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Adjustable suspension scaffolds are designed to be raised and lowered while occupied by workers and materials, and must be capable of bearing their load whether stationary or in motion. Note: Except where indicated, these requirements also apply to multi-level, single-point adjustable, multi-point adjustable, interior hung, needle beam, catenary, and float (ship) scaffolds.

Capacity
  • Scaffolds and scaffold components must be capable of supporting, without failure, their own weight and at least 4 times their maximum intended load (Figure 1). [1926.451(a)]

  • Each suspension rope, including connecting hardware, must be capable of supporting, without failure, at least 6 times the maximum intended load applied to that rope while the scaffold is operating at the greater of either:

    • The rated load of the hoist, or

    • 2 times the stall load of the hoist. [1926.451(a)(4)]
  • All suspension scaffold support devices, such as outrigger beams, cornice hooks, and parapet clamps, must:

    • Rest on surfaces capable of supporting at least 4 times the load imposed on them by the scaffold operating at the greater of either:

      • The rated load of the hoist, or

      • 1½ times the stall capacity of the hoist (Figures 2 & 3). [1926.451(d)(1)]
    • Be supported by bearing blocks (Figures 2 & 3). [1926.451(d)(5)(ii)]

    • Be secured against movement by tiebacks installed at right angles to the face of the building or structure (Figures 2 & 3), or by opposing angle tiebacks installed and secured to a structurally sound point of anchorage (structurally sound points of anchorage include structural members, but not vents, electrical conduit, or standpipes and other piping systems). [1926.451(d)(5)(iii)]
  • No more than two employees should occupy suspension scaffolds designed for a working load of 500 pounds (non-mandatory). [1926 Subpart L Appendix A (2)(p)(2)]

  • No more than three employees should occupy suspension scaffolds designed for a working load of 750 pounds (non-mandatory). [1926 Subpart L Appendix A (2)(p)(2)]

  • Scaffolds shall be altered only under the supervision and direction of a competent person. [1926.451(f)(7)]
Figure 1. This job-made rig consists of some sections of scaffold decking and some aluminum ladders, hung from the roof. Who determined if it was capable of supporting its own weight and 4X its maximum intended load?

Figure 1.
This job-made rig consists of some sections of scaffold decking and some aluminum ladders hung from the roof. Who determined if it was capable of supporting its own weight and 4X its maximum intended load?


Figure 2. Does this parapet look capable of supporting at least 4X the load imposed on it by the cornice hook? Should the cornice hook be tied back, and supported with bearing blocks?

Figure 2.
Does this parapet look capable of supporting at least 4X the load imposed on it by the cornice hook? Should the cornice hook be tied back, and supported with bearing blocks?


Figure 3. How likely is this hook to slip? Has it been supported by bearing blocks? Does a length of manila rope tied with an overhand knot constitute adequate tieback?

Figure 3.
How likely is this hook to slip? Has it been supported by bearing blocks? Does a length of manila rope tied with an overhand knot constitute adequate tieback?




Components
  • Scaffold components manufactured by different manufacturers must not be intermixed, unless they fit together without being forced, and the scaffold's structural integrity is maintained (Figure 4). [1926.451(b)(10)]

  • Scaffold components manufactured by different manufacturers are not allowed to be modified to make them fit together, unless a competent person determines that the resulting scaffold is structurally sound. [1926.451(b)(10)]

  • Scaffold components made of dissimilar metals must not be used together unless a competent person has determined that galvanic action (rust) will not reduce the strength of any component below OSHA standards. [1926.451(b)(11)]

  • Scaffold support devices such as cornice hooks, roof hooks, roof irons, parapet clamps, or similar devices must be made of steel, wrought iron, or materials of equivalent strength. [1926.451(d)(5)(i)]
Figure 4. This is the same jury-rigged scaffold as in Figure 1. How can you tell if these components possess sufficient structural integrity?

Figure 4.
This is the same jury-rigged scaffold as in Figure 1. How can you tell if these components possess sufficient structural integrity?




Outrigger Beams
  • Outrigger beams must be made of structural metal, or other material of equivalent strength. [1926.451(d)(2)]

  • Outrigger beams must be restrained to prevent movement. [1926.451(d)(2)]

  • The inboard ends of outrigger beams must be stabilized by bolts or other direct connections to the floor or roof deck, or by counterweights. [1926.451(d)(3)]

  • Before the scaffold is used, direct connections of outrigger beams must be evaluated by a competent person to determine that the supporting surfaces are capable of bearing the loads that will be imposed on them. [1926.451(d)(3)(i)]

  • When outrigger beams are not stabilized by bolts or other direct connections to the floor or roof deck, they must instead be secured by tiebacks. [1926.451(d)(3)(vi)]

  • Outrigger beams must be placed perpendicular to their bearing support (usually the face of the building or structure, (Figure 5). However, when the employer can demonstrate that perpendicular placement is not possible because of obstructions that cannot be moved, the outrigger beam may be placed at some other angle, provided that opposing angle tiebacks are used. [1926.451(d)(3)(viii)]

  • Outrigger beams shall be:

    • Provided with stop bolts or shackles at both ends; [1926.451(d)(4)(i)]

    • Securely fastened together with the flanges turned out when channel iron beams are used instead of I-beams; [1926.451(d)(4)(ii)]

    • Installed with all bearing supports perpendicular to the beam center line; [1926.451(d)(4)(iii)]

    • Set and maintained with the web in a vertical position; [1926.451(d)(4)(iv)]

    • Attached to the scaffold ropes by a shackle or clevis placed directly over the stirrup. [1926.451)(d)(4)(v)]


Suspension Ropes
  • Suspension ropes supporting adjustable suspension scaffolds must have a diameter large enough to permit proper functioning of brake and hoist mechanisms. [1926.451(f)(10)]

  • The use of repaired wire rope as suspension rope is prohibited. [1926.451(d)(7)]

  • Wire suspension ropes must not be joined together except through the use of eye splice thimbles connected with shackles or coverplates and bolts. [1926.451(d)(8)]

  • The load end of wire suspension ropes must be equipped with proper-size thimbles, and secured by eyesplicing or equivalent means (Figure 6). [1926.451(d)(9)]

  • Ropes must be inspected for defects by a competent person prior to each workshift, and after every occurrence which could affect a rope's integrity (see Tip). [1926.451(d)(10)]

  • Ropes are to be replaced when any of the following conditions exist:

    • Any physical damage which impairs the function and strength of the rope (Figure 7). [1926.451(d)(10)(i)]

    • Kinks that might impair the tracking or wrapping of the rope around the drum or sheave of the hoist (Figure 8). [1926.451(d)(10)(ii)]

    • Six randomly distributed wires are broken in one rope lay, or three broken wires in one strand in one rope lay (Figure 9). [1926.451(d)(10)(iii)]

    • Loss of more than one-third of the original diameter of the outside wires due to abrasion, corrosion, scrubbing, flattening, or peening. [1926.451(d)(10)(iv)]

    • Heat damage caused by a torch, or any damage caused by contact with electrical wires. [1926.451(d)(10)(v)]

    • Evidence that the secondary brake has been activated during an overspeed condition and has engaged the suspension rope. [1926.451(d)(10)(vi)]
  • Swaged attachments or spliced eyes on wire suspension ropes may not be used unless they are made by the manufacturer or a qualified person. [1926.451(d)(11)]

  • When wire rope clips are used on suspension scaffolds:

    • There must be a minimum of 3 clips installed, with the clips a minimum of 6 rope diameters apart (Figure 10); [1926.451(d)(12)(i)]

    • Clips must be installed according to the manufacturer's recommendations; [1926.451(d)(12)(ii)]

    • Clips must be retightened to the manufacturer's recommendations after the initial loading; [1926.451(d)(12)(iii)]

    • Clips are to be inspected and retightened to the manufacturer's recommendations at the start of each subsequent workshift; [1926.451(d)(12)(iv)]

    • U-bolt clips may not be used at the point of suspension for any scaffold hoist; [1926.451(d)(12)(v)]

    • When U-bolt clips are used, the U-bolt must be placed over the dead end of the rope, and the saddle must be placed over the live end of the rope. [1926.451(d)(12)(vi)]
  • Suspension ropes are to be shielded from heat-producing processes. When acids or other corrosive substances are used on a scaffold, the ropes shall be shielded, treated to protect against the corrosive substances, or shall be of a material that will not be damaged by the substances. [1926.451(f)(11)]

Tip: Analysis of Bureau of Labor Statistics data for suspended scaffold fatalities from 1992-99 found that over 20 percent of fall deaths were due to suspension ropes breaking. This underlines the importance of inspecting ropes before every workshift.

Figure 5. This wire rope has a thimble secured by an eyesplice, as required on the load end of suspension ropes.

Figure 5.
This wire rope has a thimble secured by an eyesplice, as required on the load end of suspension ropes.


Figure 6. The construction adhesive on this wire rope could interfere with the operation of the hoist brakes.

Figure 6.
The construction adhesive on this wire rope could interfere with the operation of the hoist brakes.


Figure 7. This wire rope has "bird-caged" and become unsuitable for use.

Figure 7.
This wire rope has "bird-caged" and become unsuitable for use.


Figure 8. The constant rotation of this rope as it ran through the hoist has caused the free end to twist and split.

Figure 8.
The constant rotation of this rope as it ran through the hoist has caused the free end to twist and split.


Figure 9. There are only 2 clips fastening this wire rope. Is it safe? (The standard requires 3 clips).

Figure 9.
There are only 2 clips fastening this wire rope. Is it safe? (The standard requires 3 clips).




Hoists
  • The stall load of any scaffold hoist must not exceed 3 times its rated load (Figure 10). [1926.451(a)(5)]

  • When winding drum hoists are used and the scaffold is extended to its lowest point of travel, there must be enough rope to still wrap four times around the drum. [1926.451(d)(6)]

  • When other types of hoists are used, the suspension ropes must be long enough to allow the scaffold to travel to the level below without the rope end passing through the hoist, or else the rope end must be provided with means to prevent the end from passing through the hoist. [1926.451(d)(6)]

  • Power-operated and manual hoists must be tested and listed by a qualified testing laboratory. [1926.451(d)(13)]

  • Gasoline-powered hoists may not be used on suspension scaffolds. [1926.451(d)(14)]

  • Gears and brakes of power-operated hoists used on suspension scaffolds must be enclosed. [1926.451(d)(15)]

  • In addition to the normal operating brake, both power-operated and manual hoists must have a braking device or locking pawl which engages automatically when a hoist experiences:

    • An instantaneous change in momentum; or

    • An accelerated overspeed episode. [1926.451(d)(16)]
  • Manually operated hoists must require a positive crank force to descend. [1926.451(d)(17)]

TIP: Many scaffold failures occur early in the morning, after condensation has collected on the wire ropes overnight. The preferred industry practice at the beginning of a shift is to raise the scaffold 3 feet, hit the brakes, then lower the scaffold and hit the brakes again. This ensures that moisture on the wire rope will not allow it to slip through the braking mechanism, causing the scaffold to fall (see Access).

Figure 10. Animation of what happens when a scaffold becomes stuck while traveling.

Figure 10.
If a suspended scaffold becomes stuck while traveling, the hoist motor may strain and cause additional load on tiebacks, counterweights, or even the structure itself. Should these fail, the result may be a fatal fall.



View animation of this image.


 
 
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