AMERICAN NATIONAL STANDARD ANSI/ASSE Z359.6-2009 Specifications and Design Requirements for Active Fall Protection Systems Part of the Fall Protection Code A S S E AMERICAN S OCIETY OF S AFETY E NGINEERS The information and materials contained in this publication have been developed from sources believed to be reliable. However, the American Society of Safety Engineers (ASSE) as secretariat of the ANSI accredited Z359 Committee or individual committee members accept no legal responsibility for the correctness or completeness of this material or its application to speci fi c factual situations. By publication of this standard, ASSE or the Z359 Committee does not ensure that adherence to these recommendations will protect the safety or health of any persons, or preserve property ANSI® ANSI/ASSE Z359.6 – 2009 American National Standard Speci fi cations and Design Requirements for Active Fall Protection Systems Secretariat American Society of Safety Engineers 1 800 East Oakton Street Des Plaines, Illinois 6001 8-21 87 Approved June 3, 2009 Effective Date November 16, 2009 American National Standards Institute, Inc. American National Standard Approval of an American National Standard requires veri fi cation by ANSI that the requirements for due process, consensus, and other criteria for approval have been met by the standards developer. Consensus is established when, in the judgment of the ANSI Board of Standards Review, substantial agreement has been reached by directly and materially affected interests. Substantial agreement means much more than a simple majority, but not necessarily unanimity. Consensus requires that all views and objections be considered, and that a concerted effort be made toward their resolution. The use of American National Standards is completely voluntary; their existence does not in any respect preclude anyone, whether he/she has approved the standards or not, from manufacturing, marketing, purchasing, or using products, processes, or procedures not conforming to the standards. The American National Standards Institute does not develop standards and will in no circumstance give an interpretation of any American National Standard. Moreover, no person shall have the right or authority to issue an interpretation of an American National Standard in the name of the American National Standards Institute. Requests for interpretation should be addressed to the secretariat or sponsor whose name appears on the title page of this standard. Caution Notice: This American National Standard may be revised or withdrawn at any time. The procedures of the American National Standards Institute require that action be taken periodically to reaffi rm, revise, or withdraw this standard. Purchasers of American National Standards may receive current information on all standards by calling or writing the American National Standards Institute. Published August 2009 by: American Society of Safety Engineers 1 800 East Oakton Street Des Plaines, Illinois 60018-2187 (847) 699-2929 • www.asse.org Copyright ©2009 by American Society of Safety Engineers All Rights Reserved. No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher. Printed in the United States of America Foreword (This Foreword is not a part of American National Standard Z359.6-2009.) This standard, national in scope, was developed by an Accredited Standards Committee functioning under the procedures of the American National Standards Institute, with the American Society of Safety Engineers (ASSE) as secretariat. This standard establishes guidelines and minimum requirements for the development of the various components that would comprise a comprehensive managed fall protection program. It is intended that every employer whose operations fall within the scope and purpose of the standard will adopt the guidelines and requirements detailed in this standard. The need for this standard activity grew out of the continuing development of a series of fall protectionrelated standards. The focus is to provide guidance to designers of active fall protection systems. It should be noted, as in all Z359-series standards, that this standard applies to all occupational and non-occupational activities except those in SIC Division C (construction). It also is not intended to apply to sports activities such as mountaineering. Neither the standards committee, nor the secretariat, states that this standard is perfect or in its ultimate form. It is recognized that new developments are to be expected, and that revisions of the standard will be necessary as the state-of-the-art progresses and further experience is gained. It is felt, however, that uniform guidelines for the design of active fall protection systems are very much needed and that the standard in its present form provides for the minimum criteria necessary. The Z359 Committee acknowledges the critical role of design in in fl uencing the use of proper fall protection equipment. Design de fi ciencies often increase the risk for employees who may be exposed to fall hazards: examples are (1) lack of rail systems to prevent falls from machines, equipment and structures; (2) failure to provide engineered anchorages where use of personal fall arrest systems are anticipated; (3) no provision for safe access to elevated work areas; (4) installation of machines or equipment at heights, rather than fl oor/ ground level to preclude access to elevated areas; (5) failure to plan for the use of travel restriction or work positioning devices. The Z359 Committee solicits public input that may suggest the need for revisions to this standard. Such input should be sent to the Secretariat, ASC Z359, American Society of Safety Engineers, 1 800 E. Oakton Street, Des Plaines, IL 6001 8-21 87. This standard was developed and approved for submittal to ANSI by the American National Standards Committee on Standards for Fall Protection, Z359. Committee approval of the standard does not necessarily imply that all committee members voted for its approval. At the time it approved this standard, the Z359 Committee had the following members: Randall Wing fi eld, Chairman Basil Tominna, P.E., Vice Chairman Timothy R. Fisher, CSP, CHMM, ARM, CPEA, Secretary Jennie Dalesandro, Administrative Technical Support Organization Represented Name of Representative American Society of Safety Engineers Daniel Paine Carl Griffi th, CSHM, CPSM, CHCM, CUSA, CPEA Bradley S. McGill Roderick A. Paul Chuck Orebaugh Joey R. Junio Jim Rullo Chris Delavera J. Thomas Wolner, P.E. Brad Rohlf Craig Berkenmeier Joe Burke James W. Lane, CSP, P.E. Mark C. Conover Paul Doepel Dr. J. Nigel Ellis, P.E., CSP, CPE John T. Whitty, P.E. Hugh Armstrong David Lee Randall Wing fi eld Dave Lough Timothy Healey Jerome Kucharski, CFPS Jack Lamberson Bruce Guiliani Frank Anzaldi Ron Larkin Russell Goldmann, II Janice C. Bradley, CSP David H. Pate, CUSA Thomas Kramer, P.E., CSP Rupert Noton, CEng, MIStructE Paul Illick Lynn Camp Bashlin Industries, Inc. Boeing Company Buckingham Mfg. Co., Inc. Capital Safety Group Chevron Chrysler LLC Elk River, Inc. Ellis Fall Safety Solutions Flexible Lifeline Systems Gravitec Systems, Inc. Hartford Steam Boiler Inspection & Insurance Co. Heritage Group Safety Hy-Safe Technology ISEA – International Safety Equipment Association Indianapolis Power and Light LJB Inc. Latchways PLC Lawrence Livermore National Security Liberty Mutual Group Lighthouse Safety LLC MSA Monsanto Murdock Webbing Co. Inc. National Association of Tower Erectors Pamela R. Huck, Inc. Peakworks PenSafe Reliance Industries, LLC SPRAT – Society of Professional Rope Access Technicians Safety Connection Safety Equipment Institute Safety Through Engineering, Inc. Scaffold Industry Association SPANCO, Inc. Sperian Protection Sturges Manufacturing Co., Inc. Tractel Inc. Travelers Tritech Fall Protection United Auto Workers U.S. Air Force Safety Center U.S. Bureau of Reclamation John Rabovsky, MS, CSP, ARM Peter Furst John Corriveau Joseph Feldstein Robert Apel Robert Kling, P.E., CSP Chad M. McDanel Bob Golz Greg Pilgrim Gordon Lyman Don Doty Pamela Huck, CSP Tim Accursi Gabe Fusco Keith Smith W. Joe Shaw Gary Choate Loui McCurley Jim Frank Clint Honeycutt, Sr. Chad Bourgeois Steve Sanders Mike C. Wright, P.E., CPE, CSP Jeremy T. Deason, P.E. Scott Billish Daniel Zarletti Arnie Galpin, P.E. George Nolan Preston Anderson Chuck Ziegler Richard Griffi th Tyler Griffi th Doug Knapp Cliff Theve Scott H. Richert, CSP, ARM, ALCM John Seto Craig Siciliani Tom Kinman John Rupp, Jr. Thomas Pazell Arvie E. Scott Steven C. Beason Victor Feuerstein, CIH U.S. Department of Labor – OSHA U.S. Department of the Navy Western Area Power Administration Subgroup Z359.6 had the following members: Thomas Kramer, P.E., CSP (Chair) Frank Anzaldi John Corriveau Dr. J. Nigel Ellis, P.E., CSP, CPE Peter Furst Joey Junio Robert Kling, P.E., CSP Paul Illick Ken Mahnick Chad M. McDanel Daniel Paine David H. Pate, CUSA John Rabovsky, MS, CSP, ARM W. Joe Shaw Greg Small, P.Eng., M.Eng. Basil Tominna, P.E. Mike C. Wright, P.E., CPE, CSP Sherman Williamson John Newquist Basil Tominna, P.E. Douglas L. Craddock Jeff Wild Ralph Armstrong Contents SECTION .................................................................................................................. PAGE 1 . Scope, Purpose, Applications, Exceptions and Interpretations ........................ 8 1 .1 Scope .......................................................................................................... 8 1 .2 Purpose and Application ........................................................................... 8 1 .3 Exceptions .................................................................................................. 9 1 .4 Interpretations ............................................................................................ 1 0 2. De fi nitions ................................................................................................................ 1 0 3. Drawings and Speci fi cations ................................................................................. 1 0 3.1 General ........................................................................................................ 1 0 3.2 Sealing by a Professional Engineer ......................................................... 1 0 3.3 Required Information ................................................................................. 11 4. Materials, Equipment, and Other Design Requirements ................................... 1 3 4.1 Composition of Materials .......................................................................... 1 3 4.2 Ductility of Materials .................................................................................. 1 3 4.3 Environmental Considerations ................................................................. 1 3 4.4 Equipment ................................................................................................... 1 3 4.5 Other Design Requirements for Travel Restraint Systems ................... 1 7 4.6 Other Design Requirements for Fall Arrest Systems ............................. 1 7 5. Safety Criteria ......................................................................................................... 1 8 5.1 Speci fi ed Loads .......................................................................................... 1 8 5.2 Strength ....................................................................................................... 1 9 5.3 Swing Falls .................................................................................................. 21 5.4 Forces on the Worker’s Body ................................................................... 21 5.5 Clearance .................................................................................................... 22 5.6 Stability of Free-Standing Systems .......................................................... 22 6. Fall Protection System Loads and Forces ........................................................... 24 6.1 General ....................................................................................................... 24 6.2 Travel Restraint Systems .......................................................................... 24 6.3 Fall Arrest Systems ................................................................................... 25 7. Clearances for Fall Arrest Systems ...................................................................... 28 7.1 Clearance Reference ................................................................................ 28 7.2 Required Clearance .................................................................................. 28 8. Design Assumptions and Analytical Methods ..................................................... 32 8.1 Elasticity of Ropes ..................................................................................... 32 8.2 Horizontal Lifelines Sags .......................................................................... 32 8.3 Analytical Methods .................................................................................... 32 9. References .............................................................................................................. 34 1 0. Figures ................................................................................................................... 35 Appendices A Commentary ........................................................................................................... 42 B Bibliography ............................................................................................................ 51 ANSI/ASSE Z359.6-2009 American National Standard STANDARD REQUIREMENTS 1 . SCOPE, PURPOSE, APPLICATIONS, EXCEPTIONS AND INTERPRETATIONS Specifications and Design Requirements for Active Fall Protection Systems EXPLANATORY INFORMATION (Not part of American National Standard Z359. 1) 1 .1 Scope. 1 .1 .1 This standard is intended for engineers with expertise in designing fall protection systems. It speci fi es requirements for the design and performance of complete active fall protection systems, including travel restraint and vertical and horizontal fall arrest systems. E1.1.1 In most cases, the engineer should be a professional engineer. However, there are some exceptions where it is permissible per a local building code for an engineer who is not registered with a state or other governing body to perform engineering. It is strongly recommended that if this work is being performed by a consultant for a client, that the work be performed under the supervision of a professional engineer. 1 .2 Purpose and Application. 1 .2.1 This standard has been developed as a consensus document to provide uniform practice in the design of active fall protection systems. The intention is to provide design criteria for routine use and not to provide speci fi c criteria for infrequently encountered problems which occur. 1 .2.2 This standard involves the application of the last option from the hierarchy of fall protection – active fall protection systems. Other options for employee protection should be considered prior to the employer selecting the use of an active fall protection system. E1.2.2 The ANSI/ASSE Z359. 2 standard contains a hierarchy of fall protection (See Section 5. 1). The first and preferred element of the hierarchy is eliminating fall hazards. OSHA Instruction STD 1-1. 13 states that “in situations where the safeguarding [through the use of physical barriers is] not applicable because employees are exposed to falls from an elevated surface other than a predictable and regular basis, personal protective equipment as required by 29 CFR 1910. 132(a) or other effective fall protection shall be provided. ” Furthermore, predictable and regular was de fined in this document as: a. At least once every 2 weeks, or b. For a total of 4 man-hours or more during any sequential 4-week period (e. g. , 2 employees once every 4 weeks for 2 hours = 4 man-hours per 4-week period). Ap pr ove e ri c a n N at i o n a l d Am Sta n da rd 8 AMERICAN S OCIETY OF S AFETY E NGINEERS ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems 1 .3 Exceptions. 1 .3.1 This standard is not intended as a substitute for testing and certi fi cation of individual components of fall protection equipment in accordance with applicable ANSI/ASSE Z359 equipment standards. 1 .3.2 This standard does not cover the design of passive fall protection systems such as guardrails and nets, except where such passive systems are also designed to serve as anchorage and/or anchorage connector subsystems for active fall protection systems covered by this standard. 1 .3.3 This standard does not cover the design of positioning systems. 1 .3.4 This standard does not cover the determination of structural strength and behavior of components or anchorages of active fall protection systems. It does, however, establish the safety criteria once the strengths and behaviors are known. Such strengths and behaviors are determined by analytical testing or engineering methods and by AISC, ACI, NDS or other design standards for the materials and structural systems being used. The IBC, ASCE, state and local building codes shall be referenced by the designer of active fall protections systems. E1.3.4 AISC – American Institute of Steel Construction. ACI – American Concrete Institute NDS – National Design Standard for Wood Construction IBC – International Building Code ASCE – American Society of Civil Engineers 1 .3.5 This standard does not specify design or performance requirements for fall arrest equipment or systems that have been manufactured and successfully tested in accordance with the requirements of another ANSI/ASSE Z359 standard. E1.3.5. This standard is intended for the design of complete active fall protection systems. Therefore, it is recommended that this standard not be referenced on specific fall protection products. It is anticipated that this standard may be used to incorporate equipment components into the design of active fall protection systems prior to an acceptable product standard being created for the equipment component’s proper use. Acceptance of material supplied from outside of the United States. For equipment in which an ANSI standard does not exist, engineers can consider fall arrest equipment complying with EN, CSA, AU and NZ standards as acceptable alternatives after a review of the applicable foreign standard. 1 .3.6 This standard does not supersede the requirements of applicable occupational safety and pr o ve eri ca n N ation al d Am Sta n da rd Ap AMERICAN S OCIETY OF S AFETY E NGINEERS 9 ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems health regulations. Where the requirements in this standard differ from legislated requirements, the most conservative requirement shall be followed. 1 .3.7 In ANSI standards, “shall” is used to express a requirement, i.e., a provision that the user is obliged to satisfy in order to comply with the standard; “should” is used to express a recommendation or that which is advised but not required; and “may” is used to express an option or that which is permissible within the limits of the standard. Notes accompanying sections do not include requirements or alternative requirements; the purpose of the e-column accompanying a section is to separate from the text explanatory or informative material. Notes to tables and fi gures are considered part of the table or fi gure and may be written as requirements. Legends to equations and fi gures are considered requirements. 1 .4 Interpretations. Requests for interpretations of this standard shall be in writing and addressed to the Secretariat of this standard. 2. DEFINITIONS Please refer to ANSI/ASSE Z359.0, Definitions and Nomenclature Used for Fall Protection and Fall Arrest, for de fi nitions of terms used in this standard. 3. DRAWINGS AND SPECIFICATIONS 3.1 General. 3.1 .1 A fall protection system meeting the requirements of this standard shall have drawings and/or speci fi cations prepared by or under the direction of an engineer. 3.2 Sealing by a Professional Engineer. 3.2.1 If the system is designed by a professional engineer, the professional engineer who designs the system shall affi x his or her professional seal to each drawing and speci fi cation issued. The professional engineer shall be registered in the state or jurisdiction where the work is being performed. Ap pr ove e ri c a n N at i o n a l d Am Sta n da rd 10 AMERICAN S OCIETY OF S AFETY E NGINEERS ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems 3. 3 Req u i red I n form ati on . Drawings, speci fi cations, and instructions provided by the engineer shall include: 3. 3. 1 A statement de fi ning the type of system (fall arrest, travel restraint, etc.) and indicating that the design is in accordance with the requirements of this standard; 3. 3. 1 . 1 A drawing showing the layout of the system, including where it is located and the complete assembly of all components. In the case of a system that can be relocated, the layout shall depict the engineer’s expected typical installation and design assumptions; 3. 3. 1 . 2 A speci fi cation of the number, location, and quali fi cations (including minimum and maximum weights and training) of workers using the system; 3. 3. 1 . 3 Speci fi cations for all components, including sizes and minimum required breaking strengths. The speci fi cations shall reference applicable standards and/or fully specify the makes and models of the components. Where substitute materials are allowed or performance speci fi cations are provided, the speci fi cations shall adequately describe the acceptable substitutions or products, respectively; 3. 3. 1 . 4 E3.3.1.4 This section applies to products and materials that are not manufactured in accordance with an ANSI/ASSE Z359 standard. A description of any proof testing required before the system may be put into use; 3. 3. 1 . 5 Alternatively, guidelines under which it was intended for the system to be used can be provided. Information on the expected performance of the system, including the maximum arrest load (MAL), maximum loadings of all components, sags and de fl ections, deployment of energy absorbers, and the maximum arrest force (MAF). Where system performance may be affected by variable environmental conditions such as temperature, performance in worst-case conditions shall be described; In horizontal lifelines (HLLs), the greatest deflections occur at the highest temperature and the greatest forces occur at the lowest temperature. 3. 3. 1 . 6 3. 3. 1 . 7 pr o ve eri ca n N ation al d Am Sta n da rd Ap E3.3.1.6 A speci fi cation of any environmental limitations on the use of the fall protection system, such as chemical, temperature, radiation, or weather factors that may temporarily or permanently render the system unsafe to use; AMERICAN S OCIETY OF S AFETY E NGINEERS E3.3.1.7 11 ANSI/ASSE Z359.6-2009 American National Standard 3.3.1 .8 A description of the greatest required clearances for all permitted worker locations, connecting means, and full body harness combinations. Where a required clearance varies with environmental conditions, the worst-case value shall be speci fi ed; Specifications and Design Requirements for Active Fall Protection Systems E3.3.1.8 During a fall, harness effects or D-Ring slide are commonly taken into account in clearance calculations. The variable can vary by model. 3.3.1 .9 Instructions for assembly and installation. In the case of generic systems or a system that can be relocated, the instructions shall specify: 3.3.1 .9.1 The minimum required strength of the anchorages; 3.3.1 .9.2 The clearances required below the work- ing platform or anchorages; and 3.3.1 .9.3 Any safety precautions that shall be followed during the erection and dismantling of the system. 3.3.1 .1 0 Instructions for inspection, maintenance, and retirement of the system and all of its components, including how often inspection and maintenance are to be performed and a description of the quali fi cations required for persons performing these tasks; 3.3.1 .1 1 Instructions for safe access to, egress from, and use of the system; 3.3.1 .1 2 For fall arrest systems, a rescue plan or directions to the owner of the system or the employer of the workers using the system to develop and implement a rescue plan before the system is used. The engineer shall indicate the appropriate uses of the system or its anchorages during a rescue; 3.3.1 .1 3 A statement specifying: 3.3.1 .1 3.1 That the engineer who designed the system or an engineer with similar experience and quali fi cations shall be consulted before modifying the design; and 3.3.1 .1 3.2 Whether the system is intended to be generic or capable of being relocated, i.e., so that it may be used at multiple locations. 3.3.1 .1 4 For permanent systems, “as-constructed” Ap pr ove e ri c a n N at i o n a l d Am Sta n da rd 12 AMERICAN S OCIETY OF S AFETY E NGINEERS ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems drawings. The engineer shall state that the installation is in general accordance with the as-constructed drawings and speci fi cations; and 3.3.1 .1 5 Shall indicate how often the anchorages shall be recerti fi ed by the engineer designing the system or an engineer with similar experience and quali fi cations. E3.3.1.15. If the original design was performed by an engineer, an engineer or a qualified person under the supervision of an engineer can perform the recertification. If the original design was not performed by an engineer, an engineer should be involved in the recertification if this standard is to be used for that process.. 4. MATERIAL, EQUIPMENT, AND OTHER DESIGN REQUIREMENTS 4.1 Composition of Materials. Load-bearing com- ponents of active fall protection systems shall be composed of synthetic or metallic materials. Organic fi bers and materials may be used only for non-load-bearing components. 4.2 Ductility of Materials. Metallic or synthetic materials (with the exception of composite plastics such as fi berglass) shall have at least 1 0% elongation prior to failure in the environments to which they will be exposed. 4.3 Environmental Considerations. All compo- nents of an active fall protection system shall be speci fi ed to provide safe and durable service in the environment(s) where the system may be used. Environmental considerations include, but are not limited to, corrosion, chemical attack, weather, abrasion, and ultraviolet exposure. Additionally, all portions of anchorages which are permanently concealed from view shall be made from materials that have the necessary durability for the environment. E4.3 Designers should not assume that anchorages that are permanently concealed will last forever. At a minimum, the anchorages should be inspected as outlined in Sections 4.6.4 and 4.6.5. 4.4 Equipment. 4.4.1 General. Fall arrest equipment components used in systems designed in accordance with the requirements of this standard shall meet the requirements of the applicable ANSI/ASSE Z359 standard. Where an ANSI/ASSE Z359 standard does not exist for a particular component, suitable speci fi cations for manufacturing or purchasing the component shall be provided by the engineer. pr o ve eri ca n N ation al d Am Sta n da rd Ap AMERICAN S OCIETY OF S AFETY E NGINEERS E4.4.1 Care should be taken when considering how to use a piece of equipment. Warnings, such as a manufacturer specifically prohibiting the use of their product in a certain manner, should be heeded. An example of this prohibition is the 1) use of an SRL in a flat manner rather than on its side, or 2) use of an eyebolt in a manner that would allow it to be subjected to an out-of-plane load. 13 ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems 4.4.2 Compatibility. Equipment and hardware for all components of an active fall protection system shall be speci fi ed to provide compatible connections. Combinations of equipment from different manufacturers shall be permitted if the engineer is satis fi ed that the connections are compatible and that there is no dangerous interaction between them, e.g., loading of carabiner or snaphook gates to allow roll-out. 4.4.3 Energy Absorbers. 4.4.3.1 General. Energy absorbers, including per- sonal energy absorbers (PEAs), self-retracting lanyards (SRLs), and horizontal lifeline energy absorbers (HLLEAs), shall sacri fi cially dissipate the energy from a fall. They shall not release the energy that they have absorbed back to the system or worker. Springs, bungees, and other elastic devices shall not be considered energy absorbers under this standard. Elastic mechanisms within energy absorbers may be used to buffer, without permanent elongation, thermal shrinkage or travel restraint forces. 4.4.3.2 Selection of Personal Energy Absorbers. When selecting personal energy absorbers: 4.4.3.2.1 When the free fall distance allowed by the system is 6 feet (1 .83 m) or less and worker weight is 31 0 lbs (1 41 kg) or less, energy absorbers and energy-absorbing lanyards, where used, shall meet the requirements of ANSI/ASSE Z359.1 ; or 4.4.3.2.2 The engineer shall: 4.4.3.2.2.1 Use dynamic analysis, energy analysis, or testing and interpolation analysis to ensure that the impact forces on the worker’s body do not exceed 1 ,800 pounds (8 kN); or 4.4.3.2.2.2 Ensure that the maximum free fall distance allowed by the system does not exceed in the following formula: h Max = where w X Max E4.4.3.2.2.2 Specialized energy absorbers and energy-absorbing lanyards may be used to control the impact forces when devices meeting the requirements of ANSI/ASSE Z359.1 do not provide adequate protection. Specialized energy-absorbing lanyards meeting the requirements of ANSI/ASSE Z359.1 are AMERICAN S OCIETY OF S AFETY E NGINEERS Ap pr ove e ri c a n N at i o n a l d Am Sta n da rd 14 FAvg – w hMax ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems = maximum free fall distance permitted by the system, ft. manufactured for larger free falls and workers whose weight exceeds 310 lbs (141 kg). When used, these devices shall keep the impact forces below 1, 800 lbs (8 kN) for the maximum worker mass and free fall allowed by the system. h Max FAvg = average deployment force of the PEA or SRL, lbs, in accordance with Section 6.3.3.2 or 6.3.4.2, as applicable = weight of worker, lbs, in accordance with Section 6.3.2 w XMax XMax is often identified as the deceleration distance on an equipment label. = maximum rated extension of the PEA, ft. 4.4.4 Self-Retracting Lanyards. 4.4.4.1 Travel Restraint Systems. SRLs shall not be used in travel restraint systems unless the length of the lifeline on the drum of the SRL will not permit the worker to reach the hazard even when fully deployed. 4.4.4.2 Fall Arrest Systems. E.4.4.4.2 See Appendix A. 4.4.4.2.1 Flexible Anchorage Systems. E4.4.4.2.1 When an SRL is used in a flexible anchorage system such as an HLL, the engineer should consider the dynamic interaction between the locking mechanism and the natural frequency of the flexible anchorage system. This should be considered so that the SRL does not unlock during the rebound of the system after fall arrest or, in a system used by multiple workers simultaneously, as a result of subsequent falls. A simple drop test may consist of an SRL attached to center of 60 foot undampened cable between two substantial anchorage points. Alternatively, the same test on the cable using HLL energy absorber as specified by the HLL manufacturer. 4.4.4.2.2 Systems Where Free Fall is Limited to the Self-Retracting Lanyard’s Activation Distance. When the fall arrest system anchors the SRL suffi ciently above the worker’s dorsal D-Ring so that the free fall allowed by the system equals the SRL’s activation distance, all SRL types meeting the requirements of ANSI/ASSE Z359.1 may be used. 4.4.4.2.3 Systems Where Free Fall Exceeds the Self-Retracting Lanyard’s Activation Distance. Where the conditions of Section 4.4.4.2.2 cannot be met, only SRLs with integral PEAs may be used. pr o ve eri ca n N ation al d Am Sta n da rd Ap AMERICAN S OCIETY OF S AFETY E NGINEERS 15 ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems 4.4.5 Lanyards. 4.4.5.1 Lanyards in Travel Restraint Systems. PEAs may be used in lanyards in travel restraint systems, provided that the engineer has determined whether the restraint force could cause the PEA to deploy and, if so, that such deployment will not permit the worker to reach the fall hazard. 4.4.5.2 Lanyards in Fall Arrest Systems. Except as allowed by Section 4.4.3.2 or 5.4.2, lanyards in fall arrest systems shall meet the requirements of ANSI/ASSE Z359.1 . 4.4.6 Full Body Harnesses. Full body harnesses shall meet the requirements of ANSI/ASSE Z359.1 . Stretch out used in clearance calculations in Section 7.2.4 of this standard shall account for stretching of the type(s) of full body harnesses permitted for use with the fall arrest system. 4.4.7 Fall Arresters. Fall arresters used on vertical lifelines (VLLs) and ladder-climbing systems shall meet the requirements of ANSI/ASSE Z359.1 . 4.4.8 Horizontal Lifeline Energy Absorbers. 4.4.8.1 Travel Restraint Systems. HLLEAs may be used in travel restraint systems, provided that the engineer has determined that the restraint forces will not cause the HLLEAs to deploy and ensures that the de fl ection of the cable in combination with other deformations of the restraint system, will not permit the worker(s) to reach the fall hazard. The restraint system shall meet the requirements of Section 4.4.8.2. 4.4.8.2 Fall Arrest Systems. HLLEAs shall be used only to control or reduce the MAL, and only if the engineer has ensured that the increased clearance requirements can be met. E4.4.8.2 See Appendix A. The maximum span in any HLL where HLLEAs are used should not be greater than L Max in the following equation: 2 10.76 Avg -4 Max = 4.6 16 L T Mw where LMax = maximum span, ft. Ap pr ove e ri c a n N at i o n a l d Am Sta n da rd 16 AMERICAN S OCIETY OF S AFETY E NGINEERS ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems TAvg = average deployment force of the HLLEA, lbs, in accordance with Section 6.3.6.3 M = “lumping factor” for the maximum number of workers that may attach themselves to one span of the HLL at any one time, as specified in Section E6.3.7.2 w = weight of one worker, lbs, in accordance with Section 6.3.2 4.5 Other Design Requirements for Travel Restraint Systems. In addition to ensuring compli- ance with the applicable safety criteria in Section 5, the engineer shall ensure that the worker cannot reach and fall into any open hole or off the edge of the working platform. Special attention shall be paid to the use of fl exible anchorage systems, such as HLLs, that may in fl uence how short the lanyard or lifeline needs to be to meet this requirement. 4.6 Other Design Requirements for Fall Arrest Systems. 4.6.1 General. In addition to the applicable safety criteria outlined in Section 5, the requirements in Sections 4.6.2 and 4.6.3 shall apply. 4.6.2 Rescue. To satisfy the requirements of Sec- tion 3.3.1 .1 2, the design shall take into consideration the potential uses of and loads on the fall arrest system, in order to facilitate the prompt rescue of workers who may fall while attached to the system. 4.6.3 Anchorage for Suspended Equipment Operations. The fall arrest anchorage requirements for individuals working from suspended equipment shall be as speci fi ed in ANSI/IWCA I-1 4.1 and ASME A1 20.1 4.6.4 Inspection of Components Not Addressed by a Manufacturer’s Requirements. For compo- nents not addressed by a manufacturer’s inspection requirements, the components shall be visually inspected, as a minimum, in a manner and frequency speci fi ed by the engineer designing the active fall protection system. The frequency of inspection shall not exceed one year. pr o ve eri ca n N ation al d Am Sta n da rd Ap AMERICAN S OCIETY OF S AFETY E NGINEERS 17 ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems 4.6.5 Recerti fi cation of Active Fall Protection Systems. Active fall protection systems shall be E4.6.5. If the original design was performed by an engineer, an engineer or a qualified person under the supervision of an engineer can perform the recertification. If the original design was not performed by an engineer, an engineer should be involved in the recertification if this standard is to be used for that process. thoroughly reviewed by an engineer at a frequency to be determined by the original design or other similarly quali fi ed engineer but not to exceed fi ve years. This recerti fi cation process shall include a review of the original documents prepared for the system and their continued applicability. As a minimum, the following criteria shall also be considered and the result of the certi fi cation shall result in a report or set of documents outlined in Section 3.3.1 . • Changes in the hazards and tasks that are addressed by the active fall protection system. • Changes in regulations, standards or other factors affecting the active fall protection system. • Feedback from a representative sample of the competent persons and authorized persons of the fall protection system. 5. SAFETY CRITERIA 5.1 Speci fi ed Loads. The load effects on each component of an active fall protection system shall be determined for the following loads: E5.1 The symbols identified in Section 5.1 appear in Section 5.2.3. 5.1 .1 D — Dead loads from the static weight of materials used in the system and, as applicable, from the structure to which it is attached. 5.1 .2 A — Fall arrest or travel restraint loads applied to the system determined in accordance with Section 6. The applied loadings from energy absorbers shall be determined in accordance with Sections 6.3.3.1 , 6.3.4.1 , 6.3.5, and 6.3.6.2, as applicable. E5.1.2 This can also be taken as the impact of the dynamic loading applied to the building or structure resulting from the activation of the active fall protection system attached; as specified by the engineer designing the system. 5.1 .3 L — Live loads due to the intended use and occupancy of the building or structure to which the active fall protection system is attached. Live loads shall be as speci fi ed in the International Building Code. 5.1 .4 Q — Wind, earthquake, or other loads that may be applied to the structure or building to which the active fall protection system is attached. These loads shall be as speci fi ed in the International Building Code. 5.1 .5 AMERICAN S OCIETY OF S AFETY E NGINEERS Ap pr ove e ri c a n N at i o n a l d Am Sta n da rd 18 T — In fl uences resulting from temperature ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems changes, shrinkage or creep of component materials, or differential settlement. Temperature changes shall be as speci fi ed in the International Building Code. Shrinkage or creep shall be in accordance with the applicable design code for the materials used in the construction of the active fall protection system or the structure to which it is attached. 5.2 Strength. 5.2.1 General. All components and subsystems of an active fall protection system, and the structure to which it is attached, shall have suffi cient strength and stability such that: R ≥ F* where R = the factored resistance of the component or subsystem F* = the worst-case factored effect of the applied loads on the component or subsystem 5.2.2 Determination of Factored Resistance. 5.2.1 .1 General. Factored resistance shall be determined as follows: R = ØU where Ø = the capacity-reduction factor U = the ultimate strength of the component or subsystem 5.2.2.2 Factored Resistance for Common Construction Materials. R, Ø, and U for common construction materials used in the construction of the active fall protection system or the structure to which it is attached shall be determined in accordance with the requirements of the applicable design code(s) in Section 9. 5.2.2.3 Factored Resistance for Materials Not Covered by an ANSI Limit States Design Code. pr o ve eri ca n N ation al d Am Sta n da rd Ap AMERICAN S OCIETY OF S AFETY E NGINEERS 19 ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems Where an ANSI limit states design code does not exist for a material used in the construction of a fall arrest system: 5.2.2.3.1 The ultimate strength, U, of a component shall be based on testing of the component or calculation of the strength of the component using the known strength of the material; and 5.2.2.3.2 The capacity-reduction factor, Ø, shall be as follows: 5.2.2.3.2.1 For brittle materials such as fi berglass, 0.3; 5.2.2.3.2.2 For synthetic ropes and webbing, 0.5; 5.2.2.3.2.3 For materials that exhibit at least 1 0% elongation prior to failure at a yield stress that is between 60 and 80% of the ultimate stress, 0.6; and 5.2.2.3.2.4 For wire ropes meeting the requirements of ASTM A1 023 (applied to the terminated strength of the wire rope), 0.75 (applied to the terminated strength of the wire rope). 5.2.3 Determination of Factored Load Effects. The factored load for each component of an active fall protection system shall be the worst-case force effect, F*, using the following formula for all possible combinations of applied loading: (F* = α DD * + ? ( α A A * + α L L* + α QQ* + αTT*) where D*, A *, L*, Q *, and T* = the forces carried by each component due to the applied loads D, A , L , Q, and T described in Section 5.1 α = the load factor for the speci fi c type of loading, as follows: αD = 1 .25 or, when the dead load opposes the effect of A, 0.85 E5.2.3 See Appendix A. 1 ) Unlike the limit states design methods described in the International Building Code, the load factors in this section are applied to the forces carried by each component, rather than to the load resisted by the system. This is necessary to ensure a consistent safety factor throughout the system. For example, in an HLL system, the tension in the HLL increases in much lower proportion to the increase in applied loading, and where HLL energy absorbers are employed, there may be no increase in lifeline tension due to factoring the applied load. 2) In systems where the majority of the load effect is due to the fall arrest or travel-restraint force, A, engineers may choose to simplify their determination of F* by using α D = α A = α L = α Q = αT = 1. 5, which is often only slightly conservative. αA = 1 .5 αL = 1 .5 or, when the live load opposes the effect Ap pr ove e ri c a n N at i o n a l d Am Sta n da rd 20 AMERICAN S OCIETY OF S AFETY E NGINEERS ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems of A, 0 αQ = 1 .5 αT = 1 .25 or, when thermal stresses change the HLL pre-tension, 1 .5 ? = the load combination factor, as follows: ? ? = 1 , where only A is applied ? = 0.7, if A acts in combination with either L or Q ? = 0.6, if A acts in combination with both L and Q ? ? ? 5.3 Swing Falls. In fall arrest systems, anchor- ages shall be located directly above the worker(s) to eliminate swing falls, wherever it is reasonably practical to do so. Where it is not reasonably practical to prevent swing falls, the swing-drop distance shall not exceed 4.0 ft (1 .22 m) (see Figure 1). E5.3 See Appendix A. 5.4 Forces on the Worker’s Body. 5.4.1 Travel Restraint Systems. Where a worker is using a full body harness in a travel restraint system, the force on the worker’s body shall not exceed 400 lbs (1 .78 kN). E5.4.1. Users ofthis standard are encouraged, where possible, to design anchorages for fall restraint as if they were fall arrest anchorages. Additionally, it is recommended that energy absorbing lanyards are considered in the equipment specification. These precautions would provide some level of protection in the case of a system misuse. 5.4.2 Fall Arrest Systems. 5.4.2.1 Maximum Arrest Force. The MAF experienced by each worker using a fall arrest system shall not exceed 1 ,800 lbs, (8.0 kN) except that when PEAs or SRLs are omitted in accordance with Section 5.4.2.3, the MAF shall not exceed 1 ,800 lbs (8.0 kN). E5.4.2.1. See Appendix A. 5.4.2.2 Forces Applied to the Full Body Harness. In a fall arrest system, a worker shall wear a full body harness and be attached to the system at the dorsal D-Ring. The only permitted exception shall be for ladder-climbing systems, which may be used with a sternal attachment when the free fall distance is limited to 1 8 inches (0.46 m) or less, or for harnesses equipped with a front-mounted attachment element for fall arrest, which shall be used only as part of a personal fall arrest system pr o ve eri ca n N ation al d Am Sta n da rd Ap AMERICAN S OCIETY OF S AFETY E NGINEERS 21 ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems that limits the maximum free fall distance to two feet (0.61 m) and limits the maximum arrest force to 900 pounds (4.0 kN). 5.4.2.3 Use of Personal Energy Absorbers or Self-Retracting Lanyards. Fall arrest systems shall use PEAs meeting the requirements of Section 4.4.3.2 or SRLs meeting the requirements of Section 4.4.4.2.3 except: E5.4.2.3 PEAs are often incorporated into lanyards but may also be located elsewhere in the fall arrest system, e.g., as part of an anchorage connector or permanently attached to the full body harnesses. 5.4.2.3.1 In accordance with Section 4.4.4.2.2; 5.4.2.3.2 For ladder-climbing systems where the free fall is limited to 1 8 inches (0.46 m) or less; or 5.4.2.3.3 When elimination of energy absorbers is required to stop a fall within very limited available clearances. 5.5 Clearance. 5.5.1 Travel Restraint Systems. In travel restraint systems, consideration of clearance is not required. 5.5.2 Fall Arrest Systems. In fall arrest systems, the required clearance, calculated in accordance with Section 7.2, shall be less than or equal to the available clearance for the system. For the purposes of clearance calculations, the applied loadings from energy absorbers shall, as indicated in Sections 6.3.3.2, 6.3.4.2, and 6.3.6.3, be applicable. 5.6 Stability of Free-Standing Systems. 5.6.1 General. Free-standing systems may only be used on surfaces with a downward slope of less than 5º toward any side or opening where a worker could fall. E5.6.1 A 5º slope is equivalent to approximately a 5.6.2 Manufactured Products. In lieu of a rigor- E5.6.2 At a minimum, the engineer should request ous analysis of overturning and sliding provided below, an engineer can review manufacturer data and literature prior to the speci fi cation of a product. 1” vertical to 12” horizontal slope. the following information from the manufacturer of a product that will be used as a free-standing system: • The surfaces on which the product has been tested. Ap pr ove e ri c a n N at i o n a l d Am Sta n da rd 22 AMERICAN S OCIETY OF S AFETY E NGINEERS ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems • Potential performance variations for possible surface contaminants. • The uniform or concentrated loads the product will apply to the structure during erection, use and dismantling. • The required edge distance or edge conditions, such as a parapet, required by the product. • Other cautions or instructions that are needed for proper performance of the system. 5.6.3 Overturning of Counterbalanced Systems. Where an active fall protection system is freestanding or counterbalanced and is not anchored to a solid support, the system shall have a factor of safety against overturning to resist the worst-case combination of fall arrest loading and con fi guration of the system as follows: 5.6.3.1 Not less than 4.0; 5.6.3.2 Not less than 2.0 where the design prevents change to the counterbalance mass or movement of the fulcrum point i.e. where the counterbalance weights are bolted together and the fulcrum point is bolted to the free-standing system; 5.6.3.3 Not less than 1 .5 where: 5.6.3.3.1 The design prevents change to the counterbalance mass or movement of the fulcrum point i.e. where the counterbalance weights are bolted together and the fulcrum point is bolted to the freestanding system; and 5.6.3.3.2 There is a minimum 4.0 factor of safety when the energy required to bring the system to incipient tipping is compared to the total energy generated by the worst-case fall(s) that could occur. 5.6.4 Sliding of Ballasted Systems. Where an active fall protection system relies on friction between a ballasted anchor and its supporting surface, instead of being anchored to a solid support, the ballasted anchor shall have a factor of safety against sliding of not less than 3.0 to resist the worst-case combination of fall arrest loading and con fi guration of the system. The following requirements shall also apply: pr o ve eri ca n N ation al d Am Sta n da rd Ap AMERICAN S OCIETY OF S AFETY E NGINEERS 23 ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems 5.6.4.1 The coeffi cient of kinetic friction used in calculating the resistance to sliding shall be determined by fi eld testing in the direction(s) of potential loading at the site or similar conditions where the ballasted anchor will be used and shall simulate the worst-case weather conditions that may affect the coeffi cient of friction; and 5.6.4.2 Unless any applicable stops or parapet walls are analyzed or tested to prove that they are strong enough to prevent the ballasted anchor from sliding to an edge and falling, the ballasted anchor shall be installed a minimum of 1 0.0 ft from any edge of the surface it might fall from if it were to slide while resisting the fall arrest loading. 6. FALL PROTECTION SYSTEM LOADS AND FORCES 6.1 General. The force, A , applied to an active fall protection system to stop or prevent falls shall be determined in accordance with Sections 6.2 and 6.3. 6.2 Travel Restraint Systems. 6.2.1 Maximum Arrest Force and Maximum Arrest Load. The loads and forces in all components of a travel restraint system due to the worst-case impact from worker(s) being stopped short of the fall hazard shall be determined in accordance with Sections 6.2.2 and 6.2.3. 6.2.2 Level Surfaces. For surfaces that slope less than 5%: E6.2.2 Designers should be aware that fall arrest can result if workers have an improperly adjusted lifeline, lanyard, or SRL that is long enough to allow a fall to occur. 6.2.2.1 Temporary restraint anchorages shall be designed using static analysis with A = 400 lbs (1 .78 kN) per worker attached to the anchorage; and 6.2.2.2 Permanent restraint anchorages shall be designed for fall arrest, determined in accordance with Section 6.3. 6.2.3 Sloping Surfaces. Temporary or permanent restraint anchorages intended to prevent workers from falling off the bottom edge of a downward slop- Ap pr ove e ri c a n N at i o n a l d Am Sta n da rd 24 AMERICAN S OCIETY OF S AFETY E NGINEERS ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems ing surface shall be designed for the force required to stop the worst-case slides down the slope. Forces may be determined using one of the methods outlined in Sections 8.3.2 to 8.3.6, but shall be not less than what is required by Section 6.2.2. 6.3 Fall Arrest Systems. 6.3.1 Maximum Arrest Force and Maximum Load. The loads and forces in all components of a fall arrest system shall be determined, for the worst-case fall, by one of the methods outlined in Sections 8.3.2 to 8.3.6. 6.3.2 Design Weight of Workers. For an analysis in accordance with Sections 5.2 and 6.3, the design weight, w, shall be the mass of the heaviest worker permitted on the system, including all tools and equipment, but not less than 31 0 pounds (1 41 kg). E6.3.2 See Appendix A. 6.3.3 Deployment Force of Personal Energy Absorbers and Energy-Absorbing Lanyards. 6.3.3.1 FMax (for strength calculations). PEAs and energy-absorbing lanyards meeting the requirements of ANSI/ASSE Z359.1 shall be assumed to deploy at a force of FMax = 900 pounds (4.0 kN), or, in environments where they may become wet and frozen, at a force of FMax = 1 ,800 lbs (8.0 kN). Where a specialized PEA is required by the design, as permitted by Section 4.4.3.2, the device shall be assumed to deploy at the maximum force speci fi ed by its manufacturer, but not less than 900 lbs (4.0 kN). 6.3.3.2 FAvg (for clearance calculations). PEAs and energy-absorbing lanyards shall be assumed to deploy at the minimum average force speci fi ed by their manufacturers. In the absence of information from the manufacturer, PEAs meeting the requirements of ANSI/ASSE Z359.1 may be assumed to deploy at FAvg = 0.8 x FMax. 6.3.4 Impact Force of Self-Retracting Lanyards. 6.3.4.1 General. SRLs may be used only in accor- dance with Section 4.4.4.2.2. The maximum impact force shall be determined using one of the methods in Sections 6.3.4.2 to 6.3.4.4. pr o ve eri ca n N ation al d Am Sta n da rd Ap AMERICAN S OCIETY OF S AFETY E NGINEERS 25 ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems 6.3.4.2 Dynamic Analysis and Energy Analysis. When a fall arrest system is analyzed in accordance with Section 8.3.2 or 8.3.3, the MAF shall be calculated using the assumption that the device does not stretch and does not dissipate any energy after it has locked off. 6.3.4.3 Static Analysis. When a fall arrest system is analyzed in accordance with Section 8.3.4, the MAF shall be the maximum impact force speci fi ed by the manufacturer for the free fall permitted by the system. 6.3.4.4 Testing and Interpolation Analysis. The MAF shall be the measured force(s) when a fall arrest system is tested in accordance with Section 8.3.5. 6.3.5 Deployment Force of Horizontal Lifeline Energy Absorbers. 6.3.5.1 General. When HLLEAs are used, the de- ployment forces to be used in strength and clearance calculations shall be as speci fi ed in Sections 6.3.5.2 and 6.3.5.3. 6.3.5.2 TMax (for strength calculations). HLLEAs shall be assumed to deploy at the maximum force speci fi ed by their manufacturer. 6.3.5.3 TAvg (for clearance calculations). HLLEAs shall be assumed to deploy at the minimum average force speci fi ed by their manufacturer, or, when the total energy consumed by an HLLEA at full deployment is speci fi ed by the manufacturer, as follows: U TAvg = X Max HEAMax where TAvg = average deployment force, lbs UMax = total energy absorbed by the HLLEA at full deployment, lbs•ft. XHEAMax = maximum available deployment of the HLLEA, ft. Ap pr ove e ri c a n N at i o n a l d Am Sta n da rd 26 AMERICAN S OCIETY OF S AFETY E NGINEERS ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems 6.3.6 Multiple-Worker Falls. 6.3.6.1 General. For systems that may allow more than one worker to be attached to an anchorage, anchorage connector, or anchorage subsystem, the effect of possible simultaneous or sequential impacts shall be accounted for in determining the MAF, MAL, and clearances. In HLLs, unless the design of the system or control of the work procedures reliably precludes the gathering of workers at a single point, all workers allowed within a single span shall be assumed to fall at the same point on the system. In multiple-span HLLs, the simultaneous falling of workers on different spans is considered highly improbable. It shall not be necessary to consider the possibility of simultaneous falls unless there is some unusual circumstance, such as a multiplespan HLL above a single-span work surface that, in the event of a collapse, would result in impacts on more than one span within a very short time. 6.3.6.2 Equivalent Lumped Mass. In the absence of more rigorous analytical methods, the effect of multiple-worker falls may be modeled by: E6.3.6.2 See Appendix A. Another factor to consider for the lumping factor is whether the fall is due to the surface upon which the work occurs. A collapsible surface involves a situation where the integrity of the surface upon which the employees are working leads to a potential fall hazard. Examples: employees working on a suspended platform for exterior building maintenance; maintenance on a roof with significant deterioration in which there is a hazard with the employees falling through the roof surface. 6.3.6.2.1 Lumping the masses of the falling workers into a single mass that is the product of the mass of the design worker, m, de fi ned in Section 6.3.2, and the number of falling workers. 6.3.6.2.2 Lumping PEAs or SRLs, where used, in parallel into a single device using F Max or FAvg as applicable and de fi ned in Section 6.3.3 or 6.3.4. For two workers attached, it shall be assumed that they impact at the same time. For each subsequent worker attached, the weight of the design worker shall be added to the two workers impact. pr o ve eri ca n N ation al d Am Sta n da rd Ap AMERICAN S OCIETY OF S AFETY E NGINEERS E6.3.6.2.2 For example where the MAF for the PEA is 900 lbs. (4 kN) and the maximum worker weight is 220 lbs. (100 kg) and four workers are attached, it should be assumed that two workers are suspended and two workers fall and impact the system. The resulting force would be 900+900+220+220 = 2, 240 lbs. (10 kN). If used as a factor, the effective 27 ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems lumping factor would be 2,240/900 = 2.49. E6.3.6.3. In some cases, 6.3.6.3 Sequential Falls on Horizontal Lifeline Systems. On HLLs only, the load effect, A , for mul- energy absorbers, either connected to the lanyard or horizontal lifeline, may bottom out due to the additional energy applied by the increased free fall. 6.3.7 Horizontal Systems. The engineer shall de- E6.3.7 Engineers should take into consideration for tiple-worker falls may be determined by loading the HLL, pre-sagged by the deployment of any applicable HLLEA due to the earlier falls, with the dead weight of all prior fallen workers, in accordance with Section 6.3.2, plus the fall arrest impact from the last worker. The free fall of and clearance required for the last worker will be greater than for the prior workers because the HLL has been pulled downward by the prior falls and permanent HLL sag due to deployment of an HLLEA. termine worker locations where falls would result in the least difference between required and available clearances and cause the maximum forces in the system components. Engineers shall, at a minimum, determine the performance of the system when a fall occurs on the shortest span and the longest span in the system. Engineers shall also determine the variation in system performance due to temperature or other environmental variations, if applicable. HLLs: a) The maximum transverse forces on system anchorages occur when workers fall while immediately adjacent to end or intermediate anchorages; and b) The greatest HLL tension and total-fall distance for each span of the system will occur when a fall occurs midway between supports. 7. CLEARANCES FOR FALL ARREST SYSTEMS 7.1 Clearance Reference. Clearances shall be ref- erenced to the working platform (CP), except when it may be necessary for portable or temporary systems to reference clearances to the anchorage (CA) (see Figure 2). 7.2 Required Clearance. 7.2.1 General. Clearance requirements shall ac- count for the worst-case total of free fall distance, deceleration distance, stretch out, applicable swingdrop distance, and the safety margin speci fi ed in Sections 7.2.2 to 7.2.6 (see Figures 1 , 2, and 3). In multiple-worker systems that are analyzed in accordance with Section 6.3.6.2, the required clearance shall be adjusted in accordance with Section 7.2.6. 7.2.2 Free Fall Distance. Ap pr ove e ri c a n N at i o n a l d Am Sta n da rd 28 AMERICAN S OCIETY OF S AFETY E NGINEERS ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems 7.2.2.1 General. Free fall is the unimpeded fall dis- tance of the worker. Free fall ends when all slack has been taken out of the fall arrest system so that further displacement of the worker will be resisted by forces developed in the system. Free fall will include any applicable lanyard or HLL or VLL slack, or activation distance (see Figures 2, 4, and 5). 7.2.2.2 Lanyard or Lifeline Slack. The lanyard or lifeline slack shall be taken as the height of the worker’s D-Ring above the opposite end of the lanyard or lifeline, plus the length of the lanyard or lifeline. Where the worker’s D-Ring is below the opposite end of the lifeline or lanyard, the difference in height shall be negative (see Figures 4 and 5). 7.2.2.3 Activation Distance. The activation or lock-off distance of a fall arrester or SRL shall be included in the free fall distance (see Figure 5). 7.2.2.4 Horizontal Lifeline Slack. In HLL systems, the change in sag between the initial sag and the cusp sag shall be included in the free fall distance (see Figure 6). 7.2.3 Deceleration Distance. 7.2.3.1 General. Deceleration distance is the distance over which a fall arrest system reacts to bring a falling worker to a complete stop. Deceleration distance shall include any applicable stretch of lifelines and lanyards, the maximum anchorage system de fl ection, and deployment of PEAs and SRLs (see Figure 2). 7.2.3.2 Stretch of Lanyards. Signi fi cant dynamic stretch of SRLs and conventional lanyards shall be included in the deceleration distance. Where the stretch is known to be less than 2 inches, it may be ignored (see Figure 2). 7.2.3.3 Maximum Anchorage System De fl ection (MASD). The dynamic displacement of the anchor- age, dynamic stretch of a vertical lifeline, or dynamic sag of an HLL shall be included in the deceleration distance (see Figures 2 and 6). 7.2.3.4 Deployment of Personal Energy Absorbers and Self-Retracting Lanyards. In fall arrest pr o ve eri ca n N ation al d Am Sta n da rd Ap AMERICAN S OCIETY OF S AFETY E NGINEERS E7.2.3.4 See Appendix A. 29 ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems systems that use PEAs or SRLs, the deceleration distance shall include the deployment distance of these devices (see Figure 2), as follows: 7.2.3.4.1 PEAs may be assumed to fully deploy; 7.2.3.4.2 Deployment of PEAs or SRLs may be accurately determined using dynamic analysis, energy analysis, or testing and interpolation analysis in accordance with Section 8.3.2, 8.3.3, or 8.3.5, respectively; or 7.2.3.4.3 if static analysis is used (as allowed by Section 8.3.4), deployment of PEAs or SRLs may be estimated using the following formula: X PEA = wh FAvg - w Where XPEA = deployment of the PEA or SRL, ft. w = weight of falling worker, lbs, in accordance with Section 6.3.2 h = the free fall, ft. FAvg = average deployment force of the PEA or SRL, lbs, in accordance with Section 6.3.3.2 or 6.3.4.2, as applicable. The engineer shall review the manufacturer’s literature to determine the maximum deployment of the PEA that he or she has speci fi ed for the fall arrest system or shall otherwise assume 3.5 ft (1 .07 m) worst-case deployment. 7.2.4 Stretch Out. The required clearance shall include allowance for stretch out, including harness stretch, and reaction of the worker’s body to the deceleration forces, including applicable lengthening of the worker’s body if falling from a kneeling or lying position (see Figure 3). The type of full body harness being worn by the workers is a major component of stretch out. Harness stretch data shall be obtained from the harness manufacturer or shall be determined by testing harness performance at the MAF allowed by the fall arrest system. If the engineer is unable to obtain harness stretch infor- AMERICAN S OCIETY OF S AFETY E NGINEERS Ap pr ove e ri c a n N at i o n a l d Am Sta n da rd 30 E7.2.4 See Appendix A. ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems mation or does not otherwise specify and control the type(s) of full body harnesses being used, a minimum of 2.5 ft (0.76 m) shall be assumed for the harness contribution to stretch out. 7.2.5 Swing-Fall Distance. The required clearance shall include an allowance for any applicable swing-fall distance (see Figure 1). 7.2.6 Safety Margin. 7.2.6.1 Rigid Anchorage Systems. The safety margin, E, for rigid anchorage systems (see Figure 2) shall be not less than 2.0 ft (0.61 m). 7.2.6.2 Flexible Anchorage Systems. The safety margin, E, for fl exible anchorage systems (see Figure 2) shall be not less than the value given by the following formula: E7.2.6.2 See Appendix A. E = 0.6 + CMASD x MASD (ft) where CMASD depends on the method used to determine the maximum anchorage system de fl ection (MASD), as follows: CMASD = 0.30 for static analysis in accordance with Section 8.3.4 CMASD = 0.1 0 for dynamic analysis or energy analy- sis in accordance with Section 8.3.2 or 8.3.3 CMASD = 0.05 for testing and interpolation analysis in accordance with Section 8.3.5 7.2.7 Clearance for Equivalent Lumped-Mass Simulation of Multiple-Worker Falls. Where a fl exible anchorage system providing protection for multiple workers has been analyzed using an equivalent lumped mass as de fi ned in Section 6.3.7.2, the required clearance calculated for the equivalent lumped mass shall be increased to account for the increased total of free fall and deceleration distance seen by the last worker to fall. In the absence of other proven methods, the following formula may be used to calculate the required clearance: pr o ve eri ca n N ation al d Am Sta n da rd Ap AMERICAN S OCIETY OF S AFETY E NGINEERS E7.2.7 See Appendix A. C, CLM, and C1 are the applicable CP or CA values, depending on whether the clearance is specified below the platform or below the anchorage. 31 ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems C = 1 .6C LM – 0.6C1 where C = clearance for the last worker to fall CLM = required clearance for the equivalent lumpedmass fall C1 = required clearance for a single-worker fall 8. DESIGN ASSUMPTIONS AND ANALYTICAL METHODS 8.1 Elasticity of Ropes. 8.1 .1 Wire Ropes. Wire ropes may be assumed to behave in a linear elastic manner, using the elastic modulus recommended by the manufacturer and in accordance with the grade and construction of the wire rope. 8.1 .2 Synthetic Ropes. Synthetic ropes may be assumed to behave in a linear elastic manner. In the absence of more accurate analytical methods, the engineer shall use an elastic modulus that gives the correct stretch (+/- 5%) at the greatest MAF or MAL to which the rope will be subjected. The stretch properties of the rope shall be determined by testing or shall be detailed in information supplied by the manufacturer. 8.2 Horizontal Lifelines Sags. HLL sags due to pretension may be determined using catenary or parabolic equations. E8.2 For all sags greater than or equal to the cusp sag (SC), the HLL may be idealized as straight-line chords, ignoring the slight sags that occur because of its self-weight (see Figure 6). 8.3 Analytical Methods. 8.3.1 General. The analytical methods described in Sections 8.3.2 to 8.3.6 may be used to determine the performance of active fall protection systems. 8.3.2 Dynamic Analysis. Dynamic analysis may be used on all active fall protection systems. 8.3.3 Energy Analysis. Energy analysis may be used on all active fall protection systems. Ap pr ove e ri c a n N at i o n a l d Am Sta n da rd 32 AMERICAN S OCIETY OF S AFETY E NGINEERS ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems 8.3.4 Static Analysis. 8.3.4.1 General. Static analysis may be used only on active fall protection systems where the requirements of Section 8.3.4.2 or 8.3.4.3 are met, i.e., so that the MAF or restraint force applied to the system is known. 8.3.4.2 Travel Restraint Systems. In travel restraint systems, static analysis may be used only if the requirements of Section 6.2.2 are met, i.e., so that the force speci fi ed in that section is applicable. 8.3.4.3 Fall Arrest Systems. In fall arrest systems, static analysis may be used only when all of the following conditions can be met: E8.3.4.3 See Appendix A. 8.3.4.3.1 PEAs or SRLs are used to control the MAF; 8.3.4.3.2 The free fall distance for any worker attached to the system is less than h Max, as calculated in Section 4.4.3.2; and E8.3.4.3.2 In systems used by multiple workers simultaneously, the free fall of the last worker to fall in a sequential fall is used for comparison to the allowable hMax. In the absence of more rigorous methods, the free fall of the last worker may be taken as the free fall of the first worker plus the maximum anchorage system displacement to arrest a lumped-mass fall of all workers prior to the last worker. 8.3.4.3.3 In HLL systems that incorporate HLLEAs, E8.3.4.3.3 The following condition should be considered in HLL systems that incorporate HLLEAs. The total available deployment of all HLLEAs used in the system should be greater than XHEAMin as defined below: the engineer shall verify that the HLLEA does not completely deploy. If the HLLEA does completely deploy, other methods are required to accurately determine the peak forces in the HLL, which will be greater than the deployment force of the HLLEA. X HEAMin = 1.5 1 1- MFAvg 2TAvg 2 -1 L where XHEAMin = the minimum required total deployment of all HLLEAs used in the system, ft. M = the “lumping factor” for the maximum number of pr o ve eri ca n N ation al d Am Sta n da rd Ap AMERICAN S OCIETY OF S AFETY E NGINEERS 33 ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems workers that may attach to one span of the HLL at any one time, in accordance with Section E6.3.7.2 FAvg = the average deployment force of the PEA or SRL, lbs, in accordance with Section 6.3.4.2 TAvg = the average deployment force of the HLLEA, lbs, in accordance with Section 6.3.6.3 L = the maximum span of the HLL, ft. 8.3.5 Testing and Interpolation Analysis. Forces and clearance requirements for active fall protection systems may be based on tests of a prototype of the actual system or interpolation of test results for similar systems that bracket the system being designed. Where interpolation of test data is required, an adequate range of con fi gurations shall be tested, but not fewer than four tests for each parameter that is being varied, to permit interpolation to an accuracy of +/-5%. Rigid test weight(s) or articulating mannequins shall have a mass as speci fi ed in Section 6.3.2. For multiple-worker systems, a lumped mass in accordance with Section 6.3.7.2 may be used. The test(s) shall use the actual equipment speci fi ed for use in the active fall protection system. Full body harnesses may be omitted, provided that clearances are increased to account for stretch out of both the worker and the harness. PEAs may be substituted for SRLs in the tests, provided that testing has proved that the average deployment force of the chosen lanyard is within +/-5% of the average deployment force of the SRL. 8.3.6 Other Acceptable Methods. Other analytical methods, based on proven scienti fi c principles, shall be acceptable if they can be shown to accurately predict the performance of active fall protection systems. 9. REFERENCES This standard refers to the following publications, and where such reference is made, it shall be to the edition listed below, including all amendments published thereto. 9.1 American Concrete Institute (ACI) Ap pr ove e ri c a n N at i o n a l d Am Sta n da rd 34 AMERICAN S OCIETY OF S AFETY E NGINEERS ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems 9.1 .1 ACI 31 8-05, Building Code Requirements for Structural Concrete and Commentary 9.2 American Institute of Steel Construction (AISC) 9.2.1 ANSI/AISC 360-05, Specification for Structural Steel Buildings 9.3 American National Standards Institute (ANSI) 9.3.1 ANSI/SIA A92.29 Vehicle-Mounted Elevating and Rotating Aerial Devices 9.3.2 ANSI/IWCA I 1 4.1 -2001 , Window Cleaning Safety 9.4 American Society for Testing and Materials (ASTM) 9.4.1 A1 023/A1 023M-02, Standard Specification for Stranded Carbon Steel Wire Ropes for General Purposes 9.5 Other Publications 9.5.1 PLUS 11 56 Fall arrest systems — Practical Essentials, by Andrew C. Sulowski 9.5.2 ANSI/ASSE Z359 series of Standards 9.5.3 International Building Code 9.5.4 Arteau, J. (2003). “Protection contre les chutes de hauteur: absorbeur d’énergie, distance de freinage, grande hauteur de chute et grande masse (Protection against falls from height: energy absorber, deceleration distance, large free fall distance and large mass)”. Actes du 25e congrès de l’AQHSST, Trois-Rivières, 7–9 May, 2003, pp. 249–260 9.5.5 Sulowski, A. C. Evaluation of Fall Arresting Systems (Ontario Hydro Research Report 78-98H). Toronto, 1 978 1 0. FIGURES pr o ve eri ca n N ation al d Am Sta n da rd Ap AMERICAN S OCIETY OF S AFETY E NGINEERS 35 Specifications and Design Requirements for Active Fall Protection Systems SFD SDD ANSI/ASSE Z359.6-2009 American National Standard Legend: SDD = Swing-drop distance (drop in height of D-Ring from the onset of the swing to the point where the worker may impact any structure) SFD = Swing-fall distance (drop in height of D-Ring from the onset of the swing to the lowest point it reaches during the swing) Note: SDD and SFD are calculated assuming a circular (pendular) motion of the worker’s D-Ring on a fi xed taut length of lifeline. They do not include a drop in height due to free or deceleration distance Drawings © Copyright AMERICAN S OCIETY OF S AFETY E NGINEERS Ap pr ove e ri c a n N at i o n a l d Am Sta n da rd 36 Figure 1: Swing Falls ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems (HI) (HDA ) D-Ring (Typical) (FF) (HA ) MASD TFD (XL) DD (HI) (E) (HF) (XW) (XPEA ) (CA ) (CP) MASD Top of Highest Obstruction Legend: C A = Required clearance below the anchorage HI CP MASD = DD = FF - HDA + DD + HF + E = Required clearance below the platform = FF + DD + XW + E = Deceleration Distance HA = MASD + XL + XPEA = Safety margin = Free Fall = FFA + FFL + FFC (SEE FIGURE 1, 2 = Height of anchorage above the H DA = HF = E FF AND 3) working platform Height of D-Ring above the anchorage (H DA is negative if the D-Ring is initially below the anchorage) Final height of D-Ring (above the worker’s toes) at fall arrest = TDF = XL XPEA = = XW = Initial Height of D-Ring (above the worker’s surface) at start of fall Maximum anchorage system displacement (dynamic de fl ection of horizontal lifelines, fl exible anchorages) Total fall distance (of the worker’s dorsal D-Ring) Stretch of the lanyard Deployment of the personal energy absorber or clutching self-retracting lanyard Stretch out (due to D-Ring fl ip and slide, harness stretch, and straightening of worker’s body) Figure 2: Clearance (Excluding Swing Fall Distance) pr o ve eri ca n N ation al d Am Sta n da rd Ap AMERICAN S OCIETY OF S AFETY E NGINEERS Drawings © Copyright 37 ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems HI D-Ring (typical) XW HF HI D-Ring (typical) Legend: H F = Final height of D-Ring (above the worker’s toes) at fall arrest H I = Initial height of D-Ring of (above the workers surface) at start of fall XW = Stretch out (due to D-Ring flip and slide, Harness stretch, and straightening of the worker’s body) Legend: H F = Final height of D-Ring (above the worker’s toes) at fall arrest H I = Initial height of D-Ring of (above the worker’s surface) at start of fall XW = Stretch out (due to D-Ring fl ip and slide, harness stretch, and straightening of the worker’s body) Figure 3: Stretch Out Drawings © Copyright Ap pr ove e ri c a n N at i o n a l d Am Sta n da rd 38 AMERICAN S OCIETY OF S AFETY E NGINEERS ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems (H DA) D-Ring (Typical) D-Ring (Typical) (H DA) Anchorage Anchorage Connector Free Fall Distance (FF) Work Platform Length of Lanyard (LY) Anchorage Connector Length of Lanyard (LY) Free Fall Distance (FF) Anchorage Work Platform WORKER’S D-RING IS ABOVE ANCHORAGE WORKER’S D-RING IS BELOW ANCHORAGE LLegend: d FF = Free Fall FFA = Free Fall due to the activation distance of the fall arrester (to lock onto the vertical lifeline) FFL = Free Fall resulting from Lanyard slack = H DA + L Y H DA = Vertical distance from the D-Ring to where the lanyard connects to the anchorage connector (H DA is negative if the D-Ring is initially below the fall arrestor) L Y = Length of Lanyard Figure 4: Free Fall Resulting from Lanyard Lifeline Slack Drawings © Copyright pr o ve eri ca n N ation al d Am Sta n da rd Ap AMERICAN S OCIETY OF S AFETY E NGINEERS 39 ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems Anchorage (A) Anchorage (A) D-Ring Anchorage Connector Anchorage Connector (FFA ) Length of Lanyard (L Y) (HDA ) Working Surface Free Fall Distance (FF) (FFA ) Length of Lanyard (LY) Free Fall Distance (FF) (HDA ) D-Ring Working Surface WORKER’S D-RING IS BELOW ANCHORAGE WORKER’S D-RING IS ABOVE ANCHORAGE Lifeline Tensioner (LT) Lifeline Tensioner (LT) Legend: FF = Free Fall FFA = Free Fall due to the activation distance of the fall arrester (to lock onto the vertical lifeline) FFL = Free Fall resulting from lanyard slack = H DA + L Y H DA = Vertical distance from the D-Ring to where the lanyard connects to the anchorage connector LY (H DA is negative if the D-Ring is initially below the fall arrestor) = Length of lanyard Drawings © Copyright AMERICAN S OCIETY OF S AFETY E NGINEERS Ap pr ove e ri c a n N at i o n a l d Am Sta n da rd 40 Figure 5: Free Fall on Vertical Lifelines Resulting from Lanyard Slack and Movement of the Fall Arrest pr o ve eri ca n N ation al d Am Sta nd a Intermediate Anchorage End Anchorage End Anchorage (FFC) S Max (FC) MASD MAF Legend: F CLegend:= Force required to pull slack out of adjacent spans and hold the initial length of cable into approximate Fc = Force required to pull slack out of adjacentthis spansforce and hold length cable into approximate straight-line cords (because is the low,initial there is ofnegligible worker deceleration straight-line cords (becuase this force is low, there is negligible worker deceleration prior to achieving cusp FFsag) C = Free fall distance due to slack in the horizontal lifeline cable MAF = Maximum Force distance Arrest due to slack in the horizontal lifeline cable FF C = Free-fall MAL Maximum MAF == Maximum ArrestArrest Force Load (a force vector co-linear with the cable) prior to achieving cusp sag) MAL == Maximum S - SArrest Load ( a force vector co-linear with the cable) Max C S Max - S C S CSC ===Cusp Cusp of the horizontal to all out slack beingspans pulled adjacent spans and to the initial length of sag ofsag the horizontal lifeline (due tolifeline all slack(due being pulled of adjacent and toout theof initial rd length of cable being pulled into approximate straight-line cords) being pulled cords) to self-weight being balanced by the pretension force) S I =cable initial sag of into theapproximate horizontalstraight-line lifeline (due sag of the horizontal lifeline (due to self-weight balanced by the pre-tension S I ==initial S Max Maximum sag of the horizontal lifelinebeing at fall arrest (due to the force) applied MAF) 41 Drawings © Copyright Specifications and Design Requirements for Active Fall Protection Systems Figure 6: Horizontal Lifeline Sags and Forces (SC) (SI) MAL ANSI/ASSE Z359.6-2009 American National Standard Ap AMERICAN S OCIETY OF S AFETY E NGINEERS MAL ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems APPENDIX A (INFORMATIVE) COMMENTARY A.1 Selection of Personal Energy Absorbers (see Section 4.4.3.2). Section 4.4.3.2 limits the as- sumption of a 900 lbs (4.0 kN) peak impact force for ANSI/ASSE Z359.1 energy absorbers to situations where the free fall is 4.6 ft (1 .40 m) or less and worker mass is 31 0 lbs (1 41 kg) or less. The purpose of this limitation is to prevent the energy absorber from bottoming out. When either of the above restrictions cannot be met, the formula provided in Section 4.4.3.2 allows one to calculate the maximum allowable free fall needed to ensure that the personal energy absorber (PEA) does not bottom out. It is based on all of the energy from the fall being consumed by the PEA. The 4.6 ft (1 .40 m) limit is less than is currently allowed by some regulations and was determined as follows: EA.1 1) This Appendix is not a mandatory part of this standard. 2) This commentary provides additional information on selected sections in this standard. Fall protection engineering is a relatively new specialization, and for this reason the standard has adopted a fairly conservative approach to fall protection. 3) The authors of this standard expect that some sections will be refined as time and further research allow. Users of this standard who believe that it can be improved are invited to submit proposed changes, supported by research and sound reasoning, to the Z359.6 Subcommittee. A.1 .1 ANSI/ASSE Z359.1 establishes a test for PEAs that involves dropping a 220 lbs (1 00 kg) mass 6.0 ft. (1 .83 m). The PEA is permitted to deploy up to 3.5 ft (1 .07 m), with a peak force of up to 900 lbs (4.0 kN). A.1 .2 Most PEAs sold in U.S. are manufactured for both the U.S. and Canadian markets (and therefore limit their maximum deployment to 3.5 ft (1 .07 m) to meet the ANSI/ASSE Z359.1 (and CSA) requirement). A.1 .3 Most PEAs deploy at an average force of 600 to 800 lbs (2.67 to 3.56 kN). A.1 .4 Given the commentary in Section A.7, the ANSI Z359 Full Committee has concluded that a 282 lbs (1 28 kg) mass should be used to simulate the effect from a 31 0 lbs (1 41 kg) worker. This is a departure from the previously accepted assumption that a 220 lbs (1 00 kg) test mass would properly represent a 31 0 lbs (1 41 kg) worker. A.1 .5 The formula in Section 4.4.3.2 yields a maxi- mum allowable free fall of 4.6 ft (1 .40 m), based on FAvg = 720 lbs (3.2 kN), XMax = 3.5 ft (1 .07 m), and m = 31 0 lbs (1 41 kg). Ap pr ove e ri c a n N at i o n a l d Am Sta n da rd 42 AMERICAN S OCIETY OF S AFETY E NGINEERS ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems A.2 Self-Retracting Lanyards Used in Fall Arrest Systems (see Section 4.4.4.2). Section 4.4.4.2 restricts the use of self-retracting lanyards (SRLs) that meet the requirements of ANSI/ASSE Z359.1 . These SRLs are restricted to fall arrest systems where the SRL is anchored above the worker (such that the free fall is the lock-off distance of the SRL). The reasoning behind this requirement is as follows: A.2.1 The testing method in ANSI/ASSE Z359.1 subjects SRLs to a free fall of only 2.0 ft (0.61 m) plus the lock-off of the SRL. The maximum arrest force (MAF) is not measured (which would determine the MAF seen by the worker). Most of these devices include a label stating that the impact force to the worker’s body is kept below 900 lbs (4.0 kN), but only if the device is anchored above the worker prior to the drop, so that the free fall is limited to the lock-off distance of the SRL. A.3 Horizontal Lifeline Energy Absorbers Used in Fall Arrest Systems (see Section 4.4.8.2). Sec- tion 4.4.8.2 provides the following formula for limiting the maximum span of horizontal lifelines (HLLs) when horizontal lifeline energy absorbers (HLLEAs) are used: Lmax = 4.6 16 T Mw 9.75 avg 2 -4 where Lmax = maximum span, ft. TAvg = average deployment force of the HLLEA, lbs, in accordance with Section 6.3.6.3 M = the “lumping factor” for the maximum number of workers that may be attached to one span of the HLL at any one time, in accordance with Section E6.3.7.2 w = weight of one worker, lbs, in accordance with Section 6.3.2 Some members of the CSA Z259 Technical Com- pr o ve eri ca n N ation al d Am Sta n da rd Ap AMERICAN S OCIETY OF S AFETY E NGINEERS 43 ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems mittee have tested HLLEAs on long spans where, due to the properties of the energy absorber, the system has become unstable beyond certain span lengths and sagged well past a simple balance of forces between the PEA and HLLEA. The above formula was derived using the following progression of theoretical arguments: A.3.1 A body being accelerated by gravity will continue to accelerate downward until acted on by an upward force that is greater than the weight of the falling body. A.3.2 Because there is always elasticity in actual fall arrest anchorage systems, the force applied to arrest the falling body is related to the de fl ection of the system. A.3.3 In the case of HLLs, and particularly HLLs with HLLEAs, signi fi cant sag is required before the system reacts with a force greater than or equal to the weight of the falling body (the sag beyond which the falling body begins to slow). A.3.4 The worst case is a mid-span fall. A.3.5 The cable will defl ect into a V shape of two straight lines. A.3.6 The average cable tension is equal to the average deployment force of the HLLEA (usually less than the nominal [peak] deployment force). A.3.7 The average vertical arresting force applied to arrest the falling body is equal to the sum of the vertical components of the average cable tension. A.3.8 The sag at which the system begins to slow the falling mass is the sag where the average vertical arresting force applied by the cable equals the weight of the falling mass. HLLs meeting the requirements of this formula will begin to slow the falling worker(s) within the fi rst 4.0 ft (1 .22 m) of sag. The 4.0 ft (1 .22 m) value was selected to ensure that the PEA does not bottom out in a fall with a 6.0 ft (1 .83 m) lanyard connected to an HLL at waist height. With a few exceptions, HLLEAs on the market are already limited by their manufacturers to Ap pr ove e ri c a n N at i o n a l d Am Sta n da rd 44 AMERICAN S OCIETY OF S AFETY E NGINEERS ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems spans shorter than those permitted by this formula. Readers should note that the fi nal sag of the HLL at fall arrest is typically two to four times the sag where the system begins to slow the falling body. A.4 Determination of Factored Load Effects (see Section 5.2.3). Because fall arrest systems are subjected to dynamic rather than static forces, and because of the use of PEAs and HLLEAs to limit the forces in fall arrest systems, it was necessary to apply the load factors to the load effects rather than to the loads themselves. This is contrary to the limit states design methodology in the International Building Code 2003, where the load factor is applied to the weight of the falling mass. (If this approach were used in a system that includes a PEA, the maximum impact force could be identical to that calculated for the unfactored weight, resulting in no factor of safety for the strength of the system.) The overall factor of safety for the strength of the system is equal to the ratio of the load factor, α , divided by the capacity-reduction factor, Ø. The load factor applied to the load effect, α A, was chosen to be 1 .5 for consistency with load factors used in other American design codes. It was not developed based on a statistical review of the variability of loadings. The authors of this standard believe that the capacity-reduction factors used in ANSI/AISC360-05 and ACI-31 8 generally maintain an overall factor of safety greater than or equal to 2.0 between the applied loading and the ultimate strength of the supporting system, which agrees with the fall protection regulations in most jurisdictions where the factor of safety has been speci fi ed, e.g., the United States (OSHA). Section 5.2.3 speci fi es capacity-reduction factors for materials not covered by ANSI. These factors were selected with a view to maintaining a consistent factor of safety of at least 2.0, in accordance with the factors of safety that have been used for other materials. Applicable references are as follows: A.4.1 Section 3.2.2 of ANSI/SIA A92.2 for vehicle- mounted aerial devices speci fi es a structural factor of safety of at least 5.0 for fi berglass. This standard therefore uses a capacity-reduction factor of pr o ve eri ca n N ation al d Am Sta n da rd Ap AMERICAN S OCIETY OF S AFETY E NGINEERS 45 ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems 0.3, which, in combination with the load factor of 1 .5, matches the factor of safety of 5.0 in ANSI/SIA A92.2. A.4.2 Draft standand ANSI/ASSE Z359.17-20XX requires a factor of safety of 3.0 for synthetic rope. A capacity-reduction factor of 0.5 was therefore selected, in order to be consistent with ANSI/ASSE Z359.1 7-20XX. A.4.3 A capacity-reduction factor of 0.6 was select- ed for other ductile materials not covered by U.S. design codes to provide an overall factor of safety of 2.5. A.4.4 Although ACI-31 8 suggests a capacity-reduc- tion factor of 0.8 against the ultimate strength of prestressing strands, a value of 0.75 was selected for all wire rope cables to maintain a minimum factor of safety of 2.0. A.5 Swing Falls (see Section 5.3). The “swing velocity” of a worker is created by the potential energy gained by the worker’s drop in elevation during the swing. The swing velocity is therefore identical to the velocity attained in a vertical fall for the same drop in elevation. EA.5 U.S. legislative bodies (OSHA) require fall protection above threshold heights that are typically between 4.0 and 1 0.0 ft. The important difference with swing falls is that the impact will always be perpendicular to the main axis of the body, whereas in vertical falls the orientation of the body on impact may be random but can be affected by the twisting and tumbling of the falling worker as he or she attempts to land in the strongest possible orientation (feet fi rst). The Committee therefore believed that a conservative limit on the maximum permissible elevation drop during a swing fall was warranted, but also needed to allow a reasonable amount of lateral movement from an overhead anchorage. A maximum swing drop distance of 4.0 ft was chosen. A.6 Maximum Arrest Force (see Section 5.4.2.2). Sulowski (1 978) and other sources have recommended that the maximum impact to a worker wearing a properly fi tted full body harness should not exceed 9 g. The current maximum force accepted virtually everywhere in North America is 1 ,800 lbs Ap pr ove e ri c a n N at i o n a l d Am Sta n da rd 46 AMERICAN S OCIETY OF S AFETY E NGINEERS ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems (8 kN), which ensures that no more than 9 g is felt by the worker so long as his or her body mass is at least 200 lbs (91 kg). There is certainly a signi fi cant proportion of the working population that weighs less than this. For most SRLs, and all energy absorbers meeting ANSI/ASSE Z359.1 requirements, the maximum impact force that a worker should experience with a dry energy absorber at room temperature is 900 lbs (4.0 kN), thus keeping impacts below 9 g for body masses down to 1 00 lbs (45 kg). For large workers or long free falls where suffi cient clearance exists, two or more energy absorbers meeting the requirements of ANSI/ASSE Z359.1 could be used in series. This should be done only under the direction of a engineer. See Arteau (2003) and CSA PLUS 11 56. A.7 Design Mass of Workers (see Section 6.3.2). This standard radically departs from other testing and design standards in that the mass employed to represent a 31 0 lbs (1 41 kg) worker is 220 lbs (1 00 kg). ANSI/ASSE Z359.1 -2007 and standards in the CSA Z259 series published before 2003 provide for the dropping of 220 lbs rigid test masses to simulate the effect from a 31 0 lbs (1 41 kg) worker (the heaviest worker that these standards are designed to protect). The 220 lbs (1 00 kg) test mass is based on a commonly accepted principle that a human body will stretch and absorb energy, so that the impact forces from a person should be less than those from a rigid test mass of the same weight. The rule adopted by testing standards and some OSHA regulations speci fi es a relationship of 1 .4 between the impact forces generated by a test mass and those generated by a person of the same weight. This factor, established several decades ago, was based on dynamic testing using non-energy-absorbing lanyards. It has been assumed that the force relationship also translates into a mass relationship of 1 .4 (e.g., a 220 lbs (1 00 kg) weight will have the same effect on a fall arrest system as a 31 0 lbs (1 41 kg) worker). pr o ve eri ca n N ation al d Am Sta n da rd Ap AMERICAN S OCIETY OF S AFETY E NGINEERS 47 ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems One member of the CSA Technical Committee stated that he had done some very limited testing comparing the deployment of energy absorbers using rigid test torsos and human subjects and found virtually no difference between the two. A preliminary examination of the historical basis of the 1 .4 factor revealed a tremendous variation in the test data, and showed that 1 .4 was more a consensus value picked by regulators than a number clearly proved by testing. (Testing of rope lanyards at the time the 1 .4 factor was chosen showed a variation of 1 .1 to 1 .8.) The Technical Committee concluded that whereas one would expect a human body to absorb some fall energy because of its internal elasticity, energy absorber deployments might not re fl ect this, for two reasons: a) The drop tests that led to the 1 .4 factor probably produced greater impact forces on the human body (perhaps up to 1 ,800 lbs (8.0 kN) or more), in which case the in fl uence of the elasticity of the human body would be stronger. With the lesser forces of a energy absorber (nominally 900 lbs, and likely closer to 630 to 81 0 lbs), it is probable that the force takes up all of the initial slack in the human body, all of which lowers the body’s center of mass, generating some fall energy (which may be of the same magnitude as the energy the body absorbed as it fl exed). It is only at higher forces that tendons and joints bottom out, leading to increased compression or crushing of cartilage, stretching of tendons, and stretching of muscles beyond their range of easy movement. Thus where the forces are greater, the body may absorb or dissipate fall energy at a greater rate than is produced by the additional lowering of the center of gravity (leading to development of the 1 .4 factor). b) When a person wears a full body harness with a sliding D-Ring, the harness stretches and the D-Ring slides, lowering the body by perhaps 6 to 24 inches (0.1 5 to 0.61 m), depending on the elasticity of the harness. This fl ex of the harness and sliding of the D-Ring occurs at relatively low forces and therefore does not absorb as much energy as is gained by the additional lowering of the person’s center of mass. Ap pr ove e ri c a n N at i o n a l d Am Sta n da rd 48 AMERICAN S OCIETY OF S AFETY E NGINEERS ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems After further discussion, it was agreed that this standard should not rely on the 1 .4 factor for forces or for equivalency of test (or design calculation) masses, particularly since energy absorbers are now common place and the basis of the 1 .4 factor was testing with non-energy-absorbing lanyards. In the face of test data, and with plausible explanations why a person in a harness should cause the same deployment of a energy absorber as a rigid test mass, the consensus vote of the Full Committee was to reduce the 1 .4 factor to 1 .1 . A.8 Equivalent Lumped Mass (see Section 6.3.7.2). For multiple-worker falls, a common ap- proach is to lump the masses of workers together into a single mass that may then be analyzed using techniques for a single-worker fall. Research on multiple-worker falls has shown that it was virtually impossible to have a simultaneous peak impact involving multiple workers even when the goal of the test is to create a simultaneous impact. The information in Section 6.3.7.2.2 is consistent with the BS 8347-2005. A.9 Deployment of Personal Energy Absorbers and Self-Retracting Lanyards (see Section 7.2.3.4). If the designer of a fall arrest system has met the requirements of Section 4.4.3.2, the PEA will not fully deploy, and for this reason the designer may conservatively assume full deployment in calculating clearance requirements. If the designer is using energy analysis, dynamic analysis, or testing and interpolation analysis, the amount of deployment of the energy absorber can be accurately calculated. Static analysis, however, will not enable the designer to determine the amount of fall energy absorbed by other components of the fall arrest system (meaning that the designer cannot accurately calculate the deployment of the energy absorber). The equation in Section 7.2.3.4 is another version of the equation in Section 4.4.3.2.2.2, algebraically pr o ve eri ca n N ation al d Am Sta n da rd Ap AMERICAN S OCIETY OF S AFETY E NGINEERS 49 ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems manipulated to solve for PEA deployment rather than free fall height. A.10 Stretch Out (see Section 7.2.4). The stretch out of the worker and harness was kept as a separate factor so that designers account for: A.1 0.1 Situations where a worker using an SRL anchored overhead might fall from a kneeling or lying position. These situations require more clearance below the working platform than situations where the worker falls from a standing position; and A.1 0.2 The stretch of a full body harness, which can vary tremendously (typically from 6 to 30 inches) depending on the harness design and the elasticity of the webbing. A.11 Safety Margin for Flexible Anchorage Systems (see Section 7.2.6.2). The safety margins for fl exible anchorage systems are adjusted to account for the anticipated worst-case inaccuracies expected for the various analytical methods. The CMASD factors in this standard re fl ect the consensus of the Working Group and do not have a rational or scienti fi c basis. They were chosen as a starting point for this edition of the standard, because of their use by some Committee members. They may be subject to re fi nement in future editions if research into this topic is undertaken by interested parties and submitted to the Committee. A.1 2 Clearance for Equivalent Lumped-Mass Simulation of Multiple-Worker Falls (see Section 7.2.7). In a sequential fall on a fl exible anchorage system, the last worker falling will have the greatest free fall because the anchorage system (such as an HLL) will have been moved by the preceding falls. A.1 3 Condition Required for Static Analysis of Fall Arrest Systems (see Section 8.3.4.3.3). The equation in Section 8.3.4.3.3 was developed to ensure that an HLLEA will not deploy more than two-thirds of its maximum available deployment in a worst-case fall. This requirement permits users of static analysis to safely assume that the maximum tension in the HLL will be TMax (See Section 6.3.6.2). Ap pr ove e ri c a n N at i o n a l d Am Sta n da rd 50 AMERICAN S OCIETY OF S AFETY E NGINEERS ANSI/ASSE Z359.6-2009 American National Standard Specifications and Design Requirements for Active Fall Protection Systems Should the HLLEA bottom out, static analysis no longer applies. In that case, the designer would use energy, dynamic, or testing and interpolation analytical methods to accurately determine the peak forces in the HLL, which will be greater than the deployment force of the HLLEA. APPENDIX B (INFORMATIVE) BIBLIOGRAPHY B.1 Riches, D. (2002) “Analysis and evaluation of different types of test surrogate employed in the dynamic performance testing of fall arrest equipment”. Health & Safety Executive HSE (United Kingdom), Research Report CRR 411 /2002. E B.1 This Appendix is not a mandatory part of this standard. B.2 Corden, C.H.H. “Wire rope grip terminations”. Health and Safety Executive, May 1 996 B.3 Sulowski, A.C., and Amphoux, M. (eds). “Fundamentals of Fall Protection”. 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