03/04/2004 - Wire rope clips on suspension scaffolds; safety latches on large crane hooks; order of assembly for hanging scaffolds; and horizontal lifeline design.

Standard Interpretations - Table of Contents

• Standard Number:

1926.502(d)(8); 1926.502(b); 1926.251(c); 1926.760(d); 1926.502(d)(14); 1926.451(a); 1926.451(b); 1926.451(f); 1926.251(a)(4); 1926.451(d)(12); 1926.550(g)(4)(iv)(B); 1926.753(d); 1926.550(g); 1926.502(d)(15)

OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at http://www.osha.gov.

March 4, 2004

Martin D. Spencer Jr.
Northeast Area Rigging Coordinator
International Brotherhood of Boilermakers
5745 Big Tree Road
Orchard Park, NY 14127

Re: Wire rope clips on suspension scaffolds; safety latches on large crane hooks; hanging scaffolds - order of assembly; jobsite fabricated lifting accessories - criteria; and horizontal lifelines: use of wire rope clips, anchorages, number of persons allowed to be connected, requirements relating to sag, and use of synthetic rope.

Dear Mr. Spencer:

This is in response to your facsimile dated November 14, 2003, to the Occupational Safety and Health Administration (OSHA). We have paraphrased your questions as follows:

Question 1(a) - (c): When using horizontal lifelines as part of personal fall arrest systems, what type of wire rope clips does OSHA require, and how many clips must be used? Additionally, what are the horizontal spacing criteria for the uprights?

Answer
Subpart M - Fall Protection, 29 CFR 1926.502, contains criteria requirements for fall protection systems. Horizontal lifelines may be used as part of a personal fall arrest system if provisions within §1926.502(d) are met. Section 1926.502(d)(8) requires that:

Horizontal lifelines shall be designed, installed, and used, under the supervision of a qualified person, as part of a complete personal fall arrest system, which maintains a safety factor of at least two.

Subpart M does not specify what type of wire rope clip or how many clips/clamps must be used when installing a horizontal lifeline. However, under §1926.502(d)(8), these decisions must be made under the supervision of a qualified person when the system is designed. The determination of the horizontal spacing criteria for uprights is also left to the qualified person's supervisory approval.¹

In an August 28, 2000 letter to Mr. Troxell ², we addressed the related issue of using wire rope clips on a wire rope guardrail. In that letter, we cautioned that, as a practical matter, it is unlikely that the criteria requirements for guardrails under §1926.502(b) could be met unless the manufacturer's recommendations for the number of clips to be used on wire ropes of different diameters were followed (for example, the Crosby Group, Inc., general catalog 2000 edition, has tables showing their recommendations for their clips). We also pointed out that OSHA's standard for rigging equipment used for material handling, 29 CFR 1926.251, has a table showing the number of clips required for wire rope ½-inch and greater. We noted that although that standard does not apply to wire rope used for guardrails, when designing a rope system to meet the §1926.502 guardrail requirements, following the tables at §1926.251 will normally ensure that there will be enough clips.

The forces exerted on a horizontal lifeline are substantially greater than those on a typical guardrail. Therefore, the system designer needs to ensure that the number, type, and location of clips will withstand the anticipated forces and meet the performance requirements in §1926.502 for horizontal lifelines.

Question 1(d): How many people may be attached to the same horizontal lifeline at the same time?

Answer
The standard does not set a limit on the number of people that may be simultaneously attached to the same horizontal lifeline. Under §1926.502(d)(8), the determination of how many people may be simultaneously attached depends on a variety of factors that a qualified person must consider when designing the system.³

Note that Appendix C to Subpart M may also be helpful to the qualified person dealing with this situation. Section II (h)(6) states that:

Extreme care should be taken in considering a horizontal lifeline for multiple tie-offs. The reason for this is that in multiple tie-offs to a horizontal lifeline, if one employee falls, the movement of the falling employee and the horizontal lifeline during arrest of the fall may cause other employees to fall also. Horizontal lifeline and anchorage strength should be increased for each additional employee to be tied-off. For these and other reasons, the design of systems using horizontal lifelines must only be done by qualified persons.

Although the possibility of one person falling may raise the risk of another person being pulled into a fall, it is not our position that the lifeline must necessarily be designed so that it can withstand a simultaneous fall by all the individuals tied-off to it. In assessing the total strength required for the lifeline, the qualified person must make a determination on the likelihood of simultaneous falls based on factors such as the type of walking/working surface the workers will be on, the length of their lanyards, and whether their work assignments call for them all to be near the edge at the same time.

Question 1(e): Are there any recommended anchor points for horizontal lifelines?

Answer
Anchor points for a horizontal lifeline must be determined under the supervision of a qualified person under §1926.502(d)(8). Subpart M does not identify particular anchor points for horizontal lifelines. Appendix C, Section II (h)(1), provides some anchorage point considerations to be addressed when designing personal fall arrest systems.

Question 2: For a horizontal lifeline used as part of a personal fall arrest system during steel erection work, how tight should the lifeline be, and may synthetic rope be used for the horizontal lifeline?

Answer
Subpart R - Steel Erection, 29 CFR 1926.760, addresses fall protection requirements in steel erection. Section 1926.760(d), criteria for fall protection equipment, incorporates into Subpart M §1926.502(b)-(e), fall protection systems criteria and practices. Section 1926.502(d)(8) requires that:

Horizontal lifelines shall be designed, installed, and used, under the supervision of a qualified person, as part of a complete personal fall arrest system, which maintains a safety factor of at least two.

Therefore, a qualified person is required to determine how tight the lifeline should be based on site-specific factors. No other requirements are imposed by OSHA regarding the tightness of the lifeline, so long as it comports with a safety factor of at least two.

With regard to the use of synthetic ropes, §1926.502(d)(14) specifies that, when using non-wire rope, synthetic rope (rather than nature fiber rope) must be used:

Ropes and straps (webbing) used in lanyards, lifelines, and strength components of body belts and body harnesses shall be made from synthetic fibers.

Therefore, the standard permits the use of synthetic rope (instead of wire rope) for a horizontal lifeline.

Question 3: Are you allowed to hang pre-engineered scaffolding from the top down, or do you have to erect it from the ground up?

Answer
Section 1926.451 sets forth the general requirements for scaffolds. In regard to the capacity of the scaffold, §1926.451(a)(6) states:

Scaffolds shall be designed by a qualified person and shall be constructed and loaded in accordance with that design. Non-mandatory Appendix A to this subpart contains examples of criteria that will enable an employer to comply with paragraph (a). [Emphasis added.]

Section 1926.450(b) defines "qualified" as:

Qualified means one who, by possession of a recognized degree, certificate, or professional standing, or by extensive knowledge, training, and experience, has successfully demonstrated his/her ability to solve or resolve problems related to the subject matter, the work, or the project.

The employer is responsible for designing and assembling components in such a way that the completed system will meet the requirements of §1926.451(a). Scaffold components which are not selected and loaded in accordance with this Appendix, and components for which no specific guidelines or tables are given in this Appendix, must be designed and constructed in accordance with the capacity requirements of §1926.451(a).

The requirements set forth in §1926.451(b) must also be followed when erecting the scaffold. In regard to scaffold components used in the construction of the scaffold, §1926.451(b)(10) states:

Scaffold components manufactured by different manufacturers shall not be intermixed unless the components fit together without force and the scaffold's structural integrity is maintained by the user. Scaffold components manufactured by different manufacturers shall not be modified in order to intermix them unless a competent person determines the resulting scaffold is structurally sound. [Emphasis added.]

Section 1926.451(f) sets out requirements involving the use of the scaffold. Where scaffolding is erected, moved, dismantled, or altered, §1926.451(f)(7) provides:

Scaffolds shall be erected, moved, dismantled, or altered only under the supervision and direction of a competent person qualified in scaffold erection, moving, dismantling, or alteration. Such activities shall be performed only by experienced and trained employees selected for such work by the competent person. [Emphasis added.]

A "competent person" is defined in §1926.450(b):

Competent person means one who is capable of identifying existing and predictable hazards in the surroundings or working conditions which are unsanitary, hazardous, or dangerous to employees, and who has authorization to take prompt corrective measures to eliminate them.

When erecting the scaffold you describe, the employer must ensure that the scaffold has been designed by a qualified person and constructed and loaded in accordance with that design. If the designer requires the scaffold to be erected from the top down, then it must be erected in that manner. If the designer requires it to be erected from the bottom up, then that order must be followed. If the designer does not indicate one or the other order, then the competent person must determine whether the scaffold may be erected from the top down or the bottom up.

Question 4: Are there OSHA standards that specify criteria for constructing jobsite fabricated rigging equipment such as an equalizing beam, lifting beam, spreader beam, equalizing plates, tee lugs, lifting lugs, and welded scaffold brackets?

Answer
The only OSHA construction standards that contains specific criteria related to the construction of special custom design lifting accessories is 29 CFR 1926.251(a)(4), which states:

(4) Special custom design grabs, hooks, clamps, or other lifting accessories, for such units as modular panels, prefabricated structures and similar materials, shall be marked to indicate the safe working loads and shall be proof-tested prior to use to 125 percent of their rated load.

The custom design lifting accessories you describe above must be tested and marked in accordance with §1926.251(a)(4) before being used.

Question 5: Under §1926.451(d)(12)(v) and (vi), when wire rope clips are used on suspension scaffolds, "(v) U-bolt clips shall not be used at the point of suspension for any scaffold hoist," and "(vi) when U-bolt clips are used, the U-bolt shall be placed over the dead end of the rope, and the saddle shall be placed over the live end of the rope." Does §1926.451(d)(12)(v) contradict paragraph (d)(12)(vi)?

Answer
No. By its terms, §1926.451(d)(12)(v) prohibits the use of U-bolt clips at the point of suspension for any scaffold. The scaffold standard does not prohibit using U-bolt clips elsewhere. However, when using them elsewhere, under §1926.451(d)(12)(vi), the U-bolt must be placed over the dead end of the rope, and the saddle placed over the live end of the rope.

Question 6: Under §1926.251(c)(4)(iii), are eyes in wire rope bridles and slings or bull wires formed by wire rope clips permitted when used to lift scrap boxes or pendants?

Answer
No. Section 1926.251(c)(4)(iii) states:

eyes in wire rope bridles and slings or bull wires shall not be formed by wire rope clips or knots.

This provision specifically prohibits eyes in wire rope bridles and slings or bull wires being formed by wire rope clips. There is no exception for lifting scrap boxes or pendants.

Question 7: Does OSHA have any specific criteria in its standards for horizontal high-lines?

Answer
There are no OSHA standards setting criteria for horizontal high-lines. However, an employer's use of a horizontal high-line must be in accordance with its obligations under Section 5(a)(1) of the Occupational Safety and Health Act (the "General Duty Clause"), which states:

Each employer shall furnish to each of his employees employment and a place of employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees.

In our view, the industry recognizes that the following engineering factors, among others, must be considered when designing horizontal high-lines: the span and sag of the wire rope line, the weight of the load being lifted, the initial tension of the rope line, and the size of the columns.

Question 8: Is it mandatory for large crane hooks to have safety latches on them? If so, are older hooks without them "grandfathered"?

Answer
OSHA requirements for a safety latch on hooks do not depend of the size of the hook but rather the activity for which the hook is being used. Safety latches on hooks are required in two instances:

Personnel platforms

Section 1926.550(g)(4)(iv)(B) states:

Hooks on overhaul ball assemblies, lower load blocks, or other attachment assemblies shall be of a type that can be closed and locked, eliminating the hook throat opening. Alternatively, an alloy anchor type shackle with a bolt, nut and retaining pin may be used.

This provision is intended to prevent personnel platforms from falling as a result of becoming accidentally unfastened from the hook.

Working under the load

Section 1926.753(d) prohibits workers engaged in steel erection activities from being directly under a suspended load, with some exceptions. Where those exceptions apply (i.e., where workers are engaged in the initial connection of steel or employees are unhooking the load), specific criteria apply. One such criterion is the requirement for safety latches.

Section 1926.753(d)(2)(ii) states:

Hooks with self-closing safety latches or their equivalent shall be used to prevent components from slipping out of the hook . . .

This provision was intended to prevent the components from becoming accidentally unfastened from the hook and falling on the worker below. The preamble to the proposed rule explained that an "equivalent" device would include:

A hook with another type of closing device, i.e., a hook with a spring-loaded gate or another type of safety hook that would provide the same level of safety as a safety hook with a self-closing latch. (At 63 FR 43464, August 13, 1998.)

Neither the personnel platform nor the steel erection/working under load requirement has an exception for large hooks - the requirements apply irrespective of the size of the hook. Also, there is no "grandfather" exception for older hooks without safety latches.

Question 9: For wire rope used in material handling, is it permissible to use a knot and clip (contractors knot) end termination?

Answer
Section 1926.251(c)(3) states:

Wire rope shall not be secured by knots, except on haul back lines on scrapers.

Knotting wire rope compromises the integrity of the strength of the wire rope and is therefore prohibited. Based on the picture provided, which showed a knot in wire rope secured by a U-bolt clip, this practice would be in violation of §1926.251(c)(3).

Question 10: Do OSHA standards require the attachment of an orange and white flag to the highest point of a crane that is being used in the vicinity of an airport?

Answer
There are no OSHA standards that require the highest point of a crane to be marked to enhance visibility to air traffic. However, the use of a crane in the vicinity of an airport may be subject to requirements set by other regulatory agencies, such as the Federal Aviation Administration.

Question 11: Do OSHA standards specify a particular anchorage point for connecting the lanyards of workers on crane suspended personnel platforms? Do the standards limit the number of such workers that can be attached to an anchorage point?

Answer
Section 1926.550(g)(1)(i) (Crane or derrick suspended personnel platforms) of Subpart N (Cranes, Derricks, Hoist, Elevators, and Conveyors) states:

This standard applies to the design [and]* * * use of personnel platforms on the load lines of cranes or derricks and the hoisting of personnel platforms on the load lines of cranes or derricks.

Section 1926.550(g)(6)(vii) provides:

Except over water, employees occupying the personnel platform shall use a body belt/harness system with lanyard appropriately attached to the lower load block or overhaul ball, or to a structural member within the personnel platform capable of supporting a fall impact for employees using the anchorage. When working over water, the requirements of §1926.106 shall apply. [Emphasis added.]

In addition, §1926.550(4)(i) (Design Criteria)(C) notes in part:

* * *
Criteria for guardrail and personal fall arrest system anchorages are contained in Subpart M [Fall Protection] of the Part. [Emphasis added.]

Section 1926.502(d)(15) of Subpart M states:

Anchorages used for attachment of personal fall arrest equipment shall be independent of any anchorage being used to support or suspend platforms and capable of supporting at least 5,000 pounds * * * per employee attached or shall be designed, installed, and used as follows: (i) as part of a complete personal fall arrest system which maintains a safety factor of at least two; and (ii) under the supervision of a qualified person.

As you can see from the text of these provisions, §1926.550(g)(6)(vii) specifies the permissible locations of anchorage points - lower load block, overhaul ball, or the structural member within the personnel platform. Section 1926.502(d)(15) in Subpart M sets forth various criteria for anchorage points but does not establish a limit relative to the number of workers that can be attached to any one anchorage.

In addition, note that several other significant provisions in §1926.550(g) of Subpart N may affect the number of employees allowed in a personnel platform. These provisions include §1926.550(g)(4), which limits the number of employees on platforms to those required to do the work, and sets other requirements as well. Provisions most relevant to your question include §1926.550(g)(3)(i)(E) (limits total weight of loaded personnel platform and related rigging to 50 percent of rated capacity for the radius and configuration of the crane); §1926.550(g)(3)(i)(B) (load line capacities); §1926.550(g)(4)(i)(C) (support criteria applicable to the personnel platform itself); §1926.550(g)(4)(iii) (load limitation of the personnel platform); and §1926.550(g)(4)(iii)(C) (personnel platform rigging requirements). Note that this list is not comprehensive -- please see the actual text of §1926.550(g) for the other provisions.

If you need additional information, please contact us by fax (202-693-1689) at: U.S. Department of Labor, OSHA, Office of Construction Standards and Guidance. You can also contact us by mail at U.S. Department of Labor, OSHA, Office of Construction Standards and Guidance, Room N3468, 200 Constitution Avenue, N.W., Washington, D.C. 20210, although there will be a delay in our receiving correspondence by mail.

Sincerely,

Russell B. Swanson, Director
Directorate of Construction

¹Note that Appendix C to Subpart M provides Non-Mandatory Guidelines for complying with §1926.502(d), personal fall arrest systems, and provides some information on the design of horizontal lifelines. [ back to text ]

²This letter is available at http://www.osha.gov under the Laws & Regulations -- Interpretations section. [ back to text ]

³Note that, with respect to the anchorages to which the horizontal lifeline will be attached, §1926.502(d)(15) states:

Anchorages used for attachment of personal fall arrest equipment shall be . . . capable of supporting at least 5,000 pounds per employee attached or shall be designed, installed, and used as follows: (i) as part of a complete personal fall arrest system which maintains a safety factor of at least two;
* * *

[ back to text ]

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