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Round duct support rings are spaced, often at three diameters, or as require at up to about 50 ft centers (14 m). At this spacing the main support rings are designed for the sum of suction pressure stresses & support bending moments. Round ductwork allowable compressive stress is = 662 /(d/t) +339 * Fy (tubular steel structures, chapter 2).
The conduit may be coated to prevent corrosion by incidental contact with concrete. Aluminum conduit is generally lower cost than steel in addition to having a lower labor cost to install, since a length of aluminum conduit will have about one-third the weight of an equally-sized rigid steel conduit. [2]
In electric power distribution, a bus duct (also called busway) typically uses sheet metal, welded metal [1] or cast resin to contain and isolate copper or aluminium busbars for the purpose of conducting a substantial current of electricity. It is an alternative means of conducting electricity to power cables or cable bus.
Round duct is made using a continuous spiral forming machine which can make round duct in nearly any diameter when using the right forming die and to any length to suit, but the most common stock sizes range evenly from 4" to 24" (10-60 cm) with 6"-12" (15-30 cm) being most commonly used.
A pipe support or pipe hanger is a designed element that transfer the load from a pipe to the supporting structures. The load includes the weight of the pipe proper, the content that the pipe carries, all the pipe fittings attached to pipe, and the pipe covering such as insulation .
There are two means of providing fire-resistance rated ductwork: Inherently fire-resistant, or proprietary factory assembled ducts which are made of sheet metal shells filled with mixtures of rockwool, fiber and silicon dioxide
Control joints must have adequate depth and not exceed maximum spacing for them to be effective. Typical specifications for a four-inch-thick slab are: [8] 25% depth of material; spacing at 24 × to 36 × of slab depth (some specification call for a maximum of 30 ×) special care for inside corners
Rooftop HVAC unit with view of fresh-air intake vent Ventilation duct with outlet diffuser vent. These are installed throughout a building to move air in or out of rooms. In the middle is a damper to open and close the vent to allow more or less air to enter the space. The control circuit in a household HVAC installation.