Contents:
- Objective
- Scope
- References
- Material
- Material Procurement, Handling and Storage
- Duct Fabrication
- Duct Installation
- Duct Insulation
- Objective
This method statement provides information concerning the method of construction to ensure compliance with contract requirements, drawing, technical specification and quality control to provide a successful installation, testing, and commissioning of the of Black Steel Duct work.
- Scope
HAC shall supply and install in accordance with the specification of material and workmanship of black steel duct system.
HAC shall complete install works, testing, witness testing at the site by the engineer, testing and commissioning of the black steel duct system.
- References
- Contract Specifications.
- Material Submittal.
- Design Drawings.
- Shop Drawings.
- Latest edition of SMACNA Duct Construction Standards.
- Material
- Black steel duct.
- Thermal & grease sealer.
- Insulation.
- Galvanized supports & Accessories.
- Material Procurement, Handling and Storage
- Upon approval of the material and shop drawing submittals, Contractor shall survey the QTY including fittings as per approved shop drawing and fabricate the material as per project schedule.
- Upon delivery to site, all duct and accessories shall be stored indoor, in a clean, dry and ventilated place.
- Duct Fabrication
General:
- Ductwork sections shall be unloaded and stored in such a way to avoid damage and contamination.
- Duct shall be factory fabricated.
- Prepare approved shop drawing showing the size, Access Doors, fitting and transformation section of ducting.
- Duct sheet thickness is 3.4mm and Access Doors shall be of the same sheet thickness.
Methodology:
- Select the right thickness of material as per the constructional details.
- Steel sheet cutting shall be using electric cutter.
- Steel sheet bending shall be using hydraulic bending machine (L shape according to the approved shop drawing).
- Two Pieces of L-shape steel sheet welding shall be using Electric CO2 welding machine (Gas Shield Metal Arch. Welding using automatic feeding and CO2 as shield gas).
- Threaded openings in the flanges of sizes 5cm x 5cm x 5mm shall be made using drilling machine (as per submitted sample).
- Assembly of the boxes shall be using galvanized tighten bolts as per shop drawings.
- Grease and heat sealant shall be applied between any two assembled parts.
- No vanes or any dampers/splitters are allowed to be installed in the path of the duct.
- Duct Installation
General:
- Ductwork routing shall avoid undue changes of direction, sets or bends.
- The internal joints shall be arranged such that raw edges do not oppose the airflow.
- Duct hangers are fitted at correct setting and location.
- Support spacing shall be relevant sections of SMACNA Duct Construction Standards, as per note on IFC details drawings. Ductwork support material shall be galvanized.
- Select the fabricated duct section with correct dimension.
- Where space conditions permit, full radius turns shall be used.
- Where space conditions do not permit a short radius or square elbows shall be used.
- All installation work shall be carried-out per approved drawings.
Methodology:
- Based on the size of the ducts, two/three sections of the ducts are joined (as indicated in the shop drawing) on the floor as per layout drawing.
- Two adjoining duct section are jointed together with tighten bolts; grease and heat sealant is applied between the joints.
- Prior installation, ducts are cleaned internally.
- The assembled duct pieces are lifted, seated on to the hangers and leveled; slop shall be maintained in the direction of the hood.
- The open ends of the ducts are closed with polythene sheets to avoid ingress of dust.
- The installed duct length is then offered for inspection. After the inspection clearance the duct length is leakage tested.
- All Joints shall be inspected and checked for maximum leakage allowance.
- Duct Insulation
General:
- All materials shall be new and fully dried and must be maintained in this condition during the progress of the works.
- All insulating materials shall be proofed against rotting, mold, fungus growth and attack by vermin.
Methodology for Duct Insulation:
- Ensure surface of duct is dry and free from dust or grease.
- Wrap insulation, foil face up, to the prepared duct surface making sure that all edge joints are closely butted.
- Apply uniform hand pressure to outside surface of insulation to obtain good bond.
- Tape all longitudinal and transverse joints with a good quality self-adhesive insulation tape. Seal any puncture points in insulation around hangers etc. with tape.
lacing wire is used for additional security and light gauge galvanized angle should be fitted on each edge to prevent wire from cutting into insulation.
