Why textile HVAC ductwork is its own engineering discipline
Textile manufacturing is one of the most diverse single industries an HVAC engineer will ever specify ductwork for. A single integrated mill can run a wool-scouring line at 90 degrees Celsius and saturated humidity beside a carding hall full of fine wool dust, a weaving floor at 90 dB(A) with cotton lint suspended in the air, a dyeing house at 80 degrees Celsius with acid and azo-dye chemistry, a tenter-frame finishing line at 180 degrees Celsius, a coating and lamination booth full of VOC, and a garment-assembly hall with 200 sewing operators who need design-office air quality. Every one of those zones is a different duct material, a different velocity, a different fire-protection regime, and a different noise criterion. Trying to specify the whole plant with one ductwork specification is how a six-figure ventilation budget gets blown twice over.
The Australian context adds a few specific challenges. The Australian wool clip is the world's largest fine-wool source and the scouring and carding stages happen domestically before the bulk of the spinning, weaving and knitting moves offshore. Cotton from the Murray-Darling and Namoi valleys is ginned, baled and warehoused in Australia. Hot, dry summers and cool, damp winters mean the same plant has to handle both ends of the humidity range without dewpoint excursions in the supply duct. And the Australian regulatory regime — AS 1668.2 for industrial ventilation, AS 4024 for machinery safety, AS/NZS 60079 for hazardous areas, and the local cross-references to NFPA 484 combustible dust and NFPA 33 spray finishing — sets the floor that every ductwork specification has to clear.
This guide walks through the full process flow from raw fibre to finished garment, calls out the specific duct, fan and material decisions for each stage, summarises the standards that apply, and ends with the SBKJ machine configuration we recommend for fabricators serving the Australian textile, clothing, fashion and outdoor-apparel sector. It is the reference our engineers use when an Australian mill, fashion house or technical-textile fabricator calls us for a duct-machinery specification.
Standards that frame the specification
Before any process detail, it is worth getting the standards stack clear in one place. Every textile ductwork specification we write in Australia traces back to the following documents, and a fabricator who cannot evidence compliance with each is not building duct for a serious mill.
- AS 1668.2 — The use of ventilation and air conditioning in buildings, Part 2 — Mechanical ventilation in buildings. Sets minimum outdoor-air rates, contaminant exhaust requirements and general industrial ventilation design rules. Every textile process zone has a minimum outdoor-air rate that traces back to AS 1668.2, and the duct sizing flows from that rate plus the local contaminant load.
- AS 4024 — Safety of machinery. Covers guarding, interlocks and lock-out for machinery, including ducted exhaust on processes like tenter frames, calenders and coating lines where the duct is integrated into the machine envelope. AS 4024 is what stops a maintenance operator from opening an inspection hatch on a live duct.
- AS/NZS 60079 — Explosive atmospheres. Classifies zones where flammable gas, vapour or dust may be present. Dyeing chemistry vapour, solvent-spotting cabinets, coating booths and certain lamination lines all fall under AS/NZS 60079 zone classification, and any electrical or mechanical device inside the zone — fans, dampers, sensors, lights — has to be rated for the zone and the equipment temperature class.
- NFPA 484 — Standard for Combustible Metals. Despite the name, the wider NFPA 484 framework and its companion NFPA 654 are the international reference for combustible particulate solids including cotton lint, wool dust and synthetic-fibre dust. Kst, Pmax, MIE and dust-cloud ignition data drive duct geometry, isolation, deflagration venting and explosion-protected fan selection.
- NFPA 33 — Standard for Spray Application Using Flammable or Combustible Materials. Applies to coating booths, lamination lines and any process where finishing chemistry is sprayed onto fabric. NFPA 33 drives booth design, exhaust velocity, VOC capture and the fire-suppression interface between duct, booth and stack.
- ISO 9000 series — Quality management systems. A textile mill running to ISO 9001:2015 has to document its environmental control regime including supply-air filtration, room pressure differentials and contaminant capture. The ductwork specification is part of the QMS evidence pack, not a separate document.
Every zone in the rest of this guide is tagged with the specific standards that apply, the duct material that follows from those standards, and the fabrication implication for the duct-line operator.
Stage 1 — Wool clip processing: scouring, carding, combing, spinning
The Australian wool clip is shorn on-farm, baled, and trucked to a wool store for sale. From there it moves to a scouring plant, then a carding line, then combing and spinning. Every stage has its own ventilation signature and its own duct material implication.
Wool stores and bale handling
A wool store is a large warehouse-style building full of wool bales waiting for sale or shipment. The air-quality risks are wool dust suspended by bale movement, residual sheep lanolin and grease, and any agricultural contamination on the fleece. The HVAC design is low-velocity dilution ventilation, NC-55 acoustic, and 6-8 air changes per hour. Duct is galvanized G350 spiral or rectangular. Reference Australian wool stores include Botany Bay Wool Stores in New South Wales and the historic Yennora wool selling complex in western Sydney.
Wool scouring
Scouring is the wet-cleaning stage where greasy wool is washed through a sequence of hot-water bowls dosed with detergent and alkali to remove lanolin, suint and farm dirt. The scouring bowl runs at 50-65 degrees Celsius and the airspace above it is saturated with water vapour, detergent aerosol and trace ammonia. The duct over a scouring line is 316L stainless steel with welded longitudinal seams, sloped at 1:100 to a condensate drain that ties to the wool-grease recovery system. Reference Australian scouring operations include Michell Wool at Salisbury in South Australia (one of the largest wool processors in Australia and one of the longest continuous operators in the global wool industry), GWS Group in Geelong, and the wider Australian Wool Network and Australian Wool Innovation supply base. Wool International is another reference operator in the broader Australian-owned processing space.
Wool drying
After scouring, scoured wool is dried in a multi-stage drier at 60-90 degrees Celsius. Duct on the dryer is 316L stainless steel with high-temperature insulation. A dedicated air-to-air heat exchanger on the dryer stack is the single largest energy-recovery opportunity on a wool-processing line, and the supply-side of the exchanger is fed back into the scouring bowl and pre-warm circuit.
Carding
Carding straightens and aligns the dried wool fibres into a continuous web. The carding hall is the dustiest part of a wool mill. Fine wool dust, vegetable matter and short broken fibres are released into the room air, captured at hooded inlets above each card, and ducted to a dust collector. Duct material is galvanized G350 spiral with bonded and grounded joints under NFPA 484. Hood capture velocity is 1.0-1.5 m/s at the face, transport velocity in the main is 18-22 m/s to keep wool dust suspended without bridging. Deflagration venting on the dust collector and isolation valves on the trunk are mandatory.
Combing
Combing removes short fibres and parallelises the long fibres for worsted spinning. Dust loading is lower than carding because the wool is already cleaned and the short fibres are extracted to a separate by-product line. Duct is still galvanized G350 spiral but transport velocity drops to 16-18 m/s and the dust load on the collector is roughly a third of the carding load.
Spinning
Spinning twists the combed sliver into yarn on a ring or open-end spinning frame. The spinning hall is humidity-controlled to 60-65% RH because dry wool generates static and breaks. Supply duct is insulated galvanized G350 with a high-efficiency particulate filter on the supply side, and there is a low-velocity exhaust on the floor to clear short fibres and lint that drop from the spindles. Acoustic target is NC-55 because spinning frames are noisy but not as loud as weaving looms.
Stage 2 — Cotton processing: ginning, baling, lint capture
Australian cotton is grown in the Namoi, Gwydir, Macquarie and Murray-Darling valleys and ginned at regional gin sites before being baled and trucked to port. The reference industry bodies and operators are Cotton Australia (the industry peak body), Namoi Cotton (the publicly listed processor and marketer trading on the ASX), the historic Auscott operation at Goondiwindi (which was divested in 2023), and a wide network of grower-owned and grower-cooperative gins including operations around Walgett.
Ginning
A cotton gin separates the lint from the seed and from the trash (sticks, leaves, stones, soil). The gin stand and lint cleaner is the dustiest single point in the entire cotton supply chain. Duct material is galvanized G350 spiral, sized for a transport velocity of 20-24 m/s in lint-return lines and 16-20 m/s in trash-return lines. NFPA 484 combustible-dust classification is mandatory because cotton lint has one of the highest dust-cloud ignition sensitivities in any agricultural fibre. Deflagration venting is sized to KSt and rupture-disc pressure of the dust collector. Spark detection and extinguishing systems are integrated into the trunk before the cyclone or baghouse.
Baling
After ginning, lint is compressed into universal density bales (about 227 kg each) and wrapped for transport. The baling room has a lower dust load than the gin stand but is still a NFPA 484 zone. Duct serves the bale press and the warehouse air-handling. Galvanized G350 spiral with bonded joints, deflagration venting on any branch over 6 m.
Cottonseed handling
Cottonseed is a high-value by-product. Seed handling generates trash dust and seed-hull fines. Duct on the seed line is galvanized G350 spiral with the same NFPA 484 protections. The seed line is often on the same dust collector as the trash-return line from the gin stand.
Stage 3 — Fabric weaving and knitting
Fabric formation splits into weaving (which interlaces warp and weft yarns) and knitting (which loops a single yarn into a fabric). Both stages have ventilation requirements that look superficially similar but differ in the detail.
Weaving
A modern shuttleless weaving floor — air-jet, rapier or projectile — runs at 85-95 dB(A) machine noise across hundreds of looms. The HVAC target is humidity control at 65-75% RH (high humidity keeps the warp yarns flexible and reduces breakage), supply-air filtration to remove ambient dust and finish residue, and continuous lint extraction at floor level. Supply duct is insulated galvanized G350 rectangular running overhead with low-velocity drum diffusers. Lint-extraction duct is galvanized G350 spiral with no-flat-bottom hoppers under the trunk. Transport velocity 18-22 m/s. Noise criterion in the weaving hall itself is NC-65 because anything quieter is masked by the looms; the duct is sized for the air change and lint capture, not the acoustic.
Australian reference operations in fabric weaving and textile manufacturing include the historic Sheridan Textiles Australian manufacturing (since closed; Sheridan now operates as a design-and-import brand under Hanesbrands), Bambi (the long-running luxury blanket manufacturer), MacGregor's in New South Wales, the wider Australian Country Spinners operation that supplies the Spotlight retail group, and Bonds (now part of Hanesbrands with design retained in Australia but bulk manufacture offshore).
Knitting
Knitting halls are quieter (75-85 dB(A) typical) and generate less lint than weaving because the yarn is not subject to the same warp-weft abrasion. HVAC duct is galvanized G350 rectangular for supply with insulated wrap to control sweating in a humid-controlled hall, and galvanized G350 spiral for lint return. Transport velocity 16-20 m/s. Noise criterion NC-60.
Warping, sizing and beam preparation
Upstream of the weaving floor, warping creels and sizing machines apply a starch or PVA film to the warp yarns to reduce breakage during weaving. Sizing machines run at 80-100 degrees Celsius and exhaust steam, starch aerosol and trace solvent. Duct on the sizing exhaust is 316L stainless steel with a condensate drain.
Stage 4 — Dyeing house: chemistry, humidity, corrosion
The dyeing house is where most ductwork specifications break down on the first project. The combination of 60-80% relative humidity, hot acid, alkali, azo-dye and salt chemistry in the exhaust air, and continuous operation at 70-90 degrees Celsius means galvanized steel rusts through the zinc layer in 18-36 months. The duct contaminates the dyebath with iron oxide particles, the dyebath fails the colour-fastness specification, and the operator blames the dye supplier for six months before someone climbs up to the duct and finds the rust.
Atmospheric loading
A typical dyeing house operates at 60-80% RH because high humidity reduces yarn breakage during dyeing and stops the dyebath from concentrating through evaporation. The exhaust air carries water vapour, fine droplet aerosol, dissolved chemistry, and reactive vapours from acid, alkali, azo-dye, salt, levelling agent and pH adjuster. Specific dye chemistries (reactive dyes for cotton, acid dyes for wool, disperse dyes for polyester) each have their own vapour signature but the duct specification has to handle the worst-case combination.
Duct material
The reference duct specification for a modern dyeing house is 316L stainless steel for general exhaust with welded longitudinal seams, FRP (fibreglass-reinforced polyester) for sulfuric-acid exhaust and azo-dye exhaust, and polypropylene-lined steel for caustic alkali exhaust. The change-over points are documented on the drawing and the duct fabricator marks the material on the outside of every section so the installer cannot mix them up. Flange and gasket selection follows the same logic: 316L bolting and EPDM gasket for general exhaust, 316L bolting and PTFE gasket for FRP and polypropylene sections.
Slope, drainage and condensate
Every exhaust duct in a dyeing house is sloped at 1:100 minimum back to a condensate sump that ties to the dyehouse effluent treatment plant. Condensate is acidic and salt-laden and is not allowed into the storm system. The sump has a level alarm wired to the BMS and a pump-out cycle every shift.
Fans
Exhaust fans on a dyeing house are FRP or 316L stainless-steel direct-drive centrifugal with sealed bearings. Carbon-steel fans last 12-24 months in this service and the dye operator pays for replacement plus the lost production during the change-out.
Reference operators
Most large-scale dyeing operations in Australia have moved to commission dyeing through specialist trade houses rather than running their own integrated dye plants. The remaining Australian dyeing capacity is concentrated in wool top-makers and specialty technical-textile finishers, with the bulk of garment-stage dyeing taking place offshore for brands like Country Road, Aje, Camilla, Zimmermann, Sass & Bide and the wider Premier Investments and Just Group portfolio.
Stage 5 — Finishing: tenter frames, calenders, heat recovery
After dyeing, fabric is washed, dried, set to width and finished on a tenter frame (sometimes called a stenter). The tenter frame is the single largest energy load in a textile plant and the duct specification has to handle 150-180 degrees Celsius, condensable oils, plasticisers and finishing chemistry.
Tenter frame
A tenter frame is a long horizontal oven through which fabric passes on pin chains. Hot air is recirculated through burner boxes and a portion is exhausted continuously to control humidity and remove finishing volatiles. Exhaust duct is 316L stainless steel with welded longitudinal seams, R-1.0 insulation on the supply side, and slope to a condensate sump. Operating temperature is 150-180 degrees Celsius for most fabrics and up to 210 degrees Celsius for some technical textiles. The condensate is an oily, plasticiser-rich liquor that ties to the trade-waste system through a coalescing oil separator.
Heat recovery
An air-to-air plate or rotary heat exchanger on the tenter exhaust is the single biggest energy-recovery opportunity in a textile mill. The exchanger is sized for the worst-case dirty side (assume 180 degrees Celsius and full condensate load) and protected with a wash-down cycle on the dirty side that ties to the plant cleaning schedule. The clean side feeds the burner box pre-warm and the dyeing-house ventilation supply.
Calenders
Calenders pass fabric between heated rollers to set the surface finish, gloss or hand. The calender is sensible-heavy and runs at 100-160 degrees Celsius. Exhaust duct is 316L stainless steel with insulation. Calender exhaust is often combined into the tenter exhaust trunk upstream of the heat exchanger.
Stage 6 — Coating, lamination and technical textiles
Coating and lamination apply a polymer film (PU, PVC, silicone, acrylic, fluorocarbon) to a base fabric to create technical textiles for outdoor apparel, automotive interiors, medical fabrics, geotextiles and protective clothing. The HVAC specification is the most complex in the textile industry because it combines NFPA 33 spray-finishing classification, AS/NZS 60079 hazardous-area classification, VOC capture and high-temperature curing exhaust.
Booth and exhaust
A coating booth is enclosed, mechanically exhausted, and rated to NFPA 33. Exhaust velocity at the booth face is 0.5-1.0 m/s with a hooded back-extract that captures solvent vapour at the application point. Duct from the booth to the stack is 316L stainless steel with welded seams. Velocity in the trunk is 12-18 m/s to keep solvent vapour homogenous and avoid stratification.
VOC capture
Booth exhaust feeds either an activated-carbon adsorber for low-volume operations or a regenerative thermal oxidiser (RTO) for higher-volume coating lines. The RTO inlet duct is 316L stainless steel insulated to limit heat loss. The RTO outlet stack is unlined carbon steel because the gas is hot, dry and post-combustion.
Hazardous-area zone
Inside the booth and within 1 m of any face the zone is classified per AS/NZS 60079. Every electrical device — fan motor, sensor, light, damper actuator — is rated to the zone and equipment temperature class. The fan is direct-drive with an explosion-protected motor (Ex d IIB T4 minimum for most solvent-based coatings).
Curing oven
After coating, fabric passes through a curing oven at 120-180 degrees Celsius to set the polymer film. The oven exhaust duct is 316L stainless steel with insulation and slope to a condensate drain. Curing oven exhaust often feeds the same RTO as the booth exhaust.
Australian technical-textile reference
Australian technical-textile operations cluster around outdoor apparel, automotive interiors and protective clothing. Macpac (originally a New Zealand brand, now in the Super Retail Group portfolio with Australian operations), Kathmandu (another Super Retail Group brand with a strong Australian presence), Mountain Designs (now part of the Anaconda Group), and the broader Anaconda outdoor-retail business (under the Spotlight Group) are the major customer-facing brands. Their high-performance shell fabrics, insulation linings and weatherproof membranes are coated and laminated through a global supply chain with a small but growing Australian technical-textile finishing capacity.
Stage 7 — Garment assembly: cut, sew, press, pack
Garment assembly is the people-intensive end of the textile industry. A modern cut-and-sew floor has hundreds of operators on automatic and semi-automatic sewing machines, with cutting tables, fusing presses, finishing presses and packing stations adjacent. The HVAC profile is internal-gain heavy (200 operators at 100 W each is 20 kW of body heat alone), low contaminant, with a continuous floor-level lint extraction.
Cutting
The cutting room handles bolts of fabric on long tables, often with automatic CNC cutters that generate fine fabric dust and short fibres. Duct on the cutter is galvanized G350 spiral with a dedicated dust collector. Transport velocity 18-20 m/s. NFPA 484 classification depends on the fabric composition: pure cotton or wool is dust-class, polyester is not.
Sewing
The sewing floor is ambient temperature, 50-60% RH, with overhead supply and floor-level exhaust to clear thread lint and short fibres. Supply duct is insulated galvanized G350 with low-velocity drum or linear diffusers. Acoustic criterion NC-50.
Fusing and pressing
Fusing presses apply heat and pressure to bond an interlining to the shell fabric. Pressing stations use steam to set seams and shape garments. Exhaust on the press is galvanized G350 with insulation and a condensate drain. Steam loading is locally high but contained to the press hood.
Spotting and stain removal
Garment-finishing spotting cabinets use solvent (perchloroethylene, mineral spirits or specialist proprietary blends) to remove production stains. The spotting cabinet is enclosed and exhausted under AS/NZS 60079 hazardous-area classification. Duct is 316L stainless steel with welded seams to the booth and a dedicated activated-carbon adsorber on the outlet.
Packing
The packing room is ambient and clean. Duct is galvanized G350 rectangular for supply, with extraction local to any tagging-gun or label-printer station. Acoustic criterion NC-45.
Stage 8 — Australian fashion brands and the small-batch reality
The bulk of Australian fashion brand manufacturing has moved offshore over the last two decades, but design, sample-making, small-batch couture and adjacent garment-trade activity remain a significant onshore industry. The HVAC ductwork specification for a design studio, a sample room or a couture workroom is different from a mass-production floor and is worth calling out separately.
Country Road and the David Jones group
Country Road operates as one of the flagship apparel brands within the David Jones group (under Woolworths Holdings of South Africa). The design, merchandising and sample-making functions are concentrated in Australia. The HVAC criterion for a design studio is NC-40 acoustic, 50% RH, and supply-air filtration to remove ambient dust that would soil sample fabrics. Duct is insulated galvanized G350 rectangular with low-velocity diffusers.
Aje, Camilla, Zimmermann, Sass & Bide
Australia's premium fashion houses — Aje, Camilla, Zimmermann and Sass & Bide — operate design and sample-room functions in Australia with bulk production offshore. Zimmermann also operates a premium swimwear and resort-wear category that overlaps with the swimwear section below. The HVAC criterion for a sample room is NC-40 acoustic, 50% RH, low-velocity supply, and dedicated extraction over any cutting or fusing station.
Bonds and Hanesbrands
Bonds is one of the most recognisable Australian apparel brands and is now part of the Hanesbrands portfolio with design retained in Australia and bulk manufacturing offshore. The Australian operations focus on design, marketing, distribution and sample-making.
Cotton On Group
The Cotton On Group, headquartered in Geelong, is the largest Australian-owned apparel retailer with a global footprint. Design, merchandising, distribution and a substantial supply-chain function operate from Australia, with manufacturing through a global supplier base.
The Iconic
The Iconic operates as Australia's dominant pure-play online fashion retailer with a large distribution centre and customer-experience operation in New South Wales. The HVAC criterion for the distribution centre is industrial warehouse — 4-6 air changes per hour, galvanized G350 spiral or rectangular, NC-55 acoustic.
Premier Investments and the Just Group
Premier Investments owns the Just Group portfolio — Jay Jays, Just Jeans, Portmans, Dotti, Smiggle and Peter Alexander — operating across Australia, New Zealand and selected international markets. The Australian operation is design, merchandising, sample-making and distribution. The HVAC criterion for a multi-brand head-office facility is mixed-use commercial with dedicated sample-room extraction.
Lorna Jane and the Australian activewear sector
Lorna Jane, owned by the McGoogan family, is the largest Australian-owned activewear brand. Lululemon Australia operates 50+ stores in Australia as the local arm of the Canadian parent. The Australian activewear sector is design and retail heavy with manufacturing offshore.
The wider designer portfolio
Sportscraft, Anthea Crawford, Reset Studio, Witchery, Mimco and Country Road operate as design and retail brands with sample-making in Australia and production offshore. The HVAC criterion for a multi-brand creative and sample-making facility is the same NC-40 design-studio specification with dedicated extraction over the sample-room cutting and pressing stations.
Stage 9 — Swimwear, leisurewear and resort apparel
Swimwear is a small but technically interesting category because the elastic-rich fabric and the precision pattern-cutting drive higher cleanroom standards than the rest of the fashion industry. Reference Australian operators include Speedo Australia (the local arm of the global Speedo brand), Seafolly Australia (a leading premium swimwear house), Tigerlily (a long-running Australian bohemian swimwear and resort-wear brand), and the premium swimwear range under Zimmermann.
The HVAC specification for a swimwear sample room is closer to a medical-device cleanroom than a general garment-assembly floor. Air is filtered to F8/F9 supply efficiency, room pressure is positive to adjacent corridors, humidity is held at 50% RH to avoid static on the elastic fabrics, and the acoustic target is NC-40. Duct is insulated galvanized G350 rectangular with low-velocity drum diffusers. Floor-level extraction captures cutting fines and short-elastic fragments.
Stage 10 — Footwear and leather
Australian footwear and leather operations are concentrated in a small number of long-established makers but they remain a meaningful onshore manufacturing presence. The HVAC specification for footwear and leather work is different from textile garment assembly because of the adhesive solvent, the leather-finishing chemistry and the lasting-room heat load.
Blundstone
Blundstone has operated from Hobart in Tasmania since 1870 and is one of the longest-running continuous footwear manufacturers in the southern hemisphere. The Blundstone elastic-sided boot is sold in 100+ countries and remains a significant Australian export. Footwear assembly involves leather cutting, stitching, lasting (forming the upper around the last) and bonding the sole to the upper. The bonding step uses solvent-based adhesives and the HVAC specification falls under NFPA 33 and AS/NZS 60079.
R.M. Williams
R.M. Williams is headquartered in Adelaide, South Australia, and operates as one of the most recognisable Australian footwear and apparel brands. R.M. Williams is currently owned by Tattarang, the private investment company of the Andrew Forrest family. The Adelaide manufacturing operation produces the iconic one-piece leather boot through a sequence of hand and machine stations that includes leather selection, cutting, stitching, lasting and finishing.
Leather tanneries and finishers
Australian leather operations include Packer Leather in Brisbane (a long-running tannery serving footwear, equestrian and saddlery markets) and Howe Leather (specialty leather for automotive and aviation interiors). The HVAC specification for a tannery is a special case — the chemistry includes chromium salts, acid pickling, and a wide range of finishing solvents. Duct material is 316L stainless steel for general exhaust, FRP for acid-pickling exhaust, and welded carbon steel for the solvent-finishing booth. NFPA 33 and AS/NZS 60079 classifications apply.
Stage 11 — Outdoor apparel and technical textiles
The high-performance outdoor apparel sector has its own technical-textile requirements that bridge the garment-assembly and coating-and-lamination chapters of this guide. Macpac, Kathmandu, Mountain Designs and the broader Anaconda outdoor-retail business all use coated and laminated shell fabrics, technical insulation linings, and seam-sealed waterproof membranes. The HVAC specification for a high-performance outdoor-apparel design and sample facility combines a design-studio cleanroom (NC-40, 50% RH, F8 supply filtration) with a heat-sealing and seam-taping station that uses thermal welding rather than stitching.
Seam taping is the process of laminating a waterproof tape over the inside of a sewn seam to seal the needle holes. The heat-seal head runs at 400-500 degrees Celsius and generates a small but locally high VOC plume from the tape adhesive activation. The exhaust over the seam-tape station is local 316L stainless steel ducted to a dedicated activated-carbon adsorber. NFPA 33 classification applies because the tape adhesive is a flammable thermoplastic.
Why galvanized fails — the engineering audit
Most ductwork failures we see in textile mills come from a single root cause: someone specified galvanized steel for a duty cycle that called for stainless or FRP, the project came in under budget, and the duct lasted 18-36 months before the operator started seeing rust marks on the dyed fabric. The four most common failure modes are worth listing in detail.
- Dyeing-house humidity and chemistry. Galvanized steel exposed to 60-80% RH and acid or alkali chemistry corrodes through the zinc layer in 12-24 months. The zinc oxide flake falls into the dyebath. The operator reports colour-fastness failures and the duct is condemned.
- Lint accumulation. Cotton lint and wool dust accumulate in horizontal duct runs and bridge across joints. Bridged lint becomes a fire propagation path. The duct itself is not failing but the lint deposit makes the whole installation unsafe.
- Scouring exhaust corrosion. Wool scouring exhaust carries hot water vapour with detergent, ammonia and trace agricultural contamination. Galvanized fails through pinhole corrosion at the longitudinal seam within 18 months. The fix is 316L stainless with welded seams.
- Tenter-frame condensate. Tenter-frame exhaust at 150-180 degrees Celsius condenses on the inside of any duct section that drops below the dewpoint. The condensate is an oily, plasticiser-rich liquor that attacks galvanized rapidly. The fix is 316L stainless with welded seams, insulation R-1.0 minimum, and slope to a condensate drain.
SBKJ machine configuration for textile-sector fabricators
For an Australian duct fabricator serving the textile, clothing and fashion sector, our standard recommended machine configuration is built around the SBAL-V auto duct production line with the multi-coil and material-change-over feature, an SBTF-1602 spiral tubeformer for the dust-collection and lint-return mains, and a TIG seam welder for the stainless and FRP-lined sections that demand pressure-tight joints.
SBAL-V auto duct production line
The SBAL-V is a five-line auto duct line that takes coil stock through decoiling, levelling, notching, longitudinal seaming and corner folding to deliver a finished rectangular duct section. For textile work we recommend the multi-coil feature so the operator can change between galvanized G350 and 316L stainless steel in under an hour. The TDF flange end-forming is integrated into the line. The line accepts coil from 0.5 mm to 1.5 mm thickness across the full galvanized and stainless range.
SBTF-1602 spiral tubeformer
The SBTF-1602 forms spiral tube duct from coil stock at production rates suitable for a textile-mill dust-collection main. The 1602 model handles 80-1500 mm diameter and is configured for both galvanized G350 and 316L stainless coil. Lockformed seam is the default; for high-pressure dust mains the seam is welded by a follow-on TIG station.
TIG seam welder
For stainless and FRP-lined duct sections that need pressure-tight joints, a TIG seam welder is the production tool. The welder runs at 80-120 A across 1.0-2.0 mm stainless and produces a continuous longitudinal seam with no gas inclusion. The TIG station is integrated downstream of the SBTF-1602 for spiral tube or as a standalone station for rectangular duct from the SBAL-V.
Optional auxiliary stations
For a fabricator serving the full textile sector we typically recommend three optional auxiliary stations: a hydraulic press brake for FRP and polypropylene flange forming, a plasma cutter for branch and stub-in cutting in the dust-collection mains, and an automatic flange-bolt-hole punching station for the high-volume galvanized rectangular work serving the garment-assembly halls.
Process flow summary table
The full process flow from raw fibre to finished garment, with the duct material, velocity, acoustic and standards reference for each stage, is summarised below as a quick-reference for the engineer drafting the project specification.
- Wool stores. Galvanized G350 spiral. 8-12 m/s. NC-55. AS 1668.2.
- Wool scouring. 316L stainless welded seam. 12-15 m/s. NC-55. AS 1668.2, AS/NZS 60079.
- Wool drying. 316L stainless insulated. 15-18 m/s. NC-55. AS 1668.2 with heat recovery.
- Wool carding. Galvanized G350 spiral bonded and grounded. 18-22 m/s. NC-60. NFPA 484.
- Wool combing. Galvanized G350 spiral bonded. 16-18 m/s. NC-58. NFPA 484.
- Wool spinning. Galvanized G350 rectangular insulated. 8-10 m/s supply, 16-18 m/s lint. NC-55. AS 1668.2.
- Cotton ginning. Galvanized G350 spiral bonded. 20-24 m/s. NC-60. NFPA 484 with deflagration venting.
- Cotton baling. Galvanized G350 spiral bonded. 18-20 m/s. NC-58. NFPA 484.
- Weaving floor. Galvanized G350 rectangular insulated supply, spiral lint. 8-10 m/s supply, 18-22 m/s lint. NC-65. AS 1668.2 and NFPA 484 if cotton-rich.
- Knitting floor. Galvanized G350 rectangular insulated. 8-10 m/s supply, 16-18 m/s lint. NC-60. AS 1668.2.
- Warping and sizing. 316L stainless with condensate drain. 12-15 m/s. NC-55. AS 1668.2.
- Dyeing house (general). 316L stainless welded seam. 10-15 m/s. NC-55. AS 1668.2 and AS/NZS 60079.
- Dyeing house (sulfuric, azo). FRP. 10-12 m/s. NC-55. AS 1668.2 and AS/NZS 60079.
- Dyeing house (caustic). Polypropylene-lined steel. 10-12 m/s. NC-55. AS 1668.2 and AS/NZS 60079.
- Tenter frame. 316L stainless insulated welded seam with heat recovery. 15-20 m/s. NC-55. AS 1668.2.
- Calender. 316L stainless insulated. 12-15 m/s. NC-55. AS 1668.2.
- Coating booth. 316L stainless welded seam. 12-18 m/s. NC-55. NFPA 33 and AS/NZS 60079.
- Coating cure oven. 316L stainless insulated. 15-20 m/s. NC-55. AS 1668.2.
- Cutting room. Galvanized G350 spiral. 18-20 m/s. NC-55. NFPA 484 if cotton or wool rich.
- Sewing floor. Galvanized G350 rectangular insulated supply, spiral lint. 8-10 m/s supply, 14-16 m/s lint. NC-50. AS 1668.2.
- Pressing. Galvanized G350 insulated. 10-12 m/s. NC-50. AS 1668.2.
- Spotting cabinet. 316L stainless welded seam. 12-15 m/s. NC-50. NFPA 33 and AS/NZS 60079.
- Packing room. Galvanized G350 rectangular. 6-8 m/s. NC-45. AS 1668.2.
- Design studio and sample room. Galvanized G350 rectangular insulated. 4-6 m/s. NC-40. AS 1668.2.
- Swimwear cleanroom. Galvanized G350 rectangular insulated. 4-6 m/s with F8/F9 filtration. NC-40. AS 1668.2 cleanroom annex.
- Footwear bonding. 316L stainless welded seam. 12-15 m/s. NC-55. NFPA 33 and AS/NZS 60079.
- Tannery (general). 316L stainless welded seam. 12-15 m/s. NC-58. AS 1668.2 and AS/NZS 60079.
- Tannery (acid pickling). FRP. 10-12 m/s. NC-58. AS 1668.2 and AS/NZS 60079.
- Seam-tape station. 316L stainless welded seam. 12-15 m/s. NC-50. NFPA 33.
How SBKJ supports the project
SBKJ Group supplies duct-fabrication machinery to mechanical contractors and integrated mills serving the textile, clothing and fashion sector worldwide. Our typical engagement on a textile-mill project covers four areas.
- Specification review. Our engineers review the project ventilation drawing pack, identify the material change-over points between galvanized, 316L stainless, FRP and polypropylene-lined sections, and confirm the duct fabrication machinery is matched to the worst-case coil specification.
- Machine configuration. We supply the SBAL-V auto duct line with multi-coil feature, the SBTF-1602 spiral tubeformer, the TIG seam welder and any auxiliary stations matched to the project scope. Every machine ships with the matched roll set and PLC programme for the change-over between coatings.
- Factory Acceptance Test. Every line is FAT-tested in our workshop with the buyer's nominated coil before shipment. The FAT runs a full production cycle on each material the line will see in service.
- Installation, commissioning and training. SBKJ engineers travel to site for 5-10 days for installation, mechanical and electrical commissioning, operator training and a first-article duct sign-off. The training covers the change-over procedure between galvanized and stainless coil and the maintenance schedule for the multi-coil head.
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FAQ
Why does galvanized duct fail in a textile dyeing house?
Dyeing houses run at 60-80% relative humidity with acid, alkali and azo-dye chemistry vapour in the exhaust airstream. Galvanized rusts through the zinc layer in 18-36 months under those conditions and contaminates the dyebath with iron oxide particles. The fix is 316L stainless steel for acid exhaust, FRP or polypropylene-lined duct for sulfuric and azo-dye chemistry, and dedicated heat recovery on tenter-frame exhaust to drop the moisture load before it hits the duct.
What dust class applies to wool and cotton processing?
Cotton lint and wool dust are both classified as combustible particulate solids under NFPA 484. Wool dust has a lower Kst than cotton but both require explosion-protected dust collectors, deflagration vents on collection ducts, no-flat-bottom hoppers, and bonding and grounding on all duct runs over 6 metres. AS/NZS 60079 hazardous-area classification applies when solvent spotting or coating chemistry is also present in the same airstream.
What ductwork serves a tenter-frame finishing line?
Tenter frames run at 150-180 degrees Celsius with finishing chemistry, plasticisers and condensable oils in the exhaust. The duct is 316L stainless steel with welded longitudinal seams, slope to a condensate collection sump at 1:100 minimum, R-1.0 insulation on the supply side, and a dedicated air-to-air heat recovery exchanger upstream of the stack. Coating and lamination lines add NFPA 33 spray-finishing classification and a VOC-capture stage.
What is the noise criterion for a weaving mill?
A modern shuttleless weaving floor runs at 85-95 dB(A) machine noise. HVAC duct in the production hall is specified to NC-65 because anything quieter is masked by the looms anyway. Adjacent garment-assembly halls are NC-50, design and pattern-making rooms are NC-40, and customer-facing showrooms drop to NC-35. The duct material does not change but the velocity, terminal devices and acoustic treatment do.
What machine configuration does SBKJ recommend for a textile-mill project?
For a mixed textile, dyeing and finishing plant the typical SBKJ configuration is an SBAL-V auto duct production line in galvanized steel with a parallel 316L stainless option for dyeing-house and tenter-frame exhaust, an SBTF-1602 spiral tubeformer for dust-collection mains and lint-return ducts, and a TIG seam welder for the stainless and FRP-lined sections. We supply the matched roll set and PLC programmes for the change-over between coatings.
