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Duct Sheet Selection:

Basis: GB50243-2016 “Ventilation and Air Conditioning Engineering Construction Quality Acceptance Specification”.

4.1.4 The air duct system shall be divided into four categories of micro-pressure, low-pressure, medium-pressure and high-pressure according to its working pressure, and the air ducts of the corresponding categories shall be used. Duct category should be divided according to the provisions of Table 4.1.4.

4.2.3 The fabrication of metal air duct shall comply with the following provisions:

1 The material varieties, specifications, properties and thickness of metal air duct shall meet the design requirements. When there is no design requirement for the thickness of air duct, it shall be implemented according to this specification. Thickness of steel plate duct sheet shall conform to the provisions of Table 4.2.3-1. Galvanized steel galvanized layer thickness should be in accordance with the design or contract, when the design does not specify, should not be used less than ^80g/m2 plate; stainless steel plate duct plate thickness should be in accordance with the provisions of Table 4.2.3-2; aluminum plate duct plate thickness should be in accordance with the provisions of Table 4.2.3-3.

Clean duct should also require: rectangular duct side length less than or equal to 900mm, the bottom plate should not be splicing; greater than 900mm, there should be no horizontal splicing;

Splicing of air duct (angle steel flange):

The distance between the bolts and rivet holes of the duct flange of medium and low pressure system shall not be greater than 150mm; the duct of high pressure system shall not be greater than 100mm. rectangular duct flange shall be provided with screw holes at the corners.

2 metal duct connection shall comply with the following provisions:

1) The joints of duct sheet splicing shall be staggered, and there shall be no cross-shaped splicing joints.

2) The flange and bolt specifications of metal round duct shall conform to the provisions of Table 4.2.3-4, and the flange and bolt specifications of metal rectangular duct shall conform to the provisions of Table 4.2.3-5. Micro-pressure, low-pressure and medium-pressure system duct flange bolts and rivet holes in the hole distance shall not be greater than 150mm; high-pressure system duct shall not be greater than 100mm. rectangular duct flange corners should be provided with screw holes.

3) for medium pressure and the following pressure system air ducts of thin steel flange rectangular duct flange height, should be greater than or equal to the same metal flange duct flange height. Thin steel flange rectangular duct shall not be used for high pressure duct.
 

Figure 4.3.1 Reinforcement forms for metal ducts

2) Arrangement of fluting tendons (lines) should be regular, the interval should be uniform, the maximum spacing should be 300mm, the surface of the plate should be flat, concave and convex deformation (unevenness) should not be greater than 10mm.

3) Angle steel or steel plate folded into the height of the reinforcing bar should be less than or equal to the height of the flange of the duct, reinforcing arrangement should be neat and uniform. Riveting with the duct should be firm, the maximum interval should not be greater than 220mm; the intersection of each band, or the intersection of band and flange should be connected and fixed.

4) The fixing of pipe support and duct should be firm, and sealing measures should be taken at the wall of the pipe. The distance between each support point or support point and the edge of the duct or flange should be uniform, and should not be greater than 950mm.

5) When the length of the duct section of medium and high pressure system is more than 1250mm, reinforcement measures should be taken to strengthen the frame. High-pressure system duct single bite seam, should also be taken to prevent the bite seam expansion of the reinforcement or reinforcing measures.

Other requirements:

The nibble joints of air ducts and fittings should be tight and consistent in width; the folded corners should be straight and the arcs should be even; the two end surfaces should be parallel. There is no obvious twisting and warping of the duct; the surface should be flat and the concavity and convexity should not be more than 10mm.

The permissible deviation of the outer diameter or length of the duct is 2mm when it is less than or equal to 300mm and 3mm when it is greater than 300mm, the permissible deviation of the flatness of the duct opening is 2mm, and the difference between the two diagonal lengths of rectangular ducts should not be greater than 3mm; the difference between the diameters of any orthogonal two of the circular flanges should not be greater than 2mm.

Rectangular ducts connected by c, S-shaped inserts, the side length should not be greater than 630mm; inserts and duct processing socket width should match the same, the allowable deviation of 2mm; connection should be flat, tight, the two ends of the inserts should be pressed down length should not be less than 20mm;

Production requirements: the length of flexible short pipe, generally appropriate for 150 ~ 300mm, the connection should be tight, firm and reliable; flexible short pipe should not be used as a straightening, leveling reducer connecting pipe;

Set up in the structure of the deformation joints of the flexible short pipe, its length should be the width of the deformation joints plus 100mm and above;

The production material of flexible short pipe of smoke prevention and exhaust system must be non-combustible material.

Casing:

When the air duct passes through the fireproof and explosion-proof wall or floor that needs to be closed, there should be a pre-embedded pipe or protective casing, and the thickness of its steel plate should not be less than 1.6mm. between the air duct and the protective casing, it should be blocked with non-combustible and non-hazardous flexible materials.