Smacna 1143 Pdf

Conduct tests in the positive or negative mode of pressurization, as desired. Instead it was decided to arbitrarily establish minimum threshold velocities for various static pressures.

Sheet Metal is an introduction to the fundamentals of layout, cutting, forming, and fabrication of sheet metal. The sheet must resist both deflection caused by internal pressure and vibration due to turbulent air flow. However, other limits may be acceptable if they can be shown to result in equivalent construction. In the event that the petitioner has a substantive disagreement with the interpretation, an appeal may be filed with the Technical Resources Committee which has technical oversight responsibility.



The greater duct dimension must be on the top, not on the side. Any further use in part or in whole requires permission.

Some may have mesh reinforcement. Suggestions for future improvement are welcome. After waiting enough time to achieve adequate bond strength which will vary, depending on the air temperature-impale the duct liner on the pin and add the spring clip or washer. In any multiple hanger system, the failure of one hanger transfers that its load to adjacent hangers.

If a contractor wants to fabricate this type of casing, it is suggested that strength of the panels be determined by structural calculations or pressure tests on mock-ups. This is the modulus of elasticity multiplied by a moment of inertia that is based on the contributing elements of the connector, the reinforcement, the duct wall, or combinations of these. Such internal supports should be illustrated on the contract drawings.

The new edition also includes a historic architectural sheet metal. The hot melt type is normally a shop application. In theory, the tapered casings conserve energy and facilitate uniform air distribution. Use instrumentation and follow procedures that will produce laboratory accuracy.


If more than one tie is used, the load is proportional. Double-wall rigid round duct is available from several industry sources. Each size in a pressure class has a minimum duct wall thickness and a minimum specification for joints, reinforcements, etc. Fasten the bar stock to the connector at ends and intermediate positions.

Very large ducts may require internal hangers as shown in Figure or may require other internal supports to provide shape retention. This assumes that threaded connections carry the load. Fasteners used on steel duct shall be steel. Pitch pockets require periodic maintenance and are not permanently watertight.

HVAC Duct Construction Standards

However, as a practical matter, the tapers required for ideal expansion or contraction are such that there is seldom enough space to accommodate them in typical equipment rooms. Furthermore, the ability of a reinforcing member to perform its function is critically affected by the location and adequacy of its attachment to the duct. First investigate the duct side with the greater dimension because this side dictates the duct gage. Surface primers are now available, but their additional cost may not result in measurable long-term benefits. Both modes are accepted when neither is given.

Where vibration isolation material is required at the connection of ducts to equipment, such material should be impervious to water. They are generally known as the peel and seal variety and have been used between flanges and on the exterior of ducts. On this basis, they unanimously agreed that the maximum amplitude of vibration established as a standard was well within the limits of vibration considered acceptable.

HVAC Duct Construction Standards

Piping systems manual by Saravanapavan Gowripalan smacna issuu. Sheet Metal is an introduction smacna the fundamentals of layout, cutting, forming, utah voter registration form pdf and fabrication of sheet metal. Piping Smacna Manual Brian Silowash. Circles in the Table denotes only column numbers.

HVAC Air Duct Leakage Test Manual

Openings in roofs require coordination of the architectural, structural, mechanical, and electrical contract drawings. Such detail now sets forth material, wall thickness, and joint construction, among other features. Roof penetrations by ducts should have curbs.


The duct hanging system is composed of three elements, the upper attachment to the building, the hanger itself, and the lower attachment to the duct. Nothing in this document implies an obligation to provide volume control devices that are not on the contract drawings. Ducts that are of heavier gage, smaller dimensions, and smaller panel area and those that are lined or externally insulated are not required to have crossbreaking or beading. The arrow indicates that the right most value continues to the end of the row because the minimum duct gage and reinforcement grade remain the same for shorter spacings.

Solvent cleaning is an additional expense. And many of these also indicate what type of information would be appropriate in certain spots more than a lot of other templates do. There are several combinations of woven fabrics fibrous glass mesh, gauze, canvas, etc. The deflection of the reinforcing angles was measured with a dial indicator using as a reference the same superstructure used for the potentiometers, and these measurements were recorded manually.

Flexible ducts may come to the installer in compressed form in a variety of lengths. Adequate airtightness can normally be ensured by a selecting a static pressure, construction class suitable for the operating condition, and b sealing the ductwork properly.


Coincidence with proprietary features is unintentional. The mere presence of sealant at a connection, however, does not ensure low leakage.