Attribute Schema Library
Attribute schemaHVACR

Duct & Fittings Attributes

Duct and fittings covers round and rectangular sheet metal pipe, spiral and flat oval duct, elbows, tees, wyes, reducers, takeoffs, caps, flexible duct, plus the clamps and gaskets that join them. Buyers are contractor purchasing agents, sheet metal shops buying what they don't fabricate, kitchen exhaust and dust collection installers, and counter walk-ins who need an 8 in. crimped elbow today.

The category is dimension-driven, and the dimensions are not the whole spec. A 26 ga, 8 in., 90° galvanized elbow is several SKUs depending on gore count, centerline radius, which end is crimped, and whether it is gasketed. Gauge is an index into sheet steel thickness, not a thickness, and SMACNA ties minimum gauge to diameter and pressure class.

Most of that spec lives in fabricator dimensional catalogs and submittals, not the price file. Line data arrives as a description string — ELL 90 8 26GA GALV CRIMP — geometry encoded in abbreviations. Metric suppliers send mm and Pa, domestic ones inches and w.g., and G90 arrives as G-90, HDG, or nothing.

Core

Every SKU needs these. Without them the record is not a product, it is a row.

Fitting Type
enum
90° Elbow, 5-Gore

The first cut on every filter rail. Elbow, tee, wye, reducer, coupling, boot, takeoff, cap and pipe are not interchangeable families.

Duct Shape
enum
Round

Round, rectangular and flat oval are separate fabrication systems with separate fittings. Cross-shopping them wastes counter time.

Nominal Diameter
number · in
8

The number the buyer starts with. Spiral and clamp-together run 3 in. to 24 in. in 1 in. increments; flanged goes to 72 in.

Material
enum
Galvanized Steel

Drives corrosion service, weldability and price. Galvanized, 304/316 stainless, aluminum, black iron, PVC and FRP are different jobs.

Metal Thickness (Gauge)
enum · ga
26 ga (0.0187 in)

Sets whether the part meets SMACNA minimums at its diameter and pressure class. Carry the decimal inch alongside the gauge index.

Wall Construction
enum
Double-Wall, 1 in. Insulated

Single-wall, single-wall lined and double-wall change ID, weight, acoustics and price. Lined duct loses free area to the liner.

End Connection Type
enum
Crimped Small End / Raw Large End

Determines whether the part slips in or over the mating duct. The single most return-generating field in the category.

Nominal Length
number · in
60

Pipe ships in 60 in. and 120 in. lengths. Affects joint count, freight class and reinforcement spacing on the run.

Manufacturer Part Number
identifier
SWR-0826-60

The string contractors quote off a submittal, and the key that reconciles a fabricator's dimensional catalog to the price file.

GTIN / UPC
identifier
00812345678903

Required for marketplace listing, scan-at-counter and any GS1-based data exchange. Fittings are chronically unbarcoded.

Differentiating

What buyers actually compare on. This is where catalogs win or lose the filter.

Branch / Outlet Diameter
number · in
6

Tees, wyes, saddle taps and reducers need both ends. An 8x6 reducer is a different part from a 6x8, and buyers filter on both.

Elbow Angle
number · °
90

90°, 45° and 30° are separate SKUs and separate filter values. Adjustable elbows need their swept range, not a single angle.

Pressure Class
range · in. w.g.
+2 / −2

SMACNA defines ½, 1, 2, 3, 4, 6 and 10 in. w.g. classes. Positive and negative ratings differ; carry the signed pair, not one number.

Insulation R-Value
number · hr·ft²·°F/Btu
6.0

The filter on every flex duct listing. Common values are R-4.2, R-6.0 and R-8.0, reported per ASTM C518 at installed thickness.

Seam Construction
enum
Spiral Lockseam

Spiral lockseam, laser-welded longitudinal, Pittsburgh lock and welded liquid-tight behave differently on leakage and on grease service.

Compliance & identifiers

Standards, regulatory data, and the identifiers channels reject you for missing.

SMACNA Seal / Leakage Class
enum
Seal Class A / CL6

Specs call out Seal Class A/B/C and Leakage Class CL3/CL6/CL12/CL48. Gasketed fittings win those jobs; unsealed slip fittings do not.

UL 181 Classification
enum
UL 181 Class 1 Air Duct

Class 1 air duct requires flame spread ≤25 and smoke developed ≤50 per ASTM E84. Code officials reject flex without the listing.

Country of Origin
enum
United States

Drives duty, Buy American eligibility on federal and institutional work, and customs paperwork on the import line.

The fields that aren't in the schema at all

What most duct & fittings catalogs are missing.

The table above is the schema most catalogs already have. These are the attributes that usually aren't in it — each one surfaced by a signal from the live market rather than by an audit of what's already there. This is what Anglera's Schema Foundry does on a real catalog, in this category.

Supplier signal
+ Zinc Coating Designation (G60 / G90)

Fabricator submittals state the ASTM A653 coating class explicitly, and job specs call G90 for rooftop and damp locations. Most distributor catalogs stop at 'Galvanized Steel' with no coating field.

Loses every spec'd job that requires G90. The buyer cannot confirm it from the listing, so they call a competitor whose page says it.

Search signal
+ Centerline Radius Ratio

Buyers search '1.5D elbow' and 'long radius elbow' and get zero results. Catalogs carry angle and diameter but no radius field, so stamped short-radius and gored 1.5D elbows sit in one listing.

Wrong elbow ships on a static-pressure-sensitive run. Return, plus a rework the contractor blames on the counter.

Supplier signal
+ Maximum Service Temperature

Manufacturers publish it — G90 galvanized rated to 390 °F, 304 and 316 stainless to 1100 °F. It appears in the engineering spec sheet and almost never on the product record.

No way to filter duct for oven, dryer or high-temp process exhaust. Those RFQs route to the specialist who publishes the number.

Competitor signal
+ Gasket Material and Temperature Range

Complete-seal and clamp-together fittings ship with EPDM or silicone gaskets, and the datasheet gives the elastomer and its range. Catalogs say 'gasketed' with no material behind it.

Gasket fails outside its range or against an incompatible airstream. The fitting gets blamed and the whole line loses the account.

Marketplace signal
+ Gore Count on Elbows

Dimensional catalogs list 3-gore, 5-gore and 7-gore elbows as distinct parts at distinct prices. Web listings collapse them to '90° Elbow' and pick whichever the description string implied.

Price and pressure-drop mismatch between the quote and what ships. Buyers who know the difference cannot filter for it and go elsewhere.

How Schema Foundry finds these

Messy in, governed out.

The same value, spelled every way HVACR suppliers spell it. A filter only works once they agree.

Metal Thickness (Gauge)
26 GA26ga26 Gauge#260.0187"0.55 mm
26 ga (0.0187 in)

Gauge is an index into a sheet steel table, not a unit. Metric suppliers send mm and never mention gauge at all.

Material
GALVGalv. SteelG90 GalvanizedHot Dipped GalvZinc Coated SteelGI
Galvanized Steel (ASTM A653)

Coating class belongs in its own field. Leaving G90 inside the material string makes it unfilterable and hides G60 stock.

Pressure Class
2" WG2 in. w.g.+2/-2 SP2" W.C.500 PaClass 2
±2 in. w.g.

w.g., w.c. and Pa all appear. Sign matters most: a fitting rated +2 is not rated −2 on a return or dust collection line.

End Connection Type
CrimpedCrimp x RawMale/FemaleC x RSmall End CrimpedSlip Fit
Crimped One End / Raw One End

Male/female is ambiguous on round duct — fittings are male, pipe is female. Say which end is crimped and at what diameter.

What buyers ask

Every one of these should be answerable from the attributes above. If it isn't, that's a gap.

  • Is the 8 in. end crimped or raw — does it slip into my spiral pipe or over it?
  • Is this G60 or G90? It's going on a rooftop curb.
  • Is that a 1.5D gored elbow or a stamped short-radius one?
  • Will this fitting hold at negative 10 in. w.g. on a dust collection branch?
  • What's the R-value on this flex, and is it UL 181 Class 1?
  • Is 26 ga legal at 8 in. for a 2 in. w.g. system?
  • What gasket is in the complete-seal fitting, and what's its temperature range?
  • Is the reducer 8x6 or 6x8 — which end takes the trunk?

What channels require

The same SKU, different mandatory fields per destination.

Distributor's own site (faceted search)
Fitting TypeDuct ShapeNominal DiameterBranch / Outlet DiameterMetal Thickness (Gauge)End Connection Type
Amazon Business
GTIN / UPCManufacturer Part NumberBrandNominal DiameterMaterialCountry of Origin
HARDI / GS1 US data exchange
GTIN / UPCManufacturer Part NumberBrandUNSPSCCountry of OriginPackage hierarchy
Contractor procurement portals (submittal-driven)
Manufacturer Part NumberPressure ClassSMACNA Seal / Leakage ClassUL 181 ClassificationMetal Thickness (Gauge)Material

Duct & Fittings data, in practice

Why isn't gauge enough on its own?

Gauge is an index into a sheet steel thickness table, and it only means something next to diameter and pressure class. SMACNA sets minimum gauge as a function of the duct's size and its pressure class — 22 ga is the floor for round spiral at 2 in. w.g. up to 36 in., while 26 ga is common on smaller low-pressure residential runs. A listing that says '26 ga' and nothing else cannot answer whether the part suits the job. Gauge also says nothing about corrosion service: G60 and G90 are the same steel thickness with different zinc weights, so coating designation has to be its own field.

What drives the variant explosion in this category?

Multiplication. Diameter × gauge × material × wall construction × end configuration, then branch size on top for any tee, wye or reducer. An 8 in. 90° elbow alone splits by gore count, centerline radius, crimped or raw ends, and gasketed or plain. Reducers are directional — 8x6 and 6x8 are different parts. Most catalogs carry diameter and gauge because those survive in the description string, and drop the rest because they never had a field for them. That is why two physically different SKUs so often share one listing.

Is SMACNA a product certification?

No. SMACNA's HVAC Duct Construction Standards — Metal and Flexible is a construction standard for the fabricated system, not a mark you put on a fitting. A fitting isn't 'SMACNA certified'; it is built to meet a pressure class (½, 1, 2, 3, 4, 6 or 10 in. w.g.) and a seal class (A, B or C), which then maps to a leakage class such as CL6. Carry the pressure class and the seal class as attributes and let the engineer do the compliance check. UL 181 is different — that is a real product listing, and Class 1 air duct is the one code officials look for on flex.

Where does the missing spec actually live?

In documents, not in the ERP. Fabricator dimensional catalogs carry the gore counts, centerline radii and end configurations. Engineering spec sheets carry the coating designation, the service temperature ceiling and the gasket elastomer. Submittal packages carry the pressure and leakage classes. The price file carries a 40-character description string. Anglera reads the PDFs, the spec tables and the drawings, discovers the fields your schema never had, and normalizes what comes back into one governed vocabulary. Your PIM stores the data. Anglera does the work.

More HVACR schemas

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