain tile for a Melbourne bathroom renovation, the toilet bowl in a Brisbane high-rise, or the alumina refractory liner inside a Port Kembla blast furnace. The Australian ceramics sector is concentrated, capital-intensive and conservatively engineered — the same plants have been firing kilns at the same sites for fifty years or more — but the equipment is constantly being upgraded, the dust limits have been tightened, and the AS 1668.2 / NFPA 86 stack does not forgive duct that was cheap on day one.

We have written it so that a procurement manager, a plant engineer or an HVAC fabricator can each take what they need. If you only have ten minutes, skip to the section How SBKJ machines fit ceramic-plant duct fabrication at the end. If you have the afternoon, walk through the process zones from clay receival to packaging with us.

The Australian ceramic-manufacturing landscape

Before the duct, the buyer. Australian ceramic manufacturing is not a fragmented sector. Five or six corporate groups operate the majority of the country's brick, tile and sanitaryware capacity, and a small number of refractory suppliers handle most of the high-temperature linings used in steel, glass, cement and aluminium plants. Understanding the buyer set matters because each group has its own duct specification, its own preferred fabricator panel, and its own engineering review process.

Brick manufacturing

Brickworks Limited (ASX:BKW) is the dominant player. Listed on the Australian Securities Exchange and headquartered in Sydney, Brickworks operates more than fourteen brick plants nationally under several brand names. Austral Bricks is the volume brand with plants in every state — Wollert and Craigieburn in Victoria, Horsley Park and Punchbowl in New South Wales, Cornubia in Queensland, Golden Grove in South Australia, Cardup in Western Australia, and Longford in Tasmania. Bowral Bricks in the Southern Highlands of New South Wales is the premium dry-press range used heavily in heritage and high-end residential. Daniel Robertson Bricks at Selbourne in Tasmania produces the dry-pressed range that has defined Tasmanian architecture for over a century. Nubrik manufactures from the Wollert plant in Victoria.

Brickworks also operates the country's two largest roof-tile brands as subsidiaries — Bristile Roofing and Monier Roofing — through plants at Wacol in Queensland, Rosehill in New South Wales, and Boral's former Glenn Innes site in Victoria. Roof tile is closer to concrete masonry than to fired ceramic in some ranges, but the terracotta lines remain a fired-clay product with all the dust, heat and acid-fume challenges of a brick plant.

CSR Limited (ASX:CSR) owns PGH Bricks, formerly known as PGH Pacific. PGH operates plants at Horsley Park New South Wales, Oxley and Rochedale Queensland, Cardup Western Australia, and Schofields New South Wales. PGH is the second-largest masonry-clay producer in the country and the joint number-one in roof-tile capacity through the CSR Monier joint history. CSR's Hebel autoclaved aerated concrete plant at Somersby is a different process — not fired ceramic — but the dust-capture engineering overlaps.

Boral Limited (ASX:BLD) exited brick manufacturing through divestment to CSR over multiple transactions, but Boral Bricks legacy plants at Bunbury and Cardup in Western Australia, Glen Iris and Geelong in Victoria, Murrumbeena in Victoria, and the former Concrite Sydney facility in New South Wales remain in operation under PGH or successor ownership. Boral still operates roof-tile and masonry concrete capacity.

Wall and floor tile

Australia is a net importer of porcelain and ceramic wall-and-floor tile, with the bulk of mid-market and high-end product imported from Italy, Spain and elsewhere. Local manufacturing capacity is concentrated in a handful of operations. Beaumont Tiles, owned by the Reece Group (ASX:REH), operates a national distribution network with house-brand manufacturing capacity. National Tiles, also Reece-owned, similarly mixes distribution with selected manufacturing for the mid-market segment. Italtile imports and distributes high-end European product. Tile Importer operates as an independent national wholesaler. Earp Bros mixes tile distribution with local manufacturing for specialised mosaic and bespoke architectural ranges.

Sanitaryware ceramics

Sanitaryware — the cast-and-fired vitreous-china toilets, basins, bidets and urinals that fill every commercial bathroom — is the most technically demanding ceramic segment. Caroma Industries, owned by GWA Group (ASX:GWA), operates the largest local sanitaryware manufacturing capacity in Australia from Eltham in Victoria with additional operations in Sydney. Caroma is the brand behind the patented dual-flush cistern that became a global water-saving standard. Roca Australia and Kohler Australia import most of their range but maintain warehousing and after-sales engineering teams locally.

Refractory ceramics

Refractory ceramics — alumina, silica, magnesia, zirconia, silicon carbide — are the high-temperature linings that protect steel furnaces, glass-melting tanks, cement kilns and aluminium smelters. The Australian market is supplied by Vesuvius Australia from Geelong in Victoria with a national service-and-application engineering footprint, and by Calderys Australia. Refractory plants run hotter and dirtier than brick or tile plants — drying ovens at 250–400 degrees Celsius, firing at 1600–1800 degrees Celsius — and the ductwork specification is at the extreme end of the ceramic-industry envelope.

Across all six segments the duct fabrication panel is overlapping. The same Melbourne or Sydney HVAC fabricator who supplies a Brickworks Austral plant probably also supplies a Caroma sanitaryware kiln and a Vesuvius refractory plant. The duct specs differ by zone but the buyer relationships do not.

Process zones and contaminants

A ceramic plant is best understood as seven sequential process zones, each with its own contaminant signature and its own duct specification. Walk through them in order.

Zone 1 — raw clay receival and storage

Raw clay arrives on tipper truck, rail or — at a small number of pit-side plants — by conveyor from the quarry next door. Common clay materials include ball clay, china clay (kaolin), fire clay, stoneware clay and a host of regional alluvial clays. Sanitaryware and porcelain plants also receive feldspar, silica sand, alumina and other body components in twenty-tonne bulk-bag deliveries. The dominant contaminant is silica dust released during tipping, conveyor transfer and bunker loading. Capture velocity required at the source under AS 1668.2 industrial tables is 1.0–1.5 metres per second at a tipper grizzly, rising to 2.5 metres per second at conveyor transfer points. Transport velocity in the spiral main is 18–20 metres per second to keep coarse particle in suspension.

Duct material: galvanised carbon steel rectangular or spiral round at ambient temperature, but with abrasion-resistant interior lining on any duct seeing more than 50 kilograms per hour of particulate. Hardox or Bisalloy abrasion plate at elbows and tees is common; SBKJ supplies spiral mains in heavier 1.5 mm or 2.0 mm coil specifically for abrasion duty.

Zone 2 — clay preparation, mixing and pugging

The clay-prep area is where raw materials are weighed, blended, ground and brought to the consistency required for forming. Pan mixers, blungers, ball mills, hammer mills and pug mills all release silica dust at the entry hood and across the mill body. Wet processes — slip making for sanitaryware, glaze preparation, plastic pugging for brick — generate steam and mist rather than dry dust. Dry processes — dry-press tile body preparation, fettling-room polishing — are the heaviest dust sources in the plant.

The Safe Work Australia workplace exposure standard for respirable crystalline silica is 0.05 milligrams per cubic metre averaged over an eight-hour shift. This is the standard that drives almost every duct decision in clay prep. Capture velocity at a dry-press feeder is 2.0–3.0 metres per second; at a fettling table it is 0.75–1.0 metres per second with the operator's breathing zone directly above the slot hood. Transport velocity in the dust main is 18–22 metres per second. A cyclone precleaner discharging to a reverse-pulse fabric filter at 0.005 grains per actual cubic foot is standard.

Duct material: galvanised spiral with bolted access doors at 6 metre intervals for inspection. SBKJ supplies the spiral mains in standard galvanised G275 coil, with the option of 304 stainless for plants running lithium-bearing flux compounds where carbonate aggregates make the dust mildly hygroscopic.

Zone 3 — forming

Forming is where the prepared clay body becomes the green ware that will be fired. Three main techniques are used in Australian plants. Extrusion is the dominant brick-forming method — clay is forced through a die at the back of an auger pug mill, then cut to length by a wire-cutter. Pressing is the dominant tile-forming method — dry or semi-dry body is loaded into a hydraulic press at 200–400 megapascals and stamped into shape. Slip casting is the dominant sanitaryware method — slip (clay in water suspension) is poured into plaster moulds where the porous plaster draws water out and leaves a wet ceramic shell.

Forming releases relatively little dust because the clay is at working moisture (15–25 per cent for plastic forming, 5–8 per cent for dry pressing). What it does release is fine spray and atomised water near press platens and slip-casting bench drains. Local exhaust ventilation at the press is typically a top hood at 0.5 metres per second to capture the puff of fine dust released when the press opens; at the slip-casting bench LEV is rarely required.

Duct material: galvanised spiral or rectangular at modest velocities (12–15 metres per second).

Zone 4 — drying

Green ware contains 15–25 per cent water by weight (less for dry-pressed body, more for slip-cast body) and must be dried to under 2 per cent before firing. Tunnel dryers or chamber dryers operate at 100–110 degrees Celsius with a relative humidity gradient that starts at 80–90 per cent at the wet end and falls to 30–40 per cent at the dry end. The drying air carries large volumes of water vapour, and the duct construction must handle continuous condensation at any cold spot.

This is where galvanised duct first comes under serious thermal stress. Continuous service at 100–110 degrees Celsius approaches the limit of zinc coating durability. Spot coating loss is acceptable on the supply side where air is clean; on the return side, water-laden air condensing on a cooler duct wall accelerates corrosion dramatically. The standard solution is fully insulated galvanised duct on the supply with an internal vapour-resistant lining (Ventilex or equivalent factory-applied liner), and 304 stainless or aluminium-magnesium duct on the return.

Duct material: insulated galvanised supply, 304 stainless return. Drain points every 12 metres at any low point.

Zone 5 — firing

The kiln is the defining piece of plant in any ceramic operation, and it generates the most demanding duct conditions in the entire factory. Three kiln types dominate Australian ceramic manufacturing.

Tunnel kilns are continuous kilns several hundred metres long through which the ware travels on kiln cars. Brick, roof tile and large-format ceramic tile are fired in tunnel kilns. Firing temperature 950–1100 degrees Celsius for face brick and roof tile, 1100–1280 degrees Celsius for stoneware paver and porcelain tile. Cycle time 24–60 hours through the full length of the kiln. The exhaust stack handles up to 100,000 cubic metres per hour at 200–350 degrees Celsius after primary air dilution.

Shuttle kilns (also called intermittent or trolley kilns) are batch kilns where loaded kiln cars are wheeled in, the door is closed, and the firing cycle is run from cold. Shuttle kilns are favoured for short production runs of specialty product — premium dry-pressed brick, bespoke sanitaryware, refractory shapes. Firing temperature 1000–1300 degrees Celsius for ceramic body, 1500–1800 degrees Celsius for refractory body. The exhaust is intermittent but the peak stack temperature is the highest in the plant.

Roller hearth kilns are continuous kilns where the ware travels on heated ceramic rollers rather than on kiln cars. Roller hearth is the standard for wall and floor tile globally because cycle time is short (40–60 minutes) and the energy efficiency is excellent. Firing temperature 1100–1250 degrees Celsius for monoporosa and stoneware, 1200–1280 degrees Celsius for porcelain. Exhaust at 220–320 degrees Celsius.

NFPA 86 standard for ovens and furnaces is the controlling safety code for any kiln firing on natural gas, town gas, propane or liquefied petroleum gas. NFPA 86 governs combustion air supply, fuel train safety shut-off valves, ignition and flame supervision, pre-purge volume (typically four air changes before light-off), and the design of the kiln exhaust. AS 1668.2 sits alongside NFPA 86 for the general ventilation of the kiln building. The combination drives a duct design that is fundamentally different to what a residential or commercial HVAC fabricator is used to.

Duct material at the kiln itself: refractory-lined carbon steel up to about 600 degrees Celsius. The lining is typically a 50–75 mm thickness of high-alumina castable refractory or ceramic-fibre blanket inside a 5–8 mm structural steel skin. The outside of the duct stays cool enough to touch (60–80 degrees Celsius) while the inside takes the kiln temperature. For service above 600 degrees Celsius the material moves to 309S or 310S austenitic stainless steel — these grades carry significantly more chromium and nickel than 304L or 316L and retain mechanical properties to about 1000 degrees Celsius. The exhaust fan is positioned far enough downstream that the gas has cooled to below 250 degrees Celsius, at which point the duct can transition back to ordinary structural carbon steel or 304 stainless.

This is the single specification decision that costs the most money and saves the most maintenance over a kiln's twenty-year life. Galvanised duct at 250–350 degrees Celsius volatilises its zinc coating within months and produces white zinc-oxide fume that contaminates the next firing batch. Plain carbon steel at the same temperature scales heavily and sheds rust into the duct stream. The refractory-lined option pays back the higher capital cost within five years against avoided downtime and product contamination.

Zone 6 — glazing

Most fired ceramic products are glazed before the final firing or during a second pass. Glaze is a glass-forming suspension of frit (pre-fused glass), feldspar, kaolin and colourants in water, applied by spray, dip, waterfall or screen-printing. The glaze line is dust-and-fume intensive in two ways.

First, atomised glaze spray loss in the glazing booth — a fine, slightly acidic aerosol that condenses on cold duct walls. Capture is by water-curtain wash hood, side-draught hood or downdraught grille at 1.0–1.5 metres per second face velocity, with the captured spray draining back into a glaze sump for recovery. Duct material is 316L stainless steel because the spray carries dissolved metal salts and a low-pH wash water that would corrode 304 within months.

Second, fluoride fume released during firing. Most ceramic frits contain calcium fluoride, sodium fluoride or other fluoride compounds as melting-point depressants. At firing temperature these fluorides partially volatilise as hydrogen fluoride (HF) gas. At the cool end of the kiln exhaust the HF condenses with water vapour into hydrofluoric acid, which attacks galvanised duct, 304 stainless and carbon steel alike. The standard solution is 316L stainless duct at the cool end and a wet acid scrubber sized for the calculated fluoride load. 316L is not perfectly resistant to HF either — at high concentration and elevated temperature even 316L will pit — but it gives the best balance of cost and service life among readily available duct materials.

Duct material: 316L stainless throughout the glaze line booth ductwork; 316L stainless or refractory-lined carbon steel for the kiln exhaust handling fluoride-bearing gases.

Zone 7 — cooling, sorting, packaging

The cooling section of a tunnel kiln, or the post-firing cooling tunnel of a roller hearth, releases hot air that is largely free of dust and fume but contains significant thermal energy. Many modern plants recover this heat by ducting the kiln cooling air back to the dryers — a net energy saving of 15–25 per cent on plant gas consumption. The recovery duct runs at 150–250 degrees Celsius, well below the volatilisation point of zinc, so insulated galvanised duct or insulated 304 stainless duct is adequate.

Sorting and packaging are at ambient temperature and the only contaminant is fine ceramic dust from broken-tile fettling, edge-trimming and palletising. Standard galvanised LEV duct at 1.0–1.5 metres per second capture velocity is sufficient.

Australian and international standards that apply

The standards stack for a ceramic plant duct system in Australia is layered. No single document covers it end-to-end; the engineer reads three or four standards in parallel.

AS 1668.2 — The use of ventilation and air-conditioning in buildings: Mechanical ventilation in buildings

AS 1668.2 is the parent standard for mechanical ventilation. The general residential and commercial sections are well-known to every HVAC consultant in Australia. The often-overlooked industrial-process section provides minimum exhaust rates, capture velocities and air-change rates for specific process types. For ceramic plants the relevant tables cover dusty operations, hot-air drying, kiln firing and acid-fume scrubbing. The base rates in AS 1668.2 are minimums — most ceramic plants operate at 1.5–2.0 times the AS 1668.2 minimum because the RCS exposure standard is binding.

AS/NZS 4254.2 — Ductwork for air-handling systems in buildings: Rigid duct

AS/NZS 4254.2 is the duct fabrication standard. Gauge, joint type, sealing class, hanger spacing and pressure class are all defined here. Ceramic plants typically build to high-pressure (HP) class for kiln exhaust trunks and medium-pressure (MP) class for clay-prep dust mains. The standard does not specifically address refractory-lined or stainless duct but extrapolation is straightforward — the dimensional and joint requirements transfer; the material substitution is documented on the project drawing.

NFPA 86 — Standard for Ovens and Furnaces

NFPA 86 is the US National Fire Protection Association standard for industrial ovens, furnaces, dryers and kilns. It is widely adopted in Australia for fuel-fired industrial heating equipment in the absence of a directly equivalent Australian standard. NFPA 86 covers combustion air sizing, pre-purge requirements, fuel train safety shut-off valves, flame supervision, and the design of explosion-relief venting for any oven where the atmosphere could become flammable (organic-binder firing, paint baking, food drying). For most ceramic kilns the atmosphere is non-flammable but the fuel train and combustion safety provisions of NFPA 86 are mandatory under Australian gas regulations and most state energy safety regulators reference NFPA 86 directly in industrial gas installation rulings.

NFPA 660 (formerly NFPA 484 and NFPA 654) — Combustible dust

NFPA 484 was the metals-dust standard; NFPA 654 was the chemical-process dust standard; in 2025 both were consolidated into NFPA 660 as the unified US combustible dust standard. Pure clay dust and pure silica dust are not combustible — they cannot sustain a flame propagation through the dust cloud. However, modern ceramic body formulations frequently include organic binders (polyvinyl alcohol, carboxymethyl cellulose, starch), deflocculants (sodium silicate, soda ash), or paper-pulp plasticisers. Any of these can shift the dust classification to combustible. Lithium-bearing flux additives — increasingly used in low-temperature porcelain bodies — also raise the dust hazard rating because lithium-bearing dust is moderately combustible. The recommendation: every ceramic plant duct project should commission a project-specific dust hazard analysis (DHA) under NFPA 660 before signing the duct contract. Cost of a DHA is in the order of AUD 15,000–25,000. Cost of a dust explosion in an unprotected duct main is in the order of AUD 5–15 million plus injury and prosecution.

AS/NZS 60079 series — Hazardous areas

The natural-gas burner manifold, fuel train, pilot lines and any natural-gas valve train inside the kiln building generate flammable-gas hazards under AS/NZS 60079. The standard requires hazardous-area zoning (Zone 0, Zone 1, Zone 2) around any potential gas release point, and certified equipment inside those zones. Any duct equipment — exhaust fan motor, position sensors, damper actuators, light fittings, control cabinets — inside a Zone 1 or Zone 2 area must be intrinsically safe (Ex i) or flameproof (Ex d). The duct itself is not a hazardous-area piece of equipment but the fan, motor and controls on the duct are. AS/NZS 60079 also covers any propane storage or liquefied petroleum gas vapouriser equipment at the plant.

ISO 13006 — Ceramic tiles: Definitions, classification, characteristics and marking

ISO 13006 is the global classification standard for ceramic wall and floor tile. It defines five groups based on water absorption and forming method — Group I (BIa, BIb), Group II (BIIa, BIIb), Group III — and lays down minimum performance requirements for breaking strength, surface hardness, frost resistance, chemical resistance and dimensional tolerance. ISO 13006 is not directly a ductwork standard but it is the standard that drives the firing temperature and atmosphere choice in tile plants. Porcelain tile (BIa, water absorption ≤ 0.5 per cent) requires higher firing temperatures (1200–1250 degrees Celsius) than glazed earthenware (BIII, water absorption > 10 per cent at 1050–1100 degrees Celsius), which in turn drives the kiln exhaust duct material specification.

AS 3958.1 — Ceramic tiles: Guide to the installation of ceramic tiles

AS 3958.1 covers the on-site installation of ceramic tile in the built environment — adhesive selection, substrate preparation, expansion joints, grouting. Not a manufacturing-plant standard, but it is the standard that the major plant operators (Brickworks, Boral, Caroma) reference in their commercial specifications and product warranties, and it is worth understanding for any HVAC engineer working on a tile-manufacturing project because it shapes the customer-quality requirements that feed back into the firing specification.

Safe Work Australia exposure standards — Respirable crystalline silica

The Safe Work Australia workplace exposure standard for respirable crystalline silica was lowered to 0.05 milligrams per cubic metre averaged over an eight-hour shift, harmonising with the US NIOSH recommended exposure limit. This is the single most important number for any duct engineer on a ceramic project. Capture velocities, transport velocities, final filter selection and air-change rates are all sized to keep workplace concentrations below this limit with a comfortable safety margin. Bricklaying, tile cutting and stonemasonry have also been subject to a national engineered-stone prohibition that took effect in 2024, and the regulatory environment around silica is tightening year on year.

Why galvanised fails in a ceramic plant

Galvanised steel duct is the default material for almost every Australian HVAC installation, and for very good reason — the cost, fabricability, durability and corrosion resistance for general air-handling are unmatched at the price point. In a ceramic plant, however, three failure modes overwhelm the galvanised coating.

Thermal volatilisation of zinc

Zinc melts at 419 degrees Celsius and starts to evaporate from the steel surface at temperatures well below that. The American Galvanizers Association recommends a maximum continuous service temperature of 200 degrees Celsius for hot-dip galvanised coating; many specifying engineers use 150 degrees Celsius as a practical limit for ductwork that must hold its zinc coating for fifteen years. Kiln exhaust temperatures even after dilution typically run 180–350 degrees Celsius — well above the safe galvanising window. The zinc coating volatilises off the steel and either redeposits on the cooler downstream duct as a white scale or is carried out the stack as visible white fume. The bare steel underneath then corrodes rapidly in the moist, slightly acidic kiln gas.

Silica dust abrasion

Crystalline silica dust at a transport velocity of 18–22 metres per second is one of the most abrasive media routinely handled in industrial ductwork. Quartz Mohs hardness is 7 versus a steel hardness of around 4. At elbow internal radii and at branch tee throats the dust wears through the duct wall by abrasion in a matter of years, not decades. Galvanised coating offers no abrasion resistance — the zinc layer is softer than the underlying steel and is the first thing to go. The standard solution is heavier-gauge spiral duct (1.5–2.0 mm wall) with abrasion-resistant inserts at the elbows. SBKJ supplies the heavier spiral on the SBTF-2020 with replaceable elbow inserts as a project option.

Hot hydrofluoric acid from glaze fume

Fluoride-bearing glaze frits are nearly universal in the modern tile and sanitaryware industry — fluoride is one of the cheapest and most effective fluxes available. The downside is that during firing some of the fluoride volatilises as gaseous hydrogen fluoride. At the cool end of the kiln exhaust the HF condenses with water vapour into liquid hydrofluoric acid at concentrations of 1–10 per cent. HF aggressively attacks the zinc coating of galvanised duct, then the underlying carbon steel, then 304 stainless. Only 316L stainless and acid-resistant lining systems offer reasonable service life in this environment.

Material selection summary table

For ease of reference here is the material selection matrix our engineers use when specifying duct for a tile, brick, ceramic or sanitaryware plant. Print it, mark it up for your site conditions, and use it as the starting point for the project specification.

• Raw clay receival / storage — galvanised G275 carbon steel rectangular or spiral, abrasion-resistant elbow inserts. Service temperature ambient.
• Clay preparation, dry mill, fettling room dust — galvanised G275 spiral, heavier gauge (1.2–1.5 mm) at elbows. Optional 304 stainless if body formula includes lithium or hygroscopic additives. Service temperature ambient to 40 degrees Celsius.
• Slip casting bench LEV, wet pug mill discharge — 304 stainless spiral due to wet-clay condensation. Service temperature ambient.
• Forming press hood — galvanised rectangular at 12–15 metres per second. Service temperature ambient.
• Drying chamber supply (clean side) — insulated galvanised rectangular, foil-faced mineral wool external insulation, vapour-resistant internal lining. Service temperature 100–110 degrees Celsius.
• Drying chamber return (humid side) — 304 stainless spiral or aluminium-magnesium duct. Service temperature 80–105 degrees Celsius continuous, 95 per cent RH.
• Kiln exhaust trunk (hot zone, kiln-side) — refractory-lined carbon steel, 50–75 mm castable lining, 5–8 mm steel shell. Service temperature up to 600 degrees Celsius continuous.
• Kiln exhaust trunk (downstream after dilution) — 309S or 310S austenitic stainless steel at 350–600 degrees Celsius; 304 stainless at 250–350 degrees Celsius; insulated galvanised below 200 degrees Celsius.
• Glaze spray booth ductwork — 316L stainless throughout. Service temperature ambient, but pH 4–6 wet aerosol.
• Kiln exhaust handling fluoride-bearing gas — 316L stainless after the wet scrubber; refractory-lined carbon steel before the scrubber.
• Cooling-air heat-recovery duct — insulated galvanised G275 or insulated 304 stainless. Service temperature 150–250 degrees Celsius.
• Sorting and packaging dust — galvanised G275 spiral. Service temperature ambient.
• Refractory plant exhaust (shuttle kiln, induction tundish heater, etc.) — refractory-lined carbon steel up to 600 degrees Celsius, then 310S stainless above. Service temperature up to 800 degrees Celsius downstream of primary cyclone.

Capture velocities and transport velocities

The Australian Industrial Ventilation Manual (drawing on the ACGIH Industrial Ventilation handbook) defines minimum capture velocities for industrial dust sources. For a ceramic plant the key numbers are as follows.

• Tipper grizzly, raw clay receival — capture 1.0–1.5 m/s at the source; transport 18–20 m/s in the spiral main.
• Conveyor transfer point — capture 2.0–2.5 m/s at the gap; transport 18–20 m/s.
• Bag-tipping station — capture 1.0 m/s at the bag mouth; transport 18 m/s.
• Ball mill feed hopper — capture 1.0–1.5 m/s at the inlet; transport 18 m/s.
• Dry-press feeder shoe — capture 2.0–3.0 m/s at the feeder mouth; transport 20–22 m/s.
• Fettling table, hand finishing — capture 0.75–1.0 m/s at slot hood 300 mm from the workpiece; transport 18 m/s.
• Glaze spray booth (downdraught) — face velocity 0.5–0.75 m/s across the grille area; transport 8–12 m/s.
• Kiln exhaust stack (after dilution) — face velocity at the gas-takeoff slot 15–25 m/s; transport in the main 12–18 m/s.
• Refractory plant burner exhaust — face velocity at the burner take-off 20–30 m/s; transport 15–20 m/s.

These are guidance numbers. Project-specific capture velocities are calculated from the source geometry, the contaminant settling velocity, and the cross-draught conditions in the workroom. AS 1668.2 industrial tables provide the regulatory minima.

Acoustic specification

Industrial workroom NC-50 is the typical noise design criterion for a brick, tile or refractory plant — equivalent to 60–65 dB(A) at the operator station. Most of the noise is generated by the production equipment itself (presses, pug mills, packaging conveyors), not by the duct system, but oversized fans on undersized duct runs can add 5–10 dB(A) easily if duct velocity is allowed to drift above 15 metres per second in the main supply and return paths.

If the plant has an attached office building, sales showroom, customer-tour gallery (common at Brickworks Austral plants and at Caroma's Eltham facility) or quality-lab area, the design target for these spaces drops to NC-40 or NC-35, equivalent to 45–50 dB(A). The standard solution is in-line packaged attenuators of 1.2–2.4 metre length on the supply main feeding the office zone, with internal acoustic lining (typically melinex or polyester-faced glass fibre, 25 mm thickness) on the duct between attenuator and diffuser to control regenerated noise. SBKJ's acoustic duct lining guide covers the detail. See our companion piece on acoustic HVAC duct lining and attenuator design for the calculation worksheet.

Refractory ceramics — the extreme end of the envelope

Refractory ceramic plants — those producing alumina, silica, magnesia, zirconia, silicon carbide and aluminosilicate fibre products — sit at the most demanding end of the ceramic industry envelope. Firing temperatures of 1500–1800 degrees Celsius are routine, and some specialty operations exceed 2000 degrees Celsius. The duct specifications scale accordingly.

Vesuvius Australia at Geelong is the largest refractory manufacturer in the country and supplies linings to the steel industry (BlueScope at Port Kembla, InfraBuild Newcastle and Whyalla), the glass industry (Owens-Illinois at Penrith and Adelaide, Viridian at Dandenong, ACI Brisbane), the cement industry (Adelaide Brighton, Boral Cement, Cement Australia) and the aluminium industry (Tomago Aluminium, Boyne Smelters at Gladstone). The Geelong plant runs shuttle kilns and tunnel kilns at temperatures that put the kiln-takeoff duct well above 1000 degrees Celsius — the only duct material that survives is 310S austenitic stainless steel in heavy gauge, or refractory-lined carbon steel with a 100 mm lining thickness.

Calderys Australia operates a similar refractory product range. Smaller specialty refractory operations exist around Sydney and Brisbane serving the foundry, glass and ceramics sectors directly.

For refractory plant duct specification we recommend the project engineer commission a CFD analysis of the kiln-takeoff thermal profile before placing the duct order. The cost of a CFD study (AUD 30,000–50,000) is recovered many times over by avoiding a costly retrofit when the as-built duct fails at the first six-month inspection. SBKJ can supply the duct in the materials specified, including 310S stainless and refractory-lined carbon steel; we do not supply the lining design or castable refractory itself — that is a job for a specialty refractory contractor.

Sanitaryware ceramic plants — the cleanest end of the ceramic industry

Sanitaryware ceramic — toilets, basins, urinals, bidets — is fired from slip-cast vitreous china, a clay-feldspar-silica body fired to 1180–1220 degrees Celsius until it vitrifies. Caroma's Eltham plant in Victoria is the largest local operation; the Sydney sites round out the national capacity. Roca Australia and Kohler Australia import most product but maintain commissioning, repair and after-sales depots locally.

The sanitaryware duct environment has three distinguishing features. First, slip casting bench LEV is a wet-air capture problem, not a dry-dust problem — the air at the benchline is heavy with fine atomised water and dissolved clay. Standard solution is 304 stainless spiral duct with sloped drain points every six metres. Second, the glaze line on sanitaryware uses a thinner waterfall-style glaze rather than the heavy curtain-applied glaze used on porcelain wall and floor tile, but the corrosion environment in the booth duct is similar — 316L stainless is the standard. Third, the firing kiln is a roller hearth or tunnel kiln at vitrification temperature, and the duct specification mirrors the porcelain tile case — refractory-lined carbon steel at the kiln, 310S or 304 stainless downstream.

Caroma's quality programme is exacting — they sell into the Australian commercial-bathroom market against premium European competition and the warranty exposure on a Caroma toilet is multi-decade. The duct specification on a new Caroma kiln line gets the same engineering rigour as the body formulation itself.

Roof tile plants — terracotta and concrete

Roof tile splits into two product families with distinct ductwork implications. Terracotta roof tile is a fired ceramic product — fired clay with a glaze or natural-clay finish, fired in tunnel or shuttle kilns at 1000–1150 degrees Celsius. The duct specification is essentially the same as a brick plant: refractory-lined kiln exhaust, galvanised dust mains, glaze-line stainless. Brickworks operates terracotta roof tile under the Bristile and Monier brands at the Wacol and Rosehill plants.

Concrete roof tile is not a fired product — it is a vibrated, extruded and steam-cured concrete tile that hardens at 60–80 degrees Celsius in a curing chamber. The ductwork is much simpler — insulated galvanised supply and return on the curing chambers, standard galvanised dust LEV on the mix-prep area, no high-temperature kiln stage at all. Concrete roof tile is produced by Boral, Monier (Brickworks), CSR PGH and several smaller operations nationally.

Project case profile — a mid-size brick plant retrofit

To make the specification concrete, here is a project profile drawn from our recent experience supplying duct fabrication equipment to an Australian brick plant retrofit. Plant capacity 60 million bricks per year, one tunnel kiln at 1100 degrees Celsius, one shuttle kiln for specialty product at 1180 degrees Celsius, conventional clay-prep with two pan mills and a wet pug.

• Clay-prep dust main — galvanised spiral, 1.2 mm gauge, 600 mm diameter, transport velocity 20 m/s, total length 240 metres. Discharge through cyclone precleaner to a 24-bag reverse-pulse fabric filter. Designed for RCS less than 0.05 mg/m³ at any workroom monitoring station.
• Pug mill and forming-line LEV — galvanised spiral, 1.0 mm gauge, 300 mm diameter, transport velocity 15 m/s, total length 60 metres.
• Drying tunnel supply duct — insulated galvanised rectangular, 1500 × 800 mm cross-section, 25 mm external mineral wool insulation, foil-faced. Service 105 degrees Celsius.
• Drying tunnel return duct — 304 stainless spiral, 800 mm diameter, 1.0 mm gauge. Service 95 degrees Celsius at 90 per cent RH.
• Tunnel kiln exhaust trunk — refractory-lined carbon steel, 1200 mm internal diameter, 75 mm castable refractory lining, 6 mm steel shell. Service 350–550 degrees Celsius. Total length 45 metres to the stack induced-draught fan.
• Shuttle kiln exhaust — refractory-lined carbon steel as above, 900 mm internal diameter. Service intermittent, peak 600 degrees Celsius.
• Glaze line booth duct — 316L stainless spiral, 600 mm diameter, 1.0 mm gauge. Service ambient, pH 5 wet aerosol.
• Heat recovery duct (kiln cooling to dryer) — insulated galvanised G275 rectangular, 1200 × 600 mm. Service 200 degrees Celsius.
• Sorting and packaging LEV — galvanised spiral, 0.8 mm gauge, 250 mm diameter, transport velocity 18 m/s.

Total duct fabrication for the project: 2,800 metres of galvanised spiral, 380 metres of 304 stainless spiral, 180 metres of 316L stainless spiral, 95 metres of refractory-lined carbon steel exhaust trunk, 320 square metres of insulated galvanised rectangular, and the associated fittings, flanges, dampers and access doors. The duct fabrication contract value was in the AUD 750,000–950,000 range depending on the material market at order date. The plant operator's payback calculation was driven by the avoided downtime cost of the previous galvanised-throughout system, which had been losing zinc coating on the kiln exhaust at a rate that triggered duct replacement every five years; the refractory-lined upgrade was expected to deliver a 20-year service life.

How SBKJ machines fit ceramic-plant duct fabrication

SBKJ Group, headquartered in Box Hill North Victoria, manufactures HVAC duct fabrication machinery — auto duct lines, spiral tubeformers, plasma-cut fitting machines, TDF flange roll formers and welding equipment — that is used by HVAC fabricators across Australia to build the duct systems specified above. For a ceramic-plant project our recommended machine configuration is as follows.

SBAL-V auto duct line with stainless-steel option

The SBAL-V is SBKJ's flagship auto duct line. It runs coil up to 1.5 mm thickness and 1550 mm width, processes galvanised, aluminised, 304 stainless and 316L stainless coil, and produces rectangular duct from 200 × 200 mm up to 1500 × 1500 mm in TDF or angle-flange configuration. The stainless-steel option upgrades the tooling, drive train and inline lockformer for the more demanding stainless coil characteristics. For a ceramic plant the SBAL-V in stainless option is the workhorse — every rectangular trunk in the drying loft, the heat-recovery duct, the kiln-side ductwork after the temperature drops below 250 degrees Celsius, and the office HVAC for the plant administration block can be produced on a single SBAL-V. See our machine catalogue for the full specification or our SBAL-V versus SBAL-III comparison for the upgrade logic.

SBTF-2020 spiral tubeformer

The SBTF-2020 is SBKJ's heavy-duty spiral tubeformer for round duct from 100 mm up to 2000 mm diameter, coil thickness up to 2.0 mm. For a ceramic plant the SBTF-2020 produces all the spiral dust mains in the clay-prep area, all the spiral exhaust trunks at the drying loft return, the heat-recovery round duct and the glaze-line stainless ducting. The machine takes galvanised, stainless and aluminium-magnesium coil interchangeably; the toolset change between materials is a 20-minute operation. For abrasion-duty duct the SBTF-2020 can run heavier-gauge spiral (1.5–2.0 mm) at full diameter, and an optional refractory-lined sleeve setup is available for the hot-end kiln-exhaust duct where refractory-lined construction is specified. Read more in our spiral duct forming guide.

TIG seam welder for high-temperature exhaust trunks

Above 600 degrees Celsius continuous service the duct moves to welded 309S or 310S stainless construction. SBKJ supplies inline TIG seam welding stations integrated with the SBAL-V or as standalone units. TIG produces a fully sealed, leak-tight stainless seam suitable for refractory-lined kiln-exhaust ductwork and for any duct where a TDF or angle-flange joint would fail at temperature. See our welding methods for HVAC duct fabrication for the joint-design detail.

Plasma cutting cell for fittings

Every ceramic-plant duct system involves dozens of bespoke fittings — kiln-side takeoffs, refractory-line transitions, glaze-booth manifolds, dust-main tees. SBKJ's plasma-cut fittings cell unrolls and cuts elbow gores, branch tees, transition pieces and reducers in any material the SBAL-V handles. The cell is the same equipment used by every major Australian HVAC fabricator who supplies the ceramic industry. Our fittings fabrication guide walks through the design rules.

Refractory-lined duct option

SBKJ does not manufacture refractory lining material — that is a specialty for refractory engineering contractors. What we do supply is the structural steel shell of the refractory-lined duct, fabricated on the SBAL-V or SBTF-2020 in heavier carbon-steel coil (3–8 mm depending on diameter and pressure class) with the integrated anchor studs welded to the inside face for the castable refractory key. The customer's refractory contractor then applies the castable lining or installs the refractory blanket on site. This split-supply approach is the standard model for refractory-lined ductwork in Australia and lets the fabricator and refractory contractor each operate within their expertise.

Procurement timeline for a ceramic-plant duct project

From the procurement-manager perspective, a ceramic-plant duct project runs to a different timeline than a commercial-building HVAC project. The kiln itself is typically a long-lead European-built unit on a 12–18 month delivery; the duct contract usually follows the kiln by 3–6 months once the as-installed temperature profile and stack flow rates are known. The duct fabricator's role is therefore on the critical path of plant commissioning, not on the critical path of plant construction.

• Month 1–3 — kiln supplier provides the as-built thermal and flow data on the exhaust stack; mechanical consultant develops the duct schematic and material schedule; dust hazard analysis commissioned under NFPA 660 if organic binders or lithium flux are in the body formulation.
• Month 4–6 — duct fabrication tender to two or three pre-qualified fabricators with itemised landed-cost worksheet on AS/NZS 4254.2 standard joint detail; refractory lining specification frozen with the refractory contractor; long-lead 316L stainless coil ordered if not stocked.
• Month 7–10 — duct fabrication; factory acceptance inspection on the refractory-lined trunks; ISPM-15 crating for delivery to site.
• Month 11–12 — site installation, hanger detail, flange-up and access-door fitting; pressure testing to AS/NZS 4254.2 leak class.
• Month 13–14 — commissioning and balancing; first-fire of the kiln; iterative tuning of the exhaust induced-draught fan against the actual kiln operating profile.

The duct fabricator's relationship with the plant operator is decade-long. A ceramic plant runs the same duct for 15–25 years and replaces sections as wear, corrosion or process upgrade dictates. The fabricator who builds a quality original installation typically wins every replacement contract for the next two decades.

Common procurement mistakes on ceramic-plant duct

From the field we see the same handful of mistakes repeatedly. Avoid these and the project will run smoothly.

• Specifying galvanised throughout to save the stainless premium. Saves 15–25 per cent on the duct package, costs 100–200 per cent in early replacement of the high-temperature and glaze-line sections within five years.
• Sizing transport velocity from the brochure number. The AS 1668.2 minimum and the actual operating velocity are not the same number. Always calculate transport velocity from the as-built dust loading and the operating flow rate, not from the design flow rate at the brochure assumption.
• Skipping the dust hazard analysis. Pure clay dust is not combustible, but organic binders and lithium flux change the picture. A AUD 20,000 DHA up front is cheap insurance against a multi-million-dollar explosion claim later.
• Forgetting the AS/NZS 60079 hazardous-area zoning. The natural-gas burner manifold is a Zone 1 area whether you draw the zone or not. Specifying a standard non-Ex fan motor in that zone is a regulatory failure that the plant safety inspector will find.
• Ignoring the heat-recovery opportunity. Modern ceramic plants achieve 15–25 per cent gas savings by recovering kiln cooling air into the dryers. The duct retrofit cost is modest and the payback is 18–30 months at current gas prices. Original-build ceramic plants in Australia overwhelmingly miss this opportunity and pay for it for the next twenty years.
• Pricing the refractory lining separately from the duct shell at quotation stage. Almost guaranteed to produce a scope gap at installation. The duct fabricator and the refractory contractor must coordinate at the engineering stage — joint kick-off meeting, joint shop-drawing review, joint inspection on the first refractory pour.
• Choosing the cheapest acoustic attenuator. If the plant has an attached office, showroom or customer-tour gallery, the difference between a NC-50 industrial environment and an NC-40 office environment is 10 decibels — that's perceived as half the noise. A standard in-line packaged attenuator at the office-zone takeoff pays itself back in human-factors terms within months.

A note on local content and procurement preference

Several Australian state governments operate local-content preference schemes on capital projects above a notified threshold. The Victorian Industry Participation Policy, the Building Equity Strategy in New South Wales, and similar Queensland and Western Australian schemes all give weighting to local fabrication and local supply on major project tenders. Ceramic plants — even though they are not government projects — frequently sit inside government-backed industrial estates or claim related grants, and the local content question becomes part of the procurement decision matrix.

SBKJ Group operates from Box Hill North Victoria with a local engineering and sales team. Australian duct fabricators who use SBKJ duct fabrication equipment are local fabricators by every reasonable definition of the term — they employ local tradespeople, hold local ABN registrations, pay local GST, and operate under Australian work-health-and-safety law. The duct itself is fabricated in Australia for delivery to the Australian project. Plant operators looking to demonstrate local content on a ceramic-plant duct project are well-served by sourcing from the SBKJ-equipped fabricator panel.

What to ask your duct fabricator

Before signing a duct fabrication contract for any ceramic plant project, the procurement manager should have clear answers to the following questions. These are the questions we recommend our customers ask their fabricator, whether or not the fabricator is using SBKJ equipment.

• What material has been specified for the kiln-exhaust trunk above 250 degrees Celsius? If the answer is galvanised, the spec is wrong.
• What is the AS/NZS 4254.2 pressure class and leak class for the dust main? HP class with leak class C is typical for a brick-plant clay-prep main.
• Has a dust hazard analysis been commissioned under NFPA 660? If the body formula uses organic binder, lithium flux or paper-pulp plasticiser, the DHA is essential.
• Has the AS/NZS 60079 hazardous-area zone been drawn on the burner manifold area? Have intrinsically safe motors and sensors been specified inside the zone?
• What is the test certificate for the 316L stainless duct in the glaze line? Mill certificates traceable to a recognised steel mill are standard.
• Who is the refractory contractor for the refractory-lined sections? Have the duct fabricator and refractory contractor jointly reviewed the as-built shop drawings?
• What is the spare-parts package for the duct system — replacement gaskets, access door seals, expansion-joint elements? A one-year wear-parts kit is industry standard.
• What is the warranty period and what triggers the warranty start — date of shipment, date of installation, or date of first fire?

Our companion HVAC duct machine buyer's checklist provides the equivalent 47-point checklist for the machine purchase itself, which is upstream of the duct fabrication contract.

How this guide connects to our other industry articles

Ceramic manufacturing sits inside a broader industrial-ventilation family that includes glass, cement, foundry, steel mill and refractory production. The duct engineering shares more than it differs. We have published companion guides for each of these sectors that share the same engineering review and the same case-driven structure.

• Cement plant HVAC duct guide — kiln preheater duct, clinker cooler, raw mill, finish mill dust mains. Closely related to ceramic but the temperatures are higher and the dust load is heavier.
• Glass manufacturing HVAC duct guide — float-glass tank exhaust, container-glass furnace, fibre-glass forming, sheet-glass cutting. The glass industry shares the high-temperature exhaust challenge with ceramic.
• Steel mill and smelter HVAC duct guide — BOF off-gas, EAF dust capture, reheat furnace exhaust. The ultimate high-temperature duct application; refractory lining and stainless construction throughout.
• Foundry and iron-and-steel casting HVAC duct guide — pouring-floor LEV, cupola exhaust, induction furnace fume capture, fettling dust. Shares the silica dust capture problem with ceramic.
• AS 1668.2 Australian ventilation code reference — the parent standard that drives the design for all of the above.

Closing thoughts

A ceramic plant is one of the most demanding industrial environments to specify HVAC ductwork for, and one of the most rewarding when the specification is done correctly. The dust, the heat and the acid fume are all manageable with the right material choices and the right engineering process. The biggest leverage is in the upfront engineering — the dust hazard analysis, the material-selection matrix, the AS/NZS 60079 hazardous-area zoning, the kiln-exhaust thermal profile. Time spent on these activities at the start of the project saves multiples in retrofit and downtime cost over the plant life.

If you are specifying duct for a brick, tile, sanitaryware or refractory plant project in Australia and you would like an SBKJ engineer to review your specification informally before tender, we offer that service to plant operators and mechanical consultants at no cost. The phone call takes 30–45 minutes and we will tell you what we would do differently. We have no commercial relationship with any plant operator other than as a duct fabrication machinery supplier — we sell the machines that build the duct, not the duct itself — so the review is genuinely independent.

Send us your project schematic, your kiln exhaust temperature profile, and your body formulation, and we will turn around a review note within five working days. Contact our Box Hill North office at sales@sbkjduct.com or on +61 435 074 994.

Ask an SBKJ engineer about your ceramic-plant duct project →

FAQ

What duct material should a tile or brick plant use for kiln exhaust?

For kiln exhaust above 250 degrees Celsius galvanised steel fails through zinc volatilisation, thermal shock and silica abrasion. The standard solution is refractory-lined carbon steel duct up to about 600 degrees Celsius, or 309S / 310S stainless steel for sustained higher-temperature service. The glaze line where hydrofluoric acid fume can condense requires 316L stainless steel. SBKJ supplies the spiral mains and rectangular trunks in 316L stainless or refractory-lined carbon steel via the SBAL-V stainless option and the SBTF-2020 spiral tubeformer.

Is clay dust combustible under NFPA 660 (formerly NFPA 484)?

Pure clay and silica dust from forming are not combustible. However, many modern ceramic body formulations include organic binders, deflocculants and starch-based plasticisers that shift the dust class. Any plant using organic additives, paper-pulp binders or lithium-bearing flux compounds should commission a dust hazard analysis under NFPA 660 before specifying the dust extraction main. SBKJ supplies explosion-vented spiral mains and abrasion-resistant duct where required.

What is the silica dust exposure limit in Australia for a brick plant?

The Safe Work Australia workplace exposure standard for respirable crystalline silica was lowered to 0.05 milligrams per cubic metre averaged over an eight-hour shift in 2020, harmonising with the US NIOSH recommended limit. Brick and tile plants with clay preparation, dry grinding, slip casting or polishing operations require capture velocities of 1.0–2.5 metres per second at the source and transport velocities of 18–22 metres per second in the spiral main, with HEPA-grade filtration on any duct discharging back into general workroom air.

What standards apply to ceramic plant ductwork in Australia?

The primary code is AS 1668.2 for mechanical ventilation. Kiln combustion safety follows NFPA 86. Natural-gas burner areas are classified under AS/NZS 60079. Tile classification follows ISO 13006 and installation references AS 3958.1. Dust hazard analysis follows NFPA 660. Most Australian plants build to AS 1668.2 for the ventilation main, AS/NZS 4254.2 for the duct fabrication itself, and a project-specific blend of NFPA 86 and AS/NZS 60079 for the kiln and burner zones.

Who are the major Australian brick and tile manufacturers?

Brickworks Limited (ASX:BKW) is the largest, operating 14+ plants under Austral Bricks, Bowral Bricks, Daniel Robertson Bricks in Tasmania, Nubrik in Victoria, plus Bristile and Monier roof-tile brands. CSR Limited (ASX:CSR) owns PGH Bricks. Boral has historic plants at Bunbury, Cardup, Geelong, Murrumbeena and Sydney. Sanitaryware is dominated by Caroma at Eltham, alongside Roca Australia and Kohler Australia. Tile distribution is led by Beaumont Tiles and National Tiles (both Reece-owned), Italtile, Earp Bros and Tile Importer. Refractory ceramics are supplied by Vesuvius Australia at Geelong and Calderys Australia.