- PURPOSE
- SCOPE
- REFERENCE
- EXECUTION PROCEDURE
- SAFETY ASPECT
1.0 PURPOSE:
Purpose of ducting is done in order to cool the required air in the building (SUB STATION) through which required quantity of air flow will flow, and the insulation is being done on the supply duct in order to avoid
the heat transfer from the cool air flow through the duct which is directly in the open atmosphere in order to avoid the condensation.
2.0 DUCT INSTALLATION AND INSULATION METHOD STATEMENT:
This document covers the requirements and procedures for installation of HVAC system. And to ensure that the work is performed in accordance with the Project Specifications and IFC drawings and SAES code, HVAC design specifications, SMACNA, NEFA90A, UMC, Schedule-Q, Quality requirements, SATIP, SAEP, SAIC, SATR, ASHRAE, ASTM, SAMSS etc.
3.0 REFERENCES:
ASHRAE American Society of Heating and Refrigeration Association Of Engineers
HVAC Heating, Ventilation and Air Conditioning
NFPA National Fire Protection Association
SMACNA Sheet Metal Air Conditioning Contractors National Association
UMC Uniform Mechanical Code
ANSI American National Standards Institute
AMCA Air Movement & Control Association International
ASTM American Society for Testing & Materials
ASME American Society of Mechanical Engineers
AABC Associated Air Balance Council
SAMSS Saudi Aramco Materials System Specification
SATIP Saudi Aramco Typical Inspection Plan
Materials
• Galvanized Zinc. coating Iron Sheets
• Duct Sealant.
• Angles and supports
• Scaffolding
• Hardware
• Insulation Materials
• Aluminum Cladding
• Accessories as per approved I FC drawings.
Manpower
• Site Engineers
• QC inspector
• Safety Officer
• Supervisors
• Technicians
• Labor
4.0 DUCT INSTALLATION AND INSULATION PROCEDURE
4.1 DUCT HANGERS AND SUPPORT INSTALLATION
1) Supports for Rectangular ducts when suspended from above shall be installed on two opposite side of each duct.
2) Supports for Rectangular ducts shall be riveted, bolted, or metal screwed to each side of the duct at not more than the intervals specified.
3) Duct must be supported at each change of direction.
4) Hanger spacing not to be exceed 8 ft. (2.5 Mt) as per SMACNA Standard.
5) The support system shall not cause corrosion by galvanic action at points of contact with the duct.
6) Concrete fasteners shall be installed after the concrete has been poured and the forms have been removed.
7) The support system shall not penetrate enclosures containing fluids or electrical wiring in such a manner to create a hazard.
8) Horizontal duct shall have a support within the feet of each elbow and within 4 feet of each branch intersection.
9) When ducts are supported from wall they shall be located against the wall or maximum of 2″ away from wall.
10) The supports system shall not penetrate a bearing member in such a manner as to cause excessive loading on the member.
11) Circular bands shall not be less than one-inch-wide nor less than equivalent to the gauge of the duct material does it support.
12) Ducts shall be equipped with tight circular bands extending around the entire perimeter of the duct at each specified support interval.
13) Fastener (for supporting ducts from wall) shall be located within 1″ of the duct edge (wall side) and within 2″ of the duct outer edge. Minimum of 3 on 24″ width and up is required in addition to ones from edges.
14) Rectangular duct risers from floor shall be supported by angles or channels secured to the sides of duct with welds, bolts, sheet metal screws, or blind rivets. Fasteners shall be located within 2″ of the duct edges, locate others at evenly spaced interval.
15) Angles shall be at 12 feet intervals for rectangular and round duct risers.
16) AII duct hanger & supports details shall be according to the drawing.
4.2 DUCT INSTALLATION
1) Duct Work shall be installed in accordance with approved General Construction
Drawings, Specifications, and Manufacturer’s Installation Manual.
2) Prior to install make sure duct are properly clean both side in and out
3) Rectangular elbows shall be provided with Turning Vanes.
Note: For low velocity systems only.
Exception: No turning vanes required if the throat radius is equal to the duct width.
4) Ducts shall be isolated from their Air Handling System (Fan, Fan Coil, AHU’s, etc) by Flexible Connections. Flexible Duct Connected shall not exceed 8 feet in overall length and shall not have bends greater than 30 degrees.
5) Splitter dampers shall not be used for duct branch take-offs.
6) All building exhausts shall be directly to the outside with a point of discharge of at least 1.5 m away from any open able window or door, and a minimum of 1 m above and 3 m horizontally away from any air intake.
7) Metal ducting shall be grounded, provide jumpers at flexible duct.
8) Metal Ducts shall be installed at least 100 mm from Ground level
9) Joints, seams and fittings of duct systems shall be made substantially airtight by means of tapes, mastic, gasket or other approved methods.
10) If air leakages in ducts located outside of buildings are exposed to weather, they shall receive exterior duct sealant.
11)Exterior ducts sealant if exposed to direct sunlight shall be ultraviolet ray and ozone resistant or shall be painted with a compatible coating that provides such resistant (SMACNA Para S1 .9 g).
12) Seal class C shall be provided for 2″ w.g. pressure class duct Construction. Class C: Transverse joints only
13) Installation of duct shall be done with proper alignment.
14) All duct work shall comply with SMACNA standards suitable for 2″ w.g. pressure class.
15) All duct passing through the wall shall be provided with duct sleeve as per SMACNA and Aramco standards.
16) All duct opening shall be covered with plastic material to avoid dust infiltration to internal part of the duct.
17) Combustible materials located inside the duct and ceiling (if any) shall be discarded and completely removed as per NFPA-90A requirements
18) Metal corner bends shall be provided with aluminum strap (1-inch width) to all insulated AC ductworks.
19) Turning vanes shall be provided in all rectangular elbows of low velocity systems as per SMACNA HVAC Duct construction standards.
20) All duct penetrations to the wall shall be sealed with Aramco approved fire stop sealant an NFPA -90A complaint.
21) TAB (Testing, adjusting and balancing) shall be conducted and carried out by HVAC contractor or third party TAB contractor approved by Aramco.
Material Specifications: Material Confirms to: ASTM A653
Material: Galvanized Iron sheets, Zinc Coating: G-90
Thickness: As per General Construction Drawings.
4.3 DUCT INSULATION:
1) Duct joints shall be sealed prior to insulation.
2) Duct Surface to be cleaned properly before applying adhesive.
3) Mechanical fasteners, adhesive, tapes, metal straps or any other means at the intervals specified in the construction drawings or specification shall be used in the installation of the duct insulation.
4) Duct insulation (For supply and return air ducts only) shall be done on the installed duct by leaving 50mm on both sides of duct and shall be erected. After installation of ducts and proper alignment, duct joints shall be sealed and insulated properly.
5) Insulation applied to the exterior surface of ducts located in buildings shall have a flame spread index of not more than 25 and a smoke density index not exceeding 50 when tested as a composite installation including insulation, facing material, tapes and adhesive as normally applied.
6) Ducts shall be insulated in accordance with ARAMCO STANDARDS.
7) All Supply air ducts, located indoors or exposed to unconditioned air shall be insulated with 25 mm thick 48 kg/m3.
8) Aluminum sheet jacketing of 0.4 mm thick comply with ASTM B209m for the outdoor exposed ducts will be done.
9) Pin fastener’s spacing or interval of 200-300 mm not more than 20 from the duct corner will fixed.
10) All sealant shall be NFPA-90A complaint, a non-combustible type with zero flammability and shall be Aramco approved.
4.4 FLEXIBLE DUCTS:
1) Flexible ducts shall be installed in accordance with SMACNA standard.
2) The bends of the flexible ducts shall not exceed 45 Degrees.
3) The length of the flexible duct shall not exceed 1.5 meters.
4) The flexible ducts shall be supported every 1.5 meters (max.) to avoid it from sagging and touching the false ceiling.
5) Fire damper should be approved with fiber glass blanket wrapping and corrugated aluminum type sleeve.
4.5 GRILLS AND DIFFUSERS:
1) Grills and diffusers shall be installed to distribute the amount of air in every room. Refer to approved Standard detail drawing.
2) Grills and registers shall be installed with self-tapping screws to the wall or to the ducts as per shop drawings.
3) Supply grills or registers shall be installed with volume dampers easily adjustable from the front.
4) Return grills or registers shall be installed with deflectors and volume dampers. The type of the diffusers shall be in accordance with the false ceiling.
5) Supply ceiling diffusers shall be installed with deflectors and volume dampers. The type of the diffusers shall be in accordance with the false ceiling.
6) Return ceiling diffusers shall be installed without volume dampers, and it shall be the same model with the supply diffusers. If the return diffusers are not the same with supply, the size and model shall be as specified in the shop drawings.
7) Air Terminal Devices shall be mounted at locations shown on approved Construction Drawings.
8) Air terminal devices shall not be installed directly on the main ducts.
4.6 SMOKE & FIRE DAMPERS:
1) The fire dampers shall be installed in accordance with manufacturer’s recommendation.
2) AII fire dampers must have fire ratings of 165 F. During off position the curtains shall be out of air stream so that it will not block the air stream.
3) Access doors shall be standard sizes and opening shall be provided on each fire to reach the blade in order to reset the fire damper after it is activated. Refer to approved standard detail drawings.
4) The location of the fire dampers shall be as specified in the approved shop drawings.
5) Type of duct connection to Fire Damper sleeve shall be breakaway connection.
6) Adequate space / opening is provided for restoring the damper (when done manually) in its normal operating condition.
7) Retaining angle shall be secured to sleeve on 8″ centers. Retaining angles shall not be fixed to the walls.
8) Fire/ Smoke Dampers shall bear a label from a recognized by testing laboratory (such as UL) or be tested in accordance with the requirements of Project Specification.
9) Clearance of the damper sleeves within a wall shall be 1/8″ per linear foot.
10) Length of the sleeve extending beyond the wall or floor opening shall be six inches on one side and sixteen inches on the opposite side.
11) All fire rated walls shall be provided with combination type motorized fire and smoke dampers or Fire dampers as per SMACNA and Aramco standards requirements, codes etc.
12) Combination type motorized fire and smoke dampers to be installed shall be UL listed, UL 555 /UL555S and shall be installed in all fire rated walls.
13) All motor actuators of motorized fire and smoke dampers, motorized volume dampers and motorized gas tight dampers shall be UL listed.
14) For flashing, retaining angle frame fixing & fire sealant work refer the attached approved sketch as per site condition.
4.7 VOLUME DAMPERS & BACK DRAFT DAMPERS INSTALLATION:
4.7.1 VOLUME DAMPERS
1) All volume dampers shall be installed in accordance with SMACNA standard and HVAC IFC drawings.
2) Multi blade dampers shall be used on ducts sizes more than 12″ depth, the blades must be opposed type.
3) All volume dampers operated manually shall have a handle which can be lock to a certain setting.
4) All volume dampers operated by motors shall have an extended shaft for the installation of the actuators/motors.
5) Branch duct dampers shall be sheet metal butterfly type, using pivot and rod, with locking quadrant damper/opposite blade type.
4.7.2 FRESH AIR STACK:
1.) Fresh Air Stack unit shall be installed in accordance with approved IFC drawings.
2.) Location, orientation, elevation and conditions of AIR Stack conformed with Approved drawings.
3.) All Air Stack units shall be installed on substantial concrete foundation or as Specified in approved shop drawing.
4.) Installed sand trap Louvers are from the approved manufacturer and vendor with wire mesh or bird screen.
5.) Air Stack & Components (including Coatings) are free of damage. Any damages are identified for Corrective & Preventive Action as required.
4.7.3 BACK DRAFT DAMPERS:
1) All back draft dampers shall have a parallel blades linked to each other.
2) The installation of the back draft damper should be checked so that the blades are free from obstructions and that it opens on the flow of air. Or closed by the pressure building on the opposite side.
3) Gravity back draft dampers are closed down ward, the length of the blades shall be free from any obstruction so that the blades will return when there is no air flow.
4) If the back draft damper is placed horizontally so that it will open down ward, the damper shall have a counter weight to enable the damper to close on no flow position.
5) The location of the back draft dampers shall be as specified in the approved shop drawings.
4.8 LIGHT TEST:
1) LIGHT TEST: Light test shall be performed in sections prior to insulation (if required by the client). There is no need to verify leakage control by field testing when adequate methods of assembly and sealing are used. Leakage tests are an added expense in system installation. It is not recommended that duct systems constructed to 3 in. wg (750 Pa) class or lower be tested because this is generally not cost effective (SMACNA).
2) In case of requirement, the Light test shall be performed with heavy duty halogen lamps (500 or 1000 Watts lamps), which will located inside the ducting and the leakage in the ducts shall be traced and sealed properly with the sealant.
5.0 SAFETY
5.1 GUIDELINES: Person working on ducting erection work shall wear the required personal Protective equipment’s (PPE) at all times on the job site. Warning sign boards “Ducting erection ongoing keep away” and light for nights working shall be provided wherever necessary.
5.2 RESPONSIBILITIES: Safety Inspector/Officer in conjunction with the Site Supervisor or Foreman shall physically check and conform that all safety requirements had been provided and implemented.
5.3 JOB HAZARD ANALYSIS: