The manufacture and installation of air ducts shall be based on different specifications of construction drawings, and the unit of measurement shall be "m2" according to the developed area, without deducting the areas occupied by inspection holes, measuring holes, air supply openings and air suction openings.

Circular air duct

F

=

Pi?

×

D

×

L

In which: F—

Enlarged area of circular pipeline, m2;

D —

Diameter of circular air duct, m;

I-

Length of pipeline centerline, m

2.

The length of air duct shall be subject to the length of the center line in the construction drawing, including the length of elbow, tee joint, reducer, round place and other pipe fittings, but excluding the length of components (regulating valve, muffler, muffler elbow and static pressure box). The diameter and circumference are based on the dimensions shown in the figure, and the occlusal overlapping part has been included in the corresponding project and will not be added separately.

3.

The diameter listed in the manufacture and installation of plastic air duct and composite air duct is the inner diameter and the perimeter is the inner perimeter.

4.

The manufacture and installation of thin steel ventilation pipes, purification ventilation pipes, glass fiber reinforced plastic ventilation pipes and composite ventilation pipes have already included flanges, reinforcing frames and hangers, and are not counted separately.

5.

The manufacture and installation of stainless steel ventilation pipes, aluminum ventilation pipes and plastic ventilation pipes do not include hangers, which can be calculated separately according to the corresponding items with "kg" as the unit of measurement.

6.

When calculating the length of air duct, the main pipe and branch pipe are divided according to the intersection of their centerlines, the length of reducing pipe is calculated within the extended meter of large-diameter air duct, and the length of elbow is calculated according to the intersection of the centerlines of two air ducts.

7.

The installation of flexible flexible air duct is based on the length of the center line shown in the figure, and the unit of measurement is "m".

8.

The density of galvanized steel sheet is 1.05 times that of ordinary steel sheet.