Coal Seam Gas (CSG), Cooper Basin, Bass Strait, Pipeline Compressor Station, LPG Terminal & Underground Gas Storage HVAC Duct Guide — Australian Engineering Reference

Why onshore gas HVAC is its own engineering discipline

Australian onshore gas is one of the largest industrial HVAC categories in the country by installed building count, even though it does not match the export-revenue scale of the offshore LNG complex covered in the sister LNG, gas processing, oil refinery, petrochemical and offshore platform HVAC duct guide. The reason is geography — the onshore gas footprint runs across thousands of wellheads, hundreds of gathering compressor stations, dozens of central processing facilities, more than ten thousand kilometres of high-pressure transmission pipeline, the mainline compressor stations spaced every 80 to 150 kilometres along the major pipelines, the underground gas storage facilities at the network interfaces, and the LPG terminals and cylinder filling plants that feed the regional and metropolitan gas markets. Every one of those buildings sits inside a hazardous-area envelope, and every one of them needs HVAC ductwork that is designed to AS/NZS 60079 and built in material that survives the local atmosphere for a 25 to 40 year asset life.

HVAC ductwork inside a CSG wellhead enclosure, a mainline pipeline compressor station, an LPG bulk terminal or an underground gas storage facility is not a comfort-cooling commodity. It is a safety-critical layer of protection between fugitive methane and propane emission and the people who operate the facility, between produced formation water and the maintenance technician, between vent stack discharge and the control room operator. The duct material has to survive simultaneous chloride attack from formation water aerosol, methane and propane vapour exposure, intermittent H2S at the partially-sour Cooper Basin and Moomba facilities, mercury vapour from gas treatment trains, glycol and amine mist from dehydration and sweetening processes, and the elevated temperature near the compressor turbine exhaust path. The fans, motors and dampers have to be IECEx or ATEX rated to the zone classification, spark-resistant under AMCA 99, and supplied with traceable documentation that goes into the operator's Major Hazard Facility Safety Case (Moomba, the larger compressor stations) or the state petroleum approval document (CSG wellheads, smaller gathering facilities, LPG terminals).

This guide is written for the engineers, project managers, safety leads and procurement specialists who plan, build, operate or refurbish onshore gas facilities in Australia — Origin Energy and the Australia Pacific LNG upstream operations on the Surat Basin, Santos at the Cooper Basin and the Narrabri Project in NSW, Shell QGC across the Surat coal seam gas footprint, Senex Energy (now POSCO-Hancock-Korea Gas owned) in the Surat Basin, Beach Energy at the Cooper Basin and the Otway Basin, Cooper Energy in the Otway, Strike Energy in the Perth Basin, ExxonMobil at the Bass Strait Longford gas plant, APA Group as the largest mainline transmission operator, Jemena, AusNet Services, AGN Australia Gas Networks, ATCO in Western Australia, Elgas (Origin), Kleenheat Gas, Mogas Regional and the various LPG distributors. It is also written for the EPC contractor base — Worley, Bechtel Australia, Saipem, Monadelphous, McConnell Dowell, John Holland, BMD Constructions, Civmec — and the fabrication shops that supply duct to those contractors.

The recurring failure mode we see in the Australian onshore gas market is identical to the one we see across LNG and refining — somebody specifies galvanised duct where 316L stainless was required, and inside two or three summers the zinc is consumed by combined chloride, methane vapour and intermittent H2S attack, the underlying carbon steel rusts through and fugitive emission breaches the building Safety Case. The cost of getting the metallurgy wrong is not a service call — it is a notifiable event under the relevant state petroleum and gas safety act.

The Australian onshore gas footprint — fields, basins and operators

Before specifying ductwork an engineer needs a clear picture of the asset base. Australian onshore gas is produced from a number of distinct sedimentary basins, each with its own gas chemistry, regulatory framework and HVAC design profile.

Surat Basin coal seam gas — Queensland

The Surat Basin in southern Queensland is the single largest coal seam gas province in Australia and the world's first major commercial CSG operation. The basin produces gas from the Walloon coal measures of the Jurassic age — coals at depths of approximately 200 to 1000 metres that hold methane in adsorbed form on the coal surfaces. The gas is liberated by reducing reservoir pressure through dewatering — pumping formation water out of the coal seam, which drops the pressure below the methane desorption point and releases the gas. The Surat Basin feeds the three coal seam gas LNG export projects on Curtis Island at Gladstone: Queensland Curtis LNG (Shell QGC), Australia Pacific LNG (ConocoPhillips, Origin) and Gladstone LNG (Santos). The gas is sweet — H2S typically below 4 ppm — and the dominant impurity is water from the coal seam.

The HVAC scope across a Surat Basin CSG field is distributed and modular. Each wellhead pad has a small Christmas tree fitting envelope and a separator/dewatering unit; clusters of 5 to 20 wells feed a low-pressure gathering compressor station; multiple gathering stations feed a central processing facility that compresses the gas to high pressure and dehydrates it for pipeline delivery to Curtis Island. Every wellhead pad, every gathering station and every central processing facility has a control kiosk, a substation and a workshop. The building count across the Surat Basin runs into the thousands.

Bowen Basin coal seam gas — Queensland

The Bowen Basin in central Queensland produces coal seam gas from the Bandanna formation and the Baralaba coal measures at depths of approximately 300 to 1200 metres. The basin is more variable than the Surat — sections carry trace H2S and CO2 that require selective amine sweetening at the central processing facility — but the bulk of the production is sweet. The Bowen Basin feeds the same Curtis Island LNG export complex as the Surat Basin, supplemented by some domestic gas delivery.

Narrabri Project coal seam gas — New South Wales

The Narrabri Project, operated by Santos in northern NSW, is the dominant onshore gas development in New South Wales. The project taps coal seam gas from the Maules Creek formation and the Black Jack Group at depths of approximately 600 to 1200 metres. The project has been progressively approved through the NSW Petroleum (Onshore) Act 1991 framework and is targeted at supplying eastern Australian gas demand once production is fully ramped. The gas is sweet. The Aboriginal Heritage Act and the Native Title legislation are particularly active across the Pilliga Forest area where the project sits, and the Land Access Code and the Right to Negotiate provisions are active across the cropping land to the east.

Cooper Basin conventional gas — South Australia and Queensland

The Cooper Basin in the far north of South Australia and the south-west corner of Queensland is the oldest onshore gas province in Australia, producing conventional gas from the Permian Patchawarra, Toolachee, Murteree and Roseneath formations at depths of approximately 1500 to 4500 metres. The Moomba gas processing complex is the central hub of the Cooper Basin, operated by Santos with Beach Energy and others as joint-venture partners. The Cooper Basin gas is partially sour — sections of the Toolachee and Patchawarra fields carry H2S at concentrations that do trigger ISO 15156 NACE MR0175 sour-service material selection, and the Moomba processing plant includes amine sweetening, sulphur recovery and dehydration. The Cooper Basin feeds the Moomba-Sydney Pipeline, the Moomba-Adelaide Pipeline and a number of feeder lines into the eastern gas market.

Otway Basin gas — Victoria and South Australia

The Otway Basin in south-western Victoria and south-eastern South Australia produces gas from the Eumeralla formation and the Waarre formation. Beach Energy and Cooper Energy operate the major onshore Otway facilities at the Otway Gas Plant. The Iona Gas Plant near Port Campbell in Victoria, operated by Lochard Energy, is the underground gas storage facility that uses a depleted Otway reservoir for seasonal storage of gas brought down from the Cooper Basin and the offshore Otway fields. The Otway gas is sweet.

Bass Strait Gippsland Basin — Victoria onshore receiving

The Bass Strait offshore fields produce gas that is delivered to the Longford Gas Plant near Sale in eastern Victoria for separation and processing. The Longford plant is operated by ExxonMobil with Santos as joint-venture partner. The onshore HVAC scope at Longford includes the gas plant building envelope, the LPG fractionation unit, the condensate handling area, the tank farm, the mainline metering station and the central control room. The Esso Long Island Point facility near Geelong is a related liquids handling facility. Bass Strait gas is sweet.

Perth Basin gas — Western Australia

The Perth Basin in Western Australia produces conventional gas from the Dongara, Beharra Springs and Walyering fields. Strike Energy is the most active operator in the basin in 2026. The gas is generally sweet but the basin has significant H2S in some legacy fields. The HVAC scope is comparable to the Otway onshore but with the ISO 9223 corrosivity reflecting inland WA rather than coastal Victoria.

Northern Territory and outback gas

The Mereenie field in central Northern Territory and the Beetaloo Sub-basin shale gas development north of Tennant Creek are the active onshore gas operations in the Territory. The Beetaloo Sub-basin is at an early stage of commercial development with Origin Energy, Tamboran Resources and Empire Energy as the active explorers. The HVAC scope is comparable to a Surat Basin gathering footprint but with substantially higher ambient temperatures and a more variable wet season.

CSG dewatering — the building envelope no other gas province has

Coal seam gas production is unique in the global gas industry because the gas is liberated by dewatering rather than by drilling into a free-gas reservoir. Every CSG wellhead pad has a dewatering pump — a submersible pump set inside the well casing that lifts formation water out of the coal seam, drops the reservoir pressure below the methane desorption point and releases the gas for production. The formation water that comes out is brackish to saline — typical Walloon coal measures water carries 1500 to 6000 mg/L total dissolved solids, with elevated sodium chloride, bicarbonate, sulphate and trace heavy metals depending on the specific coal seam — and at large volumes. The Surat Basin alone produces over 70 gigalitres of CSG formation water per year that has to be handled.

The formation water is delivered to a network of dewatering ponds at the wellhead pad, then trucked or pipelined to a central water treatment facility for reverse osmosis purification, brine concentration and ultimate beneficial reuse (agricultural irrigation, dust suppression on mine sites, return to streams) or evaporation pond disposal. The HVAC scope around the water handling envelope is:

• Dewatering pump shelter. Small shelter housing the variable-speed drive and the submersible pump controls. Zone 2 perimeter (formation water carries dissolved methane). 6 to 8 ACH normal, 25 ACH on methane LEL detection. 316L stainless on outside-air run, galvanised on internal recirculation in segregated office space. Spark-resistant fan with IECEx Ex-d motor.
• Water pond extract. The dewatering pond itself has an open-air vapour zone with continuous methane off-gassing. Small mechanical extract at the pond perimeter to maintain ventilation under stagnant-air conditions; 316L stainless ducting with continuous bonding.
• Reverse osmosis treatment building. RO membrane skid, chemical dosing, brine concentration. Not a hazardous-area envelope itself (the gas has been separated upstream) but exposed to high salt aerosol from the brine reject stream. 316L stainless throughout. 8 to 12 ACH normal.
• Brine concentration evaporator. Heated evaporator or mechanical vapour recompression. AS 4036 and AS 4037 pressure equipment apply. 316L stainless. 12 ACH normal because of elevated temperature and humidity.

The dewatering scope is the single most distinctive HVAC envelope on a CSG site compared to a conventional gas field. Conventional gas fields like the Cooper Basin produce small volumes of formation water (water cuts of a few percent typical) compared to the very high water-to-gas ratios at the start of a CSG well life. The duct fabrication implication is straightforward — 316L stainless throughout the wellhead and water-handling envelope from day one.

CSG wellhead Christmas tree and separator — Zone 1 and Zone 2 envelope

The wellhead Christmas tree at a CSG well is the assembly of valves, chokes and pressure gauges that controls the flow of produced fluid out of the well casing. Above the Christmas tree sit the production separator (a simple two-phase separator that splits the formation water from the gas), the dehydration glycol unit (where applicable — many CSG wellheads do not have local dehydration and rely on the gathering station for water removal) and the metering skid that totalises the well production.

The hazardous-area classification under AS/NZS 60079.10.1 is:

• Zone 1 — within approximately 1.5 metres of the Christmas tree fittings, the separator relief valve discharge, the dehydration glycol contactor vent and any other point where a release of methane is likely in normal operation.
• Zone 2 — within approximately 4.5 metres of the same fittings, and across the perimeter of any equipment shelter housing the production equipment.

The HVAC scope is:

• Wellhead Christmas tree. Open-air installation, no building envelope. No HVAC scope.
• Separator and dehydration shed. Small shelter housing the production separator and (where present) the dehydration glycol skid. Zone 2 interior under dilution ventilation. 8 ACH normal, 25 ACH on methane LEL detection. 316L stainless throughout. Spark-resistant fan with IECEx Ex-d motor.
• Metering and proving skid. Open-air or small shelter. Zone 2 if shelter present. 6 ACH normal. 316L stainless.
• Wellhead control kiosk. Small pressurised non-hazardous kiosk housing the RTU, the wellhead choke controller and the local instrument power. AS/NZS 60079.4 pressurisation at 50 Pa positive. Methane and oxygen detection in the intake. 316L stainless on outside-air run, galvanised internal recirculation. Standard general-purpose fan because pressurisation maintains non-hazardous classification inside the kiosk.

The duct envelope around a single wellhead pad is small — typically 30 to 50 metres of 316L stainless duct and 10 to 15 metres of galvanised duct in the segregated kiosk interior. The volume comes from the multiplier — a single Surat Basin field has hundreds to thousands of wellheads.

CSG gathering compressor station — Zone 2 envelope with continuous dilution

The output of the CSG wellheads is gathered through low-pressure flowlines to a gathering compressor station that boosts the pressure for delivery to the central processing facility. The gathering compressor is typically a reciprocating gas-engine driven compressor at low to medium pressure (10 to 70 bar discharge) handling 10 to 100 TJ/day of gas from 20 to 100 upstream wells. The Surat and Bowen Basin CSG fields have over 100 active gathering compressor stations across the operating gas tenements.

The gathering compressor station HVAC scope is:

• Compressor enclosure. The reciprocating compressor housed in a steel-framed shelter with louvred sides and a louvred roof for natural ventilation, supplemented by mechanical extract for emergency mode. Zone 2 by AS/NZS 60079.10.1 dilution-ventilation classification provided continuous mechanical ventilation at 6 to 10 ACH is maintained. On methane LEL detection at 20 percent the ventilation steps to 30 ACH emergency mode. 316L stainless throughout. Spark-resistant AMCA Type B fans with IECEx Ex-d motors. Belt drives anti-static. Approximately 80 to 150 metres of 316L stainless duct per station.
• Gas engine driver. Caterpillar or Waukesha gas-fired reciprocating engine producing 500 to 2500 kW shaft power. AS 4036 pressure equipment and AS 1318 industrial chimney requirements apply to the engine exhaust. The exhaust stack is 316L stainless with external lagging to prevent condensation and corrosion of the stack interior.
• Fuel gas skid. Small skid that conditions the engine fuel gas (filter, pressure regulator, knock-out drum). Zone 1 within 1.5 metres of the relief vent. 316L stainless extract over the skid.
• Operator and control kiosk. Pressurised non-hazardous kiosk under AS/NZS 60079.4 at 50 to 75 Pa positive pressure. Methane detection in the intake. 316L stainless on outside-air run, galvanised internal. Approximately 25 to 40 metres of duct.
• Substation and switchgear. Pressurised non-hazardous building under AS/NZS 60079.4 at 50 Pa positive. Standard general-purpose fan inside the pressurised envelope. 316L outside-air run, galvanised inside. Approximately 30 to 50 metres of duct.

The duct scope across a single gathering compressor station is approximately 200 to 300 metres total, with around 70 percent being 316L stainless and 30 percent galvanised in the segregated pressurised buildings.

CSG central processing facility — dehydration, sweetening and metering

The output of the gathering compressor stations is delivered to the central processing facility (CPF) that performs the final gas conditioning before delivery to the mainline pipeline. The CPF typically handles 500 to 1500 TJ/day at full ramp and is the most chemically complex part of the upstream CSG envelope. The HVAC scope includes:

• High-pressure compression. Final stage compression to mainline pressure (typically 100 to 150 bar). Centrifugal turbo-compressors driven by gas turbines or electric motors. Zone 2 enclosure. 12 ACH normal, 30 ACH emergency on methane LEL. 316L stainless with continuity-tested earthing. Approximately 150 to 250 metres of 316L per CPF.
• Dehydration TEG unit. Triethylene glycol absorber removes water from the gas stream before delivery to the pipeline. Zone 2. 8 to 12 ACH normal, 25 ACH emergency. 316L stainless. Approximately 80 to 120 metres.
• Amine sweetening unit (Bowen Basin partially sour CPFs). MDEA absorber removes H2S and CO2 from the trace-sour sections of the Bowen Basin and selected Surat fields. Zone 2 at the absorber, Zone 1 at the regenerator overhead. 15 ACH normal, 30 ACH on H2S at 10 ppm or hydrocarbon LEL. 316L stainless with localised Inconel 625 cladding at the regenerator overhead extract — sourced from specialist alloy fabricators outside SBKJ scope. Approximately 100 metres of 316L plus 15 to 25 metres of Inconel cladding where required.
• Custody transfer metering station. Ultrasonic or orifice meter station at the pipeline interface. Open structure with small pressurised metering hut. 316L stainless on outside-air to the hut. Approximately 30 metres.
• Pig launcher and receiver. Pipeline pigging equipment at the pipeline interface. Zone 1 within 1.5 metres of the closure door and any vent point. 316L stainless local extract over the launcher area. Approximately 40 metres.
• Vent stack and flare. Emergency relief discharge to vent stack (cold venting) or low-pressure flare for combustion of process upsets. Radiant heat envelope around the flare; the HVAC intake locations on adjacent buildings must be on the upwind side from the flare. AS 1318 industrial chimney requirements apply to the vent stack.
• Central control room. Pressurised blast-rated non-hazardous enclosure under AS/NZS 60079.4 at 75 Pa positive. Outside-air intake on the side furthest from the process. Methane, H2S (where applicable) and oxygen detection in the intake. 316L stainless on outside-air, galvanised on recirculation. Approximately 80 metres total.
• Workshop, store and amenity. Non-hazardous segregated. 316L outside-air, galvanised internal. Approximately 80 to 120 metres total.

The duct scope at a single CPF is approximately 600 to 900 metres total. The Surat and Bowen Basin CSG operations include eight to twelve operating CPFs across the joint Origin/QGC/APLNG/Santos footprint, plus expansion projects in progress.

Cooper Basin Moomba — the sour-service hub

The Moomba gas processing complex in the far north of South Australia is the central processing facility for the Cooper Basin and the largest and most chemically complex onshore gas plant in Australia. Moomba processes raw conventional gas from approximately 800 producing wells across the Cooper Basin and the Eromanga Basin, sweetens the partially-sour streams, recovers sulphur, fractionates the LPG components, dehydrates the gas and meters it for delivery to the Moomba-Sydney Pipeline, the Moomba-Adelaide Pipeline and several feeder lines. The site has been operating since 1969 and has been progressively expanded.

The HVAC scope at Moomba is similar to a CPF but at a larger scale and with a more demanding chemistry. Key differences from a Surat Basin CPF:

• Sulphur recovery unit. Claus process unit converting H2S from the amine regenerator into elemental sulphur. Zone 2 throughout. 15 to 20 ACH normal, 30 ACH emergency on H2S or SO2 detection. 316L stainless with localised Inconel 625 cladding on extract sections near the furnace skin and the catalytic reactor manholes. AS 4036 and AS 4037 pressure equipment apply. AS 1318 industrial chimney for the tail gas incinerator stack with CEMS for SO2 under air quality regulations.
• Sulphur storage. Solid sulphur prills or pastilles stored in shed. Zone 22 dust hazardous area. 8 to 12 ACH normal. 316L stainless with anti-static internal lining.
• Mercury removal unit. Sulphur-impregnated activated carbon bed removes trace mercury. Zone 2. 8 to 12 ACH normal, 25 ACH on mercury detection above 0.025 mg/m³. 316L stainless throughout. Spent carbon handled as hazardous waste at end of bed life.
• Mainline LPG fractionation. Fractionation columns separating ethane, propane, butane and heavier fractions for product delivery. AS/NZS 1596 LPG handling for the propane and butane streams. Zone 2 throughout. 12 ACH normal, 30 ACH emergency on propane LEL.
• Pipeline mainline metering and dispatch. Ultrasonic flow measurement at the pipeline take-off point. 316L stainless local extract over the metering envelope.

The Moomba site has approximately 1500 to 2000 metres of process building HVAC duct in 316L stainless plus 50 to 80 metres of Inconel 625 cladding in localised severe sour-service sections. The site sits in the inland desert atmosphere — ISO 9223 corrosivity is lower than the coastal Pilbara C5-M but still significant because of the periodic high-dust events and the high diurnal temperature variation.

Bass Strait Longford Gas Plant — onshore receiving and processing

The Longford Gas Plant near Sale in eastern Victoria is the onshore receiving and processing facility for the Bass Strait offshore gas fields operated by ExxonMobil with Santos as joint-venture partner. The plant receives raw gas, condensate and oil from the offshore platforms through subsea pipelines, separates the streams, processes the gas for pipeline delivery into Victoria and beyond, and processes the condensate and crude oil for shipment to refineries. The site has been operating since 1969 and is one of the largest onshore gas processing complexes in Australia.

The HVAC scope at Longford is comparable to a Cooper Basin or Surat Basin CPF but with the additional liquids-handling envelope for condensate and crude oil. Key building scopes:

• Gas processing trains. Multiple parallel trains handling raw gas separation, dehydration, LPG fractionation and final pipeline metering. Zone 2 throughout the equipment shelters. 12 ACH normal, 30 ACH emergency. 316L stainless throughout because of the combined coastal salt and hydrocarbon atmosphere.
• Condensate handling. Stabilisation columns and storage tanks. AS 1940 flammable liquids storage. Zone 1 at the tank breather vents. Zone 2 across the surrounding envelope. 12 ACH at the operator shelters. 316L stainless.
• Pipeline mainline metering and dispatch. Ultrasonic flow measurement at the pipeline take-off into the Eastern Gas Pipeline and the South East Australia Gas Pipeline. 316L stainless.
• Esso Long Island Point. Related liquids handling facility near Geelong on Corio Bay. Tank farm, marine berth, LPG and condensate loading. AS 1940 flammable liquids. AS/NZS 1596 LPG. ISO 9223 C5-M coastal corrosivity. 316L stainless throughout.

Mainline pipeline compressor station — Zone 2 envelope at 80 to 150 km spacing

Once gas leaves the central processing facility it enters the high-pressure transmission pipeline network — the largest pipeline operator in Australia is APA Group, which owns the East Australian Gas Pipeline, the Moomba-Sydney Pipeline, the Roma-Brisbane Pipeline and the QSN3 Queensland to NSW Interconnect. Jemena owns the Northern Territory Gas Pipeline and the Queensland Gas Pipeline. AusNet Services owns the Victorian gas transmission network. AGN Australia Gas Networks owns the distribution networks across SA, VIC and QLD. ATCO owns the WA gas distribution network. The transmission pipelines run at typically 7 to 15 MPa pressure and require booster compression at intervals of approximately 80 to 150 kilometres to maintain pipeline pressure against pipeline pressure drop.

The mainline compressor station HVAC scope is similar to the CSG gathering compressor station but at a larger scale and with more demanding chemistry because the gas is the conditioned product:

• Mainline compressor enclosure. Centrifugal compressor driven by gas turbine (typically Solar Mars or Taurus units) or electric motor. Zone 2 by AS/NZS 60079.10.1 dilution-ventilation classification provided 12 ACH continuous is maintained. On methane LEL at 20 percent the ventilation steps to 30 ACH emergency. 316L stainless throughout. Spark-resistant fans AMCA Type B or C. IECEx Ex-d motors. Approximately 150 to 250 metres of 316L stainless duct per station.
• Gas turbine driver. Solar Mars 100 (10 MW) or Solar Titan 130 (15 MW) or Taurus 60 (5 MW) gas-fired turbine. AS 4036 and AS 4037 pressure equipment and AS 1318 industrial chimney for the exhaust. The exhaust stack is 316L stainless with external lagging.
• Fuel gas skid. Conditioning skid (filter, pressure regulator, knock-out drum) at the inlet to the gas turbine. Zone 1 within 1.5 metres of relief vent. 316L stainless local extract.
• Inlet gas filter. Mainline gas filter at the station inlet. Zone 2 perimeter. 316L stainless.
• Cooler bay. Aerial coolers for the compressed gas heat removal. Open structure. No HVAC scope (atmospheric).
• Operator and control kiosk. Pressurised non-hazardous under AS/NZS 60079.4. 50 to 75 Pa positive. Methane detection in intake. 316L outside-air, galvanised internal. Approximately 40 to 60 metres.
• Substation. Pressurised non-hazardous. 50 Pa positive. 316L outside-air, galvanised internal. Approximately 40 to 60 metres.
• Workshop. Non-hazardous segregated. 316L outside-air for coastal stations, galvanised inland. 60 to 90 metres.
• Amenity. Non-hazardous segregated. Commercial-grade HVAC. 60 to 80 metres.

The duct scope at a single mainline compressor station is approximately 400 to 700 metres total, with around 65 percent being 316L stainless and 35 percent galvanised in the segregated pressurised buildings. The total mainline compressor station count across the Australian transmission network runs to approximately 50 to 70 stations across the major pipelines.

Mainline metering station and meter run — Zone 2

At every interface between operators on the gas transmission network there is a custody transfer metering station that measures the gas flow for billing and pipeline balance accounting. The mainline metering stations are open-air installations with an ultrasonic flow meter package, a chromatograph that measures gas composition (CO2, methane, ethane, propane and heavier fractions) for energy content calculation, and a small metering hut that houses the flow computer and the chromatograph itself.

• Meter run. Open structure. Zone 2 perimeter. No HVAC scope.
• Metering hut. Small pressurised non-hazardous building. 50 Pa positive. Methane detection in intake. 316L outside-air. Approximately 20 to 30 metres of duct.
• Pressure regulation station. Where applicable, pressure step-down between transmission and distribution pressure. Zone 2 perimeter. Small pressurised regulator shelter.

Pig launcher and receiver — Zone 1 vapour handling

Pipeline cleaning and inspection is carried out by sending instrumented "pigs" down the pipeline at regular intervals (typically 6 to 24 months). The pig is launched from a pig launcher trap at the upstream end of the pipeline section and received at a pig receiver trap at the downstream end. Each launching and receiving operation involves opening a pressurised closure door, which is a controlled release of gas to atmosphere; the operation is therefore a Zone 1 event in normal use.

• Pig launcher / receiver shed. Shelter housing the launcher or receiver barrel. Zone 1 within 1.5 metres of the closure door and any vent point during a pigging operation. Zone 2 perimeter the rest of the time. 12 ACH normal, 30 ACH emergency on methane LEL. 316L stainless. Approximately 50 to 80 metres of duct.
• Pig handling area. Open area or canopy for removing the pig from the barrel after a run. Zone 2.

Underground gas storage — Iona, Newport, Ironbark

Underground gas storage provides seasonal flexibility to the Australian gas market — gas is injected into a storage facility during periods of low demand (summer for residential heating) and withdrawn during periods of high demand (winter). The Australian underground gas storage facilities are:

• Iona Gas Plant. Near Port Campbell in Victoria, operated by Lochard Energy. The facility uses a depleted Otway Basin reservoir for storage. Capacity approximately 25 PJ working gas. The site combines depleted reservoir storage with surface processing for the Otway gas production.
• Newport Gas Storage. Near Port Campbell in Victoria, second underground gas storage facility serving the Victorian and southeast Australian gas market.
• Ironbark Gas Storage. In southern Queensland, operated as a depleted reservoir storage facility for the eastern Australian gas market.
• Calliope Gas Storage. Additional storage facility near Gladstone Queensland.

The HVAC scope at an underground gas storage facility is similar to a CSG CPF with additional complexity for the injection/withdrawal cycling. The wellhead area is Zone 1 within 1.5 metres of fittings and Zone 2 to 4.5 metres. The injection/withdrawal compressor enclosure is Zone 2 by dilution ventilation at 12 ACH minimum. The dehydration train conditions the withdrawn gas before pipeline delivery — every storage cycle changes the gas composition slightly as gas mixes with the residual hydrocarbons in the reservoir, and the dehydration train must accommodate the variability. The duct material is 316L stainless throughout because the site sits in a continuous methane vapour exposure envelope with formation water that may carry corrosive products from the underlying reservoir.

LPG bulk terminal — Zone 1, Zone 2 and vapour return

Liquefied petroleum gas (LPG — predominantly propane and butane mix in Australia) is handled at bulk terminals that receive product from refineries, gas plants and shipping imports, store it in pressurised bullet tanks or refrigerated atmospheric tanks, and dispatch it for downstream distribution by truck, rail or pipeline. The major Australian LPG distributors are Elgas (Origin), Kleenheat Gas (Wesfarmers Chemical, Energy and Fertilisers, WA), Mogas Regional and BP Australia. AS/NZS 1596 (Storage and handling of LP Gas) is the primary Australian standard governing the entire LPG bulk envelope.

• LPG bulk storage tank — pressurised bullet. Horizontal cylindrical pressure vessel typically 100 to 500 tonnes capacity. AS 4036 and AS 4037 pressure equipment. AS/NZS 1596 LPG handling. Zone 1 within 1.5 metres of any fitting (relief valve, manway, instrument tapping). Zone 2 to 4.5 metres. No building envelope around the bullet — open-air installation. HVAC scope is limited to the local extract over the manway and the relief valve discharge area if needed.
• LPG bulk storage tank — refrigerated atmospheric. Some larger terminals (Sydney, Brisbane) use refrigerated atmospheric tanks at -42°C for propane and -1°C for butane. Concentric double-shell construction. Zone 1 at fittings, Zone 2 perimeter. No major HVAC scope on the tank itself.
• LPG truck loading rack. Loading arms and vapour return system at the truck loading rack. Zone 1 within 1.5 metres of loading arm and vapour return point. Zone 2 to 4.5 metres. 316L stainless local extract over the loading rack envelope. Vapour return system collects vented LPG vapour during truck filling and routes back to vapour recovery unit or low-pressure storage. Grounding cable mandatory before loading commences.
• LPG rail loading. Where present (Geelong, Lytton, Botany). Comparable Zone 1 envelope to truck loading.
• LPG marine berth. Where present (LPG import or export). Zone 1 at the manifold. 316L stainless local extract.
• Vapour recovery unit. Compressor that recovers vented LPG vapour and returns it to the storage tank. Zone 2 enclosure. 12 ACH normal, 30 ACH emergency on propane LEL at 20 percent. Spark-resistant fan with IECEx Ex-d motor. 316L stainless throughout.
• Operator and control building. Pressurised non-hazardous under AS/NZS 60079.4 at 50 to 75 Pa positive. Propane and oxygen detection in intake. 316L outside-air, galvanised internal. Approximately 60 to 80 metres of duct.
• Pump shelter. LPG transfer pumps housed in shelter. Zone 1 within 1.5 metres of fittings. Zone 2 perimeter. 12 ACH normal, 30 ACH emergency. 316L stainless with continuity bonding. Approximately 80 to 120 metres.

LPG cylinder filling plant — Zone 1 with continuous detection

LPG cylinder filling is the operation that fills the standard portable LPG cylinders used across the Australian market — the 9 kg BBQ cylinder, the 4.5 kg automotive forklift cylinder, the 3.7 to 7 kg leisure caravan cylinder, the 45 kg domestic cylinder and various commercial sizes. Cylinder filling plants are located at the LPG bulk terminals and at standalone filling plants near major population centres. AS 4332 (cylinder gas) and AS 4838 (LPG cylinders for decanting) apply.

• Cylinder filling shed. Steel-framed shelter with louvred sides for natural ventilation, supplemented by mechanical extract. The filling carousel houses 8 to 24 filling stations that simultaneously fill cylinders by weight. Zone 1 within 1.5 metres of any filling head and any vent point. Zone 2 across the shelter envelope. AS/NZS 1596 ventilation requirements apply: typically 12 ACH normal, 30 ACH on propane LEL at 20 percent. Spark-resistant fan AMCA Type B or C with IECEx Ex-d motor. 316L stainless throughout with continuity-tested earthing. Approximately 100 to 150 metres of 316L per filling shed.
• Cylinder storage area. Outdoor storage of full and empty cylinders. AS 4332 cylinder racking. Open-air, Zone 2 perimeter, no HVAC scope.
• Cylinder testing and refurbishment. Internal cleaning, pressure testing and refurbishment of returned cylinders. AS 2030 hydrostatic test where required. Zone 2 perimeter. 8 to 12 ACH normal. 316L stainless local extract over the test envelope.
• Operator and control kiosk. Pressurised non-hazardous. 50 to 75 Pa positive. Propane detection in intake. 316L outside-air, galvanised internal. Approximately 30 to 50 metres.

LPG decanting station — retail and small commercial

LPG decanting stations are the retail filling points where small cylinders are filled from a bulk on-site tank. The most common installation is the BBQ cylinder swap-and-fill at service stations, hardware retailers and caravan parks. AS 4838 governs the decanting operation.

• Decanting cabinet. Small cabinet containing the filling pump, the scales and the filling hose. Zone 1 within 1.5 metres of the filling head. Zone 2 perimeter. Mechanical extract over the cabinet on propane LEL detection. 316L stainless local extract. AS/NZS 1596 separation distances from any ignition source.
• Bulk supply tank. Small pressurised bullet typically 1000 to 5000 kg capacity. AS 4036 pressure equipment. Open-air installation. No HVAC scope.

Why galvanised duct fails inside two or three summers in onshore gas

The failure mode for galvanised duct in Australian onshore gas service is the same as for LNG and refining but with three additional drivers specific to onshore gas:

• Formation water aerosol. CSG wellhead pads have continuous formation water handling at the dewatering pond and the truck loading. The aerosol from the pond surface and the truck-loading splash carries sodium chloride, bicarbonate and sulphate that disrupts the zinc passive layer at any duct surface within drift range.
• Intermittent H2S. Cooper Basin Moomba and selected Bowen Basin facilities have intermittent H2S exposure at concentrations that consume zinc at orders of magnitude faster than chloride alone. The Safe Work Australia exposure standard for H2S is 10 ppm TWA / 15 ppm STEL — a fugitive concentration well below this threshold is still enough to attack zinc.
• Mercaptan odorant. All Australian distribution gas (downstream of the pipeline metering) is odorised with ethyl mercaptan or tert-butyl mercaptan for leak detection. The mercaptan is sulphur-based and attacks zinc. Distribution-side facilities (city gates, regulating stations, holder yards) have this exposure.

The Surat Basin and the Bowen Basin sit in ISO 9223 corrosivity category C3 to C4 depending on the season and the coastal proximity. The Cooper Basin sits in C2 to C3 (drier inland atmosphere) but the localised chemistry around Moomba lifts the effective corrosivity to C5 or higher in the H2S envelope. Bass Strait Longford and the Otway sites are coastal C5-M. The Northern Territory inland sites are C3 to C4. The net of all of this is that galvanised duct can be relied upon only for office, amenity and warehouse HVAC in segregated non-hazardous administrative buildings physically offset from the process area. Every other duct in onshore gas is 316L stainless.

316L stainless — the onshore gas HVAC default

The default material for HVAC ductwork in Australian onshore gas, pipeline compressor station, LPG terminal and underground gas storage service is austenitic stainless steel grade 316L. The L stands for low-carbon (≤0.03 percent carbon) — the low-carbon variant resists sensitisation and intergranular corrosion in the heat-affected zone after welding, which matters because every joint in a TIG-welded sour-service duct is a welded joint.

The relevant 316L chemistry is approximately 17 percent chromium, 12 percent nickel and 2.5 percent molybdenum. The chromium forms the passive chromium-oxide layer that protects the alloy; the nickel stabilises the austenitic phase; the molybdenum gives the alloy its resistance to chloride pitting — the dominant failure mechanism of the cheaper 304 stainless in coastal and brackish-water environments. Every Australian onshore gas site is exposed to either coastal salt or formation water salinity, and the chloride loading is enough to drive a switch from 304 to 316L throughout.

For SBKJ-fabricated 316L duct the standard configuration is full-thickness 316L sheet stock (1.2 mm minimum for low-pressure extract, 1.6 mm or 2.0 mm for process-extract and any duct downstream of a fan), longitudinal seams TIG-welded with 316L filler metal on the SB-ZF1500 automatic stitchwelder, transverse joints either TIG-welded butt joints or 316L flanged joints with chemically compatible gaskets (EPDM, Viton or PTFE depending on chemistry). Internally the duct is passivated after welding with a citric or nitric pickle to restore the chromium-oxide layer in the heat-affected zone. The result is a duct that lasts 25 to 40 years in service — matching the plant design life.

Inconel 625 — for the Moomba sulphur recovery and severe sour-service nodes

316L is not the answer for the Moomba sulphur recovery unit and the small number of severe sour-service nodes elsewhere. The two scenarios where it fails are wet H2S at high partial pressure and high-temperature acid attack. Wet H2S above approximately 100 ppm can cause sulphide stress cracking in even the low-carbon stainless grades; in those environments the upgrade specification is to a nickel-base alloy — Inconel 625, Inconel 825 or Hastelloy C-276 depending on the specific chemistry. ISO 15156 NACE MR0175 is the international standard that governs material selection for sour service and is referenced throughout Australian gas-industry specifications.

The relevant scenarios on Australian onshore gas sites are:

• Moomba sulphur recovery unit (SRU) — Inconel 625 on hot tail-gas paths. The Claus process furnace tail gas carries SO2, residual H2S, sulphur vapour and water at elevated temperature. Localised duct sections are clad with Inconel 625 or specialised refractory-lined steel.
• Moomba amine regenerator overhead — Inconel 625 cladding on hot rich-amine extract. The rich amine stream leaving the absorber is loaded with H2S and CO2; the regenerator overhead carries hot wet acid gas. Localised duct sections near these points are clad with Inconel 625 to resist sulphide stress cracking.
• Selected partially-sour Cooper Basin gathering facilities. Where the local gas chemistry exceeds the NACE threshold for short-term H2S exposure.

The procurement reality is that Inconel costs roughly five to eight times the equivalent 316L on a per-tonne basis, and the welding requires specialist procedures that are outside the standard SBKJ scope. The right approach is to map the duct network bay-by-bay and use 316L for general service with localised Inconel cladding at the severe sour-service nodes — supplied by specialist alloy fabricators that work alongside the SBKJ-equipped 316L shop. SBKJ does not fabricate Inconel or other superalloys directly; the SBAL-V, SB-ZF1500 and SBPC1500 are configured for 316L.

AS/NZS 60079 — the hazardous-area framework

The AS/NZS 60079 series is the Australian implementation of the international IEC 60079 hazardous-area standards. It is the governing technical standard for every electrical and ventilation specification inside an explosive-atmosphere envelope and applies across the entire onshore gas envelope.

AS/NZS 60079.10.1 — Classification of areas, explosive gas atmospheres

AS/NZS 60079.10.1 classifies areas where flammable gas or vapour may be present. The classification produces zones — Zone 0 where an explosive atmosphere is continuously present, Zone 1 where it is likely to be present in normal operation, and Zone 2 where it is unlikely and only present briefly. For an onshore gas site the classification yields:

• Zone 0 — inside the wellhead casing, inside a pressurised pipeline and inside the LPG bullet tank vapour space. Not a ventilation envelope.
• Zone 1 — wellhead Christmas tree fitting envelope, gathering manifold vent point, dehydration glycol contactor vent, separator relief valve discharge, LPG truck loading arm vapour zone, LPG cylinder filling head, LPG decanting cabinet, LPG bullet relief valve discharge, pig launcher/receiver closure door, vent stack discharge area, flare knock-out drum vicinity.
• Zone 2 — perimeter of the wellhead pad, perimeter of the gathering compressor enclosure, perimeter of the mainline compressor station, perimeter of the LPG bullet, perimeter of the LPG cylinder filling shed, perimeter of the pig launcher area, interior of process buildings where ventilation maintains continuous dilution.

HVAC fans, motors and dampers inside any of these zones must be IECEx-certified to match the zone. Ductwork is passive sheet metal and not certified as a product but must be electrically continuous and bonded to the site earth.

AS/NZS 60079.14 — Electrical installations design, selection and erection

AS/NZS 60079.14 governs the design, selection and erection of electrical installations in hazardous areas. For HVAC scope this is the standard that says the fan terminal box, the motor terminal box, the damper actuator and every cable gland must be selected to match the Equipment Protection Level (EPL) for the zone. The IECEx Ex marking on the fan and motor nameplates must trace back to a current IECEx certificate of conformity issued by a recognised certification body.

AS/NZS 60079.17 — Electrical installations inspection and maintenance

AS/NZS 60079.17 governs the inspection and maintenance of hazardous-area electrical installations. For HVAC this drives the maintenance schedule for fan and motor inspection, damper actuator inspection, gas detector calibration, the integrity check of duct earthing continuity and the cable-gland tightness check. The plant operator schedules these inspections at intervals defined by the standard and the maintenance records become part of the operating documentation.

AS/NZS 60079.19 — Equipment repair, overhaul and reclamation

AS/NZS 60079.19 governs the repair and overhaul of hazardous-area electrical equipment. Where a fan motor or damper actuator is removed for service the repair must be conducted to the standard, with the certification status preserved through the repair cycle.

AS/NZS 1596 — the LPG storage and handling standard

AS/NZS 1596 (The storage and handling of LP Gas) is the primary Australian standard governing every aspect of LPG storage, decanting, dispensing and cylinder handling. The standard sets the separation distances between LPG storage and ignition sources, the ventilation requirements for filling sheds and decanting cabinets, the spill containment requirements for the bullet tank impoundment, the bonding and grounding requirements for transfer operations, and the requirements for IECEx-rated equipment in the propane vapour envelope.

Key AS/NZS 1596 provisions for HVAC scope:

• Ventilation of indoor LPG areas. Filling sheds and decanting cabinets require continuous mechanical ventilation at sufficient rate to maintain propane concentration below 20 percent LEL across the operating envelope. Typical design is 12 ACH normal stepping to 30 ACH on detection.
• Hazardous-area classification. AS/NZS 60079.10.1 zone classifications around all LPG fittings and vapour-handling envelopes. Zone 1 within 1.5 metres of fittings, Zone 2 to 4.5 metres.
• Separation distances. LPG bullets must be separated from ignition sources by AS/NZS 1596 prescriptive distances based on tank size. HVAC intakes on adjacent buildings must respect these distances.
• Spill containment. Bullets are within an impoundment bund sized to contain the largest credible spill. The bund area is Zone 2 perimeter.
• Vapour recovery. Truck loading and cylinder filling vent points are captured into vapour recovery systems where practical, with the recovery compressor in a Zone 2 enclosure.

AS 5601 — LPG installations downstream of the bulk tank

AS 5601 (Gas installations) governs the LPG installation downstream of the cylinder or bulk tank — the piping from the tank to the appliance, the regulation equipment, the meter, the appliance connections and the installation safety devices. AS 5601 is the standard that the licensed gas fitter works to when installing or modifying an LPG (or natural gas) installation in any Australian residence or commercial property. For HVAC duct scope the relevance is at the LPG cylinder cabinet (commercial installations) and at the LPG decanting station (where the AS 5601 framework defines the gas fitter's interface with the AS/NZS 1596 storage scope).

AS 2885 — pipeline standard

AS 2885 (Pipelines — Gas and Liquid Petroleum) is the Australian pipeline standard that governs the design, construction, operation and maintenance of high-pressure gas and liquid petroleum pipelines. For onshore gas the relevance is at every mainline compressor station and every pipeline facility — the standard prescribes the safety case approach, the consequence analysis, the location class assessment and the operating procedures. For HVAC scope the connection is that the compressor station facility is part of the pipeline system and the HVAC scope on the station is documented in the pipeline Safety Case as a layer of protection.

NFPA 30, 30A, 50, 50A, 50B, 55 and 59 — the American reference framework

The NFPA standards are referenced in Australian onshore gas project Safety Cases as benchmark practice even though the Australian regulatory framework does not directly adopt them. The relevant NFPA standards are:

• NFPA 30 — Flammable and Combustible Liquids Code. Referenced for condensate, crude oil and refined product storage at the Bass Strait and Cooper Basin facilities.
• NFPA 30A — Code for Motor Fuel Dispensing Facilities and Repair Garages. Referenced for fuel-handling areas.
• NFPA 50 / 50A / 50B — Standard for Bulk Oxygen Systems / Liquefied Petroleum Gas / LP Gas Operation. Historical LPG standards now consolidated under NFPA 58.
• NFPA 55 — Compressed Gases and Cryogenic Fluids Code. Referenced for compressed gas storage including high-pressure pipeline scope.
• NFPA 58 — Liquefied Petroleum Gas Code. The current consolidated American standard for LPG handling, equivalent in scope to AS/NZS 1596.
• NFPA 59 — Utility LP-Gas Plant Code. Specifically for utility-scale LP-gas plants (large bulk terminals).

API 520, 521 and the pressure-relief interface

API 520 (Sizing, Selection, and Installation of Pressure-Relieving Devices) and API 521 (Pressure-relieving and Depressuring Systems) govern the flare and vent header design of process plants. The HVAC interface to these standards is that relief streams discharged at low level under fault conditions can flood the HVAC intake of an adjacent control room, substation or amenity building. Intakes must be placed so that a credible flammable-vapour cloud cannot be drawn into the building, which usually means high-level intakes on the side furthest from the process area and overpressure dampers wired through the gas-detection system.

API 1104 and ASME B31.3 / B31.8 — the piping interface

API 1104 (Welding of Pipelines and Related Facilities) and ASME B31.3 (Process Piping) and B31.8 (Gas Transmission and Distribution Piping Systems) govern the process piping and pipeline welding. These standards do not apply to ductwork — Australian ductwork follows AS 4254 and AS/NZS 1554.6 for welding — but they are referenced because the HVAC duct fabricator must understand the piping interface. The pipe penetrations through building walls are sealed with AS 1530.4 fire-rated penetrations.

AS 2865 — confined spaces (critical for wellhead and compressor station work)

AS 2865 (Confined spaces) is critical across the onshore gas envelope because wellhead Christmas tree access, separator manhole entry, compressor crankcase inspection, pig launcher barrel cleaning and LPG bullet manway entry are all confined space operations. The HVAC design has to provide controlled pre-entry ventilation, continuous monitoring of oxygen and combustible gases during entry, and gas-tight isolation from the surrounding pressurised system. For onshore gas the confined-space scope drives a number of specific HVAC features:

• Portable extract fans with IECEx Ex-d motors deployed at the confined space entry point during entry operations.
• Continuous gas detection (methane LEL, oxygen, H2S, propane) at the confined space face throughout the entry.
• Pre-entry purge with nitrogen or air to reduce hydrocarbon concentration before entry.
• Documented gas-free certificate before entry permits are issued.

Petroleum and gas legislation — state-by-state framework

Australian onshore gas operates under state petroleum and gas legislation, with each state having its own primary act and subordinate regulations. The relevant frameworks are:

NSW — Petroleum (Onshore) Act 1991

The NSW Petroleum (Onshore) Act 1991 governs onshore petroleum and gas operations in New South Wales, administered by the Department of Regional NSW. The Act is the primary statutory framework for the Narrabri Project. Layered on top are the WHS Regulations, the Major Hazard Facilities Regulations and the Aboriginal Heritage Act and Native Title legislation. The Land Access Code governs access to private land for petroleum exploration and production. The Right to Negotiate provisions of the Native Title Act apply across native title areas.

Queensland — Petroleum and Gas (Production and Safety) Act 2004

The Queensland Petroleum and Gas (Production and Safety) Act 2004 governs onshore petroleum and gas in Queensland and is the primary statutory framework for the Surat Basin, Bowen Basin and Cooper Basin operations. Subordinate regulations include:

• Queensland Coal Seam Gas Compliance Plan. Operational compliance framework for CSG operators across the state.
• Underground Water Impact Report. Mandatory assessment of formation water impact on aquifers.
• Surat Basin Strategic Cropping Land assessment. Land-use planning framework for the prime agricultural land overlying the CSG fields.
• Aboriginal Cultural Heritage Act. Native title and cultural heritage compliance.

South Australia — Petroleum and Geothermal Energy Act 2000

The SA Petroleum and Geothermal Energy Act 2000 governs Cooper Basin operations within South Australia (the Cooper Basin straddles the SA-QLD border with Moomba in SA). The Act is administered by the Department for Energy and Mining.

Victoria — Petroleum Act 1998 and Gas Industry Act

The Victorian Petroleum Act 1998 governs onshore petroleum operations in Victoria. The state has imposed a moratorium on onshore unconventional gas since 2017 (renewed periodically); conventional onshore gas exploration was reopened in 2021. The Gas Industry Act governs the downstream gas market.

Northern Territory — Petroleum Act

The NT Petroleum Act governs onshore petroleum in the Territory, including the Mereenie field and the emerging Beetaloo Sub-basin developments.

Western Australia — Petroleum and Geothermal Energy Resources Act

The WA Petroleum and Geothermal Energy Resources Act 1967 governs onshore petroleum in Western Australia, including the Perth Basin operations.

Safe Work Australia workplace exposure standards for onshore gas

The Safe Work Australia workplace exposure standards relevant to onshore gas, pipeline compressor station, LPG terminal and underground gas storage workers are:

• Methane (CH4) — 1000 ppm (asphyxiant). Detected via catalytic-bead or infrared LEL sensors at the 20 percent LEL trigger point (10,000 ppm in methane terms).
• Propane — 1000 ppm.
• Pentane (n-pentane) — 600 ppm.
• Hexane (n-hexane) — 50 ppm.
• Toluene — 50 ppm.
• Xylene — 50 ppm.
• Benzene — 1 ppm STEL (extremely toxic carcinogen present in trace amounts in some natural gas streams and in BTEX-rich condensate at Bass Strait Longford).
• Hydrogen sulphide (H2S) — 10 ppm TWA / 15 ppm STEL (extremely toxic). Cooper Basin Moomba and selected Bowen Basin facilities.
• Carbon monoxide (CO) — 30 ppm. From compressor station gas engine and gas turbine exhaust.
• Mercury (Hg) vapour — 0.025 mg/m³. From gas treatment trains (mercury removal unit and trace mercury vapour in raw gas).
• Arsine (AsH3) — 0.05 ppm STEL (extremely toxic). Present in some natural gas streams at trace concentration.
• Sulphur dioxide (SO2) — 2 ppm. From sulphur recovery at Moomba.
• Ammonia (NH3) — 25 ppm TWA / 35 ppm STEL. From sweetening solvent regeneration where amine systems use ammonia-compatible chemistry.
• MDEA (methyldiethanolamine) — 1 ppm. The dominant amine in modern Australian gas sweetening.
• Oxygen — 19.5% minimum, 23.5% maximum. Detected at confined space entry and at pressurised non-hazardous building intakes.

The HVAC design has to keep continuous exposure below these levels during normal operation and trigger emergency-mode extract on detection above the alarm setpoint.

Worked example — Surat Basin CSG gathering compressor station

To make the design discussion concrete, here is a notional summary of the HVAC envelope on a single Surat Basin coal seam gas gathering compressor station — typical of the Origin, QGC and APLNG operations across the Walloon coal measures. The site sits in inland southern Queensland in ISO 9223 corrosivity category C3 to C4, with combined methane vapour exposure, formation water aerosol from the dewatering envelope and the long humid wet season.

• Compressor enclosure. Zone 2 by dilution ventilation. 8 ACH normal, 30 ACH emergency on methane LEL. 316L stainless throughout with continuity bonding. Spark-resistant AMCA Type B fans, IECEx Ex-d motors. Approximately 120 metres of 316L stainless duct.
• Gas engine exhaust stack. 316L stainless with external lagging. Approximately 15 metres of stack.
• Fuel gas skid shelter. Zone 1 within 1.5 metres of relief vent. 316L stainless local extract. Approximately 25 metres.
• Operator and control kiosk. Pressurised non-hazardous at 50 to 75 Pa positive. Methane detection in intake. 316L outside-air, galvanised internal. Approximately 35 metres total.
• Substation. Pressurised non-hazardous at 50 Pa positive. 316L outside-air, galvanised internal. Approximately 40 metres total.
• Workshop and store. Non-hazardous segregated. 316L outside-air (because of formation water aerosol drift), galvanised internal. Approximately 60 metres total.
• Amenity. Non-hazardous segregated. Commercial-grade HVAC. Galvanised throughout (sufficient inland offset). Approximately 50 metres.

Total scope is approximately 345 metres of 316L stainless duct and 105 metres of galvanised duct in segregated non-hazardous spaces. The SBKJ machine line for this scope is the SBAL-V stainless auto duct line, the SB-ZF1500 stitchwelder, the SBSF-1525 hydraulic flanging machine, the SBPC1500 plasma cutter, and the SBLR-600 for any aluminium flexible duct in the kiosk recirculation. Total shop fabrication is approximately three weeks single-shift. The QGC, APLNG, Origin and Senex CSG operations each have between 30 and 80 gathering compressor stations across their operating tenements — multiplying the scope substantially.

Worked example — Moomba sulphur recovery unit and amine sweetening

The second worked example is the Moomba central processing facility in the Cooper Basin — specifically the sulphur recovery unit and the amine sweetening section, modelled loosely on the Santos Moomba operations. The site sits in the inland desert atmosphere of the SA-QLD border region with ISO 9223 C2 to C3 corrosivity, but the localised process chemistry around the sulphur recovery and amine envelope lifts the effective corrosivity to a much more aggressive level. The scope:

• Amine absorber building. Zone 2 throughout. 12 ACH normal, 30 ACH emergency on H2S at 10 ppm or hydrocarbon LEL. 316L stainless throughout. Approximately 180 metres of 316L stainless duct.
• Amine regenerator building. Zone 1 at the regenerator overhead, Zone 2 elsewhere. 15 ACH normal, 30 ACH emergency. 316L stainless with localised Inconel 625 cladding at the regenerator overhead extract (sourced from specialist alloy fabricators outside SBKJ scope). Approximately 140 metres of 316L plus 20 metres of Inconel cladding.
• SRU furnace and reactor enclosure. Zone 2. 18 ACH normal, 30 ACH emergency. 316L stainless with localised Inconel cladding on the furnace and reactor extract. AS 4036 and AS 4037 pressure equipment apply. Approximately 200 metres of 316L plus 30 metres of Inconel.
• Sulphur storage shed. Zone 22 dust envelope. 10 ACH normal, 25 ACH emergency. 316L stainless with anti-static internal lining and continuous earthing. Approximately 100 metres.
• Tail gas incinerator stack. 316L stainless with external lagging. AS 1318 industrial chimney. CEMS for SO2 monitoring. Approximately 25 metres of stack.
• Mercury removal unit. Zone 2. 10 ACH normal, 25 ACH emergency on mercury detection. 316L stainless. Approximately 60 metres.
• Operator and control building. Pressurised non-hazardous at 75 Pa positive. H2S, methane and oxygen detection in intake. 316L outside-air, galvanised internal. Approximately 70 metres total.

Total scope is approximately 750 metres of 316L stainless duct, 50 metres of Inconel 625 cladding (specialist sub-contract), and 120 metres of galvanised duct in segregated non-hazardous spaces. SBKJ machine line is the same as the gathering compressor station. Total shop fabrication is approximately seven to eight weeks single-shift, with the Inconel sub-contract running in parallel.

Worked example — APA Group mainline compressor station

The third worked example is a notional APA Group mainline compressor station along the Moomba-Sydney Pipeline, modelled loosely on the operational compressor stations between Moomba and Wilton. The site sits in inland NSW or western Queensland at ISO 9223 C2 to C3 corrosivity. The scope:

• Mainline compressor enclosure. Solar Mars 100 or Taurus 60 gas turbine driver, centrifugal compressor. Zone 2 by dilution ventilation. 12 ACH normal, 30 ACH emergency. 316L stainless throughout. Spark-resistant AMCA Type B fans, IECEx Ex-d motors. Approximately 200 metres of 316L stainless duct.
• Gas turbine exhaust. AS 4036 and AS 4037 pressure equipment, AS 1318 industrial chimney. 316L stainless exhaust stack with external lagging. Approximately 25 metres.
• Fuel gas skid. Zone 1 within 1.5 metres of relief vent. 316L stainless local extract. Approximately 25 metres.
• Aerial cooler bay. Open structure. No HVAC scope.
• Pig launcher / receiver. Zone 1 within 1.5 metres of closure door during operation. 316L stainless local extract. Approximately 50 metres.
• Operator and control building. Pressurised non-hazardous at 75 Pa positive. Methane detection in intake. 316L outside-air, galvanised internal. Approximately 60 metres total.
• Substation and switchgear. Pressurised non-hazardous. 50 Pa positive. 316L outside-air, galvanised internal. Approximately 50 metres total.
• Workshop and store. Non-hazardous segregated. 316L outside-air (low corrosivity inland), galvanised internal. Approximately 70 metres total.
• Amenity. Non-hazardous segregated. Commercial-grade HVAC. Galvanised throughout. Approximately 60 metres.

Total scope is approximately 480 metres of 316L stainless duct and 130 metres of galvanised duct in segregated non-hazardous spaces. SBKJ machine line as previous examples. Total shop fabrication is approximately four to five weeks single-shift.

Worked example — Elgas LPG bulk terminal and cylinder filling plant

The fourth worked example is a notional Elgas (Origin) LPG bulk terminal and cylinder filling plant on the outskirts of a major Australian capital city. The site receives bulk LPG by rail, stores in pressurised bullets and fills cylinders for retail and commercial distribution. The site sits in an industrial-zoned coastal corridor at ISO 9223 C4 to C5-M corrosivity. The scope:

• LPG bullet storage area. Three 200 tonne pressurised bullets. AS 4036 and AS 4037 pressure equipment, AS/NZS 1596. Zone 1 within 1.5 metres of fittings, Zone 2 to 4.5 metres. No major HVAC scope on the open bullet installation.
• LPG transfer pump shelter. Zone 1 within 1.5 metres of fittings, Zone 2 perimeter. 12 ACH normal, 30 ACH emergency on propane LEL. 316L stainless throughout with continuity bonding. Spark-resistant AMCA Type B fan, IECEx Ex-d motor. Approximately 90 metres of duct.
• LPG rail unloading rack. Zone 1 within 1.5 metres of loading arm and vapour return. Open structure. 316L stainless local extract over the loading rack. Approximately 60 metres.
• LPG truck loading rack. Same scope as rail. Approximately 60 metres.
• LPG cylinder filling shed. 16-station filling carousel. Zone 1 within 1.5 metres of filling heads, Zone 2 across shelter envelope. AS 4332 cylinder handling, AS 4838 decanting. AS/NZS 1596 ventilation. 12 ACH normal, 30 ACH emergency. Spark-resistant fan, IECEx Ex-d motor. 316L stainless throughout. Approximately 130 metres.
• Vapour recovery unit. Compressor recovers vented LPG vapour to the bullet. Zone 2 enclosure. 12 ACH normal, 30 ACH emergency. Spark-resistant fan. 316L stainless. Approximately 60 metres.
• Cylinder testing and refurbishment. Zone 2 perimeter. 8 to 12 ACH normal. 316L stainless local extract. Approximately 50 metres.
• Operator and control building. Pressurised non-hazardous at 75 Pa positive. Propane and oxygen detection in intake. 316L outside-air, galvanised internal. Approximately 60 metres total.
• Workshop and store. Non-hazardous segregated. 316L outside-air (coastal), galvanised internal. Approximately 50 metres total.
• Amenity. Non-hazardous segregated. Commercial-grade HVAC. 316L outside-air (coastal). Approximately 50 metres.

Total scope is approximately 660 metres of 316L stainless duct and 100 metres of galvanised duct in segregated non-hazardous spaces. SBKJ machine line as previous examples. Total shop fabrication is approximately six weeks single-shift.

Worked example — Iona Gas Plant underground gas storage

The fifth worked example is the Iona Gas Plant underground gas storage facility near Port Campbell in Victoria, modelled loosely on the Lochard Energy operations. The site sits in coastal western Victoria at ISO 9223 C5-M corrosivity, with continuous salt aerosol exposure. The scope:

• Injection and withdrawal compressor enclosure. Reciprocating or centrifugal compressor for the high-pressure injection cycle. Zone 2 by dilution ventilation. 12 ACH normal, 30 ACH emergency on methane LEL. 316L stainless throughout with continuity bonding. Spark-resistant fans, IECEx Ex-d motors. Approximately 180 metres of 316L stainless duct.
• Dehydration TEG unit. Removes formation water and reservoir hydrocarbons from the withdrawn gas. Zone 2. 12 ACH normal, 30 ACH emergency. 316L stainless. Approximately 100 metres.
• Wellhead area. Zone 1 within 1.5 metres of the injection/withdrawal wellhead fittings, Zone 2 to 4.5 metres. Open-air installation. No major HVAC scope.
• Mainline metering and dispatch. 316L stainless local extract. Approximately 30 metres.
• Pig launcher and receiver. Zone 1 at closure door. 316L stainless local extract. Approximately 50 metres.
• Operator and control building. Pressurised non-hazardous at 75 Pa positive. Methane and oxygen detection in intake. 316L throughout because of the coastal salt envelope. Approximately 70 metres total.
• Substation. Pressurised non-hazardous. 316L throughout. Approximately 50 metres total.
• Workshop and store. Non-hazardous segregated. 316L outside-air (coastal), galvanised internal. Approximately 60 metres total.
• Amenity. Non-hazardous segregated. 316L outside-air (coastal). Approximately 50 metres.

Total scope is approximately 580 metres of 316L stainless duct and 70 metres of galvanised duct. SBKJ machine line as previous examples. Total shop fabrication is approximately five weeks single-shift.

SBKJ machine configuration for onshore gas ductwork

Fabricating onshore gas ductwork at the scale required by Australian CSG, conventional gas, mainline pipeline, LPG and underground gas storage projects — typically 300 to 1500 metres of run per facility, multiplied across thousands of wellheads and dozens of compressor stations — requires the right shop equipment. The SBKJ standard machine configuration for onshore gas fabrication shops is:

• SBAL-V stainless 316L auto duct line. The SBAL-V is the stainless variant of the SBAL auto duct line, configured with 316L-compatible tooling, full TIG-welded longitudinal seam closure and a coil de-coiler and leveller sized for 316L sheet stock at 1.2 mm to 2.0 mm thickness up to 1500 mm wide. The line produces rectangular duct sections at TDF or PB flange standard with consistent dimensional tolerances meeting AS/NZS 4254 and SMACNA. For onshore gas projects the SBAL-V is typically configured with a stainless plasma cutter for the slot-and-tab transverse joint and a notch-and-bend station for the TDF flange profile. Cross-reference the SBAL-V product page for full specification.
• SB-ZF1500 automatic stitchwelder. The SB-ZF1500 is SBKJ's automatic longitudinal seam stitchwelder, the critical machine for hazardous-area duct welding because it produces consistent TIG seam welds at production speed with documented weld procedure specifications. For onshore gas, pipeline compressor and LPG service every longitudinal seam is closed on the SB-ZF1500 to AS/NZS 1554.6 with 316L filler. The SB-ZF1500 is also configured for ATEX-rated assembly with controlled heat input to minimise sensitisation in the heat-affected zone and produces the documented weld traceability records that go into the operator's Safety Case.
• SBSF-1525 hydraulic flanging machine. The SBSF-1525 produces 316L stainless round-duct flanges for the round-duct sections of the process extract and supply system. The flange is formed by hydraulic press to a consistent dimensional standard and welded to the duct on the SB-ZF1500.
• SBPC1500 plasma cutter. The SBPC1500 is the plasma cutter for 316L plate cutting at production-grade dimensional tolerance. The plasma cut is used for cutting blanks, openings, branch connections and dimensional details that are not produced on the SBAL-V auto duct line.
• SBLR-600 welder. The SBLR-600 is a longitudinal seam welder used for round duct seam closure and for the smaller-section transitions where the SB-ZF1500 is over-sized for the work envelope. For onshore gas the SBLR-600 supports the gathering compressor station and the LPG cylinder filling shed duct fabrication.
• SBLR-600A aluminium flexible duct forming line. Where present, the SBLR-600A produces aluminium flexible ducts used for kiosk and control-room recirculation connections, accommodation flexibles and ductwork details where rigid duct cannot be installed.
• Spark-resistant fans and IECEx motor sourcing. SBKJ does not directly manufacture spark-resistant fans or IECEx motors — these are sourced from specialist suppliers (typically Howden, Greenheck, COFIMCO, ABB or SEW Eurodrive) and packaged with the SBKJ-fabricated duct as part of the project deliverable. For onshore gas, pipeline compressor and LPG service the fan is AMCA 99 Type B or Type C with the IECEx Ex-d or Ex-e motor matched to the zone.
• Specialist alloy sub-contract for Inconel 625 and other superalloys. Where the duct scope includes severe sour-service sections requiring Inconel cladding (the Moomba SRU and amine regenerator overhead are the typical cases), SBKJ sub-contracts the cladding fabrication to a specialist alloy fabricator while retaining responsibility for the overall scope, integration and documentation.
• FRP/PP duct for primary H2S and amine vapour scrubbers. Where the duct scope includes primary acid-vapour scrubbing (the inlet to a packed scrubber where H2S and amine vapour load is concentrated), fibreglass-reinforced polyester (FRP) or polypropylene (PP) duct may be specified. This material is outside SBKJ's primary metal-duct scope and is sub-contracted to a specialist FRP fabricator with the integration handled by SBKJ engineering.
• AS/NZS 60079, ATEX and IECEx fabrication-shop option. Where the fabrication shop itself is classified as a Zone 22 dust-handling area (because of stainless-steel grinding swarf), the SBKJ machine line is configured with hazardous-area-rated electrical components, anti-static drive belts and bonded earthing throughout. This is the right shop configuration for fabrication shops that operate inside an existing chemical or hydrocarbon site footprint.

Cross-reference the SBKJ machine catalogue for full specification, output and certification details, and the 47-point HVAC duct machine buyer's checklist for the procurement verification questions to ask any vendor.

Project sequencing and lead time

Onshore gas HVAC projects sit on more compressed lead times than their LNG counterparts because the building scope per facility is smaller, but the project count is much higher. A representative schedule for a CSG gathering compressor station HVAC scope from design freeze to first article fabricated is:

• Weeks 1 to 3 — Design and hazard freeze. Hazardous-area classification drawing signed off, dangerous-goods register complete, state petroleum approval document referenced, AS/NZS code applicability matrix complete, single-line ventilation drawing signed off, Safety Case bow-tie linkage documented (where the facility falls under MHF coverage).
• Weeks 3 to 9 — Procurement and material lead. 316L stainless sheet stock ordered to project schedule (lead time 6 to 12 weeks from mill for project tonnages), IECEx fan-and-damper package ordered (lead time 12 to 18 weeks from specialist supplier).
• Weeks 9 to 12 — Fabrication. SBAL-V stainless auto duct line single-shift output is approximately 2,500 m² of duct per week at onshore-gas-grade thickness; a single CSG gathering compressor station HVAC scope (approximately 350 to 450 metres of 316L) fabricates in roughly two to three weeks of shop time. Quality records (welder qualifications, weld procedure specifications, root and visual inspection records, mill certificates) are compiled in parallel.
• Weeks 12 to 15 — Shipment and site delivery. 316L stainless duct shipped flat-packed for site assembly; pre-fabricated welded sections shipped in protective crating with humidity indicators.
• Weeks 15 to 22 — Site assembly, hazardous-area continuity testing, gas-detection commissioning, cause-and-effect matrix witness testing.
• Weeks 22 to 28 — Documentation hand-over to the operator EHS and regulatory audit.

For a mainline compressor station the schedule is similar but the IECEx fan-and-damper package lead time extends because the larger size and higher pressure rating of the compressor enclosure fans have thinner stockholding. For a Moomba-scale CPF upgrade or an LPG terminal expansion the schedule extends to a full LNG-style 24 to 30 weeks because of the Inconel sub-contract lead time and the multi-building scope.

Cost envelope — onshore gas HVAC pricing

A representative cost envelope for onshore gas, pipeline compressor station, LPG terminal and underground gas storage ductwork in 2026 prices (Australian dollars, ex-works fabrication shop, before site installation and commissioning):

• Galvanised steel duct — AUD 70 to AUD 120 per square metre installed, for non-hazardous office, amenity and warehouse areas physically segregated from process.
• 316L stainless duct, TIG-welded, mill-finished — AUD 380 to AUD 620 per square metre installed, for general onshore gas, pipeline and LPG service.
• 316L stainless duct, TIG-welded, electropolished or passivated — AUD 480 to AUD 780 per square metre installed, for severe-service sections at Moomba and the partially-sour Cooper Basin facilities.
• Inconel 625 clad duct — AUD 2,400 to AUD 4,800 per square metre installed, for severe sour-service sections at the Moomba SRU and amine regenerator overhead. Specialist sub-contract.
• FRP/PP duct for primary acid-vapour scrubber inlet — AUD 800 to AUD 1,600 per square metre installed, specialist sub-contract.
• Spark-resistant fan with IECEx Ex-d motor — AUD 18,000 to AUD 65,000 per unit depending on size and zone, sourced through SBKJ from a specialist supplier.
• IECEx Zone 1/2 damper actuator — AUD 2,800 to AUD 9,500 per unit depending on size and torque.

The cost case for designing the network bay-by-bay rather than blanketing the whole project in one alloy is straightforward — the difference between specifying Inconel 625 throughout an 800 m² Moomba SRU duct envelope (AUD 1.9 million to AUD 3.8 million) and specifying 316L for 90 percent and Inconel for 10 percent (AUD 600,000 to AUD 1 million combined) is roughly AUD 1.5 to AUD 3 million of saved capital at no compromise in performance.

Documentation and audit pack

Every onshore gas HVAC project hands over a documentation pack that goes into the site EHS document control system and feeds into the next state petroleum regulator audit or Major Hazard Facility review. The pack contents are:

• Hazardous-area classification drawings (AS/NZS 60079.10.1) signed by the responsible engineer.
• As-built single-line and isometric drawings of the duct network.
• Weld procedure specifications and welder qualification records for every TIG-welded joint under AS/NZS 1554.6 (and ASME Section IX where parent-company alignment requires it).
• Mill certificates for 316L stainless sheet stock, traceable by heat number to each fabricated section.
• Specialist alloy mill certificates for Inconel 625 clad sections (Moomba and the partially-sour Cooper Basin facilities).
• IECEx certificates for every fan, damper actuator, gas detector, motor and electrical accessory inside a hazardous zone.
• AMCA 99 spark-resistant fan documentation.
• Continuity-test records for every duct joint inside a hazardous zone, showing earth resistance below the Safety Case-defined limit (typically 1 Ω).
• Pressure-test records to AS 4254 leakage class C or the project-specified class.
• Cause-and-effect matrix for the gas-detection system showing normal-to-emergency mode transitions.
• Witness-test records for the emergency-mode air-change rate against a simulated gas-detector trip.
• Fire-rated penetration certificates under AS 1530.4.
• Fire damper inspection schedules under AS 1851.
• Operating and maintenance manuals in English including spare-parts lists, lubrication schedules and inspection intervals under AS/NZS 60079.17.
• Cross-references to the operator's Major Hazard Facility Safety Case (Moomba, mainline compressor stations, LPG bulk terminals over the MHF threshold) or the state petroleum approval document (CSG wellheads, smaller compressor stations, LPG terminals below threshold) showing where the ductwork is named as a layer of protection in bow-tie analyses.
• For pipeline facilities — additional documentation for AS 2885 pipeline safety case compliance.
• For LPG bulk and cylinder facilities — additional documentation for AS/NZS 1596 compliance including separation distance survey, IECEx equipment selection rationale and vapour recovery design basis.

SBKJ supplies the as-built, weld and material documentation for the SBKJ scope; the IECEx, hazardous-area classification and Safety Case integration documents are supplied by the principal designer or the site EHS team. The interface is defined at project award and walked through at the project pre-start meeting.

Industry bodies and the Australian engagement map

The Australian onshore gas industry is represented by a network of industry bodies that publish guidance, set standards and engage with the regulator on behalf of operators. Engagement with these bodies is part of the long-term commercial development for any fabricator or supplier into the sector:

• APPEA — Australian Petroleum Production and Exploration Association. The peak body for the upstream oil and gas industry in Australia, covering CSG, conventional gas, offshore production and LNG. APPEA hosts an annual conference that is the primary networking and policy forum for the sector.
• APGA — Australian Pipelines and Gas Association. The peak body for transmission pipeline operators and the gas pipeline construction industry. APGA publishes guidance referenced alongside AS 2885 (Pipelines — Gas and Liquid Petroleum) that connects pipeline design to facility design.
• AEMO — Australian Energy Market Operator. The regulator and market operator for the eastern Australian gas and electricity markets. AEMO publishes the Gas Statement of Opportunities and the Victorian Gas Planning Report that map the supply-demand balance.
• Australian Energy Council (AEC). The peak body covering the gas-and-electricity downstream — particularly the gas distribution and gas retail side.
• Energy Networks Australia (ENA). The peak body for gas and electricity distribution networks.
• ARPC — Australian Reinsurance Pool Corporation. Related to the Major Hazard Facility insurance environment.

Operator base — Australian onshore gas

The Australian onshore gas operator base in 2026 is dominated by the integrated CSG-to-LNG operators in Queensland plus the conventional gas operators across the southern states:

Coal seam gas operators

• Shell QGC (Queensland Gas Company) — Surat Basin biggest. Acquired by Shell in 2016 when Shell bought BG Group.
• Origin Energy (ASX:ORG) — Surat Basin, Australia Pacific LNG operator with ConocoPhillips.
• Santos (ASX:STO) — Cooper Basin operator, Gladstone LNG (GLNG) operator, Narrabri NSW CSG operator.
• Senex Energy — acquired by POSCO International, Hancock Energy and Korea Gas in 2022. Surat Basin operator.
• AGL Energy (ASX:AGL) — gas customer, not producer.

Cooper Basin operators

• Santos — operator of the Moomba complex.
• Beach Energy (ASX:BPT) — Cooper Basin and Otway Basin.
• Cooper Energy (ASX:COE) — Otway Basin and Cooper Basin.

Otway Basin and Bass Strait operators

• ExxonMobil + Santos — Gippsland Basin Bass Strait operators.
• Beach Energy — Otway Basin.
• Cooper Energy — Otway Basin offshore and onshore.
• Lochard Energy — Iona Gas Plant operator.

Perth Basin and Western Australia onshore

• Strike Energy (ASX:STX) — Perth Basin operator.
• Carnarvon Energy (ASX:CVN) — Carnarvon Basin operator.

Mainline pipeline operators

• APA Group (ASX:APA) — biggest gas transmission operator in Australia. Owns the East Australian Gas Pipeline (EGAPL), Moomba-Sydney Pipeline, Roma-Brisbane Pipeline, QSN3 Queensland-NSW Interconnect, Carpentaria Gas Pipeline and others.
• Jemena — Singapore Power and State Grid Corporation joint owners. Owns NSW gas distribution, Northern Territory Gas Pipeline and Queensland Gas Pipeline.
• AusNet Services — Brookfield-owned. Operates the Victorian gas transmission network and the Victorian electricity transmission network.
• AGN Australia Gas Networks — Brookfield and Hastings joint owners. Distribution networks across SA, VIC and QLD.
• Energex / Energy Queensland — Queensland electricity and gas distribution.
• ATCO Australia — WA gas distribution.
• AusGrid and Endeavour Energy — NSW electricity and gas distribution.

LPG operators

• Elgas (Origin) — biggest LPG distributor in Australia, national footprint.
• Origin Energy LPG — Origin's broader LPG operations.
• Kleenheat Gas (Wesfarmers Chemical, Energy and Fertilisers) — WA LPG distributor.
• Mogas Regional — regional LPG and petrol distributor.
• Beach Energy — LPG production and sales from Cooper Basin fractionation.
• BP Australia — LPG forecourt and retail.
• Manuka Resources — LPG and petrol.

Underground gas storage operators

• Lochard Energy — Iona Gas Plant, Victoria.
• Newport Gas Storage — Victoria.
• Ironbark Gas Storage — Queensland.
• Calliope Gas Storage — Queensland.

EPC contractor base — onshore gas projects

The EPC contractor base for Australian onshore gas, pipeline compressor station, LPG and underground gas storage is a small group of internationally-experienced firms with established Australian operations:

• Worley (ASX:WOR) — Brisbane and Perth offices, the largest Australian gas EPC firm.
• Bechtel Australia — significant onshore CSG-to-LNG and gas plant footprint.
• Saipem Australia — pipeline and onshore facilities.
• Monadelphous (ASX:MND) — Pilbara, CSG and pipeline construction.
• McConnell Dowell — pipeline and facilities.
• John Holland — civil and pipeline construction.
• BMD Constructions — pipeline and facility civil works.
• Civmec (ASX:CVL) — heavy fabrication and construction services.
• Fluor Australia — gas and downstream EPC.
• KBR Australia — engineering services.

SBKJ engages with this EPC base through the partner fabricators in the Brisbane, Toowoomba, Roma, Sydney, Newcastle, Wollongong, Adelaide, Melbourne and Perth corridors that operate SBKJ equipment, and through direct engineering pre-construction support to consulting engineers and project teams. For trade-show engagement the Australia Ducting Pty Ltd presence at ARBS 2026 (exhibition ID 236) is the front face of the SBKJ commercial engagement with the Australian buying market.

How SBKJ supports Australian onshore gas projects

SBKJ Group has supplied HVAC duct fabrication equipment to onshore gas, pipeline compressor station, LPG terminal and underground gas storage projects across 100+ countries. The Australian footprint runs through the SBKJ office in Box Hill North VIC for English-speaking after-sales, project engineering and spare-parts support, and through the Australia Ducting Pty Ltd presence as the local trade-show face at events including ARBS 2026. For onshore gas projects we typically engage at one of three project phases:

• Design support. Pre-construction review of the duct material, joint, fan and damper scope against AS/NZS, NFPA, API and ISO references — usually as an unpaid courtesy to architects and consulting engineers who are sizing the fabrication-shop footprint.
• Shop equipment supply. Supply of the SBAL-V stainless auto duct line, SB-ZF1500 automatic stitchwelder, SBSF-1525 hydraulic flanging machine, SBPC1500 plasma cutter, SBLR-600 welder and ancillary handling equipment to a buyer fabricating duct in their own shop. Lead time 18 to 26 weeks; on-site commissioning by SBKJ engineers from the Box Hill North office.
• Toll fabrication via partners. For projects where the buyer prefers to procure duct directly rather than fabricate in-house, SBKJ partners with Australian fabrication shops that operate SBKJ equipment in the Brisbane, Toowoomba, Roma, Sydney, Newcastle, Adelaide, Melbourne and Perth areas.

Cross-reference the why choose SBKJ summary, the SBKJ machine catalogue, the SBAL-V product page, the pricing and lead time guide and the 47-point HVAC duct machine buyer's checklist. For related industry guides see the LNG, gas processing, oil refinery, petrochemical and offshore platform HVAC duct guide, the coal and gas power plant HVAC duct guide, the hydrogen production, electrolyser, ammonia and H2 refuelling HVAC duct guide, the specialty chemicals, petrochemical, agrochemical and industrial gas HVAC duct guide and the underground mine, coal, hardrock ventilation, refuge and fan station HVAC duct guide.

Get an onshore-gas-grade HVAC duct quote from SBKJ →

FAQ

What ductwork material is required for an Australian coal seam gas wellhead facility?

316L stainless steel is the default specification for above-ground building envelopes at Australian coal seam gas wellheads — the dewatering pump shelter, the separator and dehydration shed, the wellhead control kiosk and the gas gathering manifold building. The driver is the combined exposure to methane vapour, formation water (high salinity from the Walloon coal measures and Bandanna formation), trace H2S in some Bowen Basin and Surat Basin wells, and the long humid wet season in southern Queensland. Galvanised duct can be tolerated only in segregated non-hazardous administrative buildings physically offset from the wellhead pad. The SBAL-V stainless auto duct line and the SB-ZF1500 stitchwelder are the SBKJ machine configuration used to fabricate the 316L rectangular and round duct envelope for these wellhead facilities.

What hazardous-area zone classification applies at a CSG wellhead and gathering compressor?

AS/NZS 60079.10.1 applies throughout. The wellhead Christmas tree fitting envelope is Zone 1 within approximately 1.5 metres of the fittings and Zone 2 to approximately 4.5 metres. The gas gathering manifold is Zone 1 immediately around vent points and Zone 2 across the shelter envelope. The low-pressure CSG gathering compressor enclosure is Zone 2 by dilution-ventilation classification provided continuous mechanical ventilation maintains at least 6 to 12 air changes per hour; if ventilation is lost it reverts to Zone 1. The high-pressure mainline compressor station downstream is similarly Zone 2 by dilution ventilation with 12 air changes per hour minimum. Control kiosks, telemetry shelters and substation buildings are pressurised non-hazardous under AS/NZS 60079.4.

How sour is Australian coal seam gas and does it need ISO 15156 NACE materials?

Most Australian coal seam gas is sweet — the Walloon coal measures in the Surat Basin and the Bowen Basin coals produce gas with H2S typically below 4 ppm in the raw stream, well below the ISO 15156 NACE MR0175 trigger of 0.0003 MPa partial pressure for sour-service material selection. The Narrabri Project gas in NSW is similarly sweet. Cooper Basin gas, by contrast, is partially sour — sections of the Toolachee and Patchawarra fields carry H2S at concentrations that do trigger NACE MR0175 sour-service material selection on the wet gas side. Bass Strait onshore receiving gas from the Gippsland Basin is sweet. The duct specification reflects this: 316L stainless everywhere for general service plus localised Inconel 625 cladding only on the wet H2S extract sections at Moomba and the partially-sour Cooper Basin facilities.

What ventilation rate applies to a CSG gathering compressor station?

AS 1668.2 sets the baseline and AS/NZS 60079.10.1 sets the hazardous-area trigger. For a CSG low-pressure gathering compressor enclosure the design rate is 6 to 10 air changes per hour on normal operation to maintain Zone 2 dilution-ventilation classification, stepping to 30 air changes per hour on methane detection at 20 percent LEL. For the high-pressure mainline compressor station downstream the rate is 12 air changes per hour minimum on normal operation, stepping to 30 air changes per hour on emergency. Fans are spark-resistant under AMCA 99 Type B or C with IECEx Ex-d or Ex-e motors. Ductwork is 316L stainless throughout with continuity-tested earthing across every joint.

What standards apply to an Australian LPG bulk terminal and cylinder filling plant?

AS/NZS 1596 (Storage and handling of LP Gas) is the primary Australian standard governing LPG bulk storage, decanting, cylinder filling and dispensing. AS 5601 (Gas installations) governs the LPG installation downstream of the cylinder or bulk tank. AS 4332 (Storage and handling of gases in cylinders) covers cylinder racking and storage. AS 4838 covers LPG cylinders for decanting. AS/NZS 60079.10.1 classifies the hazardous-area zones — typically Zone 1 within 1.5 metres of any pressurised fitting or vent point and Zone 2 to 4.5 metres. NFPA 58 and NFPA 59 are the American equivalents commonly referenced in Australian project Safety Cases. The duct envelope around an LPG bulk terminal is 316L stainless on the outside-air run for control rooms, instrument shelters and operator buildings, with localised Zone 1 IECEx-rated fans for any cylinder filling shed extract and spark-resistant fans for any vapour-recovery extract.

How is HVAC designed for an underground gas storage facility?

Australian underground gas storage is in depleted reservoirs (Iona Gas Plant in Victoria, the Newport Gas Storage in Victoria, the Ironbark Gas Storage in Queensland) and one operating salt cavern proposal. The HVAC scope is centred on the surface compressor and control facilities — every storage cycle requires high-pressure injection and withdrawal compressors, dehydration to remove formation water, separation and metering. The wellhead area on the storage site is Zone 1 within 1.5 metres of fittings and Zone 2 to 4.5 metres. The compressor enclosure is Zone 2 by dilution ventilation. Control kiosks and substations are pressurised non-hazardous. Duct material is 316L stainless throughout because the site sits in a continuous methane vapour exposure envelope with formation water that may carry corrosive products from the underlying reservoir.

Which Australian operators source HVAC duct equipment for onshore gas, pipeline and LPG facilities?

SBKJ supplies HVAC duct machinery to fabrication shops servicing Australian onshore gas, pipeline compressor station, LPG terminal and underground gas storage projects through partner fabricators in the Brisbane, Toowoomba, Roma, Sydney, Newcastle, Wollongong, Adelaide, Melbourne and Perth corridors. The operator base includes Origin Energy and APLNG, Santos at the Cooper Basin and Narrabri, Shell QGC, Senex Energy, Beach Energy at Cooper and Otway, Cooper Energy, ExxonMobil Bass Strait, APA Group as the mainline transmission operator, Jemena, AusNet Services, AGN Australia Gas Networks, ATCO, Elgas (Origin), Kleenheat Gas, Mogas Regional and the EPC contractor base including Worley, Bechtel, Saipem, Monadelphous, McConnell Dowell, John Holland and BMD Constructions. SBKJ engineers specify the SBAL-V, SB-ZF1500, SBSF-1525, SBPC1500 and SBLR-600 configuration for each project.