Agricultural Machinery, Tractor, Harvester, Seeder, Sprayer & Farm-Implement Manufacturing HVAC Duct Guide

1. Why agricultural machinery manufacturing HVAC is its own engineering discipline

Agricultural machinery manufacturing is one of the most diverse heavy-fabrication environments in the Australian industrial economy, and the HVAC ductwork that serves it has to span an unusually wide range of process hazards inside a single building. Within one tractor, header or implement plant — a Goldacres sprayer line in Ballarat VIC, a Kelly Engineering disc-chain shop in Booleroo SA, a Gessner tillage works in the Toowoomba QLD region, or a John Deere Australia assembly and parts operation — you can find a structural welder laying multi-pass MIG weld on a 20 mm chassis plate in one bay, a CNC plasma table cutting boom sections in the next, a grit-blast room stripping millscale off a header front, a downdraft spray booth applying two-pack polyurethane topcoat under isocyanate control, a powder-coat line curing seeder tynes at 200 degrees C, a fibreglass laminating bay laying up a cab roof in styrene-rich polyester resin, a machining cell turning axle shafts under flood coolant, and a final-assembly hall fitting hydraulics and diesel engines. Each of those operations has its own characteristic dust load, fume chemistry, ignition risk, hazardous-area zoning and material specification. The ductwork that ties them together is not a commodity item; it is a process-engineering problem that touches AS/NZS 1554 welding fume, AS 1940 flammable-liquid paint, AS 3957 abrasive-blasting dust, AS/NZS 60079 explosive-atmosphere zoning, NFPA 33 spray application, and the SafeWork Australia workplace exposure standards for a dozen contaminants — all sitting inside one NCC Class 8 industrial envelope.

This guide writes against the full breadth of the Australian agricultural-machinery sector as it exists in 2026. The market has two faces. The first is the global original-equipment manufacturers operating in Australia — John Deere Australia, Case IH and CNH, AGCO and Kubota Australia — whose Australian footprint spans distribution, regional assembly, parts manufacturing, dealer-support fabrication and, increasingly, local engineering of harvesting fronts, headers and platforms suited to Australian broadacre conditions. The second, and the larger fabrication-intensity story, is the Australian-owned implement and equipment builders. Goldacres in Ballarat VIC builds self-propelled and trailing crop sprayers, with a heavy boom-welding operation and one of the more demanding spray-and-bake paint lines in regional Victoria. Croplands and Hardi Australia build sprayers. Gessner and Hayes build tillage and ground-engaging implements in the Toowoomba and Brisbane QLD belt. Kelly Engineering in Booleroo SA builds the disc-chain tillage systems it exports across the world from a regional South Australian base. K-Line Ag, Boss Engineering, Multifarm, Serafin, Trufab, Norseman, Reekie, McIntosh, Howard Australia and Connor Shea build seeders, headers, air carts, tillage and a broad span of broadacre equipment across regional NSW, the WA wheatbelt, Shepparton VIC and Adelaide SA.

Across this entire sector, agricultural-machinery ductwork must survive five simultaneous demands. Abrasion resistance — structural weld-fume, plasma and laser plate-cutting dust, and grit-blast reclaim duct all carry hard metallic and mineral particulate at 18 to 25 m/s that erodes thin-gauge duct at every elbow. Flammable-vapour integrity — the paint-booth and bake-oven exhaust carries atomised solvent and isocyanate that must be contained in a hermetic, conductive, AS 1940 and NFPA 33 compliant duct. Combustible-dust deflagration resistance — powder-coat overspray, fine metallic cutting dust and organic blast dust are explosible under AS/NZS 60079 and the NFPA 68/69 framework. Corrosion and contaminant resistance — Cr(VI) from stainless welding, ozone from aluminium GMAW, styrene from fibreglass lamination, and acid from any pickling stream attack ordinary galvanising. And occupational-exposure compliance — every weld hood, every booth and every blast room has to hold the operator's breathing-zone air below a workplace exposure standard, with isocyanate at 0.02 mg/m3 and manganese at 1 mg/m3 driving the tightest numbers. Each is manageable in isolation. Together they explain why a generic commercial fabricator treating an ag-machinery plant as just another industrial job loses money on the first project and walks away from the second.

This guide walks every major process zone in an agricultural-machinery plant and explains what changes about the ductwork. We start with the regulatory backbone, then map the plant section by section — structural welding, plate cutting, machining, surface preparation, painting, powder coating, fibreglass, assembly and the emerging electric and autonomous-ag work — then close with the SBKJ machine configuration that gives an Australian fabricator the production envelope to serve this market from Box Hill North VIC across the country.

2. The Australian regulatory stack — AS 1668.2, AS 4254, AS/NZS 1554, AS 1940, AS 3957, AS/NZS 60079, NFPA 33, AS 1375, AS 4024, AS/NZS 1715/1716

Agricultural-machinery manufacturing HVAC sits at the intersection of more than two dozen overlapping standards and codes. Ignoring any one of them is a notice of non-compliance from SafeWork Australia, the state EPA, or both, waiting to happen. The standards stack splits into building-code and ventilation compliance, occupational-health exposure compliance, welding-fume control, flammable-liquid and spray-application safety, abrasive-blasting dust safety, hazardous-area electrical compliance, combustible-dust safety, gas-fired-oven safety, and machinery-safety and respiratory-protection.

2.1 AS 1668.2 — mechanical ventilation for buildings

AS 1668.2 is the umbrella mechanical-ventilation standard for Australia, and AS 1668.1 covers the fire and smoke control of air-handling systems. Agricultural-machinery plants fall under NCC Class 8 industrial occupancy. AS 1668.2 sets the dilution-ventilation method for keeping airborne contaminants below their workplace exposure standard, and it sets minimum extract rates for welding, grinding, painting, machining and similar operations. In an ag-machinery plant the building seldom gets close to the minimum on dilution alone — localised exhaust ventilation at each weld station, cutting table, booth and blast room drives total exhaust well above the building-volume figure. Where AS 1668.2 matters most is the make-up air requirement: every cubic metre extracted from a weld hood, a spray booth, a blast room or a machining cell must be replaced by tempered, filtered, controlled-velocity supply air, holding the fabrication hall at neutral-to-slightly-negative pressure relative to the paint and final-assembly areas so that solvent and fume do not migrate into clean zones.

2.2 AS 4254 — sheet metal duct construction

AS/NZS 4254.1 (sheet metal) and AS/NZS 4254.2 (flexible) govern duct construction across the normal pressure ranges — low pressure (up to 500 Pa), medium pressure (up to 1000 Pa) and high pressure (up to 2500 Pa). Most ag-machinery supply air, general extract, weld-fume LEV, paint-booth exhaust and machining oil-mist duct sit inside AS 4254 ranges, although the gauge selection runs heavier than commercial work because of the abrasion and the velocity. The bake-oven high-temperature riser runs beyond ordinary AS 4254 construction and uses purpose-engineered high-temperature stainless; AS 4254 picks up again on the cool side downstream of the oven.

2.3 AS/NZS 1554.1, 1554.6, 1554.7 — structural steel, stainless and aluminium welding

The AS/NZS 1554 series governs welding of the structures that an ag-machinery plant fabricates, and it is the standard that the welding-fume LEV is designed to support. AS/NZS 1554.1 covers welding of steel structures — the mild and high-strength steel of chassis, frames, booms, header fronts and seeder bars, welded by GMAW, FCAW and submerged arc. AS/NZS 1554.6 covers welding of stainless steel — food-contact augers, trim and any stainless componentry, where hexavalent chromium becomes the controlling fume. AS/NZS 1554.7 covers welding of aluminium — boom sections, panels and lightweight structures, where ozone and aluminium oxide dominate. The fume chemistry differs across the three, and the LEV duct material and the dust collector both have to be specified for the worst-case duty (Cr(VI) hermetic and cleanable) even when most of the shop's work is mild steel.

2.4 AS 1940 — storage and handling of flammable and combustible liquids

AS 1940 governs the storage and handling of flammable and combustible liquids, and it is the controlling standard for the paint line. The solvent-borne primers, two-pack polyurethane topcoats, thinners, isopropanol and acetone in an ag-machinery paint shop are Class IB and Class IC flammable liquids; their bulk storage, day-tanks, mixing room, gun-wash and the spray booth itself are all governed by AS 1940 for bunded containment, segregated storage, dedicated ventilation and ignition-source control. The spray-booth interior is a hazardous area where atomised solvent forms a flammable atmosphere, and AS 1940 ties directly into AS/NZS 60079 for the electrical-equipment selection and into NFPA 33 for the spray-application engineering.

2.5 AS 3957 — dust hazard from abrasive blasting

AS 3957 governs walls, floors and ventilation for abrasive-blasting operations and is the controlling standard for the grit-blast and shot-blast surface-preparation room. It sets the through-room ventilation velocity for operator visibility and dust clearance, the construction of the enclosure, and the dust-extraction and abrasive-reclaim arrangement. The abrasive (garnet, chilled iron grit, steel shot, aluminium oxide) plus the blasted millscale and old coating create very high dust loadings, and where the abrasive or substrate carries silica, respirable crystalline silica at 0.05 mg/m3 becomes the controlling exposure. AS 3957 is reinforced by AS 1668.2 for the WES dilution and by AS/NZS 1715/1716 for the blaster's air-supplied helmet.

2.6 AS/NZS 60079 — explosive atmospheres, the dominant electrical-safety standard

AS/NZS 60079 is the hazardous-area-classification standard, and an ag-machinery plant triggers it at the paint line, the powder-coat booth, the fibreglass bay and every combustible-dust collection system:

• Zone 1 (gas/vapour): The spray-booth interior during spraying, the paint mixing room, the gun-wash station, the fibreglass spray-up and gelcoat bay, the acetone and IPA clean-down stations.
• Zone 2 (gas/vapour, unlikely in normal operation): The general paint-shop area surrounding the booth, the general fibreglass laminating area.
• Zone 20 (continuous explosible dust): The interior of a powder-coat reclaim collector, the interior of a combustible-dust transport main above settling velocity.
• Zone 21 (occasional explosible dust): The powder-coat booth interior, the immediate area around a combustible-dust transfer point.
• Zone 22 (unlikely release, short duration): The general area around the powder-coat booth and the fine-metallic dust collector.

AS/NZS 60079 drives Ex-rated electrical-equipment requirements for fans, motors, instrumentation, duct-mounted sensors and lighting in or near the affected zones. Combustible-dust and flammable-vapour ductwork must be conductive, continuously bonded with conductive flange gaskets, externally bonded to the building earth grid, and verified at commissioning with documented earth-resistance below 1 ohm to ground at every section.

2.7 NFPA 33 — spray application using flammable materials

NFPA 33 is the US National Fire Protection Association standard for spray application using flammable or combustible materials, referenced extensively by Australian paint-line designers and insurers alongside AS 1940. NFPA 33 sets the spray-booth ventilation rate, the booth-to-conveyor and booth-to-oven interlocks, the electrical-area classification of the booth and its surrounds, the deflagration-protection and the fire-suppression requirements for a spray operation. For an ag-machinery paint line applying two-pack polyurethane to large equipment, NFPA 33 (together with NFPA 68 deflagration venting and NFPA 69 explosion prevention) is the engineering reference that sets the booth extract rate, the duct-velocity floor that keeps deposited overspray from accumulating in the exhaust duct, and the cleaning-access provisions on the exhaust main.

2.8 AS 1375 — industrial fuel-fired appliances and the bake oven

AS 1375 (the SAA Industrial Fuel-Fired Appliances Code) governs the gas-fired bake oven that cures the wet-paint topcoat and the powder-coat. The oven must be purged of any combustible atmosphere before burner light-off, monitored for flame failure, and exhausted through a dedicated high-temperature riser that does not share with general extract. The oven exhaust carries cure off-gas, residual solvent and combustion products, and the duct transitions from high-temperature aluminised or stainless at the oven to ordinary construction downstream of the cooling section. AS 1375 ties into AS 1530.4 for the fire rating of the oven-exhaust penetrations through fire compartments.

2.9 AS 1530.4 and AS 1682 — fire resistance and fire dampers

AS 1530.4 covers fire-resistance testing of building elements including fire-rated ductwork penetrations, and AS 1682 covers fire and smoke dampers. In an ag-machinery plant this matters where the paint-shop, the bake oven and the dust-collection systems penetrate fire compartments between the fabrication hall, the paint shop, the office and the warehouse. The duct penetration is typically rated at 250 degrees C / 2 hour fire integrity, with fire dampers complying with AS 1682 and the surrounding wall or floor assembly meeting the fire-resistance level called by the building's NCC approval.

2.10 AS 4024 — safety of machinery

AS 4024 (the safety-of-machinery series) governs the guarding, access and isolation of the fabrication machinery and the dust-collection and air-handling plant, and it sets the inspection-and-access provisions that the ductwork must support — access ports sized for inspection and cleaning, lockable isolation on fans and dampers, and guarding of any duct-mounted moving part. The duct designer reads AS 4024 alongside AS 4254 to size the access ports and to detail the maintenance-access strategy for the weld-fume, paint-booth and dust-collection duct.

2.11 NFPA 68 and NFPA 69 — deflagration venting and explosion prevention

NFPA 68 (deflagration venting) and NFPA 69 (explosion prevention systems) are the engineering references for protecting combustible-dust collection systems — the powder-coat reclaim, the fine-metallic plasma and laser cutting dust, and any organic blast dust. They set the vent-panel sizing on the collector, the explosion-isolation-valve placement between the dust main and the collector, the chemical-suppression or flap-valve or rotary-valve isolation strategy, and the inerting and concentration-control practice. The isolation valve pre-trips on flame or pressure rise sensed in the collector, preventing flame propagation back up the duct main into the booth or the cutting table.

2.12 NCC Section J, ASHRAE 62.1 and heat recovery — energy and indoor air quality

NCC Section J sets the energy-efficiency requirements for the building services, and it bears directly on the make-up air for a high-extract ag-machinery plant. Every cubic metre extracted by the weld hoods, the booth and the blast room has to be replaced by tempered, filtered make-up air, and Section J pushes the designer toward heat recovery on that make-up stream — run-around coils, plate heat exchangers or thermal wheels recovering heat from the warm exhaust into the cold winter make-up, which in a regional Victorian or South Australian plant is a substantial energy saving. ASHRAE 62.1 informs the ventilation-for-acceptable-indoor-air-quality approach in the office, assembly and clean-work zones. The interaction of high process extract, Section J make-up-air tempering and heat recovery is one of the defining HVAC engineering challenges in a modern ag-machinery plant.

2.13 ISO 9001, ISO 14001 and ISO 45001 — quality, environment and safety management

ISO 9001 (quality), ISO 14001 (environment) and ISO 45001 (occupational health and safety) are the management-system standards that most established ag-machinery manufacturers operate, and they bear on the ductwork through documentation. ISO 14001 ties the dust-collection and paint-booth stack emissions to the state EPA licence; ISO 45001 ties the LEV performance to the breathing-zone air-sampling program and the WES; ISO 9001 ties every length of ductwork to its mill certificate, fabrication record, pressure-test and commissioning data. SBKJ supplies the foundation paperwork — mill certificate, pressure-test record, bonding verification and AS/NZS-compliant labelling — that the operator then integrates into the ISO management-system audit pack.

2.14 SafeWork Australia workplace exposure standards — the chemistry-driven sizing inputs

SafeWork Australia's workplace exposure standards (WES) are the regulatory inputs that drive LEV capture velocity and ductwork sizing across the plant. The ag-machinery-relevant standards are extensive:

• Welding fume (not otherwise classified): SafeWork Australia has lowered the recommended figure to 1 mg/m3 respirable and is trending toward removing any safe number — the controlling driver for structural weld-fume LEV across every chassis, boom, frame and header bay.
• Manganese: 1 mg/m3. A neurotoxin and the controlling metal on most agricultural steel welding (GMAW, FCAW, submerged arc on mild and high-strength steel).
• Iron oxide (as Fe): 5 mg/m3. The bulk of mild-steel weld fume and oxy-cutting fume.
• Ozone (O3): 0.1 ppm. From the welding arc, dominating on aluminium GMAW (AS/NZS 1554.7) and high on stainless GTAW; also from plasma cutting.
• Hexavalent chromium Cr(VI): 0.05 mg/m3. From stainless and high-alloy welding (AS/NZS 1554.6); an IARC Group 1 human carcinogen and the controlling metal where stainless is welded.
• Nickel (inhalable): 1 mg/m3; insoluble nickel compounds 0.1 mg/m3. From stainless and nickel-alloy welding and machining.
• Isocyanate (TDI/MDI, and HDI/IPDI as the isocyanate group): 0.02 mg/m3 TWA / 0.02 mg/m3 ceiling — among the lowest in the standard. From two-pack polyurethane primer and topcoat in the paint line. Potent respiratory sensitiser — the killer of the ag-machinery paint shop.
• Xylene: 80 ppm. Solvent carrier in primers, topcoats and thinners.
• Toluene: 50 ppm. Solvent in paint and adhesive.
• Styrene: 50 ppm TWA, 100 ppm STEL. From fibreglass cab, tank and panel lamination with polyester and vinyl-ester resin — the controlling exposure in the FRP bay.
• Oil mist (mineral): 5 mg/m3. From CNC machining flood coolant, straight cutting oil and grinding.
• MEK methyl ethyl ketone / MIBK / acetone / IPA: 200 / 50 / 250 / 400 ppm respectively. From paint gun-wash, fibreglass tooling clean-down and parts cleaning.
• Respirable crystalline silica (RCS): 0.05 mg/m3. From silica-bearing grit blasting and silica-contaminated substrate stripping.
• Carbon monoxide (CO): 30 ppm. From the gas-fired bake oven, diesel engine-test cells and LPG forklift operation indoors.
• Carbon dioxide (CO2): 5000 ppm. Indoor-air-quality marker; rises in poorly ventilated assembly halls.
• Zinc oxide: 5 mg/m3. From welding or cutting galvanised or zinc-primed steel — the cause of metal-fume fever.
• Aluminium (welding/oxide): 1 mg/m3 metal, 10 mg/m3 oxide. From aluminium boom and panel welding and machining.

Every dust and fume LEV branch in an ag-machinery plant has to keep the operator's breathing-zone air below the relevant WES. Where multiple contaminants are present (manganese plus iron oxide plus ozone at a steel weld station, or Cr(VI) plus nickel plus ozone at a stainless station), the additive-mixture rule applies and the LEV must be sized to the most demanding fraction. This is the calculation that drives capture velocity, transport velocity, branch sizing and main sizing across every duct system in the plant.

3. Heavy structural welding fume LEV — capture at source for chassis, booms, frames and headers

Heavy structural welding is the single largest source of airborne contaminant in an agricultural-machinery plant and the process that consumes the most LEV ductwork. Tractor and loader chassis, sprayer booms, header fronts and feeder housings, seeder bars and air-cart frames, disc-chain assemblies, drawbars and three-point-linkage componentry are all built by multi-pass arc welding of heavy steel section — commonly 6 to 25 mm plate and structural sections joined by GMAW (MIG), flux-cored arc welding (FCAW) and, on long straight seams, submerged arc, all to AS/NZS 1554.1. Aluminium boom and panel work adds GMAW and GTAW to AS/NZS 1554.7; stainless trim and food-contact augers add welding to AS/NZS 1554.6.

The fume chemistry is dominated by welding fume not otherwise classified (now targeted below 1 mg/m3 respirable and trending toward no safe number), manganese (1 mg/m3, the controlling neurotoxic metal on alloy steel), iron oxide (5 mg/m3), and ozone (0.1 ppm) from the arc. On galvanised or zinc-primed steel, zinc oxide (5 mg/m3) drives metal-fume fever. On stainless, hexavalent chromium (0.05 mg/m3) and nickel become the controlling carcinogenic metals. On aluminium, ozone and aluminium oxide dominate. SafeWork Australia's progressive tightening of the welding-fume WES — reflecting the reclassification of welding fume as a carcinogen — has made capture-at-source the legal expectation, not merely good practice. General dilution ventilation alone no longer meets the regulator's position on weld fume.

The engineering response is layered capture at the arc. The first and most effective layer is on-torch fume extraction — a high-vacuum extraction nozzle integrated into the welding gun that draws fume at the point of generation, typically 50 to 100 m3/h per torch at high vacuum (15 to 30 kPa) into a small-bore high-vacuum extraction main. On-torch extraction captures the highest fraction of fume at the lowest total airflow, which minimises the make-up-air and energy penalty. Where on-torch extraction is impractical (large multi-pass structural work where the gun geometry will not carry an extraction shroud), the second layer is a fixed or articulated capture hood — an extraction arm or a fixed hood positioned within 300 to 500 mm of the arc, drawing at 0.5 to 1.0 m/s capture velocity at the weld. The third layer, for large fabrications welded across a big bay, is overhead canopy or push-pull ventilation capturing the rising thermal plume, backed by AS 1668.2 dilution as the background top-up.

The duct that ties this together carries metallic fume and fine spatter at 18 to 22 m/s transport velocity — below 15 m/s the metallic particulate drops out at horizontal elbows and accumulates as a deposit that is both an LEV-performance loss and a fire risk on oily duct. The branch and trunk mains run in heavy-gauge galvanised or aluminised steel (1.6 to 2.0 mm) because thinner gauge erodes at the elbows under the abrasive metallic load. Where the bay welds stainless or aluminium and the duct carries Cr(VI) or ozone-laden air, the duct material steps up to stainless and the seam is continuously welded for a hermetic, cleanable run. The mains terminate at a cartridge or reverse-air baghouse dust collector with automatic pulse cleaning, a spark-arrestor or drop-out box on the inlet (essential where hot spatter enters the duct), and HEPA polish on the discharge where the fume is carcinogenic. Each bay's collector is sized for the coincident weld load — not every torch fires at once, so a coincidence factor (typically 0.5 to 0.7 across a multi-station bay) sets the trunk and collector size. SBKJ forms these heavy-gauge weld-fume trunk mains on the SBAL-III, the branch duct on the SBAL-V with the SBLR-600 forming the seam, the round mains on the SBFB-1500 TDF spiral line, and the hermetic Cr(VI) seam on the SBSF-1525 stitchwelder.

4. Plate cutting — plasma, laser and oxy-fuel fume and dust extraction

Profile cutting of heavy steel and aluminium plate is the front end of every ag-machinery fabrication line — chassis rails, boom sections, header fronts and feeder housings, seeder bars, disc-chain frames, mounting brackets and gusset plates are all cut from plate by CNC plasma, CNC fibre laser and oxy-fuel cutting. All three processes generate metal-oxide fume and fine particulate at high rate, and the extraction is one of the heaviest dust duties in the plant.

Plasma cutting is the highest fume generator of the three. A plasma arc at 20,000 to 30,000 degrees C vaporises the kerf metal, producing iron oxide, manganese (1 mg/m3) from the alloy steel, ozone and oxides of nitrogen from the arc, and zinc oxide where the plate is galvanised. Fibre laser cutting produces a finer fume plume at lower total volume but, on coated, galvanised or zinc-primed plate, releases zinc oxide and the associated metal-fume-fever risk, and on stainless produces Cr(VI). Oxy-fuel cutting produces a heavy molten slag and iron-oxide fume plus combustion products from the fuel gas.

The standard control is a downdraught cutting table with sectioned, damper-controlled extraction. The table is divided into zones along its length, and dampers open extraction only to the zone directly beneath the active cut — this concentrates the available airflow at the kerf (typically 1.0 to 1.5 m/s downdraught at the cut) instead of spreading it thinly across the whole table, and it dramatically reduces the total airflow and the collector size. The captured fume and dust runs in a 18 to 22 m/s dust main, in heavy-gauge galvanised or aluminised duct because plasma and laser dust is abrasive and hot at capture, to a cartridge or baghouse dust collector. The collector inlet carries a spark-arrestor or drop-out box because incandescent particulate enters the duct directly from the cut. Because fine metallic cutting dust mixed with combustible fines (from cutting oily, primed or composite-faced plate) can be explosible, the collector is fitted with deflagration protection and isolation to the NFPA 68/69 framework, and the duct is bonded and earthed where the dust hazard requires it under AS/NZS 60079. SBKJ forms the downdraught-table extraction plenums in 1.6 to 2.0 mm gauge on the SBAL-III, the round trunk mains on the SBFB-1500 TDF spiral line, and cuts the heavier custom table-plenum transitions on the SBPC1500 plasma cutter.

5. CNC machining — oil mist and coolant aerosol extraction

Agricultural machines carry a large content of precision-machined componentry — axles, hubs, wheel motors and final-drive shafts; gearbox and transmission housings; gear hobbing and shaping; hydraulic valve blocks, manifolds and cylinder bores; pins, bushes and bearing seats. These are produced on CNC turning centres, machining centres, gear machines, grinders and honing machines, almost all running flood coolant or straight cutting oil. The machining cell's airborne hazard is oil mist and coolant aerosol — a fine, sticky, flammable aerosol generated as the high-speed cutting action atomises and vaporises the coolant.

The SafeWork Australia WES for mineral oil mist is 5 mg/m3, and beyond the inhalation hazard the oil aerosol creates a fire risk (oil film accumulating inside ductwork and on the collector media) and a slip and air-quality problem if it escapes into the machining hall. The control is enclosure-and-extraction: modern machining centres are fully enclosed, and the enclosure is extracted at a face velocity (0.3 to 0.5 m/s at any opening) into a branch duct that runs at 8 to 12 m/s — a lower transport velocity than dust mains because oil-mist aerosol stays entrained at lower velocity and because the duct must be pitched to drain captured oil back to the collector rather than to keep heavy solids airborne. The mains terminate at a coalescing oil-mist filter or an electrostatic precipitator that drops the oil out for return to the coolant system, with a final filter polish before the cleaned air is recirculated or discharged.

The duct itself must be leak-tight (oil weeps through a sealed lock seam over time), drainable at every low point, and accessible for the periodic degrease that oil-mist duct demands — an oil-fouled duct is a fire load and a cleaning liability. SBKJ forms the machining-cell branch duct in 0.7 to 1.2 mm galvanised or stainless on the SBAL-V with the SBLR-600 forming the seam, lays a continuous hermetic weld bead on the SBSF-1525 where the oil-mist duct must not weep, and forms the drainable round trunk mains to the coalescer on the SBFB-1500 TDF spiral line. Swarf and chip handling is a separate mechanical-conveyor and briquetting problem, not an HVAC duty, but the dry-grinding and tool-sharpening stations add a fine metallic-dust LEV branch that ties into the general dust-collection system.

6. Shot blast and grit blast — pre-paint surface preparation to AS 3957

Before any quality paint or powder-coat system goes onto a chassis, boom, frame or implement, the steel is abrasive-blasted to remove millscale, rust and old coating and to create the surface profile that the primer keys into — typically a near-white Sa 2.5 finish to AS 1627.4 / ISO 8501. This surface-preparation step has the most severe dust duty in the entire plant, and AS 3957 is the controlling standard for the blast-room enclosure and its ventilation.

The abrasive is garnet, chilled iron grit, steel shot, aluminium oxide or, on older operations, copper slag. The dust loading is enormous — kilograms per minute of airborne abrasive fines, spent media, blasted millscale and pulverised old coating. Where the abrasive is silica-bearing (garnet is low-silica but not silica-free, and some legacy abrasives carry significant silica) or the substrate carries silica contamination, respirable crystalline silica at 0.05 mg/m3 becomes the controlling exposure and the dust is a serious chronic health hazard. The blasted old coating can also carry lead, hexavalent chromium (from old chromate primers) or zinc, which the dust-collection system must contain and which the spent abrasive disposal must account for.

A blast room is ventilated by a high-volume downdraught or cross-draught system — typically 0.5 to 0.7 m/s through-room air velocity for blaster visibility and dust clearance, which on a large blast room is one of the biggest single air-movers in the plant. The air is drawn through a media-reclaim floor (a grated floor with screw or pneumatic conveyors that recover the reusable heavy abrasive) or a sweep-out arrangement, then through a cyclone or settling chamber that drops the heavy spent abrasive for reclaim, then to a large cartridge or reverse-air baghouse dust collector. Where the dust is combustible — fine aluminium-oxide-blasted aluminium swarf, organic coating dust, or magnesium-bearing fines — the collector carries deflagration protection to the NFPA 68/69 framework. The reclaim and dust mains run in heavy-gauge abrasion-resistant duct — 3 to 5 mm wear plate, with hardened liners or wear-backs at every elbow — at 20 to 25 m/s to keep the heavy abrasive entrained without dropout. This is the most punishing duct duty in the building, and thin commercial-gauge duct fails in months. Smaller components are blasted in blast cabinets (enclosed, operator-outside, glove-and-window) with their own reclaim and dust-collection circuit at lower scale. SBKJ forms the blast-room hood, reclaim and dust-main transitions and plenums on the SBAL-III and the SBPC1500, with the heaviest wear sections specified in plate that the SBPC1500 plasma cutter profiles.

7. Paint line — spray-and-bake, solvent VOC and the isocyanate-controlled booth

The paint line is the most safety-critical HVAC system in an agricultural-machinery plant, and the two-pack polyurethane topcoat is the controlling design case for the entire facility's ventilation. Large equipment — tractor bodies, sprayer chassis and booms, header fronts, seeder frames, air carts — is finished by a spray-and-bake process: surface preparation and degrease, a solvent-borne or two-pack epoxy primer, then a two-pack polyurethane topcoat, sprayed in a downdraft booth and cured in a bake oven.

The killer compound is isocyanate. Two-pack (2K) polyurethane primers and topcoats cure by reacting a polyol resin with an isocyanate hardener — the hardener is typically an HDI (hexamethylene diisocyanate) trimer with residual monomeric HDI, plus IPDI in some systems and the aromatic TDI and MDI in some primers. The SafeWork Australia WES for isocyanates as a group is 0.02 mg/m3 (TWA), with TDI and MDI carrying a 0.02 mg/m3 ceiling — among the lowest exposure limits in the entire standard. Isocyanates are potent respiratory sensitisers: once a spray-painter is sensitised, occupational asthma can be triggered by exposure far below the WES, and the sensitisation is permanent and career-ending. The solvent carriers add their own load — xylene (80 ppm), toluene (50 ppm), n-butyl acetate, MEK and MIBK — and the atomised solvent forms a flammable atmosphere inside the booth.

The HVAC control is total enclosure of spraying inside a downdraft spray booth engineered to AS 1668.2, AS 1940 and NFPA 33. A downdraft booth delivers tempered, filtered supply air through a full-ceiling plenum, sweeping vertically past the operator and the workpiece at 0.3 to 0.5 m/s and capturing the overspray and the isocyanate-and-solvent-laden air into a floor-level exhaust pit and out through the exhaust stack. The booth supply and exhaust are balanced to hold the booth at slightly negative pressure relative to the surrounding paint shop so that no contaminant escapes. The booth runs AS/NZS 60079 hazardous-area-rated fans, motors and lighting because the booth interior is a Zone 1 flammable-vapour space during spraying. Critically, no booth performance removes the need for air-supplied respiratory protection — every painter wears an air-fed full-face or hood respirator to AS/NZS 1715 and AS/NZS 1716 regardless of booth airflow, because the isocyanate WES is so low that booth ventilation alone cannot guarantee a safe breathing-zone concentration during spraying.

The bake oven cures the applied film at 60 to 100 degrees C (for low-bake 2K systems) or higher for force-dry, and is governed by AS 1375: the oven is purged of any flammable atmosphere before burner light-off, monitored for flame failure, and exhausted through a dedicated high-temperature riser. The booth-to-oven interlock prevents the oven firing while the booth is in a spray cycle. The exhaust ductwork — both the booth solvent-and-isocyanate exhaust and the oven cure off-gas — is a flammable-vapour duct to AS 1940 and NFPA 33: it must be hermetic, conductive, bonded and earthed, run at a velocity that prevents overspray deposition (which is both a fire load and a duct-blockage risk), and provide cleaning access along its length because paint overspray accumulates inside booth-exhaust duct and must be removed on a maintenance schedule. SBKJ forms the booth supply and exhaust plenums and the booth-to-oven transitions in 1.6 to 2.0 mm aluminised on the SBAL-III, the round booth-exhaust and stack risers on the SBFB-1500, the continuous hermetic exhaust seam on the SBSF-1525 and SB-ZF1500 stitchwelders, the high-temperature oven-riser plate transitions on the SBPC1500 plasma cutter, and the heavy thermal flanges on the SBTF-1500/1602/2020 TDF flange line.

8. Powder coating — implement finishing, overspray reclaim and cure oven

Powder coating is the dominant finish for small-to-medium agricultural implements and components — seeder tynes and points, disc-chain frames and discs, guards and shrouds, brackets, toolboxes, hydraulic-tank covers and the smaller fabricated parts — because it produces a tough, durable, low-VOC finish well suited to abrasive outdoor agricultural service. The HVAC profile is fundamentally different from wet paint because there is no solvent and no isocyanate; the controlling hazard is combustible organic dust.

Electrostatic powder — epoxy, polyester or epoxy-polyester hybrid resin — is sprayed in a powder booth where the charged powder is attracted to the earthed workpiece and the overspray is captured and reclaimed for reuse. The overspray is a fine combustible organic dust with a measurable deflagration index Kst and a minimum ignition energy, which makes it an explosible dust under AS/NZS 60079 and the NFPA 68/69 framework. The booth runs at a controlled face velocity (typically 0.5 m/s minimum at every opening and aperture) into a cartridge reclaim module that recovers the oversprayed powder. The engineering controls that prevent a powder-cloud deflagration are continuous monitoring of the powder concentration in the booth and duct below 50 percent of the lower explosible limit, thorough bonding and earthing of all conductive parts (the workpiece, the booth, the duct, the reclaim module) to prevent static-discharge ignition, and deflagration venting or chemical suppression on the reclaim collector.

The cure oven — gas-fired convection or infrared at 180 to 200 degrees C — melts and cross-links the powder into a continuous film and is governed by AS 1375. The oven is purged before light-off and exhausted through a dedicated high-temperature riser that carries the cure off-gas (the small fraction of volatile cure by-product released as the powder cross-links) and any combustion products. The reclaim duct, the booth-extract and the oven-exhaust are each formed in the appropriate material — galvanised or aluminised for the reclaim and booth duct, high-temperature aluminised or stainless for the oven riser. SBKJ forms the powder-booth reclaim and extract duct on the SBAL-V and SBFB-1500, with bonding and earthing detailed on every conductive section per AS/NZS 60079, and the oven-riser transitions on the SBPC1500.

9. Fibreglass cab and panel manufacturing — styrene LEV

Many agricultural machines carry fibreglass-reinforced plastic (FRP/GRP) components — tractor and harvester cab roofs and shells, sprayer and seeder tanks and hoppers, guards, fenders, fairings and instrument fascias. FRP is laid up by open-mould hand lay-up, spray-up with a chopper gun, or resin transfer moulding (RTM), using unsaturated polyester or vinyl-ester resin cured with an MEK-peroxide catalyst. The dominant airborne hazard is styrene monomer, which evaporates from the resin during lamination and cure.

The SafeWork Australia WES for styrene is 50 ppm TWA with a 100 ppm STEL, and open spray-up lamination is one of the heaviest styrene emitters in manufacturing — without strong LEV the laminator's breathing-zone concentration easily exceeds the WES. Acetone (250 ppm) for tooling and equipment clean-down and the MEK-peroxide catalyst add to the airborne load, and styrene-and-air forms a flammable mixture, which makes the laminating bay a hazardous area.

The HVAC control is a cross-draught or downdraught laminating bay drawing a controlled face velocity (0.5 to 1.0 m/s) across the open mould, capturing the styrene-laden air at the source. The duct material must resist styrene — styrene attacks galvanising and softens some plastics — so the LEV duct is stainless or purpose-rated FRP, running at 8 to 12 m/s to a styrene-abatement device: a regenerative thermal oxidiser, a carbon adsorber or an acrylic-fibre filter, then a stack discharge engineered to AS/NZS 60079 because of the flammable styrene-and-air mixture. Gelcoat spray and chopper-gun stations are additionally treated as paint-booth-class enclosures with their own dedicated extract. Operators who mould their own cabs, tanks and panels in-house run a dedicated styrene LEV system separate from the metal-fabrication and paint extract; the styrene exhaust must never be combined with the weld-fume or paint-booth duct. SBKJ forms the stainless styrene-LEV branch and trunk duct on the SBAL-V and SBFB-1500 with continuous hermetic seam on the SBSF-1525.

10. Assembly, hydraulic and engine fit — dilution ventilation and engine-test exhaust

The final-assembly hall is where the fabricated, machined, painted and powder-coated components come together into a complete machine — chassis and body, driveline and transmission, hydraulics, electrical and electronic systems, cab, wheels and tyres, and the diesel engine. The airborne hazards here are lower in intensity than the fabrication and paint zones but are not nil, and the ventilation strategy shifts from capture-at-source LEV to building dilution ventilation with targeted local extract at specific stations.

The dominant point hazards are diesel engine running and testing, hydraulic-oil aerosol from system commissioning and leak-testing, adhesive and sealant VOC (urethane and silicone sealants, threadlockers, gasket compounds), battery handling, and indoor LPG forklift and tug operation. Diesel engine test — running a newly assembled engine on a dynamometer or in-machine for commissioning — generates a concentrated exhaust stream (carbon monoxide at 30 ppm WES, oxides of nitrogen, diesel particulate matter classified as a Group 1 carcinogen) that must be captured at the tailpipe by a direct-connection exhaust-extraction hose or a high-canopy hood and ducted directly to atmosphere through a dedicated stack — it is never diluted into the general hall air. Hydraulic commissioning generates a fine oil aerosol at the test rigs, captured by local extract similar to the machining oil-mist duty. Adhesive and sealant application releases VOC (toluene, xylene, isocyanate in some urethane sealants) controlled by local extract at the application bench. The general hall is ventilated to AS 1668.2 dilution and ASHRAE 62.1 for acceptable indoor air quality, with CO and CO2 monitoring (CO 30 ppm, CO2 5000 ppm) where engine running or LPG forklift traffic is significant. SBKJ supplies the engine-test extraction duct, the hydraulic-test oil-mist branch and the general-extract and make-up-air duct in galvanised and aluminised on the SBAL-V, SBAL-III and SBFB-1500.

11. Tyre fit, adhesive, sealant and ancillary process hazards

Beyond the major process zones, an ag-machinery plant carries a tail of ancillary processes that each add a small LEV or ventilation demand. Tyre fitting and bead seating — large agricultural tyres on rims — uses bead-seating lubricant and, on tube-type assemblies, may involve solvent cements; the station needs local extract for solvent VOC and good general ventilation. Adhesive and sealant stations bond cab glass, trim, panels and gaskets using urethane (some carrying isocyanate), silicone, MS-polymer and epoxy adhesives, each releasing VOC controlled by bench extract. Hydraulic-hose crimping and assembly is largely a mechanical operation with minimal airborne hazard. Wash bays and pressure-wash stations generate a water aerosol and, where alkaline or solvent degreasers are used, a chemical mist controlled by local extract and a properly drained, corrosion-resistant duct.

The decal and graphics application, the final-detail and touch-up paint station (often a small dedicated touch-up booth running the same isocyanate-controlled 2K topcoat as the main line, and therefore subject to the same AS 1940 / NFPA 33 / 0.02 mg/m3 isocyanate controls at smaller scale), and the battery-fill and electrical-commissioning stations each add a targeted extract branch. None of these is large individually, but together they form a network of small LEV branches that tie into the general dust-and-fume collection system, and the duct designer has to account for them in the total building exhaust and make-up-air balance. SBKJ forms these small-branch duct runs on the SBAL-V with the SBLR-600 forming the seam, with stainless and hermetic seam where the branch carries solvent, isocyanate or chemical mist.

12. Electric and autonomous agricultural machinery — the emerging assembly envelope

The agricultural-machinery sector is in the early stages of the same electrification and automation transition that is reshaping on-road vehicles. Battery-electric tractors and implements, hybrid-diesel-electric drivelines, and autonomous and semi-autonomous machines (driverless tractors, autonomous sprayers and seeders, precision-ag platforms carrying sensor and compute payloads) are moving from prototype to early production. Each adds new manufacturing and assembly demands that change the HVAC envelope.

Battery assembly is the most significant new HVAC driver. Lithium-ion battery-pack assembly carries a thermal-runaway and off-gas hazard (the electrolyte solvents and the vent gas from a cell in thermal runaway are flammable and toxic), and the assembly area requires gas detection, dedicated extract and a ventilation strategy that handles a credible cell-venting event — an envelope closer to a battery-manufacturing cleanroom than a traditional engine-fit hall. Battery module and pack assembly, electrolyte handling where present, and battery testing and conditioning each carry their own extract and gas-detection requirement. Electric-drive assembly — motors, inverters, power electronics — is a clean, low-fume operation requiring conditioned, filtered air and ESD control more than contaminant extract.

Autonomous-ag assembly adds sensor, lidar, camera, GPS and compute-payload integration — again a clean, conditioned, low-fume environment. The net effect of the electric and autonomous transition is to add clean-assembly and battery-handling envelopes alongside the traditional heavy-fabrication and paint zones, and to increase the share of the plant that needs tempered, filtered, conditioned supply air with humidity and ESD control rather than high-volume contaminant extract. The duct material for these zones is conventional galvanised spiral for the clean supply, with stainless and dedicated extract where battery off-gas or electrolyte handling creates a specific hazard. SBKJ forms the clean-assembly supply duct on the SBAL-V and SBFB-1500 and the dedicated battery-area extract in stainless with hermetic seam on the SBSF-1525.

13. Hazardous-area classification — mapping the plant to AS/NZS 60079

Hazardous-area classification is the discipline that determines where flammable vapour or explosible dust can be present, and it governs the electrical-equipment selection, the duct bonding and the isolation-valve placement throughout the plant. An ag-machinery plant carries both gas/vapour and dust hazardous areas, and the duct designer has to map every zone before fabrication begins.

The gas/vapour hazardous areas (classified under AS/NZS 60079.10.1) centre on the paint line and the fibreglass bay. The spray-booth interior during spraying is Zone 1 (a flammable vapour likely in normal operation); the paint mixing room, the gun-wash station, the bulk-solvent store and the fibreglass spray-up and gelcoat bay are Zone 1; the general paint-shop area around the booth and the general fibreglass laminating area are Zone 2 (a flammable vapour unlikely in normal operation and present only briefly). The dust hazardous areas (classified under AS/NZS 60079.10.2) centre on the combustible-dust collection systems — the interior of the powder-coat reclaim collector and the interior of a combustible-dust transport main are Zone 20 (continuous explosible dust); the powder-coat booth interior is Zone 21 (occasional); the general area around the powder-coat booth and the fine-metallic dust collector is Zone 22 (unlikely, short duration).

The classification drives three things. First, electrical equipment — every fan, motor, light fitting, instrument and duct-mounted sensor inside or near a classified zone must be Ex-rated to the appropriate protection technique and gas/dust group. Second, duct bonding and earthing — flammable-vapour and combustible-dust duct must be conductive throughout, continuously bonded with conductive flange gaskets at every joint, externally bonded to the building earth grid, and verified at commissioning with documented earth-resistance below 1 ohm to ground at every section, so that no static charge can accumulate and discharge as an ignition spark. Third, isolation and protection — explosion-isolation valves on combustible-dust duct (per NFPA 68/69) and fire dampers on flammable-vapour duct (per AS 1682) at the appropriate boundaries. SBKJ supplies conductive-gasket-detailed, bonded ductwork for every classified zone, with the bonding strategy documented for the commissioning pack.

14. Combustible dust — powder coat, fine metallic and organic blast dust deflagration control

Combustible dust is the explosion hazard that ties together the powder-coat booth, the plasma and laser cutting tables, the grit-blast room and any fine-metallic dust-collection system, and it is governed by AS/NZS 60079 (for the area classification) and the NFPA 68/69 framework (for the engineering protection). A combustible-dust deflagration requires the simultaneous presence of fuel (the suspended dust), an oxidant (air), confinement (the duct or the collector), dispersion (the dust cloud) and an ignition source — the classic dust-explosion pentagon — and the protection strategy removes or controls as many of these as practical.

The dusts of concern in an ag-machinery plant are the powder-coat overspray (epoxy, polyester and hybrid organic powder with a measurable Kst and a low minimum ignition energy), the fine metallic dust from plasma and laser cutting (iron, aluminium and alloy fines, which can be explosible especially when mixed with combustible coating fines), and the organic and metallic dust from grit blasting (the pulverised old coating, and aluminium-oxide-blasted aluminium swarf). Aluminium dust is a particular concern — fine aluminium is a highly reactive combustible metal with a high deflagration index, and any operation that generates fine aluminium dust (machining, cutting or blasting aluminium booms and panels) must treat the dust collection as a combustible-metal duty.

The engineering controls are layered. Prevention first — concentration monitoring to keep the dust cloud below 50 percent of the lower explosible limit (mandatory on the powder-coat booth), thorough bonding and earthing to remove static-discharge ignition, and spark-arrestor pre-separation to remove incandescent particulate before it reaches the collector. Protection second — deflagration vent panels on the collector (NFPA 68) sized for the dust Kst and the enclosure volume, directing a deflagration to a safe location; explosion-isolation valves (NFPA 69) between the collector and the inbound duct, which pre-trip on flame or pressure rise and prevent flame propagation back up the duct into the booth or cutting table; and chemical suppression or inerting where the dust is especially reactive. The duct itself is bonded and earthed throughout, routed with the minimum bends to prevent dust accumulation, and built in spiral round geometry where practical because the streamlined cross-section resists the dropout that creates accumulated deflagration fuel. SBKJ forms the combustible-dust duct on the SBFB-1500 TDF spiral line with the TIG-weld seam option and conductive flange gaskets, and details the bonding and the isolation-valve interface for the dust-collection-system designer.

15. WES dilution calculation — sizing extract against the workplace exposure standard

The workplace exposure standard is the number that ultimately drives every LEV and dilution-ventilation sizing decision in the plant, and the duct designer has to be able to run the calculation. AS 1668.2 gives the dilution-ventilation method for the cases where capture-at-source alone is insufficient, and the SafeWork Australia WES values give the target concentrations.

The dilution airflow Q (in litres per second) required to hold a contaminant at a target concentration is, in its basic form, Q equals the contaminant generation rate divided by the target concentration, multiplied by a mixing-efficiency safety factor (the K factor, typically 3 to 10 for imperfect mixing in a real workshop). For a welding bay the controlling contaminant is welding fume (target well below 1 mg/m3 respirable) or manganese (1 mg/m3); for the paint shop it is isocyanate (0.02 mg/m3); for the grit-blast room it is RCS (0.05 mg/m3) or the abrasive dust; for the machining cell it is oil mist (5 mg/m3); for the fibreglass bay it is styrene (50 ppm). Where several contaminants are present at one station — manganese plus iron oxide plus ozone at a steel weld, or Cr(VI) plus nickel plus ozone at a stainless weld — the additive-mixture rule applies: the sum of the ratios of each contaminant's concentration to its WES must not exceed one, and the ventilation is sized to the most demanding fraction.

In practice, the calculation almost never lands on dilution as the primary control in an ag-machinery plant. The isocyanate WES at 0.02 mg/m3 is so low, and the styrene and RCS targets so demanding, that capture-at-source LEV — the weld hoods, the downdraft booth, the blast-room extract, the oil-mist enclosure — is always the primary control, with dilution as the background top-up. The booth, the blast room and the weld hoods drive the total building exhaust well above any AS 1668.2 dilution minimum. What the WES calculation does control is the verification: the breathing-zone air-sampling program (quarterly, NATA-certified, fed into the ISO 45001 system) measures the actual concentration against the WES at every operator-occupied zone, and the result either confirms the LEV is working or triggers a redesign. The make-up air to AS 1668.1 and NCC Section J — tempered, filtered and energy-recovered — must replace every cubic metre extracted while holding the fabrication hall at the right pressure relationship to the paint and assembly areas.

16. Material selection — why galvanised survives some duties and fails others

Galvanised duct is the workhorse of HVAC fabrication, and in an ag-machinery plant it is the right answer for a larger share of the work than in some other heavy industries — the general supply air, the general extract, the lighter weld-fume branches and the assembly-hall ventilation are all well served by hot-dip-galvanised carbon steel to AS/NZS 4254. But several duties demand a step up in gauge or a change of material:

16.1 Heavy galvanised and aluminised — abrasion-resistant dust and weld-fume mains

The structural weld-fume mains, the plasma and laser plate-cutting dust mains, and the powder-coat reclaim duct all carry abrasive particulate at 18 to 22 m/s, which erodes thin-gauge galvanised at every elbow. The answer is heavy-gauge (1.6 to 2.0 mm) galvanised or aluminised steel, with abrasion-resistant elbows and wear liners at every change of direction. Aluminised steel adds temperature resistance (good service to 400 to 600 degrees C) for the cooler sections of the bake-oven and engine-test exhaust.

16.2 Wear plate — the grit-blast reclaim and dust duty

The grit-blast reclaim and dust mains carry the heaviest abrasive load in the plant at 20 to 25 m/s, and even heavy-gauge galvanised wears through quickly. The answer is 3 to 5 mm wear plate, with hardened liners, wear-backs or replaceable wear sections at every elbow and at the high-wear straight runs. This is the most punishing duct duty in the building, and it is the duty that most distinguishes an ag-machinery (and mining-adjacent) fabricator's duct from ordinary commercial work.

16.3 Stainless — Cr(VI), styrene, isocyanate and corrosive-mist duty

Where the duct carries hexavalent chromium (stainless welding to AS/NZS 1554.6), ozone-laden aluminium GMAW fume, styrene (fibreglass lamination), isocyanate-and-solvent (the paint-booth and oven exhaust), or chemical mist (wash bays, any pickling), the duct steps up to 304 or 316 stainless with a continuous hermetic welded seam. Galvanising fails these duties — styrene and solvent attack the zinc, Cr(VI) and ozone duct must be cleanable, and the flammable-vapour exhaust must be conductive and leak-tight. The SBSF-1525 stitchwelder lays the continuous longitudinal weld that makes a hermetic stainless duct.

16.4 High-temperature stainless — the bake-oven riser

The bake-oven exhaust riser, where the gas exits the oven above 180 to 200 degrees C, runs in high-temperature aluminised or 309/310-grade stainless for the first section before transitioning to ordinary construction downstream of the cooling section. The SBPC1500 plasma cutter profiles the heavier high-temperature plate transitions, and the SBTF-1500/1602/2020 TDF flange line forms the heavy flanges that carry the thermal load.

17. Velocity and sizing — transport and capture for ag-machinery dust and fume

Ag-machinery HVAC sizing is dominated by two velocity calculations — capture velocity at the contaminant source, and transport velocity in the main carrying the contaminant to the collector. Both are driven by the contaminant chemistry, particle size and density, and the practical limits of fan static-pressure capacity.

Capture velocity at the source is the velocity at which the contaminant is drawn away from the operator's breathing zone faster than thermal buoyancy, mechanical disturbance and cross-drafts can carry it past. For structural welding fume, 0.5 to 1.0 m/s at the arc (with on-torch high-vacuum extraction achieving capture at much lower total airflow); for plasma and laser cutting, 1.0 to 1.5 m/s downdraught at the cut; for the grit-blast room, 0.5 to 0.7 m/s through-room velocity; for the spray booth, 0.3 to 0.5 m/s downdraft past the operator; for the powder-coat booth, 0.5 m/s minimum at every opening; for the fibreglass laminating bay, 0.5 to 1.0 m/s across the open mould; for CNC machining-cell enclosures, 0.3 to 0.5 m/s at the openings.

Transport velocity in the main is the minimum velocity at which the contaminant stays entrained without dropout. For grit-blast abrasive (the heaviest load), 20 to 25 m/s; for metallic weld fume, plasma and laser dust, and powder-coat overspray, 18 to 22 m/s — below 15 m/s the metallic and mineral particulate drops out at horizontal elbows and accumulates; for oil-mist aerosol, 8 to 12 m/s (the aerosol stays entrained at lower velocity and the duct is pitched to drain); for styrene and solvent VOC vapour, 8 to 12 m/s (no particulate dropout concern); for chemical mist, 10 to 15 m/s (corrosive but not abrasive). Each branch is sized at its design transport velocity, and the trunk main is sized for the coincident load of all branches at their design coincidence factor — lower for the welding bays (not every torch fires at once) and near unity for the booth and blast room (continuous duty).

18. SBKJ machine line — the fabrication envelope for ag-machinery ductwork

Fabricating ag-machinery-grade ductwork in an Australian shop requires the right machine fit, the right process discipline and the right documentation. The SBKJ Product Catalog 2026 covers the full envelope for ag-machinery duct fabrication, from the heavy abrasion-resistant dust mains through the hermetic flammable-vapour paint-booth exhaust to the lighter assembly-hall supply duct:

SBAL-V — auto duct line handling galvanised, aluminised and 304/316 stainless from 0.7 mm to 1.6 mm with TDF flange. Used for the bulk of supply and general extract ductwork, the weld-fume branch duct, the CNC oil-mist branches, the powder-booth reclaim duct, the assembly-hall ventilation and the stainless styrene and corrosive-mist branches.

SBAL-III — heavy-gauge auto duct line for 1.6 mm to 2.0 mm work with TDF flange. Used for the structural weld-fume trunk mains, the plasma and laser plate-cutting dust mains, the grit-blast hood and reclaim transitions, the paint-booth supply and exhaust plenums, and the booth-to-oven transitions — every heavy abrasion-resistant and high-velocity duct in the plant.

SBSF-1525 — stitchwelder laying a continuous longitudinal weld bead on the seam. Used for the paint-booth and bake-oven flammable-vapour exhaust, the fibreglass styrene exhaust, the oil-mist mains, the Cr(VI) stainless weld-fume duct and any duct requiring a hermetic, conductive, cleanable seam.

SB-ZF1500 — TDF stitchwelder for trunk-main continuous longitudinal weld. Used for the larger-diameter paint-booth-exhaust and dust trunk mains that must be hermetic and leak-tight.

SBFB-1500 — TDF spiral tubeformer producing spiral round duct 80 to 1500 mm diameter in 0.6 to 1.5 mm galvanised, aluminised or stainless. Used for the round weld-fume, plasma and laser dust, grit-blast dust, powder-booth reclaim, oil-mist and paint-booth-exhaust trunk mains — the streamlined geometry holds transport velocity through bends without dropout. The single most-used machine for ag-machinery dust-main fabrication.

SBPC1500 — plasma cutter handling galvanised, aluminised and stainless plate up to 25 mm thickness. Used for the custom downdraught-cutting-table plenums, the grit-blast-room transitions, the paint-booth-to-oven transitions, the high-temperature bake-oven risers and the reinforced wear-plate sections.

SBLR-600 — rollformer producing Pittsburgh-lock and snap-lock longitudinal seams. Used for rectangular duct construction across the weld-fume branch, oil-mist, powder-booth and general-ventilation duct.

SBTF-1500/1602/2020 — TDF flange line forming heavy flanges and trunk-main flanging at 1500 to 2020 mm. Used for the heavy thermal flanges on the bake-oven risers, the large paint-booth supply and exhaust plenums and the largest dust trunk mains at the highest-volume plants.

19. Commissioning, monitoring and measurement & verification (M&V)

Commissioning ag-machinery ductwork is more demanding than commissioning conventional industrial HVAC because of the safety-critical paint-booth, dust-collection and weld-fume systems. The compliance documentation required at handover includes pressure-test records (1.5x design pressure for 30 minutes per AS 4254 on every branch), earth-bonding verification at every flange on combustible-dust and flammable-vapour duct (resistance below 1 ohm to ground), NATA-certified airflow balance against the design schedule, capture-velocity verification at every weld hood, booth-face-velocity verification at the spray and powder booths, blast-room through-velocity verification, the AS 3957 blast-room ventilation certificate, the AS 1940 / NFPA 33 paint-booth compliance documentation, the AS/NZS 60079 hazardous-area-classification document, and the NFPA 68/69 deflagration-protection documentation for every combustible-dust collector.

Measurement and verification (M&V) and ongoing monitoring run daily, weekly, monthly, quarterly and annual cycles. Daily: booth and oven interlock function, dust-collector differential pressure (alarm at plus or minus 25 percent of design), powder-booth concentration below 50 percent of the lower explosible limit, CO monitoring in the engine-test and assembly areas. Weekly: visual inspection of duct interior at access ports for overspray, dust and oil accumulation; condition of bonding straps and conductive flange gaskets; spark-arrestor and drop-out box condition. Monthly: airflow balance verification at key branches, fire-damper and explosion-isolation-valve actuation test, fan-vibration measurement. Quarterly: NATA-certified breathing-zone air sampling against the WES for welding fume, manganese, hexavalent chromium, isocyanate, styrene, oil mist, ozone and RCS at every operator-occupied zone, fed into the AS 4801 / ISO 45001 OHS management system. Annual: full-system pressure test, full bonding-resistance re-verification, high-temperature-section inspection on the bake-oven riser, dust-collector media replacement, and AS/NZS 60079.17 inspection of all Ex equipment. The M&V program is what converts a fabricated duct system into a demonstrably compliant one, and it is the data the operator carries into the ISO 14001 environmental and ISO 45001 safety audits and the EPA stack-emissions licence renewal.

20. Standards and exposure-limit reference table

The following consolidates the standards and the controlling exposure limits referenced throughout this guide, as a quick-reference for the duct designer and the mechanical contractor:

• AS 1668.1 / AS 1668.2 — fire and smoke control of air handling, and mechanical ventilation including dilution against the WES and make-up air.
• AS 4254.1 / AS 4254.2 — sheet-metal and flexible duct construction; pressure-test at 1.5x design pressure for 30 minutes.
• AS/NZS 1554.1 / .6 / .7 — welding of steel / stainless / aluminium structures; the basis of the weld-fume LEV design.
• AS 1940 — storage and handling of flammable and combustible liquids; the paint-line controlling standard.
• AS 3957 — abrasive-blasting enclosure walls, floors and ventilation.
• AS/NZS 60079 — explosive atmospheres; Zone 1/2 (gas) and Zone 20/21/22 (dust) classification and Ex equipment.
• NFPA 33 — spray application using flammable materials; booth ventilation and interlocks.
• NFPA 68 / NFPA 69 — deflagration venting and explosion prevention for combustible-dust collectors.
• AS 1375 — industrial fuel-fired appliances; the bake-oven and cure-oven safety code.
• AS 1530.4 / AS 1682 — fire resistance of building elements and fire/smoke dampers; rated penetrations.
• AS 4024 — safety of machinery; guarding, access and isolation.
• AS/NZS 1715 / AS/NZS 1716 — selection and use, and equipment standards, for respiratory protective equipment.
• NCC Section J / ASHRAE 62.1 — building energy efficiency and ventilation for acceptable indoor air quality.
• ISO 9001 / ISO 14001 / ISO 45001 — quality, environmental and OHS management systems.
• Welding fume (NOC): below 1 mg/m3 respirable, trending to no safe number. Manganese: 1 mg/m3. Iron oxide: 5 mg/m3. Ozone: 0.1 ppm.
• Hexavalent chromium: 0.05 mg/m3. Nickel: 1 mg/m3 inhalable, 0.1 mg/m3 insoluble. Zinc oxide: 5 mg/m3.
• Isocyanate (TDI/MDI/HDI group): 0.02 mg/m3 — the paint-line killer. Xylene: 80 ppm. Toluene: 50 ppm.
• Styrene: 50 ppm TWA, 100 ppm STEL. Oil mist: 5 mg/m3. RCS: 0.05 mg/m3. CO: 30 ppm. CO2: 5000 ppm.

21. Energy, heat recovery, Green Star and NABERS — the sustainability dimension

A high-extract ag-machinery plant moves an enormous volume of air, and every cubic metre extracted has to be replaced by tempered, filtered make-up air. In a regional Victorian, South Australian or NSW plant, that make-up-air tempering load — heating cold winter air to comfort temperature — is a major energy cost and a major carbon line item. NCC Section J pushes the designer toward heat recovery on the make-up stream: run-around coil loops, plate heat exchangers or thermal wheels that recover heat from the warm process exhaust into the cold incoming make-up air. On a plant extracting hundreds of thousands of cubic metres per hour, the heat-recovery saving is substantial and the payback short.

Beyond the mandatory NCC Section J floor, ag-machinery manufacturers increasingly pursue Green Star (the Green Building Council of Australia rating) for new facilities and NABERS Energy (the National Australian Built Environment Rating System) for operational performance, particularly where the manufacturer is supplying to corporate or government customers with sustainability-procurement requirements, or where the parent group carries a net-zero commitment. The HVAC design contributes through heat recovery, high-efficiency fans (EC motors, variable-speed drives matching extract to actual process demand rather than running flat-out continuously), demand-controlled ventilation in the assembly and clean zones, and right-sized dust collection. The duct designer supports this through low-leakage construction (every leak is conditioned air lost), correctly sized duct (oversizing wastes fan energy, undersizing drives up static pressure), and the M&V data that demonstrates the ongoing performance a NABERS rating depends on. The combination of high process extract and the drive for energy efficiency is one of the defining tensions in modern ag-machinery HVAC, and it is resolved by capture-at-source LEV (which minimises the total airflow), heat recovery (which recovers the unavoidable extract energy) and variable-speed control (which matches the airflow to the actual production load).

22. Accessibility, amenity and DDA — AS 1428.1 in the manufacturing facility

An ag-machinery manufacturing facility is a workplace and, in its office, showroom, training and amenity areas, a place that customers, dealers and visitors enter. The Disability Discrimination Act and the associated AS 1428.1 (design for access and mobility) apply to the accessible paths, amenities and public areas of the facility, and they interact with the HVAC design in the conditioned office, training-room, showroom and amenity zones — these areas require comfort conditioning to ASHRAE 62.1 and the NCC, with the supply and return ductwork integrated into accessible ceiling and bulkhead spaces without compromising the accessible-path clearances AS 1428.1 requires. The amenity ventilation (change rooms, wash-down facilities, lunch rooms) carries its own AS 1668.2 extract requirement. While AS 1428.1 is not a ducting standard, the duct designer has to coordinate the conditioned-zone duct routing with the accessible-design requirements so that the building services and the accessibility provisions do not conflict — a coordination task that is routine on the office-and-amenity side of a large manufacturing facility.

23. Demand trend — food security, precision agriculture and the export-implement market

The Australian agricultural-machinery manufacturing sector sits on a structurally growing demand base, and that growth feeds directly into demand for new and expanded manufacturing facilities and the HVAC infrastructure that serves them. Three forces drive it.

First, food security and the agricultural commodity cycle. Australia is one of the world's major exporters of wheat, barley, canola, pulses, beef, lamb, wool, cotton, sugar and horticulture, and the long-run global demand for food and fibre underpins continued investment in Australian agricultural production capacity — which is mechanised by tractors, headers, seeders, sprayers and tillage equipment. When commodity prices and seasonal conditions are strong, capital spending on new machinery surges, and the manufacturers and importers scale fabrication, assembly and finishing capacity to match.

Second, precision agriculture and the technology transition. GPS-guided machinery, variable-rate application, autonomous and semi-autonomous platforms, controlled-traffic farming, sensor-and-data-driven agronomy and the move toward electrified drivelines are reshaping the machinery itself and the way it is built. This drives investment in new assembly capability — electronics integration, battery assembly, sensor calibration — alongside the traditional heavy fabrication, and it adds the clean-assembly and battery-handling HVAC envelopes discussed earlier.

Third, the export-implement opportunity. Australian implement builders have a genuine and growing export presence — Kelly Engineering exports its disc-chain systems internationally from Booleroo SA, and a range of Australian seeder, tillage and sprayer builders export to markets with comparable broadacre conditions. Australian-designed equipment is well regarded for its suitability to large-scale, low-rainfall, abrasive-soil conditions, and the export market gives the domestic fabrication base a scale beyond the Australian farm market alone. Each of these forces — food-security-driven domestic demand, the precision-ag technology transition, and the export-implement market — sustains investment in manufacturing capacity, and every new or expanded weld bay, cutting cell, blast room, paint line and assembly hall needs the AS/NZS 1554, AS 1940, AS 3957 and AS/NZS 60079 compliant ductwork this guide describes.

24. Industry bodies and standards organisations

The Australian agricultural-machinery sector is supported by an active set of industry bodies and standards organisations. The Tractor and Machinery Association of Australia (TMA) is the peak national body representing the manufacturers, importers and distributors of agricultural and outdoor-power machinery, publishing the industry sales statistics and representing the sector on policy, safety and standards. AgForce (the Queensland peak farm-organisation body) and the National Farmers' Federation (NFF) represent the farmer-customer base whose demand drives the machinery market, and whose positions on agricultural policy, drought, water and trade shape the long-run demand environment. The Australian Industry Group (Ai Group) represents Australian manufacturers broadly, including the heavy-fabrication and equipment-manufacturing base, on industrial relations, skills, energy and manufacturing policy.

On the standards and regulatory side, Standards Australia publishes the AS and AS/NZS standards referenced throughout this guide. SafeWork Australia sets the model work-health-and-safety framework and the workplace exposure standards. The state work-health-and-safety regulators (WorkSafe Victoria, SafeWork NSW, Workplace Health and Safety Queensland, SafeWork SA, WorkSafe WA) enforce the WHS duties on the manufacturers. The state environment-protection authorities (EPA Victoria, EPA NSW, the Queensland and South Australian EPAs) licence the stack emissions from the dust collectors and the paint-booth exhaust. The Green Building Council of Australia administers Green Star, and the NABERS national administrator runs the operational rating scheme. The combination of TMA representation, the farm-organisation demand context, Ai Group's manufacturing-policy voice, and the Standards Australia / SafeWork Australia / state-EPA regulatory framework forms the institutional environment within which an ag-machinery manufacturer plans, builds and operates its facility.

25. Competitive positioning — why the SBKJ machine fit suits the Australian ag-machinery fabricator

An Australian mechanical contractor or in-house fabrication team that wants to serve the ag-machinery manufacturing sector — building the weld-fume LEV, the cutting-table extraction, the blast-room dust mains, the paint-booth exhaust and the assembly ventilation — needs a fabrication envelope that spans heavy abrasion-resistant duct, hermetic flammable-vapour duct, and lighter general-ventilation duct, all to Australian Standards. That is precisely the envelope the SBKJ Product Catalog 2026 is built to cover.

The SBAL-III gives the heavy-gauge capacity for the abrasion-resistant weld-fume, plate-cutting and blast-room dust mains that ordinary commercial duct lines cannot form economically. The SBAL-V, SBLR-600 and SBFB-1500 give the production speed for the high-volume branch and round duct. The SBSF-1525 and SB-ZF1500 stitchwelders give the hermetic continuous seam that the paint-booth exhaust, the styrene LEV and the Cr(VI) stainless duct demand — a capability that distinguishes a serious heavy-fabrication duct shop from a commercial one. The SBPC1500 plasma cutter gives the custom-geometry plate-cutting capacity for the booth transitions, oven risers, blast-room hoods and downdraught-table plenums. The SBTF-1500/1602/2020 flange line gives the heavy flanging for the largest plenums and the thermal-duty bake-oven risers. The combination lets an Australian fabricator produce every duct system in an ag-machinery plant in-house, to Australian Standards, with the documentation the operator's ISO 9001, ISO 14001 and ISO 45001 audits and the EPA licence require — rather than subcontracting the hard duties (the hermetic stainless seam, the heavy abrasion-resistant duct, the custom plate transitions) to a specialist and losing margin and control. The SBKJ Group engineering team in Box Hill North VIC supplies the machines, the engineering support and the commissioning advisory to make that production capability real.

26. Closing — SBKJ engineering support for Australian ag-machinery manufacturing

The Australian agricultural-machinery manufacturing sector is investing in new and expanded capacity across heavy fabrication, finishing and the emerging electric and autonomous-ag assembly envelopes, driven by food-security demand, the precision-ag technology transition and a genuine export-implement opportunity. Every transition from an ageing facility to a modern one, and every capacity expansion, exposes the limits of generic commercial HVAC and demands purpose-engineered ductwork that meets the full standards stack outlined in this guide — the AS/NZS 1554 weld-fume LEV, the AS 1940 and NFPA 33 paint-booth exhaust, the AS 3957 blast-room dust mains, the AS/NZS 60079 hazardous-area and NFPA 68/69 combustible-dust protection, and the AS 1668.2 dilution and make-up-air balance. The SBKJ Group engineering team in Box Hill North VIC is positioned to support Australian fabricators and mechanical contractors serving the sector with a combination of machine supply (SBAL-V, SBAL-III, SBSF-1525, SB-ZF1500, SBFB-1500, SBPC1500, SBLR-600 and SBTF-1500/1602/2020), engineering documentation, commissioning support and ongoing technical advisory across every process zone described in this document.

We will be exhibiting at ARBS 2026 in Sydney in May with the full SBKJ machine portfolio plus ag-machinery-specific reference samples covering heavy abrasion-resistant weld-fume and dust mains, hermetic stainless paint-booth and styrene exhaust, and high-temperature bake-oven transitions. Pre-show meetings with Australian ag-machinery manufacturers, their mechanical contractors and existing customers are scheduled across the week.