| SECTION
7: Suspension Scaffolds
Suspension scaffolds, also know as swing-stage scaffolds,
are suspended by ropes or cables
connected to stirrups at each end of the platform.
Currently the only supported scaffold the University uses is a boatswain
chairs. However, two point suspension scaffolds are used on campus
by contractors and the potential exists for University use. A detailed
analysis with specific regulations and tips pertaining to the boatswain
chairs and swing stage scaffolds is located in the individual scaffold
section, Appendix
A.
Anchorage (top)
The safe use of a suspended scaffold begins with secure anchorage.
The weight of the scaffold and its occupants must be supported
by both the structure to which it is attached and by each of the scaffold
components that make up the anchorage system.
Suspended scaffolds outrigger beams must be stabilized to the floor
or deck by bolts, counterweights, or other direct connections.
Direct connections must be capable of resisting the greater of:
- At least 4 times the tipping moment imposed by the scaffold
when it is operating at the rated load of the hoist.
- A minimum of
1-½ times the tipping moment imposed by the scaffold
when it is operating at the stall load of the hoist.
Tiebacks
Tiebacks must be secured to a structurally sound anchorage on the
building or structure, which may include structural members, but
not include
vents, electrical conduits, or standpipes and other piping systems.
Tiebacks must be installed perpendicular to the face of the building
or structure, or opposing angle tiebacks must be installed. Single
tiebacks installed at an angle are prohibited.
Tiebacks must be equivalent in strength to the suspension ropes and
hoisting rope.
Counterweights
Counterweights used to balance adjustable suspension scaffolds must
be capable of resisting the greater of:
- At least 4 times the tipping moment imposed by the scaffold
when it is operating at the rated load of the hoist.
- A minimum of
1-½ times the tipping moment imposed by the scaffold
when it is operating at the stall load of the hoist.
Only items specifically designed as counter weights may be used as
counterweights. Flowable materials such as sand, gravel, and similar
materials that can be easily dislocated are prohibited. Masonry units,
rolls of roofing felt, and other similar construction materials may
not be used as counterweights.
Counterweights must be secured by mechanical means to the outrigger
beams to prevent accidental displacement.
Counterweights must remain attached to the outrigger beam until the
scaffold is disassembled.
Support (top)
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.
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.
Capacity
Scaffold and scaffold components must be capable of supporting their
own load and at least 4 times their maximum intended load.
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 load of the hoist or 2 times the stall load.
Suspension scaffolds 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.
Suspension scaffolds must rest on bearing blocks.
Suspension scaffolds must be secured against movement by tiebacks
installed at right angles to the face of the building or structure,
or by opposing angle tiebacks installed and secured to a structurally
sound point of anchorage. Sound anchorage includes but is not limited
to structural members, but does not include vents, electrical conduits,
or standpipes and other piping.
No more than two people should occupy suspension scaffolds designed
for a working load of 500 pounds.
No more than three people should occupy suspension scaffolds designed
for a working load of 750 pounds.
Scaffolds can only be altered under the supervision of the competent
person.
Outrigger beams
Outrigger beams must be made of structural metal, or other material
of equivalent strength, and must be restrained to prevent movement.
The inboard ends of outrigger beams must be stabilized by bolts or
other direct connections to the floor or the roof deck, or restrained
by counterweights.
A competent person must evaluate direct connection of outrigger beams
and confirm that the supporting surfaces are capable of bearing the
load imposed on them.
When beams must be secured by tiebacks if they are not secured the
floor or roof deck by bolts or other direct connections, outrigger
beams must be placed perpendicular to their bearing support, normally
the face of the building, except when the competent person can demonstrate
that perpendicular placement is not possible because of obstructions.
In those cases outrigger beams may be placed at some angle, given that
opposing angle tiebacks are used.
Outrigger beams must be provided with stop bolts or shackles at both
ends, and securely fastened together with the flanges turned out when
channel iron beams are used instead of I-beams. Outrigger beams must
be set and maintained with the web in a vertical position and attached
to the scaffold ropes by a shackle or clevis placed directly over the
stirrup.
All bearing supports must me installed perpendicular to the beam’s
center line.
Suspension Rope
Suspension ropes supporting adjustable suspension scaffolds must have
a diameter large enough to permit proper functioning of brake and
hoist mechanisms.
The use of repaired wire rope as suspension rope is prohibited.
Wire suspension ropes must not be joined together except through the
use of eye splice thimbles connected with shackles or coverplates and
bolts.
The load end of wire suspension ropes must be equipped with proper-size
thimbles, and secured by eye splicing or equivalent means.
The competent person must inspect ropes for defects prior to each
work shift, and after every occurrence that could affect the rope's
integrity.
Ropes are to be replaced when any of the following conditions exist:
- Any physical damage which impairs the
function and strength of the rope
- Kinks that might impair the tracking
or wrapping of the rope around the drum or sheave of the hoist
- If
one rope has six randomly distributed broken
wires, or has three broken wires in one strand
- Loss of more than one-third
of the ropes original diameter due to abrasion, corrosion, scrubbing,
flattening, or peening
- Heat damage caused by a torch, or
any damage caused by contact with electrical wires
- Evidence that the secondary
brake has been activated during an overspeed condition and
has engaged the suspension rope.
Swaged attachments or spliced eyes on wire suspension ropes cannot
be used unless they are made by the scaffolds manufacturer or by a
qualified person.
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. Clips must be installed according to the manufacturer's
recommendations, and retightened to the manufacturer's recommendations
after the initial loading clips are to be inspected and retightened
at the start of each subsequent work shift.
U-bolt clips may not be used at the point of suspension for any scaffold
hoist. When U-bolt clips are used, they must be placed over the dead
end of the rope, and the saddle placed over the live end.
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.
Electrical Hazards (top)
Suspended scaffolds are often made of metal and sometimes used in close
proximity to overhead power lines. These factors introduce the risk
of electrocution. However, proper clearance and maintenance reduce
this risk.
Scaffolds must be far enough from overhead power lines to prevent
any conductive materials (e.g. building materials, paint roller extensions,
scaffold components) that may be handled on the scaffold, at a distance
greater than 10 feet from the power line. Scaffolds are permitted to
be within 3 feet of insulated power lines.
Scaffolds and scaffold materials may be closer to power lines than
specified above when clearance is necessary to work on the power
line. However, before workers are allowed close proximity the power
company
or electrical system operator must be notified and the line must
be either de-energized or relocated, or after protective coverings
have been placed to prevent accidental contact with the lines.
Because metal frame scaffolds are conductive, power tools, cords,
etc. that suffer insulation failure can electrify the entire scaffold.
Therefore, all portable electric equipment must be protected by GFCIs
(ground-fault circuit interrupters) or an AEGCP (assured equipment
grounding conductor program.
Fall Protection (top)
Fall protection consists of either personal fall arrest systems or
guardrail systems, and must be provided on any scaffold 10 feet or
more above a lower level (two-point scaffolds require both PFAS and
guardrail systems). This is especially critical with suspended scaffolds,
because they often are operated at extreme elevations.
 Section
6  Appendix
A
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