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Industrial Ducting Glossary & Definitions

Industrial Ducting Glossary | Duct Components & Terms


Ductwork Types


1. Flanged Duct

  • Typically medium to heavy gauge duct that is joined using angle rings (also known as companion rings) that bolt to the ring on the adjoining part. Rings may join VanStoned ends where the end of the duct is turned out 90 degrees and are then ‘sandwiched’ between the rings. Or they may be welded to the duct by a full or intermittent welds. Gaskets may be used between the rings.
2. Spiral Duct

  • Duct that is made by mechanically locking a narrow coil of metal in such a way as to make a long piece of duct giving it the spiral appearance. Usually made in light to medium gauge. Ends can be joined in a big end/small end method that uses tec-screws or tape to secure the connection or by any number of flanging/companion ring methods- all of which are affixed to the end of the duct parts and then joined with screws/bolts.
3. Clamp Together Duct (Rolled Lip)

  • Duct and components with a rolled lip formed on the end by a mechanical process. The resulting rolled end resembles the end of a metal 55 gal drum but smaller. A gasketed, over-center locking clamp is used to encompass and pull the ends together and secure them.
4. Clamp Together Flanged Lip

  • Duct and components with a flat edge that is formed at 90 degrees to the end of all parts. The end is the same as a VanStone end used in flanged duct. A gasketed, over-center locking clamps are used to encompass and pull the ends together and secure them.
5. Raw End

  • Raw end duct made of gauges suitable for welding the ends with a full weld.

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Ductwork Materials


1. Hose Adapters

  • Short pieces of duct with a knurled end on one end, over which flex hose is slid and then clamped tight. The knurled bulge keeps the hose from pulling off the duct..
2. Hangers

  • Hangers enable the suspension of the duct from the ceiling/roof/truss system. They are sized and spaced along the duct based upon the weight of the duct if 80% full of the material being collected/conveyed.
3. Angle Ring

  • Angle iron that is rolled to the duct diameter and then punched for the proper hole configuration. An angle ring on one piece of duct is joined to the angle ring of the next part with bolts.

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Typical Applications


1. Wood Dust

  • Chip, dust or shavings generated by any number of wood working machinery. Special hoods and manifolds for multiple pickup are common in these applications.
2. Oil Mist Collection

  • Metal grinding/cutting applications require effluents to cool the part and high speed cutters and the resulting mist and waste material must be removed.
3. Fume

  • Welding smoke, plasma tables, cookers, coolers, bathes, chemicals all generate fume that can be harmful to the personnel and operation and should be removed.
4. Paper Trim

  • The long ribbons/ ‘off fall’ from paper rolling trimming operations need to be safely and quickly removed.

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Special Fabrications & Solutions


1. Diverter Valves

  • Diverter valves are heavy gauge (1/4”), square body branches, with a heavy gauge internal swinging door that diverts the air or material flow from the lateral branch to the center line leg. The door has a replaceable seal around the perimeter so as to provide a tight seal. A common application is for truck loading of material where the door diverts the material from one truck or bin to the other. Can be manual or pneumatic/automatic.
2. No Loss Stackheads

  • No Loss Stacks eliminate fan exhaust backpressure that robs the fan of horse power and reduces the air flow, by providing a completely straight path for the air. Because they are typically mounted on the roof in the vertical position, they leave the fan vulnerable to rain. Therefore a larger outer duct is slid over and attached to the inner duct leaving a gap between the two. The larger duct extends past the outlet duct by a length of two time the diameter of the outlet/exhaust duct. Rain then runs down the inside of the outer duct and out the space left between the two ducts.
3. Galvanized / galvanized coating

  • Typically a G-90 grade. Multiple gauges. The most common and economical material. Easy to form and spot weld, and can be painted.
4. Stainless Steel

  • 304 and 316 are standard grades. 316 has more nickel and greater resistance to corrosion. Typically used in food or corrosive applications. Multiple gauges.
5. Carbon Steel

  • Untreated cold rolled steel. Multiple gauges. Typically used for parts that are going to be painted. .
5. Aluminum

  • Light weight but usually too malleable for use as ducting.

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Ductwork Fittings & Components


1. Elbows

  • Curved duct that creates a variety of ‘turns’ in various degrees. Typically made in 90, 60, 45 or 30 degrees to compliment the 30 and 45 degrees in branches. The length of the turn is referred to as the radius and is typically 1xDiameter, 1.5xDiameter or 2.5x Diameter.
2. Branches

  • Also called laterals, branches allow for convergence of lateral ductwork.
    • Standard branches, where the converging duct enters the main trunk from one side only and typically at an angle of 30 of 45 degrees to the center line.
    • Y branches, where the duct is converging from both sides of the center line again at either 30 or 45 degrees to the center line. There is no straight on entrance, only the laterals.
    • Double branches, where the duct has an inlet, an outlet and two converging ducts usually (but not necessarily) on opposite sides of the center line.
3. Reducers

  • A part that changes from one size to another.
4. Adapters

  • Joins two different connection styles. For example- Flanged to Rolled Lip or Rolled Lip to Spiral.
5. Bell Mouths

  • Short straight duct that is spun and formed to produce a bugle mouth. Used as suction hoods.
6. Floor Sweeps

  • Floor mounted units with kick open doors into which debris can be sweep.
7. Cut-Offs/Gates

  • Gates provide a means for inserting a blade into the air stream so as to close off the air flow.
8. Automatic Gates

  • Air operated Cut-offs. Electric solenoids control the air flow to the pneumatic cylinder, opening and closing it upon demand through electrical current.
9. Butterfly Valves/Dampeners

  • Control air flow in the duct by variably adjusting a disc that is the same diameter as the duct, and is mounted to a pivoting rod that runs through the duct. The rod is joined to an adjustable quadrant mounted on the outside of the duct. The rod and disc may be offset or centered to the inside of the duct.
10. Oil Mist Accumulator

  • Oil mist accumulators remove excessive mist and effluent through a slowing chamber containing a series of expanded metal agglomerating cones. As the air enters the larger chamber it slows and particles agglomerates on the expanded metal cones, where it then migrates by gravity to the outer edges of the cone and drips into the sump below. A return hose allows the liquid to flow back to the machine.
11. Oil Mist Curbs

  • Because flex hose is commonly used for the final ducting connection and because it CANNOT be clamped tight enough to prevent leaks in ‘wet’ applications, the oil mist curb is attached to the machine and then the hose to the curb. The leaking liquid is captured in the curb, a trough, which is welded to the outside of the inner duct. The liquid then seeps back into the unit through weep holes drilled around the base of the trough and through the inner duct.
12. Silencers

  • Exhausting air from a fan is turbulent and therefore noisy. Silencers, straighten the air and dampen the turbulence with insulation that surrounds the inner duct. The inner duct is constructed of expanded metal duct to allow both the air and sound to contact the insulation.
13. Spark Traps/Coolers

  • Spark traps provide a tortuous path for sparks from welding, grinding, and/or metal cutting applications. This presents the spark with more moving air and provides time for it to extinguish. A finned cone, spins and diverts the spark laden air around and past the outlet so that it must spin and reverse direction twice before exiting the unit. This time and turbulence provides the perfect condition for the spark to burn out. However, no apparatus is completely able to guarantee against fire and a sophisticated spark detection and extinguishing system is recommended.
14. Cyclones

  • Cyclones utilize cyclonic spinning action to separate dust and material out of the air stream. The particles spin to the outside of the larger section and then forced by the entry of more air, into the smaller cone where the cleaned air on the inside of the ‘cyclone’ is forced out an inner duct. The spinning action slows as the air exits and the dust falls to the bottom of the unit. Removal is accomplished by having a sealed bin at the bottom or with an air lock.
15. Manifolds

  • A convergence of multiple ducts into a series of branches, double branches and/or Y branches in such a close proximity to one another that a special configuration requiring design and fabrication.

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