Why this reference exists
The AUKUS submarine programme is the largest single defence-industrial undertaking in Australian history. Public commitments place the programme value above USD 245 billion over the next three decades, with the partners — Australia, the United Kingdom and the United States — committing to deliver a conventionally armed nuclear-powered attack submarine capability. Pillar 1 of the AUKUS framework, the submarine pathway, requires Australia to host visiting Virginia-class boats from 2027 under the Submarine Rotational Force-West arrangement, take delivery of three to five Virginia-class submarines from the early 2030s, and stand up a sovereign construction yard to build the SSN-AUKUS class — the trilaterally designed successor submarine — at Henderson on the Cockburn Sound coast of Western Australia from the 2030s onward.
Behind the headline numbers sits a quieter industrial reality: every one of those submarines, frigates and surface combatants will be built inside a hall that needs world-class ventilation. The welders need fume capture, the combat-system technicians need a cleanroom, the paint shop needs an explosion-proof exhaust train, the sandblasting bay needs dust extraction at scale, and every penetration through a security wall needs a duct designed not to give up classified information. The fabric of a submarine construction yard is not the dry dock — it is the kilometres of duct that make the dry dock habitable.
This reference is for the engineers, fabricators and procurement managers tasked with delivering that duct. It is not a tender document, a clearance briefing or a security-controlled specification. It is a public-domain consolidation of the standards stack, the marine atmosphere, the materials, the security overlays and the duct-shop configuration that recur across Henderson, Osborne, Garden Island, HMAS Stirling and Williamstown. SBKJ Group, headquartered in Box Hill North Victoria, supplies HVAC duct fabrication machinery to cleared defence contractors and naval fabricators around the world. The guide below is written from the duct-machine perspective: what the standards say, what the atmosphere demands, what the security envelope requires, and what the duct fabrication shop needs to look like to keep up with the programme.
Section 1 — The AUKUS programme in context
Pillar 1: the submarine pathway
AUKUS is a trilateral security partnership announced in September 2021 between Australia, the United Kingdom and the United States. It is organised around two pillars. Pillar 1 is the submarine pathway: a sequenced transition for Australia from its current Collins-class diesel-electric fleet to a conventionally armed nuclear-powered attack submarine capability. Pillar 2 is the advanced capabilities track covering quantum, hypersonics, artificial intelligence, electronic warfare and undersea capabilities. For the construction infrastructure conversation, Pillar 1 is the dominant driver.
Pillar 1 unfolds in three overlapping phases. The first phase, already in progress, is Submarine Rotational Force-West (SRF-West) — the rotational deployment of United States Virginia-class and United Kingdom Astute-class submarines through HMAS Stirling on Garden Island West in Western Australia, from 2027. The second phase is the sovereign acquisition of three Virginia-class submarines from the United States in the early 2030s, with options for two more. The third phase is the construction of the SSN-AUKUS class — a new trilateral design, built in the United Kingdom for the Royal Navy and in Australia for the Royal Australian Navy at the new Henderson submarine construction yard, with first Australian-built deliveries from the early 2040s.
The construction infrastructure footprint to support that programme is substantial. New construction halls, dry docks, wharves, training schools, combat-system integration facilities, classified storage facilities, maintenance and support workshops, and the supporting administration estate all need to be designed, built and commissioned. The Australian Submarine Agency, established as a statutory authority in 2023, holds the programme management responsibility on the Australian side and works alongside the United States Navy and the United Kingdom Royal Navy authorities on shared interoperability requirements.
The Australian Submarine Agency
The Australian Submarine Agency (ASA) is the Australian Commonwealth’s programme-management authority for the submarine pathway. Established by amendment to the Naval Nuclear Power Safety Act framework in 2023, the ASA is responsible for delivering the AUKUS submarine capability across acquisition, sustainment, infrastructure, workforce, regulatory and nuclear-stewardship lines of effort. The ASA sits within the Defence portfolio but operates as a distinct statutory entity with a direct line to ministerial oversight. For infrastructure works, the ASA coordinates with the Defence Estate and Infrastructure Group and the principal industry contractors to deliver the new buildings, halls, dry docks and wharf infrastructure required at Henderson and at the supporting east-coast and south-coast bases.
Defence Strategic Review and National Defence Strategy
Two policy documents anchor the infrastructure conversation. The Defence Strategic Review 2023 set the strategic posture: a focus on northern Australia, longer-range strike, integrated air and missile defence, and a hardened, resilient defence estate. The National Defence Strategy 2024 carried that posture into a delivery framework, with the AUKUS submarine programme identified as a generational national endeavour and the supporting infrastructure as a critical enabling investment. Together those documents underpin the funding line and the priority assigned to dockyard and construction yard works.
Industry partners
Several industry primes recur across the AUKUS infrastructure footprint. The Henderson Defence Precinct hosts Civmec, Austal and a growing constellation of subcontractors. Osborne Naval Shipyard hosts BAE Systems Australia (Hunter-class frigate programme) and ASC Pty Ltd, which is now consolidated into a larger sovereign defence shipbuilding entity. Saab Australia provides combat-system integration capabilities, particularly relevant to the cleanroom and classified-storage conversation. On the partner side, United States primes such as General Dynamics Electric Boat and Northrop Grumman, and the United Kingdom prime BAE Systems Submarines (Barrow-in-Furness), bring submarine-build pedigree and reference specifications. European groups such as Naval Group (France), TKMS (Germany) and Fincantieri (Italy) recur in adjacent surface-combatant and conventional-submarine programmes globally and inform reference practice on welding fume capture and assembly-hall ventilation. The duct fabricator’s direct customer is typically the mechanical services subcontractor working under the principal industry partner — and the duct fabricator’s machinery supplier sits one further tier behind.
Section 2 — The standards stack
DEF(AUST)10120 — the Australian Defence ductwork standard
DEF(AUST)10120 is the Australian Defence ductwork construction standard most frequently cited on naval and defence-estate projects. It sets out the construction grades, material specifications, pressure classes, seam constructions and inspection regimes acceptable on Defence works in Australia. On naval projects, DEF(AUST)10120 sits alongside AS 1668.2 (the use of ventilation and air-conditioning in buildings — mechanical ventilation) and AS/NZS 4254 (ductwork for air-handling systems in buildings) to form the baseline duct standards stack. DEF(AUST)10120 typically adds material grade requirements, weld inspection requirements, security cross-section requirements at penetrations and acceptance test requirements above those in the civilian standards.
AS 1668.2 and AS/NZS 4254
AS 1668.2 is the Australian mechanical ventilation code. It establishes minimum outdoor-air rates, exhaust requirements for contaminant sources, smoke management requirements, fire-mode ventilation and the general framework that any ducted ventilation system in Australia is designed against. AS/NZS 4254 (in two parts — flexible duct and rigid duct) sets the construction requirements for ductwork: pressure classes, leakage classes, seam constructions, hangers, supports and reinforcement. On a defence project the civilian standards form the floor — DEF(AUST)10120 raises the ceiling.
Defence Estate Management Manual (DEMM)
The Defence Estate Management Manual (DEMM) is the Australian Department of Defence’s suite of guidance for the planning, delivery, operation and disposal of defence estate. For mechanical services, the DEMM directs designers to the relevant Australian Standards, DEF(AUST) series specifications and any project-specific Functional Performance Specifications (FPS) issued by Defence. It also sets the asset-handover regime: the documentation, inspection records, commissioning data and as-built drawings required at practical completion. Duct fabricators feeding a Defence project should expect a more comprehensive handover dossier than a comparable commercial project — material traceability mill certificates, weld procedure specifications, welder qualification records, weld inspection records, passivation reports for stainless duct and full air-balance commissioning data are typical inclusions.
NAVSEA references — the United States interoperability layer
For spaces that host United States Navy assets — most prominently the Virginia-class rotational hosting at HMAS Stirling under SRF-West — interoperability with United States Navy ventilation practice matters. The Naval Sea Systems Command (NAVSEA) publishes a family of technical references covering shipboard and shore-facility ventilation, fume control, paint-shop ventilation, sandblasting extraction and submarine-base support facility ventilation. These references inform the design of any space that interfaces directly with a Virginia-class submarine, including dry-dock plant rooms, wharf-side support buildings, classified-storage rooms holding United States-origin material under bilateral arrangements, and combat-system integration spaces.
JSP 318 and DefStan — the United Kingdom interoperability layer
The United Kingdom Ministry of Defence publishes Joint Service Publications, including JSP 318 (Regulation of Aviation and JSP 375 family on Health and Safety at Work; the broader JSP family covers the defence estate ventilation envelope), and a family of Defence Standards (DefStan) including DefStan 02-series covering naval engineering practice. On AUKUS projects with United Kingdom design lineage — and the SSN-AUKUS class carries substantial United Kingdom design content — the United Kingdom reference set layers over the Australian stack at the interfaces. The duct fabricator does not need to be the world expert on the United Kingdom standards; it is the responsibility of the principal contractor and the mechanical services consultant to translate the United Kingdom requirements into a clear Australian-jurisdiction specification. The fabricator’s task is to deliver duct that satisfies that translated specification.
Cleanroom and electromagnetic standards
Combat-system integration spaces and similar electronics-heavy rooms commonly target ISO 14644 Class 7 cleanroom classification. ISO 14644 governs particle counts, change rates, recovery times and the duct and HEPA module configuration needed to achieve them. TEMPEST emissions security — the discipline of controlling unintended electromagnetic emanations from classified systems — adds an electromagnetic compatibility overlay. Where a duct passes through a TEMPEST zone boundary, it must not act as a waveguide that leaks radiated emanations. Design practice includes electromagnetic-shielded duct construction, honeycomb vent panels at boundary penetrations, and continuous bonding of duct sections through the boundary.
NUREG-1.140 and the nuclear-relevant overlay
For spaces with a nuclear-relevant function — and the Virginia-class rotational hosting and the eventual SSN-AUKUS construction yard both bring nuclear-relevant considerations to the dockyard envelope — United States Nuclear Regulatory Commission Regulatory Guide 1.140 sets out the design, inspection and testing of normal ventilation exhaust systems in nuclear power plants. NUREG-1.140 is not directly applicable to a naval submarine programme regulated under separate frameworks (the United States Naval Reactors authority, Australian Naval Nuclear Power Safety Regulator and similar United Kingdom and partner-jurisdiction authorities). It does, however, codify a body of nuclear-ventilation practice that informs the design philosophy: redundancy, segregation, HEPA filtration, monitoring, leak-tight duct construction and air-balance verification. Where a duct in an Australian naval dockyard carries a nuclear-relevant function, the fabrication and inspection regime tightens accordingly.
Section 3 — The Australian dockyard map
Henderson Defence Precinct, Western Australia
The Henderson Defence Precinct sits on the coast south of Fremantle, on Cockburn Sound in Western Australia. It is the announced location of Australia’s AUKUS submarine construction yard, with construction works ramping through the late 2020s and a sovereign submarine build capability targeted for the early 2030s. Henderson is already home to Civmec, Austal and a network of mechanical and electrical subcontractors supporting Royal Australian Navy patrol-boat, offshore-patrol-vessel and amphibious-craft work. The submarine construction expansion adds a new construction hall, a dedicated submarine assembly building, a new floating dock or graving dock, support buildings for combat-system integration and classified storage, a sandblasting and paint hall, training facilities and an enlarged industrial precinct.
For the duct fabricator, the Henderson programme is the single largest forward demand signal in the Australian dockyard market. The submarine assembly hall is a hi-bay enclosed building with strict dust-control, climate-stability and welding-fume-capture requirements. The supporting buildings carry the full range of security overlays. The duct material set is dominated by 316L stainless steel; the seam construction by continuous TIG welding; the fabrication shop by stainless-rated coil lines and seam welders running in a controlled environment.
Osborne Naval Shipyard, South Australia
Osborne Naval Shipyard at Port Adelaide is the south-coast hub of Australian sovereign naval shipbuilding. It hosts the Hunter-class frigate programme, run by BAE Systems Australia, and the broader sovereign shipbuilding capability consolidated around ASC and the Commonwealth’s shipbuilding entities. Osborne’s relevance to the AUKUS submarine programme is indirect — the primary submarine build move is to Henderson — but its surface-combatant ventilation work, modular construction hall ductwork, paint shop and combat-system integration spaces are reference-class examples of the discipline. The fabricators serving Osborne have developed deep capability in stainless duct, security ductwork and assembly-hall ventilation that translates directly to the Henderson submarine yard.
Garden Island East, Sydney
Garden Island East in Sydney Harbour is the location of HMAS Kuttabul, the Royal Australian Navy’s east-coast fleet base. It is a mature naval base with a long history of surface-ship operation, maintenance and refit. Its HVAC duct asset base is heterogeneous — heritage buildings, mid-life utility plant, contemporary mechanical services — and the ongoing refurbishment and replacement programme is a steady source of marine-grade duct work. The base is exposed to the marine atmosphere of Sydney Harbour with strong south-easterly weather patterns, and the duct material specification reflects that exposure.
Garden Island West, Sydney — Captain Cook Graving Dock
Garden Island West in Sydney is the location of the Captain Cook Graving Dock. The dock is one of the largest graving docks in the southern hemisphere and a critical national asset for surface-ship docking, hull cleaning and underwater-hull maintenance. It is also relevant to the submarine maintenance conversation as a possible east-coast maintenance node. The ventilation requirements around a graving dock are demanding: high air-change rates in the dock chamber during paint or chemical work, robust fume-extraction, marine-atmosphere duct construction in the splash zone, and redundant ventilation to the supporting plant rooms. Any duct material below 316L stainless steel in the splash zone has a very short asset life.
HMAS Stirling, Garden Island West, Western Australia
HMAS Stirling sits on Garden Island in Cockburn Sound, the same body of water that hosts the Henderson Defence Precinct on its eastern shore. It is the Royal Australian Navy’s primary submarine base and the announced host site for Submarine Rotational Force-West from 2027 — the rotational presence of United States Virginia-class and United Kingdom Astute-class submarines on Australian soil. Stirling is the focus of an extensive infrastructure upgrade programme: new wharves, new support buildings, classified-storage facilities, training schools, fuel and stores buildings and significant mechanical services upgrades. The duct asset register at Stirling will grow significantly between now and 2030.
Stirling is also where the most demanding interoperability-driven specifications are felt. The site must support Virginia-class operations under United States Navy support practice and the local Royal Australian Navy operating regime. Mechanical services specifications carry the dual layer of Australian standards and United States Navy interoperability requirements at the interfaces.
Williamstown Dockyard, Victoria
The Williamstown Dockyard sits on the western side of Port Phillip Bay in Melbourne. It is one of the oldest continually used shipyards in Australia, with a build history including the Adelaide-class frigate and other surface combatants. Modern operations are reduced — the site is no longer the dominant shipbuilding node it once was — but it retains relevance as a heritage facility and as a regional maintenance and refit option. For the duct fabricator, Williamstown is closer to home than the west-coast and south-coast sites and offers a familiar Victorian regulatory and supply environment for refurbishment-grade marine duct work.
Section 4 — The marine atmosphere envelope
ISO 9223 corrosivity categories
ISO 9223 is the international standard that classifies atmospheric corrosivity into six categories from C1 (very low) to CX (extreme). The categories combine the deposition of chloride and sulphur dioxide with the time-of-wetness on the surface. Each Australian naval dockyard sits in the upper categories. Henderson on Cockburn Sound, HMAS Stirling on Garden Island, Garden Island East and West in Sydney Harbour, and Osborne on Port Adelaide are all coastal sites with sustained marine aerosol exposure. Their effective corrosivity category for exterior steelwork is C5-M — very high, marine. Williamstown on Port Phillip Bay is similarly classed at C4 to C5-M depending on location within the site.
The corrosivity category determines the duct material set. Carbon steel in a C5-M envelope corrodes at first-year rates measured in tens of grams per square metre. Galvanised steel performs better but loses its zinc layer within a small number of years under sustained marine exposure and is typically rejected on serious defence specifications unless protected by a heavy-duty coating system to ISO 12944 C5-M durability class “very high”. Aluminium suffers from chloride pitting and crevice corrosion. The material of choice for exterior and shoreline duct in the C5-M envelope is 316L austenitic stainless steel.
Why 316L stainless
Type 316L is a molybdenum-bearing austenitic stainless steel with low carbon (the “L” grade). The molybdenum content lifts pitting and crevice-corrosion resistance in chloride environments compared with 304 stainless. The low carbon content avoids carbide precipitation in the heat-affected zone of welds, preserving the corrosion resistance of the seam. For a marine-atmosphere duct that will be cleaned, splashed and sometimes hosed in service, 316L is the well-validated material choice. It is not the cheapest stainless on offer — duplex stainless grades and higher-alloy stainless steels exist — but its weldability, formability and well-understood behaviour in HVAC duct service make it the default.
Seam construction in the C5-M envelope
The duct seam is the weak link in marine-atmosphere service. Mechanical lock-form seams (Pittsburgh seam, snap-lock, button-punch) trap chlorides in the seam crevice and crevice-corrode from inside the lap. Spot-welded seams behave similarly at the spots. The construction of choice for exterior duct in a C5-M envelope is a continuous longitudinal TIG-welded seam, full strength, on 316L stainless coil. The weld is then passivated to restore the chromium-rich oxide layer in the heat-affected zone. The result is a duct that has no chloride-trapping crevice on the seam line and that performs at the corrosion-resistance level of the parent stainless throughout its life.
SBKJ’s SBAL-V stainless duct line is configured for this work: a stainless-rated coil cradle and forming train, an integrated TIG seam welder, and a passivation handling regime that lets the fabricator close out the seam to a continuous corrosion-resistant joint. The line is supplied to cleared fabricators who set up the stainless workstations in their shop and run the work under their own quality and security framework.
Joint sealing and gasket selection
In a C5-M envelope the duct joints matter as much as the seams. The gasket selection should favour materials resistant to marine atmosphere and to the cleaning regimes used on the asset — typically EPDM or silicone gaskets in stainless joints, with stainless or coated fasteners to avoid galvanic couples. Galvanic couples — carbon-steel screws into stainless flanges, for example — corrode aggressively in the C5-M envelope and should be designed out at the shop-drawing stage.
Section 5 — Security overlays
SCIF ductwork
A Sensitive Compartmented Information Facility is a hardened room or suite of rooms used to process classified material. The construction of a SCIF is governed by detailed and largely access-controlled specifications issued by the relevant security authority — in Australia, the Australian Government Security Vetting Agency and the Department of Defence’s security framework, with reference to allied United States and United Kingdom standards under the AUKUS interoperability arrangements. The duct requirements that recur in the public-domain framing of these standards include the following.
First, anti-contraband and anti-intrusion cross-sections at the boundary penetration. Any duct that passes through a SCIF boundary wall must be small enough — commonly 96 mm or smaller on any dimension at the penetration — to refuse covert human or contraband entry, or must be fitted with a security barrier (mesh, grille, baffle) that achieves the same end. Second, tamper-resistant grilles and inspection covers at the boundary. Any inspection point that breaches the wall must be visible, tamper-evident and lockable. Third, acoustic baffles to defeat audio egress through the duct path. Fourth, continuous welded seams that resist tampering and re-entry. Fifth, dedicated SCIF AHUs and exhaust trains that do not share airflow with non-SCIF spaces; or, where shared trains are unavoidable, isolation dampers and back-flow protection that meet the security framework.
The SCIF duct is fabricated and installed by a contractor holding the appropriate security clearance, working under a programme governed by the cleared principal. SBKJ’s role in this conversation is upstream: the SBAL-V stainless line with its TIG seam welder, security mesh integration handling and Class A sealed-seam capability provides the cleared fabricator with the tooling needed to produce SCIF-grade duct. SBKJ itself does not hold AUKUS or partner-jurisdiction security clearance.
TEMPEST emissions security
TEMPEST is the discipline of controlling the unintended electromagnetic emanations from classified systems — the radiated signals that an adversary could intercept and reconstruct to recover the information being processed. TEMPEST design touches building shielding, cable routing, grounding, and ventilation. Where a duct passes through a TEMPEST zone boundary it must not act as a waveguide that leaks emanations from the protected zone to the outside world. The design responses are well established: electromagnetic-shielded duct construction (continuous-welded stainless or copper-clad sheet) bonded to the boundary shield; honeycomb air-vent panels at boundary penetrations that pass air but choke emanations across a controlled cut-off frequency; continuous electrical bonding of duct sections through the boundary; and grilles and registers that integrate into the shielded envelope. As with SCIF, the detailed TEMPEST specifications are access-controlled. The fabrication implication is clear: the fabricator needs a duct line that can produce continuous-welded shielded duct sections at the dimensions and tolerances the cleared specification requires.
96 mm anti-contraband cross-section
The 96 mm dimension — frequently cited as a threshold for anti-contraband duct cross-section — is the public-domain rule of thumb for the largest dimension of a duct opening that cannot be entered by a person or used to push contraband through. Detailed security specifications may quote tighter or different dimensions, and may layer additional barriers (mesh, bars, baffles) onto larger ducts that are unavoidable on the airflow side. The shop-drawing implication is the same: every duct penetration through a security boundary needs a cross-section design that satisfies the security framework, and that design has to be coordinated between the mechanical services consultant, the security consultant and the fabricator at shop-drawing stage rather than discovered at site fit-out.
Air-gap construction at perimeter walls
An additional security and acoustic technique used at perimeter walls is air-gap construction: the duct from the secure side terminates short of the wall, an air gap is bridged by an acoustic and security barrier, and the duct on the non-secure side starts again on the other side of the gap. The air gap, with its baffles and grilles, defeats acoustic and contraband paths along the duct line while preserving the airflow. Air-gap construction details are coordinated by the cleared contractor.
ITAR-controlled spaces
The International Traffic in Arms Regulations (ITAR) are a United States regulatory framework controlling the export and re-export of defence-related articles and technical data. Several AUKUS-relevant spaces — particularly combat-system integration rooms and classified-storage rooms holding United States-origin material — are designated as ITAR-controlled, with personnel access restricted to United States persons or pre-authorised foreign nationals. The construction of these spaces, and the duct that ventilates them, is delivered under contract terms that recognise the ITAR restrictions. SBKJ’s role here, again, is upstream — supplying duct fabrication machinery to cleared contractors operating under ITAR-aware contracts. SBKJ does not handle ITAR-controlled technical data and does not contract directly into ITAR-controlled space delivery.
Section 6 — The construction-hall ventilation problem
The submarine assembly hall
A submarine assembly hall is a hi-bay enclosed building, often 30 to 50 metres clear height, hundreds of metres long and tens of metres wide, with overhead cranes, large openings at the ends for hull transfer, and an internal environment that must support precision steel work, machinery installation, weld inspection, and increasingly the integration of combat-system electronics inside hull sections. The ventilation problem is multi-layered.
The first layer is climate stability. Steel hull sections weld and machine differently as ambient temperature changes; precision-fit work demands tight tolerance bands. The hall is conditioned to a controlled temperature and humidity envelope — often around 20 to 24 degrees Celsius with relative humidity in the 40 to 60 percent band — across its full volume. The duct system distributes large volumes of conditioned air at low velocities to avoid creating draughts that disturb welding shielding gas or stir up settled fume and dust.
The second layer is dust control. The hall is kept clean — far cleaner than a general fabrication shop — to protect the precision work being performed and to prepare the hull for combat-system integration. Filtration is high-efficiency at the AHU and at the local terminal modules.
The third layer is welding fume capture. Submarine hull welding generates very large quantities of welding fume. A single shift in a busy hall can produce six kilograms or more of welding fume from active welding bays. The fume contains nickel, chromium and manganese compounds at concentrations of regulatory concern. The design response is source-capture extraction at each welding bay — local hoods, on-torch extraction, mobile extraction arms — combined with hall-level dilution ventilation sized to AS 1668.2 and the relevant occupational health and safety code. The extraction duct material is selected for compatibility with welding fume, with abrasion in the duct from particulate transport, and with the cleaning regime used on the duct in service.
Sandblasting and surface preparation
Hull sections are sandblasted (or, more commonly today, grit-blasted with a recyclable abrasive media) to prepare the surface for primer and topcoat. The sandblasting bay is a dedicated, enclosed space with very high air-change rates, dust extraction at scale, and a duct system that handles abrasive dust. The duct material is selected to resist erosion from the abrasive — typically heavier-gauge steel duct with abrasion-resistant linings at the high-wear points (elbows, transitions, dampers). The extraction discharges to a baghouse or cartridge filter and a stack.
Paint shop and polyurethane VOC capture
Paint shops on naval hulls apply primers and topcoats — frequently two-pack polyurethane systems — that release significant volatile organic compounds (VOCs) and that may include isocyanate components requiring strict respiratory control. The ventilation system is designed to NFPA 33 (Standard for Spray Application Using Flammable or Combustible Materials) or its equivalent in the local jurisdiction. The booth provides airflow to control overspray and to keep VOC concentrations below the lower flammable limit and the relevant occupational exposure limit. The exhaust train is either filtered through a paint filter bank or, on larger systems, abated through a thermal or catalytic oxidiser before discharge. The duct material is selected to resist solvent attack — stainless or coated steel.
Combat-system integration room
The combat-system integration room is where the submarine’s combat-system electronics are installed, calibrated and tested as a hull section is fitted out. It is typically classified ISO 14644 Class 7 (particle counts of 352,000 particles per cubic metre at 0.5 microns and larger) and is operated as a positive-pressure cleanroom. The duct material is 316L stainless with continuous welded seams; HEPA filtration is provided at the terminal modules; pressure cascades are coordinated to keep the cleanroom positive against the surrounding spaces. The room also carries security overlays — it commonly meets SCIF requirements and may be ITAR-controlled — so the duct construction is the intersection of cleanroom, security and marine-atmosphere considerations.
Boatlift and floating dock environments
A boatlift or floating dock at the dockyard is a high-corrosivity environment with continuous saltwater exposure. The ventilation plant supporting these assets — mostly enclosed plant rooms on the dock or in adjacent buildings — sits in a localised C5-M envelope. Duct material is 316L stainless throughout, with sealed-seam construction and stainless fasteners. Cable penetrations and pipe penetrations through the duct system are sealed against water and dust ingress.
Section 7 — Redundancy and resilience
N+1 minimum, N+2 for combat zones
Redundancy is sized to the criticality of the served space. The general rule across the AUKUS infrastructure footprint is N+1 minimum redundancy on AHUs, exhaust fans, chillers and pumps — that is, one additional unit beyond the number needed to meet the design load, so the system continues to operate at full capacity through any single failure or planned maintenance event. For combat-system integration spaces, classified-storage rooms and other mission-critical spaces, the redundancy posture lifts to N+2: two additional units beyond the design count, providing tolerance to a fault during maintenance.
Redundancy in the duct system itself means cross-linked supply and exhaust trains so a single duct breach does not eliminate ventilation to a critical space. The design includes isolation dampers, alternative airpaths, and the ability to route supply and exhaust through either of two trains. The control system layers in automatic changeover on detected failure and operator-controlled switchover for planned maintenance.
24/7 operation
Most naval dockyard buildings operate continuously. The ventilation systems are designed for continuous duty with planned maintenance windows that do not interrupt service to critical spaces. Components are selected for continuous-duty rating, bearings and motors are oversized, and the duct supports are designed for the vibration regime of continuous operation.
Resilience to attack and accident
Critical defence facilities are designed against a wider range of threats than a commercial building. The duct system is segregated from areas that pose a fire, blast or contaminant risk; smoke-management duct is fire-rated to the relevant standard; chemical, biological, radiological and nuclear (CBRN) filtration is provided to the high-priority spaces; and the duct system is bonded into the building’s overall protective-design framework. The detailed threat-modelling is performed by the principal contractor and the security authority — the duct fabricator delivers the duct that the threat-model requires.
Section 8 — The duct fabrication shop
Shop layout and material flow
A fabrication shop serving the AUKUS infrastructure footprint at scale needs to be set up around three primary material streams: 316L stainless steel coil for the bulk of the duct, heavier stainless or coated steel for the abrasion-loaded extraction duct, and a residual carbon-steel or galvanised-steel stream for the few interior climate-controlled spaces that permit it. The most important shop-layout discipline is the strict separation of stainless work from carbon-steel work. Cross-contamination from carbon-steel grinding dust or fragments embedded in stainless surfaces causes rust spotting, ruins the corrosion-resistance of the part, and can fail inspection at the supplier.
The practical response is dedicated stainless workstations physically isolated from the carbon-steel area: separate coil cradles, separate forming trains, separate weld bays, separate grinding and finishing zones, separate handling equipment, and a passivation bay sited within the stainless zone. The SBKJ SBAL-V stainless duct line is sized and configured for this work and is supplied with the recommendations for shop layout that the cleared fabricator implements in their own facility.
TIG seam welding
The longitudinal seam on a stainless rectangular duct is a continuous TIG weld run with appropriate shielding gas (argon-based or argon-hydrogen mixture), with backing-gas purge inside the duct to prevent oxidation on the inside surface, and with weld parameters tuned for the gauge and width of the work. The SBAL-V line includes the TIG seam welder integrated into the coil-line motion control, so the weld is laid down at a controlled rate as the duct profile is formed. After welding, the weld zone is passivated to restore the chromium-rich oxide layer in the heat-affected zone — typically a pickling-paste or pickling-bath process followed by neutralisation and rinsing.
Sealed-seam Class A duct
AS/NZS 4254 Class A is the highest leakage class commonly specified in the Australian framework — duct that leaks no more than a small fraction of the air volume per unit area at the duct working pressure. On defence projects, sealed-seam Class A construction is the norm for any duct that crosses a security boundary, any duct in a cleanroom, and any duct carrying a contaminant where leakage matters. The fabrication discipline to achieve Class A is rigorous: continuous welded seams, gasketed and bolted joints, and full leakage testing on representative duct sections at acceptance. The SBAL-V line is configured to produce Class A duct to AS/NZS 4254 with the appropriate seam and joint detailing.
Security mesh integration
SCIF and security-boundary duct frequently includes mesh, grilles or baffles integrated into the duct fabrication rather than added on site. The fabrication process accommodates these inserts as part of the seam welding sequence, with the mesh placed and clamped before the duct is closed out and welded around it. The SBAL-V line handles this insertion as a stop-and-clamp step within the production sequence, allowing the cleared fabricator to build security mesh into the duct line product rather than retrofit it.
Documentation and traceability
Every duct length on a defence project carries a documentation tail: the material mill certificate identifying the heat number of the parent stainless, the weld procedure specification (WPS) used on the seam, the welder identification (and qualification record) of the welder who ran the weld, the visual and dimensional inspection record, the passivation record where applicable, and the final shop-drawing reference. The fabrication shop maintains this paper-trail in a quality-management system that supports the asset-handover regime under the Defence Estate Management Manual. SBKJ’s SBAL-V line includes a duct-tagging and data-capture option that feeds straight into the fabricator’s quality-management system.
Section 9 — Working with cleared contractors
The supply chain structure
An AUKUS construction-yard mechanical services package is delivered through a tiered supply chain. At the top sits the Commonwealth (via the Australian Submarine Agency, the Defence Estate and Infrastructure Group and the project authority for the specific package) and the principal industry contractor (Civmec at Henderson, BAE Systems Australia at Osborne, or whoever holds the package). Below sits the mechanical services contractor, who designs and installs the HVAC for the building or precinct. Below that sits the duct fabricator, who manufactures the duct under the mechanical services contractor’s direction. Below that sits the duct machinery supplier, who provides the fabrication shop with the tooling to do the work.
The security clearance lives in the upper tiers of this stack. The cleared mechanical services contractor or the cleared duct fabricator holds the personnel vetting, the facility clearance, the ITAR authorisation where required, and the contractual responsibility for delivering the duct under the security framework. The duct machinery supplier — SBKJ — supplies the tools to the cleared fabricator on a normal commercial basis. SBKJ does not require AUKUS security clearance to sell duct machinery to a cleared fabricator, and does not claim to hold AUKUS clearance.
What SBKJ supplies
SBKJ supplies the duct fabrication machinery configured for the work the cleared fabricator needs to deliver. For an AUKUS construction-yard fit-out, the typical SBKJ package includes the SBAL-V stainless duct line configured for 316L coil, the TIG seam welder integrated into the line, sealed-seam Class A capability, security mesh integration handling, the duct-tagging and traceability option, the operator and maintenance training package, the spare-parts kit, and the after-sales support framework operated from the SBKJ Box Hill North Victoria office. The cleared fabricator runs the work under their own security and quality framework.
Reference language for tender responses
Mechanical services contractors and duct fabricators responding to AUKUS-related tenders sometimes ask for reference language for the duct fabrication machinery section of their response. SBKJ provides letters of capability, equipment specifications, certifications (CE, ISO 9001), and reference installations on request. The reference content does not extend to security-sensitive claims — SBKJ does not assert that its machines or its company have AUKUS clearance, and does not include such claims in any supporting documentation.
Section 10 — A worked example: a notional submarine assembly hall
The building
Consider a notional submarine assembly hall at Henderson: 250 metres long, 60 metres wide, 40 metres clear height, with three internal work bays separated by movable partitions, a sandblasting bay at one end, a paint shop at the other, an attached combat-system integration room of ISO 14644 Class 7 specification, and supporting plant rooms and office mezzanines. The hall is on the shoreline; its exterior duct sits in C5-M; its interior duct serves a controlled environment.
The duct asset register
The duct asset register for the building runs to many kilometres of supply, return and exhaust duct. The main air-handling units sit on the plant-room roof or in dedicated plant rooms; the duct fans out to terminal modules at low velocity across the bay; the welding fume capture sits at each active welding station and is ducted to a central abatement plant. The sandblasting bay has its own dedicated extraction. The paint shop is fully enclosed with its own supply and exhaust trains discharging through a paint filter bank or a thermal oxidiser. The combat-system integration room operates as a positive-pressure cleanroom with HEPA terminal modules and a dedicated AHU sized for the change rate and the heat load.
The material breakdown
For this notional building, a typical material breakdown would put 316L stainless at well over half of the duct mass — most exterior, most plant-room, most cleanroom and most security-boundary duct. The remaining mass is split between coated or stainless heavy-gauge duct on the sandblasting and paint-shop extraction, where abrasion or solvent attack matters, and a residual share of galvanised duct in fully interior climate-controlled spaces where the project specification explicitly permits it. The seam construction is overwhelmingly continuous TIG-welded on the stainless work; the joint construction is bolted-and-gasketed at sections, with welded joints at security boundaries.
The fabrication-shop response
A fabricator delivering this package needs at least one SBAL-V class stainless duct line, a TIG seam welder, a passivation bay, a clean staging area to keep finished stainless out of the carbon-steel zone, a security-mesh integration capability, a documentation regime to support the handover, and a project management overlay that sequences fabrication against the site installation programme. SBKJ supplies the line and the integrated tooling. The cleared fabricator brings the people, the security framework, the project management and the site delivery capability.
Section 11 — How SBKJ fits the AUKUS supply chain
What SBKJ is
SBKJ Group is an HVAC duct fabrication machinery manufacturer headquartered in Box Hill North Victoria. The company supplies coil-fed duct production lines, stainless duct lines, seam welders, plasma cutters, gore lockers, stitchwelders and bending machines to mechanical services contractors and duct fabricators internationally. SBKJ is not a defence contractor, holds no AUKUS or partner-jurisdiction security clearance, and does not bid for cleared defence packages. SBKJ’s role in the AUKUS infrastructure conversation is the upstream supply of duct fabrication machinery to the cleared fabricators who deliver the work.
What SBKJ supplies for AUKUS-relevant work
The SBKJ machine catalogue that is most relevant to AUKUS-related duct fabrication is the SBAL-V stainless duct line, configured for 316L coil with integrated TIG seam welding, sealed-seam Class A capability to AS/NZS 4254, security mesh integration handling, and the duct-tagging and traceability option. The line is supplied with full CE certification, ISO 9001-certified manufacturing, full operator and maintenance training delivered in English from the SBKJ Australia office, and a long-term parts continuity commitment (SBKJ continues to support machines installed more than two decades ago). For paint-shop and sandblasting extraction duct, SBKJ’s heavier-gauge duct lines and abrasion-rated tooling are available. For supporting buildings and administration estate, the standard SBKJ duct catalogue applies.
How SBKJ engages
SBKJ engages with cleared fabricators on a normal commercial basis. The engagement model is a technical conversation about the duct types, gauges, materials and volumes required, followed by a machine configuration recommendation, a Factory Acceptance Test against the agreed configuration, shipping, installation supervision by SBKJ engineers on the fabricator’s site, operator training, and the long-term after-sales relationship. The cleared fabricator carries the security framework around their site and personnel; SBKJ’s installation engineers comply with the fabricator’s site induction and security access regime.
What SBKJ does not supply
SBKJ does not supply duct (we supply the machines that make the duct), does not supply cleared defence services, does not handle ITAR-controlled technical data, and does not contract directly into Australian Submarine Agency packages or partner-jurisdiction defence packages. SBKJ does not assert in any quotation, tender response or marketing material that the company holds AUKUS clearance.
Section 12 — A reference checklist
The following checklist condenses the conversation above into the questions a mechanical services consultant or duct fabricator might walk through before committing to a duct package on an AUKUS-relevant project. It is a public-domain summary; the controlling document is the project specification.
- Standards stack. Confirm DEF(AUST)10120 as the duct construction baseline, with AS 1668.2, AS/NZS 4254 and the project Functional Performance Specification overlaid. Identify NAVSEA, JSP 318 and DefStan references at the interoperability interfaces.
- Corrosivity envelope. Map every duct zone to its ISO 9223 category. Confirm C5-M at all exterior and shoreline locations; confirm C4 or C3 only inside fully sealed climate-controlled interior zones.
- Material set. Specify 316L stainless steel for all C5-M duct, cleanroom duct and security-boundary duct. Reserve galvanised and aluminium for permitted interior cases.
- Seam construction. Continuous TIG-welded longitudinal seams on stainless duct, passivated at the weld zone. Avoid mechanical lock-form seams in the C5-M envelope.
- Joint construction. Bolted and gasketed at sections; welded at security boundaries. Stainless fasteners and chloride-resistant gaskets throughout the C5-M envelope.
- Security overlays. Coordinate SCIF, TEMPEST, anti-contraband cross-sections, security mesh, acoustic baffles and air-gap construction with the cleared security consultant at shop-drawing stage.
- Cleanroom envelope. Identify ISO 14644 Class 7 spaces (combat-system integration rooms) early. Coordinate duct material, HEPA module layout, and pressure cascades with the cleanroom subcontractor.
- Welding fume capture. Provide source-capture at each welding station and hall-level dilution to AS 1668.2. Size the extraction duct for the contaminant load and the cleaning regime.
- Sandblasting and paint. Provide dedicated extraction with abrasion-rated duct for sandblasting; NFPA 33 or equivalent paint-shop ventilation with VOC capture and (where required) thermal or catalytic abatement.
- Redundancy. N+1 minimum on AHUs, fans and chillers; N+2 on combat-system and classified-storage spaces. Cross-link duct trains for single-failure tolerance.
- Continuous duty. Select components for continuous duty; specify planned maintenance windows that do not interrupt service to critical spaces.
- Documentation. Plan the handover dossier: mill certificates, WPS, welder records, inspection records, passivation reports, leakage tests, air-balance commissioning data.
- Fabrication shop. Separate stainless and carbon-steel workstations; dedicated stainless line with TIG seam welder; passivation bay; security mesh integration capability; data capture into the fabricator’s quality-management system.
- Cleared supply chain. Identify the security clearance holder at each tier of the supply chain. Ensure tender responses do not over-claim clearance held downstream by the machinery supplier or the steel mill.
Section 13 — Cross-references and further reading
Several SBKJ insights articles cover adjacent topics in more detail. For the general marine and offshore HVAC duct conversation, see the Marine & Offshore HVAC Duct Guide. For the welding methods used in stainless duct fabrication, see the welding methods reference. For the Australian ventilation code, see the AS 1668.2 reference. For SBKJ’s defence-industry positioning, see the defence industry page and the marine industry page.
Talk to an SBKJ engineer about a stainless duct line for naval and defence work →
FAQ
Which Australian standard governs ductwork construction for defence projects?
DEF(AUST)10120 is the Australian Defence ductwork construction standard most frequently cited on naval and defence-estate projects, applied with AS 1668.2 for mechanical ventilation, AS/NZS 4254 for duct construction, and the Defence Estate Management Manual (DEMM) for facility delivery. For AUKUS-classified spaces, NAVSEA and JSP 318 layer over the Australian baseline.
What duct material is required for exterior dockyard installations?
Coastal dockyards at Henderson, Osborne, Garden Island and HMAS Stirling sit in ISO 9223 corrosivity category C5-M. Exterior, plant-room and splash-zone duct should be fabricated from 316L stainless steel as a minimum, with TIG-welded longitudinal seams, passivated finish and gasketed joints to AS/NZS 4254. Galvanised steel is unsuitable for the C5-M envelope and is generally rejected on defence asset specifications.
What is a SCIF and why does its ductwork need to be different?
A Sensitive Compartmented Information Facility is a hardened room used to process classified material. The duct must defeat covert intrusion, acoustic leakage and emanations egress. Typical requirements include 96 mm or smaller anti-contraband cross-sections at penetrations, tamper-resistant grilles, security mesh inserts, acoustic baffles and continuous welded seams. SCIF duct is fabricated by a contractor holding the appropriate clearance.
Does SBKJ hold AUKUS security clearance?
No. SBKJ is a HVAC duct fabrication machinery supplier, not a cleared defence contractor. SBKJ machines are sold to defence-cleared fabricators and main contractors who hold the relevant Australian, United Kingdom or United States security clearances. SBKJ supplies the duct line, security tooling options and stainless seam-welding capability — the cleared fabricator runs the work under their own security framework, ITAR controls and personnel vetting.
Which Australian dockyards are part of the AUKUS submarine programme?
The principal sites are the Henderson Defence Precinct in Western Australia (the announced AUKUS submarine construction yard from the 2030s), HMAS Stirling at Garden Island West WA (Virginia-class rotational hosting from 2027), Osborne Naval Shipyard in South Australia (Hunter-class frigate and broader naval shipbuilding), Garden Island East in Sydney (HMAS Kuttabul fleet base and Captain Cook Graving Dock), and Williamstown Dockyard in Victoria (heritage shipyard).
