Ducts of black and galvanized steel sheet hot-rolled (cold) in diameter or larger in size by up to 2000 mm inclusive. manufacture of spiral-palace or longitudinal seam on seam, spirally welded longitudinally to the welding, and air ducts having a diameter or size greater part of more than 2000 mm – panel (welded, kleesvarnymi). Ducts are made of metal-on rebate, and stainless steel, titanium and its alloys, aluminum sheet metal and its alloys – for welding or seam. Flexible ducts are made of aluminum and steel. In the manufacture of welded duct with a longitudinal eyelet must apply seam welding. Ducts are made of two classes: P – dense, N – normal. Sheet metal thickness of less than 1.5 mm should be welded lap, and a thickness of 1.5 to 2 mm – butt or lap. Sheet metal thicker than 2 mm must be welded back to back.

For welded joints straight sections and fittings ducts, which are produced from the black hot-rolled steel sheet (cold) and stainless steel, used The following welding methods: – plasma – automatic and semiautomatic arc submerged arc or inert gas – contact – roller – mma. For welding of air produced from sheet aluminum and its alloys, it should apply the following welding methods: – tig automatic – mag – tig manual – non-consumable electrode with the filler wire – gas. For welding ducts of titanium and its alloys are used argon-arc welding consumable electrode. Ducts made of sheet aluminum and its alloys with thickness up to 1.5 mm should be manufac-Lebanon in rebate. Longitudinal folds in ducts of sheet roof and stainless steel and aluminum sheet in diameter or larger size of 500 mm or more should be fixed at the beginning and end of the link duct spot welding, rivets.

Folds on air for any thickness of metal and method of manufacture must be satisfied cut-off. Folded seams must be the same width throughout the length and must be uniformly dense deposition. In the folded ducts, as well as nesting should not be cross-connections seams. On straight ducts of rectangular cross section when the amount of cross-section of more than 400 mm to increase the rigidity of the ridge should be performed increments from 200 to 300 mm along the perimeter of the duct or diagonal creases (ridges). When the amount of cross-section of more than 1000 mm, but it is necessary to provide external frame rigidity. Frame rigidity should be secured spot welding or rivets. Elements of the fittings should be connected to each other on zigah, rebate, welding, rivets and the way (indentation). Elements of fittings of metal-base should be connected between a rebate on. Zigovye connections to systems transporting air humidity or doped with combustible dust is not allowed.