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Different types of scaffolding structure in safety

Types of Scaffolds

There are many different types of scaffolds used . The three major categories are:
  • Self-supporting scaffolds
  • Suspension scaffolds
  • Special use scaffolds
Supported scaffolds consist of one or more platforms supported by outrigger beams, brackets, poles, legs, uprights, posts, frames, or similar rigid support. Because frame scaffolds are the most common type of supported scaffold. 
The types of self-supporting scaffolds include:
  • Frame scaffold
  • Manually propelled/ Mobile scaffold
  • Pump jack scaffold
  • Tube coupler scaffold
  • Ladder jack scaffold
  • Pole scaffold
  • Specialty scaffold
Suspended scaffolds are platforms suspended by ropes, or other non-rigid means, from an overhead structure. Because two-point scaffolds are the most common type of suspended scaffold.
  • Single-Point Adjustable scaffold(Boatswain’s Chairs)
  • Two-Point Adjustable scaffold(Swing Stage)
  • Multiple-Point Adjustable scaffold
  • Multi-Level scaffold
  • Catenary scaffold
  • Float (Ship) scaffold
  • Interior Hung scaffold
  • Needle Beam scaffold
Special use scaffolds and assemblies are capable of supporting their own weight and at least 4 times the maximum intended load. The types of special use scaffolds include:
  • Form and Carpenter Bracket
  • Roof Bracket
  • Outrigger
  • Pump Jack
  • Ladder Jack
  • Window Jack
  • Horse
  • Crawling Boards
  • Step, Platforms, and Trestle Ladder

Supported scaffolds:

Supported scaffolds consist of one or more platforms supported by outrigger beams, brackets, poles, legs, uprights, posts, frames, or similar rigid support. Because frame scaffolds are the most common type of supported scaffold.

Frame or Fabricated:

Frame or FabricatedFabricated frame scaffolds are the most common type of scaffold because they are versatile, economical, and easy to use. They are frequently used in one or two tiers by residential contractors, painters, etc., but their modular frames can also be stacked several stories high for use on large-scale construction jobs. NOTE: Except where indicated, the same basic scaffold requirements that appear in this module also apply to manually propelled, pump jack, ladder jack, tube and coupler, and pole scaffolds, as well as the specialty scaffolds described in Supported Scaffolds. Additional requirements for these scaffolds can be found in their respective modules. The number one scaffold hazard is worker falls. 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. Specific requirements are described below.

Mobile

MobileMobile scaffolds are a type of supported scaffold set on wheels or casters. They are designed to be easily moved and are commonly used for things like painting and plastering, where workers must frequently change position.Scaffolds must be plumb, level, and squared.All brace connections must be secured.To prevent movement of the scaffold while it is being used in a stationary position, scaffold casters and wheels must be locked with positive wheel locks Platforms must not extend beyond the base supports of the scaffold, unless stability is ensured by outrigger frames Leveling of the scaffold, where necessary, must be achieved by the use of screw jacks.

Pump Jack

Pump JackPump jacks are a uniquely designed scaffold consisting of a platform supported by move able brackets on vertical poles. The brackets are designed to be raised and lowered in a manner similar to an automobile jack. Pump jacks are appealing for certain applications because they are easily adjusted to variable heights, and are relatively inexpensive.Pump jack brackets, braces, and accessories must be fabricated from metal plates and angles.Each pump jack bracket must have two positive gripping mechanisms to prevent any failure or slippage. When bracing already installed has to be removed so the pump jack can pass, an additional brace must be installed approximately 4 feet above the original brace before it is removed. The additional brace must be left in place until the pump jack has been moved and the original brace reinstalled.

Tube and Coupler

Tube and CouplerTube and coupler scaffolds are so-named because they are built from tubing connected by coupling devices. Due to their strength, they are frequently used where heavy loads need to be carried, or where multiple platforms must reach several stories high. Their versatility, which enables them to be assembled in multiple directions in a variety of settings, also makes them hard to build correctly. When platforms are being moved to the next level, the existing platform must be left undisturbed until the new bearers have been set in place. Braced before receiving the new platform.The use of couplers made from gray cast iron is prohibited. Tube and coupler scaffolds over 125 feet in height must be designed by a registered professional engineer.

Ladder Jack

Ladder JackA ladder jack scaffold is a simple device consisting of a platform resting on brackets attached to a ladder. Ladder jacks are primarily used in light applications because of their portability and cost effectiveness. All ladders used to support ladder jack scaffolds must comply with-Stairways and Ladders. Ladder jacks must be designed and constructed to bear on the side rails and ladder rungs. Ladders used to support ladder jack scaffolds must be placed to prevent slipping fastened to prevent slipping and or equipped with devices to prevent slipping.

Pole or Wood Pole

Pole or Wood PolePole scaffolds are a type of supported scaffold in which every structural component, from uprights to braces to platforms, is made of wood. OSHA has standards for two kinds: single-pole, which are supported on their interior side by a structure or wall, and double-pole, which are supported by double uprights independent of any structure.Because they have to be built from scratch and cannot easily be reused, pole scaffolds are considered old-fashioned and are rarely used today.When platforms are moved to the next level, the existing platform must be left undisturbed until the new bearers have been set in place and braced. Pole scaffolds over 60 feet in height must be designed by a registered professional engineer.

Specialty and Other Scaffolds

Specialty and Other ScaffoldsMany scaffold types regulated by OSHA standards are rarely used, and designed for a very narrow and specific range of applications. Requirement for these specialty scaffolds are addressed on this page. Scaffolds must not be more than 10 feet or two tiers in height, whichever is less.Scaffold platforms must be placed no higher than the second-highest rung or step of the ladder supporting the platform.

Suspended scaffolds:

Suspended scaffolds are platforms suspended by ropes, or other non-rigid means, from an overhead structure. Because two-point scaffolds are the most common type of suspended scaffold.

Catenary scaffold:

Catenary - image points out the struture above, vertical pickups hanging below the structure, and the platform hanging from the vertical pickups using by hook stops and anchored wire rope
A catenary scaffold is a scaffold consisting of a platform supported by two essentially horizontal and parallel ropes attached to structural members of a building or other structure.Platforms supported by wire rope must have hook-shaped stops on each of the platform to prevent them from slipping off the wire ropes. These hooks must be positioned so that they prevent the platform from falling if one of the horizontal wire ropes breaks. Wire ropes must not be over-tightened to the point that a scaffold load will overstress them. Wire ropes must be continuous and without splices between anchors.Each employee on a catenary scaffold must be protected by a personal fall-arrest system.

Interior Hung

Interior HungAn interior hung suspension scaffold consists of a platform suspended from the ceiling or roof structure by fixed-length supports.Interior hung scaffolds must be suspended from roof structures (e.g., ceiling beams).Roof structures must be inspected for strength before scaffolds are erected.Suspension ropes/cables must be connected to overhead supports by shackles, clips, thimbles, or equivalent means.

Multi-point Adjustable:

Multi-point AdjustableA multi-point adjustable scaffold consists of a platform (or platforms) suspended by more than two ropes from overhead supports and equipped with means to raise and lower the platform(s) to desired work levels. An example of this type of scaffold is a chimney hoist, used in chimney-cleaning operations.Multi-point adjustable scaffolds must be suspended from metal outriggers,brackets,wire rope slings,hooks or means that meet equivalent criteria for strength, durability, etc.When two or more scaffolds are used they must not be bridged together unless design allows them to be connected,bridge connections are articulated and hoists are properly sized.

Single-point Adjustable

Single-point AdjustableA single-point adjustable scaffold consists of a platform suspended by one rope from an overhead support and equipped with means to permit the movement of the platform to desired work levels. The most common among these is the scaffold used by window washers to clean the outside of a skyscraper (also known as a boatswain's chair).The supporting rope between the scaffold and the suspension device must be kept vertical unless designed by a qualified person, accessible to rescuers,protected from rubbing during direction changes.

Float (ship)

Float (ship)A float, or ship, scaffold is a suspension scaffold consisting of a braced platform resting on two parallel bearers and hung from overhead supports by ropes of fixed length.Platforms must be supported by and securely fastened to a minimum of two bearers extending at least 6 inches beyond the platform on both sides.open connections must not allow the platform to shift or slip.When only two ropes are used with each float Ropes must be arranged to provide four ends that are securely fastened to overhead supportsand Each employee on a float (ship) scaffold must be protected by a personal fall-arrest system.

Multi-level

Multi-levelA multi-level scaffold is a two-point or multi-point adjustable suspension scaffold with a series of platforms at various levels resting on common stirrups.Multi-level suspended scaffolds must be equipped with additional independent support lines that are equal in number to the number of points supported,equal in strength to the suspension ropes and rigged to support the scaffold if the suspension ropes fail. Independent support lines and suspension ropes must not be anchored to the same points. Supports for platforms must be attached directly to support stirrups (not to other platforms).

Needle Beam

Needle BeamThis simple type of scaffold consists of a platform suspended from needle beams, usually attached on one end to a permanent structural member. Scaffold support beams must be installed on edge.Ropes or hangers must be used for supports. Ropes must be securely attached to needle beams. Support connections must be arranged to prevent the needle beam from rolling or becoming displaced.Platform units must be attached by bolts or equivalent means. Cleats and overhang are not considered adequate means of attachment.

Two-point (swing stage) Electrical Hazards

Two-point adjustable suspension scaffolds, also known as swing-stage scaffolds, are perhaps the most common type of suspended scaffold. Hung by ropes or cables connected to stirrups at each end of the platform, they are typically used by window washers on skyscrapers, but play a prominent role in high-rise construction as well. 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.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.Because the platform is the work area of a suspended scaffold, an inspection requires safety checks of both the platform structure and how the platform is used by the workers. Even if a suspended scaffold has been assembled in compliance with every applicable standard, employers and workers must continue to exercise caution and use sound work practices to assure their safety. Extreme weather, excessive loads, or damage to structural components can all affect a scaffold's stability.

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