Fastener, Bolt, Screw, Nut, Nail, Rivet, Spring & Wireform Manufacturing HVAC Duct Guide

1. Why fastener and spring manufacturing HVAC is its own engineering discipline

A modern Australian fastener plant is one of the most chemically and thermally diverse industrial environments you can walk into. Within a single site — Ajax Fasteners in Braeside VIC, a Konnect or Bremick production line, a merchant heat-treater in Dandenong, a wire mill at Waratah InfraBuild in Newcastle, or a spring works running Sandvik and Bohler wire — you find cold-forging presses flooding their dies with oil and soap lubricant in one bay, a continuous hardening furnace running a hydrogen-and-carbon-monoxide endothermic atmosphere in the next, an oil quench throwing dense combustible smoke beside it, a hydrochloric pickle line stripping mill scale off wire coils down the aisle, and a chrome plating shop evolving chromic-acid mist at the back. Each of those processes has its own contaminant chemistry, its own ignition and explosion risk, its own workplace exposure standard, and its own demand on the duct material. HVAC ductwork inside a fastener, spring or wireform plant is not a commodity item. It is a process-engineering problem that touches AS 1375 heat-treatment furnace safety, AS/NZS 60079 hazardous-area electrical compliance, AS 3780 corrosive-substance handling, AS 3957 combustible-dust deflagration safety, AS 1940 flammable-liquid control, and the SafeWork Australia workplace exposure standards for oil mist, carbon monoxide, hydrogen chloride, sulphuric acid mist, hexavalent chromium, alkaline mist and nickel — all sitting inside the same building envelope.

This guide writes against the full breadth of the Australian fastener and spring sector as it exists in 2026. The cold-forming tier — the high-speed cold heading of wire blanks into bolts, screws, rivets and nails, followed by thread rolling — is where the volume lives. Ajax Fasteners in Braeside VIC is the heritage Australian name, an established automotive and structural bolt maker with deep roots in the Melbourne manufacturing belt. Konnect Fastening Systems, Bremick, ITW Proline and its Buildex screw brand, SI Fasteners (trading as Sied), Australian Fasteners, Zenith Fasteners and Allfast cover the broader manufacturing and distribution landscape, with Würth Australia anchoring the distribution side. These operations run multi-station bolt makers, headers, nut formers and thread rollers, and every one of them throws forging-lubricant oil mist, soap-lube aerosol and fine metal dust off the dies.

The heat-treatment tier is where the safety stakes climb. To turn a soft cold-formed blank into a high-tensile fastener of property class 8.8, 10.9 or 12.9 the part must be hardened and tempered — austenitised in a controlled atmosphere, quenched in oil, then tempered back. High-volume continuous mesh-belt and sealed-quench furnaces, and batch furnaces for the heavier work, run under an endothermic protective atmosphere — endo-gas — that is roughly 40 percent hydrogen, 20 percent carbon monoxide and 40 percent nitrogen. That single fact drives more of the HVAC design than anything else in the plant: carbon monoxide is colourless, odourless and toxic at 30 ppm; hydrogen is flammable above 4 percent in air. The furnace burn-off, the quench-oil smoke, the generator room and the dilution ventilation are all governed by AS 1375 and AS/NZS 60079.

The surface-finishing tier is where the chemistry turns aggressive. Before plating or coating, scale is stripped in pickling and acid-descaling baths — sulphuric or hydrochloric acid throwing corrosive fume. Then fasteners are zinc plated, zinc-nickel plated or chrome plated, with chromate conversion coatings layered over the zinc. Chrome plating and chromating involve hexavalent chromium, a confirmed carcinogen with a workplace exposure standard of just 0.0003 mg/m3 — one of the lowest in the entire Australian standard. Zinc-flake coatings (Geomet, Dacromet) and phosphate-and-oil coatings add VOC and curing-oven exhaust. Some fasteners are hot-dip galvanised, throwing zinc fume and flux smoke — a hazard covered in detail in the dedicated SBKJ galvanising guide and cross-referenced here.

The spring and wireform tier rounds out the sector. Wallaby Springs, Airdrome and Aus-Spring coil compression, extension and torsion springs from spring wire; the heavier spring makers run Sandvik and Bohler oil-tempered and hard-drawn wire. Wire drawing — at Waratah InfraBuild in Newcastle producing nails, wire and fencing, at the OneSteel and InfraBuild wire operations, and at Cyclone — pulls rod through carbide dies through a soap or oil lubricant, throwing soap dust or oil mist off the capstans. Spring coiling, end grinding and shot peening each generate their own dust-and-mist load. Across this entire sector, ductwork must survive simultaneous demands for oil-mist capture, combustible-dust deflagration resistance, corrosive-acid resistance, high-temperature service and carbon-monoxide dilution. Each is manageable in isolation. Together they explain why a generic commercial fabricator treating a fastener plant as just another industrial job loses money on the first project. This guide walks every major process zone, explains what changes about the ductwork, and closes 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, AS 4254, AS 1375, AS 1940, AS 3957, AS 3780, AS/NZS 60079, AS 1110/1111/1112, ISO 9001/14001/45001

Fastener and spring manufacturing HVAC in Australia sits at the intersection of more than a dozen overlapping standards and codes. Ignoring any one of them is a notice-of-non-compliance from SafeWork Australia, the state EPA or the relevant WorkSafe authority waiting to happen. The standards stack splits into building-code and ventilation compliance, occupational-health exposure compliance, heat-treatment furnace safety, flammable-liquid and corrosive-substance handling, combustible-dust safety, hazardous-area electrical compliance, the fastener product standards that define what is being made, and the overarching management-system standards.

2.1 AS 1668.2 and AS 1668.1 — mechanical ventilation and fire

AS 1668.2 is the umbrella mechanical-ventilation standard for Australian buildings, governing the required ventilation rate for the control of airborne contaminants. Fastener and spring plants fall under NCC Class 8 industrial occupancy. AS 1668.2 drives the dilution-ventilation calculation for the heat-treatment hall (sweeping escaped carbon monoxide below the 30 ppm workplace exposure standard), the make-up air requirement for every cubic metre extracted by localised exhaust, and the supply-air tempering and filtration. AS 1668.1 covers the fire and smoke control aspects of air-handling systems — fire dampers at fire-compartment penetrations, smoke management, and the shutdown logic that integrates the HVAC with the building fire system. In practice the plant rarely sits near the AS 1668.2 building-volume minimum because the sum of localised exhaust at every header, furnace, pickle tank and plating line drives total extract well above the building figure; what AS 1668.2 governs most tightly is that every extracted cubic metre is replaced with controlled, tempered, filtered make-up air so the production zones stay at neutral or slightly negative pressure relative to offices and so contaminant does not migrate.

2.2 AS 4254.1 and AS 4254.2 — sheet-metal and flexible duct construction

AS/NZS 4254.1 (sheet metal) and AS/NZS 4254.2 (flexible) govern duct construction across the normal pressure ranges — low pressure to 500 Pa, medium to 1000 Pa and high to 2500 Pa. Most fastener-plant supply air, general extract and the cooler downstream sections of oil-mist and dust mains sit inside the AS 4254 ranges. The hot furnace burn-off flue and the wet acid-laden pickling and plating runs sit outside AS 4254 in their high-temperature or corrosion-resistant sections and require purpose-engineered construction (316 stainless, FRP, PP or PVC); AS 4254 picks up again on the cool, downstream, non-corrosive side. Every SBKJ-fabricated steel section is built to AS 4254 with a documented pressure test at 1.5 times design pressure for the handover pack.

2.3 AS 1375 — the code of practice for heat-treatment furnaces

AS 1375 is the single most important standard for the heat-treatment hall and the document that most directly shapes the furnace HVAC. It is the SAA industrial-furnaces code, covering the safe operation of fuel-fired and electrically heated furnaces, the handling of controlled and protective atmospheres, the management of endothermic and exothermic generated gas, flame-curtain and purge requirements, and the burn-off of combustible atmosphere gas at furnace openings. For the duct designer, AS 1375 sets the framework for the burn-off flue capture, the dilution ventilation that keeps escaped carbon monoxide below 30 ppm, the purge-before-light sequences that prevent a hydrogen-rich furnace charge from deflagrating, and the segregation of the endo-gas generator as a hazardous-atmosphere area. AS 1375 is read alongside AS 1668.2 (dilution), AS/NZS 60079 (the generator-room hazardous area) and the combustion-safety principles of NFPA 86 where AS guidance is supplemented.

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

AS 1940 governs flammable and combustible liquids. A fastener plant triggers AS 1940 at several points: the forging-oil and soap-lubricant inventory in the cold-forming hall; the quench-oil reservoir at every hardening furnace (a large inventory of combustible oil held hot); the solvent-degrease tanks; and the oil-mist captured stream itself, which is combustible and therefore makes the oil-mist ductwork a flammable-stream envelope. AS 1940 drives bunded containment around oil and solvent inventories, fire dampers and cleanable bare-steel construction (no internal lining) on the oil-mist and quench-mist ducts, and segregated storage for solvents and chemicals.

2.5 AS 3957 — dust hazard and combustible dust

AS 3957 is the Australian standard for the layout of buildings to control the spread of fire, and in the dust-hazard context it works alongside the hazardous-area dust principles to address combustible particulate. Fastener and spring plants generate several combustible dusts: the soap-lube dust off cold-forming dies and dry wire-drawing capstans; the fine metal dust shed from wire and trimmed slugs; the metallic grinding dust from spring end-grinding; and the metallic shot-and-media fines from shot peening. Combustible metal dust is a deflagration hazard. AS 3957, read with the hazardous-area dust classification of AS/NZS 60079.10.2 and the deflagration-protection practice of NFPA 68 (venting) and NFPA 69 (inerting and isolation), forces the duct designer to ask at every dust-collection point: what is the dust, is it combustible, what is its deflagration index, and what is the engineered protection chain (vent panels, isolation valves, inerting) between the collector and the inbound duct? The answer drives collector selection, isolation-valve placement and the bonding-and-grounding of every metre of dust-laden duct.

2.6 AS 3780 — the storage and handling of corrosive substances

AS 3780 governs corrosive substances and is the controlling standard for the pickling and electroplating exhaust. The sulphuric and hydrochloric acid of the pickle line, the chromic acid and chromating chemistry of the plating shop, and the caustic of the alkaline plating and degrease tanks are all corrosive substances. AS 3780 drives bunded containment, segregated chemical storage, and the corrosion-resistant material selection (FRP, PP, PVC for wet runs; 316L stainless for steel transitions) for the exhaust serving these areas. It is read alongside AS 1668.2 for the capture velocity and dilution, and the relevant state EPA licence for the scrubber discharge.

2.7 AS/NZS 60079 — explosive atmospheres

AS/NZS 60079 is the hazardous-area-classification standard, triggered in a fastener plant at two distinct kinds of location. On the gas side, AS/NZS 60079.10.1 classifies the endothermic-gas generator room (hydrogen and carbon-monoxide inventory) and the solvent-degrease tank area (flammable vapour) as hazardous areas requiring Ex-rated electrical equipment. On the dust side, AS/NZS 60079.10.2 classifies the interior of combustible-dust collectors and dust transport lines. The standard drives Ex-rated fans, motors, instrumentation and gas-detection heads in the affected zones, and drives the requirement that dust-laden and generator-room ductwork be conductive throughout, continuously bonded with conductive flange gaskets, externally bonded to the building earth grid, and verified at commissioning to less than 1 ohm to ground at every section.

2.8 AS/NZS 2243.8 and AS 4024 — fume cupboards and machinery safety

AS/NZS 2243.8 covers fume cupboards and is referenced for the plating-shop laboratory, the chemistry and analysis benches, and any bench-scale acid work, setting capture velocity and exhaust-path requirements. AS 4024 is the machinery-safety standard, relevant to the duct designer for the guarding of fans and rotating equipment, and for the safe-access requirements that drive inspection and clean-out port placement on oil-mist and dust mains. The two together ensure that the ductwork is safe to operate and safe to clean.

2.9 AS/NZS 1715 and AS/NZS 1716 — respiratory protective equipment

AS/NZS 1715 (selection, use and maintenance) and AS/NZS 1716 (the equipment standard) govern respiratory protective equipment. LEV is always the primary control, but in a fastener plant RPE is the documented backup — powered air-purifying respirators for furnace operators in a carbon-monoxide environment, acid-gas cartridge respirators for pickle and plating operators, and dust masks for grinding and peening. The HVAC design and the RPE programme are documented together so that the residual exposure after LEV is shown to sit within the protection factor of the selected RPE.

2.10 AS 1110, AS 1111, AS 1112 — the fastener product standards

AS 1110, AS 1111 and AS 1112 define the products being made and provide essential context for the duct designer. AS 1110 covers ISO metric hexagon bolts and screws (product grade A and B, the higher-tensile structural and engineering fasteners). AS 1111 covers ISO metric hexagon commercial bolts and screws (product grade C). AS 1112 covers ISO metric hexagon nuts. These standards define the property classes — 4.6, 8.8, 10.9, 12.9 — that dictate whether a fastener is cold-formed and used as-is or must be hardened and tempered, which in turn dictates whether the plant runs the heat-treatment hall and its endo-gas and quench HVAC at all. A plant making only low-class commercial fasteners may skip hardening; a plant making structural 8.8 and 10.9 bolts cannot.

2.11 NCC Section J, ASHRAE 62.1, ISO 9001/14001/45001 and NFPA 68/69

NCC Section J sets the energy-efficiency requirements for the building fabric and services — relevant to the heat-recovery and fan-energy decisions on the HVAC. ASHRAE 62.1 is the international ventilation-for-acceptable-indoor-air-quality reference, used alongside AS 1668.2 for the office and amenity zones. ISO 9001 (quality), ISO 14001 (environment) and ISO 45001 (occupational health and safety) are the management-system standards that most established Australian fastener and spring makers hold; the HVAC commissioning documentation feeds directly into the ISO 14001 emissions register and the ISO 45001 exposure-monitoring records. NFPA 68 (deflagration venting) and NFPA 69 (explosion prevention by inerting and isolation) are the US references used for the engineered protection of combustible-dust collectors where AS guidance is supplemented. Together this stack defines the compliance envelope that every metre of fabricated ductwork must satisfy.

3. Cold forging and heading — oil-mist and soap-lube LEV in the bolt-making hall

Cold forging is where most fasteners begin and where the largest single oil-mist load in the plant is generated. A multi-station cold header takes wire blanks cut from a coil and, in a sequence of die stations operating at hundreds of strokes per minute, upsets and shapes the head of a bolt, screw, rivet or nail without heating the metal. Nut formers do the equivalent for nuts. The tonnage is enormous and the dies must be continuously flooded with forging lubricant — a blend of forming oil, soap-based dry-film lubricant and extreme-pressure additive — to prevent galling, manage friction and protect the tooling. As the dies slam shut and the slugs are trimmed, the lubricant is thrown off as a fine oil-mist aerosol, a soap-lube dust, and a fine metal dust shed from the wire surface. The SafeWork Australia workplace exposure standard for oil mist is 5 mg/m3 as an eight-hour time-weighted average. An uncontrolled bolt-making hall running a bank of headers sits well above that figure, with a visible oily haze and an oily film on every surface.

The control is localised exhaust ventilation at each machine. The most effective arrangement is an enclosing hood or close-capture canopy built around each header and thread roller, capturing the mist at the source before it escapes into the general air. The captured stream is ducted at 7 to 10 m/s transport velocity — fast enough to keep the oil aerosol entrained and prevent it dropping out and pooling in the duct — to a high-efficiency oil-mist eliminator. The eliminator is typically a multi-stage coalescing collector (progressively finer coalescing media that merge the fine droplets into drainable liquid) or an electrostatic precipitator (charging the droplets and collecting them on grounded plates). The cleaned air is then either recirculated through a HEPA polish stage back into the hall (saving conditioned air and reducing make-up load) or discharged to atmosphere under AS 1668.2.

Because the captured stream is oil-laden and therefore combustible, the oil-mist ductwork falls squarely under AS 1940 flammable-liquids principles and the combustible-stream logic of AS 3957. The duct must be bare, cleanable steel — never internally lined, because oil-soaked lining is both a fire load and impossible to clean. Fire dampers are fitted at fire-compartment boundaries and the collector is protected against fire propagation. Access doors are fitted along the mains so the accumulated oil film can be cleaned out on a maintenance schedule, because an oil-fouled duct is a fire risk and a capture-velocity risk as the cross-section narrows. The hood bodies and canopies are 304 stainless (316 where the lubricant carries chloride additives), formed on the SBAL-V auto duct line, with continuously TIG-welded seams on the SBSF-1525 stitch welder so the hood is oil-tight with no seam weep. The round oil-mist mains are 304 stainless spiral formed on the SBFB-1500 tubeformer. At Ajax Fasteners in Braeside VIC and the broader Melbourne and Dandenong fastener cluster, this oil-mist capture circuit is the single largest LEV system in the plant.

4. Wire drawing — soap-dust and oil-mist capture for spring wire and nail wire

Wire drawing is the process that converts hot-rolled rod into the precise-diameter wire that feeds the cold headers, the spring coilers and the nail machines. The rod is pulled through a sequence of carbide or diamond dies, each reducing the diameter slightly, with the wire passing through a drawing lubricant at every die to manage the friction and heat of the reduction. There are two lubricant regimes, and they generate different contaminants. Dry drawing pulls the wire through a soap-based powder lubricant held in a die box; the soap coats the wire and the excess is thrown off the capstans as a fine soap dust. Wet drawing runs the wire through an oil or soap-solution bath; the excess is thrown off as a fine oil mist.

The soap dust is both a housekeeping nuisance and a combustible-dust hazard under AS 3957 — soap-based drawing compounds are organic and combustible, and accumulated soap dust on overhead surfaces is a deflagration fuel. The oil mist sits under the 5 mg/m3 oil-mist workplace exposure standard. The control in both cases is close-capture hooding over the die boxes and capstans, capturing the contaminant at the point of release. The captured stream is ducted at 8 to 12 m/s transport velocity — the higher figure for soap dust to keep the heavier particulate entrained — to a cartridge dust collector for dry-drawing soap dust or an oil-mist eliminator for wet-drawing oil. The soap-dust collector, handling combustible organic dust, gets engineered deflagration protection: explosion-vent panels per NFPA 68, isolation valves to stop a deflagration propagating back into the duct main, and continuous earth bonding under AS/NZS 60079.

Australian wire mills run this capture across their drawing bays. Waratah at InfraBuild in Newcastle — producing nails, wire and fencing wire at volume — runs extensive capstan and die-box extraction, as do the broader OneSteel and InfraBuild wire operations and Cyclone. The spring-wire feedstock used by Wallaby Springs, Airdrome, Aus-Spring and the heavier spring makers running Sandvik and Bohler oil-tempered and hard-drawn wire is drawn to close tolerance through the same kind of die-box lubrication, with the same soap-dust or oil-mist capture demand. SBKJ fabricates the capstan and die-box hoods, the dust and mist mains, and the collector transitions in galvanised and 304 stainless on the SBAL-V auto duct line, the SBFB-1500 spiral tubeformer and the SBLR-600 lock former, with deflagration-protected sealed-and-bonded construction on the combustible soap-dust circuit.

5. Heat treatment — the continuous and batch hardening furnace, quench and temper

Heat treatment is where a soft cold-formed blank becomes a high-tensile fastener and where the most demanding HVAC in the plant lives. To reach property class 8.8, 10.9 or 12.9 a fastener must be hardened — heated into the austenitising range, held, then rapidly quenched in oil to transform the steel to hard martensite — and then tempered, reheated to a lower temperature to relieve brittleness and set the final mechanical properties. The high-volume workhorse for this in a fastener plant is the continuous mesh-belt or sealed-quench furnace: fasteners flow continuously through a controlled-atmosphere austenitising zone, drop into an integral oil quench, and pass through a continuous temper furnace, all under AS 1375. Heavier and lower-volume work runs in batch furnaces — sealed-quench batch furnaces or pit furnaces — on the same atmosphere and quench principles.

The HVAC envelope around this hardware has three distinct contaminant sources. First, the controlled atmosphere itself — the endothermic gas described in the next section — which is continuously burned off at every furnace opening by a flame curtain, generating a hot burn-off plume captured by a dedicated flue hood. Second, the oil quench, which flashes off a dense, hot, oily, combustible smoke as red-hot parts hit the oil; this rolls off the quench elevator and the furnace exit vestibule and is captured by a dedicated high-temperature canopy. Third, the temper furnace, which off-gasses residual quench oil burning off the parts as they reheat. Each source is captured separately because they differ in temperature, oil loading and combustibility, and because mixing a hot burn-off stream with an oil-laden quench stream in one duct creates an uncontrolled fire risk.

The quench-mist canopy and the burn-off flue hood are fabricated in 316 stainless to tolerate the heat and the oil, formed on the SBAL-III heavy-gauge auto duct line with the custom hood plenums and high-temperature transitions cut on the SBPC1500 plasma cutter. The quench-mist stream runs to a high-efficiency oil-mist eliminator with a pre-cooling or spark-arrest stage; the duct is bare, cleanable, fitted with fire dampers and access doors under AS 1940. The burn-off flue discharges hot to atmosphere. The general exhaust mains downstream of the furnace cooling section are 1.2 to 1.6 mm stainless formed on the SBAL-III with continuous longitudinal stitch welding on the SB-ZF1500 for an oil-tight, smoke-tight stream. Australian fastener heat-treatment runs at Ajax Fasteners in Braeside, in the in-house lines at Bremick and Konnect, and at the merchant heat-treaters serving the Dandenong, Western Sydney, Brisbane and Perth fastener clusters — every one of them with this three-source furnace HVAC topology.

6. Controlled-atmosphere furnaces and the carbon-monoxide hazard

The single fact that drives more of the fastener-plant HVAC design than any other is that the hardening furnaces run under an endothermic protective atmosphere. To prevent the steel from oxidising (scaling) and decarburising (losing surface carbon and therefore surface hardness) during austenitising, the furnace interior is filled with endo-gas — a reducing atmosphere generated by partially combusting natural gas over a heated nickel catalyst in an endothermic generator. The resulting gas is approximately 40 percent hydrogen, 20 percent carbon monoxide and 40 percent nitrogen. Both of the active components are deadly in different ways.

Carbon monoxide is the toxic hazard. It is colourless, odourless, and binds to haemoglobin with an affinity more than two hundred times that of oxygen, so it asphyxiates at very low airborne concentration. The SafeWork Australia workplace exposure standard is 30 ppm as an eight-hour time-weighted average, with a short-term limit of 60 ppm. A flame-curtain failure, a cracked muffle, a furnace door-seal leak, a generator fault or a momentary positive-pressure excursion can release endo-gas into the workshop atmosphere in minutes, and because carbon monoxide gives no sensory warning, the first sign of a leak without instrumentation is a collapsed operator. Hydrogen is the explosion hazard. Its lower explosive limit is 4 percent in air, so an endo-gas leak is simultaneously a toxic-gas event and a flammable-gas event — a leak large enough to threaten asphyxiation is also large enough to find an ignition source.

The HVAC and gas-detection response is layered and is governed by AS 1375 and AS 1668.2. Every furnace opening runs a flame curtain — a continuous ring of small flames that burns off escaping endo-gas, converting the hydrogen and carbon monoxide to water and carbon dioxide before it can enter the workshop. The burn-off plume is captured by a dedicated stainless flue hood. Roof-level dilution ventilation under AS 1668.2 maintains an air-change rate that sweeps any escaped carbon monoxide out of the building before it can accumulate to 30 ppm at the operator breathing zone. Fixed electrochemical carbon-monoxide sensors are mounted at low level near the furnace doors and quench openings, and at operator breathing-zone height, alarming at the 30 ppm time-weighted average and triggering an evacuate condition and a dilution-fan boost at higher levels. Personal carbon-monoxide dosimeters are issued to furnace operators. Carbon dioxide is also monitored where dilution is marginal — the workplace exposure standard for carbon dioxide is 5000 ppm. SBKJ fabricates the burn-off flue hoods, the roof-level dilution extract mains and the connecting risers in 304 and 316 stainless on the SBAL-V, SBAL-III and SBFB-1500, sized to the AS 1668.2 dilution calculation for the specific endo-gas inventory of the plant.

7. The endothermic-gas generator and neutral salt bath — hazardous-area exhaust

The endothermic-gas generator is the source of the furnace atmosphere and a hazardous area in its own right. It holds a continuous inventory of hydrogen-and-carbon-monoxide-rich gas at temperature and pressure, and a generator fault — a cracked retort, a failed seal, a catalyst problem — can release that gas into the generator room. Under AS/NZS 60079.10.1 the generator room is classified as a hazardous area on two counts simultaneously: the hydrogen creates a flammable-gas atmosphere (lower explosive limit 4 percent) and the carbon monoxide creates a toxic atmosphere (workplace exposure standard 30 ppm). The room therefore gets dedicated gas detection — a carbon-monoxide head alarming at the 30 ppm standard and a hydrogen lower-explosive-limit head alarming at a fraction (typically 10 to 25 percent) of the 4 percent LEL — Ex-rated electrical equipment throughout, and a dedicated high-level extract sized to sweep any leak and interlocked to boost on alarm.

The neutral salt bath is the alternative or supplementary heat-treatment medium used for some fastener and spring work — molten neutral salt provides rapid, uniform heating with excellent surface protection. Modern Australian practice uses cyanide-free neutral salts, eliminating the historic cyanide hazard, but the molten salt still throws a salt fume and vapour that must be captured by a hood over the bath. The protective-atmosphere and salt-bath exhausts are kept entirely separate from the oil-mist and acid-fume circuits. SBKJ fabricates the generator-room extract main, the salt-bath fume hood and the connecting risers in 304 stainless on the SBAL-V and SBFB-1500, with continuous earth bonding to the building grid verified below 1 ohm at every section to satisfy the AS/NZS 60079 hazardous-area requirement, and with the extract fans interlocked to the gas-detection system.

8. Pickling and acid descaling — corrosive acid-fume extraction

Before a fastener, wire coil or spring blank can be plated or coated, the mill scale and oxide that form during hot rolling and heat treatment must be stripped. This is done by pickling — immersion in a sulphuric or hydrochloric acid bath that dissolves the scale — and the process throws an aggressively corrosive acid fume. Hydrochloric pickle lines evolve hydrogen chloride gas; the SafeWork Australia workplace exposure standard for hydrogen chloride is 5 ppm as a peak limitation. Sulphuric pickle lines, particularly when run hot to speed the descaling, throw a sulphuric acid mist; the workplace exposure standard for sulphuric acid mist is 0.2 mg/m3. Both acids attack mild steel and galvanised duct, destroying conventional steel ductwork in a matter of weeks. The pickling reaction also evolves hydrogen at the steel surface, adding a flammable-gas consideration where ventilation is poor.

The control begins at the tank. Lateral lip-extraction slots run along the long edges of every pickle tank, pulling the fume across the liquid surface and away from the operator breathing zone before it can rise into the room, sized to the capture-velocity rules of AS 1668.2 and the corrosive-substance requirements of AS 3780. The captured fume is ducted to a packed-bed wet scrubber, where a recirculating caustic solution neutralises the acid before the cleaned gas is discharged to atmosphere under the relevant state EPA licence. The wet, acid-laden ductwork between the tank hoods and the scrubber must be a non-metallic corrosion-resistant material — fibre-reinforced plastic (FRP), polypropylene (PP) or PVC — because no economic steel survives the service. Where steel is unavoidable, at the scrubber, fan and stack interface, 316L stainless is the minimum, and even 316L is sacrificial in concentrated hydrochloric service and is treated as a wear item.

SBKJ supplies the 316L stainless transition spools, the scrubber-interface flanges and the stack-head sections fabricated on the SBSF-1525 stitch welder and the SBFB-1500 spiral tubeformer, with custom geometry cut on the SBPC1500 plasma cutter and continuous TIG bead via the SB-ZF1500 so every stainless seam is hermetic against residual acid mist. The wet FRP, PP and PVC runs are specified by the corrosives engineer alongside the SBKJ steel sections under AS 3780 and integrated at commissioning. This division of labour — non-metallic for the wet acid runs, stainless for the steel interfaces and stack — is the standard topology for Australian fastener pickling lines.

9. Electroplating — acid mist, alkaline mist and the hexavalent-chromium problem

Electroplating is how most fasteners get their corrosion-protective finish, and it is the area of the plant with the most dangerous single contaminant. Zinc plating (the volume finish for general fasteners), zinc-nickel plating (the premium finish for automotive and structural fasteners demanding higher corrosion resistance) and decorative or hard chrome plating each run banks of plating tanks through which current is passed to deposit metal onto the fastener. Over the zinc and zinc-nickel, a chromate conversion coating — a passivation layer — is applied to lift corrosion resistance further. Both the chrome plating and the chromating involve hexavalent chromium, Cr(VI).

Hexavalent chromium is a confirmed human carcinogen and an aggressive respiratory and skin sensitiser. The SafeWork Australia workplace exposure standard for Cr(VI) is 0.0003 mg/m3 — that is three ten-thousandths of a milligram, or 0.3 micrograms, per cubic metre — as an eight-hour time-weighted average. This is one of the very lowest exposure limits in the entire Australian standard, roughly seventeen thousand times lower than the oil-mist limit, and it leaves no tolerance for a poorly captured tank. The mechanism that puts Cr(VI) into the air is hydrogen evolution: as current passes, hydrogen bubbles form at the cathode, rise through the chromic-acid electrolyte and burst at the surface, flinging a fine chromic-acid mist into the breathing zone. Zinc and zinc-nickel plating add their own contaminants — alkaline mist from the caustic process tanks (sodium hydroxide, workplace exposure standard 2 mg/m3) and, on zinc-nickel, nickel exposure (0.1 mg/m3 insoluble) — and the acid process tanks add general acid mist.

The control for chrome tanks is push-pull lateral lip extraction — a supply jet along one long edge pushing the fume across the surface into an extraction slot on the opposite edge — combined with a surface foam blanket or chemical fume suppressant that physically caps the mist at the liquid surface. The captured stream is ducted in FRP or PVC at controlled velocity to a high-efficiency mesh-pad mist eliminator (capturing the fine droplets) and a packed-bed scrubber before discharge under AS 3780 and the EPA licence. Because the Cr(VI) limit is so low, the chrome exhaust is engineered, balanced and validated to a far tighter standard than any other LEV in the plant, with regular breathing-zone air sampling against the 0.0003 mg/m3 limit through a NATA-accredited laboratory. SBKJ fabricates the 316L stainless transition and stack sections of the plating exhaust on the SBSF-1525 and SBFB-1500; the FRP tank hoods and wet mains are specified alongside under AS 3780 and integrated at commissioning. Australian electroplating of fasteners runs in-house at the larger fastener makers and at specialist electroplating jobbers serving the Dandenong, Western Sydney, Brisbane and Perth fastener clusters.

10. Zinc-flake, mechanical and phosphate coating — VOC, curing ovens and oil mist

Beyond electroplating, several other coating processes are used on fasteners, each with its own ventilation demand. Zinc-flake coating — the application of a water- or solvent-based dispersion of zinc and aluminium flake in a binder, sold under process names such as Geomet and Dacromet — gives high corrosion resistance without the hydrogen-embrittlement risk of electroplating, which makes it the preferred finish for high-tensile and safety-critical fasteners. The coating is applied by dip-spin or spray, then cured in an oven. The contaminant load is the volatile organic compound (VOC) released from the binder and any solvent carrier, plus the curing-oven exhaust. The curing oven runs under furnace-oven combustion-safety principles cross-referenced to NFPA 86, with lower-explosive-limit monitoring on any gas-fired burner, and the VOC is captured at the dip-spin or spray station and at the oven exhaust under AS 1940 flammable-vapour principles for the solvent-based variants.

Mechanical (or peen) zinc plating — tumbling fasteners with zinc powder, glass-bead media and a chemical accelerator to cold-weld a zinc coating onto the surface — is another hydrogen-embrittlement-free option, generating a fine zinc and media dust captured by enclosing-cabinet exhaust. Phosphate coating — the conversion of the steel surface to a crystalline zinc or manganese phosphate layer, usually followed by an oil or wax seal — is used as a paint base, a corrosion-protective base and a friction-control finish. The phosphating bath throws a phosphate mist, and the subsequent oil or wax dip adds an oil mist (5 mg/m3 standard). The phosphate-and-oil exhaust is fabricated in 304 or 316 stainless with continuously welded seams for the oil-bearing stream. SBKJ forms the coating-line hood bodies on the SBAL-V, the curing-oven exhaust risers and high-temperature sections on the SBAL-III, and the round mains on the SBFB-1500, with the SBSF-1525 providing the continuous welded seam for the oil-bearing phosphate and zinc-flake streams.

Hot-dip galvanising is also applied to some fasteners — particularly large structural bolts and agricultural and fencing hardware — throwing zinc fume and ammonium-chloride flux smoke from the molten zinc kettle. The galvanising HVAC envelope (kettle hooding, zinc-oxide fume capture at the 5 mg/m3 standard, and flux-smoke control) is covered in detail in the dedicated SBKJ hot-dip galvanising guide and is cross-referenced here; the same SBKJ machine line that fabricates the fastener-plant exhaust fabricates the galvanising-line hooding.

11. Spring coiling, end grinding and shot peening — combustible metal dust and oil mist

Spring manufacturing has its own characteristic contaminant profile, and the Australian spring sector — Wallaby Springs, Airdrome, Aus-Spring and the broader spring makers running Sandvik and Bohler spring wire — runs three distinct dust-and-mist sources. Coiling is the first: compression, extension and torsion springs are formed on CNC coilers that bend the spring wire around an arbor or through coiling points. The wire carries a coiling lubricant, and the coiling action throws a light oil mist (5 mg/m3 standard) captured by close hooding over the coiler and ducted to an oil-mist eliminator.

End grinding is the second and the more hazardous. Compression springs are ground flat on both ends so they sit square under load, and grinding hardened spring steel against an abrasive wheel throws a fine metallic grinding dust mixed with abrasive-wheel dust. Fine metallic dust is a combustible-dust deflagration hazard under AS 3957 — metal fines have a high surface area and a low minimum ignition energy — so the grinder exhaust runs to either a wet collector (the safest option for combustible metal dust, drowning the deflagration risk in water) or a deflagration-protected dry collector with explosion-vent panels per NFPA 68 and isolation valves per NFPA 69. Shot peening is the third: bombarding the spring surface with metallic shot to induce a compressive residual stress that dramatically lifts fatigue life. The peening cabinet exhaust captures the fine metallic shot dust and the broken-down media fines — again a combustible-metal-dust hazard — and runs to a cyclone-plus-baghouse or cartridge collector with the same deflagration protection.

Each operation is ducted separately because the contaminants differ: an oil-mist eliminator on the coilers, a deflagration-protected dust collector on the grinders, and a deflagration-protected dust collector on the peening cabinets. The combustible-metal-dust mains are conductive, continuously bonded to earth under AS/NZS 60079, and built with sealed welded seams. SBKJ fabricates the grinder and peening-cabinet exhaust hoods, the dust mains and the collector transitions on the SBFB-1500 spiral tubeformer and the SBAL-V auto duct line, with the SB-ZF1500 adding the continuous welded conductive seam on the combustible-dust circuit and the SBLR-600 forming the rectangular hood and transition seams.

12. Tumbling, deburring and degreasing — VOC and alkaline mist

Between the major process steps, fasteners and springs pass through tumbling, deburring and cleaning operations that have their own ventilation demand. Vibratory and rotary tumbling — tumbling parts with ceramic or plastic media and a compound to deburr, descale, polish or clean — throws a fine media-and-compound dust and, in wet tumbling, a fine mist captured by enclosing-cabinet or canopy exhaust. Degreasing — removing forging oil, drawing lubricant and handling soils before plating or coating — runs in one of two regimes, and they have very different hazard profiles.

Solvent degreasing — immersing or vapour-cleaning parts in a chlorinated or hydrocarbon solvent — throws a flammable or toxic VOC vapour. The solvent-degrease tank area is a flammable-vapour envelope under AS 1940 and is classified under AS/NZS 60079 as a hazardous area, with bare cleanable steel ductwork, fire dampers and Ex-rated equipment around the tank, and the captured vapour treated by carbon adsorption or condensation before discharge. Aqueous degreasing — cleaning in a hot caustic or alkaline solution — is the increasingly preferred lower-hazard alternative, throwing an alkaline mist (sodium hydroxide, workplace exposure standard 2 mg/m3) captured by lip or canopy extraction and ducted in stainless or FRP to a mist eliminator. SBKJ fabricates the tumbling and degrease hood bodies and mains in 304 stainless on the SBAL-V and SBFB-1500, with the appropriate combustible-stream construction under AS 1940 for the solvent variant and corrosion-resistant stainless for the alkaline variant.

13. Hazardous-area classification across the fastener plant

Pulling the hazardous-area picture together, a fastener and spring plant triggers AS/NZS 60079 classification at a set of distinct locations, each driving Ex-rated electrical equipment, conductive bonded ductwork, and gas or dust detection. On the gas-and-vapour side under AS/NZS 60079.10.1: the endothermic-gas generator room is classified for hydrogen (4 percent LEL) and carbon monoxide; the solvent-degrease tank area is classified for flammable VOC vapour; the immediate area around any hot quench-oil reservoir is assessed for oil-vapour risk; and the pickle line is assessed for the hydrogen evolved at the steel surface. On the dust side under AS/NZS 60079.10.2: the interior of the soap-dust collector, the grinding-dust collector and the shot-peening-dust collector, and the dust transport lines feeding them, are classified for combustible dust.

For each classified zone the duct designer must do three things. First, confirm that every electrical device in or near the zone — fan motors, dampers, instrumentation, sensors, lighting — is Ex-rated to the appropriate protection level. Second, ensure the ductwork serving the zone is conductive throughout (304 or 316 stainless is the default), continuously bonded with conductive flange gaskets at every joint, externally bonded with copper or stainless strap to the building earth grid, and verified at commissioning to less than 1 ohm to ground at every section — so the duct cannot accumulate a static charge that becomes an ignition source. Third, place the engineered deflagration protection — explosion-vent panels per NFPA 68, isolation valves per NFPA 69 — between the dust collector and the inbound duct so that a deflagration in the collector cannot propagate back through the ductwork into the workshop. SBKJ fabricates every hazardous-area duct section to this specification, delivering each with its earth-bonding verification record for the AS/NZS 60079 documentation pack.

14. Combustible dust — deflagration protection on the collector and duct

The combustible-dust hazard in a fastener and spring plant deserves its own treatment because it spans several process areas and because the consequences of getting it wrong are catastrophic. The combustible dusts are the soap-lube dust from cold forming and dry wire drawing (organic, combustible), the fine metal dust from cold heading and slug trimming, the metallic grinding dust from spring end-grinding, and the metallic shot-and-media fines from shot peening. Metal dusts in particular combine a high surface area with a low minimum ignition energy and a high deflagration index, meaning a suspended cloud can ignite from a small spark and propagate a destructive pressure wave.

The engineering response follows the hierarchy of AS 3957, AS/NZS 60079.10.2, NFPA 68 and NFPA 69. The first principle is to minimise accumulation — capture the dust efficiently at source so it never builds up on overhead surfaces (a layer of combustible dust on a beam is a secondary-explosion fuel). The second is to keep the dust entrained in the duct at adequate transport velocity (8 to 12 m/s for these dusts) so it does not drop out and pool. The third is to protect the collector: a wet collector for the highest-risk metal dusts (drowning the deflagration in water), or a dry collector fitted with explosion-vent panels (NFPA 68) that relieve a deflagration safely to a clear outdoor zone, plus inerting where justified (NFPA 69). The fourth is isolation: a fast-acting isolation valve (chemical-suppression, flap or rotary) between the collector and the duct main, interlocked to a flame or pressure sensor in the collector, that closes on the first sign of a deflagration and stops the flame front propagating back through the ductwork into the occupied workshop. The fifth is bonding and grounding of every metre of duct so static cannot become an ignition source. SBKJ fabricates the combustible-dust mains and collector transitions in conductive bonded stainless on the SBFB-1500 and SB-ZF1500, built to integrate directly with the isolation valves and vented collector that the dust-hazard engineer specifies.

15. WES dilution and capture-velocity calculation for the fastener plant

The numbers that drive the duct sizing come from two calculations: the localised-exhaust capture-velocity calculation at each hood, and the general dilution-ventilation calculation for the contaminants that escape capture. Both are anchored to the SafeWork Australia workplace exposure standards for the specific contaminants and to AS 1668.2.

For localised exhaust, the governing figure at each hood is the capture velocity — the air velocity at the point of contaminant release needed to draw the contaminant into the hood against the disrupting air currents of the workshop. For an enclosing oil-mist canopy over a cold header, where the hood substantially surrounds the source, a face velocity of 0.5 to 1.0 m/s is sufficient; for a lip-extraction slot over an open pickle or plating tank, where the hood must reach across the tank surface, the capture velocity at the far edge must be maintained against cross-draughts, typically requiring 0.5 m/s or more at the most distant point of release. The hood airflow is then the capture velocity multiplied by the relevant area, and the duct is sized to carry that airflow at the contaminant-appropriate transport velocity — 7 to 10 m/s for oil mist, 8 to 12 m/s for combustible dust, lower for clean acid-gas streams.

For dilution ventilation, the principle is to supply enough clean air to dilute any escaped contaminant below its workplace exposure standard. The required dilution airflow is the contaminant generation rate divided by the target concentration (the WES, with a safety factor). This matters most for carbon monoxide in the heat-treatment hall: with a WES of 30 ppm and a continuous low-level release from furnace openings, the dilution-air figure is substantial and is the dominant ventilation load in that hall. The relevant standards anchor the targets: oil mist 5 mg/m3, hydrogen chloride 5 ppm, sulphuric and chromic acid mist 0.2 mg/m3, hexavalent chromium 0.0003 mg/m3, carbon monoxide 30 ppm, carbon dioxide 5000 ppm, sodium hydroxide alkaline mist 2 mg/m3, nickel 0.1 mg/m3 insoluble, zinc oxide fume 5 mg/m3, and hydrogen managed below 4 percent lower explosive limit. Every duct branch SBKJ fabricates is sized from the airflow that these capture-velocity and dilution calculations produce, and is validated at commissioning by breathing-zone air sampling against each standard.

16. The SBKJ machine line for fastener, spring and wireform duct fabrication

For an Australian fabricator or mechanical contractor serving the fastener, spring and wireform sector from Box Hill North VIC, the practical SBKJ machine envelope to cover the full duct demand across cold forging, heat treatment, pickling, plating, coating and spring work is built from the SBKJ Product Catalog 2026 range. Each machine maps to a specific duct-fabrication role in this sector.

• SBAL-V with 304/316 stainless option — the workhorse auto duct line for the oil-mist canopies over cold headers, thread rollers and spring coilers, the supply-air and general extract ductwork, and the bulk of the stainless duct across the plant. Production envelope 0.7–1.6 mm 304/316 stainless plus galvanised and aluminised, with TDF flange forming, surface-protection film and stainless-specific tooling. Forms rectangular hood bodies and TDF-flanged transitions at 4–6 m/min on 1.0 mm stainless.
• SBAL-III — the heavy-gauge auto duct line for the 1.6–2.0 mm work: the 316 stainless quench-oil mist canopies, the high-temperature furnace burn-off flue hoods, the heat-treat exhaust mains downstream of the furnace cooling section, and the coating-oven exhaust risers.
• SBSF-1525 — the longitudinal stitch welder that produces continuously TIG-welded 316L stainless duct for the oil-tight hood seams, the corrosion-resistant pickling and plating stainless transitions, and the oil-bearing phosphate and zinc-flake streams. Critical wherever the seam must be hermetic against oil mist or residual acid mist.
• SB-ZF1500 — the in-line longitudinal stitch welder running with the SBFB-1500 to deposit a continuous TIG bead on spiral mains 1000–1500 mm. Used on the combustible soap-dust, grinding-dust and shot-peening-dust mains for a sealed conductive seam, and on the acid-fume stainless stack sections.
• SBFB-1500 — the spiral tubeformer producing round duct 80–1500 mm diameter in galvanised, aluminised or stainless at 0.6–1.5 mm. The single most-used machine for this sector: oil-mist mains, soap-dust and oil-mist wire-drawing mains, combustible grinding and peening dust mains, and acid-fume stack spools.
• SBPC1500 — the plasma cutter for custom transitions in 316L, 309/310S high-temperature stainless and heavier plate up to 25 mm, used for the furnace burn-off and quench hood plenums, refractory-anchor stud plates, scrubber-interface geometry and stack-head transitions.
• SBLR-600 — the rollformer and lock former for Pittsburgh-lock and snap-lock seams in rectangular duct, with heavy-gauge tooling for 1.2 mm stainless on the cleanroom-clean supply-air, wire-drawing hood and coating-line transition work.
• SBTF-1500/1602/2020 — the TDF flange line for trunk mains and large transitions up to 2000 mm diameter, used for centralised collector trunk mains, large dilution-extract mains in the heat-treatment hall, and the make-up-air supply trunk.

The combined machine fit delivers the production envelope to cover every duct requirement across every process zone in an Australian fastener, spring or wireform plant — from the oil-mist hall at Ajax Fasteners in Braeside VIC, through the heat-treatment lines of the Dandenong and Western Sydney clusters, the wire-drawing bays at Waratah InfraBuild in Newcastle, the pickling and plating shops, and the spring works of Wallaby Springs, Airdrome and Aus-Spring, to the Brisbane and Perth fastener operations and the broader national market.

17. Commissioning, measurement and verification (M&V)

Fabricating the ductwork is half the job; commissioning it and proving it works is the other half, and in a fastener plant the verification is what stands between the operator and a SafeWork notice. The commissioning sequence follows AS 4254 for the construction verification and AS 1668.2 for the performance verification, and it produces the documentation that feeds the operator's ISO 14001 and ISO 45001 management systems.

The construction-verification stage confirms what was built. Every steel duct branch is pressure-tested to 1.5 times its design pressure for 30 minutes per AS 4254. Every combustible-dust and hazardous-area duct has its earth bonding verified below 1 ohm at every flange with a hand-held resistance meter, and the result is recorded against the AS/NZS 60079 documentation. Every flexible connection on a hazardous-area circuit has its conductivity tested. Inspection and clean-out access ports are confirmed at 5 to 10 m intervals on every oil-mist and dust main per the safe-access principles of AS 4024.

The performance-verification stage confirms what it does. The system is balanced so that each hood draws its design airflow and each capture point reaches its design capture velocity, measured with a calibrated anemometer at every hood face and slot. The dilution-ventilation air-change rate in the heat-treatment hall is confirmed against the AS 1668.2 calculation. Then the proof: breathing-zone air sampling, taken by a NATA-accredited occupational hygienist, against each workplace exposure standard — oil mist below 5 mg/m3, hydrogen chloride below 5 ppm, sulphuric and chromic acid mist below 0.2 mg/m3, hexavalent chromium below 0.0003 mg/m3, carbon monoxide below 30 ppm, sodium hydroxide alkaline mist below 2 mg/m3, nickel below 0.1 mg/m3. The fixed gas-detection (carbon monoxide and hydrogen LEL) is function-tested and its alarm and fan-interlock logic confirmed. The final NATA-certified commissioning report ties every duct branch back to its process zone, its dominant contaminant, its workplace exposure standard, its AS 1375 / AS 3780 / AS 3957 / AS/NZS 60079 classification, and its mill certificate — the foundation document the operator integrates into the ISO management system and presents to the regulator.

18. Standards and exposure-limit reference table

The following consolidates the standards and exposure limits referenced throughout this guide, as a quick-reference for the duct designer and the commissioning hygienist.

• AS 1668.1 — fire and smoke control in air-handling systems (fire dampers, shutdown logic).
• AS 1668.2 — mechanical ventilation; dilution and make-up air; capture and dilution calculations against WES.
• AS 4254.1 / AS 4254.2 — sheet-metal and flexible duct construction; pressure-test certification.
• AS 1530.4 — fire-resistance of building elements; fire-rated penetrations at fire-compartment boundaries.
• AS 1375 — code of practice for heat-treatment furnaces; controlled atmosphere, flame curtain, purge, burn-off.
• AS 1940 — flammable and combustible liquids; oil-mist and solvent-degrease combustible-stream ductwork.
• AS 3957 — dust hazard and fire-spread control; combustible soap, metal, grinding and peening dust.
• AS 3780 — corrosive substances; pickling and plating acid-fume exhaust material selection.
• AS/NZS 60079 — explosive atmospheres; generator-room and solvent gas zones, combustible-dust collector zones.
• AS/NZS 2243.8 — fume cupboards for plating-shop laboratory and chemistry benches.
• AS 4024 — machinery safety; fan guarding and safe-access clean-out ports.
• AS/NZS 1715 / AS/NZS 1716 — respiratory protective equipment selection and specification.
• AS 1110 / AS 1111 / AS 1112 — fastener product standards (hexagon bolts, screws, nuts); property classes driving heat-treatment demand.
• NCC Section J — building energy efficiency; heat-recovery and fan-energy decisions.
• ASHRAE 62.1 — ventilation for acceptable indoor air quality (office and amenity zones).
• ISO 9001 / ISO 14001 / ISO 45001 — quality, environmental and OHS management systems.
• NFPA 68 / NFPA 69 — deflagration venting and explosion prevention by inerting and isolation (combustible-dust collectors).
• WES — oil mist 5 mg/m3 (cold forging, quench, coiling, wet wire drawing, phosphate-and-oil).
• WES — carbon monoxide 30 ppm TWA, 60 ppm STEL (endothermic-atmosphere heat treatment).
• WES — hydrogen chloride 5 ppm peak (hydrochloric pickling).
• WES — sulphuric acid mist 0.2 mg/m3 (sulphuric pickling) and chromic acid mist 0.2 mg/m3.
• WES — hexavalent chromium Cr(VI) 0.0003 mg/m3 (chrome plating and chromating — the lowest limit in the plant).
• WES — sodium hydroxide alkaline mist 2 mg/m3 (zinc and zinc-nickel plating, aqueous degrease).
• WES — nickel 0.1 mg/m3 insoluble (zinc-nickel plating).
• WES — zinc oxide fume 5 mg/m3 (hot-dip galvanising cross-reference).
• WES — carbon dioxide 5000 ppm (heat-treatment hall dilution check).
• Hydrogen lower explosive limit 4 percent in air (endo-gas generator and pickle-line evolved hydrogen).

19. Energy, heat recovery, Green Star and NABERS

A fastener plant moves enormous volumes of conditioned air through its localised exhaust, and every cubic metre extracted must be replaced by tempered make-up air, so the energy implications under NCC Section J are significant. The two largest opportunities are recirculation and heat recovery. Where an oil-mist stream is cleaned to a high standard through a coalescing collector and a HEPA polish, the air can be recirculated back into the hall rather than discharged, eliminating the make-up-air heating or cooling load for that volume — subject to a careful contaminant-breakthrough monitoring regime so that a collector failure cannot recirculate oil mist. Where exhaust must be discharged — the acid-fume and carbon-monoxide streams cannot be recirculated — an air-to-air heat exchanger recovers the thermal energy from the warm exhaust into the incoming make-up air, with corrosion-resistant heat-exchanger materials on the acid-fume streams.

For the broader building, Green Star (the Green Building Council of Australia rating) and NABERS (the National Australian Built Environment Rating System) increasingly feature in the procurement and lease decisions of larger manufacturers, and an efficient, well-recovered ventilation system contributes to both. The heat-treatment hall, with its furnaces and quench tanks, is a major heat source that can be tapped for space heating or process water preheating elsewhere in the plant. SBKJ fabricates the heat-recovery duct transitions, the recirculation and discharge dampers, and the corrosion-resistant exchanger interfaces in stainless, integrating the energy-recovery hardware into the exhaust topology so the plant meets its Section J obligation without compromising contaminant control.

20. Accessibility, amenity and DDA compliance (AS 1428.1)

Beyond the production stages, a fastener plant has offices, amenities, a quality laboratory and visitor spaces that must meet the accessibility requirements of the Disability Discrimination Act and AS 1428.1 (design for access and mobility). The ventilation of these zones is conventional comfort HVAC under AS 1668.2 and ASHRAE 62.1, but the integration matters: the office and amenity zones must be kept at positive pressure relative to the production stages so that oil mist, acid fume and carbon monoxide cannot migrate into the occupied non-production spaces, and the accessible amenities must be ventilated to the relevant rate. The DDA-compliant access routes also constrain where ductwork, plant and access doors can be placed at low level. SBKJ fabricates the comfort-HVAC supply and return ductwork for these zones on the SBAL-V and SBLR-600 alongside the process exhaust, ensuring the whole-building air-balance keeps the occupied zones clean and the access routes clear.

21. The Australian fastener and spring sector — demand, local content and industry bodies

The Australian fastener, spring and wireform sector sits at the intersection of several demand drivers that are strengthening the case for local manufacturing and, with it, for plant investment that includes properly engineered HVAC. Construction demand — structural bolts for steel framing, fasteners for the building products supply chain, and the fixings consumed by the residential and commercial pipeline — is the largest single end market. Automotive and heavy-vehicle demand, the historic foundation of Ajax Fasteners and the Braeside manufacturing belt, continues through component manufacturing, heavy-vehicle and trailer assembly, and the aftermarket. Agricultural and mining-equipment demand consumes large structural and specialty fasteners. Defence and rail demand, with their local-content and traceability requirements, increasingly favour Australian-made and Australian-certified fasteners.

That local-content trend is the structural tailwind for the sector. Government procurement rules favouring Australian Industry Participation, the resilience lessons of recent global supply-chain disruption, and the certification and traceability advantages of local manufacture all push toward onshore production of structural and safety-critical fasteners — which is exactly the work that requires hardening, plating and the full HVAC stack described in this guide. The industry bodies that represent and standardise the sector include the Australian Fastener Council (representing fastener manufacturers and distributors and advocating for the sector), the Australian Steel Institute (ASI, covering the steel supply chain that feeds wire and fastener production), and the Australian Industry Group (Ai Group, the peak manufacturing body), with Standards Australia publishing the AS 1110/1111/1112 product standards and the AS ventilation and safety standards. For SBKJ, this strengthening local-manufacturing case is the reason the fastener and spring sector is a priority market: every new or upgraded Australian fastener line, and every plant retrofitting its heat-treatment, pickling or plating exhaust to meet current SafeWork expectations, is a duct-fabrication opportunity.

22. Competitive positioning — why fabricate locally

The case for an Australian fabricator owning the SBKJ machine line to serve this sector rests on three things that an importer of finished ductwork cannot match. The first is responsiveness: fastener-plant HVAC is full of custom geometry — bespoke quench-mist canopies, scrubber-interface transitions, furnace burn-off hoods, refractory-anchor plates — and a local fabricator with the SBPC1500 plasma cutter and the SBAL/SBFB forming lines can turn a measured site condition into a fabricated, pressure-tested, documented duct section in days, not the months of an import lead time. The second is documentation: the AS 4254 pressure test, the AS/NZS 60079 earth-bonding record, the mill-certificate traceability and the NATA commissioning report are produced as the work is fabricated, in the format the Australian operator needs for the SafeWork and ISO audit — not retrofitted onto an imported product. The third is service life: a fabricator who understands that the oil-mist duct must be bare and cleanable, that the acid-fume interface must be 316L, that the combustible-dust main must be bonded, and that the quench hood must be welded oil-tight, builds ductwork that survives the service rather than failing in its first year.

SBKJ supplies the machine line that gives the Australian fabricator this capability. From Box Hill North VIC the SBKJ engineering team supports fabricators and mechanical contractors across the country with machine supply, application engineering for the specific contaminant streams of the fastener and spring sector, commissioning support, and ongoing technical advisory. The SBAL-V, SBAL-III, SBSF-1525, SB-ZF1500, SBFB-1500, SBPC1500, SBLR-600 and SBTF-1500/1602/2020 lines together cover every duct requirement from the cold-forging hall to the plating-shop stack.

23. AS/NZS compliance checklist for fastener and spring duct commissioning

A short-form compliance checklist for fastener, spring and wireform ductwork commissioning, suitable for inclusion in the handover documentation pack:

• AS 1668.2 mechanical ventilation — design extract, capture-velocity and make-up-air calculations documented for every process zone.
• AS 1668.1 fire and smoke control — fire dampers and shutdown logic documented at every fire-compartment penetration.
• AS 4254.1 / AS 4254.2 duct construction — pressure-test certificates at 1.5x design pressure for 30 minutes on every steel branch.
• AS 1530.4 fire resistance — fire-rated penetrations certified at fire-compartment boundaries.
• AS 1375 heat-treatment furnaces — burn-off flue capture, flame-curtain and dilution documented for every controlled-atmosphere furnace.
• AS 1940 flammable and combustible liquids — oil-mist, quench-mist and solvent-degrease combustible-stream ductwork documented; fire dampers and clean-out access confirmed.
• AS 3957 dust hazard — combustible soap, metal, grinding and peening dust hazard analysis with deflagration-protection chain documented.
• AS 3780 corrosives — pickling and plating acid-fume material selection (FRP/PP/PVC wet runs, 316L interfaces) documented.
• AS/NZS 60079.10 hazardous-area classification — generator-room and solvent gas zones and combustible-dust collector zones mapped with Ex-equipment selection.
• AS/NZS 2243.8 fume cupboards — capture velocity documented for plating-shop laboratory and chemistry benches.
• AS 4024 machinery safety — fan guarding and safe-access clean-out ports at 5–10 m intervals confirmed.
• AS/NZS 1715 / AS/NZS 1716 RPE — PAPR and acid-gas and dust respirator selection documented for every captured task.
• AS 1110 / AS 1111 / AS 1112 — fastener product context documented to confirm heat-treatment scope and HVAC demand.
• NFPA 68 / NFPA 69 — deflagration venting and isolation documented for every combustible-dust collection system.
• Breathing-zone air sampling — NATA-certified results against oil mist 5, HCl 5 ppm, acid mist 0.2, Cr(VI) 0.0003, CO 30 ppm, NaOH 2, nickel 0.1.
• Gas detection — fixed CO and hydrogen LEL heads function-tested with alarm and fan-interlock logic confirmed.
• Earth bonding — verified below 1 ohm at every flange on combustible-dust and hazardous-area ductwork.
• ISO 9001 / ISO 14001 / ISO 45001 — commissioning documentation integrated into the operator's management systems.
• NCC Section J — heat-recovery and fan-energy compliance documented.
• NATA certification — final commissioning balance and breathing-zone sampling certified by a NATA-accredited laboratory.

Compliance documentation is the bridge between the fabricated ductwork and the operator's ongoing regulatory obligation. Every length of ductwork SBKJ supplies to an Australian fastener, spring or wireform fabricator is delivered with mill certificate, fabrication date, pressure-test record, earth-bonding verification at every flange and AS-compliant labelling — the foundation paperwork the operator integrates into the SafeWork, ISO 14001 and ISO 45001 audit pack.

24. Closing — SBKJ engineering support for Australian fastener manufacturing

The Australian fastener, spring and wireform sector is in a period of renewed investment, driven by construction demand, automotive and heavy-vehicle manufacturing, the strengthening local-content case in defence and rail, and the steady tightening of SafeWork expectations around oil mist, carbon monoxide, acid fume and hexavalent chromium. Every new or upgraded line — a fresh bank of cold headers at a Braeside or Dandenong plant, a new continuous hardening furnace, a re-engineered pickling or plating exhaust, a spring works adding shot-peening capacity — exposes the limits of generic commercial HVAC and demands purpose-engineered ductwork that meets the full standards stack outlined in this guide. The SBKJ Group engineering team in Box Hill North VIC is positioned to support Australian fabricators and mechanical contractors serving this sector with machine supply (SBAL-V, SBAL-III, SBSF-1525, SB-ZF1500, SBFB-1500, SBPC1500, SBLR-600, SBTF-1500/1602/2020), application engineering, 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 sector-specific reference samples covering 304 and 316 stainless oil-mist canopies, 316L corrosion-resistant acid-fume transitions, high-temperature furnace and quench-hood geometry, and combustible-dust bonded spiral. Pre-show meetings with Australian fastener and spring manufacturers, mechanical contractors and machine OEM partners are scheduled across the week.