Spiral Round Ducting Installation Methods

Posted by Insight Control System February 23, 2025

Spiral Round Ducting Installation Methods

In this Article we are going to see Installation and Insulation of Spiral Round Ducting and Duct Accessories.

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Spiral Round Ducting Installation

Spiral round ducting is a type of duct work commonly used in HVAC (heating, ventilation, and air conditioning) systems for efficient air distribution.

It is characterized by a helical (spiral) seam that enhances strength and rigidity.

Basic Features of Spiral Round Ducting

☑️ Construction:

Made from galvanized steel, stainless steel, Aluminum, or PVC.

Manufactured by forming metal strips into a continuous spiral seam.

☑️ Advantages:

Higher Strength: The spiral seam adds rigidity, reducing the need for additional reinforcements.

Leakage Resistance: Minimizes air leakage compared to traditional rectangular ducts.

Cost-Effective: Requires less material and labor for installation.

Smooth Airflow: The round shape reduces turbulence and enhances efficiency.

Aesthetic Appeal: Often used in exposed duct work designs for industrial or modern interiors.

☑️ Common Applications:

HVAC systems in commercial and industrial buildings.

Ventilation and exhaust systems in factories and kitchens.

Underground duct systems for air distribution.

HVAC Applications

☑️ Sizes & Fittings

Available in various diameters, typically ranging from 4 inches to 60" inches.

Can be connected using fittings like elbows, reducers, and couplings.

INSTALLATION:

✅ Scope and Purpose:

This Method Statement covers the on site installation of Spiral round ducting and duct accessories and the requirement of checks to be carried out.

✅ Reference Documents:

Project Specifications,
Approved shop drawings (latest revision),
Approved material submittals,
Duct work standard OW 144,

✅ General Materials:

GI Spiral round ducting generally installed in for FCU return air, and supply air as shown in approved shop drawing includes

Spiral round ducting,
Fittings such as Elbows,
Tees,
Couplings,
Reducers,
Collars etc,
Volume control dampers,
Flexible ducting insulation

General Materials

✅ General Equipment:

Portable grinding Machine,
Drilling Machine,
Sheet metal cutting tools and bender,
Spirit level,
Scaffolding,
Duct erector hand tools,
Testing instruments,
Air Compressor,

General Equipment

✅ Responsible Persons:

Project Engineers,
Construction In-Charge,
Site Engineer and Site supervisor,
QA and QC Inspectors,
Safety officer,
Site Foremen,
Pipe fitters and Welders,
Helpers

Responsible Persons

✅ Method of per Installation:

1. Ensure that approved material required to carryout work will be available.

2. Prior to commencement of work, area and access will be inspected to confirm that the site is ready to commence the work,

3. Check all the GI Spiral ducting received are pre fabricated with tag number labelled and received at site in accordance with specifications and correct dimensions as per approved drawings.

4. All relevant documentation and material applicable to particular section of works will be checked by site engineer before commencement.

5. Physical verification of material will be carried out for any damages prior to taking from stores.

6. The site engineer or supervisor will give necessary instruction to tradesman and provide necessary construction shop drawings.

7. The site engineer or supervisor will also check that tools and equipment available are in compliance to contract requirements.

8. The site supervisor also explains tradesman regarding safety pre-cautions to be observed.

✅ Method of Installation:

1. Prior to commencement of work coordination will be done with other services.

2. Determine the position of duct supports as per approved Shop drawings and coordinated layouts and specification.

HVAC Ducting Drawing

3. Prepare and fix the duct supports as per approved construction drawing and specification.

4. Any cut edges of angles, channels or threaded rods will be touch up with Zinc rich paint.

5. Transport the Duct pieces and fittings to final location.

6. Before assembly ensure that all ducts are free from dirt.

7. Check that ducts and fittings are undamaged. This is specially important with regard to the rubber gaskets.

Duct Pieces & Fittings

8. Assemble the Duct pieces and fittings as per approved shop drawing ensuring the alignment.

9. Push the fittings into the duct right to the stop, Turning the fitting a little makes insertion easier.

10. Fasten fittings to the duct with self tapping screws or centered pop rivets.

11. Distribute the screws or pop rivets evenly around the circumference, ensuring the rubber gaskets are not damaged i.e. placing them approximate 10mm from stop and end of the duct. In the event of incorrect assembly, holes caused by screws or pop rivets must be sealed.

Screws or Pop Rivets

12. Raise the duct work on to the supports ensuring that each length is aligned and levelled with preceding length as per dimensions shown on approved shop drawings.

13. Ensure that duct work is clean and no tools/ construction debris exists within duct work before proceeding to next length.

14. All open ends of the duct works shall be temporarily sealed with polythene Sheets/ply wood before leaving the job site to prevent moisture and dirt.

15. Ensure that all accessories like Volume control dampers, Test points, Sensors are installed in accordance with approved shop drawings.

Installation of duct work

16. Installation of duct work (complete with accessories) shall be checked before applying insulation at joints.

17. Insulation of duct work will be completed as per manufacturer's recommendations (copy enclosed).

18. Ensure the duct surface is clean and dry before re-applying any insulation material, Apply thinner /cleaner where necessary to make the area grease free.

19. Apply glue recommended by manufacturer with an even spread on complete surface of insulation sheet.

20. Once the glue on the sheet gets dry, apply glue on the GI duct and let it dry, then stick the sheet on one end and slowly press the sheet on the duct from one end to the other so as to ensure that the sheet sticks on the GI duct completely avoiding air bubbles between the insulation sheet and GI duct.

21. In the areas where the GI duct comes into contact with the duct hangers, rigid support is recommended such as wood.

duct hangers

The wood piece should be glued onto the duct hanger and layer of rubber to be glued on the wood, so that there is no direct contact between the duct insulation and the wooden piece thus preventing tearing of the duct insulation.

In case the positioning of the support is available in advance, wood by itself can be used.

In this case it has to be made sure that insulation will be glued to the wood from both sides accordingly.

22. Where insulated duct work passes through fire rated wall/partitions the gap between sleeve and duct work shall be filled with approved fire barrier.

fire rated wall or partitions

✅ Quality Control:

QCE along with Project Engineer and site Supervisor will monitor that all components are installed as per the contract specifications and approved submittals.