Coal-Fired Power Station, Gas-Fired CCGT & OCGT, Combined Cycle, Snowy 2.0 Pumped Hydro, Kidston Genex & Thermal Power Generation HVAC Duct Guide

Coal-fired power station HVAC duct — the broadest single industrial brief in Australian engineering

Of the heavy industrial verticals that cross the Box Hill North desk, the combined thermal power generation brief — coal-fired, gas-fired, combined cycle, pumped hydro and co-located battery storage — is the broadest in code overlap, the most dispersed in geography across the Australian National Electricity Market, and the most consequential to the country's energy transition. A single coal-fired station such as AGL's Bayswater NSW or Origin's Eraring NSW will run multiple kilometres of HVAC ductwork through coal handling, pulverised fuel coal mill, boiler house, hydrogen-cooled turbine generator, flue gas desulphurisation, selective catalytic reduction, activated carbon injection, fly ash silo and 200-metre stack, with material specifications ranging from heavy-gauge galvanised on the coal handling extract to 316L stainless on the FGD outlet wet acid stack to Inconel and Hastelloy on the boiler bundle at 540 to 600 degrees C. Get the duct gauge wrong on the pulverised fuel extract and a coal mill explosion vent does not function as designed under NFPA 68. Get the stainless grade wrong on the SCR ammonia injection skid and the catalyst is poisoned within twelve months by chloride breakthrough. Get the hydrogen generator purge vent route wrong and the AS/NZS 60079 Class I Zone 1 IIC classification fails IECEx CoPC audit, blocking commissioning. Get the BESS thermal-runaway extract wrong and the AEMO Frequency Control Ancillary Services contract is non-deliverable because the battery thermal interlock will not arm.

Layer the regulatory framework over the engineering and the brief deepens further. The NER National Electricity Rules administered by AEMC drive the dispatch reliability requirement that the control room HVAC has to support; the AEMO Grid Code adds the Network Operating Plan obligations that determine the redundancy specification; the AER audits the cost-recovery framework; the CER administers the Renewable Energy Target and the National Greenhouse and Energy Reporting NGER scheme; the ESB Energy Security Board coordinates the integrated system plan; the AEC peak body, APPEA and Australian Coal Association ACA contribute the industry-body view; and the state environmental authorities — NSW EPA under POEO, VIC EPA, QLD DES, SA EPA, WA DWER — each administer the stack emission licence with continuous emission monitoring of mercury, sulphur dioxide, nitrogen oxides, carbon monoxide, particulate matter, hydrogen chloride and hydrogen fluoride. ARPANSA RPS 9 covers Naturally Occurring Radioactive Material (NORM) which is present in measurable concentration in fly ash and bottom ash because coal contains trace uranium, thorium and potassium-40 isotopes that concentrate during combustion. Safe Work Australia workplace exposure standards govern the personnel exposure envelope and the Queensland and New South Wales Coal Workers Pneumoconiosis Black Lung Royal Commission of 2018 introduced tightened respirable coal dust monitoring requirements that have changed the local exhaust ventilation design baseline at every coal handling area in Australia.

This guide walks through what a consulting engineer, IECEx CoPC hazardous area auditor, mechanical contractor or asset owner has to decide when specifying HVAC ductwork across this full thermal power vertical. It is written from the practitioner's standpoint and referenced against the AGL, Origin, EnergyAustralia, Stanwell, CS Energy, Snowy Hydro, Hydro Tasmania, Synergy WA, Genex Power and Neoen project base that defines the operating Australian fleet in May 2026, with the construction-phase Snowy 2.0 and Kurri Kurri projects providing the leading edge of new-plant scope and the Liddell and Wallerawang decommissioning projects providing the trailing edge of asbestos abatement and brownfield BESS conversion.

Bayswater, Eraring and Loy Yang — the biggest coal-fired operators

The first input to any HVAC specification is which operator is delivering the project, because each Australian thermal power operator has its own engineering standards, preferred consulting engineers, preferred mechanical contractors and historical baseline of duct specification practice that any new project sits on top of.

AGL Energy and Bayswater plus Loy Yang A

AGL Energy (ASX:AGL) is Australia's largest coal-fired generator by both capacity and CO2 emissions. The headline assets are Bayswater Power Station in the Upper Hunter region of NSW (four 660 MW black coal subcritical units totalling 2,660 MW, commissioned 1985 to 1986, closure scheduled mid-2030s) and Loy Yang A in the Latrobe Valley region of VIC (four units totalling 2,210 MW brown coal subcritical, commissioned 1984 to 1988, closure scheduled mid-2030s). Liddell Power Station in NSW (four 500 MW black coal units) was closed in 2023 with substantial asbestos legacy lagging requiring AS 2601 demolition standards and AS 4254 ductwork replacement during the decommissioning works. AGL's transition portfolio includes the Liddell BESS (commissioned 2024 on the closed Liddell site), the Torrens Island Big Battery in SA (250 MW co-located with the legacy Torrens Island gas station), the planned Loy Yang battery, and the Hunter Valley pumped hydro feasibility studies. Bayswater HVAC scope follows the GE-Westinghouse-Toshiba legacy turbine-generator baseline with hydrogen-cooled generators classified Class I Zone 1 IIC, vertical roller coal mills with NFPA 60 PF protection, an FGD retrofit study in early stages, and the 200-metre brick stack continuous emission monitoring reporting to NSW EPA under POEO.

Origin Energy and Eraring

Origin Energy (ASX:ORG) operates Eraring Power Station on the Central Coast of NSW — four 720 MW black coal subcritical units totalling 2,880 MW, originally commissioned 1981 to 1984. Eraring is Australia's largest single power station by capacity, larger than any AGL or EnergyAustralia coal-fired site. Closure was originally scheduled for August 2025 but was extended on a NSW state government underwrite arrangement to 2027 to manage the grid transition. Origin's Eraring battery project is now operating at 460 MW first phase (commissioned 2024) with planned expansion to 700 MW and 2,800 MWh which will be Australia's largest single battery installation. Origin also operates the Mortlake gas-fired CCGT in VIC (566 MW), the Quarantine OCGT peaking station in SA, and held a stake in the Australia Pacific LNG joint venture in Queensland with the operating LNG export trains generating substantial natural gas demand. Eraring's HVAC inventory spans the coal handling and stockpile precinct (travelling stacker and reclaimer, enclosed conveyors at AS 3957 Zone 21/22 coal dust hazard), the coal mill enclosure (four vertical roller mills per unit, NFPA 60 PF protection), the boiler house (subcritical wall-fired, 540 degrees C, 200 bar), the turbine hall, the hydrogen-cooled generator (Class I Zone 1 IIC, photoacoustic H2 leak detection at ceiling level), the natural-draft cooling tower precinct (AS/NZS 3666 Legionella program), the ESP and ash handling, the 200-metre stack with CEM, and the new co-located 460 MW BESS commissioned 2024 with planned expansion to 700 MW.

EnergyAustralia and Yallourn plus Mt Piper

EnergyAustralia operates Yallourn Power Station in VIC (four units totalling 1,480 MW brown coal, scheduled closure 2028) and Mt Piper Power Station in NSW (two 700 MW black coal units totalling 1,400 MW, scheduled closure mid-2040s). The Wallerawang Power Station NSW (closed 2014, demolished 2018) hosts an EnergyAustralia BESS conversion project. The Yallourn battery is planned at 350 MW co-located on the Yallourn site. The Hallett Power Station SA (180 MW OCGT peaking gas) and the Tallawarra A and B stations NSW (combined CCGT capacity at 800 MW with Tallawarra B at 320 MW commissioned 2023 as the first new gas peaking station for a decade) complete the EnergyAustralia generation portfolio. Yallourn brown-coal HVAC has the particular characteristic that brown coal has lower calorific value (typically 9 to 10 MJ/kg as-fired versus 22 to 28 MJ/kg for black coal), which drives larger boiler and mill physical scale per MW of output and a substantially larger pulverised fuel inventory at the coal mill enclosure — all sized on the NFPA 60 and AS 3957 framework.

Stanwell Corporation Queensland and Tarong plus Kogan Creek

Stanwell Corporation (QLD government-owned) operates Stanwell Power Station near Rockhampton QLD (four 360 MW black coal subcritical units totalling 1,460 MW), Tarong Power Station near Kingaroy QLD (four 350 MW black coal subcritical units, with Tarong North being a single 443 MW supercritical unit commissioned 2003), and Kogan Creek Power Station near Chinchilla QLD (single 750 MW supercritical unit commissioned 2007). Kogan Creek is Australia's largest single coal-fired generating unit and one of only a handful of supercritical operating units, running 600 degrees C superheat at 250 bar pressure with correspondingly higher-grade boiler tube material specifications. Stanwell's transition portfolio includes proposed pumped hydro feasibility at the Tarong site, hydrogen-ready gas turbine studies and several large-scale solar and wind investments through the CleanCo state-owned partnership.

CS Energy Queensland and Callide

CS Energy (QLD government-owned) operates Callide B Power Station (two 350 MW black coal units) and Callide C Power Station (two 420 MW supercritical units, joint venture with IGES). The Callide C unit 4 catastrophic failure of May 2021 — a thrust bearing failure that damaged the generator and turbine — required substantial rebuild and was reflective of the increasing maintenance demands on the legacy coal fleet. CS Energy's transition includes the proposed Brigalow Peaking Plant (gas OCGT) and several solar and BESS investments through the CleanCo partnership.

Snowy Hydro and the Snowy 2.0 pumped hydro plus Kurri Kurri gas peaking

Snowy Hydro Limited (Commonwealth Government-owned) operates the existing Snowy Mountains Scheme conventional hydro at Tumut 1, 2 and 3, Murray 1 and 2, Guthega, Blowering and Burrinjuck (combined 4,100 MW) plus the under-construction Snowy 2.0 pumped hydro storage at 2 GW nameplate and 175 GWh of stored energy. Snowy Hydro also operates the Hunter Valley gas peaking precinct at Colongra and is constructing the Kurri Kurri gas peaking power station in the Hunter region NSW (660 MW OCGT, hydrogen-ready capable, planned commissioning 2026). The Reeves Plains pumped hydro feasibility study in SA is an additional Snowy Hydro development. Snowy 2.0 is the largest single HVAC scope in Australian power generation history — several thousand linear metres of large-diameter spiral round duct on the SBKJ SBTF-2020, hundreds of fire dampers, dual-redundant AHU plant in the cavern, and surface fan houses at Tantangara, Talbingo and the main access tunnel portals — all delivered by the Salini Impregilo Webuild Future Generation Joint Venture FGJV with Lendlease and Webuild as the EPC.

Hydro Tasmania and Synergy WA

Hydro Tasmania is the Tasmanian state-owned operator of the largest renewable energy fleet in Australia by name-plate capacity — approximately 2,600 MW of hydroelectric across 30-plus stations including Bell Bay (gas-fired backup), Tarraleah, Trevallyn, Lake Gordon and Cethana. Hydro Tasmania has announced the 750 MW Cethana Pumped Hydro Project and the Tarraleah pumped storage redevelopment as part of the Battery of the Nation portfolio targeting interconnection with mainland Australia through the Marinus Link HVDC cable. Synergy WA operates the Muja and Collie Power Stations (combined 1,660 MW black coal) in the South West Interconnected System (SWIS), with closure timelines through the late 2020s and early 2030s.

Genex Power and Kidston Pumped Hydro

Genex Power (ASX:GNX) is developing the 250 MW Kidston Pumped Hydro Project in North Queensland, using two existing open-cut mine voids at the former Kidston gold mine as the upper and lower reservoirs. Kidston is the first new Australian pumped hydro project to reach construction phase and is the flagship project for the Northern Queensland Renewable Energy Zone. The Kidston Hybrid (50 MW solar plus 250 MW pumped hydro plus 100 MW solar farm and 250 MW BESS planned) is the integrated portfolio model that Genex has developed.

Pulverised fuel coal mill HVAC and NFPA 60 dust extraction

For coal-fired power stations the coal mill enclosure and the pulverised fuel pipework are the dominant hazardous-area HVAC scope. Each generating unit typically has four to eight coal mills (ball-and-race type at older subcritical stations such as Bayswater, vertical roller mill type at newer supercritical stations such as Kogan Creek and Tarong North) that grind raw coal from the bunker to pulverised fuel at 70 percent finer than 75 micrometre particle size. The classifier above each mill recirculates oversize coal back to the grinding bed; the underflow is pneumatically conveyed under primary air at 60 to 80 degrees C through pulverised fuel pipework directly to the burner front.

Hazardous area classification Zone 21 and Zone 22

The pulverised fuel system is classified Zone 21 inside the mill enclosure and during pneumatic conveying — dust cloud present continuously or for long periods during normal operation. The surrounding coal mill house is classified Zone 22 — dust cloud occasionally during fugitive emission. Coal dust Kst is typically 100 to 250 bar.m/s as tested per the modified Hartmann tube method, placing coal dust in the St2 hazard class under AS 3957 and IEC 80079-20-2. Minimum ignition energy of fine coal dust is typically 30 to 100 mJ — within the easy ignition range of any static discharge, hot surface or arcing electrical contact.

NFPA 60 and NFPA 654 design framework

NFPA 60 (Standard for the Installation and Use of Stationary Pulverised Fuel Systems) sets the design requirements for PF systems including the minimum fuel-to-air ratio safety margins (typically the air-to-fuel mass ratio is held at 1.5 to 1.8 to keep the PF mixture above the upper explosive limit during normal conveying), the burner-front trip logic and the explosion-protection design. NFPA 654 (Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing and Handling of Combustible Particulate Solids) covers combustible dust deflagration more generally and is referenced under NFPA 850. NFPA 68 (Standard on Explosion Protection by Deflagration Venting) sets the deflagration vent area calculation, typically requiring 1 to 2 m2 of vent area per 10 m3 of enclosure volume for coal dust at St2 hazard class. NFPA 69 (Standard on Explosion Prevention Systems) covers inerting (typically nitrogen blanket on idle mills, oxygen content held below 8 percent during shutdown) and explosion isolation (chemical isolation barriers, fast-acting valves, or rotary airlocks preventing flame propagation upstream and downstream of the protected vessel).

Local exhaust ventilation and the CWP Black Lung response

The Queensland Coal Workers Pneumoconiosis Royal Commission of 2018 changed the local exhaust ventilation (LEV) design baseline at every coal handling area in Australia. The Commission found that workplace exposure to respirable coal dust above the Safe Work Australia 1.5 mg/m3 8-hour TWA had occurred at several Queensland coal mines and that the regulatory regime had failed to detect and prevent ongoing exposure. The Commission's recommendations tightened the respirable coal dust exposure standard, introduced mandatory periodic respiratory medical examinations through the Coal Mine Workers' Health Scheme administered by Resources Safety and Health Queensland (RSHQ) and the corresponding NSW Resources Regulator scheme, required occupational hygiene measurement on a continuous statistical basis, and required mandatory respirable crystalline silica monitoring at 0.05 mg/m3. For coal-fired power stations, the practical impact on HVAC duct specification is that LEV at every coal transfer point, every coal mill loading point and every PF pipework connection must be sized to maintain respirable coal dust below 0.5 mg/m3 in the worker breathing zone (one-third of the WES, providing a safety margin), with capture velocities of 1 to 2 m/s at the source.

Duct material and the SBKJ machine selection

LEV ductwork on the coal mill enclosure is heavy-gauge galvanised on the SBKJ SBFB-1500 or SBTF-2020 at 1.5 to 2.0 mm wall thickness, with grounding and bonding at every duct segment per AS 1020 and AS/NZS 60079.14. Heavier-gauge fabrication where the duct service runs above 2,500 Pa internal pressure or the structural reinforcement demand exceeds the SBAL-V envelope uses the SBKJ SBAL-III. The dust collection system terminates at a dedicated baghouse or ESP upstream of any discharge to atmosphere; the baghouse collected dust is reintroduced to the PF burner feed where possible to maximise calorific recovery and minimise hazardous waste disposal. Explosion-vented panels at every coal mill housing per NFPA 68 are factory-mounted in the mill OEM scope rather than the SBKJ duct scope; chemical isolation barriers per NFPA 69 are similarly OEM scope but the duct upstream and downstream of the barriers is SBKJ scope.

Boiler, HRSG and superheater HVAC at 540 to 1,200 degrees C

The boiler at a coal-fired or gas-fired thermal power station is the heart of the steam cycle. Subcritical boilers operate at 540 degrees C superheat and 200 bar pressure; supercritical at 600 degrees C and 250 to 280 bar; ultra-supercritical (no operating Australian examples to date but referenced in several feasibility studies) at 600 to 620 degrees C and 300 bar plus. Boiler firing configurations include wall-fired (most Bayswater and Eraring units), tangential-fired (corner-burner arrangement, used at several Tarong and Stanwell units), and down-fired (specialty configurations at a small number of units). The boiler island typically includes the water-cooled membrane walls, the superheater stages, the reheater, the economiser and the air heater, all in a single fire-rated enclosure.

AS 4036 and AS 4037 pressure vessel design

AS 4036 covers the design, fabrication and inspection of boiler pressure parts and AS 4037 covers in-service inspection of pressure vessels. The HVAC engineer's interaction with the boiler enclosure is at the boiler house ventilation supply and the boiler-bundle adjacent extract — the supply provides combustion air to the burners (typically 30 to 50 m3/s per 100 MW of boiler thermal capacity) and the extract removes radiant heat from the boiler exterior surface. Boiler house ventilation runs at 4 to 6 ACH baseline rising to 8 to 12 ACH during summer peak ambient. Material specification on the boiler house supply is galvanised on the SBKJ SBAL-V at 1.0 to 1.2 mm thickness; material on the bundle-adjacent extract is 304H or 309S stainless because the radiant heat plus trace flue gas contamination attacks galvanised within a few years.

Combined cycle HRSG at 540 to 600 degrees C

Combined Cycle Gas Turbine (CCGT) plants such as Origin Mortlake VIC, EnergyAustralia Tallawarra B NSW and AGL Torrens Island SA include a Heat Recovery Steam Generator (HRSG) downstream of the gas turbine exhaust to capture waste heat at 600 degrees C and convert it to steam for a downstream steam turbine cycle. The HRSG bundle operates at 540 to 600 degrees C steam at the high-pressure superheater outlet and is fabricated in 309S, 310S or Inconel material grade depending on the specific tube row temperature. The HVAC scope at the HRSG includes the boundary ventilation around the HRSG enclosure (galvanised on the SBAL-V at 1.0 mm), the gas turbine inlet filter house (galvanised at 1.0 mm), the gas turbine enclosure ventilation (Class I Zone 1 IIA natural gas, NFPA 70 NEC, AS/NZS 60079), and the steam turbine hall (similar to the conventional coal-fired turbine hall HVAC).

Gas turbine combustor at 1,200 to 1,500 degrees C

The gas turbine combustor — the firing chamber where natural gas mixes with compressed air and combusts to drive the turbine — operates at 1,200 to 1,500 degrees C combustion temperature on modern frames including the GE Vernova 7HA and 9HA, the Mitsubishi M501J and M701F, and the Siemens SGT-A35, SGT-A65 and SGT-800. The combustor itself is built in ceramic-coated Inconel and Hastelloy materials by the OEM and is outside the SBKJ HVAC duct scope. The HVAC engineer's interaction is at the gas turbine enclosure ventilation (the surrounding enclosure that contains the entire gas turbine package), the exhaust duct from the combustor outlet to the HRSG inlet (typically refractory-lined steel rather than HVAC duct), and the bypass stack used during HRSG outage or commissioning. NFPA 86 (Standard for Ovens and Furnaces) is the international reference for the combustor design; AS/NZS 60079 Class I Zone 1 IIA applies to the natural gas fuel side of the gas turbine enclosure.

NFPA 850 and NFPA 86 framework

NFPA 850 (Fire Protection for Electric Generating Plants) is the international reference adopted by most Australian operators under contractual reference. It references back to NFPA 70 NEC for electrical, NFPA 60 for pulverised fuel, NFPA 86 for industrial furnace and boiler, NFPA 654 for combustible dust, NFPA 68 and 69 for deflagration vent and inerting, and AS 1530.4 for fire-rated duct penetration testing. NFPA 850 sets the fire compartment strategy, the smoke control intent, the deluge and dry-pipe sprinkler requirements at transformer pits and turbine lube-oil reservoirs, the fire detection coverage at every operational area, and the fire-rated wall and floor crossings throughout the plant.

Steam turbine hall and hydrogen-cooled generator at Class I Zone 1 IIC

The steam turbine at a thermal power station converts the high-pressure superheated steam from the boiler or HRSG into mechanical rotation that drives the generator. Modern Australian thermal power plants use Siemens, GE, Mitsubishi or legacy Alstom steam turbines on a single shaft with multiple cylinders — typically a high-pressure (HP) cylinder, an intermediate-pressure (IP) cylinder and one or two low-pressure (LP) cylinders, with steam reheat between HP and IP and progressive expansion through to the LP exhaust at the condenser. Turbine inlet steam conditions at modern Australian plants are 540 to 600 degrees C and 200 to 280 bar; the LP exhaust enters the condenser at near-vacuum 5 to 10 kPa absolute. The turbine hall surrounds the entire turbine plus the directly coupled generator.

Turbine hall HVAC sizing

Turbine hall ventilation is sized on heat removal from the turbine bearing oil coolers, the generator stator windings, the exciter, the turbine surface radiant heat and the lube oil reservoir. Total heat load is typically 1 to 2 percent of nameplate generation capacity dissipated to the hall — for a 660 MW Bayswater unit that is 6.6 to 13 MW of continuous heat. Hall ventilation runs at 4 to 6 ACH baseline rising to 8 to 12 ACH during summer peak. Material specification on the turbine hall is galvanised on the SBKJ SBAL-V at 1.0 to 1.2 mm thickness for the supply and 304L stainless on the SBAL-V stainless configuration at 0.8 to 1.0 mm for the bearing-oil-pit-adjacent extract where trace oil aerosol attacks galvanised over a 5 to 8 year horizon.

Hydrogen-cooled generator and Class I Zone 1 IIC classification

Large thermal power station generators above approximately 700 MW capacity — including the Siemens, GE, Toshiba and Westinghouse units at Bayswater, Eraring, Loy Yang A, Yallourn, Mt Piper and Stanwell — use hydrogen as the internal cooling medium rather than air. Hydrogen has approximately 7 times the heat capacity of air at the same density and a viscosity about half that of air, which allows substantially higher generator power density and substantially lower windage losses on the generator rotor. Hydrogen inventory in a large generator is typically 50 to 200 kilograms at 3 to 5 bar internal pressure. The generator enclosure interior and the immediate purge gas vent paths are classified AS/NZS 60079 Class I Zone 1 IIC because hydrogen LEL is 4 percent volume in air, autoignition temperature is 500 degrees C and minimum ignition energy is 0.017 mJ (the lowest of any common gas — even a small static discharge can ignite a hydrogen-air mixture).

Hydrogen leak detection and purge

Hydrogen leak detection uses photoacoustic or catalytic-bead H2 sensors at ceiling level (hydrogen relative density is 0.0695 — it rises rapidly), with first alarm at 1 percent volume (25 percent LEL) triggering ventilation boost and second alarm at 2 percent volume (50 percent LEL) triggering grid-side trip and emergency hydrogen purge using inert nitrogen. Purge gas vents through dedicated 316L stainless ductwork on the SBKJ SBSF-1525 stitchwelder line with continuous longitudinal seam closure, routed to a tall surface stack discharging well clear of any HVAC fresh air intake and any ignition source. NFPA 2 (Hydrogen Technologies Code) is the international reference. AS/NZS 60079 Zone 1 spark-resistant fan housings are mandatory on the purge exhaust path. The hydrogen system also requires inert nitrogen scavenge during fill, purge and de-fill operations, plus carbon dioxide as the intermediate inert during gas changeover from air to hydrogen at first commissioning and at any major outage.

Hydrogen-ready future gas turbines

The Snowy Hydro Kurri Kurri OCGT under construction in 2026 is specified as hydrogen-ready, meaning the gas turbine combustor and the fuel supply system are capable of operation on a hydrogen-natural-gas blend ranging from 5 percent to 30 percent hydrogen by volume initially, with future capability for 100 percent hydrogen operation. The GE Vernova 7HA and Mitsubishi T-Point platforms support this hydrogen capability. AGL, Origin and Stanwell are studying hydrogen-ready conversions at several other future-gas-peaking sites under the Future Energy framework. The HVAC implication is that the gas turbine enclosure ventilation has to support both natural gas service (LEL 5 percent, autoignition 540 degrees C, IIA gas group) and hydrogen service (LEL 4 percent, autoignition 500 degrees C, IIC gas group) with the latter driving the more stringent ventilation rate and detection coverage. SBKJ duct on hydrogen-ready gas turbine enclosures uses 316L stainless throughout on the SBAL-V stainless configuration plus SBSF-1525 stitchwelder for continuous longitudinal seam.

Flue gas treatment — FGD, SCR, ACI and the 200-metre stack

The flue gas treatment train at a coal-fired power station removes regulated pollutants from the boiler exhaust before atmospheric discharge through the 80 to 200-metre stack. Modern Australian coal-fired stations include some combination of an electrostatic precipitator (ESP) or baghouse for particulate matter, a flue gas desulphurisation (FGD) unit for SO2, a selective catalytic reduction (SCR) unit for NOx, and an activated carbon injection (ACI) unit for vapour-phase mercury and dioxins. Each unit adds dedicated HVAC and ductwork to the station inventory.

ESP and baghouse particulate capture

Electrostatic precipitators capture fly ash from the flue gas using high-voltage corona discharge to charge the particles and collection plates to remove them; baghouses use fabric filter media in cylindrical cages with pulse-cleaning. Most Australian coal-fired stations were originally fitted with ESPs; many have been upgraded to a hybrid ESP-baghouse configuration to achieve the tighter modern emission limits. Captured fly ash is conveyed pneumatically to silos for beneficial reuse (cement, concrete and structural fill) or to ash dam disposal. Fly ash contains measurable Naturally Occurring Radioactive Material (NORM) — uranium, thorium and potassium-40 isotopes that concentrate during combustion — and is regulated under ARPANSA RPS 9. The pneumatic conveying ductwork uses heavy-gauge galvanised on the SBKJ SBTF-2020 at 1.5 to 2.0 mm wall thickness.

FGD wet limestone slurry scrubbing

Flue Gas Desulphurisation removes SO2 from coal-fired flue gas using either a wet limestone slurry scrubber (most common at modern stations targeting greater than 95 percent SO2 removal), a dry sorbent injection system (older retrofit, 60 to 80 percent removal) or a semi-dry spray dryer absorber (between the two). FGD inlet ductwork carries raw flue gas at 130 to 160 degrees C laden with SO2, SO3, HCl, HF, fly ash and trace heavy metals; outlet ductwork carries scrubbed flue gas at 50 to 65 degrees C saturated with water vapour plus residual acid gases. Inlet ductwork is typically corten steel or 316L stainless on the SBKJ SBTF-2020 spiral round at 1.5 to 2.0 mm wall; outlet ductwork is 316L throughout because the saturated wet acid environment attacks galvanised within months. The scrubber slurry handling adds gypsum byproduct (calcium sulphate dihydrate) which is sold as wallboard or cement additive feed or disposed in ash dam.

SCR ammonia injection and Class I Zone 2 IIA

Selective Catalytic Reduction injects ammonia (anhydrous NH3 or aqueous urea) into the flue gas upstream of a V2O5/WO3-TiO2 catalyst bed at 320 to 400 degrees C operating temperature, reducing NOx by 80 to 90 percent through the DENOX reaction. SCR ammonia storage and dosing is classified Class I Zone 2 IIA per AS/NZS 60079, with NH3 detection at floor level on 5 metre grid (ammonia relative density is 0.59 — it rises), first alarm 25 ppm STEL and second alarm 50 ppm triggering ammonia trip and grid notification. Catalyst is replaced on a 24,000 to 48,000 operating hour cycle as the surface becomes poisoned by chloride, sulphate, alkali metals and ash deposition. NH3 slip downstream of the catalyst is monitored at the stack continuous emission monitoring panel and must remain below 5 ppm under most state EPA licences.

ACI Activated Carbon Injection for mercury

Activated Carbon Injection adds powdered activated carbon to the flue gas upstream of the baghouse to capture vapour-phase mercury and dioxins, with the spent carbon collected in the baghouse and disposed as hazardous waste under each state EPA framework. Mercury emission is monitored continuously at the stack panel under POEO licence (NSW), EPA Victoria licence (VIC) and equivalent in other states, with the workplace exposure standard at 0.025 mg/m3 STEL for elemental mercury. Bromine-impregnated activated carbon products achieve substantially better mercury capture than untreated activated carbon and are the modern default at coal-fired stations targeting mercury control.

Stack continuous emission monitoring and CEM cabinet HVAC

The 80 to 200-metre stack at every coal-fired or gas-fired thermal power station houses the continuous emission monitoring (CEM) instrument panel near the stack base or at the sample probe elevation. The CEM measures mercury, SO2, NOx (NO plus NO2), CO, particulate matter, HCl, HF, NH3 slip and opacity on a continuous basis, reporting to the state EPA licence database. CEM cabinet HVAC runs ASHRAE Class A2 conditions (22 to 27 degrees C, 40 to 60 percent RH) on a dedicated split-system air conditioner to keep the analyser instruments within calibration tolerances. The CEM data feeds the National Greenhouse and Energy Reporting NGER scheme under the Clean Energy Regulator. The stack itself is built to AS 1318 (Industrial Chimneys) with AS/NZS 1170.2 wind loading and AS 1170.4 earthquake design, with continuous vibration and acoustic monitoring at the stack base.

Snowy 2.0 pumped hydro Salini Webuild FGJV — the largest single HVAC scope

Snowy 2.0 is the largest pumped hydro storage project in Australian history and the largest single HVAC duct scope in Australian power generation history. The project nameplate is 2 GW of generation capacity and 175 GWh of energy storage, being built by the Salini Impregilo Webuild Future Generation Joint Venture (FGJV) with Lendlease and Webuild as the EPC, with first generation expected in 2028. The Commonwealth Government is the underwriter through Snowy Hydro Limited.

Project geometry — Tantangara to Talbingo

The underground powerhouse cavern is approximately 800 metres below the surface in the Snowy Mountains region of NSW, connecting Tantangara Reservoir (upper) to Talbingo Reservoir (lower) through a 27-kilometre headrace tunnel driven by tunnel boring machines (TBM). Six 333 MW reversible Francis-type pump-turbines operate in either pump mode (consuming grid power to lift water from Talbingo to Tantangara, typically overnight or on excess renewable generation periods) or generate mode (discharging water back through the same machines to generate during peak demand). The cavern itself is approximately 250 metres long, 30 metres wide and 50 metres high, total internal volume 375,000 cubic metres. The access tunnel is approximately 2.7 kilometres long from the surface portal to the cavern entrance.

Access tunnel ventilation main on the SBTF-2020

The access tunnel main ventilation duct carries the bulk supply and return air between the surface fan houses at the Tantangara, Talbingo and main access tunnel portals and the powerhouse cavern. Duct diameter is 1,500 mm to 2,020 mm spiral round on the SBKJ SBTF-2020 large-diameter spiral tubeformer, with face velocity 8 to 12 m/s and pressure loss budget 200 to 400 Pa over the full tunnel run. The SBTF-2020 is the only Australian-supplied machine that produces 2,020 mm diameter spiral round duct in a single pass, which makes it the machine of choice for the access-tunnel scope on every Australian underground hydroelectric and pumped hydro project. Joint construction is bolted slip-fit with EPDM gasket; the longitudinal spiral seam is helical lock-form for galvanised or continuously welded on the SBSF-1525 stitchwelder for stainless. Snowy 2.0 supplies a parallel of 2 by 2,020 mm diameter galvanised spiral main supplies and 2 by 2,020 mm diameter return through the main access tunnel.

Cavern internal supply and exhaust distribution

Inside the powerhouse cavern, supply and exhaust trunks distribute air across the six generator bays. Cavern ventilation rate is 6 to 10 ACH of the 375,000 m3 internal volume — total ventilation rate 2.2 million to 3.7 million cubic metres per hour — to handle heat removal of 30 to 50 MW continuous from the six 333 MW pump-turbines (each rejecting 5 to 8 MW into the cavern in turbine mode and 6.6 to 10 MW in pump mode). Trunk velocities are 8 to 10 m/s on supply collection and 12 to 15 m/s on exhaust trunk. SBKJ rectangular duct on the SBAL-V at 1,500 mm wide by 600 to 1,000 mm deep handles the supply trunk runs along the upper machine hall wall, with branch take-offs dropping down to floor-level supply grilles at each generator bay. Spiral round at 800 mm to 1,500 mm on the SBTF-1500 handles the auxiliary plant and corridor runs.

Pressure cascade and smoke spill

The cavern is maintained at slight positive pressure (10 to 30 Pa) relative to the access tunnel system to prevent ingress of diesel exhaust from access tunnel vehicle movements during plant operation. On AS 1668.1 fire alarm trip the cavern HVAC switches to smoke spill mode — supply dampers close, exhaust ramps to 250 degrees C-rated smoke fan capacity, smoke is dumped through dedicated smoke spill shafts to the surface per NFPA 850 EGP equivalent. Smoke control zoning splits the cavern into the machine hall zone, the transformer hall zone, the auxiliary plant zone and the control room zone, with fire dampers on every wall crossing rated to AS 1530.4 -/120/120 minimum.

Transformer hall, GIS switchroom and battery room HVAC

Each main generating unit at Snowy 2.0 has at least one large step-up transformer (400 to 600 MVA at 500 kV) plus auxiliary transformers for station service and excitation. The transformer hall is a separate fire-rated cavern bay from the machine hall with transformers in bunded oil-containment pits per AS 1940 and IEC 61936. Hall ventilation is 8 to 15 ACH continuous on 316L stainless duct downstream of an oil-mist eliminator. The GIS switchroom uses 500 kV SF6 GIS with floor-level NDIR SF6 detection on 5 metre grid, first alarm 1,000 ppm and second alarm 10,000 ppm, 4 to 6 ACH baseline rising to 20 to 30 ACH on detection trip. The lead-acid station battery room is Zone 2 IIB+H2 with ceiling-level catalytic-bead H2 detection, 4 to 8 ACH baseline, 316L stainless because sulphuric acid mist attacks galvanised within months.

Kidston Pumped Hydro Genex on an abandoned gold mine

Kidston Pumped Hydro Genex is the first new Australian pumped hydro project to reach construction phase and is being built using two existing open-cut mine voids at the former Kidston gold mine in North Queensland as the upper and lower reservoirs. The 250 MW two-unit station with 8 hours of storage capacity is the flagship project for the Northern Queensland Renewable Energy Zone. The surface powerhouse configuration simplifies the HVAC ductwork compared to Snowy 2.0 underground cavern — conventional industrial HVAC on the SBKJ SBAL-V galvanised for the bulk of the scope plus 316L stainless on the SBSF-1525 stitchwelder for the transformer hall, switchroom and the integrated 50 MW solar BESS bay.

Gas-fired CCGT and OCGT — Mortlake, Tallawarra B, Torrens, Kurri Kurri

Gas-fired generation provides the flexible mid-merit and peaking capacity that balances the increasingly variable renewable generation mix on the National Electricity Market. Australian gas-fired generation comprises Combined Cycle Gas Turbine (CCGT) plants providing mid-merit and Open Cycle Gas Turbine (OCGT) plants providing fast-start peaking capacity. Each technology has distinct HVAC scope and standards.

CCGT efficiency and HRSG scope

Combined Cycle Gas Turbine plants use a gas turbine to drive a generator and recover waste heat from the gas turbine exhaust (typically 600 degrees C) in a Heat Recovery Steam Generator (HRSG) to drive a downstream steam turbine for a second cycle of generation. Total CCGT efficiency reaches 55 to 62 percent on modern GE Vernova 7HA, 9HA, Mitsubishi M501J and M701F or Siemens SGT-A65 frames. Australian CCGT operators include Origin Mortlake VIC (566 MW), EnergyAustralia Tallawarra B NSW (320 MW, commissioned 2023 as the first new gas peaking station for a decade), AGL Torrens Island SA, and Pacific Hydro Mortlake VIC. CCGT HVAC scope includes the HRSG bundle (subcritical 540 to 600 degrees C steam, AS 4036 pressure vessel, 309S or Inconel material for the highest-temperature bundles), the steam turbine hall (similar HVAC to a conventional coal-fired turbine hall), the condenser and cooling tower (similar to coal-fired), and full SCR ammonia injection scope (Class I Zone 2 at the urea or anhydrous ammonia storage, NH3 25 ppm STEL slip monitoring at stack).

OCGT fast-start peaking — Kurri Kurri, Reeves Plains, Quarantine

Open Cycle Gas Turbine plants use the gas turbine to drive the generator and exhaust the 600 degrees C hot gas directly to a stack, achieving only 35 to 42 percent efficiency but with much faster start-up — typical OCGT cold start to full output is 10 to 15 minutes versus 60 to 180 minutes for CCGT cold start including HRSG warm-up. OCGT is therefore the peaking plant providing fast-start dispatch during grid demand peaks. Snowy Hydro Kurri Kurri NSW (660 MW OCGT, hydrogen-ready, planned commissioning 2026) is the largest new Australian OCGT under construction. Snowy Hydro Reeves Plains SA (feasibility), Origin Quarantine SA, Pacific Hydro Mortlake OCGT and several Stanwell and CS Energy QLD peaking units complete the OCGT fleet. OCGT HVAC scope omits the HRSG, steam turbine, condenser and cooling tower entirely — the HVAC scope is dominated by the gas turbine enclosure (Class I Zone 1 IIA natural gas, gas leak detection, NFPA 70 NEC and AS/NZS 60079), the generator (typically air-cooled at OCGT size rather than hydrogen-cooled because most OCGT units are below 350 MW), and the fast-start auxiliary diesel for grid synchronisation.

Natural gas HVAC under Class I Zone 1 IIA

The natural gas fuel side of the gas turbine enclosure is classified Class I Zone 1 IIA per AS/NZS 60079. Natural gas LEL is 5 percent volume in air; autoignition temperature is 540 degrees C; minimum ignition energy is 0.29 mJ. Natural gas relative density is 0.55 (mostly methane) — it rises. Detection uses catalytic-bead or NDIR gas sensors at ceiling level on 5 metre grid, first alarm at 1 percent volume (20 percent LEL) triggering ventilation boost and second alarm at 2 percent volume (40 percent LEL) triggering gas trip, fire alarm and grid-side isolation. NFPA 70 NEC and the Australian Wiring Rules AS 3000 plus AS/NZS 60079.14 cover electrical installation. NFPA 86 (Standard for Ovens and Furnaces) covers the combustor design.

HFO, LFO, diesel, kerosene and LPG backup fuels

Most Australian OCGT and CCGT plants are dual-fuel capable — natural gas as primary fuel plus a liquid backup (typically distillate fuel oil DFO, kerosene, light fuel oil LFO or heavy fuel oil HFO depending on the OEM frame and the operator preference). The liquid fuel storage area is classified Class I Zone 2 IIA per AS/NZS 60079 with AS 1940 (Storage and Handling of Flammable and Combustible Liquids) requirements for tank bunding, fire suppression and ventilation. Diesel backup for emergency black-start is mandatory at every gas-fired station per AEMO Grid Code requirements. SBKJ duct at the liquid fuel storage and pump room uses 316L stainless on the SBAL-V stainless configuration plus AS/NZS 60079 spark-resistant fan housings.

Cooling tower, condenser and AS/NZS 3666 Legionella program

The steam condenser at a thermal power station condenses the LP exhaust steam from the steam turbine back to liquid for return to the boiler feedwater system. The condenser uses cooling water on the tube side to absorb the heat of condensation, with the cooling water then rejected to a cooling tower or directly to a water body (lake, ocean or river). Cooling tower configurations include natural-draft wet (the iconic hyperbolic concrete tower at Liddell, Bayswater, Eraring, Vales Point, Mt Piper, Yallourn, Loy Yang A, Stanwell, Tarong, Callide, Muja and Kogan Creek), mechanical-draft wet (smaller plant footprint, used at most CCGT plants including Mortlake and Tallawarra B), dry (air-cooled, used at the Kogan Creek supercritical unit because of the inland location and limited water availability), or hybrid wet-dry (Vales Point retrofit).

AS/NZS 3666 Legionella program

Every wet cooling tower in Australia is regulated under AS/NZS 3666 (Air-handling and water systems of buildings — Microbial control) administered by the relevant state Department of Health. The cooling tower must be registered, with monthly inspection, quarterly water sampling for Legionella spp. and weekly bacterial counts. The cooling water treatment program includes chlorination (Cl2 dosing maintaining 0.5 to 2 mg/L free chlorine), pH control (typically 7.5 to 8.5), biocide alternation between oxidising and non-oxidising products to prevent biofilm resistance, and blowdown to control cycles of concentration. The HVAC engineer's interaction with the cooling tower is at the drift eliminator inspection access (AS 2865 confined space), the louvre supply housing, the basin maintenance hatch and the cooling water make-up and blowdown pump room (typically conventional industrial HVAC).

Heavy metal trace contamination

Cooling water blowdown at coal-fired stations contains trace heavy metals scrubbed from the flue gas — mercury, arsenic, selenium, chromium, cadmium, lead, vanadium, nickel, zinc, manganese and cobalt — plus the regulated discharge concentrations of each under the state EPA licence. Blowdown treatment includes precipitation, settling, filtration and final discharge monitoring. The Safe Work Australia workplace exposure standards for the affected heavy metals — mercury 0.025 mg/m3 STEL, arsenic 0.05 mg/m3, cadmium 0.01 mg/m3, lead 0.05 mg/m3, chromium VI 0.05 mg/m3, beryllium 0.001 mg/m3 STEL — drive the personnel monitoring envelope at the blowdown treatment plant.

Control building, DCS and AEMO Grid Code redundancy

The plant control room is the operational heart of every thermal power station and houses the Distributed Control System (DCS) workstations, the SCADA gateway, the protection relay panels, the communication equipment and the operator amenity. Australian thermal power plants typically use one of Honeywell Experion, Yokogawa CENTUM, ABB 800xA, Emerson DeltaV or Schneider Modicon DCS platforms.

ASHRAE TC 9.9 Class A1 conditions

The control room and the adjacent DCS cabinet hall run ASHRAE TC 9.9 Class A1 mission-critical conditions — 22 to 27 degrees C dry bulb, 20 to 80 percent RH, with the dew point controlled between -9 and 15 degrees C. Cooling load is dominated by the DCS cabinet thermal load (typically 100 to 300 kW for a large coal-fired station) plus occupant amenity load. Ventilation is dual-redundant N+1 AHU plant with automatic changeover, dual chilled water plants with independent power supply, and UPS-backed control panel allowing continued HVAC operation through a station blackout. Material specification on the control room ductwork is galvanised on the SBKJ SBAL-V at 1.0 mm thickness for the main runs with the control room enclosure held at slight positive pressure (50 to 100 Pa above ambient).

AEMO Grid Code reliability

The AEMO Grid Code defines the Network Operating Plan obligations including the requirement for dispatchability availability above 90 percent at all times, the requirement for fast-frequency response within seconds, and the requirement for emergency response within minutes. The control room HVAC supports these obligations by maintaining the DCS, SCADA and protection relay equipment within manufacturer specification at all times. Black-start capability is mandatory — the plant must be able to self-start without grid supply to support grid restoration after a system black event. Black-start diesel generators are sized for the plant auxiliary load and HVAC critical load combined.

Co-located grid-scale BESS — Eraring, Hornsdale, Waratah Super Battery

Co-located grid-scale Battery Energy Storage Systems (BESS) at coal-fired and gas-fired sites are the dominant transition pathway from fossil-fuel generation to renewable replacement. Australian operating examples include:

• AGL Liddell BESS — commissioned 2024 on the closed Liddell coal site, NSW.
• AGL Loy Yang battery — planned at Loy Yang A VIC.
• Origin Eraring battery — 460 MW first phase 2024, planned 700 MW and 2,800 MWh which will be Australia's largest single battery installation.
• Neoen Hornsdale Power Reserve — 150 MW Tesla Megapack in SA, originally commissioned 2017 as the world's first large-scale Tesla installation.
• EnergyAustralia Wallerawang battery — on the closed Wallerawang coal site NSW.
• EnergyAustralia Yallourn battery — planned 350 MW on the Yallourn site VIC.
• Akaysha Waratah Super Battery — 850 MW on the Munmorah coal site NSW, one of the largest grid-scale BESS in the world.

NFPA 855 and AS/NZS 5139

NFPA 855 (Standard for the Installation of Stationary Energy Storage Systems) and AS/NZS 5139 (Electrical installations — Safety of battery systems) are the primary references. NFPA 855 sets the spacing, fire suppression, ventilation and detection requirements for stationary Li-ion BESS installations. The dominant hazard is thermal runaway of an individual cell propagating to an entire module or rack, releasing electrolyte vapour (DMC, EMC, EC, organic carbonate solvents) and gases (CO, H2, methane, ethane, ethylene, HF from PF6 electrolyte salt decomposition). Vapour density is mixed — HF is denser than air, hydrogen lighter — so detection grids run at both ceiling and floor levels with combined heat, smoke and combustible gas detection.

BESS HVAC scope and duct material

Co-located BESS HVAC scope includes the building shell ventilation around containerised Tesla Megapack or equivalent products (4 to 8 ACH baseline rising to 20 to 30 ACH on detection trip), the thermal-runaway extract route from the Megapack containers to atmosphere (316L stainless on the SBKJ SBAL-V stainless configuration plus spark-resistant fan housing per AS/NZS 60079 Zone 2 IIB+H2 thermal event classification), the inverter station HVAC (typically modular skid-mounted with integral split-system), and the substation control building (positive-pressure refuge at 50 to 100 Pa above ambient, SCADA thermal load, AEMO Grid Code redundancy). Ductwork is 316L stainless because HF and organic carbonate vapour attack galvanised within hours. Spark-resistant aluminium or non-sparking stainless fan impellers are mandatory because the off-gas mixture includes hydrogen and the room is classified Zone 2 IIB+H2 during a thermal event.

Asbestos legacy lagging — Liddell, Yallourn demolition and abatement

Coal-fired power stations commissioned before approximately 1990 used substantial asbestos-containing thermal insulation lagging on the boiler external surfaces, the steam pipe runs from boiler to turbine, the condenser shell, the feedwater heater shells and the auxiliary pump bodies. Asbestos is regulated under the WHS (Asbestos) Regulations 2011 administered by Safe Work Australia and the state work health and safety regulators, with the workplace exposure standard at 0.1 fibres/mL 8-hour TWA for any asbestos fibre type.

Decommissioning HVAC scope at Liddell and Wallerawang

The decommissioning of AGL Liddell (closed 2023, demolition 2023 to 2026) and EnergyAustralia Wallerawang (closed 2014, demolished 2018) required substantial asbestos abatement under AS 2601 (Demolition of Structures) and the WHS Asbestos Regulations. Decommissioning HVAC scope includes temporary negative-pressure enclosure ventilation around active asbestos removal areas (typically 4 to 8 ACH with HEPA-filtered exhaust), the personnel decontamination unit HVAC (separate shower and changing rooms held at progressively higher containment levels), the waste consolidation area HVAC (rigid double-bagged asbestos waste under continuous monitoring), and the post-abatement air clearance monitoring program (TEM transmission electron microscopy on settled dust samples) before any non-asbestos demolition work can proceed.

Yallourn 2028 closure planning

EnergyAustralia Yallourn (1,480 MW brown coal, scheduled closure 2028) will face similar asbestos abatement requirements at decommissioning. Planning is underway in 2026 for the staged shutdown and the subsequent demolition and site rehabilitation works. The Yallourn battery (350 MW planned) on the same site will use the cleared decommissioned area for the new BESS infrastructure, similar to the AGL Liddell BESS approach.

NORM Naturally Occurring Radioactive Material under ARPANSA RPS 9

Fly ash and bottom ash from coal-fired power station combustion contain Naturally Occurring Radioactive Material (NORM) — uranium, thorium and potassium-40 isotopes that exist in the raw coal at trace levels and concentrate by approximately tenfold during combustion as the volatile carbon, hydrogen and oxygen leave but the metal isotopes remain in the ash. ARPANSA RPS 9 (Code for Radiation Protection in Planned Exposure Situations) is the regulatory framework, with the Annual Limit on Intake and the workplace exposure limit set on a fibre-and-concentration basis.

Fly ash beneficial reuse

Fly ash is predominantly beneficially reused in Australia as cement and concrete additive (Class F fly ash with low calcium content from black coal stations is preferred for high-performance concrete), as structural fill in road and infrastructure construction, and as feedstock for lightweight aggregate manufacture. Beneficial reuse rates at modern Australian coal stations approach 50 to 70 percent of generated fly ash by mass; the balance is disposed in ash dam. The cement, concrete and structural fill applications are subject to ARPANSA NORM assessment to confirm that the cumulative dose to any user of the product remains below the public exposure limit.

HVAC implications at ash silo and conveying

Fly ash silos and pneumatic conveying ductwork have the inhalable WES at 10 mg/m3 8-hour TWA plus the NORM exposure overlay. LEV at every transfer point uses 1 to 2 m/s capture velocity to maintain breathing-zone fly ash below 3 mg/m3 (one-third of the WES for safety margin). Ductwork is galvanised on the SBKJ SBTF-2020 at 1.5 to 2.0 mm wall thickness with grounding and bonding per AS 1020 and AS/NZS 60079.14. The collected dust returns to the ash silo or directly to the cement product loading area.

Transmission interconnect and the National Electricity Market

Thermal power stations connect to the National Electricity Market (NEM) through transmission lines operated by the state transmission network service providers — TransGrid (NSW), AusNet Services (ASX:AST) (VIC), Powerlink (QLD), ElectraNet (SA), Western Power (WA outside NEM, in SWIS) and TasNetworks (TAS). AEMO operates the NEM dispatch and the Frequency Control Ancillary Services (FCAS) market; AEMC sets the National Electricity Rules; AER administers the cost-recovery framework; CER administers the National Greenhouse and Energy Reporting (NGER) scheme; ESB Energy Security Board coordinates the integrated system plan.

Industry peak bodies

The Australian Energy Council (AEC) is the peak industry body for major electricity and gas businesses. The Australian Petroleum Production and Exploration Association (APPEA) represents the upstream gas industry. The Australian Coal Association (ACA, now combined with the Minerals Council of Australia in its coal division) represents the coal industry. The Climate Change and Energy Committee (CCEC) and the Energy Networks Australia (ENA) round out the industry-body framework. The HVAC engineer engages with these bodies at industry-standards-development level and at training and accreditation level.

Commercial cost envelope and SBKJ delivery

A typical Australian small to medium thermal power station HVAC duct package (say 200 to 500 MW peaking OCGT, single building, conventional galvanised) runs AUD 1.5 to 4 million. A medium to large coal-fired or CCGT station (700 to 1,500 MW, multi-building, mixed galvanised and stainless including FGD and SCR) runs AUD 8 to 25 million. A Snowy 2.0-scale fully underground 2 GW pumped hydro powerhouse with all ancillary scope runs AUD 50 to 100 million depending on the stainless content fraction and the access tunnel ducting scope. A co-located grid-scale BESS of 100 to 500 MW with surrounding building shell HVAC runs AUD 2 to 8 million.

SBKJ machine delivery lead time

The SBAL-V, SBAL-III, SBSF-1525, SB-ZF1500, SBFB-1500, SBPC1500, SBLR-600 and SBTF-1500/1602/2020 are typically delivered within 16 to 22 weeks of order from the SBKJ Box Hill North VIC project office, including configuration for stainless or galvanised service and Factory Acceptance Test. See the HVAC duct machine buyer's checklist for full procurement guidance and the duct production line total cost of ownership analysis for life-cycle commercial assessment.

How SBKJ specifies HVAC ductwork on an Australian thermal power generation project

The procedure SBKJ engineers walk through with Australian thermal power, pumped hydro and BESS project fabricators looks like the following sequence, which has evolved from supplying machinery to power-generation projects over the last decade.

1. Confirm the generating technology and operator. Subcritical, supercritical, brown coal, CCGT, OCGT, pumped hydro, conventional or pump-turbine reversible. AGL, Origin, EnergyAustralia, Stanwell, CS Energy, Snowy Hydro, Hydro Tasmania, Synergy, Genex. Each combination drives a distinct HVAC ductwork inventory and material specification.
2. Read the hazardous area classification drawing. The HAC drawing is the master document signed off by a Certified Hazardous Area Auditor under the IECEx CoPC scheme. Zone 21/22 coal dust at PF, Class I Zone 1 IIA natural gas at gas turbine enclosure, Class I Zone 1 IIC at hydrogen generator vent, Class I Zone 2 IIA at SCR ammonia and HFO/LFO storage.
3. Read the NER, AEMO Grid Code and state environmental licence. NER drives dispatchability; AEMO Grid Code drives Network Operating Plan redundancy; NSW EPA POEO, VIC EPA, QLD DES, SA EPA, WA DWER drive stack emission monitoring and CEM cabinet HVAC.
4. Confirm the BESS scope. Co-located grid-scale BESS for FCAS or capacity firming drives a separate Li-ion thermal-runaway extract scope to NFPA 855 and AS/NZS 5139.
5. Confirm the asbestos legacy scope. Pre-1990 stations require AS 2601 demolition and asbestos abatement HVAC during decommissioning.
6. Size the duct cross-section to face velocity and pressure loss. 8 to 10 m/s on supply collection, 12 to 15 m/s on exhaust trunk, 200 to 400 Pa pressure loss budget on access tunnel main runs. Duct sized to standard SBAL-V, SBFB-1500 and SBTF-1500/1602/2020 outputs.
7. Specify the connection method. TDF flange for rectangular duct on the SBAL-V; SB-ZF1500 flange for high-pressure refuge ducts; bolted slip-fit for round duct on the SBTF and SBFB. Continuous longitudinal seam welding on the SBSF-1525 stitchwelder for any Zone 1 or Zone 2 duct; standard Pittsburgh seam acceptable for unclassified duct.
8. Confirm coil source. 1.5 mm galvanised G275 from BlueScope on standard projects; 316L UNS S31603 stainless on hazardous-area and corrosive scope; 309S, 310S or Inconel on high-temperature boiler and HRSG service. Mill certificates required for every coil traceable to every piece of finished duct.
9. Schedule fabrication. Galvanised duct at 25 m/min on the SBAL-V translates to 150 to 200 metres per shift. Stainless at 8 to 12 m/min translates to 50 to 70 metres per shift. A typical coal-fired station with full FGD and SCR retrofit requires 8,000 to 15,000 linear metres of duct fabricated in 50 to 100 shifts depending on stainless fraction.
10. Test and commission under NER, AEMO and state EPA. Pressure-test installed ductwork to 1.5 times design operating pressure. AS 4254 Class A on stainless, Class B on galvanised. Inject calibration gas at each detection point (SF6 at GIS, H2 at hydrogen generator, NH3 at SCR, CO at gas turbine, SO2 at FGD) and verify each detector response and HVAC interlock. Witness test by buyer QA or NATA-certified independent inspector. Document on commissioning report tied to NER, AEMO Grid Code, AS 1851 fire damper register, AS/NZS 60079.17 hazardous area register, state EPA POEO licence, ARPANSA RPS 9 NORM record and ISO 14001.

This procedure runs parallel to the turbine-generator commissioning and is normally on the project critical path during the final 6 to 12 months before first synchronisation to the National Electricity Market.

Construction-phase HVAC challenges

Thermal power generation construction generates substantial hot-work activity — boiler tube welding, structural steel welding, mechanical fitting and instrument calibration — with significant fume and welding spatter generation. Permanent HVAC ductwork is typically installed in the latter phases of construction, meaning the building services during the bulk of welding work are temporary ventilation systems on portable diesel-fired air movers and flexible polyethylene duct. Air change rates are 4 to 8 per hour during welding activity, dropping to 2 per hour during non-active periods. Confined-space welding inside the boiler drum, the HRSG header or the cooling tower basin requires oxygen-deficiency monitoring per AS 2865.

On Snowy 2.0 specifically, the temporary tunnel ventilation system during the 2020 to 2026 construction phase has been one of the largest in Australian civil engineering history — multiple parallel 2,020 mm diameter galvanised supply and exhaust ducts running the full 2.7 kilometre access tunnel length, with surface fan houses at Tantangara, Talbingo and the main access tunnel portal. The TBM (Tunnel Boring Machine) operating in the headrace tunnel during the 2024 to 2026 phase required dedicated TBM ventilation systems sized for the 100-plus personnel on board at any time plus the diesel exhaust from the cutterhead drive and the muck handling system.

Permanent HVAC commissioning typically runs in parallel with mechanical completion of the turbine-generator units. The HVAC system is hot-commissioned (run for 30 to 60 days at design operating conditions) before first synchronisation to confirm steady-state heat removal capacity and to baseline the AS 1851 fire damper register and the AS/NZS 60079.17 hazardous area register.

Inspection, maintenance and operational compliance

Once commissioned, a thermal power generation HVAC system enters a structured inspection and maintenance regime under AS 1851 (fire and smoke damper maintenance), AS/NZS 60079.17 (hazardous area inspection and maintenance, adopting IEC 60079-17 verbatim), AS 4037 (in-service pressure vessel inspection), AS/NZS 3666 (cooling tower microbial control), the Coal Mine Workers' Health Scheme (administered by Resources Safety and Health Queensland and the NSW Resources Regulator), the ARPANSA RPS 9 NORM register, the state EPA stack emission licence with CEM verification, the NGER scheme submission to CER, and ISO 14001 internal audit annually.

The integrated inspection pack covers the AS 1851 fire damper drop test annually, the AS/NZS 60079.17 visual inspection 12-monthly and close inspection 24-monthly, the SF6 leakage measurement quarterly under NGER, the lead-acid battery hydrogen detection calibration 6-monthly, the Li-ion BESS detection calibration 12-monthly, the SCR ammonia detection calibration 6-monthly, the cooling tower Legionella sampling quarterly, the CEM stack monitor calibration daily auto-zero plus monthly span-check, and the coal worker respirable dust monitoring on a continuous statistical basis per the post-2018 CWP Royal Commission recommendations.

Operations staff are trained on alarm response, manual ventilation override, AEMO grid code outage notification procedures, AS 2865 confined space entry permit issue, NFPA 850 EGP emergency response, RSHQ and NSW Resources Regulator coal worker health screening procedures, and the state-specific environmental licence reporting requirements. Competency records are filed in the operator's human resources management system and refreshed on a 2-yearly cycle.

Frequently Asked Questions

What Australian standards govern HVAC ductwork in a coal-fired or gas-fired power station?

AS 1668.2 mechanical ventilation, AS 4254 ductwork construction, AS 1530.4 fire-rated penetrations, AS/NZS 60079 hazardous area (Zone 21/22 coal dust, Zone 1 natural gas and hydrogen, Class I Zone 2 SCR ammonia), AS 1940 flammable liquid storage, AS 3957 dust hazard, NFPA 850 Electric Generating Plants, NFPA 60 pulverised fuel, NFPA 654 combustible dust, NFPA 86 industrial furnace, NFPA 68/69 deflagration vent and inerting, NFPA 70 NEC, AS 4036/4037 pressure vessel, AS 1318 industrial chimney, AS/NZS 1170.2 wind, AS 1170.4 earthquake, AS/NZS 1554 weld, NER, AEMO Grid Code, NSW EPA POEO, VIC EPA, QLD DES, SA EPA, WA DWER, AS 4214 gaseous suppression, AS 2118, AS 1670, ARPANSA RPS 9 NORM. Safe Work Australia WES for respirable coal dust 1.5 mg/m3 (CWP Black Lung Royal Commission 2018), RCS 0.05 mg/m3, fly ash inhalable 10 mg/m3, CO 30 ppm, SO2 2 ppm STEL, NO2 5 ppm, NOx 5 ppm STEL, Hg 0.025 mg/m3 STEL, NH3 25 ppm STEL, CH4 1.25% LEL, H2 4% LEL, benzene 1 ppm STEL, asbestos 0.1 fibres/mL.

What is the largest coal-fired power station in Australia and what HVAC scope does it run?

Eraring Power Station NSW (Origin Energy) at 2,880 MW (four 720 MW black coal units) is Australia's largest single power station. HVAC inventory spans coal handling Zone 21/22, four vertical roller mills per unit at NFPA 60 PF, subcritical boiler at 540 degrees C 200 bar, turbine hall with hydrogen-cooled generator at Class I Zone 1 IIC, natural-draft cooling towers under AS/NZS 3666 Legionella, ESP and ash handling under ARPANSA RPS 9 NORM, 200-metre stack with CEM reporting to NSW EPA POEO, and the new co-located 460 MW BESS (commissioned 2024, expanding to 700 MW and 2,800 MWh — Australia's largest single battery). Total duct inventory is tens of kilometres across the envelope.

What HVAC scope applies specifically to Snowy 2.0 pumped hydro?

Snowy 2.0 is 2 GW and 175 GWh of pumped hydro storage — six 333 MW reversible Francis pump-turbines in an 800-metre-deep underground cavern, built by Salini Impregilo Webuild FGJV with Lendlease and Webuild EPC, opening 2028. HVAC includes access tunnel main on 2 by 2,020 mm SBKJ SBTF-2020 spiral round across 2.7 km, machine hall ventilation 6 to 10 ACH of 375,000 m3 (2.2 to 3.7 million m3/hour for 30 to 50 MW heat removal), transformer hall 316L at 8 to 15 ACH, GIS switchroom 4 to 6 ACH baseline rising to 20 to 30 ACH on SF6 detection, lead-acid battery Zone 2 IIB+H2, AS 2865 confined-space penstock and tailrace ventilation, smoke spill per AS 1668.1 and NFPA 850 EGP. Tantangara to Talbingo Reservoir headrace tunnel is 27 km driven by TBM.

What is the difference between CCGT and OCGT in HVAC terms?

CCGT combines gas turbine plus HRSG plus steam turbine at 55 to 62 percent efficiency (Mortlake VIC, Tallawarra B NSW, Torrens Island SA). OCGT runs gas turbine only at 35 to 42 percent efficiency but 10 to 15 minute start-up versus 60 to 180 minutes for CCGT (Kurri Kurri NSW 660 MW under construction, Reeves Plains SA, Quarantine SA). CCGT HVAC adds HRSG bundle (540 to 600 degrees C, 309S or Inconel), steam turbine hall, condenser, cooling tower and full SCR. OCGT omits all of these — HVAC is dominated by gas turbine enclosure (Class I Zone 1 IIA natural gas, NFPA 70 NEC), air-cooled generator and fast-start diesel.

How is pulverised fuel coal mill HVAC and dust extraction specified?

Coal mills grind raw coal to 70 percent finer than 75 micrometre. Mill enclosure is Zone 21, surrounding house is Zone 22. Coal dust Kst 100 to 250 (St2) per AS 3957. NFPA 60 sets PF design; NFPA 654 combustible dust; NFPA 68 deflagration vent (1 to 2 m2 per 10 m3); NFPA 69 inerting (N2 blanket, O2 below 8 percent). LEV at 1 to 2 m/s capture velocity maintains respirable coal dust below 0.5 mg/m3 (one-third of CWP-tightened WES). Ductwork is heavy-gauge galvanised on SBKJ SBFB-1500 or SBTF-2020 at 1.5 to 2.0 mm with grounding/bonding per AS 1020 and AS/NZS 60079.14. Dedicated baghouse or ESP collection.

What HVAC ductwork applies to a hydrogen-cooled generator?

Generators above 700 MW use hydrogen cooling because H2 has 7 times the heat capacity of air. Inventory 50 to 200 kg at 3 to 5 bar. Generator enclosure interior and purge gas vent paths are AS/NZS 60079 Class I Zone 1 IIC (LEL 4 percent, autoignition 500 degrees C, MIE 0.017 mJ). Photoacoustic or catalytic-bead H2 sensors at ceiling level, first alarm 1 percent volume, second alarm 2 percent triggering grid trip and N2 purge. Purge vents through 316L stainless on SBKJ SBSF-1525 with continuous longitudinal seam to tall stack. NFPA 2 Hydrogen Technologies Code. AS/NZS 60079 Zone 1 spark-resistant fan housings mandatory.

How is FGD, SCR and ACI flue gas treatment HVAC ductwork specified?

FGD wet limestone slurry inlet at 130 to 160 degrees C is corten or 316L on SBKJ SBTF-2020 at 1.5 to 2.0 mm; outlet at 50 to 65 degrees C saturated wet acid is 316L throughout on SBSF-1525. SCR catalyst at 320 to 400 degrees C in 316L or 304H. SCR ammonia is Class I Zone 2 IIA with floor-level NH3 detection on 5 metre grid, first alarm 25 ppm STEL, second alarm 50 ppm. ACI carbon injection extract is 316L on SBAL-V stainless. CEM cabinet at stack base runs ASHRAE Class A2 on dedicated split-system to keep analysers in calibration. Stack to AS 1318 with AS/NZS 1170.2 wind and AS 1170.4 earthquake.

What is the Black Lung CWP Royal Commission 2018 and how does it affect HVAC duct specification?

The Queensland Coal Workers Pneumoconiosis Royal Commission of 2018 found Black Lung disease (CWP and progressive massive fibrosis PMF) had re-emerged among QLD and NSW coal mine workers. Recommendations tightened the respirable coal dust WES to 1.5 mg/m3, introduced mandatory 6-monthly respiratory medical examinations through the Coal Mine Workers' Health Scheme administered by Resources Safety and Health Queensland (RSHQ) and the NSW Resources Regulator scheme, required continuous statistical occupational hygiene measurement, and required mandatory RCS monitoring at 0.05 mg/m3. For HVAC at coal handling areas, LEV at every transfer point is sized to maintain breathing-zone respirable coal dust below 0.5 mg/m3 (one-third of WES safety margin) at 1 to 2 m/s capture velocity on heavy-gauge galvanised SBFB-1500 or SBTF-2020 at 1.5 to 2.0 mm.

What is the HVAC scope for a co-located grid-scale BESS at a coal or gas station?

Co-located BESS examples: AGL Liddell BESS, AGL Loy Yang battery, Origin Eraring battery 700 MW 2,800 MWh (Australia's largest), Neoen Hornsdale Power Reserve 150 MW Tesla Megapack, EnergyAustralia Wallerawang and Yallourn 350 MW battery, Akaysha Waratah Super Battery 850 MW. NFPA 855 and AS/NZS 5139. Building shell ventilation 4 to 8 ACH baseline, 20 to 30 ACH on thermal-runaway detection. Thermal-runaway extract is 316L stainless on SBKJ SBAL-V plus spark-resistant fan housing per AS/NZS 60079 Zone 2 IIB+H2. Off-gas includes CO, H2, methane, ethane, ethylene, HF — mixed vapour density with detection at both ceiling and floor.

Are SBKJ machines suitable for Australian thermal power generation projects?

Yes. SBAL-V galvanised handles control room, office, amenity, workshop and unclassified scope at 200 to 1,500 mm wide and 25 m/min on 1 mm. SBAL-V stainless handles FGD, SCR, ACI, hydrogen generator purge, BESS thermal-runaway and coastal corrosion at 8 to 12 m/min on 1 mm 316L. SBAL-III handles heavy-gauge above 2,500 Pa or where structural reinforcement exceeds SBAL-V envelope. SB-ZF1500 produces flange duct for high-pressure positive-pressure refuge. SBSF-1525 handles continuously welded longitudinal seam for stainless under AS/NZS 60079.14. SBFB-1500 produces spiral round to 1,500 mm for coal mill and PF extract. SBTF-1500, SBTF-1602 and SBTF-2020 produce spiral round to 1,500, 1,602 and 2,020 mm for access tunnel, fan house, FGD inlet and cooling tower precinct. SBPC1500 plasma cuts 316L sheet penetrations. SBLR-600 laser bevels weld-prep edges. Box Hill North VIC office supports specification, FAT and commissioning.

Related guides

For adjacent power-generation and renewable-energy references, see the following SBKJ insights:

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