What Does
Safety Net Mean?
A safety net is a fall protection device commonly used in construction work. The net is a mesh barrier that is stretched out and anchored below the level where work is taking place in order to catch people or objects that fall over the edge of the working surface.
Safety nets are fall arrest systems, meaning they limit the fall distance and dissipate the impact energy of the fall. They cannot prevent a fall from happening, but can prevent or limit the severity of fall injuries.
Safeopedia Explains Safety Net
Safety nets came to prominence thanks to Joseph Strauss, the chief engineer overseeing the construction of the Golden Gate Bridge in the 1930s. He required the installation of a manila rope safety net below the bridge, which saved the lives of 19 workers over the course of the project.
In 1937, however, a scaffold collapsed and tore through the net, resulting in 10 workers losing their lives. This tragic incident led to further developments in the manufacturing of safety nets, which are now stronger and follow a standard rating system.
Safety Net Classes
Safety nets can be knotted or unknotted with a square or diamond-shaped mesh. They are classified as Class A (2.3 kilojoules) or Class B (4.4 kilojoules) based on their absorption capacity and as Class 1 (60 mm) or Class 2 (100 mm) based on the mesh size.
A Class B1 safety net, then, is one that has a 6o mm mesh and the capacity to absorbs 4.4 kilojoules of energy.
Types of Safety Nets
There are two main types of safety nets: those meant for catching debris and those designed to catch people.
Safety nets designed to catch falling workers are made of industrial grade nylon. The materials used for debris-catching safety nets vary based on the weight and force it is expected to withstand.
- Light Duty Safety Net: Designed to catch lightweight items only. Made of PVC-coated polyester, with a fine mesh size (typically 1/8″ x 3/16”). Light duty safety nets must meet the ASTM D5034 breaking strength requirement of 178 lbf (pound force) at the length and 94 lbf at the width.
- Medium Duty Safety Net: Designed to catch larger items, like hand tools and hardware. Made of knit polyester, with a mesh size of 3/8″ x 1/2″. Medium duty safety nets must meet the ASTM D5034 breaking strength requirement of 107 PSI for the warp and 65 PSI for the fill.
- Heavy Duty Safety Net: Designed to catch heavy materials, like bricks. These are two-ply netting systems that combine a smaller mesh debris liner with a larger mesh structural net. Heavy duty safety nets require a test load of 1,200 lbs and a design load of 2,000 lbs.
OSHA’s Guidance on Safety Nets for Fall Protection
The Occupational Safety and Health Administration (OSHA) provides regulations for safety nets, which can be found in its 1926.105 standard. According to this standard, safety nets must be used when the work surface is more than 25 feet above the lower level or where using safety lines, safety belts, scaffolds, ladders, temporary floors, and catch platforms is impractical.
Safety Nets as Fall Protection: When They’re Used
Safety nets are a crucial component of many fall protection plans. They are a final line of defense to protect workers after all other fall protection measures have failed.
Like all workplace hazards, control methods for working at heights must be implemented using the hierarchy of controls. Fall hazards, however, deviate from the standard hierarchy. When implementing controls for work at heights, the order is as follows:
- Elimination: Where possible, the fall hazard should be eliminated entirely. This can be accomplished by finding ways to do the work at ground level, using drones to conduct inspections at heights, or installing HVAC systems at ground level instead of rooftops so they can be maintained without exposure to fall hazards.
- Passive Fall Protection: Physical barriers that prevent workers from coming into contact with fall hazards, such as guardrails or hole covers.
- Fall Restraint Systems: Systems that attach a worker to an anchor point and limit how far they can move, thereby keeping them from wandering too close to unguarded edges and other fall hazards.
- Fall Arrest Systems: Systems that cannot prevent a worker from falling but can stop the fall before they reach the lower level, thereby reducing the risk of severe injury or fatality.
- Administrative Controls: Warning lines, signs, controlled access zones (CAZ), and policies meant to discourage workers from going near fall hazards.
Safety nets are fall arrest devices, since they are designed to stop a fall in progress. As such, they are low on the hierarchy of controls and should only come into play when passive fall protection and fall restraint systems cannot be implemented or have failed.
Work that might require the use of safety includes:
- Bridge construction and repair
- High-rise building projects
- Construction or repair work taking place above an area with pedestrian traffic
Advantages and Disadvantages of Safety Nets
Advantages
- Significantly reduces the risk of serious injuries and fatalities
- Passive fall protection system that does not rely on worker expertise
- Provides reassurance and peace of mind for those working near fall hazards
- Can be used in conjunction with scaffolding
- Less costly than many other fall protection systems
- Reduced cost of worker compensation and claims
Disadvantages
- Safety nets cannot prevent a fall from happening
- Incorrect installation will affect its ability to arrest a fall and protect workers
- Personnel safety nets with larger netting may not prevent tools and debris from falling to a lower level
- Sharp or asymmetrical tools may damage or entangle the net
- Difficult to install where complex architectural designs are involved
Maintenance and Inspection Requirements
Proper maintenance is essential for safety nets to be effective. Every net must be regularly inspected for wear and tear and be free of caught debris.
Steps for maintaining and inspecting safety nets include:
- Checking the net for cracks, concrete remains, deterioration, and anything else that might impair its functionality
- Removing any object that falls into the net
- Inspecting anchors and fasteners to ensure that they are in good condition and will not break or unhook when weight is dropped into the net
- Replacing the net when it has exceeded the useful life specified by the manufacturer
Safety Net Installation and Performance
Safety nets must extend at least eight feet beyond the edge of the work surface and be as close to the work surface as possible (and no more than 25 feet below).
There must be sufficient clearance between the net and the surface below to prevent a falling worker from making contact with the surface. To determine the clearance, the net must be tested for impact loading.
Safety nets must also meet the following criteria:
- Maximum mesh size of 6” x 6”
- Minimum impact resistance of 17,500 foot-pounds
- Performance standard certified by the manufacturer, with a label of proof test
- Edge ropes with a minimum breaking strength of 5,000 pounds
- Net fasteners (safety hooks and shackles) made of forged steel
According to OSHA, a competent and qualified person must be present during the installation of the safety net. Every safety net must also be drop tested at the site:
- After initial installation and before use
- When removed and relocated
- After repairs to the net
- Every six months
Safety Nets as Part of a Fall Protection Plan
Safety nets are an important part of a comprehensive fall protection plan. Every site should have a written program that reflects the unique features and needs of the site. It should include all the fall protection measures implemented, how they must be used, rescue plans, and which personnel are responsible for supervision and training.
All employees must be trained in the use and maintenance of fall protection equipment, including safety nets. They must understand how the safety net works, as well as its limitations. Safety nets are a last line of defense against fall hazards and must be treated accordingly.
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