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Air duct classification and system composition-2
I. Reinforcement measures for air ducts. Reinforcement measures should be taken for metal air ducts that meet the following conditions:
(1) The diameter of the circular air duct is greater than or equal to 800mm, the diameter of the spiral air duct is greater than or equal to 1000nmm, and the length of the pipe section is greater than 1250mm or the total surface area is greater than 4m2.
(2) The side length of the low-pressure rectangular air duct is greater than 630mm or the side length of the rectangular thermal insulation air duct is greater than 800mm, the length of the pipe section is greater than 1250mm or the unilateral area is greater than 1.2m2, and the unilateral area of the medium and high pressure duct is greater than 1.0m2.
(3) Corresponding reinforcement measures shall be taken for the air duct according to its working pressure level, plate thickness, air duct length and section size. The air duct can be reinforced in the form of inner or outer pipe reinforcements, pipe wall pressing reinforcement ribs, etc. Rectangular air duct reinforcements should be made of angle steel, light steel profiles or folded steel plates; circular air duct reinforcements should be made of angle steel.
(4) The inner oblique line and inner arc elbow of the rectangle should be provided with guide vanes to reduce the local resistance and noise of the air duct.
(5) The material selected for the production of the muffler of the pipeline should meet the design requirements, such as fireproof, moisture-proof, anti-corrosion and sanitary performance requirements, the shell should be firm and tight, and the filled muffler material should be laid uniformly according to the specified density.
Ⅱ. Main points of installation of air duct system
1. Check the air duct before installation. The debris in the installation site or operation site should be cleaned up, and the production quality of the air duct and its accessories, the production and installation quality of the air duct support and the hanger should be checked.
For example, the section steel and its screw holes for cutting off supports, hangers and brackets should be machined and not cut by electric welding; supports and hangers should not be set at the air outlet, valve, inspection door and automatic control device.
2. The pairing and connection length of the air ducts should be determined according to the conditions of the construction site and the hoisting equipment. The sealing material used for the air duct connection shall meet the technical conditions of the system function.
For example, for smoke prevention and exhaust system or for conveying air or flue gas with a temperature higher than 70°C, heat-resistant rubber sheets or non-combustible temperature-resistant and fire-resistant materials should be used; when conveying gas containing corrosive medium, acid-resistant rubber sheet or soft polyvinyl chloride sheet should be used.
3. The procedure of installing the air duct in place is usually the upper layer and then the lower layer, the main pipe first and then the branch pipe, and the riser first and then the horizontal pipe. When in place, attention should be paid. For example, when using a hoisting group for the air duct, the protection of the surface should be strengthened, and attention should be paid to the center of gravity of the lifting point to ensure that the hoisting is stable and safe and that the air duct will not be twisted or bent. If necessary, measures to prevent deformation should be taken.
4. Measures taken when the air duct passes through the fire-proof and explosion-proof floor or wall that needs to be closed. A pre-managing pipe or protective casing with a steel plate thickness of not less than 16m shall be provided, and non-combustible flexible materials shall be used to block the air duct and the protective casing. When the air duct passes through the space of the deformation joint of the building, a flexible short pipe should be installed. When the air duct passes through the wall of the deformation joint of the building, a steel sleeve should be installed, and the flexible waterproof material should be used to fill the space between the air duct and the sleeve.
5. A reliable anti-static grounding device must be set for air duct systems that contain flammable and explosive gases or are installed in flammable and explosive environments; No interface shall be set in other auxiliary production rooms. The installation direction of the wind room should be correct, easy to operate, and flexible to open and close. Separate supports and hangers should be provided for elbows and three wines whose side length (diameter) is greater than or greater than 630m in the fireproof country or whose side length (diameter) is 50m larger.
6. When installing the muffler and the static pressure box, the support and hanger should be set up separately and fixed firmly.
Ⅲ. Inspection and testing of air ducts
1 Before mass production of air ducts, the strength and tightness test of air ducts should be carried out when inspecting the air duct manufacturing process.
2. After the installation of the air duct system is completed, the tightness test shall be carried out on the main and dry air duct sections after installation. After the installation of the air duct system, the tightness inspection must be carried out, mainly to inspect the seaming joint, riveting hole, flange flanging of the air duct and the connection tightness between the air duct sections after the duct fabrication and processing of the air duct and components. The main and main pipes are mainly inspected, and can be delivered to the next process only after passing the inspection.
Ⅳ. Anti-corrosion and heat insulation of air ducts
1. Before anti-corrosion construction, the metal surface should be derusted and cleaned. Manual rust removal or sandblasting can be used. Sandblasting and rust removal should be carried out in a workshop with ash removal conditions. The thickness of the anti-corrosion coating is uniform, the color is consistent, and the coating is closely combined with the metal surface.
2. The air duct insulation material and other auxiliary materials should be environmentally friendly products. The air duct insulation is fixed or bonded by means of insulation nails according to the different insulation materials. The thermal insulation of the air duct components shall not affect the operation function, and the thermal insulation of the regulating valve shall retain the position of the regulating handle to ensure flexible and convenient operation. Flanges, valves, filters and inspection points that are often disassembled on the air duct system adopt a separately disassembled thermal insulation structure.
Ⅴ. Operation and debugging of air duct system
1. The process flow of ventilation and air-conditioning engineering debugging
Organize on-site commissioning team → commissioning preparation and on-site survey → various inspections before system commissioning → measurement and adjustment of air volume and water volume of the system → single unit test operation and adjustment of ventilation and air conditioning system equipment → building and fire control system related equipment inspection → air conditioning and ventilation Individual equipment automatic control debugging → air conditioning and ventilation, smoke prevention and exhaust system automatic control linkage debugging → system no production load joint trial operation and debugging → data sorting and handover.
2. The main content of system debugging
Air volume measurement and adjustment, stand-alone test run, system no production load joint test run and debugging. The normal combined trial operation of the air-conditioning duct system with cold (heat) source shall be determined according to the slope construction season and design conditions.
For example, the test run with cold source can only be done in summer, and the test run with heat source can only be done in winter. After the construction unit has passed the joint trial operation and commissioning of the system without production load, it can enter the completion acceptance.
3. Comprehensive performance test and adjustment of ventilation and air-conditioning engineering with production load
It should be carried out under the conditions of production trial operation, the construction unit is responsible, and the design and construction units cooperate. Items that should be comprehensively measured and adjusted in the strip efficiency test that has been in production trial operation should be determined by the construction unit according to the requirements of the project nature and production process.
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