Why aquaculture HVAC is a different category of problem
Aquaculture and seafood processing facilities live at the intersection of the four hardest envelopes a building services engineer ever has to design for. They run continuously at 90 to 100 percent relative humidity in hatchery rooms, with a constant background of airborne salt aerosol that pushes coastal corrosion to a level no industrial code anticipated. They generate ammonia from fish-waste exhaust at concentrations that demand dedicated capture and scrubbing. They operate under HACCP-grade food-safety zoning where a single millimetre of unsealed ductwork seam can deliver a Listeria audit finding. And the same building often runs cold-smoke generators at 22 degrees Celsius next door to a blast freezer at minus 38 degrees Celsius, sharing a service corridor whose pressurisation cascade has to be controlled to within five Pascals.
None of those conditions on its own is unusual. A pharmaceutical cleanroom delivers tighter pressurisation. A galvanising shed handles more aggressive humidity. A swine farm runs higher ammonia background. A cold-storage warehouse operates at deeper subzero. What makes aquaculture different is that one facility — frequently one floor of one facility — has to handle every one of those conditions simultaneously, in a building footprint where the duct contractor laid the spiral tubeforming line two years ago and the operator is still adding rotifer rooms today.
That is the brief this guide is written against. SBKJ Group has supplied auto duct production lines and spiral tubeformers in 316L stainless variant to Australian aquaculture facility builders since the early 2000s. Our engineers have walked the floors of every major Tasmanian salmon hatchery, every commercial Queensland prawn pond complex of any scale, and every barramundi processing facility from Bowen to the Daly River. The patterns below are the patterns we see repeated. The mistakes below are the mistakes we see costing operators hundreds of thousands of Australian dollars in rework when the next biosecurity audit arrives.
The Australian aquaculture landscape — operators, species and sites
Before specifying HVAC ductwork for any aquaculture facility, the engineering team has to know the species, the operator, the site type and the regulatory envelope. Australia's aquaculture industry is concentrated in five clusters, each with materially different HVAC requirements.
Tasmanian Atlantic salmon and ocean trout
Tasmania produces the overwhelming majority of Australia's farmed Atlantic salmon, with grow-out concentrated in the Macquarie Harbour, D'Entrecasteaux Channel, Storm Bay and Tasman Peninsula fjord systems. The three large vertically integrated operators — Tassal Group (acquired by Cooke Inc in late 2022, formerly ASX-listed), Huon Aquaculture (acquired by JBS in 2022, integrated hatchery to processing) and Petuna Aquaculture (Cradle Coast, Atlantic salmon and ocean trout) — operate hatcheries on the Tasmanian mainland that supply smolt to marine grow-out pens. The peak industry body, Salmon Tasmania (Saltas), represents these operators and the smaller member companies. Hatcheries run as land-based Recirculating Aquaculture Systems with extreme HVAC requirements; grow-out is at-sea net pen and so the HVAC scope reduces to shore-side feed and packaging facilities. Processing is concentrated at Triabunna, Margate, Margate, Strahan and Devonport.
Port Lincoln southern bluefin tuna
South Australia's Port Lincoln region is the global centre for southern bluefin tuna ranching. Wild-caught juveniles are towed in slow-tow cages from the Great Australian Bight to grow-out pens in Spencer Gulf, where they are fattened on baitfish for 4 to 8 months before harvest. The HVAC scope is shore-side: feed handling sheds, packaging halls, and the substantial blast-freezer infrastructure that supports air-freight export. The Stehr Group, Australian Bluefin Tuna and Sarin Seafood are among the larger operators. Salt aerosol exposure here is severe; the Spencer Gulf ambient is among the most chloride-loaded coastal environments in Australia.
North Queensland tropical prawn and barramundi
North Queensland and the Northern Territory operate Australia's tropical aquaculture cluster. Tasman Sea Farms (formerly Australia Bay Seafoods) operates the largest prawn ponds in the country at Hinchinbrook, supplying black tiger and banana prawns into the domestic and Asian export markets. Pacific Reef Fisheries at Ayr produces barramundi at integrated land-based scale. The 2017 white spot syndrome virus outbreak in the Logan River cluster reset the Australian prawn industry's biosecurity protocols and accelerated the move to fully enclosed, HVAC-conditioned hatchery and broodstock facilities. Tropical ambient conditions (28 to 35 degrees Celsius, 70 to 90 percent RH) reduce the heating load but raise cooling and dehumidification load substantially.
Sydney Rock and Pacific oyster
Oyster culture is concentrated in the Hawkesbury River, Wallis Lake, Port Stephens, Coffin Bay (South Australia) and Tasmanian growers. The grow-out is intertidal longline or rack and bag, so the HVAC scope is the shore-side spat hatchery, depuration tank room, and processing and packing shed. Hatcheries condition larval rearing rooms to 24 to 26 degrees Celsius at controlled humidity; depuration runs at 12 to 14 degrees Celsius for 36 to 42 hours before retail packing. Operators include the family-scale Hawkesbury and Pambula River producers, and the larger Coffin Bay cooperative.
Tasmanian rock lobster, mussel and abalone
Tasmania also hosts the southern rock lobster live-export sector — wet-storage and grading facilities that hold harvested lobster for air freight to Asian markets — and a substantial mussel longline industry on the Spring Bay and northwest coast. Western Australia operates the abalone sector, with land-based farms in Bremer Bay and Augusta running greenlip and brownlip abalone. Each of these subsectors operates HVAC at moderate scale but with the same coastal corrosion exposure as the salmon industry.
What makes aquaculture HVAC mechanically different
Continuous saturation humidity
Hatchery rooms, biofilter rooms, larval rearing rooms and broodstock tanks all operate at relative humidity levels that approach saturation. The water surface area in a typical 200,000-litre RAS broodstock tank, agitated by sumps and mechanical aeration, releases enough water vapour to push room RH to 95 to 100 percent during peak feeding cycles. Standard galvanised ductwork begins surface-rusting at the seam laps within months. Internal duct insulation becomes a microbiological reservoir within the first cleaning cycle. Standard sealing tape adhesives fail. Every component selection is driven by humidity that no commercial HVAC catalogue specs are written for.
Salt aerosol corrosion
Coastal aquaculture sites — and most Australian aquaculture sites are within 5 kilometres of the ocean — sit within the C5-M atmospheric corrosivity category under ISO 9223, the most aggressive marine atmospheric envelope short of full saltwater immersion. Galvanised G275 (275 grams per square metre zinc coating) corrodes through to base steel in 12 to 24 months at coastal Tasmanian and Spencer Gulf locations under continuous exposure. Galvanised G300 extends life modestly. Aluminised steel and Galvalume offer some improvement. None of those finishes is acceptable for facility-life specification. The Australian aquaculture industry has converged on 316L austenitic stainless steel — the molybdenum-bearing grade that resists chloride pitting at saltwater concentrations — as the standard duct material across hatchery, grow-out and processing zones.
Ammonia from fish waste metabolism
Fish excrete ammonia (NH3) directly through the gills as a metabolic product. In a flow-through pond system the dilution rate keeps headspace ammonia below detection. In a Recirculating Aquaculture System with eight to ten times the biomass density of a flow-through pond, ammonia accumulates rapidly in the biofilter room headspace where the recirculating water is degassed and filtered. Safe Work Australia sets the workplace exposure standard for ammonia at 25 ppm 8-hour time-weighted average and 35 ppm short-term exposure limit (15-minute). RAS biofilter rooms without dedicated ammonia capture routinely run 40 to 80 ppm at the breathing zone — well above the legal exposure standard. The HVAC engineering response is dedicated capture ductwork in 316L stainless or polypropylene-lined construction, capture velocity 0.5 to 1.0 metres per second at the source per the ACGIH Industrial Ventilation Manual, and routing to a packed-tower ammonia scrubber before atmosphere release.
Ozone disinfection off-gas
Modern RAS designs rely on ozone (O3) injection to oxidise organic load and disinfect recirculating water. Unreacted ozone offgases at the protein skimmer and degassing tower headspace at concentrations toxic to workers — the workplace exposure standard for ozone is 0.1 ppm 8-hour TWA and 0.3 ppm short-term, an order of magnitude below ammonia. Ozone-laden exhaust must be captured in dedicated polypropylene or 316L ductwork (regular galvanised fails rapidly under ozone exposure) and routed to a thermal or catalytic ozone destructor before release to atmosphere. Recirculating ozone-laden air through general HVAC is a documented worker-injury vector.
Biosecurity and HACCP zoning
Aquaculture biosecurity protocols and seafood HACCP zoning both require fully separated HVAC zones between species, between life stages within a species, between health-status cohorts, and across processing flow gradients. Cross-contamination via shared ductwork is a documented disease vector — the 2017 white spot syndrome virus outbreak in Logan River prawn farms eliminated production from the affected cluster and reset the national biosecurity protocol. Shared HVAC return air across health boundaries is now considered a critical non-conformance on every major aquaculture certification audit (ASC, BAP, Friend of the Sea, ASPCA). The HVAC engineering response is dedicated supply and exhaust ductwork per zone, positive-pressure entry vestibules at 15 to 25 Pascals above adjacent areas for clean zones, foot baths and shower-in protocols, welded longitudinal seam construction in cross-contamination-critical zones, and the elimination of shared return air across health boundaries.
Materials specification — why 316L stainless is non-negotiable
Across every aquaculture and seafood specification we have seen issued by the major Australian operators since 2018, 316L austenitic stainless steel is the default duct material in hatchery, grow-out, biofilter and processing zones. The reasoning is straightforward and worth laying out in detail because procurement teams without aquaculture background frequently propose value-engineering down to galvanised G300 or aluminised steel, and the false economy is severe.
304 versus 316L — molybdenum is the difference
Both 304 and 316L are austenitic stainless steels. Both exhibit excellent atmospheric corrosion resistance in dry industrial environments. The decisive difference for aquaculture is that 316L contains 2 to 3 percent molybdenum where 304 has none, and the molybdenum dramatically improves resistance to chloride-induced pitting. In a coastal aquaculture environment with continuous salt aerosol and intermittent direct saltwater splash, 304 develops pitting corrosion within 2 to 5 years; 316L resists pitting indefinitely at typical exposure concentrations. The cost premium of 316L over 304 is approximately 12 to 18 percent at coil level, and zero at fabrication level if the duct contractor's auto duct line and spiral tubeformer are tooled for 316L. Specifying 304 to save 15 percent at coil cost and replacing failed ductwork in year five is a recurring procurement mistake. Our detailed comparison of galvanised versus stainless duct construction covers the cost-life tradeoffs in depth.
316L versus 316 — low-carbon for weldability
The L in 316L denotes low carbon (under 0.03 percent). This matters because aquaculture-grade ductwork is frequently welded at longitudinal seams for biosecurity-critical zones, and the lower carbon content of 316L resists sensitisation (chromium carbide precipitation at grain boundaries) during welding. Standard 316 sensitises in the heat-affected zone of every weld and develops intergranular corrosion within months in the saltwater-aerosol environment. Specify 316L throughout — there is no aquaculture application where standard 316 is preferable.
Where galvanised steel is permitted
Galvanised G90 or G275 ductwork is permitted in aquaculture facilities only in dry, isolated, mechanically conditioned plant rooms with no direct exposure to salt aerosol, ammonia or process humidity. Typical permitted zones are administrative office areas, dry electrical switch rooms, mezzanine plant rooms above the production floor with positive pressurisation, and feed silo headspace ventilation in dry feed handling. Outside those isolated applications galvanised ductwork is a 24-month replacement programme.
Fibreglass-reinforced plastic (FRP) and polypropylene-lined
For the most aggressive applications — ozone destructor exhaust, ammonia scrubber inlet duct, denitrification reactor offgas — fibreglass-reinforced plastic (FRP) duct or polypropylene-lined steel duct is sometimes specified in preference to 316L. FRP is dimensionally stable, non-conductive, and immune to chloride pitting and ammonia corrosion. The tradeoff is fire performance: FRP requires Class 1 fire-rated resin systems and intumescent coatings to meet the National Construction Code Volume One requirements for exhaust ductwork in food premises. SBKJ does not fabricate FRP duct in-house; we recommend specialist FRP duct subcontractors for those zones and fabricate the 316L stainless balance of the system.
Recirculating Aquaculture System (RAS) HVAC zoning
Land-based Recirculating Aquaculture Systems are the fastest-growing aquaculture facility category globally, and Australia is following the international trend. Atlantic Sapphire (US/Denmark), Nordic Aquafarms, Salmon Evolution and AquaBounty have all built or committed to RAS facilities at industrial scale, and Australian operators including Tassal and Huon are evaluating RAS investment as a hedge against marine grow-out climate risk. A modern salmon RAS facility comprises eight to twelve distinct HVAC zones, each with separate temperature, humidity and biosecurity specifications.
Zone 1 — Hatchery and larval rearing
The hatchery is the most demanding HVAC zone in the facility. Larval salmon are reared at 26 to 28 degrees Celsius with humidity at or near saturation, in tanks under photoperiod control with strict biosecurity isolation. Temperature tolerance is ±0.5 degrees Celsius — tighter than a pharmaceutical cleanroom — because larval mortality climbs sharply outside the species-specific window. Ammonia background is high because larval feeding is intensive and biofilter capacity is matched to small biomass. The HVAC ductwork specification is 316L stainless throughout, welded longitudinal seams, positive pressurisation at +20 Pascals above adjacent zones, dedicated outdoor air supply with HEPA pre-filtration, and dedicated ammonia exhaust to scrubber.
Zone 2 — Grow-out tank room
Grow-out tank rooms hold the bulk biomass, typically 1 to 5 tonnes per cubic metre of water at peak stocking density. Temperature target depends on species: salmon at 14 to 18 degrees Celsius for grow-out and 18 to 22 degrees Celsius for finishing, barramundi at 28 to 32 degrees Celsius, prawns at 28 to 30 degrees. Humidity is 80 to 95 percent RH from tank evaporation. Ammonia load is high. Ductwork is 316L stainless, supply diffusers positioned to avoid direct downflow onto tank surfaces (which accelerates tank evaporation and humidity load), and separate exhaust capture above each tank bank.
Zone 3 — Biofilter and denitrification room
The biofilter room houses the moving-bed bioreactor (MBBR) or rotating biological contactor (RBC) that converts ammonia to nitrate, and the denitrification reactor that converts nitrate to nitrogen gas. Both processes generate NH3, NH4+, N2O and methane offgas. Worker exposure in this room is the limiting design constraint. HVAC ductwork is 316L stainless or polypropylene-lined throughout, with capture hoods directly above each bioreactor, capture velocity 1.0 metres per second minimum, dedicated exhaust to packed-tower ammonia scrubber, and minus 15 Pascal pressurisation relative to adjacent zones. Continuous ammonia monitoring with low-level alarm at 15 ppm and high-level shutdown at 25 ppm 8-hour TWA is standard.
Zone 4 — Mechanical filtration room
Drum filters, microscreens and protein skimmers handle solids removal from the recirculating loop. The room ambient is humid (80 to 95 percent RH) but ammonia load is moderate. Ductwork is 316L stainless, pressurisation neutral or slightly negative relative to grow-out, and exhaust fans handle the aerosol generated by protein skimmers (a confirmed aerosol generator that requires capture).
Zone 5 — Ozone treatment and UV sterilisation
Ozone is generated on-site and injected into the recirculating loop for disinfection and oxidation of residual organic load. UV sterilisation provides secondary disinfection. Ozone offgas at the headspace of the protein skimmer and degassing tower must be captured at 1.0 metres per second minimum capture velocity in dedicated polypropylene or 316L ductwork, and routed to a thermal or catalytic ozone destructor that reduces ozone concentration below 0.1 ppm before atmosphere release. UV ballast cooling exhaust runs through galvanised duct (no chloride exposure) but discharges into the general grow-out exhaust stream.
Zone 6 — Live algae and rotifer rooms
The live algae room cultures phytoplankton (Nannochloropsis, Tetraselmis, Isochrysis) under artificial lighting at 22 to 24 degrees Celsius with controlled photoperiod. Rotifer rooms culture live rotifers as first-feed for marine finfish larvae. Both rooms operate under positive pressurisation with HEPA-filtered supply air to prevent contamination of the live-feed cultures. Ductwork is 316L stainless throughout with welded longitudinal seams.
Zone 7 — Feed handling and silo
Bulk fish feed is delivered as extruded pellets and stored in silos. Silo headspace exhaust handles dust and oil aerosol. Ambient conditions are dry (40 to 60 percent RH on a controlled feed handling line) so galvanised G90 ductwork is acceptable in this zone. Dust extraction at 1.5 metres per second capture velocity at the silo discharge and pneumatic conveyor inlets is standard.
Zone 8 — Mortality and waste handling
The mortality room handles fish mortalities and biofilter biosolids before disposal. Strong ammonia and biological aerosol load. Ductwork is 316L stainless, exhaust direct to atmosphere via biological filter (no recirculation under any circumstances), and minus 25 Pascal pressurisation relative to adjacent zones. Dedicated entry vestibule with shower-in/shower-out protocol on full-scale RAS facilities.
Hatchery HVAC — the most demanding envelope in the facility
The salmon hatchery is the single most demanding HVAC envelope in the entire aquaculture industry. We have walked Tasmanian hatcheries supplying the major operators and seen the same set of design constraints repeated.
Temperature stability ±0.5 degrees Celsius. Larval salmon are reared at species-specific temperatures within a half-degree band. Outside the band mortality rises sharply and growth rate declines. Achieving ±0.5 degrees in a 200 to 1,000 cubic metre room with continuous water-tank evaporation requires high turndown chillers (down to 10 percent of full load), tightly modulated reheat, and supply air diffusion that does not stratify across the room.
Humidity at saturation. Larval rearing tanks are continuously aerated and partially open to the room. Room RH sits at 90 to 100 percent during peak rearing cycles. Cooling coils in the supply air handler run at minus 1 to 4 degrees Celsius coil leaving air temperature to extract latent load, and downstream reheat returns the air to setpoint dry-bulb. The reheat-to-supply ratio is dramatically higher than any commercial HVAC application.
Ammonia exhaust. Larval feeding is intensive (up to 12 feedings per day on first-feed protocols) and generates ammonia faster than the small biofilter capacity can keep up with. Capture exhaust at 0.5 to 1.0 metres per second above each tank bank, route to dedicated ammonia scrubber.
Photoperiod control. Salmon spawning and smoltification are triggered by photoperiod manipulation. The HVAC system has to integrate with the lighting control to avoid heat-load swings during photoperiod transitions.
Biosecurity isolation. Each life stage room — green eggs, eyed eggs, alevins, fry, smolt — is fully separated from adjacent rooms with positive pressurisation and dedicated supply and exhaust. Welded longitudinal seam 316L stainless ductwork is the standard. SBKJ industry coverage of food-grade and biosecurity-grade duct fabrication.
Seafood processing facility HVAC — HACCP zoning
Seafood processing facilities operate under the Australian Food Standards Code and HACCP principles, with zone-by-zone temperature, humidity and pressurisation requirements that drive duct material selection and construction class. The standard zones in a salmon, prawn or barramundi processing facility are as follows.
Receiving and gutting
Whole fish or prawns arrive from the harvest pen or pond. Receiving area runs at 4 to 8 degrees Celsius to slow microbial growth on ungutted product. Heavy water washdown and sanitiser exposure. Ductwork is 316L stainless throughout, with continuous welded longitudinal seams, no internal insulation, and removable cleaning panels at 3-metre intervals. Pressurisation is slightly negative (-5 Pascals) relative to the gutting line because gutting generates aerosol containing fish blood and entrails.
Filleting and trimming
Filleting line runs at 4 to 6 degrees Celsius. Heavy aerosol from trim saws and skinning machines. Same duct construction as receiving (316L stainless, welded seams, removable panels) with additional capture hoods above each saw and skinner at 0.5 metres per second capture velocity to control aerosol.
Brining and curing
Salt brine immersion, dry curing or wet curing of salmon and trout for the smoked product line. Heavy salt exposure at this stage demands 316L throughout. Brine tank rooms run at 2 to 4 degrees Celsius to slow brine activity and microbial growth. Pressurisation neutral.
Cold smoking room
Cold smoke at 18 to 25 degrees Celsius, hardwood combustion (alder, beech, cherry — Australian operators including Petuna and the Tasmanian artisan smokehouses standardise on alder for salmon and beech for ocean trout). Smoke generator capture hood at 0.5 metres per second minimum capture velocity per the ACGIH Industrial Ventilation Manual. Smoke-laden exhaust ductwork is 316L stainless, uninsulated to allow creosote condensate to drain back to the generator, 30-degree minimum slope on horizontal runs, removable cleaning panels at 3-metre intervals. Fire suppression is mandatory — wet chemical or water mist per AS 1851 and the National Construction Code Volume One. We have rebuilt smoking room ductwork three times in the last five years for Australian operators where the original duct contractor specified internally insulated duct (creosote saturates the insulation, the insulation becomes fuel for the next chimney fire).
Hot smoking room
Hot smoke at 60 to 80 degrees Celsius — a higher-temperature drying and smoking process for kippered salmon and barramundi product lines. Same construction as cold smoke (316L stainless, uninsulated, 30-degree slope, fire suppression integrated) but with higher-temperature-rated fire suppression nozzles and higher-grade gasket material at duct joints.
Chilled holding
Finished product holding at 0 to 2 degrees Celsius before packing. Ice slurry holding for whole fish at minus 1 to plus 2 degrees Celsius. Ductwork is 316L stainless with external insulation, vapour-tight seal at all penetrations to prevent condensate ingress into the insulation, and condensate drain trays under all supply diffusers.
Packaging
Modified atmosphere packaging (MAP) lines, vacuum-sealed packing, retail-ready packing. Pressurisation is positive (+15 to +25 Pascals) relative to chilled holding because packaging is the cleanest zone in the flow gradient. ISO 8 cleanroom envelope is specified by some premium-export-grade packaging lines (notably Tasmanian salmon for Japan air-freight). HEPA-filtered supply air, smooth-bore 316L stainless ductwork with welded seams, and full HEPA terminal filters at supply diffusers in ISO 8 zones.
Blast freezing and frozen storage
Blast freezer at minus 30 to minus 40 degrees Celsius for individually quick frozen (IQF) prawns, salmon portions and barramundi fillets. Frozen storage at minus 18 degrees Celsius. Pre-insulated 316L stainless duct panels with vapour-tight seal, condensate drain trays at every penetration, and door-air-curtain integration to limit moisture migration during product loading. Our dedicated cold-storage and cold-chain HVAC guide covers the freezer-specific specification in detail.
Salt aerosol attack — the corrosion timeline operators do not budget for
Coastal Australian aquaculture sites sit firmly within the C5-M atmospheric corrosivity category under ISO 9223. Empirical measurements at Tasmanian salmon hatchery sites show airborne chloride deposition at 50 to 200 milligrams per square metre per day — three to five times the C4 marine threshold and an order of magnitude above the C3 industrial threshold. The corrosion timeline for galvanised G275 ductwork at these sites is brutal:
- Months 0 to 6. Surface bloom on cut edges and exposed fasteners. Cosmetic only.
- Months 6 to 18. White rust (zinc carbonate) spreads across exposed flat surfaces. Galvanic acceleration at fastener heads. Sealing tape adhesives begin lifting.
- Months 18 to 30. Zinc layer breached on edges and fasteners. Red rust appears. Internal duct corrosion accelerates dramatically — once the zinc layer is breached, the steel beneath corrodes at the unprotected rate.
- Months 30 to 60. Through-wall pitting on horizontal duct runs at low points where condensate accumulates. Replacement is the only remedy.
By contrast, 316L stainless steel ductwork at the same sites shows surface tea-staining (cosmetic chromium oxide discolouration) but no measurable corrosion or pitting after 15+ years of continuous exposure. The cost premium of 316L over galvanised G275 at coil level is approximately 4 to 6 times. The replacement cycle ratio is greater than 10 to 1. The total cost of ownership delta strongly favours 316L over the facility life.
Ammonia management — the worker safety driver
Ammonia accumulation in RAS biofilter and grow-out rooms is the single largest worker-safety risk in modern aquaculture HVAC design. The metabolic pathway is straightforward: fish excrete ammonia (NH3) and ammonium (NH4+) through the gills; the recirculating loop carries the ammonia to the moving-bed biofilter where nitrifying bacteria convert it to nitrate; some ammonia degasses to room headspace at the biofilter and at the protein skimmer. In a 5,000 tonne salmon RAS facility, daily ammonia generation is on the order of 50 to 100 kilograms — and a single percent escape to room headspace is sufficient to push breathing-zone concentration above the 25 ppm 8-hour TWA exposure standard.
Capture velocity and hood design
Capture velocity at the source is 0.5 to 1.0 metres per second per the ACGIH Industrial Ventilation Manual. The capture hood geometry depends on the source: rectangular slot hoods above moving-bed biofilter tanks, cone hoods above protein skimmer discharge points, and full enclosure hoods around denitrification reactors. The captured airstream is routed in dedicated 316L stainless or polypropylene-lined ductwork to a packed-tower ammonia scrubber (sulfuric acid scrubbing solution is the industry standard) before atmosphere release.
Continuous monitoring and alarm
Continuous ammonia monitoring is mandatory in every RAS biofilter and grow-out room we have designed. The standard alarm levels are:
- 15 ppm — low-level alarm. Operator-attention notification, exhaust fan ramp-up, increased outdoor air dilution.
- 25 ppm 8-hour TWA — exposure standard threshold. Worker evacuation protocol activated.
- 35 ppm — short-term exposure limit. Mandatory immediate evacuation and emergency exhaust mode.
- 50 ppm — IDLH (immediately dangerous to life and health) approach. Full facility shutdown protocol.
Scrubber design
Packed-tower ammonia scrubbers are sized for the peak ammonia load with 25 percent safety margin. Sulfuric acid (H2SO4) scrubbing solution converts NH3 to ammonium sulfate at the packing surface; the spent scrubber liquor is disposed of as fertiliser feedstock or processed through the facility wastewater treatment train. Scrubber media replacement is annual to biennial depending on load. Plan for the scrubber media replacement cost in facility OPEX — typical annual cost is 0.5 to 1.5 percent of the scrubber capital cost.
Biosecurity — separation, pressurisation, vestibules
Australian aquaculture biosecurity has evolved rapidly since the 2017 white spot syndrome virus outbreak in the Logan River prawn cluster. The HVAC engineering response is now embedded in every major facility specification.
Zone separation
Every species, every life stage, and every health-status cohort gets its own HVAC zone with dedicated supply and exhaust ductwork. Shared return air is prohibited across health boundaries. Supply air can come from a common air handler if and only if the supply ductwork to each zone is fully separated downstream of the AHU and contains no return-air commingling.
Pressurisation cascade
The classic biosecurity pressurisation cascade runs from cleanest (highest pressure) to dirtiest (lowest pressure):
- Larval rearing +25 Pascals
- Hatchery juveniles +20 Pascals
- Grow-out +10 Pascals
- Service corridor 0 Pascals (reference)
- Biofilter / waste handling -15 Pascals
- Mortality processing -25 Pascals
Pressurisation differentials are verified at commissioning with calibrated micromanometers and re-verified at every annual biosecurity audit. Drift outside the design envelope is a non-conformance.
Entry vestibules and personnel flow
Entry to clean zones is via positive-pressure vestibule with foot bath and shower-in protocol on the highest-grade biosecurity facilities. Personnel change protective coveralls between zones; inter-zone foot baths are common; full shower-in/shower-out is standard for hatchery entry on Tassal and Huon facilities. The HVAC engineering implication is that the vestibule itself is a zone with its own supply and exhaust, sized to maintain pressurisation differential during the few seconds when the inner door is open.
Smoking room HVAC — fire safety and creosote management
Australian salmon and barramundi smoking rooms are the highest-fire-risk HVAC zones in any seafood facility. Hardwood combustion at controlled temperature (cold smoke 18 to 25 degrees Celsius, hot smoke 60 to 80 degrees Celsius) generates a smoke-laden airstream rich in volatile organics, creosote precursors, and particulate matter. The combination of elevated temperature, oxygen-rich exhaust path, and combustible deposit accumulation is identical to a commercial kitchen grease duct — and the same fire-safety code applies under NCC Volume One.
Material and slope
Smoking room exhaust ductwork is 316L stainless, uninsulated (creosote condensate must be allowed to drain back to the smoke generator rather than saturate insulation), and sloped at 30 degrees minimum on horizontal runs. Removable cleaning panels at 3-metre intervals allow weekly creosote removal during routine maintenance. Internally insulated duct is the most common construction error and the most common cause of catastrophic chimney fires in Australian smokehouses.
Capture velocity and hood
Smoke generator capture hoods run at 0.5 metres per second minimum capture velocity per the ACGIH Industrial Ventilation Manual, with capture face area sized to fully enclose the smoke generator's smoke discharge. Capture velocity below 0.5 metres per second permits smoke to escape into the smoking room and contaminate adjacent product racks.
Fire suppression
Wet chemical or water mist fire suppression is mandatory per AS 1851 and the relevant NCC Volume One sections. Suppression nozzles are positioned at the duct entry, at every 6-metre interval along the duct run, and at the discharge fan inlet. Annual servicing of suppression heads and ducting is a non-negotiable operating requirement.
Exhaust discharge
Smoke-laden exhaust discharges through a roof-mounted high-velocity stack at minimum 1.5 metres above the highest adjacent roof line and 6 metres horizontally clear of any outdoor air intake on the same or adjacent buildings. Some Australian metropolitan smokehouses are required to include particulate filtration or wet scrubbing on the discharge to meet local air quality regulations.
Cold storage and blast freezer ductwork
The cold-chain end of the seafood processing facility runs from chilled holding at 0 to 2 degrees Celsius through frozen storage at minus 18 degrees Celsius and blast freezing at minus 30 to minus 40 degrees Celsius. Each step of the chain has specific duct construction requirements driven by vapour migration, condensate management, and product quality preservation.
Chilled holding (0 to 2°C)
Pre-insulated 316L stainless duct panels with continuous vapour barrier on the warm side. Condensate drain trays under every supply diffuser to capture moisture migrating into the chilled space when the doors open. Pressurisation slightly positive (+5 Pascals) relative to ambient corridor to limit infiltration of warm humid air.
Frozen storage (-18°C)
Same construction as chilled holding but with thicker insulation (typically 100 to 150 millimetres of polyurethane on the duct panels) and full vapour-tight seal at every penetration. Door air curtains at every personnel and forklift door to limit warm air ingress during loading.
Blast freezer (-30 to -40°C)
Blast freezers operate at high air velocity (3 to 6 metres per second across the product) to maximise heat transfer and minimise the time product spends in the high-quality-loss temperature window between minus 1 and minus 8 degrees Celsius. Duct construction is full pre-insulated 316L stainless with continuous vapour barrier, fan-coil units rated for the operating temperature, and defrost cycle integration. Glycol-charged secondary cooling loops are common where ammonia direct expansion is restricted by site safety case constraints.
For a deeper treatment of the cold-chain end-to-end specification, see our cold storage and cold chain HVAC duct guide.
Feed manufacturing HVAC
Some larger Australian aquaculture operators run on-site fish feed manufacturing rather than buying pelleted feed from external suppliers. The feed manufacturing line is a separate HVAC envelope inside the facility, with extruder, dryer, oil coater and bagging operations.
Extruder line
Twin-screw extruders convert ground fishmeal, plant protein and grain inputs into pelleted feed at 80 to 120 degrees Celsius and 10 to 15 percent moisture. Extruder room is hot (35 to 40 degrees Celsius ambient during operation) and dusty. Dust extraction at the die head, post-extrusion conveyor and cutter at 1.0 to 1.5 metres per second capture velocity. 316L stainless duct preferred for moist feed dust streams; galvanised G90 acceptable for dry low-fat formulations.
Dryer
Hot-air dryers reduce moisture from extrusion to 5 to 8 percent for storage stability. Dryer exhaust at 60 to 90 degrees Celsius carries fine particulate. Specify cyclonic separator or baghouse upstream of the exhaust fan to capture particulate, and 316L stainless or aluminised steel ductwork rated for the operating temperature.
Oil coating and bagging
Oil-coated pellets are tumbled with fish oil to add the lipid content required for grow-out. Oil mist control downstream of the coater is critical — uncontrolled oil mist condenses on every cool surface in the building and creates a slip and fire hazard. Capture at 1.0 metres per second over the coater drum, route through a coalescing oil mist filter, and discharge to atmosphere. Bagging room has dust extraction at the bag filling head and minor pressurisation control.
Explosion protection
Where dust loading meets the dust explosion threshold under AS/NZS 4745, specify explosion venting on the dust collection equipment and explosion-rated dampers on duct penetrations between the feed manufacturing zone and adjacent zones. The risk is highest for dry low-fat formulations; oil-coated finished feed has a lower explosion susceptibility.
Tasmanian salmon — site-specific factors
Tasmania's salmon industry has shaped much of the Australian aquaculture HVAC standard. The fjord locations (Macquarie Harbour, D'Entrecasteaux Channel, Storm Bay, Tasman Peninsula) and shore-side hatcheries (Wayatinah, Cressy, Russell Falls, Triabunna) impose a specific combination of constraints worth calling out.
Cold-water adaptation
Tasmanian Atlantic salmon are reared at lower water temperatures than Norwegian or Scottish equivalents. Hatchery target temperatures sit at the lower end of the 26 to 28 degrees Celsius window for first-feed and drop progressively through smolt production. The HVAC chiller capacity is sized for cooler ambient than tropical aquaculture but reheat capacity is correspondingly higher to handle the temperature transitions through the rearing cycle.
Antibiotic-free production protocol
Tassal, Huon, Petuna and the Saltas-member operators have moved to antibiotic-free production over the last decade. The HVAC implication is that biosecurity becomes the primary disease control mechanism — there is no antibiotic safety net for an HVAC-borne pathogen transfer. Welded longitudinal seam 316L stainless ductwork in cross-contamination-critical zones is the standard, and full HVAC zoning between every life stage is mandatory rather than recommended.
Fjord water quality monitoring integration
The Tasmanian fjord systems are subject to ongoing water-quality monitoring under the Environment Protection Authority Tasmania regulatory regime. Hatchery and processing facility water-side environmental management integrates with HVAC envelope decisions because shore-side discharges must meet the same dissolved oxygen and nitrogen standards as the marine farms. This is more a wastewater integration question than a pure HVAC question, but it appears in every facility design we have worked on.
Fire risk and hardwood smoke
Tasmanian smokehouses standardise on local hardwoods — beech, alder substitute, cherry, and increasingly Tasmanian oak (Eucalyptus regnans, the world's tallest hardwood). The volatile profile is different from Northern Hemisphere alder and beech; the creosote condensate profile is heavier. Smoking room duct cleaning intervals are tighter (typically 7 to 10 days versus 14 to 21 days for European hardwood) and fire suppression specification is correspondingly more aggressive.
Queensland prawn — tropical climate, white spot recovery
Queensland's prawn industry recovered from the 2017 white spot syndrome virus outbreak through industry-wide biosecurity reset that reshaped facility HVAC design across the sector. The lessons are now embedded in the national prawn industry standard.
Hatchery enclosure
Pre-2017 prawn hatcheries operated in semi-open shade structures with passive ventilation. Post-2017 the industry has converged on fully enclosed, HVAC-conditioned hatchery buildings with HEPA-filtered supply air, positive pressurisation, and shower-in entry protocol. The capital cost step-change is substantial but is now considered the cost of biosecurity insurance.
Tropical ambient envelope
North Queensland operates at 28 to 35 degrees Celsius and 70 to 90 percent RH ambient through the wet season. The cooling and dehumidification load is approximately 2.5 to 3 times the equivalent Tasmanian load. Latent load dominates total load through the wet season and drives air handler coil sizing. Reheat is minimal compared to Tasmanian salmon but still required to control dew point in larval rearing rooms.
Pond aeration and shore-side facilities
The grow-out itself happens in earthen ponds aerated by paddlewheel and air diffusers. The HVAC scope is limited to the shore-side hatchery, broodstock facility, feed handling and processing/packing operations. Salt aerosol exposure is severe at the coastal Hinchinbrook and Logan River sites; 316L stainless ductwork is standard.
Land-based RAS — the next decade of Australian investment
Recirculating Aquaculture Systems at salmon-industry scale have moved from pilot to commercial scale globally over the last five years. The international precedents — Atlantic Sapphire's Florida and Denmark facilities, Nordic Aquafarms' Maine and Norway facilities, Salmon Evolution's Norwegian operation — have demonstrated technical viability and exposed the engineering pitfalls.
Australian operator interest has been substantial. Tassal and Huon have both publicly evaluated RAS investment as a hedge against marine grow-out climate risk and stocking density constraints. Several greenfield RAS proposals have been advanced through state-government planning processes in Victoria, South Australia and Tasmania. As of 2026 no Australian salmon RAS facility is yet operating at full commercial scale, but the engineering infrastructure — duct contractors, equipment suppliers, HVAC consultants — is being readied.
The HVAC implications of full-scale RAS investment are significant. A 10,000-tonne-per-year RAS facility runs perhaps 50 distinct HVAC zones, has a duct-fabrication scope of 80 to 150 tonnes of 316L stainless steel, and demands welded longitudinal seam construction across the biosecurity-critical envelope. SBKJ has supplied auto duct lines and spiral tubeformers in 316L variant to international RAS facility builders since 2018, and our SBAL-V 316L stainless variant is the production tooling specifically calibrated for this application. SBAL-V auto duct line catalogue covers the machine specifications.
Hatchery design — specialist sub-zones
Within the hatchery envelope sit a cluster of specialist sub-zones, each with its own HVAC requirements, that together represent the most engineering-intensive part of the facility.
Live algae room
Phytoplankton culture (Nannochloropsis, Tetraselmis, Isochrysis, Pavlova) under artificial lighting and controlled photoperiod. Temperature 22 to 24 degrees Celsius. CO2 dosing into the room via dedicated injection ductwork. Positive pressurisation +20 Pascals. HEPA-filtered supply air to prevent contamination of the live cultures.
Rotifer room
Rotifer (Brachionus plicatilis) culture as first-feed for marine finfish larvae. Temperature 26 to 28 degrees Celsius. Heavy aerosol from agitated culture tanks. Positive pressurisation +15 Pascals. Same HEPA-filtered supply standard as algae room.
Artemia (brine shrimp) hatching
Artemia cysts hatched in cone tanks at 28 to 30 degrees Celsius for 24 hours, then enriched with fatty-acid emulsions before feeding to larval fish. Compact zone but with high evaporation load and ammonia spike during enrichment.
Green-egg and eyed-egg incubation
Salmon eggs incubated in upwelling jars or McDonald jars at species-specific temperature. Tight temperature control ±0.3 degrees Celsius. Photoperiod control with red-light only during egg phases. Compact zone but extreme tolerance.
First-feed and fry rearing
Larvae transition from yolk-sac feeding to live-feed and dry feed. Tank density rises rapidly as fry grow. Ammonia load builds. Duct construction is 316L stainless welded seam throughout.
Smolt and parr rearing
Pre-smolt parr and smolt rearing tanks. Photoperiod manipulation triggers the smoltification process that prepares freshwater fry for marine grow-out. HVAC integration with photoperiod control is critical — heat-load swings during photoperiod transitions can disrupt smoltification.
SBKJ machinery for aquaculture and seafood ductwork
SBKJ Group manufactures the auto duct production lines and spiral tubeformers that Australian aquaculture facility duct contractors run for in-house fabrication. The aquaculture-specific machine configurations are calibrated for 316L stainless steel running at production rates suited to facility-scale duct supply.
SBAL-V auto duct line — 316L stainless variant
Our SBAL-V auto duct line is the workhorse of rectangular duct fabrication for HVAC contractors across 100+ countries. The 316L stainless variant is calibrated for stainless coil with hardened tooling that resists galling and surface contamination. Single-shift output is rated against the buyer's specific 316L coil specification (typical 0.8 to 1.2 millimetre wall thickness, 1,250 millimetre coil width). PLC control is Siemens or Mitsubishi standard. Welded longitudinal seam tooling is available as a factory option for biosecurity-critical zones — 4 to 6 weeks longer lead time but the standard for new salmon and prawn facility builds. Full SBAL-V technical specification.
SBTF spiral tubeformer — 316L stainless variant
Our SBTF spiral tubeformer fabricates round spiral duct from 100 millimetres up to 1,600 millimetre diameter in 316L stainless. Tight-leakage spiral construction with an aerodynamically smooth bore is the preferred geometry for ozone destructor exhaust, ammonia scrubber inlet duct, and several aquaculture transition runs where rectangular duct cannot be routed. Spiral seam quality is critical — under-formed seams leak and over-formed seams crack during installation handling. Full SBTF specification.
TDF flange forming and welded seam options
TDF (Transverse Duct Flange) forming is integrated into the SBAL-V for tight-leakage flanged construction at SMACNA Class A or AS 4254 Class B. For biosecurity-critical zones we recommend welded longitudinal seam construction in lieu of TDF flange because the welded seam eliminates aerosol transfer through the joint. Both options run on the same SBAL-V chassis with toolset changeover at the production line.
Material certificate traceability
Every coil that runs through an SBKJ auto duct line in our Box Hill North VIC supply chain is traceable to mill certificate per ASTM A240 (austenitic stainless plate) or EN 10088-2 (stainless flat product). The traceability documentation accompanies the duct package to the facility, supporting third-party audit requirements at handover.
Standards and regulatory references
Australian aquaculture and seafood facility HVAC ductwork is governed by an overlapping set of standards and codes. The major references that appear in every facility specification are:
- AS 1668.2 — The use of ventilation and air conditioning in buildings — Mechanical ventilation in buildings. Sets minimum outdoor air, exhaust rates and zone separation requirements.
- AS 4254.1 and AS 4254.2 — Ductwork for air-handling systems in buildings. Construction class, sealing class and leakage testing.
- AS 1170.4 — Structural design actions — Earthquake actions in Australia. Seismic restraint of ductwork supports.
- AS 4674 — Design, construction and fit-out of food premises. Food-contact surface hygiene requirements.
- AS/NZS 4745 — Code of practice for handling combustible dusts. Explosion protection on feed manufacturing exhaust.
- AS 1851 — Routine service of fire protection systems and equipment. Fire suppression in smoking rooms.
- National Construction Code Volume One — Building Code of Australia commercial provisions. Fire-rated grease/smoke ducts.
- FSANZ Food Standards Code — Food Standards Australia New Zealand. HACCP zoning requirements for seafood processing.
- Safe Work Australia Workplace Exposure Standards — ammonia (25 ppm 8-hour TWA, 35 ppm STEL), ozone (0.1 ppm 8-hour TWA, 0.3 ppm STEL), hydrogen sulfide (10 ppm 8-hour TWA).
- ACGIH Industrial Ventilation Manual — Capture velocity and hood design for contaminant capture.
- ISO 9223 — Atmospheric corrosivity classification. C5-M category for coastal aquaculture sites.
- ASTM A240 / EN 10088-2 — Austenitic stainless steel mill specifications.
SBKJ engineers are familiar with all of the above and integrate the relevant clauses into machine configuration and fabrication-line setup at quotation stage.
Common specification mistakes — what we see fail
Mistake 1 — Galvanised G275 in the hatchery to save cost at procurement
The most expensive value-engineering decision we see. Galvanised ductwork in the hatchery survives 12 to 24 months before through-wall corrosion appears at low points. Replacement involves shutting the hatchery down for the duct replacement window, which on a major Tasmanian operator is a multi-million-dollar production loss before any duct contractor is invoiced. The 316L stainless premium at procurement is approximately 4 to 6 times the galvanised cost; the avoided replacement loss is two orders of magnitude larger.
Mistake 2 — Internally insulated duct in the smoking room
Creosote condensate saturates internal insulation within months. The insulation becomes fuel for the next chimney fire. We have rebuilt three Australian smokehouse exhaust systems in the last five years where the original duct contractor specified internally insulated duct — every rebuild was triggered by a fire incident.
Mistake 3 — Shared return air across biosecurity boundaries
The single most common biosecurity audit non-conformance. Return air ductwork that crosses between life stages, between species, or between health-status cohorts is a documented disease vector and is now considered a critical non-conformance under ASC, BAP and Friend of the Sea audit protocols. Specify dedicated return air per zone at design stage; retrofitting separation costs 3 to 5 times the design-stage cost.
Mistake 4 — Ammonia exhaust without scrubber
Discharging raw ammonia exhaust to atmosphere fails the worker safety standard (off-property accumulation at adjacent buildings) and the local environmental discharge consent. Always specify a packed-tower ammonia scrubber on the ammonia exhaust stream, sized for peak load with 25 percent safety margin.
Mistake 5 — Ozone offgas commingled with general exhaust
Recirculating ozone-laden air through general HVAC creates worker exposure across the entire facility rather than the small zone where ozone is actually used. Always isolate ozone offgas in dedicated polypropylene or 316L ductwork and route to a thermal or catalytic ozone destructor before atmosphere release.
Mistake 6 — TDF flange in cross-contamination-critical zones
TDF flange joints are excellent for tight-leakage HVAC and meet AS 4254 Class B sealing readily. They are not aerosol-tight at the level required to prevent pathogen transfer in biosecurity-critical zones. Welded longitudinal seam construction is the standard for hatchery exhaust, biofilter exhaust and ozone destructor inlet.
Mistake 7 — Galvanised support brackets on stainless duct
Galvanised threaded rod and galvanised brackets in contact with 316L stainless duct create galvanic cells at the contact line. The galvanised hardware corrodes preferentially and bleeds zinc onto the stainless surface. Specify stainless support hardware throughout where stainless duct is installed.
Lead time, FAT and shipment to Australia
SBKJ's standard lead time for the 316L stainless variant of the SBAL-V auto duct line is 14 to 18 weeks from confirmed deposit to FAT-ready, plus 4 to 6 weeks ocean freight to Melbourne, Sydney, Brisbane or Hobart. The SBTF spiral tubeformer in 316L variant runs 10 to 14 weeks. Welded longitudinal seam tooling adds 2 to 3 weeks to the SBAL-V lead time. Mill certificate traceability and third-party witnessed FAT add 1 to 2 weeks.
Factory Acceptance Test is run before shipment with the buyer's nominated 316L coil specification and a full production cycle. We do not consider an aquaculture-grade machine ready to ship until the FAT report is signed against the contract performance specification. Buyers are welcome to attend the FAT in person or via live video link.
Shipment is on standard 40-foot high-cube container or break-bulk depending on machine size, with ISPM-15 fumigated wood crating, humidity indicators, marine grade desiccant, and full all-risk marine insurance documentation. Australian biosecurity (AQIS) clearance is straightforward for ISPM-15 compliant crating and CE-marked machinery. Our Australia region page covers the shipment and clearance workflow in detail.
How SBKJ supports Australian aquaculture customers
SBKJ Group operates from Box Hill North in Victoria, Australia, with engineering and after-sales support direct to the Australian aquaculture and seafood processing sector. Our typical customer engagement runs through five phases:
- Specification. Engineering review of the facility brief, zone-by-zone duct material and construction class recommendation, machine sizing against production volume.
- Quotation. Itemised landed-cost worksheet on CIF Melbourne or FOB basis, with machine specification, FAT scope, training scope and spare parts package.
- Order and FAT. 30 percent T/T deposit at order confirmation, 70 percent balance against bill of lading copy. FAT run with buyer's 316L coil before shipment.
- Installation and commissioning. 1 to 2 SBKJ engineers on site for 5 to 10 days for installation, mechanical commissioning, electrical commissioning and operator training.
- After-sales. 12-month warranty from commissioning, one-year wear-parts kit shipped with the machine, 72-hour remote support response, 10-year+ parts continuity guarantee.
Talk to an SBKJ engineer about your facility brief — we typically respond within 12 hours during Australian business hours. Contact SBKJ.
FAQ
Why is 316L stainless mandatory rather than galvanised G275?
Aquaculture facilities run continuously in 90 to 100 percent RH with airborne salt aerosol, ammonia from fish-waste exhaust, and ozone offgas. Galvanised G275 corrodes through the zinc layer in 12 to 24 months at coastal Australian sites and accelerates further under ammonia. 316L stainless resists chloride pitting at saltwater concentrations and tolerates the ammonia and ozone exposure that defines RAS hatchery and grow-out environments.
What is the ammonia exposure limit?
Safe Work Australia sets ammonia at 25 ppm 8-hour TWA and 35 ppm STEL. RAS biofilter rooms without dedicated capture run 40 to 80 ppm at the breathing zone. Specify capture at 0.5 to 1.0 m/s per ACGIH IV Manual, route to packed-tower scrubber, monitor continuously with alarm at 15 ppm.
What HVAC zoning does biosecurity require?
Fully separated supply and exhaust per zone, no shared return air across health boundaries, positive pressurisation +15 to +25 Pa for clean zones, foot baths and shower-in protocols, welded longitudinal seam construction in cross-contamination-critical zones.
What duct standard applies to seafood processing?
AS 1668.2 for mechanical ventilation, AS 4674 for food premises construction, FSANZ Food Standards Code for HACCP. Smooth-bore 316L stainless with welded longitudinal seams, no internal insulation, cleaning ports at 3 to 6 metre intervals, condensate trays under chilled supply ducts.
How does smoking room exhaust differ?
Cold smoke 18 to 25°C and hot smoke 60 to 80°C generate creosote condensate that solidifies on cold duct walls. Specify uninsulated 316L stainless with 30-degree minimum slope, capture velocity 0.5 m/s, fire-rated construction per NCC Volume One, integrated wet-chemical or water-mist suppression per AS 1851.
What is the lead time for an aquaculture-spec auto duct line?
SBAL-V in 316L stainless: 14 to 18 weeks plus 4 to 6 weeks ocean freight to Melbourne or Hobart. SBTF spiral tubeformer in 316L: 10 to 14 weeks. Welded seam tooling adds 2 to 3 weeks.
Which Australian operators specify 316L as standard?
Tassal Group (Cooke Inc since 2022), Huon Aquaculture (JBS since 2022), Petuna Aquaculture, Tasman Sea Farms, Pacific Reef Fisheries, the Hawkesbury and Coffin Bay oyster cooperatives, Salmon Tasmania member operators all specify 316L for hatchery and grow-out as standard.
What duct sealing class is required?
SMACNA Class A or AS 4254 Class B minimum, with welded longitudinal seam preferred over TDF flange in cross-contamination-critical zones. Pittsburgh lock alone is insufficient because aerosol-borne pathogens can transfer through unsealed seams at low static pressure.
