Technical specification of air duct
1 General provisions
1.0.1 This specification is formulated with a view to standardize the fabrication, installation, inspection and test methods of air ducts, to ensure safety and applicability, advanced technology, cost effectiveness, rationality and convenience for construction, and to assure a good engineering quality.
1.0.2 This specification is applicable to the fabrication and installation of metal or nonmetallic ducts used for ventilation and air conditioning works for newly constructed, expanded and renovated industrial and civil buildings (referred to as “air ducts”).
1.0.3 In addition to this specification, the technical and quality requirements for the fabrication and installation of air ducts shall also meet the requirements of the current relevant compulsory standards of the nation.
2 General requirements
2.0.1 The air ducts shall be fabricated and installed in accordance with the design drawings, contracts and relevant technical standards. In case of any change, there shall be a notice of design or contract change or a technical approval verification.
2.0.2 Before the construction of the air duct system, the construction unit shall coordinate with the development unit, supervision unit, EPC and design units about the position and direction of the air duct and other pipelines, and check the holes reserved for installation, etc. During the construction, the construction unit shall cooperate with personnel of civil engineering and other professional work.
2.0.3 Sheets, profiles and other main finished materials for fabrication and installation of air ducts shall meet the requirements of the current national standards for design and related products, and shall be provided with the ex-factory inspection certificates. During approaching, materials shall be checked and accepted according to the current relevant national standards.
2.0.4 Air ducts supplied as finished products shall be provided with corresponding qualification certificates, including quality certificate of main material, strength and leakage test reports of air duct (nonmetallic air ducts shall also be provided with fire protection and health test certification reports). The performance test methods of air ducts supplied as finished products shall meet the requirements of Annex A to this specification.
2.0.5 Energy-saving, high-efficiency and mechanically processing technology should be preferred for air duct fabrication.
2.0.6 The measuring and testing instruments for the fabrication and installation of air ducts shall be in a conforming state and within the effective inspection period.
2.0.7 Air ducts of concealed works shall be checked, accepted and approved by the supervisor before concealment.
2.0.8 After the installation of air duct system, the leakage test shall be carried out by the system category, with a test method specified in the Annex B to this specification.
2.0.9 Air duct system may be classified into the following three categories according to its working pressure (P):
1 Low pressure system with P≤500Pa;
2 Medium pressure system with 500Pa
1500Pa.
2.0.10 Outside length (or outside diameter) should be the designated dimension for metal air ducts, and inside length (or inside diameter) should be the designated dimension for nonmetallic air ducts. Common specifications of side length of rectangular air duct shall meet those specified in Table 2.0.10-1, and the ratio of long side to short side shall not be greater than 4:1. Specifications of circular air ducts shall meet those specified in Table 2.0.10-2, and the basic series are preferred.
Table 2.0.10-1 Common specifications of rectangular air ducts (mm)
Side length of air duct
120 320 800 2000 4000
160 400 1000 2500 -
200 500 1250 3000 -
250 630 1600 3500 -
Table 2.0.10-2 Specifications of circular air ducts (mm)
3 Air duct fabrication
3.1 General requirements
3.1.1 Metal sheets shall meet the following requirements:
1 The steel sheets shall be flat and smooth in surface, uniform in thickness, and free from defects such as cracks and scars, whose material shall conform to the current national standard GB 13237 Cold-rolled quality carbon structural steel sheets and strips or GB 710 Hot-rolled quality carbon structural steel sheets and strips.
2 Galvanized steel sheets (strips) should be mechanically engaged, and the galvanized coating is made of material above 100# (the mean of three-point test on both sides shall not be less than 100g/m2), and the material shall meet the requirements of the current national standard GB 2518 Continuous hot-dip zinc-coated steel sheets and strips.
3 Austenitic stainless steel shall be used for stainless steel sheet, whose surface shall be free from obvious defects such as scratches, scuffing, spots and pits, and whose material shall meet the requirements of the current national standard GB 3280 Cold rolled stainless steel sheets and plates.
4 The aluminium sheet shall be pure aluminium sheet or rust-proof aluminium alloy sheet, whose surface shall be free from obvious defects such as scratches, scuffing, spots and pits and whose material shall conform to the current national standard GB/T 3880 Aluminium and aluminium alloy rolled sheet.
3.1.2 Metal structural steels shall meet the requirements of the current national standards GB 9787 Hot-rolled equal-leg angle steel — Dimensions, shape, weight and tolerances, GB 704 Dimensions, shape, weight and tolerances for hot-rolled flats, GB 707 Hot-rolled channel steel — Dimensions, shape, weight and tolerances, GB 702 Hot-rolled round and square steel bars — Dimension, shape, weight and tolerance respectively.
3.1.3 The material for nonmetallic air ducts shall meet the following requirements:
1 The combustion performance of nonmetallic air duct materials shall meet the requirements of incombustible grade A or flame retardant grade B1 in the current national standard GB 8624 Classification for burning behavior of building materials and products.
2 The surface aluminium foil material of composite material shall meet the requirements of the current national standard GB 3198 Aluminium foil for general purpose, and its thickness shall not be less than 0.06mm. When the aluminium foil layer is compounded with reinforcing materials, its thickness shall not be less than 0.012mm.
3 The composite layer of composite plate shall be securely bonded. Defects such as delamination and collapse on one side of the outer surface of the plate shall not exceed 6‰, and the internal insulation materials shall not be exposed.
4 The combustion performance of aluminium foil heat-sensitive, pressure-sensitive tapes and adhesives shall meet the flame retardant grade B1 and shall be used within the service life. The adhesives shall match the material for air duct and meet the requirements of environmental protection.
5 The width of aluminium foil pressure-sensitive and heat-sensitive tapes shall not be less than 50mm. The thickness of aluminium foil shall not be less than 0.045mm. The 180° peeling strength of aluminium foil pressure-sensitive sealing tape shall not be lower than 0.52N/mm.
The ironing surface of aluminium foil heat-sensitive tape shall have a temperature-sensitive color point, and the color changes when heated to 150°C. In the 180° peeling strength test of heat-sensitive sealing tape, the peeling strength shall not be lower than 0.68N/mm.
6 Unplasticized polyvinyl chloride (PVC-U) plates shall meet the requirements of the current national standards GB/T 4454 Rigid polyvinyl chloride laminated plates or GB/T 13520 Unplasticized polyvinyl chloride extruded plates. The combustion performance of the plates shall be flame retardant grade B1. PVC-U plates shall be free from defects such as bubbles, delamination, carbonization, deformation and cracks.
7 Technical parameters and applicable scope of nonmetallic air duct sheets shall meet those specified in Table 3.1.3.
