General provisions for PP air valve and branch air hose and exhaust air of branch air hose:

1. General provisions:

Before making the galvanized line air valve and the branch air hose for air exhaust, first check whether the materials used meet the quality requirements, and whether there are factory certificates or quality identification documents. In the absence of the above supporting documents, visual inspection shall be carried out and the following requirements shall be met:

(1) The surface of the plate should be flat, the thickness should be uniform, and there should be no convex concave and obvious crushing, and there should be no cracks, sand holes, scars, burrs and rust;

(2) The profile steel shall be uniform and uniform, free of cracks, bubbles, cavities and other defects affecting quality;

(3) Other materials shall not reduce the strength of finished products or affect their use efficiency due to defects.

2. The surface of air duct and accessories shall be flat, the arc shall be uniform, and the longitudinal joints shall be staggered; The seaming seam shall be tight and uniform in width. The welds shall be visually inspected and free of defects such as pores, sand holes, slag inclusions and cracks. The deformation of the steel plate after welding shall be corrected.

3. When making metal air ducts and fittings, the allowable deviation of outer diameter or outer edge length is - 1mm if it is less than or equal to 300mm; If it is greater than 300 mm, it is － 2 mm. The allowable deviation of the inner diameter of the circular flange or the inner dimension of the rectangular flange when making the flange is+2mm, and the unevenness shall not be greater than 2mm.

4. All right angle turns in the air duct system are equipped with silencing elbows, and galvanized iron plate deflectors are set inside the silencing elbows.

5. The insulation layer of the air duct is made of polystyrene foam board with density of 40kg/m3 and thickness of 35mm (surface temperature shall not be lower than 5 ℃). The junction part of the insulation layer edge adopts ladder or mortise structure and is pasted with resin. The outer surface shall be wrapped with aluminum foil cloth and tightly pasted with thermal tape. The outer surface of the air duct shall be free of condensation.