HVAC rectangular industrial duct construction standards

RECTANGULAR
INDUSTRIAL DUCT
ONSTRUCTION STANDARDS

-

Inch-Pound Version

SHEET METAL AND AIR’ CONDITIONING CONTRACTORS’
NATIONAL ASSOCIATION, INC.
w w w. smacna org

.


RECTANGULAR
INDUSTRIAL DUCT
CONSTRUCTION STANDARDS

I-P SECOND EDITION - AUGUST, 2004

SHEET METAL AND AIR CONDITIONING CONTRACTORS’
NATIONAL ASSOCIATION, INC.
4201 Lafayette Center Drive
Chantilly, VA 20151-1 209
www.smacna.org

RECTANGULAR
INDUSTRIAL DUCT
CONSTRUCTION STANDARDS
COPYRIGHT02004
All Rights Resewed
by

SHEET METAL AND AIR CONDITIONING CONTRACTORS’
NATIONAL ASSOCIATION, INC.
4201 Lafayette Center Drive
Chantilly, VA 20151-1 209
Printed in the U.S.A.

FIRST EDITION - 1980
I-P SECOND EDITION - AUGUST, 2004

Except as allowed in the Notice to Users and in certain licensing contracts, no part of this book may be
reproduced, stored in a retrievable system, or transmitted, in any form or by any means, electronic,
mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher.


FOREWORD
These duct construction standards are intended for use by contractors, fabricators and designers of air pollution control,
pneumatic conveyance and industrial ventilation systems.
The 1980 edition of these standards was the first publication dealing with the selection of duct gauge and reinforcement
for rectangular industrial duct systems. While the first edition served industry very well for many years, technology
has continued to evolve and in response to our membership’s request, SMACNA’s Rectangular Industrial Duct
Construction Task Force led a comprehensive review and update of the fist edition, resulting in this greatly expanded
and more “user friendly” version of the original publication.
While the new text includes many of the same assumptions as the original work, a number of new features have been

added:
Six different types of carbon galvanized and aluminized steels
Seven different types of stainless steel alloys
Three different types of aluminum alloys
Consideration of wind, snow, ice, and other loads
Design check for localized and global modes of side panel buckling
Design capability for high temperature systems up to 800 “F, and higher with design review by a specialized professional.
New Chapter of practical examples with step-by-step instructions
New Duct Class 5 - for systems handling corrosives
Expanded data for the selection of duct supports, fasteners, gaskets and joint sealants
Accepted Industry Practice for Rectangular Industrial Ducts
New Chapter on Welding
New Guide Specification for the fabrication and Installation of industrial duct systems
The Rectangular Industrial Duct Construction Task Force is deeply indebted to Doctor Michael C. Soteriades who did
the original work for the first edition and contributed greatly to the improvements and expansion of the technical scope
in the new edition. Likewise, the task force is deeply indebted to Joseph M Plecnik, PhD, P.E. of California State University at Long Beach, who is responsible for the physical testing, finite element analysis (FEA) studies, and design
guidance related to the issue of Non-Linear Elastic Buckling of Duct Side Panels on Rectangular Industrial Duct.
SHEET METAL AND AIR CONDITIONING CONTRACTORS’
NATIONAL ASSOCIATION, INC.

Rectangular Industrial Duct Construction Standards

0

I-P Second Edition

iii


RECTANGULAR INDUSTRIAL TASK FORCE

Steven P. Graves, P.E., Chairman
Du-Mont Company
Peoria, IL

Mitchell Hoppe
Melrose Metal Products, Inc.
Fremont, CA

Blake L. Anderson, P.E.
Climate Engineers, Inc.
Cedar Rapids, IA

Ernest R. Menold, P.E.
Ernest D. Menold, Inc.
Lester, PA

John Gundlach
McKinstry Company
Seattle, WA

G. A. Navas, Staff Liaison
SMACNA, lnc.
Chantilly, VA

CONSULTANTS
Douglas S. Barno
DSB Marketing Group, N.A.
Granville, Ohio

Simon J. Scott

Scott Consulting Services, Inc.
Westewille, Ohio

Joseph M. Plecnik, PhD, P.E.
Cal State University, L.B.
Long Beach, CA

Dr. Michael C. Soteriades
Catholic University
Washington, DC

FORMER COMMITTEE MEMBERS AND
OTHER CONTRIBUTORS
Harry Basore
Kansas City, MO

Donald Partney
Granite City, IL

Wallace E. Fizer
Lexington, KY

Michael G. Poja
Milwaukee, WI

William Harbaugh
Houston, TX

Francis J. Walter
Evansville, IN

Marvin Hicks
Idaho Falls, Idaho

Harold Weisgerber
Cincinnati, Ohio

iv

Rectangular Industrial Duct Construction Standards

0

I-P Second Edition


NOTICE TO USERS
OF THIS PUBLICATION

1.

DISCLAIMER OF WARRANTIES

a) The Sheet Metal and Air ConditioningContractors’National Association (“SMACNA”) provides its product for informational
purposes.
b) The product contains “Data” which is believed by SMACNA to be accurate and correct but the data, including all information,
ideas and expressionstherein, is provided strictly “AS IS”, with all faults. SMACNA makes no warranty either express or implied
regarding the Data and SMACNA EXPRESSLY DISCLAIMS ANY IMPLED WARRANTIES OF MERCHANTABILITY OR
FITNESS FOR PARTICULAR PURPOSE.
c) By using the data contained in the product user acceptsthe Data “AS IS’ and assumes all risk of loss, harm or injury that may result

from its use. User acknowledgesthat the Data is complex,subjectto faults and requires verification by competent professionals, and
that modificationof parts of the Data by user may impact the results or other parts of the Data.
d) IN NO EVENT SHALL SMACNA BE LIABLE TO USER, OR ANY OTHER PERSON,FOR ANY INDIRECT, SPECIALOR
CONSEQUENTIAL DAMAGES ARISING, DIRECTLY OR mDIRECTLY, OUT OF OR RELATED TO USER’S USE OF
SMACNA’S PRODUCT OR MODIFICATIONOF DATA THEREIN.This limitationof liability applies even if SMACNAhas been
advised of the possibility of such damages. IN NO EVENT SHALL SMACNA’S LLABILITYEXCEED THE AMOUNT PAID BY
USER FOR ACCESS TO SMACNA’S PRODUCT OR $~,ooO.OO,
WHICHEVER IS GREATER, REGARDLESS OF LEGAL
THEORY.
e) User by its use of SMACNA’sproduct acknowledges and accepts the foregoinglimitation of liability and disclaimer of warranty
and agrees to indemnify and hold harmless SMACNA from and against all injuries, claims, loss or damage arising, directly or indirectly, out of user’s access to or use of SMACNA’s product or the Data contained therein.

2.

ACCEPTANCE

This document or publication is prepared for voluntary acceptance and use within the limitations of applicationdefined herein, and
otherwise as those adopting it or applying it deem appropriate.It is not a safety standard.Its applicationfor a specificproject is contingent on a designeror other authoritydefuing a specificuse. SMACNAhas no power or authority to police or enforce compliance with
the contentsof this document or publication and it has no role in any representationsby other parties that specific components are, in
fact, in compliancewith it.

3.

AMENDMENTS

The Association may, from time to time, issue formal interpretationsor interim amendments, which can be of significance between
successive editions.
4.

PROPRIETARY PRODUCTS

SMACNA encouragestechnologicaldevelopment in the interest of improving the industryfor the public benefit. SMACNAdoes not,
however, endorse individual manufacturersor products.

5.

FORMAL INTERPRETATION

a) A formal interpretation of the literal text herein or the intent of the technical committee or task force associated with the document
or publication is obtainable only on the basis of written petition, addressedto the Technical ResourcesDepartment and sent to the
Association’snational office in Chantilly,Vuginia. In the event that the petitioner has a substantivedisagreement with the interpretation, an appeal may be filed with the Technical Resources Committee, which has technical oversightresponsibility. The request must
pertain to a specificallyidentified portion of the document that does not involve published text which provides the requestedinformation. In considering such requests, the Association will not review or judge products or components as being in compliance with the
document or publication. Oral and written interpretations otherwise obtained from anyone affiliated with the Association are unofficial. This procedure does not prevent any committee or task force chairman,member of the committee or task force, or staff liaison
from expressing an opinion on a provision within the document, provided that such person clearly states that the opinion is personal
and does not represent an official act of the Association in any way, and it should not be relied on as such. The Board of Directors of
SMACNA shall have final authority for interpretation of this standard with such rules or procedures as they may adopt for processing
same.
b) SMACNA disclaims any liability for any personal injury, property damage, or other damage of any nature whatsoever, whether
special, indirect, consequentialor compensatory, direct or indirectly resulting from the publication, use of, or relianceupon this document. SMACNA makes no guaranty or warranty as to the accuracy or completenessof any informationpublished herein.

6.

APPLICATION

a) Any standards contained in this publication were developedusing reliable engineeringprinciples and research plus consultation
with, and information obtained from, manufacturers,users, testing laboratories, and others having specializedexperience.They are

Rectangular Industrial Duct Construction Standards 0 I-P Second Edition

V

subject to revision as further experience and investigationmay show is necessary or desirable. Construction and products which comply with these Standards will not necessarily be acceptableif, when examined and tested, they are found to have other features which
impair the result contemplated by these requirements. The Sheet Metal and Air Conditioning Contractors’ National Association and
other contributors assume no responsibility and accept no liability for the application of the principles or techniques contained in this
publication. Authorities considering adoption of any standardscontained herein should review all federal, state, local, and contract
regulations applicable to specific installations.
b) In issuing and making this document available, SMACNA is not undertaking to render professional or other services for or on
behalf of any person or entity. SMACNA is a t undertaking to perform any duty owed to any person or entity to someone else. Any
person or organization using this document should rely on his, her or its own judgement or, as appropriate,seek the advice of a competent professional in determining the exercise of reasonable care in any given circumstance.
7.

REPRINT PERMISSION

Non-exclusive, royalty-free permission is granted to government and private sector specifying authorities to reproduce only any
construction details found herein in their specifications and contract drawings prepared for receipt of bids on new constniction and
renovation work within the United States and its territories, provided that the material copied is unaltered in substance and that the
reproducer assumes all liability for the specific application, including errors in reproduction.
8.

THE SMACNA LOGO

The SMACNA logo is registered as a membership identification mark. The Associationprescribes acceptable use of the logo and
expressly forbids the use of it to represent anything other than possession of membership. Possession of membership and use of the
logo in no way constitutes or reflects SMACNA approval of any product, method, or component. Furthermore, compliance of any
such item with standards published or recognized by SMACNA is not indicated by presence of the logo.

vi

Rectangular Industrial Duct Construction Standards 0 I-P Second Edition

TABLE OF CONTENTS


TABLE OF CONTENTS
FOREWORD

......................................................................

iii

.........................................

iv

.....................

iV

.........................................

V

RECTANGULAR INDUSTRIAL TASK FORCE

FORMER COMMITTEE MEMBERS AND OTHER CONTRIBUTORS
NOTICE TO USERS OF THIS PUBLICATION
TABLE OF CONTENTS
CHAPTER 1

1.1
1.2
1.3
1.4
1.5
1.6
CHAPTER 2
2.1
2.2
2.3
2.4
CHAPTER 3
3.1
3.2
3.3
3.4
3.5
3.6
3.7
CHAPTER 4
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
4.10

4.11
4.12
4.13
4.14

.............................................................

INTRODUCTION
SCOPE .............................................................
PURPOSE ..........................................................
DEVELOPMENT OF THE SECOND EDITION ...........................
INDUSTRIAL DUCT DESIGN ..........................................
HOW TO USE THIS MANUAL .........................................
MANUAL CONTENTS ................................................

vi¡
Page
1.1
1.1
1.1
1.1
1.2
1.2

INDUSTRIAL DUCT APPLICATIONS
INTRODUCTION ....................................................
DEFINITION OF INDUSTRIAL DUCT ..................................
DUCT SYSTEM CLASSIFICATION ....................................
MATERIAL (PARTICULATE) CHARACTERISTICS AND CLASSES. . . . . . . . .

2.1
2.1
2.1
2.2

DUCT MATERIALS
INTRODUCTION ....................................................
MATERIAL TYPES ...................................................
CARBON AND COATED STEEL DATA .................................
STAINLESS STEEL DATA ............................................
ALUMINUM DATA ...................................................
MATERIAL PROPERTIES SUMMARY ..................................
CORROSION .......................................................

3.1
3.1
3.4
3.9
3.12
3.14
3.15

DESIGN CRITERIA
INTRODUCTION ....................................................
GENERAL PROVISIONS .............................................
NOMENCLATURE ...................................................
LOADS .............................................................
LIMITS AND TOLERANCES ..........................................
SERVICEA6ILITY AND DURABILITY ..................................
DESIGN OF DUCT THICKNESS .......................................

DESIGN OF STIFFENER SIZE ........................................
DESIGN OF SUPPORT SPACING .....................................
BOLTING OF CONNECTIONS ........................................
CHECKING SHEAR CAPACITY OF DUCT SIDE WALLS .................
CRITERIA FOR THE DESIGN OF SYSTEMS WITH
INTERNAL SUPPORTS ..............................................
HANGERS AND SUPPORTS ..........................................
THERMAL EXPANSION ..............................................

Rectangular Industrial Duct Construction Standards t-P Second Edition

4.1
4.1
4.1
4.3
4.7
4.7
4.7
4.11
4.12
4.13
4.16
4.21
4.24
4.26

vi i


CHAPTER 5

DESIGN EXAMPLES

5.1
DESIGN EXAMPLES .................................................
5.2
SUBDIVIDING PANELS AND SELECTING INTERNAL SUPPORTS . . . . . . . .
EXAMPLE #5-1 ............................................................
EXAMPLE #5-2 ............................................................
EXAMPLE #5-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
EXAMPLE #5-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
EXAMPLE #5-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
EXAMPLE #5-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
EXAMPLE #5-7 ............................................................
CHAPTER 6
6.1
6.2
6.3
6.4
6.5
6.6
6.7
CHAPTER 7
7.1
7.2
7.3
7.4
7.5
7.6

7.7
CHAPTER 8
8.1
8.2
8.3
8.4
8.5
8.6
8.7
CHAPTER 9
9.1
9.2
9.3
9.4
9.5
9.6

Page
5.1
5.30
5.2
5.5
5.7
5.12
5.15
5.21
5.25

DUCT SELECTION TABLES .
CARBON AND COATED STEELS

INTRODUCTION ....................................................
SCOPE .............................................................
MINIMUM MATERIAL MECHANICAL PROPERTIES .....................
USE OF THE TABLES ................................................
DESIGN PROCESS ..................................................
DUCT SELECTION TABLES ..........................................
AUXILIARY TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.1
6.1
6.1
6.1
6.5
6.9
6.96

DUCT SELECTION TABLES .
STAINLESS STEEL
INTRODUCTION ....................................................
SCOPE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
MINIMUM MATERIAL MECHANICAL PROPERTIES .....................
USE OF THE TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DESIGN PROCESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DUCT SELECTION TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
AUXILIARY TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7.1
7.1
7.1
7.1

7.5
7.9
7.17

DUCT SELECTION TABLES .
ALUMINUM
INTRODUCTION ....................................................
SCOPE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
MINIMUM MATERIAL MECHANICAL PROPERTIES .....................
USE OF THE TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DESIGN PROCESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DUCT SELECTION TABLES ..........................................
AUXILIARY TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8.1
8.1
8.1
8.1
8.5
8.9
8.17

HANGERS. SUPPORTS. FASTENERS. GASKETS. AND JOINT SEALANTS
INTRODUCTION AND SCOPE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
HANGERS AND SUPPORTS COMMENTARY ...........................
GENERAL GUIDELINES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
METHODS FOR HANGING AND SUPPORTING DUCT . . . . . . . . . . . . . . . . . .
DUCT HANGERS AND SUPPORTS ...................................
GASKETS, CAULKING, AND JOINT SEALANTS ........................

9.1
9.1
9.1
9.2
9.2
9.14

CHAPTER 1O WELDING
10.1
10.2
10.3
10.4
10.5
10.6
viii

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
WELDED JOINT ACCEPTED INDUSTRY PRACTICE ....................
WELDED JOINT CONSIDERATIONS ..................................
TYPES OF JOINTS AND EDGE PREPARATION ........................
WELDING PROCEDURES ............................................
WELDING SYMBOLS ................................................
Rectangular Industrial Duct Construction Standards I-P Second Edition

10.1
10.1
10.1
10.8
10.8
10.16

CHAPTER 11 ACCEPTED INDUSTRIAL CONSTRUCTION PRACTICES
11.1
11.2
11.3

INTRODUCTION ....................................................
COMMON SEAMS AND JOINTS ......................................
FABRICATION TOLERANCES ........................................

Page
11.1
11.1
11.1

CHAPTER 12 GUIDE SPECIFICATION
12.1
12.2
12.3
12.4
APPENDIX A

INTRODUCTION ....................................................
DRAWINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SEISMIC RESTRAINT PROVISIONS ...................................
GUIDE SPECIFICATION ..............................................

12.1
12.1

12.1
12.1

COMMENTARY ON FORMULA DERIVATIONS AND UNITS

APPENDIX B SUPPLEMENTARY DESIGN DATA
B.l

INTRODUCTION

....................................................

6.1

APPENDIX C COMMENTARY ON SURFACE PREPARATION TECHNIQUES
C.l
C.2

INTRODUCTION ....................................................
METAL SURFACE PREPARATION .....................................

C.l
C.l

APPENDIX D REFERENCED DOCUMENTS
D.l
D.2
D.3
D.4
D.5

D.6
D.7

ASTM STANDARDS .................................................
ANSI STANDARDS ..................................................
NFPASTANDARDS ..................................................
ASME STANDARDS .................................................
SMACNA STANDARDS ..............................................
OTHER STANDARDS ................................................
OTHER RESOURCES ................................................

D.l
D.2
D.2
D.2
D.2
D.2
D.4

GLOSSARY
INDEX

Rectangular Industrial Duct Construction Standards I-P Second Edition

ix


TABLES

Page

Duct Classes and Minimum Conveying Velocities .........................
Material Class Descriptions ............................................
Specific Materials Classes .............................................
Hot-rolled Steel Gages ...............................................
Cold-rolled Steel Gages ..............................................
Galvanized and Aluminized Steel Gages ................................
Yield Strength Reduction Factor (vf)at
Elevated Temperatures for Carbon and Coated Steels ....................
Modulus of Elasticity Reduction Factor (77, ) at
3-5
Elevated Temperatures for Carbon and Coated Steels ....................
3-6
Stainless Steel Gages ................................................
Yield Strength Reduction Factor (qf)at
3-7
Elevated Temperatures for Stainless Steel ...............................
) at
Modulus of Elasticity Reduction Factor (7,
3-8
Elevated Temperatures for Stainless Steel ...............................
3-9
Aluminum Sheet Gages ...............................................
3-1 O Yield Strength Reduction factor ( r l f )
at Elevated Temperatures for Aluminum .................................
Modulus of Elasticity Reduction Factor (ve)
3-11
at Elevated Temperatures for Aluminum .................................
3-1 2 Material Properties and Temperature Limits ..............................
3-1 3 Corrosion Chart ......................................................

4-1
Coefficients for Mode B Analysis ........................................
5-1
Design Example Variables .............................................
6.1 -XAX
List of Commercial Grade 32 ksi Carbon Steel Tables . . . . . . . . . . . . . . . . .
6.2-XAX
List of Structural Grade 36 ksi Carbon Steel Tables ...................
List of Structural Grade 50 ksi Carbon Steel Tables ....................
6.3-XAX
6-X
List of Auxiliary Carbon Steel Tables ....................................
7-A.X List of 35 ksi Stainless Steel Tables .....................................
7-X
List of Auxiliary Stainless Steel Tables ..................................
8-A.X List of 20 ksi Aluminum Tables .........................................
8-X
List of Auxiliary Aluminum Tables .......................................
9-1
Support Capacity of Horizontal Channel .................................
9-2
Support Capacity of HorizontalAngle ...................................
9-3
Standard Steel Pipe Column - Loads ...................................
9-4
Hanger Rod Capacity .................................................
9-5
Hanger Bar Capacity .................................................
9-6
Hanger Angle Capacity ...............................................

9-7
Knee Brace Hanger Capacity ..........................................
Knee Brace Support Capacity ..........................................
9-8
9-9
Bolt Stress Area .....................................................
9-10
Grade Markings for Steel Bolts .........................................
9-11
Gaskets. Caulking. and Joint Sealants ..................................
9-11
Gaskets. Caulking. and Joint Sealants (continued) ........................
10-1
Allowable Stress For Stitch Welds ......................................
10-2 Welded Joint Designs - Butt Joints (6) .................................
10-3 Welded Joint Designs - Corner and Butt Joints (C and 9) .................
10-4 Welded Joint Designs - Corner and Tee Joints (C and T) . . . . . . . . . . . . . . . . .
10-5 Gas Metal Arc Welding of Carbon Steel .................................
10-6 Shielded Metal Arc Welding (SMAW) of Carbon Steel .....................
10-7 Gas Tungsten Arc Welding (GTAW) of Carbon Steel ......................
10-8 Gas Metal Arc Welding (GMAW) of Galvanized Steel .....................
10-9 Shielded Metal Arc Welding (SMAW) of Galvanized Steel . . . . . . . . . . . . . . . . . .
10-10 Gas Tungsten Arc Welding (GTAW) of Galvanized Steel . . . . . . . . . . . . . . . . . . .
10-11 Gas Metal Arc Welding of Stainless Steel ...............................
10-12 Shielded Metal Arc Welding (SMAW) of Austenitic Stainless Steel . . . . . . . . . .
10-13 Gas Tungsten Arc Welding (GTAW) of Austenitic Stainless Steel . . . . . . . . . . .
10-1 4 Gas Metal Arc Welding of Aluminum ....................................
10-1 5 Gas Tungsten Arc Welding (GTAW) of Aluminum .........................

2-1

2-2
2-3
3-1
3-2
3-3
3-4

X

Rectangular Industrial Duct Construction Standards

0

I-P Second Edition

4.10
2.4
2.5
3.4
3.5
3.6
3.7
3.7
3.10
3.10
3.11
3.12
3.13
3.13
3.14

3.16
4.10
5.1
6.9
6.43
6.69
6.95
7.9

7.17
8.9
8.17
9.6
9.7
9.8
9.9
9.9
9.9
9.10
9.11
9.12
9.13
9.14
9.15
10.3
10.4
10.5
10.6
10.10
10.11

10.11
10.12
10.12
10.12
10.13
10.14
10.14
10.15
10.15


6-1
8-2

6-3
8-4
C-1
C-2

Conversion of Wind Loads ............................................
Insulation Physical Data ...............................................
Lagging Physical Data ................................................
Thermal Expansion Chart .............................................
Surface Conditions and Recommended Treatment ........................
Surface Preparation Methods ..........................................

Rectangular Industrial Duct Construction Standards 0 I-P Second Edition

6.3
8.7

6.8
B.9
C.2
C.2


FIGURES

Page

4-1
4-2
4-3
4-4
4-5
4-6
4-7
4-8
4-9
4-10
4-11
4-12
4-13
4-1 4
4-1 5
5-1
5-2
6-1
6-2
6-3

6-4
6-5
7-1
7-2
7-3
7-4
7-5
8-1
8-2
8-3
8-4
8-5
9-1
9-2
10-1
10-2
10-3
10-4
10-5
11-1
11-2
11-3
11-4
11-5
11-6
11-7
11-8
11-9
11-1 O
11-11

11-1 2
11-13
6-1
B-2
B-3
B-4

xi¡

Critical Load Diagrams for Worst Case Conditions ........................
Particulate Load .....................................................
Panel Loading-Mode A ..............................................
Panel Loading-Mode B ..............................................
Stiffener Loading .....................................................
Equivalent Beam Cross-Section .......................................
Flanged Connection ..................................................
Types of Sidewall Buckling ............................................
Reinforcement Patch .................................................
Comparison of Critical Buckling Loads for 48 x 24 in. duct . . . . . . . . . . . . . . . . .
Comparison of Critical Buckling Loads for 72 x 36 in. duct . . . . . . . . . . . . . . . . .
Internal Supports .....................................................
Fixed Stiffeners ......................................................
Unfixed Stiff eners ....................................................
Definition of Riser Support Loads .......................................
Subdividing Panels ...................................................
Internal Pipe Supports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Critical Load Diagrams for Worst Case Conditions ........................
Stiffening Guidelines for Flat Panels ....................................
Sample Panel capacity Options from Table 6.1-1 A.l ......................
Panel Thickness ¿? Deflection per Stiffener Spacing .......................

Stiffener Size per Stiffener Spacing .....................................
Critical Load Diagrams for Worst Case Conditions ........................
Stiffening Guidelines for Flat Panels ....................................
Sample Panel capacity Options from Table 7-A.3 ........................
Panel Thickness & Deflection per Stiffener Spacing .......................
Stiffener Size per Stiffener Spacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Critical Load Diagrams for Worst Case Conditions ........................
Stiffening Guidelines for Flat Panels ....................................
Sample Panel Capacity Options from Table 8-A.2 ........................
Panel Thickness & Deflection per Stiffener Spacing .......................
Stiffener Size per Stiffener Spacing .....................................
Hanger Attachments to Structures ......................................
Upper Attachment Devices - Typical ....................................
Joints, Welds, and Grooves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Standard Location of Elements of a Welding Symbol ......................
Supplementary Symbols ..............................................
Typical Weld Symbols Used for
Sheet Metal and Light Plate ...........................................
Plate Welding Symbols ...............................................
Longitudinal Seams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Longitudinal Seams (continued) ........................................
Transverse Seams or Joints ...........................................
Crossbraking Light Gage Panels .......................................
Types of Stiffeners ...................................................
Types of Stiffeners (continued) .........................................
Internal Pipe Supports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Types of Flanged Connections .........................................
Expansion Joints .....................................................
Flexible Connections .................................................
Access Doors .......................................................

Explosion Door ......................................................
Various Fittings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Basic Wind Speed (mph) ..............................................
Snow Ground Load Western U.S. (Ib/sq ft) .............................
Snow Ground Load - eastern U.S.(Ib/sq ft) ..............................
Glaze Ice Accretion Zone .............................................

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CHAPTER 1

INTRODUCTION


INTRODUCTION

CHAPTER 1

The scope of this manual includes the determination of
the necessary construction details for the fabrication
and installation of rectangular metallic industrial duct
within the following general categories, and as further
detailed in the scope of individual chapters, through a
variety of both analytical and empirical methods:
O

Fabricated from flat sheet or plate panels, using welded seam, grooved lockseam, Pittsburgh lock, and standing seam techniques.

o

From commercial grades of carbon, galvanized, aluminized, or stainless steel, or aluminum of the various grades and types as described in Chapter 3.

O

For a design pressure within the range from
negative 150 in. wg to positive 150 in. wg.

O

To be supported at intervals not exceeding
30 ft.

O

1.2

facility managers, and pollution control authorities.

SCOPE

1.1

To provide an authoritative source of documentation and terminology for operations involved in the construction and installation of
rectangular metallic industrial duct.

The objectives behind the development of this second
edition of SMACNA’s Rectangular Industrial Duct
Construction Standards are to expand the scope of the

first edition; update the theoretical basis for design;
improve the presentation to make the expanded publication more “user friendly;” to cover both the simple,
low or moderate temperature and pressure indoor systems, as well as the more complex outdoor systems,
operating at moderate to high temperature and pressure, and subjected to higher and more complex external loading.

To achieve these objectives the following steps were
taken:

For a design temperature not exceeding the
specific operating limits listed for each type
and grade of metal included in Chapter 3.

O

With panel widths (w) up to 12 ft.

O

Listing of rated stiffeners, flanges, hanger
and support elements, and the methods for selecting them for specific structural loads.

O

An accepted industry practices for the fabrication and installation of rectangular metallic industrial duct, with its fittings, appurtenances, accessories, insulation, lagging,
hangers and supports.

DEVELOPMENT OF THE SECOND
EDITION

1.3

o

A professional review of the theoretical basis
for the first edition was completed and an expansion of the examples to include both global and localized shear capacity of the side
walls.

O

Laboratory testing and data analysis on rectangular duct were completed to support the
addition of a side wall shear capacity check
to those already introduced in the first edition.

o

Material previously covered in broad terms
was expanded through in-depth coverage.
New chapters were added covering such duct
fabrication topics as Stiffeners, Flanges, and
Fasteners; Hangers and Supports; Welding;
Accepted Industrial Construction Practices;
and a Guide Specification.

O

To provide for the design process of duct systems from the very simple to the complex,
while making the process %er friendly,” the
design or duct selection process was developed as a Table Driven Process.

PURPOSE

There were three primary purposes behind the development of this manual:

To develop minimum standards for the fabrication and installation of metallic rectangular industrial duct systems.
To develop new, and collect existing, duct
construction practices and data to serve as an
authoritative source of accepted industrial
practices for contractors, design engineers,

1.4

INDUSTRIAL DUCT DESIGN

The approach, or avenue to rectangular industrial duct
design is as described here:

Rectangular Industrial Duct Construction Standards 0 I-P Second Edition

1.1


Table Driven Process - The selection data for rectangular duct is divided into three chapters, each dealing
with a different material type: Carbon, Galvanized,
and Aluminized Steel (Chapter 6), Stainless Steel
(Chapter 7), and Aluminum (Chapter 8). Each chapter
has its own detailed example covering the main selection options. Use of this design process is not limited
to indoor applications, but includes wind loads and
snowhce or maintenance loads, in addition to internal
particulate loads.
HOW TO USE THIS MANUAL

1.5

As described in the above, it has been an objective of
the Rectangular Industrial Duct Construction Task
Force to make this publication more “user friendly”
than its predecessor.
The following tips are intended to familiarize the user
with the content and organization of this manual. They
are also intended to guide the user in selecting the right
chapter or sequence of chapters to consult depending
on the immediate objective.
a.

Chapters 2 and 3 are especially important to
the specifying engineer or to a “designibuild”
contractor. Chapter 2 contains basic information necessary for identifying and speciQing
the duct class.

b.

Chapter 3 deals entirely with detailed information on the mechanical characteristics of
all the metals covered by these construction
standards; it also includes a corrosion table
covering various metals and liner materials
and their corrosion performance when subjected to various corrosive agents. Chapter 3
information is useful in either selecting and
speci@ing a duct material or in identifjing
the mechanical characteristics of specified
duct materials.

c.

1.2

Chapters 4 and 5 are of interest to all users.
There is useful information, examples, and
guidance in these two chapters that may be of
greatest benefit to speci@ing engineers, designers, and contractors.

d.

Chapters 6,7, and 8 constitute the bulk of the
material needed for duct selection.

e.

Chapter 9, 10, and 11 all deal with construction details and accepted industry practices
for rectangular duct and appurtenances.
These chapters are of interest to all users.

f.

Chapter 12 is a guide specification for industrial duct construction and installation. It is of
most interest to specifying engineers.

g* The Appendices and Glossary contain terminology, design data, and other supplementary information useful to both specifiers and
contractors.
1.6

MANUAL CONTENTS

CHAPTER 1 INTRODUCTION
The introduction outlines the format and layout of the
manual, provides instruction for its use, and contains
a summary of the contents of each chapter.
CHAPTER 2

INDUSTRIAL DUCT
APPLICATIONS
This chapter contains various definitions and information related to industrial duct classes, as well as relevant physical characteristics of materials frequently
conveyed in industrial duct systems. It is envisioned
that the designer will use the information contained in
this chapter (or similar information from other sources
such as those listed in section 2.2) to speci@ the most
appropriate Duct Class for the system under consideration, and the concentration and characteristics of the
materials being conveyed. The specification of the
Duct Class and an accurate appraisal of the characteristics of the materials being conveyedplay a critical
role in the successful design of an industrial duct system. Their importance can not be over-emphasized.
CHAPTER 3 DUCT MATERIALS
This chapter contains detailed information on the
physical characteristics of the most common materials
used in industrial duct construction. Also included are
brief descriptions of each material type, its most common uses, and some limitations that may apply. It is envisioned that this chapter may be used as a reference
when selecting duct materials.
CHAPTER 4
DESIGN CRITERIA
This chapter contains design criteria-subject to the
limitations expressed in section 4.2-for the construction of rectangular industrial duct.
CHAPTER 5 DESIGN EXAMPLES

This chapter contains several industrial duct design
cases, fully developed with references to the applicable sections, equations, tables, and figures contained
in other parts of the manual including internal pipe
supports, stiffeners, support spans, flanges, and side
wall buckling.

Rectangular Industrial Duct Construction Standards I-P Second Edition


CHAPTER 6

DUCT SELECTION TABLES
CARBON,GALVANIZED, AND
ALUMINIZED STEEL
This chapter contains the basic duct selection tables
for rectangular industrial ducts, fabricated using longitudinal welded seam or lockseam techniques, from
carbon, galvanized, or aluminized steels as described
in Chapter 3.
CHAPTER 7

DUCT SELECTION TABLES
STAINLESS STEEL
This chapter contains the basic duct selection tables
for rectangular industrial ducts, fabricated using longitudinal welded seam or lockseam techniques, from
any of the stainless steel alloys described in Chapter 3.
CHAPTER 8

DUCT SELECTION TABLES
ALUMINUM
This chapter contains the basic duct selection tables

for rectangular industrial ducts, fabricated using longitudinal welded seam or lockseam techniques, from
any of the aluminum alloys described in Chapter 3.
CHAPTER 9

HANGERS, SUPPORTS, FASTENERS, GASKETS, CAULKING, AND JOINT SEALANTS
This chapter contains the necessary tables, instructions, and examples to assist the user in selecting from
among various s p e s of hangers, supports, fasteners,
gaskets, caulking, and joint sealants.
CHAPTER 10 WELDING
The information contained in this chapter is designed
to identify the welding assumptions used in the structural design of SMACNA rectangular industrial ducts.
Additionally, there is useful commentary on accepted
industry practice concerning welding, guidelines for
the application of partial and full (or complete) joint

penetration designs, tables describing full and partial
penetration joint designs, data useful in developing
welding procedures, and a description and commentary on the use of AWS welding symbols.

CHAPTER 11 ACCEPTED INDUSTRIAL
CONSTRUCTION PRACTICES
This chapter contains those features of rectangular
duct fabrication for which there exists a body of accepted field experience with practices having a proven
record of satisfactory performance.
CHAPTER 12 GUIDE SPECIFICATION
This chapter provides a guide for specifying rectangular industrial duct for industrial ventilation systems.
The guide specification is not intended as a reference
document, but rather as a guide for the development of
specificationsfor a particular project. The guide specification must be edited to fit the conditions of use and
work assignments. Particular attention should be given to the deletion of inapplicable provisions and inclusion of necessary items related to a specific project.

APPENDIX A COMMENTARY ON FORMULA
DERIVATION§ AND UNITS
APPENDIX B SUPPLEMENTARY DESIGN
DATA
APPENDIX C COMMENTARY ON SURFACE
PREPARATION TECHNIQUES
APPENDIX D REFERENCED DOCUMENTS
GLOSSARY
INDEX

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Rectangular Industrial Duct Construction Standards 0 i-P Second Edition



CHAPTER 2

INDUSTRIAL DUCT APPLICATIONS