Horizontal Lifelines: Don't Leave Them Hanging
These systems save lives if designed and used correctly, but an error in just one component or worker behavior can generate a very serious injury or fatality.
- By Michael C. Wright, PE, CSP, CPE, Moniqua Suits
- Mar 01, 2004
IT is a beautiful sunny day in the Midwest, and a construction crew is setting the decking on bridge girders located over an interstate highway. Their horizontal lifeline (HLL) system is attached to each girder with a steel cable height of approximately 42 inches (waist height) and 2-inch squared steel posts supporting the steel cable system.
Three workers are attached to the HLL system. One worker wears a 6-foot energy-absorbing lanyard, and the other two are wearing self-retracting lanyards (SRL). The 6-foot lanyard snaphooks are attached directly to the HLL system, and the SRLs are attached to the HLL steel cable by small, 4-inch aluminum carabiners.
At midday, the worker wearing the 6-foot energy-absorbing lanyard falls from the HLL system. The impact lowers the HLL cable below the foot level of the other employees. As a result, his fall pulls the other workers off with him because the SRLs were attached to the steel cable at only 42 inches above the working surface and one employee was wearing a 6-foot lanyard. Now all three workers are hanging, twisted like fish on a stringer, approximately 8 feet below the bridge girders. And then an oncoming semi trailer approaches. Rescue Me!
At a general industry site, skilled trades are performing maintenance on a 25-ton overhead crane system. As the four workers walk across a 12-inch-wide crane runway girder, they are trying to balance themselves by holding onto utility pipes and other structures hanging from the roof framing steel.
They are conducting a quarterly maintenance on the crane to lube the wheels and inspect the cables, brakes, and other electrical components. The girder is slippery from machine cutting oils, which causes one worker with a 6-foot lanyard attached to slip and pull his co-workers along with him. As they fall, their feet hit the machinery below, crushing the legs of two employees. The other two employees, who were using SRLs, are safely suspended above the machinery.
Rescue is difficult because it had not been pre-planned and the machinery covers a large area of the plant floor, making it hard to reach the fallen employees. Rescue Me!
Horizontal lifelines often are the first line of defense at construction sites and manufacturing facilities. This is true because many times, organizations have not completed the pre-planning process, putting them in a rush to address fall protection hazards. Unfortunately, rarely is a HLL system designed by a Qualified Person (QP), seldom does a trained Competent Person (CP) supervise its use, and often the At-Risk Workers (ARW) are not adequately trained to pre-plan their workplace activity and mobility requirements.
Horizontal lifelines are complex, involving mathematical equations such as cantenary and parabolic. The fallen worker may experience residual effects such as venous pooling, which becomes a life-threatening factor when rescue methods do not address suspended worker physiology. HLLs can and do save lives if designed and used correctly, but an error in just one component of the system or worker behavior can generate a very serious injury or fatality. So, how do you Rescue Me?
Role of the Qualified Person in Horizontal Lifelines
As a structural engineer and after my first 8-hour course on fall protection I felt confident that what I was doing was accurate. However with each class completed, I realized the significance of learning more so that I could verify that what I was doing was safe. After achieving the Certified Safety Professional license, my engineering approach to safety is definitely more complete.
--Michael C. Wright, PE, CSP, CPE
OSHA will provide the forces necessary to design by, but it is up to structural engineers with a sufficient background in safety and specialized training in fall protection to take these forces and develop design standards that do not negatively affect work tasks and the required mobility. This person is called a Qualified Person.
In 29 CFR 1926.32(m), OSHA states: "Qualified" means one who, by possession of a recognized degree, certificate, or professional standing, or who by extensive knowledge, training and experience, has successfully demonstrated his ability to solve or resolve problems relating to the subject matter, the work, or the project (fall protection).
One of the most significant roles a QP performs in a managed fall protection program is the design, installation, and supervision of HLLs. The specialized training, knowledge, expertise, and insight a QP provides is extremely valuable because there are many design and use factors involved with HLL systems, such as feasibility, swing fall, clear height distances, anchorage systems, personal fall protection systems, workplace activities, required worker mobility, and prompt rescue.
The first item to verify is making certain a QP designed the HLL system. Otherwise, you cannot be certain the system is going to be adequate until a fall occurs. Remember, the design for single-worker use will be different than for multiple-worker use.
In the case of a non-designed system, if one worker falls the other workers also may be pulled off. In addition, the structure to which the HLL system is anchored may not be able to withstand the horizontal and vertical forces a fall generates, resulting in a sudden rupture of the anchorage or support structure.
Other design and use considerations include clear height distance, allowable vertical cable sag, proper selection of personal fall arrest equipment, and specifications for the cable materials. Although worker safety is paramount, management also should consider the potential damage a fall can cause to machinery and process lines, as well as the impact that associated downtime and indirect costs will have on productivity and profitability.
The Qualified Person is liable in determining that the Competent Person is adequately trained and experienced in the use and supervision of the use of the HLL system. Otherwise, the QP must be on site during the use of an HLL system as required by OSHA's 1926.502 (d) (8).
The inter-relationship of the CP and the QP in regard to HLL systems is significant. If the CP is not adequately trained and experienced in the areas of fall hazard abatement and rescue, he may select the wrong fall protection system. The CP needs to understand why he cannot change the HLL specifications or the fall protection systems selected by the QP. For example, if the Qualified Person designs a system for only SRLs to be used, but the CP decides to use 6-foot lanyards (which are less expensive), the maximum arresting forces (MAF) on the HLL system will increase, which in turn increases the total clearance distance requirement. If this occurs, it would be like an accident waiting to happen.
Additional CP responsibilities include: day-to-day verification of the HLL system components and cable sags, preventing personal fall arrest equipment lines from tangling, and developing workplace activity procedures that allow workers to perform tasks in conjunction with one another while they are connected to the same HLL system. The CP needs to have an adequate rescue plan in place before work at height occurs. This is especially critical for HLL systems because multiple victims may need to be rescued simultaneously. The Competent Person is responsible for the safety and supervision of the At-Risk Workers using an HLL system while working at heights.
Role of the At-Risk Worker
The AT-Risk Worker (ARW) must be adequately trained before using HLL systems. If not, workers may develop a false sense of security using an HLL system and become careless or stretch the boundaries of its use, thinking that by being connected they are safe.
When using the fall protection equipment, the ARW should not exceed the manufacturer's recommended angle of use for the equipment. Typically, HLL systems will have to be much higher than first anticipated to be able to limit the angle of use for the equipment. Most of the time we see workers with the HLL system waist- or head-high above the working surface, when actually it needs to be higher so that the manufacturer's recommended angle of use provides more protection during workplace activities.
It is crucial that the ARW understands the potential damage of the impact of a swing fall. Rule of thumb: Remember the event of swinging into something has the same potential energy as a vertical free fall on an object of the same height and generates a potential force of 5,000 pounds.
Adequate training on fall protection equipment will help the ARW to understand that sudden or quick movements while using fall protection equipment may engage the system to lock and/or pull a co-worker into a fall. Also, the ARW should be trained on how to move in harmony with other co-workers, in order to prevent entanglement or accidentally pulling one another off the working surface.
Knowledge and use of the Hierarchy of Controls empowers Qualified and Competent Persons to use elimination and engineering controls as solutions to fall hazard abatement before considering horizontal lifelines. The Hierarchy of Controls indicates HLLs may prove to be a higher risk with high long-term costs and more defeatable due to the human behavior errors.
Workers using HLL systems must be adequately trained in fall protection and receive advanced training in the use of HLLs. Currently, there are no national standards for HLL systems, just one more reason for the QP to play such an integral role in the design, installation, and supervision of HLL systems.
The above information provides an overview of the issues that should be considered when using HLL systems. The following information directs our attention back to the scenarios described in the beginning and how they might have been avoided.
The Bridge Construction Solution
Based on the outcome, it is apparent this HLL system was non-designed or improperly designed. A QP would have designed the system above their heads (say, 8-10 feet) and required that all workers use SRLs attached to the HLL system with a metal alloy carabiner versus an aluminum carabiner. Aluminum carabiners will experience excessive wear in a very short time as a result of being used on steel cable. Their use is not the best practice.
Also, a QP would not permit the connection of a snaphook directly to a HLL cable (the sidegate of the snaphook may be forced open by the cable during the fall of a worker). A QP would specify the structural support. Given the structural engineering and fall protection safety knowledge a QP must possess, this HLL system could have been designed to eliminate the hazard of being struck by traffic flow--the system would safely stop the workers before there was a possibility of being hit by vehicles.
The General Industry Solution
In this instance, the QP could have designed a fixed-rail HLL system with a trolley attached and a short SRL lanyard. This would provide minimal deflection with the horizontal fixed-rail system, and the SRL would typically arrest the fall within 24 inches, allowing the fall victim to self-rescue or permitting easier rescue by others.
This design would keep the employees from experiencing severe injury, potential fatality, or difficult rescue and would lessen the potential of damage to the machinery or excessive downtime. In addition, a properly designed system would lessen the possibility that a fallen worker would pull off other workers.
There are fall hazard exposures that call for the use of horizontal lifeline systems, but it should not be the first method chosen because of the many complex issues associated with its use and high long-term costs. By utilizing the specialized knowledge and experience of a Qualified Person, you will be able to approach fall abatement issues with the confidence you are protecting the longevity of workers' lives and your business's profitability.
This article originally appeared in the March 2004 issue of Occupational Health & Safety.