15. Fabrication of duct using Polyvinyl Chloride Pipes. Measure the exact length of the pipe needed for installation. Cut the pipe using PVC pipe cutter. Branch lines and outlets shall be tapped to the main duct using PVC fitting or PVC welded. PVC solvent shall be applied for connections using PVC fittings. Inspect all connections and clean the surface of the pipe. Seal both ends prior to transport on site for installation.16. Installation of Air Ducts. Air Ducts shall be installed according to approved plan / lay-out. Any changes in plan / lay-out shall be approved by the Design Engineer. Prior to mounting of Air Ducts, hangers and support shall be provided. Main duct shall be tapped to the exhaust fan / air-conditioning unit using canvass cloth. Aluminum louvers with bird screen shall be provided for discharged duct of exhaust fan unit. Main and branch ducts shall be provided with galvanized iron volume dampers. Main and branch duct size shall be based on allowable air velocity. Allowable air velocity for main and branch duct shall be maintained at 5-10 meters per second and 3-5 meters per second respectively. (Divide the required flow rate in cubic meter per second by the allowable air velocity in meters per second to obtain the required cross-sectional area of duct in square meters). All joints and connections shall be provided with sealant or duct gasket. Newly installed duct shall be subjected to leak testing.

16. Hangers and Support Installation. Sufficient hangers and support for installed Mechanical Utilities (Pipes and Ducts). PVC pipe Air Ducts hangers shall conform to the requirements for pipe hangers. All hangers and support shall be attached to concrete walls, floor slab, or steel truss which is capable. Hangers for Duct and Pipe lines shall be in accordance to the standards. Requirements for Ducts and Pipe hangers are as follows:

a. Hangers and supports shall be painted with gray epoxy paint.

b. Leak Testing and Commissioning. Pipe lines for leak testing shall be isolated from the system through isolation valves by Facilities.

c. In case of vacuum lines, In-line the pipe line with the vacuum pump. Charge the pipe lines with applicable medium Compressed Air, Pressurized Water, and Special Gases) up to a pressure not less than the working pressure of the system.

d. Air ducts shall be tested for leaks by in-lining with the exhaust fan, supply fan or air-conditioning unit.

e. Inspect all joints. Soap solution maybe applied to the duct / pipe line (for leak testing using compressed air or special gases as medium) to locate the leaks. Leaks (if any) shall be immediately repaired. Repeat this procedure until all leaks are eliminated.

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