- SBAL
- SBKJ Auto Line — a family of automatic rectangular HVAC duct production lines.
- SBAL-V
- SBKJ's flagship fully automatic U-shape rectangular duct production line, output 800–2,500 m²/day with a single operator. View specs →
- SBAL-III
- Semi-automatic SBKJ rectangular duct production line with hydraulic notching and shearing, ~1,000 m²/shift. View specs →
- SBTF
- SBKJ Tube Former — a family of spiral duct forming machines covering Φ80 mm to Φ2,000 mm.
- TDF (Transverse Duct Flange)
- A flange roll-formed directly on the end of a rectangular duct section, used to bolt sections together. The dominant global standard for rectangular duct connection. Compare to angle flange →
- Pittsburgh lock
- A self-locking longitudinal seam used to close a rectangular duct, formed by interlocking two folds and hammering them flat.
- Drive cleat
- A U-shaped sheet-metal strip slid over two duct flanges to lock them together. Common on smaller rectangular duct.
- Spiral tubeformer
- A roll-forming machine that turns a flat coil into a continuous spiral round duct, with a forming head and a cut-off station. Read the explainer →
- Forming head
- The set of profiled rollers in a spiral tubeformer that bend the strip into a tube and lock the spiral seam.
- Flying shear
- A cutting station that cuts spiral duct while it is still moving through the line — no stop, no swarf, no secondary deburring.
- Saw blade cutting
- A spiral duct cut-off method using a rotating saw blade. Mechanically simpler than flying shear; produces some swarf.
- Lockformer
- A multi-station roll former that produces Pittsburgh locks, drive cleats and S-cleats on rectangular duct edges. View SBKJ lockformer →
- Gore-locker (gorelocker)
- A hydraulic machine that closes the longitudinal seam of round duct fittings (elbows, reducers) by interlocking the two edges. View SBEM-1250 →
- Coil line
- The decoiler, leveller and feeder section that handles raw galvanized or stainless coil at the front of an auto duct line.
- Decoiler
- A motorized reel that holds the coil and feeds it into the line at controlled speed and tension.
- Notching
- Cutting V or rectangular notches at the corners of a flat blank so it can be folded into a U-shape duct.
- Plasma cutter
- A CNC cutting head that uses ionized gas to cut sheet metal — faster than oxy-fuel and cleaner than mechanical shearing.
- Hoop machine
- A machine that forms structural hoop reinforcements onto large rectangular duct.
- Beading
- A rolled rib added to large duct walls for stiffness and aesthetics.
- Slitting
- Longitudinal cutting of a wide coil into narrower strips, often a pre-step to spiral forming.
- Galvanized steel
- Steel sheet coated with zinc for corrosion resistance — the most common material for HVAC duct.
- SMACNA
- Sheet Metal and Air Conditioning Contractors' National Association — publishes the duct construction standards used in North America.
- Seal Class A
- The tightest SMACNA leakage class — all transverse joints, longitudinal seams and duct wall penetrations sealed.
- Static pressure class
- The internal pressure rating of a duct section, in inches water gauge or Pascals.
- Run-out table
- A roller table at the exit of a forming line that supports finished duct as it leaves the machine.
- Workshop layout
- The 2D or 3D plan showing where each machine, storage zone, utility and traffic path goes in a duct factory. Read the layout guide →
- Turnkey project
- A complete delivery — design, equipment, installation, training and commissioning — handled by a single supplier.
- PLC
- Programmable Logic Controller — the industrial computer that drives the auto duct line's sequencing, motion and safety logic.
- CNC nesting
- Software that arranges duct part shapes on the coil to minimize scrap before cutting.
- CE marking
- European Conformity mark certifying that machinery meets EU health, safety and environmental requirements.
- Roll forming
- A continuous bending process that progressively shapes a strip of metal into a fixed cross‑section by passing it through a series of paired forming rolls. The core technology behind every TDF former, lockformer and spiral tubeformer in the SBKJ catalogue.
- Standing drive slip
- An alternative SMACNA rectangular duct connection method that uses a folded vertical lip on the duct end. TDF is a refinement of the standing drive slip principle.
- Cross-break
- A shallow X-shaped diagonal crease pressed into the flat side of large rectangular duct to stop the wall from "oil‑canning" under pressure.
- Snap lock
- A self-engaging longitudinal seam used as an alternative to Pittsburgh lock on light-gauge round and rectangular duct — faster to close, slightly less rigid.
- S-cleat
- An S-shaped sheet-metal strip used to join two rectangular duct sections face-to-face on smaller commercial ducts. Lighter than TDF, only suitable up to ~400 Pa.
- Lock seamer
- The hammer or roller station that closes a Pittsburgh lock or snap lock seam after the two folded edges have been engaged.
- Spiral duct
- Round duct produced by helically winding a strip of steel and locking the edges into a continuous lockseam. The dominant round-duct construction worldwide.
- Lockseam
- The interlocked spiral seam that runs along the length of a spiral duct, formed by folding and rolling the strip edges as the duct is being made.
- HVAC
- Heating, Ventilation and Air Conditioning — the building services trade that uses ductwork to distribute conditioned air. The end customer for almost everything SBKJ builds.
- Galvalume / Aluzinc
- A coil coating using a zinc-aluminium alloy that gives better corrosion resistance than plain galvanised steel. Common on coastal and marine duct projects.
How to use this glossary
This glossary is the SBKJ engineering team's working vocabulary — the terms we use day-to-day when we talk to customers, write quotations, and train operators. We have deliberately kept the definitions short and plain, because most of our customers are running production lines and need a quick reference, not an academic treatment. If you are reading a SBKJ specification document or a SMACNA standard and a term is unclear, this is the page to bookmark. If you find a term that should be in here but isn't, email sales@sbkjduct.com and we will add it on the next quarterly review. Every published definition has been signed off by a senior mechanical engineer with at least ten years of HVAC ductwork machinery experience.
Glossary review and update policy
The glossary is reviewed every quarter by SBKJ's QA & Engineering team. Definitions are added, retired, or rewritten in response to three triggers: new SMACNA, EN, or AS/NZS standards revisions; new SBKJ machinery families that introduce new terminology; and customer feedback when a term is misunderstood in commercial discussions. The current page contains 40 terms covering the four major sub-domains of HVAC ductwork machinery — rectangular duct, round duct, fittings, and connections — plus the standards bodies and certification frameworks that govern them.
Frequently asked questions
Why does SBKJ publish a public glossary?
Because most international duct buyers do not work in English as a first language, and HVAC machinery vocabulary varies between SMACNA, EN, AS/NZS and Chinese standards. A short, plain-English glossary saves hours of back-and-forth in commercial discussions and reduces the risk of mis-spec at the quotation stage.
How often is the glossary updated?
Quarterly, by the SBKJ QA & Engineering team. New terms are added when new standards are published or when a SBKJ customer raises a clarification question that the current glossary does not answer.
What is the difference between TDF and a standing drive slip?
TDF (Transverse Duct Flange) is a refined commercial implementation of the standing drive slip principle — same idea (a folded vertical lip on the duct end), but with a hardened roll profile, plastic or zinc corner blocks, and gasket compatibility for SMACNA Seal Class A. Standing drive slip is the SMACNA chapter heading; TDF is the modern manufacturing method.
Can I use this glossary in a tender or specification document?
Yes — the SBKJ glossary is published under a free-use editorial licence for non-commercial reference. Please link back to this page if you reproduce more than three definitions in a single document.
What if a term I am looking for is not here?
Email sales@sbkjduct.com with the term and a short context line. SBKJ engineers reply within 12 hours and the term will usually appear in the next quarterly update.
