Dairy Processing HVAC Duct Guide — Milk Powder, UHT, Cheese, Butter, Yogurt, Ice Cream and Infant Formula Manufacturing in Australia

Why dairy is one of the hardest food HVAC specifications in Australia

At first glance a dairy plant looks like a long chain of stainless steel tanks, pipes and process equipment. Walk it from end to end and the engineering complexity unfolds. A single integrated dairy site in Allansford, Tatura, Stanhope, Burnie, Cobden, Crestmead or Lismore can run more than a dozen distinct HVAC zones in the same building footprint: raw milk receival at the truck dock running wet floors and lactic odour, pasteurisation at 75 to 85 degrees Celsius shedding latent steam, UHT at 140 to 150 degrees Celsius with hydrogen peroxide sterilant carryover from aseptic filling, cream separation at 12 to 16 degrees Celsius, butter at 8 to 10 degrees Celsius chilled, yogurt fermentation at 40 to 45 degrees Celsius with lactic acid odour, cheese maturation at 10 to 15 degrees Celsius and 80 to 90 percent relative humidity holding millions of dollars of inventory for 6 to 24 months, mould chambers on Roquefort with Penicillium roqueforti and Camembert with Penicillium camemberti requiring single-pass containment of the controlled mould aerosol, milk powder spray dryers at 180 to 220 degrees Celsius inlet running combustible dust under NFPA 660 and AS 3957 St 1 to St 2 explosibility class, infant formula clean rooms qualified to ISO 14644 Class 7 (Grade C equivalent) under FSANZ Standard 2.9.1 to prevent Cronobacter sakazakii contamination, ice cream IQF tunnels at minus 30 to minus 40 degrees Celsius on direct ammonia under AS/NZS 5149, glycol chillers serving every chilled room, steam boilers at 100 plus tonnes per hour combustion duty, and CIP stations spraying caustic soda, nitric acid and peracetic sanitiser at 75 to 85 degrees Celsius on a routine cycle.

From an HVAC ductwork engineering perspective, that combination places dairy in a small group of industries where every single failure mode that destroys galvanised steel ductwork is present in the same building. Wet floors and constant washdown attack the zinc coating. Caustic CIP at 2 to 5 percent NaOH at 75 to 85 degrees Celsius strips the coating chemically. Nitric and phosphoric acid CIP at 1 to 2 percent pits it. Sanitiser sprays with peracetic acid and sodium hypochlorite chloride-pit the steel. Ammonia mist condensing on duct interiors in the machinery room and IQF tunnel returns destroys zinc within weeks. Milk powder dust deposits on duct interiors with hygroscopic load and accelerates corrosion. Steam boiler flue gas runs above the safe service temperature for zinc. The only material that survives every one of these loads is 316L austenitic stainless steel with 2 to 3 percent molybdenum, fabricated to a hygienic standard that meets FSANZ Standard 3.2.3, EHEDG Doc 8 international hygienic design and the export-market regulators that the Australian dairy sector services into Asia, the Middle East, North America and Europe.

This guide walks the dairy process map from end to end — raw milk to finished good — calls out the temperature, humidity, hygiene, combustibility, refrigerant and CIP profile of each zone, names the Australian dairy operators we encounter in each segment, and finishes with the SBKJ machine configuration our Australian and regional fabricator customers use to deliver this ductwork to a finish that passes a Dairy Food Safety Victoria (DFSV) audit, a state safe-work inspector, a fire engineer and an export-channel regulator on the same day.

The article is written from the SBKJ engineering office in Box Hill North, Victoria. We supply HVAC duct fabrication machinery to fabricators across Australia and 60 plus other markets, and the dairy sector is one of our most engineering-intensive food manufacturing customer segments. Australian dairy generates approximately 8.5 billion litres of raw milk annually, with approximately 35 percent exported into Asia-Pacific, the Middle East, North America and Europe under a range of destination-market regulator regimes, and the regulator scrutiny on those export channels — particularly on infant formula — is now the most demanding regulatory burden on any Australian food manufacturer. The ductwork specification has to keep up. This guide is the SBKJ engineering team's current best-practice reference for that work.

Section 1 — The Australian dairy code stack

Before any duct geometry is sketched, the engineer must confirm the code stack that the facility will be audited against. For Australian dairy, that stack is the most layered in any food sector because it combines federal food safety regulation, state dairy authority regulation, refrigeration safety standards, combustible dust standards, clean room classification, international codex standards and export-market regulator standards. The minimum mandatory layers are below; export operators add several more on top.

AS 1668.2 — Mechanical ventilation in buildings

AS 1668.2 is the foundational Australian mechanical ventilation standard. For dairy it drives minimum outdoor air rates per occupant in the process and packaging halls, local exhaust requirements for steam, dust and chemical vapour, makeup air for pressure balance across the room cascade, and the duct construction class for fire and smoke control. AS 1668.2 routinely intersects the building fire engineering report and the local council mechanical services consent on a new build. Cross-reference our AS 1668.2 reference guide for the duct construction class table and leakage limits.

AS 4254 — Ductwork for air-handling systems

AS 4254 sets the Australian and New Zealand ductwork construction standard, in two parts: AS 4254.1 for flexible duct and AS 4254.2 for rigid metallic duct. For dairy, AS 4254.2 drives gauge selection, joint construction, leakage class (typically Class B or Class C for hygienic process duct), reinforcement, hangers and supports. Cross-reference our AS 4254 reference guide.

AS/NZS 1677 and AS/NZS 5149 — Refrigerating systems

AS/NZS 1677 is the historical Australian and New Zealand refrigeration safety standard, now largely superseded by the AS/NZS 5149 series which adopts ISO 5149 with Australasian variations. Both standards apply to ammonia (R-717) which is the dominant industrial refrigerant in Australian dairy. AS/NZS 5149.1 classifies refrigerants and occupancies; .2 covers design, construction and testing; .3 covers installation site requirements; .4 covers operation, maintenance and recovery. For HVAC ductwork the standard drives the ammonia machinery room classification (typically Class T2 for dairy), the continuous mechanical ventilation rate (0.014 cubic metres per second per square metre floor area), the emergency exhaust trigger and ramp (30 air changes per hour on 25 ppm ammonia detection), the duct material (316L stainless single-pass), the discharge location and the detection, alarm and shutdown logic.

AS 3957 and NFPA 660 — Combustible dust

Milk powder, whey powder, lactose and infant formula base powder are all combustible dusts with measurable Kst and Pmax values placing them in St 1 to St 2 explosibility class. AS 3957 is the Australian standard for safe handling of combustible particulate solids and is the primary domestic reference. NFPA 660 is the consolidated NFPA standard for combustible dust (combining the prior NFPA 61, 484, 654, 655 and 664) and is the international reference cited by Australian property insurers, fire engineers and dairy export-channel regulators. The standard drives dust hazard analysis on every enclosed dust handling volume, design of explosion venting per NFPA 68, explosion prevention per NFPA 69, spark detection, isolation, earthing and bonding per AS/NZS 60079.14, and 316L stainless ductwork rated for the reduced explosion pressure.

NFPA 68 and NFPA 69 — Explosion venting and prevention

NFPA 68 sets the design methodology for explosion vent panels on combustible dust handling equipment, sizing the vent area to limit reduced explosion pressure to within the structural rating of the protected volume. NFPA 69 covers explosion prevention by inerting, suppression and isolation where venting is impractical or unsafe. For dairy spray dryers, both standards typically apply — venting on the chamber and bag filter, suppression on the cyclone and downstream powder handling, and isolation valves throughout to prevent flame propagation.

AS/NZS 60079 — Hazardous areas

AS/NZS 60079 series covers hazardous area classification and electrical equipment for combustible dust and flammable gas atmospheres. For dairy, AS/NZS 60079.10.2 (dust atmospheres) classifies the milk powder spray dryer, bag filter, fluidised bed dryer, powder packing room and powder storage silo as Zone 20, 21 or 22 depending on dust persistence. AS/NZS 60079.14 covers electrical installation in hazardous areas, including earthing and bonding to less than 1 megohm at every duct joint to prevent electrostatic discharge ignition of lactose dust.

AS 1940 — Flammable and combustible liquids

AS 1940 covers storage and handling of flammable and combustible liquids and applies to any dairy plant with LPG, ethanol (rare in dairy but present in some flavour rooms), or solvent-based equipment cleaners. For most dairy operations the LPG store at the steam boiler room is the primary AS 1940 zone.

AS 4036 and AS 4037 — Boiler design and inspection

AS 4036 covers boiler and pressure vessel design and AS 4037 covers boiler inspection. State safe-work boiler inspectors enforce both on every dairy steam boiler installation. For HVAC the implication is the boiler room ventilation rate (30 air changes per hour outdoor air for combustion plus dilution), the combustion air duct sizing (14 cubic metres per second per megawatt boiler capacity for Australian gas-fired plant), and the flue stack material and discharge.

AS 1530.4 — Fire test of building elements

AS 1530.4 sets the fire test methodology for building elements including ductwork passing through fire-rated compartment lines. For dairy, the boundary between the production hall and the warehouse, the boundary between the boiler room and the production hall, and the boundary between the ammonia machinery room and adjacent spaces all typically require AS 1530.4 fire-rated dampers compliant with AS 1851 for inspection and testing.

AS 1851 — Routine service of fire protection systems

AS 1851 covers routine service and inspection of fire protection systems including fire dampers, smoke dampers, fire-rated penetrations and combustible dust suppression systems. For dairy, AS 1851 drives the annual drop-test of every fire damper, the documented inspection of every fire-rated penetration, and the periodic test of the suppression system on the milk powder spray dryer.

FSANZ Food Standards Code — 1.2.1, 3.2.2, 3.2.3 and 2.9.1

Food Standards Australia New Zealand publishes the federal Food Standards Code. Four standards are directly relevant to dairy HVAC: Standard 1.2.1 (labelling and consumer information) drives traceability documentation; Standard 3.2.2 (food safety practices and general requirements) drives the hygiene system; Standard 3.2.3 (food premises and equipment) drives the duct construction requirement — surfaces in contact with food or food preparation areas must be smooth, impervious, non-absorbent, easily cleanable and corrosion-resistant; and Standard 2.9.1 (infant formula products) drives the critical multi-tier composition, contaminant and microbiological standards for infant formula, supported by the ISO 14644 Class 7 clean room specification that operators in this segment run to in practice.

ISO 22000 and HACCP — Food safety management

ISO 22000 (Food Safety Management Systems) is the international standard for food safety management and is the certification basis for most Australian export-oriented dairy operators. HACCP (Hazard Analysis and Critical Control Points) from the Codex Alimentarius Commission of the FAO and WHO is the underlying hazard analysis methodology. Both drive the documented identification of critical control points where duct geometry, material or cleaning regime is a hazard control point.

Codex Alimentarius Dairy Standards — Codex STAN 72 and 156

Codex Alimentarius Dairy Standards set the international codex composition, microbiology and labelling standards for dairy products. Codex STAN 72 covers infant formula and is the primary international reference cited by FSANZ Standard 2.9.1. Codex STAN 156 covers follow-on formula. For HVAC the implication is the export-channel scrutiny on contamination prevention — particularly Cronobacter sakazakii prevention in infant formula manufacturing — which drives the clean room classification and the duct material and finish standard.

ISO 14644 — Clean room classification

ISO 14644 is the international clean room classification standard. For infant formula manufacturing and aseptic packaging the relevant class is ISO 14644 Class 7 (broadly equivalent to EU GMP Grade C at-rest) for the powder blending, dosing, filling and packing rooms. The standard drives the airborne particle count limit (352,000 particles of 0.5 micron or larger per cubic metre at rest), the in-operation particle count limit, the HEPA filtration requirement (H13 minimum), the air change rate (typically 6 to 10 per hour at this class), the pressure cascade and the qualification protocol.

ASHRAE Handbook Chapter 22 and Chapter 35

ASHRAE Handbook of Refrigeration Chapter 22 (Food, Beverages and Floral Products) and the Handbook of HVAC Applications Chapter 35 (Industrial Drying) are the international engineering references for dairy refrigerated processing and milk powder spray drying respectively. Australian consultants routinely cite both alongside the domestic standards.

Dairy Food Safety Victoria and other state dairy authorities

Each Australian state has a dairy food safety authority operating under the model Food Act and the FSANZ Food Standards Code. Dairy Food Safety Victoria (DFSV) regulates the Victorian dairy industry which accounts for over 60 percent of Australian production. Queensland (Safe Food Production Queensland), New South Wales (NSW Food Authority dairy division), South Australia (Dairy Authority of SA), Western Australia (Department of Primary Industries and Regional Development), and Tasmania (Dairy Industry Authority of Tasmania) operate the state-level licensing. Every dairy plant operating in Australia holds a state dairy authority licence and is audited against the licence conditions annually. For HVAC the implication is the documented hygiene programme, the duct material certification, the CIP and inspection programme, and the annual audit pack.

TGA and FDA cGMP for export channels

Australian infant formula export to the United States falls under FDA cGMP (current Good Manufacturing Practice) and the FDA Infant Formula Act. Major Asia-Pacific destination markets each operate their own facility-level infant formula registration regime with on-site audit, and EU destination markets operate under EU baby food regulation. Pharmaceutical-adjacent infant formula and medical nutrition products may fall under TGA (Therapeutic Goods Administration) biological reference. The HVAC specification typically runs to the strictest of the applicable regulators.

Section 2 — Raw milk receival and storage

The dairy process starts at the truck dock. Tanker trucks — typically B-double 30,000 to 45,000 litre payloads from Victorian, Tasmanian, NSW, Queensland, South Australian and Western Australian dairy farms — arrive on a tight schedule, are tested for somatic cell count, fat, protein, antibiotic residue and bacterial count, then offload via a sanitised pumping connection into the raw milk silo. The receival hall is a wet zone with constant washdown of the truck dock, the pumping skid, the connecting hoses and the surrounding floor.

Receival hall HVAC

Receival hall design point is 18 to 22 degrees Celsius and 50 to 65 percent relative humidity, 4 to 6 air changes per hour outdoor air, with local extract over the pumping skid to capture trace lactic odour and milk aerosol. Pressure cascade slightly negative to adjacent process halls (minus 5 Pa) to contain any odour. Duct material 304 stainless on the supply because the air is clean, 316L stainless on the local extract because milk aerosol condensate plus daily caustic washdown destroys 304 over a 5 to 10 year service life. Floor drainage continuous, with stainless trench drains and stainless duct hangers spaced for the AS 4254 SMACNA standard on stainless — maximum 1.8 metre support spacing.

Raw milk silo room

Raw milk is stored at 4 to 6 degrees Celsius in 50,000 to 200,000 litre stainless silos pending separation, pasteurisation or further processing. The silo room HVAC is essentially a chilled food zone with 8 to 12 ACH, 6 to 8 degrees Celsius room ambient, 60 to 70 percent relative humidity, 304 stainless supply duct externally insulated with closed-cell PIR and continuous vapour barrier, 316L stainless local extract above any open transfer or sampling points. AS/NZS 5149 ammonia or glycol secondary refrigeration. Pressure neutral to adjacent process to avoid drawing odour from the receival hall or losing chilled air to warmer adjacent zones.

Australian raw milk supply network

Australian raw milk production sits at approximately 8.5 billion litres per year (Dairy Australia statistics). The supply network is concentrated in Victoria (Gippsland, Northern Victoria, Western Victoria), Tasmania, southern New South Wales (Riverina and Bega Valley), south-east Queensland (Darling Downs), South Australia (Mount Gambier region) and southern Western Australia (Manjimup, Margaret River). The major processors operating raw milk receival at scale include:

• Saputo Dairy Australia. Canadian-listed Saputo Inc. owns the former Murray Goulburn, Warrnambool Cheese and Butter (WCB) and Devondale operations. Sites at Allansford (VIC), Cobram (VIC), Maffra (VIC), Smithton (TAS), Burnie (TAS), Leongatha (VIC), Koroit (VIC) and Rochester (VIC). Saputo is the largest dairy processor in Australia by raw milk intake.
• Bega Cheese (ASX:BGA). Acquired Lion Dairy and Drinks in 2021 to consolidate a major position in fresh and processed dairy. Sites at Bega (NSW HQ), Tatura (VIC, via the Tatura Milk Industries subsidiary), Kingaroy (QLD), Strathmerton (VIC), Coburg (VIC), Crestmead (QLD) and Penrith (NSW).
• Fonterra Australia. Australian subsidiary of the New Zealand-headquartered farmer cooperative Fonterra Co-operative Group. Operates the Stanhope (VIC), Cobden (VIC) and Wynyard (TAS) sites. Several Fonterra Australia sites have recently transferred to Saputo and Bega under sector consolidation.
• Pauls Pure Goodness (Lactalis). Australian operating arm of French-listed Lactalis. Brisbane HQ with sites at Crestmead (QLD), Lytton (QLD) and Bentley (WA). Parmalat Australia is also part of the Lactalis group following acquisition.
• Bulla Dairy Foods. Privately-held Australian family-owned operator, sites at Colac (VIC) and Toowoomba (QLD). Largest Australian-owned ice cream maker.
• Norco Co-operative. 100-year-old farmer-owned cooperative based at Lismore (NSW), serving the northern NSW and south-east Queensland dairy region.
• Burra Foods. Privately-held processor at Korumburra (VIC), specialising in infant formula base, cream and butter.
• Tatura Milk Industries. Bega Cheese subsidiary operating from Tatura (VIC).
• Camperdown Dairy International. Victorian operator focused on infant formula.

Several Australian-listed dairy operators — Bega Cheese, a2 Milk, Bubs Australia, Synlait (NZ-listed but ASX cross-listed), Beston Global Food Company — trade on the ASX with varying ownership structures. Some operators have changed hands recently, with Saputo and Bega growing through acquisition of legacy assets.

Section 3 — Pasteurisation, UHT and aseptic packaging

HTST and LTLT pasteurisation

Pasteurisation is the controlled heat treatment of raw milk to destroy pathogenic organisms while preserving flavour, nutritional value and processability. Two protocols dominate Australian dairy: HTST (High Temperature Short Time) at 72 to 75 degrees Celsius for 15 seconds in a plate heat exchanger for fresh drinking milk, and LTLT (Low Temperature Long Time) at 63 to 65 degrees Celsius for 30 minutes in a batch vat for cream and specialty products. The pasteuriser releases latent heat plus a small mass of steam at the regenerator and the holding tube vent. The pasteurisation hall HVAC specification is 18 to 22 degrees Celsius and 50 to 65 percent relative humidity, 6 to 10 ACH, with local extract over the pasteuriser plate exchanger and the holding tube to capture latent heat and steam.

Duct material is 316L stainless on the local extract because of the routine caustic CIP washdown on the pasteuriser and the surrounding floor, 304 stainless on the supply, and the hall is held slightly negative to adjacent dry zones (minus 5 Pa) to contain odour. Pasteuriser glycol cooling on the regenerator runs via the central glycol chiller plant at 4 to 8 degrees Celsius.

UHT plant — the 140 to 150 degrees Celsius step

Ultra-High Temperature (UHT) processing pushes milk through 140 to 150 degrees Celsius for 2 to 4 seconds to commercially sterilise the product for shelf-stable aseptic packaging with a 6 to 9 month ambient shelf life. Two heating methods dominate: indirect UHT via tubular or plate heat exchanger, and direct UHT via steam injection or steam infusion. Direct UHT adds approximately 10 to 15 percent steam to the product mass which is then flash-cooled in a vacuum vessel to remove the added water and recover concentration. Both methods release substantial heat to the surrounding room.

The UHT plant hall HVAC specification is 18 to 22 degrees Celsius and 45 to 55 percent relative humidity, 8 to 12 ACH, with local extract over the steam injection chamber, the flash vessel and the holding tube to capture latent heat and steam. The flash vessel vent discharges through 316L stainless duct to outdoor. Pressure cascade slightly negative (minus 5 Pa) to the aseptic packaging hall to prevent transient excursions into the aseptic zone.

Aseptic filler enclosure — H2O2 sterilant management

The aseptic filler — typically TetraPak A3/Speed, Sidel Combi, KHS Innofill or SIG Combibloc on the Australian dairy market — receives commercially sterile product from the UHT plant and packages it into a sterile carton or bottle in a contained aseptic chamber. Sterilisation of the carton or bottle interior uses 30 to 35 percent hydrogen peroxide spray plus heat at approximately 280 degrees Celsius for less than 1 second, vapourising the H2O2 inside the package. A small residual carry-over enters the surrounding room as a vapour.

Safe Work Australia Workplace Exposure Standard (WES) for hydrogen peroxide is 1 ppm Short-Term Exposure Limit (STEL). The smell threshold is around 0.1 ppm so operators detect the gas well below the WES, but chronic exposure is the engineering control concern. SBKJ specification for the aseptic filler enclosure is a local extract hood at the filler discharge sized to capture all H2O2 vapour at 0.5 to 1.0 metres per second face velocity, ducted through a 316L stainless single-pass exhaust train to a catalytic decomposer or activated carbon scrubber, with no recirculation. The catalytic decomposer reduces H2O2 to water and oxygen at the discharge stack, with stack monitoring for residual H2O2 to verify performance.

The surrounding aseptic packaging hall runs ISO 14644 Class 7 (Grade C equivalent) clean with HEPA H13 supply, positive pressure plus 5 to plus 10 pascal relative to adjacent rooms, temperature 18 to 22 degrees Celsius and relative humidity 35 to 50 percent. Filler exhaust discharge to outdoor minimum 3 metres above roof, 8 metres horizontal from any intake, oriented away from prevailing wind. WES monitoring per Safe Work Australia annual exposure audit.

Australian UHT and aseptic operators

UHT milk has become a substantial Australian export category, particularly into Asia where ambient-stable dairy is preferred over fresh refrigerated. Major UHT operators include:

• Pauls Pure Goodness (Lactalis). UHT lines at Crestmead (QLD) and Lytton (QLD).
• Bega Cheese. UHT at Tatura (VIC) and Penrith (NSW), including Lion-acquired assets.
• Saputo Dairy Australia. UHT capacity across multiple sites.
• Norco Co-operative. UHT for export and domestic ambient market.
• The a2 Milk Company (ASX:A2M). Substantial UHT product range under the a2 brand, manufactured under contract at Synlait Milk in New Zealand and at Australian co-packers.
• Bubs Australia (ASX:BUB). UHT goat milk and specialty UHT for infant and toddler nutrition.

Section 4 — Cream, butter and chilled products

Cream separator

Cream separation runs via continuous centrifugal separator at 50 to 55 degrees Celsius pasteuriser-warm milk feed, splitting the milk into cream (35 to 40 percent fat) and skim (less than 0.5 percent fat). The separator hall HVAC is 12 to 16 degrees Celsius, 60 to 70 percent relative humidity, 8 to 12 ACH, with 316L stainless supply and extract because routine caustic CIP washdown is heavy. Cream is then immediately chilled to 8 to 10 degrees Celsius and held in the cream room pending butter production or cream packaging.

Butter churn and butter packing

Butter is produced by churning chilled cream at 8 to 10 degrees Celsius until the butterfat coalesces and separates from the buttermilk. Modern continuous butter machines (Fritz machines) run at 12 to 16 degrees Celsius churn temperature with local extract capturing butter aroma and trace moisture. Salted or unsalted butter is then formed and chilled-packed at 6 to 8 degrees Celsius.

The butter hall HVAC specification is 12 to 16 degrees Celsius and 60 to 70 percent relative humidity, 8 to 12 ACH, with local extract above the churn. The butter packing hall runs at 8 to 10 degrees Celsius with the same air change rate. Duct material 316L stainless throughout because of CIP and washdown. AS/NZS 5149 ammonia or glycol secondary refrigeration. Insulated externally with closed-cell PIR 50 to 100 mm and continuous foil vapour barrier on the warm side.

Australian butter and cream operators

Major Australian butter and cream operators include Saputo (Allansford, Maffra), Bega Cheese, Bulla Dairy (Colac and Toowoomba — major cream supplier), Burra Foods (Korumburra) and Norco. Devondale-branded butter remains a flagship product for the Saputo-owned former Murray Goulburn business.

Section 5 — Yogurt fermentation and chilled set

Yogurt fermenter hall

Yogurt is produced by inoculating pasteurised milk with thermophilic lactic acid bacteria — primarily Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus — and holding at 40 to 45 degrees Celsius for 4 to 6 hours until the pH drops to approximately 4.5 and the milk proteins coagulate into the yogurt gel. Some yogurts add Bifidobacterium and other probiotic strains; Greek-style yogurt then undergoes a straining or membrane separation step to concentrate the protein.

The fermenter hall HVAC specification is 40 to 45 degrees Celsius room ambient or fermenter-jacket controlled depending on the system design, 60 to 75 percent relative humidity, 6 to 10 ACH, with local extract over the fermenter tanks to manage the lactic acid fermentation odour at 0.3 to 0.5 m/s face velocity. The exhaust is routed via 316L stainless duct to atmospheric discharge. After fermentation the product is rapidly chilled to 4 to 6 degrees Celsius for set, then packed at 6 to 10 degrees Celsius.

Yogurt packing hall

Yogurt packing runs at 6 to 10 degrees Celsius with 8 to 12 ACH, 316L stainless supply and extract, and HEPA H13 supply filtration on premium product lines (probiotic, organic, infant-targeted). Pressure cascade slightly positive to adjacent rooms (plus 5 Pa).

Australian yogurt operators

The Australian yogurt market is led by:

• Chobani Australia. Dandenong (VIC) primary site plus Strathmerton (VIC) for Greek yogurt. Biggest yogurt brand by volume in Australia.
• Bega Yoplait. Yoplait yogurt manufactured by Bega Cheese under licence.
• Saputo Yopro. High-protein yogurt brand under Saputo Dairy Australia.
• The Collective Yogurt. Premium yogurt brand with Australian and NZ operations.
• Five:am Organic. Premium organic yogurt brand.
• Jalna Yogurt. Australian-owned premium yogurt with Melbourne production.

Section 6 — Cheese curd, pressing and maturation

Cheese curd hall

Cheese production runs through curd cutting, draining, salting, pressing and moulding before transfer to the maturation room. The curd hall HVAC specification is 14 to 18 degrees Celsius and 70 to 80 percent relative humidity, 6 to 10 ACH, with 316L stainless duct throughout because the wet floor and routine washdown destroy galvanised within months. Local extract above the cheese vats captures whey vapour and the characteristic dairy fermentation odour. Discharge through 316L stainless single-pass duct to outdoor.

Cheese maturation rooms — the long-cycle inventory

Cheese maturation is the controlled storage of cheese under specific temperature, humidity and air movement conditions for periods ranging from days to years, during which biochemical and microbiological changes develop the flavour, texture and rind characteristic of the finished cheese variety.

The HVAC specification varies by variety:

• Cheddar maturation. 8 to 12 degrees Celsius, 80 to 88 percent relative humidity, 4 to 8 ACH, hold for 6 to 24 months for mature and vintage Cheddar. Block-cured Cheddar typically vacuum-packed before maturation, reducing the rind moisture management burden. Loose-cured traditional Cheddar requires close humidity control to prevent rind cracking.
• Camembert and Brie. 11 to 13 degrees Celsius, 85 to 92 percent relative humidity, 4 to 8 ACH, hold for 30 to 50 days for the Penicillium camemberti white-mould rind to develop. Single-pass exhaust to outdoor to contain mould aerosol.
• Blue cheese (Stilton, Roquefort-style, Gorgonzola-style). 8 to 12 degrees Celsius, 85 to 95 percent relative humidity, 4 to 8 ACH, hold for 60 to 120 days for Penicillium roqueforti blue-mould development. Single-pass exhaust to outdoor — the controlled mould aerosol must not contaminate other cheese varieties in the same plant.
• Feta and white-brined. 4 to 8 degrees Celsius in brine, 80 to 90 percent RH, hold for 60 to 90 days. 316L stainless duct because brine vapour is heavily chloride-loaded.
• Parmesan, Grana and Pecorino hard cheese. 12 to 18 degrees Celsius, 80 to 88 percent RH for the long aging phase (12 to 36 months), then a drier final phase at 50 to 65 percent RH for surface drying. Hard cheese maturation rooms are physically large — thousands of square metres — with thousands of wheels stored on timber or stainless racking.

Across all cheese maturation, the HVAC engineering challenges are: holding the narrow humidity band against the natural moisture release of the cheese, controlling air movement at the cheese surface to 0.1 to 0.3 m/s (fast enough to remove moisture and CO2 from cheese respiration, slow enough not to dry the rind), HEPA H13 supply filtration to exclude wild moulds and spoilage organisms, single-pass exhaust on mould-ripened varieties to contain the controlled mould aerosol, and 316L stainless duct throughout because high humidity plus CIP cleaning destroys galvanised within months.

Cheese drying rooms — the hard cheese specialty

Hard cheeses including Parmesan, Grana Padano, Pecorino and aged Cheddar undergo a final drying phase at lower humidity (50 to 65 percent RH) before sale. This phase reduces surface moisture, hardens the rind and intensifies flavour. The drying room HVAC runs cooler (10 to 14 degrees Celsius) and drier than the maturation rooms, with similar 316L stainless duct throughout.

Australian cheese operators

Australian cheese manufacturing is led by:

• Bega Cheese. Flagship Bega Cheddar product, plus a broad cheese portfolio. Bega (NSW), Strathmerton (VIC), Coburg (VIC), Tatura (VIC).
• Saputo Dairy Australia. Coon Cheese (since renamed Cheer Cheese), Mil Lel Parmesan, plus the King Island Dairy and other premium cheese assets. Sites at Cape Wickham (TAS, King Island Dairy), Allansford, Burnie, Smithton and Koroit.
• Fonterra Australia. Mainland-branded cheese.
• Bulla Dairy Foods. Tasty and Vintage cheese alongside cream and butter from Colac (VIC).
• Tarago River Cheese Company. Premium Gippsland cheese specialist.
• Berrys Creek Gourmet Cheese. South Gippsland premium cheese maker.
• That's Amore Cheese. Melbourne-based Italian-style cheese maker (mozzarella, ricotta, burrata, scamorza).
• Jindi Cheese. Gippsland soft cheese specialist (Brie, Camembert).
• Maffra Cheese Company. Gippsland specialty cheese.
• L'Artisan Cheese. South-western Victoria artisan cheese maker.
• Pyengana Dairy. Tasmanian heritage Cheddar specialist.

Section 7 — Milk powder spray drying — the combustible dust engineering problem

The spray drying process

Milk powder is produced by spray drying concentrated milk or whey at high inlet temperature in a tall vertical drying chamber. Standard process: pre-concentrated milk (35 to 50 percent total solids) is atomised through a high-pressure nozzle or rotary atomiser into a chamber with hot air entering at 180 to 220 degrees Celsius and exiting at 80 to 90 degrees Celsius. The fine droplets dry to powder in 5 to 30 seconds depending on chamber geometry, falling to the chamber bottom and conveyed through a cyclone and bag filter for fines recovery, then through a fluidised bed for final moisture adjustment and cooling, and finally to packing.

For skim milk powder, whole milk powder, whey powder and infant formula base powder, the chamber, cyclone, bag filter, fluidised bed and powder handling lines all contain a combustible dust cloud during operation. Kst values are around 100 to 170 bar.metre per second placing the materials in St 1 to St 2 explosibility class, and the Pmax (maximum explosion pressure) is approximately 7 to 9 bar absolute.

The dust hazard analysis under AS 3957 and NFPA 660

The first engineering step on any spray dryer specification is a documented dust hazard analysis (DHA) per AS 3957 and NFPA 660. The DHA identifies every enclosed dust handling volume in the plant — spray dryer chamber, cyclone, bag filter, fluidised bed, pneumatic conveying lines, powder packing line dust extract, powder storage silo — quantifies the Kst, Pmax and minimum ignition energy of the material, classifies the dust ATEX zone (Zone 20, 21 or 22) and triggers the design of the protective measures.

NFPA 68 explosion venting — sizing and panel selection

NFPA 68 (Standard on Explosion Protection by Deflagration Venting) sizes the vent area required on each enclosed dust volume to limit the reduced explosion pressure (Pred) to within the structural rating of the vessel or duct. For a typical milk powder spray dryer chamber with Kst 100 to 130 bar.metre per second, Pmax 7 to 8 bar, a structural design pressure of 0.2 bar gauge and a chamber volume of 100 cubic metres, NFPA 68 sizes approximately 8 to 12 square metres of frangible or hinged vent panel area on the chamber top or sides, oriented to discharge to a safe outdoor location through a vent duct of equal area and no more than 6 metres long.

Vent panel options include frangible polymer panels rated to burst at 0.05 to 0.10 bar gauge, hinged stainless panels with a magnetic latch rated to release at the same pressure, and rupture discs for smaller volumes. The vent duct itself is 316L stainless rated for the reduced explosion pressure with full rounded inlet to minimise pressure rise during venting.

NFPA 69 explosion prevention — inerting and suppression

NFPA 69 (Standard on Explosion Prevention Systems) covers explosion prevention by inerting, suppression and isolation where venting is impractical or unsafe. For dairy spray dryers, NFPA 69 typically applies to the cyclone and downstream powder handling where venting to outdoor is geometrically difficult, and to indoor powder packing rooms where a vented explosion would be unacceptably dangerous to occupants.

Inerting uses nitrogen blanket on the dryer outlet, the cyclone and the bag filter to keep the oxygen concentration below the limiting oxygen concentration (LOC) for the dust (typically 8 to 12 percent O2 for milk powder, well below atmospheric 21 percent). Chemical suppression uses HRD (high-rate-discharge) bottles of suppressant powder triggered by pressure rise detection, releasing within 20 to 30 milliseconds and quenching the deflagration before it develops destructive pressure.

Isolation valves close on detection to prevent flame propagation between connected volumes — e.g. preventing a deflagration in the cyclone from propagating back to the spray dryer chamber or forward to the bag filter. Fast-acting isolation valves with under 100 millisecond closure are standard.

Spark detection and water spray

Spark detection at the spray dryer outlet duct uses infrared sensors that detect any spark or hot particle in the airstream and trigger a water spray quench within 20 to 30 milliseconds. The water spray nozzles are stainless and the spray duty is sized to wet the entire duct cross-section in the first 100 milliseconds. The system is interlocked with the dryer outlet damper to close immediately on detection, isolating the upstream dryer from the downstream cyclone and bag filter.

Bag filter explosion vent and isolation

The bag filter downstream of the cyclone collects the fine powder fines and is itself a primary deflagration risk because the dust concentration inside the filter housing is high during normal operation. NFPA 68 sizes a vent panel on the bag filter housing typically 2 to 4 square metres for a standard dairy bag filter, discharging to outdoor via a vent duct. NFPA 69 isolation valves on the inlet and outlet prevent flame propagation. The hopper discharge is gas-tight to prevent oxygen ingress during the rotary valve cycle.

Earthing, bonding and ATEX electrical

AS/NZS 60079.14 requires every component of the dust handling system to be earthed and bonded to less than 1 megohm resistance to prevent electrostatic discharge ignition of the dust cloud. Every duct flange, every support hanger, every instrument connection must be bonded. The plant earthing system must be verified annually with documented resistance measurement at every test point. All electrical equipment in Zone 20, 21 or 22 must be ATEX-certified to the appropriate temperature class (typically T4 or T3 for milk powder).

Powder packing room — 25 kg, 5 kg, retail, bulk

Powder packing runs through bulk bag (1 to 1.5 tonne FIBC), 25 kg paper sack, 5 kg foil pouch, retail tin and bulk container formats. Each format has its own dust release profile and local extract specification.

• Bulk bag (FIBC) packing: enclosed loading station with local extract at the fill spout at 1.0 to 1.5 m/s face velocity, routed via 316L stainless duct to a dedicated bag filter with NFPA 68 vent. NFPA 660 dust hazard analysis applied.
• 25 kg paper sack: rotary sack filler with local extract over the sack mouth, dust booth around the filler, 316L stainless duct to bag filter.
• 5 kg foil pouch and retail tin: cleaner packing format with reduced dust release but still requiring local extract and bag filter under NFPA 660.
• Bulk container (sea container direct loading): high-volume dust release station requiring substantial local extract and bag filter capacity, typically the dustiest part of the packing operation.

Powder storage silo

Bulk milk powder storage in 5,000 to 50,000 tonne capacity silos requires NFPA 660 dust hazard analysis on the silo top dust collector, NFPA 68 vent panel on the silo top, NFPA 69 isolation on connecting pneumatic lines, spark detection on inlet ducts, and AS/NZS 60079.14 earthing and bonding throughout. Inerting with nitrogen blanket is standard on the silo headspace to reduce the explosion risk.

Australian milk powder operators

Australian milk powder production is concentrated in Victoria and Tasmania. Major operators:

• Saputo Dairy Australia. Substantial milk powder capacity at Allansford (VIC) and Smithton (TAS). The Allansford site is one of the largest milk powder plants in the southern hemisphere.
• Fonterra Australia. Milk powder at Stanhope (VIC) and Wynyard (TAS).
• Bega Cheese. Milk powder via the Tatura Milk Industries subsidiary and the recently acquired Fonterra assets.
• Bellamy's Australia. Tasmanian milk powder operation for infant formula base.
• Burra Foods. Korumburra (VIC) infant formula base powder.
• Camperdown Dairy. Victorian milk powder for infant formula.

Section 8 — Infant formula manufacturing — the ISO 7 Grade C clean room

Why infant formula is the toughest spec in dairy HVAC

Infant formula is the most regulated category in dairy manufacturing globally. The combination of the consumer profile (infants are the most vulnerable food consumers), the historical contamination incidents (Cronobacter sakazakii outbreaks have caused infant deaths in multiple jurisdictions), and the export channel scrutiny (multiple Asia-Pacific destination market registrations, FDA Infant Formula Act, EU baby food regulation) drives a multi-tier regulatory burden:

• FSANZ Standard 2.9.1 — Infant Formula Products. The federal Australian and NZ standard sets composition, contaminant, microbiological and labelling requirements.
• Codex STAN 72 — Standard for Infant Formula and Formulas for Special Medical Purposes Intended for Infants.
• Codex STAN 156 — Standard for Follow-up Formula.
• FDA Infant Formula Act (US export). 21 CFR 106 and 21 CFR 107.
• Asia-Pacific destination market infant formula registration. Mandatory facility-level registration for infant formula exported to major Asia-Pacific destination markets, with on-site audit by destination-market regulators. Specification typically more onerous than domestic.
• EU Baby Food Regulation. EU Directive 2006/141/EC and successor regulations.
• TGA biological reference. For pharmaceutical-adjacent medical nutrition.

The HVAC ductwork specification typically runs to the strictest of the applicable regulators. For Australian infant formula plants exporting to major Asia-Pacific destination markets, the destination-market facility audit is usually the binding requirement, and the regulator inspectors examine clean room qualification, HEPA integrity, pressure cascade, surface finish and CIP records in detail.

ISO 14644 Class 7 (Grade C) specification

The powder blending, dosing, filling and packing rooms in an infant formula plant typically run to ISO 14644 Class 7 (broadly equivalent to EU GMP Grade C at-rest). The specification:

• Airborne particle count at rest. Maximum 352,000 particles ≥ 0.5 micron per cubic metre. 2,930 particles ≥ 5 micron per cubic metre.
• Airborne particle count in operation. Maximum 3,520,000 particles ≥ 0.5 micron per cubic metre.
• Air change rate. 6 to 10 per hour minimum, often 15 to 20 in practice to achieve the in-operation particle count under heavy powder release.
• HEPA filtration. H13 minimum (99.95 percent at 0.3 micron MPPS) on terminal supply, factory tested and on-site PAO challenge at commissioning per IEST-RP-CC034.
• Pressure cascade. Plus 10 to plus 15 Pa positive to adjacent process rooms. Door-side pressure indicators and BMS alarm at 50 percent design.
• Temperature. 18 to 22 degrees Celsius.
• Relative humidity. 35 to 50 percent.
• Personnel airlock. Gowning sequence with step-over bench, hand-wash, sanitiser, dedicated cleanroom gown and overshoe.
• Material airlock. Pass-through hatch with interlocked doors.
• Cleaning regime. Daily wet wipe, weekly deep clean, monthly surface swab. Documented under HACCP.

Cronobacter sakazakii prevention

Cronobacter sakazakii is an opportunistic pathogen that has caused severe and sometimes fatal infections in infants consuming contaminated powdered infant formula. The organism is environmentally resilient, surviving in dry powder for months and tolerant of standard CIP chemistries. The control strategy combines: ingredient testing on inbound powder and intermediates, environmental swab programme on the clean room surfaces and floor drains, HEPA H13 supply filtration to exclude the organism from the production air, single-pass exhaust on dust-generating activities, pressure cascade to maintain clean-to-dirty airflow direction, sealed product packaging immediately after fill, and final-product release testing.

For HVAC the implication is that the duct interior and the supply terminal must remain clean and dry. Any pooled condensate on duct interiors creates a Cronobacter reservoir. Any HEPA breach allows the organism to enter the clean room. Any pressure cascade failure allows contaminated air to flow inwards from the surrounding process areas. The HVAC engineering must prevent all three.

Infant formula blending and filling

Infant formula blending combines the base milk powder (typically reconstituted skim milk powder plus added whey, lactose, vegetable fats, vitamins, minerals and other ingredients) and dose-fills into the retail can or pouch. The blending and filling lines operate inside the ISO 14644 Class 7 clean room with the specification above. Dust release during dosing and filling is captured at local extract hoods at 0.5 to 1.0 m/s face velocity and routed through 316L stainless single-pass exhaust to bag filter and atmospheric discharge.

Australian infant formula operators

Australian infant formula manufacturing for both domestic and export markets includes:

• Bellamy's Australia. Tasmanian organic infant formula specialist, recently consolidated under new ownership.
• The a2 Milk Company (ASX:A2M). Premium A1-protein-free infant formula brand, manufactured under contract at Synlait Milk in New Zealand and at Australian co-packers, with substantial Asia-Pacific export.
• Synlait Milk. New Zealand-headquartered manufacturer producing a2 Milk infant formula and other brands. ASX cross-listed.
• Bubs Australia (ASX:BUB). Goat milk infant formula specialist at Deloraine (TAS) and other co-packers.
• Burra Foods. Infant formula base powder and contract manufacturing at Korumburra (VIC).
• Camperdown Dairy International. Victorian infant formula manufacturer.
• Beston Global Food Company (ASX:BFC). South Australian dairy operator with infant formula capability.

The Infant Nutrition Council (INC) is the peak industry body for the Australian and NZ infant formula sector.

Section 9 — Whey, lactose and protein concentrate

Whey processing

Whey is the liquid by-product of cheese making, containing approximately 6 percent solids (lactose, whey proteins, minerals). Modern dairy plants do not discard whey — they concentrate it via ultrafiltration (UF) and reverse osmosis (RO) into whey protein concentrate (WPC, 35 to 80 percent protein), whey protein isolate (WPI, 90 percent plus protein) and lactose powder. The WPC and WPI dry products are exported into the global protein supplement market.

Whey concentration runs at 8 to 15 degrees Celsius wet processing in a refrigerated UF/RO plant hall. The WPC/WPI spray dryer runs identically to the milk powder spray dryer with the same NFPA 660 combustible dust controls. Lactose crystallisation and drying generates additional dust with similar Kst and explosibility characteristics.

Australian whey and lactose operators

Saputo (Allansford, Koroit), Bega (Tatura), Fonterra (Stanhope), Burra Foods and several specialist operators run WPC, WPI and lactose drying capacity in Australia.

Section 10 — Ice cream manufacturing — the cryogenic end of dairy

Ice cream process

Ice cream is produced by blending a mix of milk solids, sugar, fat (typically dairy fat from cream and milk powder, occasionally vegetable fat), stabilisers and flavour, pasteurising, homogenising, ageing the mix at 4 to 6 degrees Celsius, then freezing in a scraped-surface freezer to a soft-serve consistency at minus 5 to minus 8 degrees Celsius core, extruding into the final shape (bar, cone, tub, slab), then hardening in a tunnel at minus 30 to minus 40 degrees Celsius to a fully solid eating-quality product.

IQF (individual quick freeze) tunnel

The hardening tunnel runs at minus 30 to minus 40 degrees Celsius internal recirculating air at 30 to 60 ACH internal recirculation, achieved via direct ammonia (R-717) evaporator coils per AS/NZS 5149 or LN2 cryogenic spray for very-high-throughput lines. Duct material 316L stainless rated for low-temperature thermal cycling with closed-cell PIR or PUR insulation 150 to 200 mm thickness and continuous foil vapour barrier on the warm side. The tunnel envelope is sandwich panel construction with stainless internal face. Defrost cycle accommodation with pitched supply duct bottom panels toward drain traps and heat-traced condensate lines through unconditioned space.

Extrusion and filling

Magnum-style bars, Cornetto cones, tubs and slabs are formed at minus 5 to minus 8 degrees Celsius soft-serve from the scraped-surface freezer outlet, then either dipped in coating (chocolate, yoghurt, white chocolate) or filled into the final container before transfer to the hardening tunnel. The filling hall HVAC runs at 12 to 16 degrees Celsius (cool enough to prevent product melt, warm enough for operator comfort), 8 to 12 ACH, with 316L stainless supply and extract.

Hardening tunnel

Post-extrusion the product passes through the hardening tunnel at minus 30 degrees Celsius for the time required to bring the product core temperature down to dispatch specification (typically minus 18 degrees Celsius). Tunnel residence time ranges from 20 minutes for individual bars to several hours for tubs.

Australian ice cream operators

The Australian ice cream market is led by:

• Bulla Dairy Foods. Colac (VIC) and Toowoomba (QLD). Largest Australian-owned ice cream maker, full range from individual sticks to family tubs.
• Streets (Unilever). Iconic Australian ice cream brand (Paddle Pop, Splice, Magnum). The Streets ice cream business was recently sold by Unilever to Froneri (the Nestle-PAI partnership), with manufacturing at Tooting Bec/Bayswater (VIC).
• Peters Ice Cream (Froneri-Nestle). Iconic Drumstick, Frosty Fruits and other heritage brands. Now under Froneri ownership.
• Connoisseur (Froneri). Premium ice cream brand also under Froneri ownership following the Streets/Peters acquisitions.
• Ben & Jerry's (Unilever). US premium brand with Australian distribution and contract co-packing.
• Maggie Beer Ice Cream. South Australian premium brand under Maggie Beer Products.

The Australian Ice Cream Association (AICA) is the peak industry body.

Section 11 — Ammonia refrigeration machinery rooms

Why ammonia dominates dairy refrigeration

Ammonia (R-717) is the dominant industrial refrigerant in Australian dairy because of its thermodynamic efficiency, zero global warming potential, zero ozone depletion potential, low cost and operational maturity. The trade-off is toxicity and flammability — ammonia is classified as B2L under ASHRAE 34 and AS/NZS 5149 (toxic and lower flammability) — which drives a substantial safety engineering envelope around the machinery room.

Machinery room ventilation under AS/NZS 5149

The ammonia machinery room is classified under AS/NZS 5149.3 typically as Class T2 occupancy. Mechanical ventilation requirements:

• Normal continuous ventilation. 0.014 cubic metres per second per square metre of floor area, mechanical, single-pass to outdoor, no recirculation.
• Emergency exhaust on ammonia detection. 30 air changes per hour ramping up immediately on detection trip.
• Ammonia detection. Low-level sensors at floor level (ammonia is heavier than air at low concentrations) and high-level sensors at ceiling. Alarm at 25 ppm. Audible and visual evacuation alarm at 150 ppm. Emergency exhaust full ramp at 250 ppm. Compressor automatic shutdown at 1000 ppm.
• Duct material. 316L stainless single-pass to outdoor. Galvanised fails within weeks under wet ammonia mist exposure.
• Discharge location. Minimum 3 metres above roof, 8 metres horizontal from any intake, 15 metres horizontal from any pedestrian path or occupied building opening, oriented away from prevailing wind. Stack diffuser to disperse on emergency vent.
• Fan redundancy. N+1 minimum, UPS-backed control, manual emergency stop at every exit door.
• Safety equipment. Eye wash and emergency shower per AS 3859 within 10 metres of any operating position. Self-contained breathing apparatus (SCBA) at the machinery room entrance.
• Pressure relief. Refrigerant pressure-relief valve discharge piped through 316L stainless vent line to outdoor terminal with diffuser, sized per AS/NZS 5149.2.

Detection calibration and audit

Ammonia detectors require annual calibration with documented sign-off, typically performed by the refrigeration contractor or a specialist calibration service. The state safe-work authority (WorkSafe Victoria, SafeWork NSW, etc) inspects ammonia machinery rooms periodically and can shut down the operation on a non-conforming inspection. Australian dairy operators with substantial ammonia inventories — Saputo Allansford and Cobram, Bega Tatura, Fonterra Stanhope, Bulla Colac, Pauls Crestmead and others — all maintain documented ammonia detection calibration and machinery room ventilation testing.

Section 12 — Glycol chiller plant

Most dairy plants run a centralised glycol chiller plant at 4 to 8 degrees Celsius supply temperature serving the pasteuriser plate exchanger regenerator, the raw milk silo cooling, the cheese curd vat jackets, the cream and butter rooms, the yogurt chiller, the ice cream mix age vat, and the glycol distribution loop throughout the plant. Glycol is propylene glycol (food-grade) typically at 30 to 40 percent concentration in water for the food-zone loop. The chiller itself is ammonia secondary or HFC depending on the site.

The glycol plant room HVAC is straightforward — 18 to 22 degrees Celsius, 6 to 10 ACH, 304 stainless or galvanised supply duct — but the glycol piping carries condensation risk in summer and is typically insulated externally with closed-cell PIR and continuous vapour barrier.

Section 13 — Steam boiler and combustion

Dairy steam consumption is substantial — 100 plus tonnes per hour on a large integrated site — serving pasteurisation, UHT direct steam injection, CIP heating, evaporator heating and spray dryer inlet air heating. Boilers are typically natural-gas-fired with some coal or biomass at legacy sites, sized at 5 to 30 MW thermal duty per boiler with multiple boilers in a redundant configuration.

Boiler room ventilation

Boiler room mechanical ventilation 30 ACH outdoor air for combustion plus dilution. Combustion air dedicated supply duct sized at approximately 14 cubic metres per second per MW boiler capacity for Australian gas-fired plant. Boiler combustion air supply duct typically galvanised because the room ambient is dry and the duct does not see CIP or process washdown.

Flue stack

The flue stack carries combustion products at 150 to 250 degrees Celsius from the boiler exhaust outlet to atmospheric discharge. Material is refractory-lined carbon steel or high-temperature stainless above 250 degrees Celsius. Stack terminal height per AS 1668.2 dispersion modelling, typically 5 to 10 metres above the boiler room roof depending on the surrounding building heights and intake locations. CO and CO2 monitoring with alarm at 30 ppm CO and 5000 ppm CO2 in the boiler room.

Boiler inspection

Boiler design and inspection under AS 4036 and AS 4037 with state safe-work boiler inspector certification. Annual flue gas analysis and combustion efficiency report. NOx emission within state EPA limit. Heat recovery from flue economiser to feedwater pre-heat or process loop where economic.

Section 14 — CIP cleaning chemistry and station extract

The CIP cycle

Clean-in-place (CIP) cleaning is the routine sanitation cycle on direct product contact equipment and the adjacent food zone surfaces. Standard sequence:

1. Pre-rinse. Cold water at 15 to 25 degrees Celsius for 3 to 5 minutes to flush gross soil.
2. Caustic wash. Sodium hydroxide (NaOH) at 2 to 5 percent concentration at 75 to 85 degrees Celsius for 15 to 30 minutes. Caustic dissolves proteins and saponifies fats.
3. Intermediate rinse. Warm water at 45 to 55 degrees Celsius for 3 to 5 minutes.
4. Acid wash. Nitric acid (HNO3) or phosphoric acid (H3PO4) at 1 to 2 percent at 65 to 75 degrees Celsius for 10 to 20 minutes. Acid dissolves mineral scale.
5. Final rinse. Cold water to potable standard.
6. Sanitiser. Peracetic acid (PAA) at 0.05 to 0.15 percent, or sodium hypochlorite (NaOCl) at 100 to 200 ppm available chlorine, or quaternary ammonium (QUAT).

WES and engineering controls

Safe Work Australia WES for CIP chemistries: caustic NaOH (as aerosol) 2 mg/m3 ceiling, nitric acid HNO3 2 ppm TWA / 4 ppm STEL, phosphoric acid H3PO4 1 mg/m3 TWA, peracetic acid PAA 0.4 ppm STEL, chlorine Cl2 0.5 ppm STEL, ammonia NH3 25 ppm TWA / 35 ppm STEL.

Local extract over CIP chemical wash bays sized to capture caustic, acid and sanitiser vapour at 0.5 to 1.0 m/s face velocity. 316L stainless single-pass exhaust to outdoor. CIP chemical store negatively pressurised minus 5 Pa relative to plant. Eye wash and emergency shower per AS 3859. Drain points at every low spot. Discharge to outdoor at minimum 3 metres above roof and 8 metres horizontal from any intake.

Section 15 — Effluent treatment and biogas

Dairy effluent — the combined wash water, CIP rinses, whey permeate and floor washdown — is substantial. A large integrated dairy plant generates 5 to 20 megalitres per day of effluent. Treatment options range from direct discharge to municipal sewer (small operators with low strength effluent), trade waste discharge after primary treatment (most metropolitan plants), or full on-site anaerobic biological treatment with biogas recovery.

Anaerobic digestion of high-strength dairy effluent produces methane biogas which is captured and used as fuel for the steam boiler or for combined heat and power generation. The biogas plant requires AS/NZS 60079 hazardous area classification (Zone 1 or Zone 2 depending on the area), gas detection on methane (LEL alarm at 20 percent, evacuation at 50 percent), and emergency exhaust ventilation.

Effluent odour management requires local extract over treatment ponds and tanks routed via 316L stainless duct to a biofilter or chemical scrubber before atmospheric discharge. Hydrogen sulphide (H2S) is the primary odour compound and Safe Work Australia WES is 10 ppm TWA / 15 ppm STEL.

Section 16 — Why galvanised steel fails in dairy — the four failure modes

Failure mode 1 — Caustic and acid CIP chemistry

Caustic NaOH at 2 to 5 percent at 75 to 85 degrees Celsius and acid HNO3 or H3PO4 at 1 to 2 percent at 65 to 75 degrees Celsius strip the zinc coating from galvanised steel within weeks under direct splash exposure and within months under overspray exposure. The underlying carbon steel then oxidises rapidly, sheds particulate into the airstream, and presents as a non-conformance on the next food safety audit. 316L stainless tolerates both chemistries indefinitely.

Failure mode 2 — Sanitiser chloride pitting

Sodium hypochlorite sanitiser at 100 to 200 ppm available chlorine and quaternary ammonium sanitisers both carry a chloride load that aggressively attacks the zinc coating and pits the underlying carbon steel. 304 stainless tolerates the chloride load adequately for most dairy applications; 316L is the durable choice for direct product splash zones.

Failure mode 3 — Wet ammonia mist

Wet ammonia mist from leaks in the ammonia machinery room, ammonia evaporator coils in product cold rooms, and ammonia secondary in IQF tunnels destroys zinc within weeks. The ammonia reacts with the zinc to form zinc-ammonia complexes that wash off in subsequent humidity cycles. 316L stainless is the only durable answer for ammonia-adjacent ductwork.

Failure mode 4 — Milk powder dust hygroscopic loading

Milk powder, whey powder and lactose powder all attract moisture from ambient humidity (hygroscopic). Powder dust deposit on duct interiors picks up moisture, becomes a sticky paste, and forms a continuous corrosion cell against the underlying steel. Galvanised duct in a powder packing room sheds zinc within months and presents as a major non-conformance on an Asia-Pacific destination market regulator audit for infant formula export.

Section 17 — SBKJ machine configuration for Australian dairy fabrication

The fabrication problem

Australian fabricators serving the dairy sector need to produce 316L stainless ductwork to hygienic finish, with TIG-welded seams ground to Ra 0.8 micron internal, in a mix of rectangular, round and oval geometries, in spark-resistant configurations for the milk powder spray dryer and ammonia machinery room work, with full traceability of mill certs and weld procedures. Conventional galvanised duct lines configured for thin-gauge Pittsburgh-seam fabrication do not deliver this. The fabricator needs a configurable food-grade stainless line.

SBKJ SBAL-V auto duct production line — stainless food-grade configuration

SBKJ ships the SBAL-V auto duct production line in a specific configuration for 316L stainless food-grade dairy work. Headline features:

• 316L stainless coil capability. 0.5 to 1.5 mm thickness, 1250 mm or 1500 mm coil width (SBAL-V-1250J or SBAL-V-1500J). PVD-coated tool steel rollers and shear blades to prevent galvanic transfer to stainless coil.
• TIG seam welder integration. Continuous TIG welding of the longitudinal seam in 316L coil, with internal ground and polished finish to Ra 0.8 micron meeting EHEDG and FSANZ 3.2.3 hygienic surface requirements.
• Quick-change coil pay-off. Switch between 316L and 304 grades within a shift — common requirement on bespoke dairy work where the ammonia machinery room exhaust and the food-zone supply may run on the same project.
• Stainless-faced run-out tables. Prevent steel-on-stainless contamination during finished duct handling.
• Surface finish inspection. In-line surface roughness inspection station verifies Ra 0.8 micron on internal seam.
• Spark-resistant tooling option. Non-sparking working faces for the milk powder spray dryer plenum, the powder packing room dust extract and the ammonia machinery room exhaust where AS/NZS 60079 hazardous area classification applies. SBKJ supplies the tooling variant on request with documented certification.

SBKJ SB-ZF1500 stitchwelder — the critical fabrication for spray dryer plenum and infant formula clean room

The SBKJ SB-ZF1500 stitchwelder is the critical machine for fabricating the spray dryer plenum, the bag filter housing duct, the cyclone connecting ducts, the powder pneumatic conveying lines and the infant formula ISO 7 clean room supply plenum. The stitchwelder produces continuous welded seams in 316L coil at 1500 mm width and 0.8 to 2.5 mm thickness, with seam integrity rated for the reduced explosion pressure on the NFPA 68 vent panel installation and the hygienic surface finish on the clean room supply.

SBKJ SBSF-1525 flanging machine — round duct termination

The SBKJ SBSF-1525 flanging machine produces hygienic flange terminations on round 316L stainless duct sections for connection to process equipment (pasteuriser, UHT plant, spray dryer, fluidised bed) and to inline components (cyclone, bag filter, isolation valves). Flange faces machined to crevice-free standard with food-grade EPDM gasket seating.

SBKJ SBFB-1500 spiral tubeformer

The SBKJ SBFB-1500 spiral tubeformer produces 316L stainless spiral round duct in 0.5 to 1.2 mm thickness up to 1500 mm diameter. Spiral round duct is the dominant geometry for the powder pneumatic conveying lines, the bag filter clean-side discharge, the cheese maturation room recirculation duct, the ammonia machinery room exhaust riser and the spray dryer combustion air supply.

SBKJ SBPC1500 plasma cutter

The SBKJ SBPC1500 plasma cutter handles stainless cutting on the SBAL-V line and offline for component fabrication including duct fittings, branch take-offs, custom transitions and HEPA terminal frames for the infant formula clean room. Plasma cuts at 1500 mm width on 0.5 to 6 mm 316L stainless plate.

SBKJ SBLR-600 longitudinal seam welder

The SBKJ SBLR-600 longitudinal seam welder completes the welded stainless components, particularly the larger spray dryer plenum sections, the bag filter housing seams, the flue stack sections (in stainless variant) and the IQF tunnel internal recirculation ducts.

Site footprint and utilities

An SBKJ food-grade stainless dairy fabrication line including SBAL-V, SB-ZF1500 stitchwelder, SBSF-1525 flanger, SBFB-1500 spiral, SBPC1500 plasma and SBLR-600 longitudinal welder occupies approximately 40 by 12 metres factory footprint plus coil decoiler and finished-duct handling area. Utilities: 120 to 150 kW total electrical, 8 bar compressed air, argon-helium TIG shield gas supply, hydraulic oil reservoir, and local exhaust on the welding stations sized to Safe Work Australia WES for stainless welding fume (manganese, hexavalent chromium, nickel).

Fabrication standard delivered

An SBKJ dairy fabrication line in food-grade stainless configuration, run by a competent operator, delivers:

• 316L or 304 stainless steel duct in round, rectangular or oval cross-section.
• Length tolerances to plus or minus 1 millimetre per metre.
• TIG-welded longitudinal seam internally ground and polished to Ra 0.8 micron.
• Drain points at every low spot on sloped runs.
• Crevice-free flange connections with food-grade EPDM gasket.
• Accessible inspection cover at every change of direction.
• Surface finish externally No. 4 brushed or 2B mill finish per buyer preference.
• Spark-resistant tooling certified for NFPA 660 and AS/NZS 60079 hazardous area applications.
• Material mill certs and weld procedure records for DFSV, Asia-Pacific destination market regulator and FDA audit pack.

This standard passes DFSV and state dairy authority audit, FSANZ 3.2.3 and 2.9.1 compliance check, AS 1668.2 mechanical ventilation review, AS/NZS 5149 refrigeration safety inspection, NFPA 660 combustible dust hazard review, ISO 14644 clean room qualification, FDA cGMP audit for US export, and the major Asia-Pacific destination market regulator facility audit for infant formula export.

Section 18 — Installation, commissioning and post-installation verification

Construction sequence

For a typical Australian integrated dairy plant fit-out, the ductwork sequence runs: confirm slab levels and roof openings; lock process equipment positions (pasteuriser, UHT plant, separator, churn, fermenter, cheese vats, maturation rooms, spray dryer, fluidised bed, infant formula clean room, ice cream IQF tunnel, ammonia machinery room, boiler room) before drawing duct geometry; fabricate off-site on the SBKJ food-grade stainless line; install on engineered supports with anti-vibration mounts at process equipment connections; insulate the chilled, frozen and cryogenic scope; install fans and air handlers with flexible joints; commission with airflow balance, leak test, temperature and humidity verification, HEPA challenge on clean rooms, ammonia detector calibration and explosion vent installation witness; hand over with as-built drawings, commissioning report and food safety officer sign-off.

Factory Acceptance Test (FAT)

FAT on 316L food-zone duct covers dimensional inspection against drawings, visual weld inspection every linear metre, internal surface roughness Ra 0.8 micron with a portable gauge, leak test at 1.5 times design pressure with smoke detection, drainability check on all sloped runs, weld procedure record verification, and witness by the customer's food safety officer and engineering project manager.

Site Acceptance Test (SAT)

SAT post-installation verifies:

• Airflow balanced within 10 percent of design at every supply and extract terminal.
• Pressure differentials between rooms verified with calibrated micromanometer.
• Temperature and humidity stable in cheese maturation, infant formula clean room, yogurt fermenter, ice cream IQF tunnel and ammonia machinery room over a 48 to 72 hour mapping run with 12 to 30 calibrated data loggers per ISO 14644 and ASHRAE 153 protocol.
• HEPA integrity test on infant formula clean room and aseptic filler supply per IEST-RP-CC034 PAO challenge.
• Surface swab on hygienic duct interiors before first product run.
• Ammonia detection calibration witnessed by safe-work inspector.
• Explosion vent panel installation witnessed by fire engineer.
• Fire damper drop-test witnessed under AS 1851.

Documentation pack

The handover pack typically includes: as-built mechanical drawings; IQ, OQ, PQ reports; mill certs for every section of 316L stainless duct; weld procedure records and weld inspection reports; FAT reports; SAT reports; leak test reports; thermal mapping reports for cheese maturation, clean rooms, IQF tunnels and ammonia machinery room; HEPA challenge certificates; ammonia detector calibration certificates; explosion vent panel certificates and NFPA 68 sizing calculations; fire damper certificates; fire engineer sign-off; food safety officer sign-off; DFSV or state dairy authority licence application pack; Asia-Pacific destination market registration pack (for Asia-Pacific infant formula export); FDA cGMP audit pack (for US export); operator manuals; CIP procedure documents.

Ongoing inspection and re-validation

Annual schedule: HEPA integrity re-test on infant formula and aseptic filler supply; thermal re-mapping on cheese maturation, clean rooms, IQF tunnels and ammonia machinery room; ammonia detector calibration; fire damper drop-test under AS 1851; explosion vent panel inspection; surface swab on hygienic duct interiors; CIP cycle audit; destination-market export-channel regulator audit (Asia-Pacific, FDA, EU) at the regulator's schedule. Documentation retained for the life of the plant.

Section 19 — Worked example: a Victorian infant formula export plant

An Australian infant formula manufacturer plans a new 30,000 tonne per year production facility in northern Victoria for export to Asia-Pacific destination markets. The site combines a milk powder spray dryer, fluidised bed dryer, powder blending and infant formula filling line, retail tin and pouch packaging, and a complete CIP and effluent system. The customer is targeting major Asia-Pacific destination market registration for the regional infant formula export channel, FDA cGMP for US export, and FSANZ Standard 2.9.1 compliance for domestic and ANZ retail.

The HVAC ductwork scope splits into 11 sub-systems:

1. Raw milk receival and silo room. 304 stainless supply and 316L stainless extract, ammonia secondary cooling on silos. Approximately 50 linear metres.
2. Pasteurisation hall. 304 stainless supply and 316L stainless extract over pasteuriser. Approximately 30 linear metres.
3. Evaporation and concentration. 316L stainless throughout for the multi-effect evaporator vapour and condensate ductwork. Approximately 40 linear metres.
4. Milk powder spray dryer. 316L stainless with NFPA 68 explosion vent panels on the chamber, NFPA 69 isolation valves on the connecting ducts to cyclone and bag filter, spark detection at the dryer outlet duct with water spray, AS/NZS 60079.14 earthing and bonding throughout. Approximately 80 linear metres of process ductwork plus 25 linear metres of explosion vent ducting.
5. Fluidised bed dryer. 316L stainless throughout with same NFPA 660 controls. Approximately 30 linear metres.
6. Powder packing room. 316L stainless dust extract on each filling line, routed to a dedicated bag filter with NFPA 68 vent panel. ISO 14644 Class 7 supply (HEPA H13) and pressure cascade plus 10 Pa to adjacent process. Approximately 80 linear metres.
7. Infant formula blending and filling clean room. ISO 14644 Class 7 with HEPA H13 supply, 316L stainless throughout, pressure cascade plus 15 Pa to adjacent process, 8 ACH continuous. Approximately 120 linear metres.
8. Retail tin and pouch packaging. 304 stainless ambient with HEPA H13 on the dosing and seal stations. Approximately 60 linear metres.
9. Ammonia machinery room. 316L stainless single-pass exhaust, 30 ACH emergency capacity, ammonia detection at 25 / 150 / 250 ppm thresholds, N+1 fan redundancy. Approximately 40 linear metres.
10. CIP chemical station and store. 316L stainless local extract over wash bays, 316L stainless single-pass exhaust to outdoor. Approximately 30 linear metres.
11. Steam boiler room. Galvanised combustion air supply, refractory-lined stainless flue stack. Approximately 35 linear metres plus 12 metres of stack.

Total ductwork approximately 632 linear metres, with 316L stainless representing over 80 percent of the scope. All 316L sub-systems fabricated on an SBKJ SBAL-V stainless food-grade line with TIG seam welding and internal grinding to Ra 0.8 micron. Stitchwelded plenums fabricated on SBKJ SB-ZF1500. Round duct fabricated on SBKJ SBFB-1500 spiral. Plasma cutting on SBKJ SBPC1500. Spark-resistant tooling applied for the spray dryer plenum, powder packing duct, fluidised bed and ammonia machinery room exhaust.

The handover compliance pack covers AS 1668.2, AS 4254, AS/NZS 5149, AS 3957, AS 1530.4, AS 1851, AS 4036, AS 4037, AS 1940, AS/NZS 60079, NFPA 660, NFPA 68, NFPA 69, FSANZ 1.2.1, 3.2.2, 3.2.3 and 2.9.1, ISO 22000, HACCP, Codex STAN 72, Codex STAN 156, ISO 14644 Class 7 clean room qualification, Dairy Food Safety Victoria licence application, Asia-Pacific destination market regulator registration audit pack (for Asia-Pacific export), FDA cGMP audit pack (for US export), FAT and SAT reports, as-built drawings, weld procedure records and operator manuals. For a project of this scale, the fabricated ductwork represents one of the largest single fit-out line items, second only to the spray dryer and the refrigeration plant.

Section 20 — Closing — the SBKJ engineering position

The Australian dairy sector is one of the most engineering-intensive food manufacturing categories anywhere in the world. The combination of FSANZ regulation, state dairy authority licensing, AS/NZS refrigeration safety, AS 3957 combustible dust, AS 1668.2 mechanical ventilation, ISO 14644 clean room classification, and the destination-market export-channel regulator scrutiny from Asia-Pacific destination market regulators, FDA and EU drives a multi-tier specification that touches every single zone in the plant. The HVAC ductwork is the connective tissue across every one of those zones and the only material that survives the combined CIP, refrigerant, dust and humidity load on a sustained basis is 316L stainless steel, fabricated to hygienic finish, installed on engineered supports with vapour barriers and drain points, and verified at FAT, SAT and on the annual audit cycle.

SBKJ Group, headquartered in Box Hill North, Victoria, ships HVAC duct fabrication machinery — the SBAL-V auto duct production line in stainless food-grade configuration, the SB-ZF1500 stitchwelder, the SBSF-1525 flanger, the SBFB-1500 spiral tubeformer, the SBPC1500 plasma cutter and the SBLR-600 longitudinal welder — to Australian and regional fabricators serving this market. Spark-resistant tooling is available for the milk powder spray dryer plenum and ammonia machinery room work. Our Box Hill North engineering team supports specification, commissioning, training and ongoing service. Our customers fabricate the ductwork that ends up in the dairy plants that supply Australian consumers and the export channels that take Australian dairy into Asia-Pacific, the Middle East, North America and Europe.

The Australian dairy industry — led by Saputo, Bega Cheese, Fonterra Australia, Bulla, Pauls Pure Goodness (Lactalis), Norco, Burra Foods, Bellamy's, a2 Milk, Bubs Australia, Chobani, Streets, Peters, Maggie Beer Ice Cream and the broad cheese specialist segment from Tarago River to King Island Dairy — runs to an HVAC ductwork standard that few other food manufacturing categories match. SBKJ supplies the machinery that fabricators use to deliver to that standard.

If you are planning a new dairy plant, expanding an existing line into infant formula or aseptic UHT, replacing galvanised duct that has reached the end of its CIP service life, or upgrading a spray dryer to current NFPA 660 controls, the right conversation starts with the process map, the code stack and the export-channel regulator scope. Send us your process flow diagram, your facility floor plan and your export market list, and one of our engineers will walk through the zone-by-zone material selection, fabrication scope and machinery configuration with you. We reply within 12 hours from Box Hill North.

Get an SBKJ engineering review of your dairy plant HVAC duct scope →

FAQ

Why is 316L stainless steel mandatory for dairy processing ductwork?

Dairy plants combine four corrosive loads: caustic CIP NaOH at 2 to 5 percent at 75 to 85 degrees Celsius, acid CIP nitric or phosphoric at 1 to 2 percent, sanitiser sprays with peracetic acid and sodium hypochlorite, and ammonia refrigeration mist. Galvanised fails within months under any one and within weeks under combined exposure. 316L with 2 to 3 percent molybdenum is the only durable answer for direct food contact, product splash, CIP-served and refrigeration-adjacent ductwork. SBKJ engineering practice is 316L throughout the wet, refrigeration and infant formula clean room scope, 304 in ambient packaging halls and AS 4254 G90 galvanised in dry warehouse and office HVAC.

What is the explosion vent and dust extract specification for a milk powder spray dryer?

Skim milk powder, whole milk powder, whey powder and infant formula base powder have Kst values 100 to 170 bar.metre per second placing them in St 1 to St 2 explosibility under AS 3957 and NFPA 660. NFPA 68 explosion venting sizes vent panels on chamber and bag filter, NFPA 69 explosion prevention applies inerting or suppression, spark detection at dryer outlet with water spray within 30 milliseconds, isolation valves to prevent flame propagation, AS/NZS 60079.14 earthing and bonding to less than 1 megohm at every joint. Duct material 316L stainless throughout.

What HVAC clean room class is required for infant formula manufacturing in Australia?

FSANZ Standard 2.9.1 plus Codex STAN 72 plus Cronobacter sakazakii prevention drives ISO 14644 Class 7 (Grade C equivalent) for powder blending, dosing and filling. HEPA H13 supply, 6 to 10 ACH, plus 10 to plus 15 Pa positive pressure, 18 to 22 degrees Celsius, 35 to 50 percent RH, 316L stainless TIG-welded Ra 0.8 micron internal. Australian export operators (Bellamy's, a2 Milk, Bubs Australia, Burra Foods, Camperdown Dairy, Beston Global) typically run tighter than minimum because of major Asia-Pacific destination-market regulator, FDA and TGA scrutiny.

What temperature and humidity is required for a cheese maturation room?

10 to 15 degrees Celsius and 80 to 90 percent RH held for 30 to 50 days for Camembert and Brie soft cheese, 6 to 24 months for Cheddar and Gouda, 12 to 36 months for Parmesan and Grana. Single-pass exhaust on mould-ripened varieties (Penicillium roqueforti blue, Penicillium camemberti white) to contain mould aerosol. HEPA H13 supply to exclude wild moulds. 316L stainless duct throughout. Air movement 0.1 to 0.3 m/s at cheese surface. Parmesan final dry-down phase at 50 to 65 percent RH.

How does an ammonia refrigeration machinery room HVAC specification work?

AS/NZS 5149 Class T2: continuous 0.014 cubic metres per second per square metre floor area, emergency 30 ACH on 25 ppm ammonia trip, alarm thresholds 25 / 150 / 250 ppm, 316L stainless single-pass exhaust to outdoor, discharge 3 m above roof and 8 m horizontal from any intake, 15 m from pedestrian path, N+1 fan redundancy, UPS-backed control, manual emergency stop at every exit. Saputo Allansford and Cobram, Bega Tatura, Fonterra Stanhope, Bulla Colac, Pauls Crestmead all comply.

How is H2O2 hydrogen peroxide handled in a UHT aseptic packaging line?

TetraPak, Sidel, KHS and SIG Combibloc fillers use 30 to 35 percent H2O2 plus heat for carton sterilisation. WES 1 ppm STEL. Local extract at filler discharge 0.5 to 1.0 m/s face velocity, 316L stainless single-pass to catalytic decomposer or activated carbon scrubber, no recirculation. Aseptic packaging hall ISO 14644 Class 7 with HEPA H13, plus 5 to plus 10 Pa positive, 18 to 22 degrees Celsius, 35 to 50 percent RH. Discharge to outdoor at 3 m above roof and 8 m from intake.

What is the difference between AS/NZS 1677 and AS/NZS 5149?

AS/NZS 1677 is the historical Australia-NZ refrigeration safety standard now largely superseded by AS/NZS 5149 series (adopting ISO 5149 with Australasian variations). AS/NZS 5149.1 definitions and classifications, .2 design construction and testing, .3 installation site, .4 operation maintenance and recovery. For HVAC duct in an ammonia machinery room both drive: refrigerant classification, room classification (Class T1/T2/T3), mechanical ventilation rate, exhaust duct material (316L stainless single-pass), ammonia detection thresholds and shutdown logic. Plants designed since 2016 use AS/NZS 5149.

What CIP cleaning chemistry does dairy ductwork have to tolerate?

Pre-rinse cold water, caustic NaOH 2 to 5 percent at 75 to 85 degrees Celsius, warm intermediate rinse, acid HNO3 or H3PO4 1 to 2 percent at 65 to 75 degrees Celsius, cold final rinse, sanitiser peracetic acid 0.05 to 0.15 percent or sodium hypochlorite 100 to 200 ppm or QUAT. WES peracetic 0.4 STEL, chlorine 0.5 STEL, ammonia 25 TWA / 35 STEL. 316L stainless throughout. Local extract over wash bays 0.5 to 1.0 m/s, single-pass to outdoor.

Why does milk powder spray dryer ductwork require explosion venting and spark detection?

Skim milk powder Kst 100 to 130, whey 120 to 150, infant formula base 130 to 170, all St 1 to St 2 under AS 3957 and NFPA 660. Pmax 7 to 9 bar. Pressures rise to 7 to 10 bar in milliseconds during deflagration. NFPA 660 dust hazard analysis on every enclosed volume, NFPA 68 explosion venting on chamber and bag filter, NFPA 69 inerting and suppression where venting impractical, spark detection at dryer outlet with water spray within 30 ms, isolation valves to prevent flame propagation, AS/NZS 60079.14 earthing and bonding below 1 megohm at every joint. 316L stainless throughout rated for reduced explosion pressure.