Why TBM tunnel construction HVAC is the most demanding life-safety scope in Australian civil engineering
HVAC engineers walking onto their first TBM tunnel construction project tend to underestimate the consequence. A commercial office tower in the Sydney CBD has a defined building envelope, a fixed mechanical plant room, a predictable air change rate and a 24-month tender-to-handover cycle that finishes with a smooth occupancy certificate. A TBM tunnel under construction has none of that. The tunnel is being created in real time, advancing several metres per day from a launch shaft toward a receiving shaft that may be five to ten kilometres away. The atmosphere at the face shifts hour by hour as the cutterhead encounters different geological strata — Sydney Hawkesbury sandstone with quartz silica, Wianamatta shale with sulphide minerals, Victorian basalt with feldspar dust, soft Brisbane sediments with groundwater inflow, hard Snowy granitic gneiss with crystalline silica. The diesel load on the back-up gantry, the muck haulage and the supply fleet ranges from a few megawatts on a small drive to fifteen or twenty megawatts on a multi-TBM mega-project. The crew at the working face are in a confined space throughout the entire length of the drive, with the nearest exit being either the launch shaft they came in through or the receiving shaft that has not yet been broken through. Every breath of air they take has travelled through the lay-flat ducting from the surface fan, past every metre of the TBM and its supply chain, before it arrives at the face. The ventilation engineer is the person responsible for keeping that breath safe.
The scale of modern Australian TBM construction reinforces the responsibility. Sydney Metro West is currently the largest single tunnel construction project in Australia, with the Acciona-Lendlease-Samsung C&T JV operating multiple Herrenknecht TBMs across a twin-tunnel alignment from Westmead through Parramatta, Sydney Olympic Park and on to the Bays. Cross River Rail in Brisbane is being delivered by the PULSE JV (CPB, UGL, John Holland) with TBM tunnels under the Brisbane CBD and the Brisbane River. Melbourne Metro Tunnel is in operating commissioning following the Cross Yarra Partnership (Lendlease, John Holland, Bouygues) TBM drives under the CBD. Snowy 2.0 by the Future Generation JV (Webuild, Clough, Lane Construction) is the largest pumped-hydro civil construction project in the Southern Hemisphere, with multiple TBMs driving headrace and tailrace tunnels through the Snowy Mountains. WestConnex M4M5 Link, M6 Stage 1, Westgate Tunnel, Western Harbour Tunnel and Beaches Link, North East Link NEL, and Forrestfield-Airport Link Perth are all active TBM projects across the eastern and western seaboards. Every one of those projects has an HVAC duct package running into the millions of dollars and an engineering scope that demands heavy-gauge spiral, heavy-gauge rectangular, 304 stainless welded plenum and field repair welding capacity.
The four engineering questions that TBM tunnel construction HVAC has to answer at once are familiar to anyone who has worked underground mining ventilation, but the answers are different. The first is dilution of diesel particulate matter (DPM) — the same Group 1 carcinogen at the same Safe Work Australia 0.1 mg/m³ EC TWA exposure standard, but at a higher concentration because the tunnel cross-section is small relative to the diesel load and the supply path is long. The second is dilution of respirable crystalline silica (RCS) — at the 0.05 mg/m³ TWA limit recently halved following the silicosis resurgence — with the particular Australian flavour that comes from boring through Hawkesbury sandstone in Sydney (high quartz content), Wianamatta shale (lower quartz but with sulphide minerals), Victorian basalt (lower quartz but with feldspar dust) and Snowy granitic gneiss (very high quartz). The third is hazardous area classification — where Australian tunnels diverge from many international projects in that the Sydney Basin contains pyrite-bearing sandstone strata that can release hydrogen sulphide and flammable gas under oxidation, the QLD coalfields contain methane-bearing strata that put parts of a tunnel into Zone 1 for methane, and every diesel handling station and fuel storage on the project is classified Zone 1 in its own right. The fourth is fire and life safety — where the consequence of a fire in a TBM under construction, with crew at the face several kilometres from the nearest exit, is catastrophic, and the fire engineering scope is at the highest stake in Australian civil construction.
This guide walks an HVAC contractor, tunnel ventilation engineer or duct fabricator from TBM type selection through to the Tier 1 JV's project handover, with reference to the Australian standards (AS 1668.2 mechanical ventilation, AS 4254 ductwork, AS 1530.4 fire-rated, AS 2865 confined spaces, AS 1746 air monitoring, AS/NZS 60079 hazardous areas, AS 1940 flammable liquids, AS 4036 and AS 4037 boiler and pressure vessel for TBM cooling water and lubrication, AS 1657 platforms, AS 1851 fire damper, AS 1742 traffic signage, AS 3580 boundary, AS 3957 dust hazard, AS 4801 OHS, AS 5601 LPG, AS/NZS 1170.2 structural for the concrete batching tower), the international references (NFPA 660 combustible dust where explosive ground or coal seam is encountered, NFPA 86 industrial furnace for TBM auxiliary heating, ITA Working Group 5 Health and Safety in Works, AusIMM and ATS guidance), the state regulations (NSW Mine Safety Act 2013 and WorkCover NSW, VIC Mineral Resources Sustainable Development Act 1990 and Worksafe Victoria, QLD Coal Mining Safety and Health Act 1999 and Mining and Quarrying Safety and Health Act 1999, WA Mines Safety and Inspection Act 1994) and Safe Work Australia workplace exposure standards. It covers project examples and operator names from Sydney Metro West through to Forrestfield-Airport Link, and it specifies the SBKJ machine portfolio that an Australian fabricator should be running to support a TBM tunnel HVAC duct package.
The TBM types and what each one demands of HVAC
The first decision in any TBM tunnel construction HVAC scope is to fix the TBM type, because the cutterhead chamber atmosphere, the back-up gantry equipment, the muck handling and the working face conditions change radically across types. Australian TBM projects run four major type families, each with a characteristic HVAC profile.
Earth Pressure Balance (EPB) TBM — Sydney Metro and Cross River Rail urban tunnels
Earth Pressure Balance TBM is the dominant TBM type for Australian urban rail and motorway tunnels in mixed soft-ground geology. Sydney Metro Northwest, Sydney Metro City and Southwest, Sydney Metro West, Cross River Rail Brisbane, Melbourne Metro Tunnel and WestConnex M4M5 Link have all used EPB machines from Herrenknecht. The EPB machine works by maintaining a pressurised earth paste in the cutterhead chamber that holds back the tunnel face during boring — the muck excavated by the cutterhead is mixed with foam, polymer and sometimes bentonite to create a paste-like consistency that supports the face. A screw conveyor at the bottom of the cutterhead chamber extracts the paste at a controlled rate to maintain face support pressure, with the extracted muck transferred onto a back-up gantry conveyor for haulage to the launch shaft.
EPB HVAC has three distinctive features. First, the cutterhead chamber is sealed against the tunnel face during boring — there is no through-ventilation from the chamber to the tunnel atmosphere, only the muck extraction through the screw conveyor. Minor extract is required to handle gases evolved from the paste (CO2 from any cement-based ground treatment, residual diesel exhaust if foam pumping is diesel-driven, occasional methane intercept in coal-seam ground). For combustible ground, CO2 or nitrogen inertion of the cutterhead chamber may be required to keep the methane below LEL during intervention. Second, the back-up gantry is densely populated with electric drive motors, hydraulic power packs, grouting equipment, segment erector hydraulics, conveyor systems and electrical cabinets — heat load on the gantry can run 500 kilowatts to 2 megawatts and the extract duct must clear this through the gantry roof to the tunnel ceiling void. Third, the diesel load behind the gantry — muck haulage trains, supply vehicles, mobile lighting — drives the face ventilation duty back through the tunnel toward the launch shaft.
Slurry TBM Mixshield STS — Lower Western Sydney, North East Link, Forrestfield-Airport Link
Slurry TBM (Herrenknecht Mixshield STS) is the alternative TBM type for soft-ground tunnelling, used where the ground is too watery or too unstable for the EPB paste approach to work. Forrestfield-Airport Link Perth (SI-NRW JV — Salini Impregilo, NRW Holdings) used slurry TBMs for the dive structure under groundwater. North East Link NEL Victoria is using slurry Mixshield TBMs for the M80 to Eastern Freeway connection. Lower Western Sydney has slurry TBMs in the planning. The slurry TBM works by maintaining a pressurised bentonite slurry in the cutterhead chamber that holds back the tunnel face — the muck excavated by the cutterhead mixes with the slurry and is pumped back to a surface separation plant where the muck is removed and the cleaned slurry is recycled to the TBM.
Slurry TBM HVAC has the same characteristic of a sealed cutterhead chamber as the EPB machine, but the cutterhead chamber is filled with bentonite slurry rather than earth paste. The chamber atmosphere management is via the slurry chemistry rather than via direct ventilation. The back-up gantry HVAC scope is similar to the EPB machine. The distinctive addition is the bentonite slurry plant at the launch shaft surface — a separation plant where the muck is screened, hydrocycloned and pressed to remove the bentonite for recycling. The slurry plant generates minor dust at the screen station, water mist at the hydrocyclone outlet, and a low concentration of bentonite aerosol throughout. HVAC scope is minor extract through standard galvanised duct.
Open-mode hard rock TBM — Snowy 2.0 historic Robbins, SELI, Herrenknecht
Open-mode hard rock TBM is the TBM type for competent rock tunnelling where the face does not require active support. Snowy 2.0 has used a mix of TBM types across the project's various headrace and tailrace drives — historically Robbins (US), SELI Overseas (Italian) and Hitachi Zosen (Japanese) machines, with current works also involving Herrenknecht. Open-mode hard rock TBM has an unsealed cutterhead chamber that opens directly into the tunnel atmosphere, with the muck excavated by the cutterhead falling onto a conveyor that carries it back through the gantry to the launch shaft or to a vertical conveyor.
Open-mode HVAC is the most demanding of the TBM types because the cutterhead chamber atmosphere is the tunnel atmosphere — dust generated at the cutterhead loads directly into the tunnel ventilation circuit, and the face ventilation forcing fan duty has to handle the dust dilution as well as the diesel dilution and the heat dilution. Typical face ventilation duty on a Snowy 2.0 open-mode TBM is 30 to 50 cubic metres per second through 2,000 mm lay-flat ducting on the supply side, with the return air running back past the gantry, the conveyor and the supply chain to the launch shaft.
Single-shield and double-shield TBM — Snowy 2.0 and similar
Single-shield and double-shield TBMs are variants on the hard rock TBM family, with a shield extending behind the cutterhead to provide structural support to the tunnel during segment erection. Snowy 2.0 has used double-shield TBMs from Herrenknecht for some of the headrace and tailrace drives. HVAC scope is similar to the open-mode hard rock TBM with the addition of segment erector station HVAC inside the shield.
The TBM operator cab — the most critical HVAC envelope on the project
The TBM operator cab is the climate-controlled enclosure on the back-up gantry where the TBM operator sits during boring operations. The operator drives the cutterhead, monitors the face support pressure, controls the muck extraction rate, oversees the segment erection sequence, and is the principal interface between the TBM control system and the human operator. The cab sits on the gantry for the entire 12 to 36 month boring period of the drive and is occupied 24 hours a day during the tunnel construction phase. The HVAC envelope of the cab is the most critical single piece of HVAC engineering on the TBM, because the operator's ability to safely drive the machine depends on a stable, clean, well-monitored breathing atmosphere.
Cab climate control
Modern TBM operator cab climate is controlled at 18 to 22 degrees C dry bulb with 40 to 60% relative humidity, achieved by a dedicated cab air conditioning unit (typically 5 to 15 kilowatt cooling capacity, with reverse-cycle heating) installed in or adjacent to the cab. The cab cooling load is dominated by the heat gain through the cab walls from the surrounding gantry equipment (typically 1 to 3 kilowatts) and the metabolic load of the occupants (100 to 250 watts per person, 1 to 3 occupants typical). The air conditioning unit recirculates cab air through a cooling coil and fan, with fresh air make-up drawn from the surface ventilation supply through a HEPA H10 filter to remove tunnel dust before the air enters the cab. The cooling coil and fan plenum is in 304 stainless welded construction, fabricated on the SBAL-V auto duct line in stainless configuration paired with the SB-ZF1500 longitudinal stitchwelder.
HEPA H10 filtration
The fresh air make-up to the cab passes through a HEPA H10 filter to remove tunnel dust. H10 is a high-efficiency particulate air filter classified per ISO 29463 (or the older EN 1822 standard) at 85% efficiency against 0.3 micrometre particles. The filter removes respirable dust (including RCS), diesel particulate matter and aerosolised cement from the supply air before it enters the cab breathing zone. Filter loading is monitored by differential pressure across the filter element, with replacement triggered at the design pressure rise (typically 250 Pa above clean filter pressure).
Gas sensors
The cab supply air and the cab return air carry continuous gas sensors for carbon monoxide (CO), carbon dioxide (CO2) and nitrogen dioxide (NO2). The sensors trigger alarm at the Safe Work Australia workplace exposure limits — CO at 30 ppm TWA, CO2 at 5000 ppm TWA and 30000 ppm STEL, NO2 at 5 ppm STEL. Alarm signal goes to the cab dashboard and to the TBM control room, with the operator able to trigger a manual evacuation procedure if the alarm condition persists. The gas sensors are also used as part of the confined space air monitoring scope under AS 1746.
Positive pressurisation +30 Pa
The cab is positively pressurised at +30 Pa relative to the surrounding gantry atmosphere. The positive pressure creates a continuous outward leakage through the cab door seals and any minor envelope gaps, preventing infiltration of contaminated outside air. The pressure differential is maintained by the fresh air make-up fan and verified by a differential pressure indicator visible to the operator.
304 stainless internal duct
The internal duct distribution inside the cab — from the air conditioning unit to the supply registers and from the return registers back to the unit — is in 304 stainless welded construction. Why 304 stainless rather than galvanised? The cab sits in the harsh tunnel atmosphere for the entire 12 to 36 month drive, and humidity, dust ingress around the door seals and condensate from the air conditioning cooling coil all attack galvanised steel. The cab is also a critical safety envelope where the integrity standard is high. 304 stainless throughout the cab internal duct distribution is the modern Australian specification on every recent project (Sydney Metro West, Cross River Rail, Melbourne Metro, Snowy 2.0, North East Link). SBKJ recommends the SBAL-V auto duct line configured for 304 stainless paired with the SB-ZF1500 longitudinal stitchwelder for the welded plenum sections of the TBM operator cab HVAC.
The TBM gantry crew compartment — the home of the tunnel crew
The TBM gantry crew compartment is a climate-controlled enclosure on the back-up gantry, typically 15 to 50 metres behind the cutterhead, where the tunnel crew rest between active tasks, take meal breaks, complete shift handover paperwork, and shelter during incident response. The compartment is occupied 24 hours a day with typically 4 to 10 crew at any one time. The HVAC envelope is similar to the operator cab but larger in volume and ventilation duty.
Climate control 18 to 22 degrees C
Crew compartment climate is controlled at 18 to 22 degrees C dry bulb with 40 to 60% relative humidity, achieved by a dedicated air conditioning unit (typically 15 to 30 kilowatt cooling capacity, with reverse-cycle heating). The cooling load is dominated by the metabolic load of the crew (1 to 3 kilowatts typical) and the heat gain through the compartment walls from the surrounding gantry equipment.
HEPA H10 filtration and gas sensors
Fresh air make-up to the compartment passes through a HEPA H10 filter on the same specification as the cab. Gas sensors monitor CO, CO2 and methane (CH4) where the tunnel alignment crosses coal-seam or gas-bearing strata. Methane sensors alarm at 1.25% TWA and trigger withdrawal at 2% under the relevant state mining or construction regulation.
Positive pressurisation +20 Pa
The compartment is positively pressurised at +20 Pa relative to the gantry atmosphere — slightly lower than the operator cab because the larger volume and higher fresh air make-up flow allows the same outward leakage at a lower differential. The differential pressure is monitored continuously.
304 stainless internal duct
The internal duct distribution inside the compartment is in 304 stainless welded construction for the same reasons as the operator cab. The compartment internal HVAC is fabricated on the SBAL-V in 304 stainless paired with the SB-ZF1500 stitchwelder.
The TBM segment erector operator station
The TBM segment erector operator station is a climate-controlled position on the back-up gantry where the operator drives the segment erector — the hydraulic manipulator that lifts each precast concrete tunnel segment from the segment storage on the gantry and installs it in the tunnel lining ring behind the cutterhead. The station is occupied during the segment erection cycle, which runs continuously during boring with each ring (typically 5 to 8 segments) taking 30 to 60 minutes to erect.
The erector station HVAC scope is similar to the operator cab in principle but smaller in volume — typically a single-occupant cabin with a 3 to 5 kilowatt air conditioning unit, HEPA H10 fresh air filtration, gas sensors and positive pressurisation. Internal duct is 304 stainless welded construction fabricated on the SBAL-V in stainless paired with the SB-ZF1500 stitchwelder.
Tunnel face ventilation — the forcing-fan system through lay-flat ducting
Tunnel face ventilation is the universal solution for delivering fresh air to the working face of an Australian TBM drive. The system runs from a primary fan at the surface (or at the portal in a portal-launched tunnel) through lay-flat ducting along the tunnel to the working face, with the spent return air exhausting through the tunnel itself back past the back-up gantry, the launch shaft and out through the portal or up the launch shaft.
Primary face ventilation fan duty
The primary face ventilation fan duty depends on the tunnel cross-section, the diesel load on the back-up gantry and the muck haulage, and the length of the drive. Typical face duty is 5 to 50 cubic metres per second at 1,500 to 4,500 Pa static pressure. Small drives — Forrestfield-Airport Link dive structure, micro-tunnelling pipe jacking, tunnel decline access — may run at the lower end of 5 to 15 cubic metres per second. Mid-range drives — Sydney Metro and Cross River Rail urban rail tunnels — run 15 to 30 cubic metres per second. Large drives — Snowy 2.0 headrace tunnels, WestConnex motorway tunnels, Melbourne Metro Tunnel — run 30 to 50 cubic metres per second per drive, with multiple drives operating concurrently on a mega-project.
Lay-flat ducting
Lay-flat ducting is positive-pressure flexible tunnel ventilation tubing in a PVC-coated polyester fabric construction with a reinforcing spiral wire for collapsing-resistance under negative pressure during fan trip. Specialist manufacturers supplying Australian projects include Sirroco Aerolite, SKF, Schauenburg, Protan, AireSpring and others. The duct is supplied in 100 to 200 metre rolls and connected end-to-end through the tunnel as the drive advances, suspended from the tunnel ceiling by purpose-designed clamp systems. Diameter ranges from 1,000 mm on small drives to 2,000 mm on the largest drives.
Lay-flat is positive-pressure only — it cannot be used on an extraction (negative-pressure) duty because the fabric construction collapses under negative pressure. The return air on a TBM tunnel runs back through the tunnel itself rather than through a dedicated return duct, with the bored tunnel acting as the return airway.
Rigid duct connections at the fan transition
The connection from the primary fan to the lay-flat duct is via a transition piece — a rigid round-to-flexible transition with a clamping band or strap. The transition piece is rigid galvanised spiral duct fabricated on the SBTF spiral tubeformer. For 2,000 mm primary fan duct on big projects (Sydney Metro West, Snowy 2.0, Cross River Rail, North East Link), SBKJ supplies the SBTF-2020 spiral tubeformer which fabricates round duct from 200 mm up to 2,000 mm diameter in heavy-gauge galvanised construction. The SBFB-1500 spiral fitting machine fabricates the bell-mouth inlets, transitions and Y-pieces.
Booster fans on long drives
On long drives — typical Sydney Metro West single drives are five to ten kilometres — the friction loss through the lay-flat duct becomes the dominant fan duty contributor. A 2,000 mm lay-flat duct at 30 cubic metres per second running 5 kilometres has approximately 3,500 to 4,500 Pa of friction loss depending on the duct surface roughness. Adding a single booster fan in line at the midpoint reduces the total fan power and improves the system efficiency. Booster fan locations are typically at the back-up gantry tail and at intermediate cross-passages.
Tunnel decline ventilation — diesel exhaust dilution
The tunnel decline is the truck access tunnel from surface down to the working level on a TBM project that uses a decline access for muck haulage and supply. Westgate Tunnel, North East Link and some Snowy 2.0 drives use decline access alongside or instead of shaft access. Decline ventilation is dominated by diesel exhaust from the haul truck fleet — a 60 tonne haul truck running on a Caterpillar 3508 engine at 600 kilowatts produces enough DPM that the dilution airflow required up the decline runs to 30 to 50 cubic metres per second per truck. The decline HVAC duct sits in the decline brow above the truck running gear, typically 1,500 to 2,000 mm round galvanised duct fabricated on the SBTF-2020 spiral tubeformer.
Engineering support TBM service tunnel — secondary ventilation
The engineering support TBM service tunnel is the parallel utility tunnel running alongside the main bored tunnel on some Australian projects, carrying the power supply, ventilation supply, water supply, slurry pipework and communications cabling. Secondary ventilation in the service tunnel keeps the utility equipment and the maintenance crew safe — typical duty is 5 to 15 cubic metres per second through 800 to 1,200 mm rigid duct or smaller lay-flat sections.
Shaft sinking — Snowy 2.0, Sydney Metro West, Marinus Link, Iron Cove
Shaft sinking is the construction of the vertical access shaft that serves the TBM launch and receiving operation, the permanent ventilation shaft for the operating tunnel, or the standalone vertical shaft for pumped hydro power station projects. Shaft sinking is the most concentrated piece of confined-space hazardous-area work in the entire tunnel construction scope.
Major Australian shaft sinking projects
Major Australian shaft sinking projects current and recent:
- Snowy 2.0 Tantangara and Talbingo shafts — Future Generation JV (Webuild, Clough, Lane Construction). Multiple deep shafts for the pumped hydro power station underground works.
- Lower Western Sydney tunnel project shafts — planning stage.
- Marinus Link — undersea HVDC interconnector between Tasmania and Victoria with shaft works at landfall.
- Iron Cove shaft — Sydney Metro West shaft site.
- Sydney Metro West shaft sites — Westmead, Parramatta, Sydney Olympic Park, North Strathfield, the Bays.
- Western Harbour Tunnel and Beaches Link shafts — ACCIONA, Ghella, CPB.
- M6 Stage 1 Sydney shafts — Acciona, Bouygues.
- Cross River Rail Brisbane shafts — PULSE JV.
Shaft sinking ventilation duty
Typical shaft ventilation duty is 30 to 100 cubic metres per second of fresh air supply through 1,000 to 1,800 mm rigid duct on the shaft wall, with deeper or larger-diameter shafts running higher duties. The supply duct is mounted on the shaft wall with purpose-designed brackets and grows in length as the shaft sinks. Spent return air exits through the shaft itself, with the shaft acting as the return airway.
Hazardous area classification — Zone 2 below grade by default
Shaft sinking ventilation is classified Zone 2 hazardous area below grade by default because the shaft atmosphere can accumulate diesel exhaust from the shaft sinking equipment, dust from the shaft excavation, and any naturally occurring gases — methane from coal-bearing strata, radon from uranium-bearing rock, hydrogen sulphide from sulphide ore zones. Coal-seam interception in the Snowy Mountains is unlikely but possible in some strata. Pyrite-bearing Sydney sandstone is classified Zone 2 for hydrogen sulphide and flammable gas from pyrite oxidation. Spark-resistant fans and IECEx Ex-d motors are mandatory throughout the shaft ventilation system.
Slipform concrete shaft and formwork
Many Australian shafts are constructed by slipform concrete — a continuous casting concrete formwork that advances as the shaft sinks, casting the concrete shaft lining in place. The slipform plant generates concrete spray aerosol and respirable crystalline silica during the casting and curing cycle. HVAC scope at the slipform plant is minor extract through galvanised duct, with the operator station inside a climate-controlled cabin similar to the TBM operator cab in principle.
Raising and the vertical conveyor
Some Australian shaft projects use a raise-bore approach for sinking — drilling a small pilot hole down from surface and then raising the shaft from below by reaming the pilot hole back upward. Other projects use a vertical conveyor for muck haulage during sinking, with the conveyor running up the shaft from the working level to the surface dump point.
SBKJ machine recommendation for shaft sinking
SBKJ supplies the heavy-gauge spiral tubeformer SBTF-2020 for the 2,000 mm shaft primary duct on the largest shaft projects. The SBAL-V auto duct line in galvanised G275 configuration fabricates the shaft fan house duct at surface. The SBFB-1500 spiral fitting machine fabricates the shaft duct transitions and bell-mouth inlets. For Zone 2 below grade, the spark-resistant fan and IECEx Ex-d motor specifications are sourced from specialist suppliers (Howden Australia, Korfmann Australia, Zitron) and SBKJ's duct ties into that specification at the rigid duct connection points.
Slipform concrete plant and tunnel lining
The slipform concrete plant is the continuous casting concrete formwork that creates the cast-in-place concrete tunnel lining on some Australian tunnel projects. The plant generates concrete spray aerosol, RCS during the casting and curing cycle, and alkali dust from Portland cement. HVAC scope at the slipform plant is minor extract for dust and aerosol through galvanised duct, with the operator station inside a climate-controlled cabin.
Shotcrete plant — the highest RCS exposure point in the entire project
Shotcrete plant produces sprayed cementitious tunnel support — wet-mix or dry-mix shotcrete delivered to the working face through pipework and applied by a shotcrete arm or by a nozzle operator. Shotcrete is the primary tunnel support method on many Australian projects, applied to the tunnel walls and roof immediately behind the cutterhead or behind the conventional drill-and-blast face. The shotcrete plant generates the highest concentration of respirable crystalline silica in the entire tunnel construction scope and the operator station is the highest single RCS exposure point in modern Australian construction.
Australian shotcrete suppliers
The major Australian shotcrete supplier and contractor list:
- Pylon Australia — concrete supplier and shotcrete contractor.
- Mapei Australia — chemical accelerator and shotcrete additive supplier.
- BASF Master Builders Solutions — chemical accelerator and additive supplier.
- Sika Australia — Swiss-headquartered chemical accelerator and additive supplier.
- CTS Cement — cement supplier.
- Holcim Concrete — RMC supplier.
- Adbri, Boral, Hanson — RMC suppliers.
Wet-mix and dry-mix shotcrete
Wet-mix shotcrete is mixed at the surface batching plant and pumped to the working face through pipework, with chemical accelerator added at the nozzle to flash-set the mix on contact with the tunnel wall. Dry-mix shotcrete carries the dry cement and aggregate to the nozzle through pipework with water added at the nozzle. Modern Australian tunnel projects use predominantly wet-mix shotcrete because the dust generation at the nozzle is significantly lower than the dry-mix process.
Respirable crystalline silica at 0.05 mg/m³ TWA
The shotcrete nozzle is the highest concentration of respirable crystalline silica in the entire tunnel construction scope. The aggregate in the shotcrete mix typically contains 20 to 60% quartz silica by mass depending on the source, and the spray atomisation at the nozzle generates fine respirable dust that includes the RCS fraction. The Safe Work Australia workplace exposure standard for RCS is 0.05 mg/m³ TWA — recently halved from the previous 0.1 mg/m³ standard following the silicosis resurgence — and the dilution airflow required to keep the nozzle operator below the standard is substantial.
Portland cement dust 10 mg/m³ inhalable irritant
The cement fraction of the shotcrete mix is Portland cement, and the dust generated at the spray contains alkali cement aerosol. The Safe Work Australia workplace exposure standard for Portland cement dust is 10 mg/m³ inhalable as an irritant — well above the typical RCS limit but still requiring ventilation engineering.
Chemical accelerator aerosol
Modern wet-mix shotcrete uses chemical accelerators based on silicate, aluminate or amine chemistry to flash-set the mix on contact with the tunnel wall. The accelerator is injected at the nozzle and a fraction of the accelerator becomes airborne as an aerosol. Mapei, BASF Master Builders, Sika and other suppliers publish exposure data on their accelerators that the HVAC engineer uses for the dilution calculation.
Cement aerosol
Cement aerosol from the shotcrete spray loads on the surface of any duct work it contacts. Galvanised steel duct is attacked by alkali cement washdown and chemical accelerator residue, with corrosion and surface degradation visible within months on a high-exposure duct section.
Shotcrete plant HVAC duct material — 304 stainless welded
The shotcrete plant HVAC duct is in 304 stainless welded construction throughout the concrete-spray-laden zones because of the alkali and chemical attack on galvanised steel. SBKJ recommends the SBAL-V auto duct line in 304 stainless configuration paired with the SB-ZF1500 longitudinal stitchwelder for the welded plenum sections of the shotcrete plant local exhaust duct. Round duct connections at the plant room fans are on the SBTF spiral tubeformer in stainless. Field installation welding of 304 stainless duct is on the SBLR-600 inverter welder with stainless filler wire (ER308L or ER316L per AS/NZS 1554.6 stainless welding qualification).
Shotcrete spraying operator station
The shotcrete spraying operator station is a climate-controlled cabin on the shotcrete arm or in a remote position from which the operator controls the nozzle. The cabin HVAC scope is similar to the TBM operator cab — climate control 18 to 22 degrees C, HEPA H10 filtration, gas sensors and positive pressurisation. Internal duct is 304 stainless welded construction.
Compressed-air station — tunnel pneumatic
The compressed-air station at the tunnel surface or in the launch shaft provides compressed air for tunnel pneumatic services — typically 5 to 10 bar gauge supplied to pneumatic tools, hyperbaric chamber compression, refuge chamber supply and emergency self-rescuer cylinder filling. The station is classified Zone 2 if the compressors are oil-lubricated (which is the standard for compressed-air tunnel work), with the Zone 2 designation reflecting the possibility of compressor oil mist in the air supply.
HVAC scope at the compressed-air station is general body ventilation through galvanised duct, with IECEx Ex-d in-line equipment for the Zone 2 designation. SBKJ recommends the SBAL-V auto duct line in galvanised G275 configuration for the compressed-air station ventilation, with the SBTF spiral tubeformer for the round connection sections.
Hyperbaric chamber — soft-ground intervention at Cross River Rail and Melbourne Metro
A hyperbaric chamber is the compressed-air work facility used for soft-ground intervention on a TBM cutterhead — where the cutterhead has to be entered for tool change or repair while the tunnel face is in unstable ground that is being held back by compressed air at the working face. The chamber pressurises the cutterhead chamber to typically 1 to 3 bar gauge above atmospheric, allowing crew to enter and work without the ground collapsing into the cutterhead. Hyperbaric interventions are a routine part of Earth Pressure Balance (EPB) TBM and slurry Mixshield TBM operations on Australian projects — Brisbane Cross River Rail and Melbourne Metro Tunnel have both used hyperbaric interventions for soft-ground tool changes.
Hyperbaric HVAC scope — medical grade
The HVAC scope on a hyperbaric chamber is medical-grade. The supply air is clean dry compressed air at the design working pressure, filtered to remove oil mist, water and particulates. Oxygen and CO2 monitoring is continuous, with the chamber atmosphere held at 19.5% to 23.5% oxygen and below 5000 ppm CO2 throughout the intervention. Temperature and humidity control are required to keep the chamber atmosphere within the working comfort range — typically 18 to 25 degrees C and 40 to 60% RH. Emergency depressurisation provisions allow the chamber to be returned to atmospheric pressure on a controlled schedule (decompression takes 30 minutes to several hours depending on the working pressure and exposure time) or in an emergency.
Hyperbaric chamber duct material — 304 stainless welded
Duct on a hyperbaric chamber is 304 stainless welded throughout because the chamber sits in the harsh tunnel atmosphere between interventions and the medical-grade air integrity standard demands stainless. SBKJ recommends the SBAL-V auto duct line in 304 stainless configuration paired with the SB-ZF1500 longitudinal stitchwelder for the hyperbaric chamber HVAC duct. The chamber acceptance test includes envelope integrity at design working pressure, supply air quality testing to the medical-grade specification, oxygen and CO2 monitoring calibration, and emergency depressurisation drill.
TBM emergency refuge chamber — between life and death
The TBM emergency refuge chamber is a sealed compartment on or near the TBM back-up gantry where the tunnel crew can shelter for typically 24 to 48 hours during a fire, gas event, water inrush or other entrapment emergency. Every Australian TBM project carries a refuge chamber on the back-up gantry and additional fixed refuge chambers along the tunnel at regular intervals as the drive lengthens. The chamber may sit unused for months between use and must work the first time it is needed.
Compressed air supply
The primary HVAC supply to a TBM refuge chamber is compressed air from the surface compressed-air reticulation system through the lay-flat or rigid supply line, with a fallback supply from stored cylinder packs inside the chamber for the event that the reticulation system has failed. The internal distribution duct from the supply manifold to the breathing zone is in 304 stainless welded construction, fabricated on the SBAL-V auto duct line in stainless configuration paired with the SB-ZF1500 longitudinal stitchwelder.
CO2 scrubbing — refer underground mine refuge
CO2 scrubbing inside the chamber is via lithium hydroxide (LiOH) cassettes or soda lime cassettes, with an internal recirculation fan moving chamber air through the scrubber media. The scrubber plenum and fan duct is in 304 stainless welded construction with welded inspection ports for cassette change-out. The scrubber duty calculation, oxygen supplementation calculation and chamber acceptance test follow the same engineering as the underground mine refuge chamber covered in the underground mine ventilation guide.
Oxygen supplementation and positive pressure
Oxygen supplementation is via cylinders of compressed oxygen inside the chamber, with a regulator and distribution manifold to the breathing zone. The chamber maintains a positive pressure differential of typically 100 to 250 Pa relative to the outside tunnel atmosphere.
Temperature control
The chamber internal temperature is controlled by a small recirculating air conditioning unit (typically 3 to 10 kilowatt cooling capacity). The cooling coil and fan plenum duct is in 304 stainless welded construction.
304 stainless welded throughout
The duct material for the TBM refuge chamber is 304 stainless welded construction throughout because the chamber may sit unused for months between use and the integrity standard at the moment crew need it is absolute. The cost premium of 304 stainless over galvanised is trivial in the context of the chamber as a whole and is non-negotiable in modern Australian TBM refuge chamber specifications. SBKJ recommends the SBAL-V configured for 304 stainless paired with the SB-ZF1500 longitudinal stitchwelder for the refuge chamber internal duct distribution and the CO2 scrubber plenum.
Grouting plant and bentonite slurry plant
The grouting plant supplies cementitious grout for cavity filling behind the precast concrete tunnel segments — typical grout is a cement-bentonite mix pumped through the grouting equipment on the back-up gantry to fill the annular gap between the segments and the surrounding ground. HVAC scope at the grouting plant is minor extract through galvanised duct.
The bentonite slurry plant on a slurry Mixshield TBM project is a larger HVAC scope. The plant is at the launch shaft surface, with the slurry pumped to the TBM through a dedicated pipeline. The plant generates minor dust at the bentonite handling station, water mist at the hydrocyclone separation outlet, and a low concentration of bentonite aerosol throughout. HVAC scope is minor extract through galvanised duct.
Construction water treatment plant
The construction water treatment plant handles groundwater dewatering inflow and process water from the TBM operation. A typical TBM operation uses 10 to 100 litres per second of process water for cooling, dust suppression, slurry mixing and concrete batching. The treatment plant removes suspended solids, neutralises pH, and may include flocculation, sedimentation and filtration steps before discharge to the storm water network or sewer per the EPA discharge approval.
HVAC scope at the water treatment plant is minor extract through galvanised duct, with the operator station inside a climate-controlled cabin.
TBM back-up gantry — heat extract on the trailing equipment
The TBM back-up gantry is the trailing equipment string behind the cutterhead, typically 15 to 100 metres long, carrying the grouting equipment, segment erector hydraulics, conveyor, ventilation supply, power reticulation, lighting and operator stations. The heat load on the gantry runs 500 kilowatts to 2 megawatts depending on the equipment density, and the extract duct runs through the gantry roof to the tunnel ceiling void or through a dedicated extract line back along the tunnel to the launch shaft.
The gantry heat extract HVAC scope is general body ventilation through galvanised duct on the gantry framework, with rectangular duct sections fabricated on the SBAL-V auto duct line. Round duct connections are on the SBTF spiral tubeformer. Field installation welding is on the SBLR-600 inverter welder.
TBM launch shaft and receiving shaft
The TBM launch shaft is the surface yard where the TBM is assembled at the start of the drive and lowered into position for tunnel boring. The receiving shaft is the corresponding yard at the breakthrough end where the TBM is recovered. Both yards are intensive construction sites for the duration of the drive, with crane operations, segment delivery and storage, muck handling, supply lay-down, office and amenity facilities.
HVAC scope at the launch and receiving shafts is similar to the general Tier 1 major-project construction scope covered in the Tier 1 construction guide — office and amenity ventilation through galvanised duct, kitchen exhaust, toilet ventilation, change-room ventilation, electrical room ventilation and so on.
Concrete precast segment casting yard
The concrete precast segment casting yard supplies the precast concrete tunnel segments that line the bored tunnel. Sydney Metro West Pacific Park yard produces over 7,000 segments for the project. Cross River Rail, Melbourne Metro Tunnel, Snowy 2.0 and other major projects all operate precast segment yards at scale.
Segment yard HVAC scope is covered in detail in the concrete precast manufacturing guide. The general specification is galvanised G275 duct for the casting hall ventilation, the curing kiln exhaust, the demoulding and finishing area, and the storage yard. SBKJ recommends the SBAL-V auto duct line in galvanised configuration for the casting hall.
Surface batching plant — Tier 1 contractor concrete
The Tier 1 contractor surface batching plant supplies concrete for the precast segment yard, the shotcrete plant, the slipform concrete shaft and tunnel lining, the cast-in-place concrete structures at the launch and receiving shafts, and the surface civil works. The batching plant is typically a dedicated facility at the construction yard with cement silos, aggregate bins, mixers, truck loadout and quality control facilities.
Batching plant HVAC scope is covered in the Tier 1 construction guide and the concrete precast guide. The general specification is galvanised G275 for the cement silo dust collector, the mixer hood extract, and the truck loadout dust extract. The batching plant tower is structurally designed to AS/NZS 1170.2.
Micro-tunnelling and pipe-jacking
Micro-tunnelling is the small-diameter tunnel construction method used for sewer, drainage and utility pipe installation under existing infrastructure where open-cut excavation is not practical. Pipe-jacking is the associated method where precast concrete pipe sections are jacked through the ground from a launch pit to a receiving pit. Bessac Australia is a French-origin specialist micro-tunnelling contractor active on Australian projects.
Micro-tunnelling HVAC scope is smaller than a TBM project but has the same principles. The micro-tunnel operator cab is climate-controlled. The face ventilation is delivered through lay-flat ducting of smaller diameter (typically 600 to 1,000 mm). The launch pit and receiving pit are confined spaces requiring AS 2865 air monitoring.
The operators — Tier 1 JVs on major Australian TBM projects
The Australian TBM construction sector is dominated by a relatively small group of Tier 1 JVs across the major projects. The HVAC duct designer and the fabricator must understand which JV they are bidding into to align the deliverables and the engineering interface.
Sydney Metro West
Lendlease, Acciona, Samsung C&T JV — the main works JV for the central package of Sydney Metro West, operating twin Herrenknecht TBMs through the urban alignment from Westmead to the Bays.
Sydney Metro Western Sydney Airport
Acciona, Bouygues, Bechtel — the main works JV for the Western Sydney Airport rail line including TBM tunnels under the airport infrastructure.
Sydney Metro Northwest (legacy completed)
Stadtler, John Holland, ID Engineering — the legacy TBM JV for the completed Sydney Metro Northwest line, now operating as Sydney Metro.
Sydney Metro City and Southwest
John Holland, CPB Contractors, Ghella (TBM Tunnels) — the TBM JV for the City and Southwest expansion linking Chatswood to Bankstown.
Cross River Rail Brisbane
PULSE (CPB, UGL, John Holland — main works) and Tunnels Brisbane Tunneller JV — the Cross River Rail TBM works under the Brisbane CBD and the Brisbane River.
Melbourne Metro Tunnel
Cross Yarra Partnership CYP (Lendlease, John Holland, Bouygues — main works) — the Melbourne Metro Tunnel TBM works, now in operating commissioning following completion of the drives.
Snowy 2.0
Future Generation FGJV (Webuild, Clough, Lane Construction) — the Snowy 2.0 main works JV operating multiple TBMs for the headrace, tailrace and underground power station works.
WestConnex M4M5 Link and M6 Stage 1
Acciona, Samsung, CPB, John Holland — the WestConnex motorway TBM works including the M4M5 Link and the M6 Stage 1.
Westgate Tunnel
CPB, John Holland — the Westgate Tunnel project under construction with TBM works under the Melbourne western suburbs.
Western Harbour Tunnel and Beaches Link
ACCIONA, Ghella, CPB — the Western Harbour Tunnel and Beaches Link motorway projects with TBM works under Sydney Harbour and the Northern Beaches alignment.
M6 Stage 1 Sydney
Acciona, Bouygues — the M6 Stage 1 motorway TBM works in Sydney's south.
North East Link NEL Victoria
Spark, Acciona, Webuild — the North East Link motorway TBM works connecting the M80 to the Eastern Freeway via slurry Mixshield TBMs.
Forrestfield-Airport Link Perth
SI-NRW JV (Salini Impregilo, NRW Holdings) — the Forrestfield-Airport Link rail TBM works using slurry Mixshield TBMs for the dive structure under groundwater.
Marinus Link
Macquarie Group, Hitachi consortium under investigation — the Tasmania-Victoria HVDC interconnector with shaft works at landfall.
Inland Rail Inland Tunnels
Inland Rail has not yet committed to TBM tunnels in the current scope but future stages may include TBM works.
TBM manufacturers — suppliers to Australian projects
The TBM machine supply for Australian projects is dominated by a small number of international manufacturers. The HVAC duct designer must engage with the manufacturer at the order stage to align the manufacturer's TBM cab, gantry crew compartment, main drive motor cooling and segment erector station HVAC scope with the project HVAC package.
Herrenknecht (German)
Herrenknecht is the dominant TBM supplier globally and to Australian projects. Sydney Metro, Cross River Rail, Snowy 2.0, WestConnex, Westgate, Melbourne Metro, M6 and North East Link have all used or are using Herrenknecht machines.
Robbins (US)
Robbins is the US-origin TBM supplier with historic supply to Snowy 2.0.
SELI Overseas (Italian)
SELI Overseas supplied original Snowy 2.0 TBMs.
Hitachi Zosen (Japanese)
Hitachi Zosen supplied Snowy 2.0 TBMs as a Japanese-origin supplier.
CREG
CREG has supplied TBMs to some Australian projects.
Tunnelling specialists — international and domestic
Beyond the Tier 1 JVs, Australian TBM projects engage tunnelling specialists who bring international experience to the local market.
International tunnelling specialists in Australia
- McConnell Dowell — NZ-based with TBM tunnel experience across ANZ.
- Bouygues Australia — French TBM specialist with experience across global tunnel projects.
- Ferrovial Australia — Spanish-origin construction major.
- Acciona Australia — Spanish-origin with TBM experience across global projects.
- Webuild Australia — Italian-origin (Salini Impregilo legacy) tunnelling specialist.
- John Holland Tunnelling — CIMIC subsidiary with deep Australian tunnelling experience.
- CPB Contractors — CIMIC subsidiary with Australian tunnelling and rail experience.
- Ghella — Italian tunnelling contractor.
- Doll Tunnelling — German tunnelling specialist.
- Bessac Australia — French micro-tunnelling specialist.
Industry bodies and reference institutions
- Australasian Tunnelling Society (ATS) — peak Australian tunnelling industry body and a sub-group of Engineers Australia. Publishes guidance notes on tunnel ventilation, fire and life safety, shaft sinking and TBM operations.
- Tunnelling Forum — Australian tunnel industry networking body.
- International Tunnelling Association (ITA) — global peak body. Working Group 5 publishes guidance on Health and Safety in Works, including tunnel ventilation, confined spaces and emergency preparedness.
- Civil Contractors Federation (CCF) — Australian civil construction industry body.
- Engineers Australia — Australian professional engineering body. The ATS is a sub-group of Engineers Australia.
- AusIMM Australian Institute of Mining and Metallurgy — peak mining and metallurgy professional body, with cross-over to tunnelling.
- AusRAIL — Australian rail industry body.
State construction and mining regulations
Every Australian state and territory has its own construction and mining safety regulation regime that overrides and extends the national WHS framework. TBM tunnel construction sits in both the construction and mining regulatory spaces depending on the project — civil construction regulations for the surface works and the urban rail tunnels, mining regulations where mining-style works are undertaken (Snowy 2.0 underground power station, deep shaft sinking).
New South Wales
NSW operates under the Work Health and Safety Act 2011 and the Work Health and Safety Regulations 2017 for civil construction, administered by SafeWork NSW (formerly WorkCover NSW). The Mine Safety Act 2013 and WHS Mining Regulations 2014 apply where mining-style works are undertaken. The Mining Design Guidelines MDG 12, MDG 16 and MDG 41 are referenced for the mining-style works.
Victoria
VIC operates under the Occupational Health and Safety Act 2004 for civil construction, administered by Worksafe Victoria. The Mineral Resources (Sustainable Development) Act 1990 applies for mining-style works.
Queensland
QLD operates under the Work Health and Safety Act 2011 for civil construction. The Coal Mining Safety and Health Act 1999 and the Mining and Quarrying Safety and Health Act 1999 apply for mining-style works, administered by Resources Safety and Health Queensland (RSHQ).
Western Australia
WA operates under the Work Health and Safety Act 2020 for civil construction, administered by WorkSafe WA. The Mines Safety and Inspection Act 1994 and the WHS (Mines) Regulations 2022 apply for mining-style works, administered by DEMIRS (Department of Energy, Mines, Industry Regulation and Safety).
Hazardous area dossier — what the duct fabricator delivers
Australian TBM tunnel construction projects require a hazardous area dossier covering every piece of in-line plant in the HVAC duct system that is destined for a Zone 1 or Zone 2 classified area. The duct fabricator's contribution to the dossier covers:
- Bonding test records. Continuity resistance between adjacent duct sections measured at less than 10 ohms, and continuity to earth at less than 10 ohms at every grounding take-off point.
- Surface treatment certificates. Anti-static surface treatment certification on galvanised duct destined for Zone 1 service.
- Material mill certificates. Mill certificates on 304 stainless duct destined for TBM operator cab, gantry crew compartment, refuge chamber, hyperbaric chamber and shotcrete plant.
- Weld inspector reports. AS/NZS 1554.6 stainless welding qualification records for the welder and the procedure on every welded section destined for fire-rated, stainless or high-integrity service.
- FAT records. Factory Acceptance Test records on first-of-type duct sections, witnessed by the principal contractor's engineering representative or by the project ventilation engineer.
SBKJ's machine portfolio supports the dossier requirements with built-in quality records. The SBAL-V auto duct line records the gauge, the geometry and the joint configuration of every duct section produced. The SBTF spiral tubeformer records the diameter, gauge, lock-seam pitch and length of every round duct produced. The SB-ZF1500 stitchwelder records the weld parameters and the inspector sign-off for every welded section produced.
SBKJ machine recommendation — by TBM tunnel construction application
The following machine recommendations cover the typical SBKJ portfolio for an Australian TBM tunnel construction HVAC duct fabrication shop. Each application has a primary machine and one or more secondary machines for fittings, accessories and field repair. The complete machine portfolio is documented on the SBKJ machine portfolio page with detailed specifications and capabilities.
TBM operator cab and gantry crew compartment (304 stainless welded)
- SBAL-V auto duct production line — primary machine configured for 304 stainless construction at the gauge required for the TBM operator cab and gantry crew compartment internal duct distribution. See the SBAL-V product page for full specifications.
- SB-ZF1500 longitudinal stitchwelder — primary machine for the welded plenum sections inside the cab and compartment envelope.
- SBLR-600 inverter welder — secondary machine for field installation welding with stainless filler wire (ER308L or ER316L per AS/NZS 1554.6).
Tunnel face ventilation — primary fan duct (heavy-gauge galvanised)
- SBTF-2020 spiral tubeformer — primary machine for 2,000 mm primary fan duct on big projects (Sydney Metro West, Snowy 2.0, Cross River Rail, North East Link).
- SBFB-1500 spiral fitting machine — primary machine for the lay-flat tunnel ventilation transitions and bell-mouth inlets.
- SBSF-1525 — primary machine for the spiral seam production on the round duct.
- SBPC1500 plasma cutter — secondary machine for plasma cutting of heavy-gauge plate for evasee transitions and silencer baffles.
Shaft sinking ventilation (heavy-gauge galvanised, Zone 2)
- SBTF-2020 spiral tubeformer — primary machine for 2,000 mm shaft primary duct.
- SBAL-V auto duct line — primary machine in galvanised G275 configuration for the shaft fan house duct at surface.
- SBFB-1500 — secondary machine for shaft duct transitions and bell-mouth inlets.
- Spark-resistant fan and IECEx Ex-d motor specifications — sourced from specialist suppliers (Howden Australia, Korfmann Australia, Zitron) for Zone 2 below grade.
Shotcrete plant (304 stainless welded)
- SBAL-V auto duct production line — primary machine configured for 304 stainless construction at the gauge required for the shotcrete plant local exhaust duct.
- SB-ZF1500 longitudinal stitchwelder — primary machine for the welded plenum sections of the shotcrete plant local exhaust duct.
- SBTF spiral tubeformer — secondary machine for round duct connections in 304 stainless.
- SBLR-600 inverter welder — secondary machine for field installation welding of stainless duct.
TBM emergency refuge chamber (304 stainless welded)
- SBAL-V auto duct production line — primary machine configured for 304 stainless construction at the gauge required for the refuge chamber internal duct distribution and the CO2 scrubber plenum. See the SBAL-V product page for the 304 stainless configuration details.
- SB-ZF1500 longitudinal stitchwelder — primary machine for the welded plenum sections inside the refuge chamber envelope.
- SBLR-600 inverter welder — secondary machine for field installation welding.
Hyperbaric chamber (304 stainless welded)
- SBAL-V auto duct production line — primary machine configured for 304 stainless construction for the hyperbaric chamber HVAC duct.
- SB-ZF1500 longitudinal stitchwelder — primary machine for the welded plenum sections inside the hyperbaric chamber.
General surface support and segment casting yard (galvanised G275)
- SBAL-V auto duct production line — primary machine configured for SBAL-V galvanised G275 for the general surface support scope and the concrete precast segment casting yard. See the SBAL-V vs SBAL-III comparison for the appropriate machine selection.
- SBTF spiral tubeformer (SBTF-1602 / SBTF-2020) — primary machine for round duct on the surface scope.
- SBFB-1500 spiral fitting machine — secondary machine for fittings on the surface scope.
- SBPC1500 plasma cutter — secondary machine for plate cutting.
Hazardous area service — coal seam methane Zone 1, pyrite Zone 2, diesel Zone 1
- Spark-resistant fans — typically aluminium impeller blades in a fibreglass-reinforced or stainless-steel casing, certified to AS/NZS 60079.1 (flameproof enclosures) and AS/NZS 60079.7 (increased safety).
- IECEx Ex-d ATEX motors — mandatory for coal seam methane Zone 1, pyrite-bearing Sydney sandstone Zone 2, and diesel exhaust Zone 2 service.
- Anti-static surface treatment on duct — specified at the order stage of the SBAL-V or SBTF production.
- Bonding straps between duct sections and earth-grounding at intervals — verified by continuity resistance test below 10 ohms.
Procurement timeline for a TBM tunnel construction HVAC duct package
TBM tunnel construction HVAC duct procurement typically runs 18 to 36 months from contract award to final delivery and commissioning, with the timeline driven by the TBM manufacturing schedule and the tunnel construction sequence rather than the duct fabrication schedule alone.
- Months 0–6 — Contract award and engineering coordination. Detailed shop drawing development, coordination with the Tier 1 JV engineering team and the TBM manufacturer (Herrenknecht, Robbins, Hitachi Zosen), sign-off on duct routing through the planned tunnel alignment, fire engineering basis lock-down, material specification confirmation (galvanised for surface, 304 stainless for confined-space refuge chamber, TBM operator cab, hyperbaric chamber and shotcrete plant), hazardous area classification confirmation under AS/NZS 60079.10.1.
- Months 6–12 — First-of-type and FAT. Manufacture of first-of-type duct sections including the 304 stainless welded plenum for refuge chambers, TBM operator cab, gantry crew compartment, hyperbaric chamber and shotcrete plant. Factory Acceptance Test witnessed by the principal contractor's engineering representative or by the project ventilation engineer. Sign-off on the welded duct assembly procedure for the stainless sections per AS/NZS 1554.6.
- Months 12–24 — Bulk fabrication. High-throughput fabrication of the bulk main and auxiliary duct on the SBAL-V auto duct line, the SBTF spiral tubeformer and the SB-ZF stitchwelder. Continuous QA witnessed at the fabricator, mill certificates collected on 304 stainless duct, weld maps documented for fire-rated and stainless sections.
- Months 18–30 — Staged delivery. Phased delivery aligned to TBM assembly progress and tunnel construction sequence. Surface scope (launch shaft yard, batching plant, precast segment yard, office and amenity) installed during launch shaft construction. TBM-mounted scope (operator cab, gantry crew compartment, segment erector station, refuge chamber, main drive motor cooling) installed at the TBM assembly area. Tunnel ventilation lay-flat connection points installed as the tunnel advances.
- Months 24–32 — Installation and commissioning. Duct installation, pressure and leakage testing per AS 4254 class C or D, primary face ventilation fan commissioning against design fan curve, TBM operator cab and gantry crew compartment positive pressurisation commissioning, refuge chamber acceptance test, hyperbaric chamber acceptance test where applicable, hazardous area dossier sign-off, fire damper integration test per AS 1851.
- Months 30–36 — Tier 1 JV handover. Final acceptance, as-built drawing handover, fan curves, leakage test certificates, refuge chamber and hyperbaric chamber acceptance certificates, hazardous area dossier, bonding test records. Tier 1 JV takes ongoing responsibility for the system during the tunnel construction phase and hands over to the operating asset owner at project completion.
Commissioning — fan curve verification, refuge chamber acceptance, hyperbaric chamber acceptance
TBM tunnel construction HVAC commissioning is a multi-stage process running over several months and culminating in the Tier 1 JV's project handover. The commissioning sequence ties back to the more general framework covered in the HVAC commissioning and air balancing guide, with specific additions for the TBM context.
The first stage is component commissioning — fan startup against design fan curve, damper actuation testing, sensor calibration, leakage testing of installed duct sections to AS 4254 class C or D, and verification of fail-safe positions on power loss and gas alarm signal. The second stage is sub-system commissioning — primary face ventilation fan curve verification on the installed lay-flat duct system, TBM operator cab and gantry crew compartment positive pressurisation verification, refuge chamber acceptance test (envelope integrity, CO2 scrubber duty, oxygen flow, internal temperature rise), hyperbaric chamber acceptance test where applicable (envelope integrity at design working pressure, supply air quality testing to medical-grade specification, oxygen and CO2 monitoring calibration, emergency depressurisation drill).
The third stage is integrated system testing — coordinated response to simulated gas alarm and fire alarm signals from the project SCADA, verification of withdrawal trigger response on methane 2% where coal-seam ground is intercepted, validation of pressure profile and air-flow direction across the full system. The Factory Acceptance Test on first-of-type duct is the project-controlled document that ties the on-site commissioning back to the fabrication baseline. SBKJ supports witnessed FAT on first-of-type duct as standard, with full documentation including weld procedure qualification records under AS/NZS 1554.6 for stainless welding, weld inspector reports, mill certificates for raw material and dimensional inspection records for every duct section.
How SBKJ supports TBM tunnel construction HVAC duct projects
SBKJ Group supplies the heavy-gauge duct fabrication machinery used by HVAC contractors and fabricators bidding into Australian TBM tunnel construction projects. The relationship typically runs through one of two routes — direct supply of fabrication machinery to a contractor with in-house duct manufacturing, or supply through a fabricator partner who is bidding into the project's HVAC duct package.
Our engineering team in Box Hill North VIC supports TBM tunnel construction duct projects in several ways: machine sizing for the project's specific duct material, gauge and pressure class; fabrication consultation including weld procedure development for 304 stainless sections destined for the TBM operator cab, gantry crew compartment, refuge chamber, hyperbaric chamber and shotcrete plant; FAT witnessing on machinery destined for TBM projects; and ongoing field service support during the project's fabrication and installation phases.
Our heavy-gauge machine portfolio covers round duct fabrication via the SBTF-2020 spiral tubeformer up to 2,000 mm diameter for primary face ventilation fan duct on big projects, the SBTF-1602 and SBTF-1500C for mid-range main and auxiliary duct, the SBFB-1500 spiral fitting machine for lay-flat tunnel ventilation transitions and bell-mouth inlets, the SBSF-1525 for spiral seam production, rectangular duct via the SBAL-V auto duct line in SBAL-V galvanised G275 for general surface support and segment casting yard service and in 304 stainless for confined-space refuge chamber, TBM operator cab and CO2 scrubber, welded duct via the SB-ZF1500 longitudinal stitchwelder for 304 stainless plenum sections, plasma cutting via the SBPC1500 and field welding via the SBLR-600 inverter welder. Spark-resistant fans and IECEx Ex-d ATEX motors are mandatory for coal seam methane Zone 1, pyrite-bearing Sydney sandstone Zone 2 and diesel exhaust Zone 2 service.
For HVAC contractors and duct fabricators bidding into Australian TBM tunnel construction projects — whether the project sits with the Sydney Metro West Lendlease-Acciona-Samsung JV, the Cross River Rail PULSE JV, the Melbourne Metro Tunnel Cross Yarra Partnership, the Snowy 2.0 Future Generation JV, WestConnex, Westgate Tunnel, Western Harbour Tunnel and Beaches Link, North East Link, M6 Stage 1, Forrestfield-Airport Link or Marinus Link — the natural starting point is a conversation about scope. Duct quantities, material breakdown across galvanised and 304 stainless, fire-rated proportion, hazardous area zone classification, schedule and FAT requirements. From that scope we run a sizing exercise to confirm the right machine portfolio for the project. Browse the SBKJ machine portfolio or view the SBAL-V auto duct production line in detail, then go directly to contact to start the conversation. We typically reply within 12 hours from a senior engineer at the Box Hill North VIC engineering office, not a salesperson.
Related guides on SBKJ
This guide on TBM tunnel construction HVAC duct sits alongside several related references on the SBKJ insights library:
FAQ
What Australian standards and regulations apply to TBM tunnel construction HVAC duct?
The general framework is AS 1668.2 (mechanical ventilation), AS 4254 (ductwork), AS 1530.4 (fire-rated), AS 2865 (confined spaces — every TBM tunnel under construction is a confined space throughout), AS 1746 (confined space air monitoring) and AS/NZS 60079 (hazardous areas). Hazardous areas in tunnel construction include diesel handling stations (Zone 1), fuel storage (Zone 1 to AS 1940), blasting magazines (Zone 2), methane-bearing strata where coal seams or gas-bearing rock is intercepted (Zone 1), pyrite-bearing Sydney sandstone (Zone 2), and battery charging rooms (Zone 2 for hydrogen). State regulations: NSW Mine Safety Act 2013 and WorkCover NSW, VIC Mineral Resources Sustainable Development Act 1990 and Worksafe Victoria, QLD Coal Mining Safety and Health Act 1999 and Mining and Quarrying Safety and Health Act 1999, WA Mines Safety and Inspection Act 1994. Industry references: ITA Working Group 5, ATS guidance notes, MDG 12/16/41. Safe Work Australia exposure standards: DPM 0.1 mg/m³ EC TWA, RCS 0.05 mg/m³ TWA, methane 1.25% TWA / 5% LEL, CO 30 ppm, CO2 5000 TWA / 30000 STEL, oxygen 19.5% to 23.5%, H2S 10/15 STEL, NO2 5 STEL, NH3 25/35 STEL, respirable dust 10 mg/m³, Portland cement 10 mg/m³ inhalable.
What HVAC duct goes into a TBM operator cab and gantry crew compartment?
Modern Australian TBMs from Herrenknecht, Robbins, SELI Overseas, Hitachi Zosen and CREG have a climate-controlled operator cab at 18 to 22 degrees C with HEPA H10 filtration, CO/CO2/NO2 sensors and positive pressure +30 Pa. The gantry crew compartment 15 to 50 metres behind the cutterhead is climate-controlled at 18 to 22 degrees C with HEPA H10, CO/CO2/CH4 sensors and positive pressure +20 Pa. Internal duct distribution is 304 stainless welded construction because the cab and compartment sit in the harsh tunnel atmosphere for 12 to 36 months. SBKJ recommends the SBAL-V auto duct line in 304 stainless paired with the SB-ZF1500 longitudinal stitchwelder for the welded plenum sections.
How is tunnel face ventilation delivered through a TBM?
Tunnel face ventilation is delivered as a forcing ventilation system through lay-flat ducting (Sirroco Aerolite, SKF, Schauenburg) from a surface or portal-mounted primary fan to the working face. Typical face duty is 5 to 50 cubic metres per second through 1,000 to 2,000 mm flexible lay-flat ducting. Fan duty static pressure runs 1,500 to 4,500 Pa with booster fans in line for long drives. Rigid duct connections at the fan transition use heavy-gauge galvanised spiral fabricated on the SBTF-2020 for 2,000 mm primary fan duct on big projects, and the SBFB-1500 spiral fitting machine for transitions and bell-mouth inlets. Return air exits through the bored tunnel itself.
Why is diesel particulate matter DPM the biggest HVAC driver in TBM construction?
DPM is now established as the biggest occupational health hazard in TBM tunnel construction. Safe Work Australia sets the workplace exposure standard at 0.1 mg/m³ EC TWA. IARC classifies diesel engine exhaust as Group 1 carcinogen — same hazard class as asbestos. Dilution airflow required runs 0.05 to 0.16 cubic metres per second per kilowatt of installed diesel power. A modern TBM site with 5 to 20 megawatts of diesel load (back-up gantry, locomotive haulage, LHDs, muck haulage) moves thousands of cubic metres per second of total intake air just to dilute DPM. The shift to battery-electric muck haulage and rail-mounted electric locos on Sydney Metro West and Cross River Rail is the single biggest ventilation efficiency lever.
How is shaft sinking ventilation specified for Snowy 2.0 and Sydney Metro shafts?
Major shaft sinking projects include Snowy 2.0 Tantangara and Talbingo (Future Generation JV), Lower Western Sydney, Marinus Link, Iron Cove, and Sydney Metro West shaft sites at Westmead, Parramatta, Sydney Olympic Park, North Strathfield and the Bays. Shaft sinking ventilation is Zone 2 hazardous below grade by default. Typical duty is 30 to 100 cubic metres per second through 1,000 to 1,800 mm rigid duct on the shaft wall. Spark-resistant fans and IECEx Ex-d motors are mandatory. SBKJ recommends the SBTF-2020 for the 2,000 mm shaft primary duct and the SBAL-V in galvanised G275 for the shaft fan house at surface.
What HVAC duct goes into a shotcrete plant?
Shotcrete plant produces sprayed cementitious tunnel support. Australian suppliers include Pylon Australia, Mapei Australia, BASF Master Builders Solutions, Sika Australia and CTS Cement. The HVAC scope handles concrete spray aerosol, RCS at 0.05 mg/m³ TWA, alkali dust from Portland cement (10 mg/m³ inhalable irritant), chemical accelerator aerosol and cement aerosol. The shotcrete spraying operator station is the highest RCS exposure point in the entire tunnel construction scope. Duct material is 304 stainless welded construction because galvanised steel is attacked by alkali cement washdown and chemical accelerator residue. SBKJ recommends the SBAL-V in 304 stainless paired with the SB-ZF1500 stitchwelder.
How is a TBM emergency refuge chamber HVAC specified?
A TBM refuge chamber is a sealed compartment on or near the back-up gantry for 24 to 48 hour shelter. Internal HVAC scope covers compressed air supply, CO2 scrubbing via lithium hydroxide or soda lime, oxygen supplementation, positive pressure and temperature control. Internal duct is 304 stainless welded construction because the chamber may sit unused for months between use and the integrity standard at the moment crew need it is absolute. SBKJ recommends the SBAL-V in 304 stainless paired with the SB-ZF1500 stitchwelder for the refuge chamber internal duct distribution and CO2 scrubber plenum.
What is a hyperbaric chamber and where is it used in Australian tunnel construction?
A hyperbaric chamber is the compressed-air work facility for soft-ground intervention on a TBM cutterhead. The chamber pressurises the cutterhead chamber to 1 to 3 bar gauge above atmospheric allowing crew to enter and work without the ground collapsing. Used on Brisbane Cross River Rail and Melbourne Metro Tunnel for soft-ground tool changes. HVAC scope is medical-grade — clean dry air, oxygen and CO2 monitoring, temperature and humidity control, emergency depressurisation provisions. Duct is 304 stainless welded throughout. SBKJ recommends the SBAL-V in 304 stainless paired with the SB-ZF1500 stitchwelder.
What duct fabrication machines does SBKJ supply for TBM tunnel construction projects?
The SBTF-2020 spiral tubeformer fabricates 2,000 mm primary fan duct on the largest projects. The SBFB-1500 spiral fitting machine fabricates lay-flat tunnel ventilation transitions and bell-mouth inlets. The SBAL-V auto duct production line fabricates rectangular duct in SBAL-V galvanised G275 for general surface support and segment casting yard, and in 304 stainless for confined-space refuge chamber, TBM operator cab and CO2 scrubber. The SB-ZF1500 stitchwelder fabricates welded plenum sections in 304 stainless. The SBSF-1525 fabricates spiral seam for spiral duct production. The SBPC1500 plasma cutter cuts heavy-gauge plate. The SBLR-600 inverter welder welds field installation joints. Spark-resistant fans and IECEx Ex-d ATEX motors are mandatory for coal seam methane Zone 1, pyrite-bearing Sydney sandstone Zone 2 and diesel exhaust Zone 2.
What is the role of the Australasian Tunnelling Society and ITA in Australian TBM projects?
The Australasian Tunnelling Society (ATS) is the peak Australian tunnelling industry body and a sub-group of Engineers Australia, publishing guidance notes on tunnel ventilation, fire and life safety, shaft sinking and TBM operations. The International Tunnelling Association (ITA) is the global peak body with Working Group 5 publishing Health and Safety in Works guidance. The HVAC duct designer cross-references ATS guidance, ITA Working Group output, the relevant AS/NZS standards (AS 1668.2, AS 4254, AS 2865, AS 1746, AS 1530.4, AS/NZS 60079) and state mining/construction regulations. Supporting bodies include the Tunnelling Forum, Civil Contractors Federation (CCF), AusIMM and AusRAIL.
How long is the lead time for a TBM tunnel construction HVAC duct package?
TBM tunnel construction HVAC duct procurement typically runs 18 to 36 months from contract award to final delivery. Months 0–6 contract award and engineering coordination with the Tier 1 JV and TBM manufacturer. Months 6–12 first-of-type fabrication and FAT for the 304 stainless welded plenum sections. Months 12–24 bulk fabrication. Months 18–30 staged delivery aligned to TBM assembly and tunnel construction sequence. Months 24–32 installation and commissioning, including refuge chamber acceptance test, hyperbaric chamber acceptance test where applicable and hazardous area dossier sign-off. Months 30–36 Tier 1 JV handover.
