Smacna Duct Construction Standards

Standard Subscriptions

SMACNA Sheet Metal and Air Conditioning Contractors National Association

Rectangular risers should be supported by angles or channels secured to the sides of the duct with welds, bolts, sheet metal screws, or blind rivets. Test only the component being substituted or test the component plus any connected components in a manner that will simulate the actual loading and will correlate with actual performance. They may be zinc or cadmium coated. The lower attachment is the connection between the hanger and the duct section.

The double-wall style of lined duct is used where increased resistance to damage is desired or where erosion of the inner surface might occur. Complete and definitive testing in these three problem areas was not practical under the financial and time limitations of this program. Any round duct fitting can have an equivalent fitting made in flat oval.

It may be only six months or one year. It was possible to take vibration readings of the various specimens and system components.

They are generally known as the peel and seal variety and have been used between flanges and on the exterior of ducts. Ships with Tracking Number! It was observed that in general, cross breaking was not beneficial to high velocity duct performances. It concluded that the structural behavior of duct is reasonably predictable in terms of pressure, deflection, metal thickness, and stiffener spacing. Double-wall rigid round duct is available from several industry sources.

Spiral flat oval duct is machine-made from round spiral lockseam duct and is available in varying sizes and aspect ratios. Many manufacturers produce liquid sealants specifically for ducts. It is presumed that project specifications define the specific materials, pressure limits, velocity limits, friction rate, thermal conductivity, acoustical ratings, mahjong for android tablet and other attributes.

HVAC Duct Construction Standards - Metal and Flexible

Follow construction details for steel construction standards unless they are superseded by data on this page or by other considerations pertinent to aluminum. Each specimen normally included two transverse joints.

Attach supports with a minimum number of duct penetrations. Then it discharged into a plenum with an outlet damper.

However, the fan and damper controls must be carefully coordinated so that it is impossible for such a negative pressure condition to occur. This document or publication is prepared for voluntary acceptance and use within the limitations of application defined herein, and otherwise as those adopting it or applying it deem appropriate. Depending on the type of fastener, discoloration or dimpling may be evident when fasteners are properly attached to the sheet metal.

Why would a light gage sheet resist vibration more than a heavy gage sheet, and why would a sheet vibrate more at lower pressures? Additional measurements were made concerning the relative noise intensity as a function of sheet gage and static pressure. Blind rivets using pull-through mandrels are not permitted if they leave holes for air leakage.

Create a Want BookSleuth Can't remember the title or the author of a book? Hammer longitudinal seam at ends of standing seam. If this Kpa load is not in excess of one in Table M for a listed length that is also not exceeded, the size is acceptable.

In considering such requests, the Association will not review or judge products or components as being in compliance with the document or publication. Use instrumentation and follow procedures that will produce laboratory accuracy. Velocity in duct mains and branches can be at constant high or low or varying levels.

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There are so many possible variations of the double-wall casing construction that it is impractical to detail them in this manual. For each width of duct, the sheet gage, reinforcing size, and reinforcing spacing were varied in order to determine the lowest cost construction that would perform within the standards. Figures in this manual show typical hanger constructions. So-called safety standards may involve tests that report various characteristics but do not meet up to a hazard classification under installed conditions.

They also require intermediate hangers to prevent the upper portion of the duct from sagging. This is generally acceptable because the substituted element will exceed the minimum requirements.

HVAC Duct Construction Standards

Tapes of a gum-like consistency with one or two removable waxed liners have become popular for some applications. Ribbed forms of round duct are not yet standardized, but may be considered under equivalent-performance-alternative provisions. The Portland Cement Association has guidelines for protection of metals in contact with concrete. Otherwise, if the bar or angle must be aluminum, change the thickness and dimensions as necessary to accommodate the aluminum extrusions. Information on air flow pressure loss standard stock sizes, strength, corrosion, comparative cost and much other data on perforated metals is available from the Industrial Perforators Association.

Duct Construction Used