Duct Work Installation

SCOPE AND PURPOSE

This "Method Statement" covers the on-site installation of HVAC ductwork and accessories and the required checks to be carried out.

REFERENCE DOCUMENTS

• Project Specifications
• Approved shop drawings (latest revision)
• Approved material submittals
• Ductwork standard DW 144

GENERAL

HVAC ductwork generally includes all types of Supply Air Ducts, Return Air Ducts, Fresh and Exhaust Air Duct and their accessories such as duct elbows, offsets, transformation pieces, branch-off pieces, tee connections, access doors, Fire Dampers, Volume Control Dampers, Sound Attenuators, flexible ducting, and insulation.

EQUIPMENT

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

RESPONSIBLE PERSONNEL

• Project Engineers
• Construction In-Charge
• Site Engineer/Site Supervisor
• QA/QC Inspectors.
• Safety officer
• Site Foremen
• Pipefitters / Welders
• Helpers
  

METHOD OF PRE INSTALLATION

• Ensure that the approved material required to carry out work is available.
• Prior to the commencement of work, the area and access will be inspected to confirm that the site is ready to commence the work
• The site engineer will check all relevant documentation and material applicable to particular work sections before commencement.

• Physical verification of material will be carried out for any damages prior to taking it from stores.
• The site engineer/supervisor will instruct the tradesman and provide necessary construction/shop drawings.
• The site engineer/supervisor will also check that the tools and equipment available are in compliance with contract requirements.
• The site supervisor also explains to tradesmen regarding safety precautions to be observed.
• Prior to Leak testing, Site Engineer will ensure that Calibrated test kit is available and in good condition.

METHOD OF INSTALLATION

1. Prior to the commencement of work, coordination will be done with other services.
2. Determine the position of duct supports as per approved construction layouts and specifications.
3. Prepare and fix the duct supports as per the approved construction drawing and specification.
4. Any cut edges of angles, channels, or threaded rods will be touched up with Zinc rich paint.
5. Transport the Duct pieces and fittings to the final location.
6. Pre-assemble the Duct pieces and fittings as per the approved shop drawing, ensuring the alignment.
7. Acoustic insulation will be carried out wherever required.
8. Raise the ductwork onto the supports, ensuring that each length is aligned with the preceding length as per the dimensions shown on approved shop drawings.
9. Approved duct sealant shall be applied to the joints. Any excess sealant so that the joint is left in a clean and tidy condition.
10. Ensure that ductwork is clean and no tools/ construction debris exist within the ductwork before proceeding to the next length.
11. All open ends of the ductwork shall be temporarily sealed with polythene sheets/plywood before leaving the job site to prevent moisture and dirt.
12. Ensure that all accessories like Volume control dampers, Fire dampers, Access doors, Test points, and Sensors are installed as per approved shop drawings.
13. Installed sound Attenuators according to approved shop drawings
14. Installation of ductwork (complete with accessories) shall be checked before applying insulation at joints.
15. A leak test will be carried out for ductwork as applicable in the DW144 standard.
16. Insulation of ductwork will be completed as per the manufacturer's recommendations (copy to be enclosed).
17. Ensure the duct surface is clean and dry before applying any insulation material.
18. Ensure the thickness of the insulation is as per the approved shop drawing.
19. Ensure that all edge joints are closely butted and ends are flush and seated properly.
20. Apply ALUGLASS Tape (Self-Adhesive Aluminium Foil Laminated on Glass fabric) at the Joints of the insulation.
21. Ensure the continuity of the vapor barrier and other protective coatings on the insulation surface as well as at connections.
22. Ensure firm adherence of insulation around ducting by using approved adhesive between sheet metal and Insulation material.
23. Where insulated ductwork passes through fire-rated walls/partitions, the gap between the sleeve and ductwork shall be filled with approved fire barriers.

QUALITY CONTROL

• QC Engineer, Project Engineer, and Site Supervisor will monitor that all components are installed per the contract specifications and approved submittals.
• Inspection Request (IR) shall be submitted to the Main Contractor/Consultant during the following stages:-

1. After completion of installation, before testing
2. Leak testing of ductwork
3. After complete insulation

SAFETY

• Work will commence as per safety regulations laid down in the contract specification and project safety plan.
• Proper safety harness to be used and secured, if required
• All personal protective equipment shall be used as appropriate according to the nature of the job.
• Housekeeping shall be of good standard and all cut lengths and debris shall be removed.
• Good ventilation for ductwork insulation shall be ensured.

References:

MEP Planning Manual by Mr. Gulshan Kumar