Part Two: Personal Fall Arrest Systems as Fall Protection on Scaffolds

In many cases, a personal fall arrest system (PFAS) will the type of fall protection system used on a scaffold. The user might implement a PFAS if guardrails are not present, such as an area where material is being loaded onto the scaffold. A PFAS might also be used in addition to the guardrails as a backup system.

In the petrochemical industry it is a common practice to require both guardrails and PFAS. During erection and dismantling of the scaffold, a PFAS might be used by erectors before guardrails are installed. PFAS systems are covered in OSHA in 1926.502(d) and ANSI/ASSE Z359.

The ABC’s of a Personal Fall Arrest System
The key components of a PFAS are the Anchorage, the Body wear, and the Connecting equipment between the body wear and the anchorage—the ABC’s of a PFAS.

Anchorage
The anchorage must be a structural component that will support either a 5,000 lb. impact force, or as an alternative maintains a safety factor of two (1926.502(d)(15)). To maintain this safety factor, the anchorage must be able to withstand at least two times the maximum impact force which could be generated during a fall. How can this be determined? When shock (energy) absorbers are used on the lanyard and the fall distance is limited to 6 ft. or less, the impact force should be 900 lbs. or less. When self-retracting lifelines are used and attached above the worker as required by manufacturers, the maximum impact force is likewise 900 lbs. or less. Consequently, the anchorage must be able to withstand 1800 lbs. in order to maintain the safety factor of two.

It is an OSHA requirement that the anchorage point be located so that free fall is reduced to six feet or less. If a greater free fall is allowed, the impact forces will also be greater.

Body Wear
Body wear should be a full body harness worn snugly, with the leg straps positioned up close to the groin area, not hanging loosely close to the knees. The back D ring should be positioned up high in the shoulder region, not down low by the lower back. The back D ring is used for attachment of the lanyard, not side or front D rings.

Connector
The third component is the connector between the harness and the anchorage. The most common connector is a 6 ft. long lanyard which incorporates a shock (energy) absorbing unit. Multiple end connectors for the lanyard are available such as standard snap hooks, larger 2.5” snap hooks, and carabineers. Other devices for connecting the lanyard to the anchorage are available including devices to attach to I beams, concrete forms, roofs, rebar, scaffold tubes, and others. Component compatibility is an important consideration. Standard size snap hooks should be attached to a properly sized “D” ring. Some lanyards have “tie back to itself” capability.

If the lanyard cannot be attached directly to the anchorage, a vertical lifeline system, retractable lifeline, or horizontal lifeline system can be used. The vertical lifeline is a special wire rope or synthetic fiber rope with a tensile strength of at least 5000 lbs. This line runs from the anchorage above down to the location of the worker. A device called a rope grab is attached onto the vertical lifeline at the workers location, and the worker attaches a lanyard from the harness to the rope grab. A self-retracting lifeline (SRL) is a unit which incorporates a lifeline in a special housing. The lifeline feeds into or out of the unit at slow speeds, the same as a seatbelt in an automobile. If an accelerated free fall occurs, the SRL locks the lifeline. Horizontal lifeline systems may also be used as an anchorage. Note that horizontal lifeline systems will experience an amplification of the original vertical impact force, must be designed by a qualified person, and preferably include an energy absorber in the horizontal lifeline itself.

Disadvantages of Particular Connections
The direct connection with shock absorbing lanyard requires clearance room to be effective. The worker’s feet may end up 15-16 ft. below the anchorage including the height of the worker, the 6 ft. of the lanyard, the potential 3.5 ft. of elongation of the shock absorber, and the rising of the harness D ring during impact. The SRL should only be used above the worker, not at a lower level like at the workers feet. A SRL might fail if used in that position. Horizontal lifelines will experience deflection and vertical lifelines will experience elongation during impact. These must be considered when calculating required clearance distance.   

All of the above listed equipment is available from reputable PFAS manufacturers with new technology frequently added. Today portable “Y” type SRL lanyards, suspension trauma relief steps, and tool tethers are available.  The manufacturers should provide documentation that the system has been tested in accordance with OSHA and ANSI protocols. Written instructions should be provided.