Asphalt, Bitumen & Hot Mix Asphalt HVAC Duct Guide — Boral, Hanson, Downer, Fulton Hogan, Viva Energy Geelong, PMB & Crumb Rubber

Why asphalt and bitumen HVAC is its own discipline

An asphalt plant is one of the few industrial environments where four different workplace hazards stack on top of each other in a single shift: respirable crystalline silica from the aggregate, benzo[a]pyrene from heated bitumen fume, styrene and butadiene from polymer modification, and combustible dust from recycled asphalt pavement, crumb rubber and fly ash co-additions. Each of those hazards individually would justify a dedicated engineering control programme. Stacked together, on a plant that is typically running 80-500 tonnes per hour of finished hot mix asphalt through a 160-180°C mix tower, they form the toughest occupational hygiene problem in Australian heavy industry behind underground hard-rock mining.

Process gas temperatures complicate everything. Aggregate enters the parallel-flow or counter-flow drum dryer wet and cold, exits the dryer at 150°C after a 2-3 minute pass through the burner zone, and lands in the hot bin at 160-180°C ready for mixing. Heated bitumen storage tanks sit at 150-180°C continuously to keep the binder pumpable. Polymer-modified bitumen blending vessels run 170-190°C with shear mixers driving SBR, EVA or EPDM into solution. The mix tower paddle deck sees 160-180°C finished asphalt on the load-out conveyor. The mix tower silos hold 1,000-2,000 tonnes of finished asphalt at 160-180°C waiting for trucks. Add the LPG or natural gas burner on the dryer, the diesel fuel storage and the heated bitumen vapour mass, and you have an AS/NZS 60079 hazardous area dossier that runs to dozens of pages.

What sits on the HVAC contractor's side of the line is just as important as the welded process duct: the control room, the weighbridge office, the laboratory, the lunch room, the change rooms, the maintenance workshop and the localised exhaust ventilation (LEV) at every fume and dust source. These are conventional galvanised sheet-metal duct systems fabricated to AS/NZS 4254-1, with 316L stainless reaches into the bitumen LEV zones. They are exactly what SBKJ auto duct lines, spiral tubeformers and plasma cutting machinery are designed to make. The trick is knowing where the scope split sits and what material grade applies to each section, because mixing them up loses money on quoting and creates a compliance failure at commissioning.

Australian asphalt and bitumen operators — who is buying HVAC duct

Australia's asphalt and road surfacing market is concentrated in five major listed operators plus a handful of independents and a tight set of bitumen refinery suppliers. Comfort HVAC duct demand and process LEV duct demand sit across every site, and the maintenance and shutdown rhythm at the larger sites is the volume driver for any HVAC contractor pursuing this market.

Boral Asphalt (ASX:BLD), headquartered in Sydney, is Australia's largest asphalt producer with more than 100 plants nationwide. Boral Asphalt operates mix plants and Boral Bitumen tank farms at every major capital and dozens of regional centres. Headline sites include Mt Coot-tha in Brisbane, Coolaroo in Melbourne, Casula in Sydney, plus operations in Adelaide, Perth and Hobart. Boral is also Australia's largest road construction materials producer, with vertically integrated aggregate quarries (Boral Quarries) and ready-mix concrete (Boral Concrete) attached to many asphalt sites. The Boral Asphalt network is the single largest source of asphalt plant HVAC duct demand in Australia, both for new plant build and for shutdown refurbishment.

Hanson Asphalt (HeidelbergMaterials/ASX:HAN), the second-largest national asphalt producer, runs a national plant network operated alongside Hanson Concrete ready-mix and Hanson Quarries aggregate supply. Hanson runs both batch plants and drum mix plants, with shutdown cycles aligned to the cement and concrete sister business. Hanson Asphalt sites add steady comfort HVAC and LEV duct demand at the major capital city operations.

Adbri (ASX:ABC, formerly Adelaide Brighton) operates asphalt production alongside its cement, aggregate and lime businesses at Birkenhead SA and Cockburn Cement WA. Adbri also holds Burnett Lime and supplies fines, lime fillers and supplementary cementitious material into asphalt production locally and into export markets.

Downer EDI Road Services (ASX:DOW) is Australia's largest road maintenance contractor, operating more than 100 asphalt plants across Brisbane, Sydney, Melbourne, Perth, Adelaide, Hobart and Darwin. Downer Road Services holds major long-term maintenance contracts with NSW RMS, VicRoads, QLD TMR, Main Roads WA, DPTI SA and TasRoads, generating a steady backlog of plant and infrastructure work that drives HVAC duct demand at the asphalt plant sites and at the road maintenance depot offices.

Fulton Hogan (ASX:FHL) is the Australian-New Zealand road construction, asphalt, bitumen and aggregate producer, headquartered in Auckland NZ with major operations in Sydney, Melbourne, Brisbane, Perth, Adelaide, Hobart and regional centres. Fulton Hogan is particularly strong in regional and rural pavement contracts and adds asphalt plant demand outside the metro corridors.

Independent and specialist operators include Pioneer Construction Materials, Bedrock Asphalt Geelong, Pioneer Asphalt, Holcim Australia Asphalt, CCS Civil Construction Services, BMD Construction (Brisbane infrastructure including Cross River Rail and Brisbane Olympic 2032 venues), John Holland CIMIC (ASX:CIM, including Melbourne Tunnel and Sydney rail/road tunnels), Lendlease, Multiplex, McConnell Dowell, Acciona, Lavan and Plenary Group PPP highway infrastructure consortia. Cardno Holdings provides infrastructure consulting across the sector.

Polymer-modified bitumen (PMB) is dominated by SAMI Bitumen Technologies, with PMB blending plants in Sydney, Melbourne, Brisbane, Perth and Adelaide producing SBR (styrene-butadiene rubber), EVA (ethylene-vinyl acetate), EPDM (ethylene propylene diene monomer) and crumb rubber polymer blends. Puma Bitumen and Shell Bitumen (produced under licence at the Viva Energy Geelong Refinery) compete in the same segment, with BP Bitumen historically supplying out of the BP Brisbane Lytton refinery.

Crumb rubber asphalt producers include Tyrecycle (now Veolia), Green Distillation Technologies (GDT) pyrolysis crumb, ECOFlex Crumb Rubber Pty Ltd and Bitumen Industries Australia (BIA). The closed Devine Tyrecycle plant in NSW is no longer operating. Tyre Stewardship Australia (TSA) coordinates the national tyre take-back and recycling scheme.

Bitumen refinery capacity in Australia is now concentrated at the Viva Energy Geelong Refinery (ASX:VEA), the Shell-licensed bitumen producer covering heavy fuel oil, paving bitumen, industrial bitumen, marine bitumen, aviation jet fuel and avgas. Geelong is the single largest bitumen production site in Australia. Ampol's Lytton Brisbane Refinery (formerly Caltex) is closing in stages for biofuel transition. The BP Kwinana Refinery WA closed in 2021. With domestic refining contracting, imported bitumen via Geelong and bulk import terminals at Port Kembla, Newcastle, Brisbane and Fremantle increasingly supplements local production.

Concrete batching and ready-mix production sits parallel to asphalt at most major sites: Boral Concrete, Hanson, Holcim Australia, Adbri, plus independents such as Bayside Group and ConChem. Aggregate quarries supplying both asphalt and concrete include Boral Quarries, Hanson Quarries and Adbri operations under varying state mining regulators (NSW Mining, VIC Mining, QLD MEMR, WA Mining, SA Mining, TAS Mining), all generating silica RCS and basalt dust requiring NFPA 660 and AS 3957 controls.

Industry bodies coordinating practice across the sector include the Australian Asphalt Pavement Association (AAPA) as the asphalt industry peak body, Austroads as the peak body of Australian and New Zealand road authorities (publishing the AGPT — Austroads Guide to Pavement Technology, APRG Austroads Pavement Research Group reports, the AGPT01-14 series and TS-02 Test Specifications), Roads Australia (RA), the Cement Concrete & Aggregates Australia (CCAA), the Minerals Council of Australia (MCA) covering aggregate quarries, the NHVR National Heavy Vehicle Regulator, the NRSPP National Road Safety Performance Programme, Tyre Stewardship Australia (TSA) and the Bitumen Industries Australia (BIA). State road authorities — NSW RMS, VicRoads, QLD TMR, Main Roads WA, DPTI SA, TasRoads, Roads ACT and NTG Transport — set construction and material specifications via the Austroads AGPT framework and the IRF (International Road Federation) cross-references.

Process zones — the asphalt plant duct map

To know where the HVAC duct sits on an asphalt plant, you need to know where the process gas, dust and fume sources are. A modern Australian asphalt batch plant or drum mix plant runs through ten distinct process zones, each with its own ventilation, LEV, hazardous area and dust hazard signature.

Aggregate stockpile, hopper and cold feed. Quarried aggregate (silica sand, basalt, limestone, dolomite, blue metal), recycled asphalt pavement (RAP) and crumb rubber are stored in open stockpiles or covered bays adjacent to the plant. Front-end loaders or feed conveyors transfer aggregate to cold feed bins (typically 4-8 bins per plant). Each bin discharges through a vibratory feeder onto a gathering conveyor. Cement and fly ash co-additions are stored in dedicated silos. This zone is the dominant source of fugitive silica RCS dust, with respirable quartz fines from sand and basalt being the critical hazard at 0.05 mg/m³ TWA. AS 3957 dust hazard practice applies: enclosure of all transfer points, hood capture at the feeder discharge, conveyor belt skirting, dust collector aspiration at every transfer point. NFPA 660 combustible dust applies where RAP, crumb rubber, cement or fly ash co-additions are present. Engineering controls include a bag filter dust collector at the cold feed building, isolated rotary lock airlocks between the dust collector and the silo, and AS 1715 P2/P3 respiratory protection at the operator station.

Aggregate dryer and rotary drum dryer. Aggregate from the cold feed gathering conveyor passes through an elevator into the rotary drum dryer, the heart of any asphalt plant. Drums run parallel-flow (counter to gas, same direction as solids) or counter-flow (gas opposing solids). Gas-fired LPG or natural gas burners (sometimes heavy fuel oil legacy) heat the drum interior to 150°C aggregate exit temperature and 350-450°C internal gas temperature. The drum dryer is the dominant heat source on the plant. Dryer exhaust gas carries silica, basalt and limestone dust at 50-200 g/Nm³, plus CO from incomplete combustion, NOx from high-flame-temperature burner zones, and trace VOCs from any RAP introduction. Dryer exhaust ducting is welded heavy fabrication in 4-6 mm carbon steel, transitioning to 309S or 310S stainless near the burner zone where surface temperature exceeds 300°C. NFPA 86 governs industrial oven design and applies to the dryer drum and burner skid. Hazardous area classification under AS/NZS 60079.10.1 makes the burner gas train Zone 1 and the drum body Zone 2. Heat recovery from dryer exhaust to pre-heat aggregate or RAP is increasingly common on new plants — adding additional duct between the cyclone outlet and the heat exchanger.

Hot mix asphalt (HMA) batch tower and drum mix plant. Heated aggregate from the dryer is screened into hot bins by particle size, weighed in proportion, and dumped into the pugmill mixer where heated bitumen is sprayed in. Batch plants (Marini, Astec, Lintec, Ammann) produce discrete 1-3 tonne batches at typically 60-90 second cycles. Continuous drum mix plants (Astec, Ammann, Marini, Caterpillar, Cedarapids) introduce bitumen directly into the second half of a long drum, producing 80-500 tonnes per hour without batching. The mix tower is the source of bitumen fume — benzo[a]pyrene, polycyclic aromatic hydrocarbons, bitumen aerosol mist — and is the primary worker-protection LEV zone. Pugmill paddle deck local exhaust ventilation, mix tower silo top vent extraction and finished asphalt truck load-out hood extraction all feed into a central scrubber, thermal oxidiser or bitumen fume condenser. AS/NZS 60079 Zone 2 applies to the mix tower deck during normal operation. Trunk LEV duct is 316L stainless 1.5 mm because heated bitumen condensate accumulates on duct internal surfaces and is highly difficult to remove from galvanised coating.

Bitumen storage and heated tank farm. Bitumen storage tanks (50,000-2,000,000 L capacity, typically vertical insulated atmospheric tanks) hold the binder at 150-180°C continuously. Tank heating is by hot oil coil, electric immersion or steam coil. Tank piping is heated and insulated. Tank breather vents handle thermal breathing and working losses. The tank farm is classified Zone 1 hazardous area within 4.5 m of any vent, sample port, manhole or pump seal under AS/NZS 60079.10.1, and Zone 2 in the bund and pump farm extending 7.5-15 m further. All electrical equipment in zone — ventilation fan motors, level transmitters, sample valve solenoids, light fittings, junction boxes — must be Ex-rated and certified under IECEx or ANZEx. AS 1940 governs flammable liquid storage. Vent stacks are equipped with ISO 16852 flame arresters and knock-out pots. Heated piping is welded carbon steel insulated and heat-traced. SAMI Bitumen Technologies, Puma Bitumen and the Viva Energy Geelong Shell Bitumen operations all run multi-tank farms with 200,000-2,000,000 L individual tank capacity.

Polymer-modified bitumen (PMB) blending. PMB blending vessels add SBR (styrene-butadiene rubber, sometimes called Stylink or Spread brand), EVA (ethylene-vinyl acetate), EPDM crumb rubber or virgin polymer to heated bitumen at 170-190°C under high-shear mixing. Master batch hoppers, continuous mixer skids, shear stages and ageing tanks each generate styrene off-gas (WES 50 ppm STEL), butadiene off-gas (WES 1 ppm STEL — extremely low because butadiene is IARC Group 1), polymer fume and bitumen aerosol. Each addition point, manhole and sample port is a Zone 1 LEV source. LEV duct in 316L stainless. AS 1141.5 and AS 1141.6 govern aggregate testing; AS 3568 covers PMB specifications; AS/NZS 2008.1 and AS 2008.1 set bitumen testing. SAMI Bitumen Technologies operates PMB blending plants in all major Australian capitals, generating substantial LEV duct fabrication demand on shutdown and expansion projects.

Crumb rubber asphalt processing. Crumb rubber producers handle whole-tyre and shredded-tyre feedstock. Mechanical crumb production grinds tyres to 0.6-2 mm crumb under aspiration to capture rubber dust and steel tyre cord (separated via magnetic and density separators). Pyrolysis crumb (Green Distillation Technologies, GDT) thermally decomposes tyres at 400-600°C in inert atmosphere, producing syngas (H2, CO, CH4), bio-oil, recovered carbon black and steel cord. Mechanical crumb plants run NFPA 660 combustible dust controls; pyrolysis plants run NFPA 660 plus AS/NZS 60079 Zone 2 (or Zone 1 in immediate vicinity of pyrolysis reactor seals) for the syngas. Tyrecycle (Veolia), GDT, ECOFlex and Bitumen Industries Australia (BIA) all run different process configurations; engineering ventilation design follows the dust hazard analysis under NFPA 660 Chapter 7.

Slurry seal, microsurfacing, cold mix and emulsion. Boral, Downer, Fulton Hogan and Hanson all run cold mix asphalt, slurry seal, microsurfacing, chip seal and spray seal plants alongside the hot mix sites. Cationic and anionic bitumen emulsions (slow-set, rapid-set) handle in dedicated emulsion plants at 60-80°C — much lower temperature than HMA so the LEV duct sizing and material specification is less aggressive. AS 3568 spray seal, AS/NZS 4198 emulsion and AS 2150 chip seal cover the construction practice; LEV duct on the emulsion mixing skid is 304 or 316 stainless at 0.8-1.2 mm because cationic emulsion handling is corrosive to galvanised coating.

Asphalt laboratory and Marshall testing. Every asphalt plant has an attached laboratory running aggregate testing (AS 1141, AS 2150, AS 3568, AS 2008), Marshall stability and flow testing (AS 2891), Hveem testing (legacy), Superpave SHRP (Strategic Highway Research Program) tests, wheel tracking, rutting, stripping and adhesion testing. Lab bitumen samples are heated for testing, generating bitumen fume in the fume cupboard. AS/NZS 2982 governs fume cupboard construction. Lab LEV duct is 316L stainless on the fume cupboard exhaust, HEPA-filtered on the analytical instrument exhausts. Lab building HVAC is conventional galvanised duct.

Paving, road construction and field placement. Asphalt pavers (Caterpillar, Volvo, Vögele, Bomag, Dynapac, Hamm, Wirtgen) lay finished mix at 4-8 m wide paver widths. Screed, tamper and vibrator compact the laid mat. Pneumatic, static and vibratory rollers complete compaction. Finished mix is delivered to site in heated truck dump trailers (8-22 tonne capacity, Vawdrey or Maxitrans bodies). Field placement is outdoor and open air so the ventilation design problem is one of capture-at-source on the paver operator station only — there is no enclosed plant duct on the placement side. AS 2891 covers field testing. Traffic management compliance under NSW RMS, VicRoads, QLD TMR, Main Roads WA, DPTI SA and TasRoads governs the surrounding work zone.

Concrete batching and aggregate quarry (parallel adjacent). Most asphalt plants run a parallel ready-mix concrete batching plant on the same site, sharing aggregate stockpile and silo infrastructure. Boral Concrete, Hanson, Holcim Australia and Adbri all operate co-located asphalt-and-concrete plants. AS 1379 (concrete production), AS 3600 (concrete structural) and AS 5100 (bridge code) govern concrete; the asphalt plant LEV scope effectively co-mingles with the concrete batching plant LEV at the shared silos and weigh hoppers.

Asphalt plant HVAC duct — scope split and material map

The defining design problem on any asphalt or bitumen plant is the scope split between sheet-metal HVAC duct (SBKJ machinery scope) and welded heavy fabrication process duct (specialist welded shop scope). The split runs differently across the ten process zones and depends on duct temperature, abrasion exposure, hazardous area and material specification. Getting the split wrong is a six-figure pricing mistake.

The sheet-metal HVAC duct scope — what SBKJ duct lines fabricate — covers:

• Comfort HVAC supply and return duct in the control room, weighbridge office, laboratory, lunch room, change rooms, maintenance workshop and amenities buildings. Galvanised G275 or G300 sheet metal 0.6-1.0 mm in rectangular section to AS/NZS 4254-1; spiral round duct 1.0-1.5 mm to AS/NZS 4254-1 spiral schedule. Fabricated on SBKJ SBAL-V auto duct line plus SBTF-1500/1602/2020 spiral tubeformer.
• LEV duct to the bitumen mix tower paddle deck and load-out hood in 316L stainless 1.5 mm because bitumen aerosol condensate is sticky and corrosive. Fabricated on SBAL-V configured for stainless coil. SBPC1500 plasma cutting station handles the heavy plate cut-outs at the connection flanges.
• LEV duct to the bitumen tank manhole and sample port in 316L stainless 1.5 mm because heated bitumen vapour exposure builds benzo[a]pyrene residue on duct internal surfaces over time. Round spiral 200-400 mm diameter fabricated on SBFB-1500.
• LEV duct to PMB blending vessel manhole and addition hopper in 316L stainless 1.5 mm because polymer condensate (SBR, EVA, EPDM) is sticky and the duct sees frequent CIP cleaning cycles. SBAL-V configured for stainless coil.
• LEV duct to crumb rubber pre-feed weigh hopper and shredder station in mild steel 1.5 mm with antistatic earthing and NFPA 660 grounding/bonding. SBFB-1500 spiral former handles the round spiral 200-800 mm trunk runs.
• LEV duct to the laboratory fume cupboard in 316L stainless 0.8-1.0 mm to AS/NZS 2982. SBAL-V configured for stainless coil.
• Aggregate cold feed bin extraction duct from each transfer point hood up to the dedicated cold feed dust collector. Galvanised G275 or mild steel 1.5 mm in rectangular section, fabricated on SBAL-V. Trunk round spiral on SBFB-1500. Antistatic earthing.

The welded heavy fabrication scope — what SBKJ machinery does NOT cover — runs:

• Aggregate dryer exhaust ducting between the drum outlet and the primary cyclone. 4-6 mm carbon steel with chromium carbide overlay or basalt liners at bends. Temperatures 200-350°C internal at counter-flow drum or 120-180°C at parallel-flow drum.
• Cyclone to baghouse inlet duct in 4-5 mm carbon steel at 110-140°C with abrasion liners.
• Baghouse outlet to stack duct in 3-5 mm carbon steel at 90-110°C, sometimes 304 stainless on tall stacks where acid dewpoint margin is a concern.
• Bitumen tank manhole breather vent stack in welded carbon steel insulated and heat-traced with ISO 16852 flame arrester and knock-out pot.
• PMB blending vessel vent stack to thermal oxidiser or scrubber, in welded carbon steel or 316L stainless.
• Pyrolysis kiln seal vent (GDT plants) to flare or thermal oxidiser, in welded carbon steel.
• Heated bitumen process piping between tanks and the mix tower spray bars, in welded carbon steel insulated and heat-traced.

The boundary between scopes runs cleanly at the flange between the LEV ductwork on the user equipment and the trunk duct rising up to the central dust collector or thermal oxidiser. The HVAC contractor fabricates everything inside the building or up to the dust collector cyclone; the welded fabrication contractor takes over at the cyclone inlet flange.

Aggregate dust and silica RCS — the AS 3957 zone

Respirable crystalline silica (RCS) is the single most regulated worker exposure on an Australian asphalt plant, behind benzo[a]pyrene only when measured in terms of total population health impact. The Safe Work Australia Workplace Exposure Standard (WES) for RCS is 0.05 mg/m³ TWA — halved from the previous 0.1 mg/m³ limit. The reduction was driven by the Australian silicosis epidemic that emerged in the early 2020s, predominantly among engineered stone workers, and that led to the Engineered Stone Ban of 2024 (the world's first national ban on engineered stone benchtops). State silica regulators (NSW EPA, VIC EPA, QLD WHS, Safe Work Australia WES) have aligned around the 0.05 mg/m³ limit and routinely audit aggregate-handling sites against AS 3957 Dust Hazard Identification and Control practice.

The silica RCS source on an asphalt plant is the aggregate itself: quartz sand (typically 70-95% SiO2), basalt fines (3-15% free silica), limestone (1-5% free silica), dolomite (1-3% free silica), blue metal, scoria and gravel. Crushed and milled aggregate generates respirable fines down to PM4 (≤4 µm) which deposit in the alveolar region of the lung and cause silicosis. Every transfer point on the plant — front-end loader pickup, cold feed bin discharge, vibratory feeder, conveyor transfer, bucket elevator, screening deck, hot bin, mixer — is an RCS source.

Engineering controls follow the AS 3957 hierarchy and the NFPA 660 combustible dust practice. Source-level enclosures cover every transfer point with full hood capture. Capture velocity 1.0-1.5 m/s at the dust source per AS 3957. Capture flow rates 1,500-3,000 m³/h per transfer point. Trunk extraction duct sized for minimum transport velocity 18-22 m/s to keep silica fines suspended. The central dust collector (typically a pulse-jet baghouse with PTFE-membrane filter media at air-to-cloth ratio 1.0-1.5 m³/m²/min) discharges cleaned air at less than 30 mg/Nm³ total dust to atmosphere. Collected silica fines are returned to the asphalt mix as filler or disposed of as licensed waste.

NFPA 660 (the 2025 consolidated combustible dust standard, replacing the legacy NFPA 652, 654, 484, 61, 664 and 655) applies where the cold feed or aggregate handling contains combustible dust constituents. Pure aggregate (basalt, limestone, dolomite) is non-combustible. But RAP (recycled asphalt pavement) contains residual bitumen, RAP dust is combustible with measurable KSt values, and high RAP feed rates trigger an NFPA 660 dust hazard analysis (DHA) under Chapter 7. Crumb rubber pre-feed is unambiguously combustible. Cement and fly ash co-additions to asphalt mix are combustible at fine particle sizes. Engineering controls follow NFPA 68 deflagration venting on the central baghouse, NFPA 69 explosion prevention by isolation valves and inerting, and grounding/bonding on conveyors, silos and ductwork to dissipate static charge.

Administrative controls are the second layer: limit operator residence time at the cold feed deck, post AS 3957 dust hazard signage at all entry points, mandate AS 1715 P2 or P3 respiratory protection for any operator within capture range, and require medical surveillance for RCS-exposed workers per Safe Work Australia code. The respirator selection — P2 for low-duration exposures, P3 with positive pressure for high-exposure or maintenance work inside the dust collector — depends on the airborne RCS concentration after engineering controls.

Bitumen fume, benzo[a]pyrene and the IARC 1 carcinogen problem

Benzo[a]pyrene (BaP) is an International Agency for Research on Cancer (IARC) Group 1 confirmed human carcinogen, with regulatory status equivalent to asbestos, benzene and tobacco smoke. BaP is present in heated bitumen fume and polycyclic aromatic hydrocarbon (PAH) emissions from asphalt mixing, paving, milling and laboratory testing. The Safe Work Australia Workplace Exposure Standard for benzo[a]pyrene is 0.05 mg/m³ TWA — among the lowest WES values on the asphalt plant, equal to the silica RCS limit. Bitumen aerosol mist limit is 0.5 mg/m³ TWA (5 mg/m³ STEL inhalable). Heated bitumen vapour also evolves trace polycyclic aromatic content — naphthalene, anthracene, pyrene, benzo[a]pyrene, benzo[k]fluoranthene — across the PAH spectrum.

BaP exposure on an asphalt plant is concentrated at the mix tower paddle deck (where heated bitumen sprays into the pugmill at 160-180°C), the bitumen tank manhole and sample port (where the headspace vapour evolves continuously above the heated tank), the truck load-out hood (where finished asphalt at 160-180°C drops into the truck body), the PMB blending vessel manhole, and the laboratory fume cupboard during sample preparation. Each of these locations is an LEV capture point with engineering controls designed to drop airborne BaP below 0.05 mg/m³ TWA at the operator breathing zone.

LEV duct on every BaP capture point is 316L stainless 1.5 mm, fabricated on the SBKJ SBAL-V configured for stainless coil. The choice of 316L over galvanised is dictated by the heated bitumen aerosol condensate behaviour — sticky condensate accumulates on the duct internal surface, gradually builds a tar-like residue, and is impossible to remove from galvanised coating because of the zinc reaction with the aromatic content. Stainless duct can be cleaned mechanically and chemically without coating loss. Trunk duct material continues 316L all the way to the central scrubber, thermal oxidiser or bitumen fume condenser.

Capture velocity at each LEV point is 0.5-1.0 m/s through the hood face plus 1.5-2.5 m/s through the duct branch — typical for fume capture work per AS 1668.2. Flow rates 1,500-5,000 m³/h per capture point depending on hood face area. Hood face area sized for full capture of the fume rise plume above the bitumen surface, with a 200-400 mm fume hood lip overhang and a 30-45° hood face slope to encourage particle drop-out.

Trunk LEV duct sizing uses minimum transport velocity 12-15 m/s for bitumen aerosol mist — high enough to prevent fume condensation on duct walls, low enough to avoid excessive abrasion at bends. Bend radius-to-diameter ratios 1.5-2.0 (long-radius elbows). Cleaning access plates at every bend and tee for periodic mechanical cleaning. Drain points at low spots to collect condensate.

Discharge of LEV trunk to a thermal oxidiser, RTO (regenerative thermal oxidiser) or wet scrubber. Thermal oxidisers operate at 750-850°C with residence time 0.5-1.0 second, oxidising BaP and PAH content to CO2 and H2O. RTOs run at the same thermal conditions with regenerative ceramic heat recovery (95%+ thermal efficiency) and are increasingly the standard new-build choice. Wet scrubbers (caustic or sodium hypochlorite) handle smaller plants or retrofit where thermal oxidation is impractical.

The mix tower and bitumen tank LEV scope on a single new Australian asphalt plant typically runs 200-600 m of 316L spiral duct, 30-80 hood capture points, one thermal oxidiser and a complete control and balance package. This is substantial 316L stainless fabrication work for the SBAL-V auto duct line configured for stainless coil.

Bitumen storage tank Zone 1 hazardous area

Bitumen storage tank farms are the single most regulated hazardous area on an asphalt plant. Tanks hold 50,000-2,000,000 L of bitumen at 150-180°C continuously. The headspace above the heated bitumen is a vapour-air mixture at varying composition — typically below the lower flammable limit (LFL) at the bulk of the headspace but transitioning above the LFL during fill/empty cycles when fresh air is drawn into the tank. Heated bitumen vapour ignition is the primary fire risk at every bitumen depot on Earth, and it is the engineering driver behind every line of the AS 1940 flammable liquid storage code and the AS/NZS 60079.10.1 hazardous area classification standard.

The classification zone runs as follows under AS/NZS 60079.10.1 and the AS 1940 supplementary guidance. Zone 0 inside the tank headspace itself (vapour continuously present). Zone 1 within 4.5 m of any tank breather vent, sample port, manhole or pump seal where vapour is intermittently present during normal operation. Zone 2 in the bund and pump farm extending 7.5-15 m beyond the tank where vapour is present only during abnormal conditions. Beyond Zone 2, unclassified. The exact zone radii depend on tank size, vent stack height and flame arrester rating — every plant runs its own hazardous area dossier signed off by a competent person under AS/NZS 60079.

All electrical equipment within the hazardous area — ventilation fan motors, level transmitters, sample valve solenoids, light fittings, junction boxes, instrument cabinets — must be Ex-rated to the appropriate equipment protection level (EPL Ga for Zone 0, EPL Gb for Zone 1, EPL Gc for Zone 2). Certification through the IECEx scheme or by ANZEx. Ex-d (flameproof), Ex-e (increased safety), Ex-i (intrinsic safety) and Ex-n (non-incendive) are all common in tank farm equipment. Cable glands at every electrical entry are Ex-certified and torqued to manufacturer specification.

Tank breather vents are equipped with ISO 16852 flame arresters and knock-out pots. Flame arresters prevent external flame propagation back into the tank if the breather discharge ignites. Knock-out pots condense bitumen aerosol back to liquid for return to the tank. Vent stacks rise 6-12 m above the tank top to discharge above operator breathing zone and to allow buoyant dispersion of any flammable vapour. Vent piping is welded carbon steel insulated and heat-traced (typically 6-12 mm wall thickness, 80-150 mm diameter for medium-size tanks, larger for the major Viva Energy Geelong tanks).

Tank shell heating is by hot oil coil (250-300°C oil), electric immersion heater (in smaller tanks), or steam coil (where steam is available from a co-located boiler). Hot oil systems run their own AS 4041 pressure piping code dossier. Heat tracing on bitumen piping runs at 180-220°C surface temperature with redundant temperature monitoring — overheating causes bitumen thermal cracking and accelerates H2S evolution from sour-crude-derived bitumen.

H2S (hydrogen sulfide) is a significant secondary hazard at sour-crude bitumen tanks. WES is 10 ppm TWA, 15 ppm STEL. H2S evolves from bitumen heated above 180°C and accumulates in the headspace. Continuous H2S monitoring inside the tank vent stack or at the manhole sample port is standard practice. Operators carrying portable H2S monitors with 10 ppm alarm thresholds are required for any manhole entry or sample port operation. The Viva Energy Geelong Shell Bitumen operation, the SAMI Bitumen Technologies plants and the historical BP Bitumen tank farms all run H2S detection at every manhole.

SBKJ machinery on a bitumen tank farm project is concentrated on the LEV duct from the manhole and sample port hoods back to the central scrubber or condenser. 316L stainless 1.5 mm round spiral 200-400 mm diameter, fabricated on the SBFB-1500 spiral former. Rectangular LEV trunk in 316L on the SBAL-V configured for stainless coil. SBPC1500 plasma cutting station handles the flange cut-outs for connection to the welded vent stack. All duct supports, hangers and bolting are Ex-rated and antistatic-bonded to the earthing grid.

Hot mix asphalt aggregate dryer exhaust

The aggregate dryer drum is the largest single piece of equipment on a hot mix asphalt plant and the largest source of high-temperature exhaust gas. Parallel-flow drums (gas and aggregate moving in the same direction) operate with peak gas temperatures of 1,200-1,400°C at the burner end, exiting at 120-180°C after heat transfer to aggregate. Counter-flow drums (gas opposing aggregate) operate with cooler exhaust 180-300°C but require more sophisticated dust handling because hot dust exits at the cold end. Drum diameter 2.0-3.6 m, length 8-12 m, rotation speed 6-12 rpm. Burner thermal input 15-30 MW for an 80-500 t/h drum.

Fuel options run LPG, natural gas, heavy fuel oil (legacy) or recycled used oil (small operators). LPG and natural gas are the dominant choices on new Australian plants because they minimise CO and NOx emissions and avoid the heavy fuel oil sulphur penalty. Burner skid is Zone 1 hazardous area under AS/NZS 60079.10.1 for the LPG/natural gas supply line. Burner combustion air supply duct is straightforward atmospheric intake with insect screen and acoustic attenuation.

Aggregate dryer exhaust gas at the drum outlet carries silica RCS, basalt and limestone fines at 50-200 g/Nm³, plus CO (30 ppm STEL — typically below this in steady operation but rising during burner transients), NOx (typically 100-300 mg/Nm³ at the burner exhaust), CO2, water vapour and trace VOCs if RAP is introduced. Dryer exhaust ducting between the drum and the primary cyclone is welded heavy fabrication: 4-6 mm carbon steel for the parallel-flow drum exhaust at 120-180°C, stepping up to 309S or 310S stainless near the burner end if surface temperature exceeds 300°C continuously. Duct internal diameter 1.0-1.8 m typical for 80-500 t/h plant capacity.

The primary cyclone (or set of cyclones in parallel) drops out the coarse dust fraction at 80-95% collection efficiency. Cyclone outlet duct to the secondary baghouse runs at 110-140°C and carries the residual fines. Cyclone return — collected dust dropped into a screw conveyor and returned to the asphalt mix as filler — is standard practice. Cyclone construction is welded heavy fabrication.

The secondary baghouse uses pulse-jet bag filters with PTFE-membrane or aramid (Nomex) bags depending on operating temperature. Aramid is used at sustained operating temperatures of 180-200°C; PTFE handles up to 250°C continuous. Filter air-to-cloth ratio 1.0-1.5 m³/m²/min for aggregate dust. A 200 t/h plant baghouse runs 1,500-2,500 filter bags in 4-8 compartments. Baghouse outlet stack discharges to atmosphere at less than 30 mg/Nm³ total dust per state EPA licence conditions.

NFPA 86 (industrial oven design) governs the burner and drum dryer combustion system. NFPA 86 requires safe shutdown logic, flame supervision, oxygen monitoring, pre-purge and post-purge cycles, low-pressure cut-out on the gas supply, high-temperature cut-out on the drum exhaust, and explosion venting on the drum body. The dust collector (cyclone and baghouse) downstream of the drum is subject to NFPA 660 dust hazard analysis where RAP, crumb rubber or other combustible constituents are present in the dust load.

Heat recovery from dryer exhaust is increasingly common on new plants to pre-heat the RAP feed or to generate process steam. Heat recovery duct between the cyclone outlet and the heat exchanger is welded carbon steel insulated. Heat exchanger outlet duct to baghouse is the same. None of this is SBKJ sheet-metal scope.

Polymer-modified bitumen and crumb rubber blending

Polymer-modified bitumen (PMB) production blends elastomeric or plastomeric polymer modifiers into heated bitumen to improve pavement performance — rutting resistance, fatigue life, low-temperature flexibility, ageing resistance, adhesion. The major polymer types used in Australia are SBR (styrene-butadiene rubber, the dominant modifier supplied by SAMI Bitumen Technologies as Stylink or Spread brand), SBS (styrene-butadiene-styrene block copolymer, used in premium PMB grades), EVA (ethylene-vinyl acetate, used in airport runway and heavy-duty pavements), EPDM (ethylene propylene diene monomer, often as crumb rubber form), and crumb rubber from recycled tyres (Tyrecycle, GDT, ECOFlex, BIA).

PMB blending vessels operate at 170-190°C with high-shear mixing for 1-4 hours to dissolve the polymer fully into the bitumen. Polymer addition is via top-loading manhole hopper (master batch) or continuous side-stream injection. Shear stages use rotor-stator high-shear mills running at 3,000-10,000 rpm to disperse polymer particles to colloidal size. Ageing tanks hold the blended PMB at 160-180°C for 12-48 hours to allow polymer-bitumen interaction to stabilise. Final QC testing uses the Polyhose test (AS 1141.5, AS 1141.6) and PMB specification per AS 3568.

The PMB blending vessel headspace is classified Zone 1 hazardous area under AS/NZS 60079.10.1, with the zone extending 3 m from any vent, sample port or top manhole. The hazard is composite: heated bitumen vapour (LFL-flammable at fill cycles), styrene off-gas from SBR/SBS addition (WES 50 ppm STEL — flammable LFL 1.1%), butadiene off-gas (WES 1 ppm STEL — IARC Group 1 carcinogen, LFL 2.0%), EVA vinyl acetate off-gas, EPDM propylene/diene off-gas, and crumb rubber thermal degradation gases at high blending temperatures.

Local exhaust ventilation at every PMB addition point, vessel manhole, sample port and shear stage is mandatory. LEV duct is 316L stainless 1.5 mm because polymer condensate is sticky and the duct sees periodic CIP (clean-in-place) hot solvent flushing. Capture velocity 0.7-1.0 m/s at the hood face. Capture flow 2,000-4,000 m³/h per addition point. SBKJ SBAL-V configured for stainless coil handles the rectangular LEV trunk; SBFB-1500 spiral former handles round trunk to 800 mm diameter.

PMB vessel vent stack discharge runs through a flame arrester to a thermal oxidiser or scrubber, not to atmosphere. Direct atmospheric discharge would release styrene, butadiene, vinyl acetate and bitumen aerosol at unacceptable concentrations. The thermal oxidiser is the same RTO unit as the mix tower bitumen fume oxidiser on integrated PMB-plus-HMA sites.

Crumb rubber pre-feed handling adds NFPA 660 combustible dust controls on top of the AS/NZS 60079 hazardous area zoning. Crumb rubber (0.6-2 mm particle size) is mechanically conveyed from the receiving silo through a vibratory feeder, weigh hopper and slurry-spray injector into the PMB vessel. Crumb rubber dust at the receiving silo top filter, the weigh hopper top vent and the vibratory feeder cover is combustible with measurable KSt values. Grounding and bonding on every conveyor and silo. Isolation valves between the rubber feed system and the PMB vessel to prevent flame propagation. Deflagration vents on the receiving silo top. NFPA 68 and NFPA 69 design practice applies.

Pyrolysis crumb rubber producers (Green Distillation Technologies GDT) run a different process — thermal decomposition of whole tyres at 400-600°C in inert (nitrogen) atmosphere, producing syngas (hydrogen at LEL 4%, CO at 12.5% LEL, methane at 5% LEL), bio-oil, carbon black and recovered steel cord. Pyrolysis reactor seals are classified Zone 1 because syngas leakage is unavoidable during normal operation. Carbon black handling downstream of the pyrolysis reactor runs NFPA 660 combustible dust with deflagration vents, isolation valves and inerting per NFPA 68/69. Pyrolysis kiln seal vent discharges to a flare or thermal oxidiser, not to atmosphere — direct discharge would release CO at lethal concentrations.

Asphalt plant control room and laboratory HVAC

The asphalt plant control room is the operational nerve centre. A typical batch plant or drum mix plant control room is a small purpose-built building (4-8 m x 6-10 m floor area) housing 2-4 operator workstations facing windows that look out over the mix tower and aggregate cold feed. Computer screens display the batch programme, aggregate weigh data, bitumen flow rate, mix tower temperature and silo level. The Plant Operator runs 8-12 hour shifts producing 80-500 t/h of HMA on demand from delivery trucks queueing at the load-out hatch.

Control room HVAC design intent is positive pressure (+25 to +50 Pa relative to the surrounding plant), two-stage particulate intake filtration (G4 prefilter ISO 16890 ePM10 ≥50% plus F7 or F9 final filter ISO 16890 ePM2.5 ≥85%), thermal comfort 22-24°C dry bulb at 50-60% RH, and acoustic comfort below 50 dBA RMS at the operator workstation. Hermetic sealing of the building envelope — gasketed doors, sealed cable penetrations, double-glazed windows with EPDM gaskets — keeps aggregate dust and bitumen fume out of the room.

The HVAC supply duct serving the control room is conventional rectangular galvanised duct in 0.7-1.0 mm wall thickness fabricated on the SBAL-V auto duct line to AS/NZS 4254-1 low-pressure construction tolerances. TDF/TDC flange joints sealed with neoprene gasket and silicone bead. Trunk supply from the rooftop AHU into the control room in spiral round duct on the SBTF-1500/1602/2020 at 200-500 mm diameter.

The asphalt laboratory adjacent to the control room runs Marshall stability and flow testing, Hveem testing, Superpave SHRP testing, wheel tracking, rutting, stripping, adhesion, density and voids analysis, plus aggregate testing under AS 1141, AS 2150, AS 3568 and AS 2008. Sample preparation involves heating bitumen samples to 150-180°C in the fume cupboard, which generates bitumen fume with benzo[a]pyrene loading. The fume cupboard exhaust is the highest-priority LEV circuit in the lab.

Laboratory fume cupboard construction follows AS/NZS 2982. Sash face velocity 0.5 m/s ± 10% across the full sash opening. Duct material 316L stainless 0.8-1.0 mm because bitumen condensate accumulates on the duct internal surface. Fume cupboard exhaust fan is dedicated (one fan per cupboard, not shared) to allow individual lab shutdown during fan maintenance. Discharge to roof level with downstream HEPA filtration if benzo[a]pyrene loading is significant.

Lab building HVAC supply is conventional galvanised duct on the SBAL-V plus SBTF. Lab analytical instrument exhausts (gas chromatograph, spectrophotometer, ash oven, Marshall water bath) are separated from the fume cupboard exhaust to avoid cross-contamination and to allow individual instrument exhaust monitoring.

AS 1668.2 outdoor air rates apply: 10 L/s/person minimum for offices, 12 L/s/person for control rooms with display screen work, 25 L/s/person for laboratory analytical benches. Air balance verification at commissioning measures supply flow, return flow, exhaust flow, room pressure differential to surrounding plant, and capture velocity at each LEV hood.

Bitumen refinery — Viva Energy Geelong

The Viva Energy Geelong Refinery (ASX:VEA) is the single largest bitumen production site in Australia and the only remaining major paving bitumen refinery on the east coast. Geelong operates under the Shell Bitumen licensing arrangement, producing paving bitumen, industrial bitumen, marine bitumen, heavy fuel oil, jet fuel, aviation gasoline and a full slate of refined products. The refinery sits on Corio Bay just outside Geelong VIC and is integrated with bulk distribution terminals serving the Australian east coast.

Bitumen production at Geelong runs through a vacuum distillation unit (VDU) and a propane deasphalting unit (PDA). VDU bottom-side bitumen is the soft paving grade; PDA-recovered asphaltenes are blended into the harder industrial and roofing grades. Finished bitumen is heated to 150-180°C and pumped to one of multiple atmospheric storage tanks on the refinery's tank farm.

HVAC duct demand at Geelong is dominated by comfort HVAC in the operator control rooms (large central control building plus distributed local control points), the maintenance workshop, the laboratory and the administration buildings. Process LEV at the tank manholes, sample ports and pump seals is significant on a refinery of this scale — 30-100 LEV capture points per tank farm depending on tank count.

Material specification on Geelong refinery LEV duct is 316L stainless 1.5 mm for the heated bitumen LEV circuit, 304 stainless for the lower-temperature jet fuel and avgas LEV circuits, and galvanised G275 for the comfort HVAC scope. All electrical equipment within the hazardous area is Ex-rated and certified under IECEx with refinery-specific competency assurance per the AS/NZS 60079 series.

Ampol's Lytton Refinery in Brisbane is in the process of closing for biofuel transition under the Ampol Future Energy programme. Bitumen production at Lytton is being phased out; remaining demand is supplied via Geelong and bulk import. The BP Kwinana Refinery in WA closed in 2021 — Kwinana bitumen production has been replaced by bulk import to Fremantle and direct supply from Geelong.

The contraction of domestic refining capacity has shifted bitumen supply security toward bulk import via Port Kembla, Newcastle, Brisbane and Fremantle terminals. Import terminal tank farms have the same Zone 1 / Zone 2 hazardous area zoning, the same AS 1940 storage compliance and the same LEV requirements as a refinery tank farm. SAMI Bitumen Technologies, Puma Bitumen and various Boral, Hanson and Downer terminal operations all run substantial import-receiving tank farms.

Workplace exposure standards — the full WES inventory

Safe Work Australia maintains the Workplace Exposure Standards (WES) for the chemical agents present on an asphalt plant. The headline numbers are the same across NSW, VIC, QLD, WA, SA, TAS, ACT and NT under the harmonised WHS framework. Critical WES values for asphalt plant engineering controls are as follows.

• Benzo[a]pyrene (BaP): 0.05 mg/m³ TWA. IARC Group 1 confirmed human carcinogen. The killer hazard for asphalt workers. Present in heated bitumen fume, asphalt paving fume, milling fume and laboratory bitumen sample preparation.
• Bitumen aerosol mist (inhalable): 0.5 mg/m³ TWA, 5 mg/m³ STEL. Bitumen aerosol carries the BaP and PAH content, so controlling the aerosol controls the BaP exposure.
• Polycyclic aromatic hydrocarbons (PAH) total: assessed as benzene-soluble fraction at the BaP limit, with the IARC PAH inventory including naphthalene, anthracene, pyrene, benzo[a]pyrene, benzo[k]fluoranthene and others.
• Respirable crystalline silica (RCS): 0.05 mg/m³ TWA. The killer hazard for aggregate workers. From quartz sand, basalt fines, limestone, dolomite, blue metal. Silicosis epidemic driver behind the Engineered Stone Ban of 2024.
• Respirable particulate (general): 5 mg/m³ TWA where no more stringent specific limit applies.
• Inhalable particulate (general): 10 mg/m³ TWA.
• Carbon monoxide (CO): 30 ppm STEL, typically 25-30 ppm TWA per harmonised state regulation. Source: LPG burner on the dryer, natural gas burner on the dryer, diesel exhaust from on-site mobile equipment, aggregate dryer incomplete combustion.
• Carbon dioxide (CO2): 5,000 ppm TWA. Source: combustion gases plus ambient.
• Methane (CH4): 1.25% LEL alarm threshold (10% of LEL). Source: natural gas burner supply line, heated bitumen low-MW hydrocarbon evolution.
• Hydrogen sulfide (H2S): 10 ppm TWA, 15 ppm STEL. Source: sour-crude-derived bitumen, aged bitumen, rejuvenator chemistry, refinery legacy.
• Styrene: 50 ppm STEL, 50 ppm TWA. Source: SBR and SBS polymer modifier addition at PMB blending vessels.
• 1,3-Butadiene: 1 ppm STEL. IARC Group 1 carcinogen — extremely low limit. Source: SBR and SBS polymer modifier addition, EPDM elastomer addition.
• Ammonia (NH3): 25 ppm TWA. Source: rare on asphalt plants — only relevant if SCR NOx control is installed on the dryer exhaust (uncommon on current Australian plants).
• Manganese (Mn): 0.2 mg/m³ TWA. Source: steel welding during plant maintenance.
• Lead (Pb): 0.05 mg/m³ TWA. Source: legacy tetraethyl lead from pre-1986 leaded petrol contamination on aged paving, leaded brass fittings, avgas 100LL legacy aviation contamination at airport pavement reseals.
• Chromium VI (Cr VI): 0.05 mg/m³ TWA. Source: stainless and chassis welding fumes.
• Nickel (Ni): 0.1 mg/m³ TWA. Source: stainless welding fumes.
• Hydrogen fluoride (HF): 1.8 mg/m³ STEL. Source: aluminium pre-paint etching (rare on asphalt plants, more common on adjacent maintenance workshops).
• Hydrochloric acid (HCl): 5 mg/m³ STEL. Source: rare.
• VOC general: assessed against individual species limits. Source: bitumen aromatic content, heated bitumen vapour, thinner, adhesive and paint use in the maintenance workshop.
• R32, R454B, R744 refrigerants: typically only relevant to office and control room HVAC condenser refrigerant inventories under AS/NZS 5149 (refrigeration safety) and AS/NZS 1677.

The asphalt plant engineering controls hierarchy applies WES values in the following sequence: elimination (substitute lower-emission bitumen grade, lower-PAH binder, low-styrene PMB modifier), substitution, engineering controls (LEV, baghouse, enclosure, capture-at-source), administrative controls (residence time limits, job rotation, signage), and PPE (AS 1715 respiratory protection) only as the final layer. Engineering controls do the bulk of the WES compliance heavy lifting.

Standards inventory — AS, NFPA, NCC and AAPA

Australian asphalt plant HVAC design draws on a long list of Standards and regulatory references. The complete inventory routinely referenced on a new plant build or a major shutdown follows.

• AS 1668.1 — fire and smoke control via mechanical air handling systems.
• AS 1668.2 — mechanical ventilation in buildings (outdoor air rates, exhaust rates).
• AS/NZS 4254.1 — ductwork for air-handling systems in buildings, low and medium pressure.
• AS/NZS 4254.2 — ductwork for air-handling systems in buildings, high pressure (spiral and rectangular).
• AS 1530.4 — fire-resistance test of building elements (fire-rated ductwork).
• AS 1657 — fixed platforms, walkways, stairways and ladders (access on tank farms and mix towers).
• AS/NZS 60079 series — hazardous area equipment and installation. AS/NZS 60079.10.1 hazardous area classification for gases. AS/NZS 60079.14 design and selection. The single most critical standard family on a bitumen tank farm or PMB plant.
• AS 1940 — storage and handling of flammable and combustible liquids. Bitumen, diesel, LPG, fuel tank, silo construction and bunding.
• AS 3957 — dust hazard identification and control (combustible and silica dust). Aggregate stockpile, hopper, feeder, conveyor, bucket elevator, silo, transfer points.
• AS 1715 — selection, use and maintenance of respiratory protective equipment. P2, P3, PAPR.
• AS/NZS 2982 — laboratory fume cupboards. Sash face velocity, exhaust duct construction.
• AS 4041 — pressure piping (hot oil heating systems).
• AS 4332 — anhydrous ammonia handling (rare on asphalt plants — only SCR retrofit).
• AS/NZS 1554.1 — structural steel welding.
• AS/NZS 1554.6 — stainless steel welding.
• AS 1885 — workplace welding fume exposure measurement.
• AS/NZS 5149 and AS/NZS 1677 — refrigeration safety (office and control room HVAC condenser refrigerant inventories).
• AS 1141 series — aggregate testing (sieving, density, AVI, AS 1141.5, AS 1141.6 etc.).
• AS 2150 — chip seal and spray seal practice.
• AS 3568 — bituminous emulsions and PMB specification.
• AS/NZS 4198 — bitumen emulsion specification.
• AS 2008, AS/NZS 2008.1 — bitumen specification and testing.
• AS 2891 — sampling and testing of asphalt mixes (Marshall, density, voids).
• NCC Class 8 industrial buildings, NCC Class 7b storage buildings, NCC Class 5 office/lab. National Construction Code building classification.
• NFPA 660 (2025) — Standard for Combustible Dust (consolidated, replacing NFPA 652, 654, 484, 61, 664, 655).
• NFPA 68 — Standard on Explosion Protection by Deflagration Venting.
• NFPA 69 — Standard on Explosion Prevention Systems (inerting, suppression, isolation).
• NFPA 86 — Standard for Ovens and Furnaces (industrial oven — drum dryer, aggregate dryer, batch oven, heated bitumen 130-180°C).
• NFPA 30 — Flammable and Combustible Liquids Code (bitumen, diesel).
• NFPA 13 — Standard for the Installation of Sprinkler Systems.
• NFPA 70 — National Electrical Code (US benchmark cross-referenced for IECEx hazardous area equipment).
• ASHRAE 90.1 and NCC Section J — energy efficiency in commercial buildings.
• AAPA — Australian Asphalt Pavement Association design guidelines and AS 2891 testing practice cross-references.
• Austroads AGPT — Austroads Guide to Pavement Technology (AGPT01 to AGPT14 series). APRG Austroads Pavement Research Group reports. TS-02 Test Specifications.
• State road authority specifications — NSW RMS, VicRoads, QLD TMR, Main Roads WA, DPTI SA, TasRoads, Roads ACT, NTG Transport.
• IRF — International Road Federation cross-references.

The HVAC contractor pricing an asphalt plant project routinely references AS 1668.2 for outdoor air rates, AS/NZS 4254.1 for rectangular duct construction tolerances, AS/NZS 60079.10.1 for hazardous area zoning around the bitumen tank farm, AS 3957 for aggregate dust capture velocity, and AAPA design guidelines for industry-standard practice. The fabrication contractor sub-contracting heavy welded duct sections references the AS/NZS 1554 welding series, NFPA 86 for the drum burner and NFPA 660 for the dust collector design.

Process exhaust ductwork — what sits outside SBKJ scope

The boundary between sheet-metal HVAC fabrication on SBKJ machinery and welded heavy fabrication on submerged-arc and FCAW process duct equipment is sharp and well-defined on an asphalt plant. Welded heavy fabrication scope covers:

• Aggregate dryer drum body — 8-15 mm wall mild steel cylindrical shell with refractory lining at the burner end. Welded by specialist drum manufacturers (Astec, Marini, Ammann, Lintec).
• Drum dryer exhaust duct from drum outlet to primary cyclone. 4-6 mm carbon steel for the parallel-flow drum exhaust at 120-180°C, 309S or 310S stainless if surface temperature exceeds 300°C. Abrasion liners (chromium carbide overlay, basalt) at bends. Welded by submerged-arc welding for longitudinal seams.
• Primary cyclone — welded heavy fabrication with internal cone in 8-12 mm carbon steel.
• Cyclone to baghouse inlet duct — 4-5 mm carbon steel at 110-140°C with abrasion liners.
• Baghouse compartments and outlet duct — 3-5 mm carbon steel, sometimes 304 stainless near the stack.
• Stack — 3-5 mm carbon steel cylindrical chimney with 316L stainless lining in the upper third for acid dewpoint margin. Stack height 25-40 m typical for an asphalt plant, set by EPA dispersion modelling.
• Bitumen tank shell — atmospheric vertical insulated tank in 5-10 mm carbon steel, welded by API 650 procedure.
• Bitumen tank breather vent stack with ISO 16852 flame arrester and knock-out pot.
• PMB vessel — 12-25 mm carbon steel or 316L stainless pressure-rated vessel with internal shear mixer and ageing tank.
• PMB vessel vent stack to thermal oxidiser or scrubber.
• Pyrolysis kiln (GDT) — 15-30 mm carbon steel pressure-rated reactor with internal seals to maintain inert atmosphere.
• Heated bitumen process piping — 6-12 mm carbon steel pipe insulated and heat-traced, welded to AS 4041 pressure piping code.
• Thermal oxidiser and RTO — 12-25 mm carbon steel with ceramic refractory lining at the combustion chamber.

SBKJ standard duct machinery — the SBAL-V auto duct line, SBFB-1500 spiral former, SBTF-1500/1602/2020 spiral tubeformer, SBAL-III, SBSF-1525 sheet flange, SB-ZF1500 sheet folding, SBLR-600 lockformer, and SBPC1500 plasma cutter — does not address the heavy-gauge welded fabrication scope listed above. That fabrication runs through submerged-arc welding shops with plate-rolling, pressure-vessel and refractory lining capability. SBKJ Australia routinely refers customers needing heavy fabrication to specialist welded-fabrication suppliers across the Australian and Southeast Asian heavy-fabrication market.

Boral, Hanson, Downer, Fulton Hogan — the maintenance contractor market

The largest single market segment for HVAC duct fabrication in Australian asphalt is the maintenance contractor backlog at the four major listed operators — Boral, Hanson, Downer EDI Road Services and Fulton Hogan. Each operator runs a network of 80-100+ asphalt plants nationally with rolling refurbishment programmes spread across the asset base.

The typical asphalt plant in this network is 15-30 years old, originally commissioned with limited LEV capture beyond the central baghouse, and progressively upgraded as WES limits have tightened, EPA licence conditions have stiffened and AAPA design practice has evolved. The 2024 Engineered Stone Ban and the alignment of state silica regulators at the 0.05 mg/m³ RCS limit have pushed every operator to revisit their aggregate cold feed LEV and to add capture-at-source at every dust transfer point. The continued tightening of benzo[a]pyrene exposure assessment, the formal recognition of asphalt fume as IARC Group 2A (probable human carcinogen) and the increasing use of PMB and crumb rubber on premium pavement contracts have all driven LEV upgrades at the mix tower paddle deck and the PMB blending vessel.

The shutdown rhythm on a single plant typically runs 1-2 weeks once per year during the winter trough in road construction demand (April-July across most of southern Australia). LEV duct upgrades, baghouse compartment replacement, dryer drum re-shelling and bitumen tank inspection all happen within this window. HVAC contractors compete for shutdown duct fabrication on price, quality, schedule and proximity to the site. Local fabrication capability — Box Hill North VIC for Melbourne plants, similar regional hubs in NSW, QLD, WA, SA, TAS — is the deciding factor on most awards.

The fabrication contractor that runs an SBKJ SBAL-V auto duct line plus an SBFB-1500 spiral former plus an SBPC1500 plasma cutter has the throughput and the flexibility to win shutdown packages across all four operators. Switching between galvanised sheet for comfort HVAC and 316L stainless for bitumen LEV happens on the same SBAL-V machine in a single shift. Stainless changeover takes 30-60 minutes of cleaning and tool offset adjustment. Single-shift fabrication output handles 8,000-15,000 m² per month of mixed duct across multiple grades and gauges.

SAMI Bitumen, Puma, Shell and the PMB plant market

The polymer-modified bitumen plant market in Australia is concentrated at three major suppliers — SAMI Bitumen Technologies (the volume leader), Puma Bitumen and Shell Bitumen (produced under licence at the Viva Energy Geelong Refinery). Each operator runs PMB blending plants in the major capital cities producing SBR, SBS, EVA, EPDM and crumb rubber polymer blends to AS 3568 specifications.

SAMI Bitumen Technologies operates PMB plants in Sydney, Melbourne, Brisbane, Perth and Adelaide. Plant scale varies from 5,000 to 50,000 tonnes per annum of finished PMB. Each plant runs 2-4 blending vessels, master batch hopper, continuous mixer skid, shear stage, ageing tank, finished PMB storage tanks and truck load-out. LEV capture at every blending vessel addition point, manhole, sample port and shear stage is mandatory under WES compliance.

Puma Bitumen operates a similar national network at smaller capacity. The Shell Bitumen production at Viva Energy Geelong feeds bulk PMB into east coast markets via the integrated terminal network.

HVAC duct demand at a PMB plant is dominated by 316L stainless LEV from each blending vessel and shear stage hood up to the central thermal oxidiser. A typical PMB plant runs 100-300 m of 316L spiral duct at 200-600 mm diameter, plus rectangular trunk in 316L at 600-1,200 mm width. SBKJ SBAL-V auto duct line configured for stainless coil and SBFB-1500 spiral former configured for stainless handle the full fabrication scope.

PMB plant LEV is typically retrofitted in stages over multi-year programmes — capture-at-source on the addition hopper first, then on the manhole top, then on the sample port and shear stage. Each retrofit is a 100-200 m duct package taking 3-6 weeks of fabrication time. The fabrication contractor that builds long-term relationships with SAMI, Puma and Viva Energy maintenance teams secures the rolling backlog.

Tyrecycle, GDT, ECOFlex and the crumb rubber market

Crumb rubber asphalt production has grown rapidly in Australia under the Tyre Stewardship Australia (TSA) framework and state road authority sustainable pavement programmes. The major crumb rubber producers are Tyrecycle (now Veolia), Green Distillation Technologies (GDT pyrolysis), ECOFlex Crumb Rubber Pty Ltd and Bitumen Industries Australia (BIA). The historical Devine Tyrecycle plant in NSW closed several years ago.

Mechanical crumb plants (Tyrecycle, ECOFlex) grind whole tyres or shredded tyre chips to 0.6-2 mm crumb under aspiration. Steel tyre cord is separated by magnetic and density separators. Polyester and nylon fibre is separated by air classification. Finished crumb is screened, packaged and shipped to PMB producers or to asphalt plants for direct addition.

Pyrolysis crumb plants (Green Distillation Technologies GDT) thermally decompose whole tyres at 400-600°C in inert nitrogen atmosphere. Decomposition products are syngas (hydrogen at LFL 4%, CO at 12.5% LEL, methane at 5% LEL), bio-oil, recovered carbon black (rCB) and steel cord. Pyrolysis is a more capital-intensive process than mechanical crumb but generates higher-value carbon black recovery alongside the rubber regrind product.

HVAC duct demand at a mechanical crumb plant is dominated by NFPA 660 combustible dust LEV at the shredder, the grinder, the screening deck, the magnetic separator and the bagging station. Trunk duct in mild steel 1.5 mm with antistatic earthing. SBKJ SBFB-1500 spiral former handles the round spiral 300-800 mm diameter trunk runs. Grounding and bonding to the plant earth grid via braided copper strap at every joint.

HVAC duct demand at a pyrolysis crumb plant is more demanding. Pyrolysis reactor seal vents discharge to a flare or thermal oxidiser via welded carbon steel piping (welded heavy fabrication scope). Carbon black handling downstream of the pyrolysis reactor runs NFPA 660 combustible dust controls with deflagration vents on the silo top, isolation valves between the reactor and the silo, and inerting with nitrogen. LEV at the carbon black bagging station is in mild steel with full antistatic earthing. The SBKJ machinery fits the carbon black LEV trunk runs — 316L stainless on high-temperature sections, mild steel elsewhere.

Bitumen Industries Australia (BIA) operates as both a crumb rubber producer and a downstream PMB blender, combining crumb production and PMB blending on the same site. The duct fabrication scope on a BIA site combines NFPA 660 dust LEV plus AS/NZS 60079 Zone 1 PMB vessel LEV, in a single integrated facility.

SBKJ machinery for asphalt plant HVAC contractors

For HVAC contractors working on Australian asphalt plant comfort HVAC, LEV and process LEV scope, SBKJ recommends a five-machine fabrication line built around the SBAL-V auto duct line as the central spine.

SBAL-V Auto Duct Production Line. The SBAL-V is the workhorse for rectangular galvanised and 316L stainless duct fabrication on asphalt plant control room, lab, workshop, amenities, PMB LEV and bitumen LEV scope. Coil-to-finished-duct in a single integrated line: decoiler, levelling rolls, notching station, beading, TDF flange forming, longitudinal seam locking and cut-off. Single-shift output 10,000-15,000 m² per month for a typical SBAL-V configuration. Capability to fabricate in galvanised G275/G300 0.6-1.5 mm or 316L stainless 1.0-1.5 mm or 309S/310S stainless for the higher-temperature LEV reaches. Material changeover 30-60 minutes including tool offset adjustment and machine cleaning. See the auto duct lines category for full machine specifications.

SBAL-III Auto Duct Production Line. The SBAL-III is a higher-throughput configuration of the auto duct line — extended for production runs above 18,000 m²/month. Same construction logic as SBAL-V with larger coil capacity, higher-speed notching and integrated flange forming. SBAL-III is the right choice for contractors holding three to five concurrent plant shutdown packages in a single month.

SBSF-1525 Sheet Flange Machine. The SBSF-1525 produces TDF/TDC sheet metal flange profiles in a single integrated rolling-and-cutting station, sized for sheet width up to 1,525 mm and gauge 0.6-1.5 mm. Flange forming is the most common stand-alone retrofit accessory in HVAC workshops. SBSF-1525 handles full asphalt plant comfort HVAC scope plus 316L stainless LEV flange production for the bitumen mix tower and PMB vessel LEV.

SB-ZF1500 Sheet Folding Machine. The SB-ZF1500 is a programmable sheet folding machine for rectangular duct sections, sized for sheet width up to 1,500 mm. Folds in galvanised G275 0.6-1.5 mm or 316L stainless. The SB-ZF1500 complements the SBAL-V on shorter production runs or one-off custom sections where the auto line throughput is overkill.

SBFB-1500 Round Duct Spiral Former. The SBFB-1500 fabricates round spiral duct from coil at 200-1,500 mm diameter, 0.6-1.5 mm wall thickness. Aggregate cold feed LEV at the silica RCS transfer points, bitumen tank LEV at the manhole sample ports, PMB vessel LEV trunk and crumb rubber LEV trunk all run round spiral on the SBFB-1500. Material options include galvanised, 316L stainless, 304 stainless and mild steel for antistatic earthed combustible dust applications. NFPA 660-compliant earthing at every joint.

SBPC1500 Manual and Plasma Cutting Station. The SBPC1500 cuts heavy plate 6-25 mm mild steel and 6-20 mm stainless. Used for aggregate dryer exhaust duct flange cut-outs, bitumen tank manhole vent stack take-offs, PMB vessel branch flanges and stack take-offs. Programmable nesting handles complex multi-piece cuts. SBPC1500 plate cutting feeds into field welding by the heavy fabrication contractor; SBKJ machinery scope ends at the cut plate ready for hand-off.

SBLR-600 Pittsburgh Lockformer. The SBLR-600 produces Pittsburgh longitudinal seams for rectangular duct, handling galvanised G275 sheet up to 1.5 mm gauge. Used as a stand-alone seam former on shorter production runs where the SBAL-V line is fully utilised on a different package.

SBTF-1500/1602/2020 Spiral Tubeformer. The SBTF series fabricates round galvanised and stainless trunk duct at higher throughput than the SBFB-1500 — typical SBTF-2020 output 1,200-1,800 m per shift at 1,500 mm diameter. SBTF spiral duct is preferred for the central trunk supply runs from the rooftop AHU into the control room and lab, plus on the central thermal oxidiser intake trunk where high flow rates demand large-diameter rigid round duct. See the spiral tubeformer category for machine selection guidance.

The five-machine line configured for a major Australian asphalt plant HVAC contractor typically runs around AUD 850,000-1,400,000 capital outlay, paid back across the rolling shutdown backlog at the Boral, Hanson, Downer and Fulton Hogan plant networks within 18-30 months. SBKJ Australia in Box Hill North VIC provides English-language pre-sales, commissioning, training and after-sales support across the configuration. Heavy welded fabrication on dryer exhaust duct, baghouse construction, stack work and bitumen tank shell fabrication remains outside the SBKJ standard machinery scope and sits with specialist welded-fabrication suppliers.

Construction phasing — shutdown-driven HVAC installation

Australian asphalt plants run continuously during the road construction season (typically September through April in southern Australia, year-round in QLD and WA) and shut down for refurbishment during the winter trough. The shutdown window varies from 1 week for minor refit to 4-6 weeks for major refurbishment or plant relocation. Comfort HVAC duct installation can mostly happen during normal operation — fabrication off-site, then installation by HVAC contractors during ordinary working hours without affecting production. LEV duct change-outs at the bitumen tank manhole, the PMB vessel and the mix tower paddle deck are shutdown-only because the equipment has to be cold and isolated.

HVAC contractors working around a shutdown coordinate closely with the plant maintenance superintendent and the EPC shutdown coordinator to avoid clashes with crane lifts, scaffold installation, refractory work and electrical isolation lockouts. Pre-shutdown fabrication off-site, modular delivery to site, crane lift on day one and tie-in on days two through five is the typical install sequence for a major LEV upgrade package.

The HVAC fabrication programme for a typical mid-sized asphalt plant LEV and comfort HVAC package (1,000-3,000 m² of duct across multiple buildings and capture points) runs 3-5 weeks of fabrication time and 2-4 weeks of installation time. Total programme from purchase order to handover is 8-14 weeks excluding design lead time. Design lead time on an asphalt plant project is typically 4-6 weeks for HVAC drawing approval through the operator's engineering review.

ARBS 2026 and the Australian asphalt-HVAC contractor network

ARBS 2026 — the Air Conditioning, Refrigeration and Building Services exhibition at the International Convention Centre Sydney in May 2026 — is the dominant Australian HVAC industry event of the year. SBKJ Group will be in attendance, with the SBAL-V auto duct line, SBFB-1500 spiral former and SBPC1500 plasma cutting station configurations on display. Heavy industrial HVAC contractors working on Boral, Hanson, Downer, Fulton Hogan, SAMI Bitumen Technologies, Puma Bitumen, Viva Energy Geelong, Tyrecycle, GDT, ECOFlex and Bitumen Industries Australia asphalt and bitumen plant projects are encouraged to attend.

The Australian Asphalt Pavement Association (AAPA) annual conference and the Austroads pavement technology symposium are the other two industry events where asphalt plant operators, HVAC contractors and equipment suppliers cross paths. AAPA design guidance and the Austroads AGPT framework remain the technical reference points for any HVAC contractor pricing or designing asphalt plant work.

FAQ

What duct materials are used for asphalt batch plant aggregate dryer exhaust?

Asphalt aggregate dryer exhaust between the drum dryer outlet and the primary cyclone runs at 120-180°C with high RCS silica and basalt dust loading. Heavy-gauge mild steel 4-6 mm wall thickness with abrasion liners at bends is the default. Higher temperature sections approaching the burner end of a counter-flow drum may run 200-300°C and step up to 309S or 310S stainless. Cyclone to baghouse inlet duct steps down to 3-5 mm carbon steel at 110-140°C. Baghouse outlet to stack runs cleaner at 90-110°C in 3-5 mm carbon steel. Bend outer walls are typically lined with chromium carbide overlay (Bisalloy, Hardox 450) or basalt insert because silica and basalt aggregate dust is extremely abrasive. None of this is SBKJ sheet-metal scope — it is welded heavy fabrication on the drier-to-baghouse run.

Why is benzo[a]pyrene the killer hazard in asphalt and bitumen HVAC design?

Benzo[a]pyrene is an IARC Group 1 confirmed human carcinogen present in heated bitumen fume and PAH emissions from asphalt mixing, paving and milling. The Safe Work Australia WES is 0.05 mg/m³ TWA — one of the lowest exposure standards on the asphalt plant, equal to the silica RCS limit. Bitumen aerosol mist limit is 0.5 mg/m³ TWA (5 mg/m³ STEL inhalable). LEV at every bitumen tank vent, mix paddle deck, truck load-out hatch, PMB blending vessel manhole and lab fume cupboard is mandatory. LEV duct in 316L stainless because heated bitumen condensate is sticky and corrosive — galvanised coating does not survive long-term bitumen aerosol exposure.

How is the bitumen storage tank farm classified under AS/NZS 60079?

Heated bitumen storage tanks at 150-180°C are classified Zone 1 hazardous area within 4.5 m of any tank breather vent, sample port, manhole or pump seal under AS/NZS 60079.10.1, because heated bitumen vapour ignites at the LFL when air mixes with the headspace vapour during fill/empty cycles. The bund and pump farm extending 7.5-15 m beyond the tank is typically Zone 2. Tank breather stacks are equipped with ISO 16852 flame arresters. All electrical equipment within the zone must be Ex-rated to EPL Ga, Gb or Gc and certified through the IECEx scheme or by ANZEx.

Which Australian asphalt and bitumen operators are the major HVAC duct buyers?

Boral Asphalt (ASX:BLD) — Australia's largest, 100+ plants nationwide. Hanson Asphalt (HeidelbergMaterials/ASX:HAN). Adbri (ASX:ABC) at Birkenhead SA and Cockburn WA. Downer EDI Road Services (ASX:DOW) — 100+ plants, largest road maintenance contractor. Fulton Hogan (ASX:FHL) Australia-NZ. Independents include Pioneer Construction Materials, Bedrock Asphalt Geelong, Holcim Australia Asphalt, CCS Civil Construction Services. Bitumen refinery: Viva Energy Geelong (ASX:VEA, Shell Bitumen licensed), Ampol Lytton Brisbane (closing), BP Kwinana WA (closed 2021). PMB: SAMI Bitumen Technologies, Puma Bitumen, Shell Bitumen. Crumb rubber: Tyrecycle (Veolia), GDT pyrolysis, ECOFlex, Bitumen Industries Australia.

What is the respirable crystalline silica RCS limit on an Australian asphalt plant?

Safe Work Australia WES for RCS is 0.05 mg/m³ TWA — halved from the previous 0.1 mg/m³ limit and reaffirmed after the engineered stone ban of 2024. Aggregate stockpile, hopper, feeder, conveyor, bucket elevator and dryer feed circuit all generate respirable silica from quartz sand, basalt fines, limestone and dolomite. RCS is the killer hazard in Australian heavy industry, behind the silicosis epidemic that led to the engineered stone ban. AS 3957 dust hazard practice with capture velocity 1.0-1.5 m/s at every transfer point is the engineering control standard, supplemented by AS 1715 P2 or P3 respiratory protection.

What standards govern combustible dust controls on asphalt aggregate handling?

NFPA 660 Standard for Combustible Dust (2025 consolidated edition, replacing NFPA 652, 654, 484, 61, 664, 655) is the international benchmark routinely adopted by Australian asphalt plant engineers, alongside AS 3957. NFPA 68 governs deflagration vent design and NFPA 69 covers explosion prevention by inerting, suppression and isolation. While pure aggregate (basalt, limestone, dolomite) is generally non-combustible, RAP, crumb rubber, fly ash, slag and cement constituents are KSt-rated combustible dusts triggering the dust hazard analysis under NFPA 660 Chapter 7.

How is polymer-modified bitumen PMB classified for ventilation design?

PMB blending vessels produce styrene off-gas (WES 50 ppm STEL), butadiene off-gas (WES 1 ppm STEL — IARC Group 1), EVA volatiles and EPDM propylene/diene off-gas. The PMB blending vessel headspace is Zone 1 hazardous area within the vessel and 3 m from any vent, sample port or top manhole under AS/NZS 60079.10.1. LEV at every addition point, manhole, sample port and shear stage is mandatory. LEV duct in 316L stainless 1.5 mm because polymer condensate is sticky and the duct sees frequent CIP cleaning. Vent discharges to a flame arrester then to a thermal oxidiser or scrubber, not to atmosphere.

What does SBKJ machinery scope cover on an Australian asphalt plant project?

SBKJ standard duct fabrication machinery covers the comfort HVAC scope: control room, weighbridge, lab, workshop, amenities. Galvanised 0.6-1.5 mm to AS/NZS 4254-1 on the SBAL-V auto duct line for rectangular and SBTF-1500/1602/2020 for round spiral. The SBAL-V also fabricates 316L stainless for bitumen LEV and PMB vessel exhaust. SBFB-1500 handles aggregate cold feed LEV at silica RCS transfer points. SBPC1500 plasma cuts heavy plate for flange cut-outs. SB-ZF1500 sheet folder, SBSF-1525 sheet flange machine and SBLR-600 Pittsburgh lockformer complete the workshop. Heavy welded fabrication on dryer exhaust ducting, baghouse, stack and bitumen tank shells is outside SBKJ standard scope.

What ventilation rate applies to bitumen storage tank vent stacks?

Bitumen tank breather vents handle thermal breathing (day/night), working losses (fill/empty cycles) and standing losses (continuous vapour evolution). For a typical 200,000-500,000 L tank at 150-180°C, the breather is sized for the larger of API 2000 thermal breathing or peak fill rate. Vent stack vapour at the breather mouth contains bitumen aerosol, PAH including benzo[a]pyrene IARC 1, H2S from sour-crude bitumen (10 ppm TWA, 15 ppm STEL), and trace VOC. ISO 16852 flame arresters and knock-out pots condense aerosols back to the tank. Discharged stack vapour is routed to an enclosed flare or VRU on newer installations. AS 1940 and AS/NZS 60079.10.1 dictate vent piping in welded carbon steel insulated and heat-traced.

How is crumb rubber asphalt pyrolysis ventilation designed?

Mechanical crumb production (Tyrecycle, ECOFlex) grinds tyres to 0.6-2 mm crumb under aspiration to capture rubber dust and steel cord. Pyrolysis crumb (Green Distillation Technologies GDT) thermally decomposes tyres at 400-600°C in inert atmosphere, producing syngas (CO, H2, CH4), bio-oil, carbon black and steel cord. Pyrolysis duct is AS/NZS 60079 Zone 2 (Zone 1 immediately at reactor seals) plus NFPA 660 for carbon black combustible dust. Carbon black dust collectors have deflagration vents, isolation valves and nitrogen inerting to NFPA 68/69. Pyrolysis kiln seal vents go through a flare or thermal oxidiser, not to atmosphere.

Talk to an SBKJ engineer about your asphalt, bitumen or PMB plant HVAC duct fabrication scope →

SBKJ Group contact

SBKJ Group is the Australian-resident supplier of HVAC duct fabrication machinery to the Australian asphalt, bitumen, PMB and crumb rubber plant market. Based in Box Hill North VIC, SBKJ provides English-language pre-sales engineering, commissioning, training, after-sales service and spare parts across the SBAL-V, SBAL-III, SBSF-1525, SB-ZF1500, SBFB-1500, SBPC1500, SBLR-600 and SBTF-1500/1602/2020 machine range. For asphalt plant HVAC contractors, road maintenance contractors, bitumen refinery operators, PMB blenders and crumb rubber producers working on Boral, Hanson, Adbri, Downer, Fulton Hogan, SAMI, Puma, Viva Energy Geelong, Tyrecycle, GDT, ECOFlex or BIA projects, SBKJ engineering replies within 12 hours.

• Email: sales@sbkjduct.com
• Phone: +61 435 074 994
• Website: sbkjduct.com
• Location: Box Hill North VIC, Australia
• ARBS 2026: May 2026, ICC Sydney — SBKJ Group on the exhibitor floor