Spiral ducting is one of the most widely used forms of circular ductwork in commercial and industrial ventilation systems. It is strong, efficient, relatively lightweight and available in a wide range of diameters and fittings.
It is commonly used for supply air, extract air and general ventilation in offices, warehouses, factories, schools, retail units and many other commercial buildings.
What is spiral ducting?
Spiral ducting is circular sheet metal ductwork manufactured from a continuous strip of metal that is formed into a tube with a spiral seam running along its length.
The spiral seam gives the duct additional rigidity and allows long sections to be manufactured efficiently while maintaining a consistent circular shape.
How is spiral ducting manufactured?
Spiral ducting is usually produced using specialist forming machinery. A continuous coil of sheet metal is fed into the machine, shaped into a circular tube and mechanically locked together along a spiral seam.
This manufacturing method produces a strong duct with a smooth internal airflow path and consistent dimensions.
Why is spiral ducting popular?
Spiral ducting is widely used because it combines good airflow characteristics with simple installation and strong mechanical performance.
Its circular shape also means it can often use less material than equivalent rectangular ductwork while maintaining good structural strength.
Advantages of spiral ducting
- Efficient airflow
- Strong and rigid construction
- Relatively lightweight
- Quick installation
- Wide range of standard fittings
- Good appearance when left exposed
- Suitable for many commercial and industrial applications
Common spiral ducting sizes
Spiral ducting is available in many different diameters to suit the airflow requirements of the ventilation system.
Smaller diameters may be used for branch runs and local extract systems, while larger diameters are commonly used for main supply and extract ducts.
The correct duct size should be selected based on required airflow, air velocity, pressure loss and system design.
Materials used for spiral ducting
The most common material used for spiral ducting is galvanised steel because it offers good strength, durability and corrosion resistance for general ventilation applications.
Spiral ducting can also be manufactured from stainless steel or aluminium where the environment or project specification requires it.
Where is spiral ducting used?
- Warehouses
- Factories
- Offices
- Schools and colleges
- Retail units
- Workshops
- Restaurants
- Commercial kitchens
- Industrial extraction systems
Spiral ducting fittings
A complete spiral ductwork system uses a range of fittings to change direction, alter diameter and create branches.
- Bends
- Reducers
- Tees
- Branches
- Couplers
- End caps
- Dampers
- Access doors
How is spiral ducting installed?
Spiral ducting is normally installed using purpose-made fittings and couplers. Sections are joined together, sealed where required and supported using suitable brackets, straps or suspension systems.
Correct support spacing and sealing are important to maintain system performance and prevent movement or air leakage.
Spiral ducting vs rectangular ducting
Both spiral and rectangular ductwork are widely used in commercial ventilation systems.
Spiral ducting is often preferred where there is sufficient space because its circular shape provides efficient airflow and good rigidity.
Rectangular ductwork can be more suitable where space is limited or where ductwork needs to fit closely against walls, ceilings or structural elements.
Is spiral ducting suitable for exposed installations?
Yes. Spiral ducting is frequently used in exposed ceiling installations because its uniform appearance can form part of the building design.
It is commonly seen in modern offices, restaurants, retail units and industrial-style interiors.
How do I choose the correct spiral ducting?
The correct ducting depends on airflow requirements, available space, pressure class, material specification and intended application.
For commercial systems, duct sizing should normally be determined by the ventilation designer or mechanical contractor.
Conclusion
Spiral ducting is a versatile, strong and efficient solution for commercial and industrial ventilation systems. Its circular construction, wide range of fittings and straightforward installation make it one of the most commonly used ductwork systems in the HVAC industry.
Choosing the correct diameter, material and fittings helps ensure the ventilation system performs efficiently and reliably.