LEARN MORE about fall protection basics
Learn the fundamentals of good fall protection practice
The U.S. Department of Labor Occupational Safety and Health Administration (OSHA) specifies under Title 29 of the Code of Federal Regulations that individuals working at heights must be protected from fall injury. Fall protection as defined in 29CFR includes:
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Fall guarding (preventing persons from entering a fall hazard area; e.g., with guard rails)
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Fall restraint (preventing persons who are in a fall hazard area from falling, e.g., with fall restraint lanyards)
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Fall arrest (safely stopping a person who is already falling).
Fall guarding
Some examples of fall guarding equipment are mobile barriers and contractor barricade tape. Most fall guarding is accomplished with temporary or permanent railings or parapets.
Fall restraint
It is important to understand the difference between a fall restraint system and a fall arrest system. These are both most commonly used in the construction industry but may apply to many other situations where employees must work at heights, such as commercial aircraft maintenance or naval maintenance.
Fall restraint systems consist of the equipment used to keep an employee from falling in the first place; for example, a tie-off system that "restrains" the employee from falling off an elevated working surface.
Fall arrest
There are two major types: general fall arrest, such as nets; and personal fall arrest, such as lifelines. The most common example of fall arrest in the workplace is the personal fall arrest system, or PFAS, which is a series of components designed to safely arrest a worker's fall, preventing him from striking the next lower level, and minimizing the possibility of serious injury.
Personal fall arrest systems must include four elements, referred to as the ABCD's of fall arrest:
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A - Anchorage – a fixed structure or structural adaptation, often including an anchorage connector, to which the other components of the PFAS are rigged;
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B - Body wear – a full body harness worn by the worker;
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C - Connector – a subsystem component connecting the harness to the anchorage, such as a lanyard;
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D - Deceleration device – a subsystem component designed to dissipate the forces associated with a fall arrest event.
Each of these elements is critical to the effectiveness of a personal fall arrest system. There are many different combinations of products that are commonly used to assemble a personal fall arrest system, and each must meet strict standards (ref 29CFR1910.66 appendix c). The specific environment or application generally dictates the combination or combinations that are most appropriate.
Energy absorption
To arrest a fall in a controlled manner, it is essential that there be sufficient energy absorption capacity in the system. Without this designed energy absorption, the fall can only be arrested by applying large forces to the worker and to the anchorage, which can result in either or both being severely affected.
Consider the difference in dropping an egg onto a stone floor or into soft mud. For the same fall distance and weight of egg (the input energy), there will be more damage with the stone floor, as the arrest distance is smaller and so forces must be higher to dissipate the energy. With the soft mud, the arrest distance is longer and so arrest forces are lower. The egg is still stopped, but is, hopefully, undamaged.
Most fall arrest parts and systems are designed to the standard contained in Federal OSHA 29CFR1910.66 appendix c, a force-type design standard that accounts for required energy considerations. The standard mitigates PPE interchangeability problems, allows wide use by designers not versed in high-rate energy methods, and limits the force into the worker to a survivable level.
Actual loads on the user and anchor-anchorage vary widely, depending on user weight, height of fall, geometry, and type of line/rope. Excessive energy into the support and user is avoided by using energy-absorbing PPE designed for the 1800 pounds maximum of the referenced Federal OSHA standard.
Vertical life line
The most common fall arrest system is the Vertical Life Line: a stranded rope that is connected to an anchor above, and to which the user's PPE is attached either directly or through a "shock-absorbing" (energy-absorbing) lanyard. Once all of the components of the particular lifeline system meet the requirements of the standard, the anchor connection is then referred to as an anchorage, and the system as well as the rope is then called a "lifeline".
Anchors used for lifeline anchorages are designed for 5000 pounds force per connecting user, and the standard permits an anchor to deform in order to absorb energy. (Adhesive anchors have higher design requirements because of aging loss.)
The rope can be lifeline rope, which stretches to lengthen the fall distance as it absorbs energy, or static rope, which does not stretch (and thus limits the fall distance), but requires the fall energy be absorbed in other devices. It is essential that the PPE be rated for Fall Arrest and that PPE used with static line include an energy absorber. While energy-absorbing lanyards hold in excess of 5000 pounds when fully absorbed, most limit the load during the fall to under 1400 pounds.
Horizontal life line
Another common system is a horizontal life line (HLL). These are linear anchoring devices that allow workers to move along the whole length of the anchor, usually without needing to disconnect and fixing points of the anchorage.
It is normally essential to include energy (or shock) absorbers within HLL in addition to those within the workers' PPE. Without such absorbers, the horizontal life line cannot deform significantly when arresting the fall. Because of the geometry of pulling across the horizontal line, this in turn results in large resolved forces being generated within the anchor system, sufficient to cause failure of the anchorage. This can occur even with energy absorbers being included in the PPE of the worker.
The load and horizontal line geometry in horizontal lifelines usually creates falls in excess of the six-foot limit of the standard, limiting HLL design to standard-defined "qualified persons". (The recognition of these basic weaknesses has resulted in most temporary "wrapped structure" HLL anchors, which were anchors made from a wire rope wrapped around a structure and its ends fastened together by wire rope clips, being replaced by fixed-point anchors or HLL systems designed by defined "qualified" persons.)
Fall clearance
In arresting a fall in a controlled manner, the distance required to arrest the fall must be considered. Federal OSHA limits the fall distance to six feet unless the specific system is designed by a "qualified person" meeting the requirements of OSHA 29CFR1910.66 appendix c. The user also may not fall so as to strike protrusions or adjoining walls during the six-foot fall.
The safe fall distance is a function of the "fall factor" and the deployment of the "energy absorbers". As a rule of thumb, for a factor two fall, a fall distance of approximately six meters will be required. This is equivalent to two stories of a building. If the fall clearance is less than this, the worker may strike the ground before fall is arrested.
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