1. The Straight Tee welding bead must be smooth, to achieve single-sided welding and double-sided forming, the interior must be polished smooth, no pores, and the folding edge of the folding surface should be flat (about 90°).

2. The part of the air duct to be painted (including the flange surface inside the pipe) must be sandblasted, the sandblasting roughness must meet the roughness of 3.0 G/S76, 40μm or more, and the residual sand particles and metal dust outside the pipe must be removed after sandblasting. Confirm whether the surface of the duct workpiece is clean and the workpiece is covered with aluminum foil.

3. Pull the pipe fittings into the coating room, start painting, spray with electrostatic powder coating machine and extended spray gun tube, adjust the sintering time moderately according to the characteristics of raw materials for 15~20 minutes, and the sintering temperature range is 285°~300°C.

4.100% total quality inspection (film thickness detection, pinhole detection), with film thickness tester to detect coating film thickness. The film thickness is 260±30 μm. A pinhole detector is used to detect whether the coating has pinholes. Adjust the standard detection voltage to 2.5KV, if there are needles that need to be repaired or reworked. The film thickness and pinhole test results after quality inspection should be recorded in the “Duct Coatung Quality Inspection Form”.

5. After the workpiece is completed, the outside of the tube is affixed with FM certification label, QC serial number and product specification label. The flange mouth is sealed with PE plate or PP hollow corrugated board, and fixed with plastic hose tape.

6.Duct diameter over 2000mm is available on request. Duct thickness is built on SMACNA. And it also can be changed as customer’s request.