Harness the power: trolley beam style systems vs. safety cables: which is better for fall protection?

Pit & Quarry, Nov, 2004 by Bob Babin

MSHA clearly has been given broad powers of enforcement for fall protection, having been issued a strong regulation open to relatively broad interpretation. The Federal Metal and Nonmetallic Mine Training, Safety and Health Standards, as enforced by MSHA under "30 CFR Subpart N--Personal Protection .15005 Safety Belts and Lines," state that "Safety belts and lines must be worn when there is a danger of falling."

In a recent Hazard Alert, Vernon R. Gomez, the administrator for Metal and Nonmetal Standards, noted that five deaths and 396 serious injuries have been caused by falls from trucks since 1992 in the mining industry. Climbing onto and getting off of trucks account for the biggest percentage of those accidents. Other causes include checking the load distribution on the truck, securing tarps on loaded trucks, and opening and closing hatches on tanker trucks. To help prevent these types of accidents Gomez recommends that operators:

1. Provide load-out facilities equipped with fall protection.

2. Require fall protection be used at all load-out facilities.

3. Provide fall protection for truckers when tarping trucks.

4. Train all truck drivers in the proper methods of getting on and off trucks.

If effectively designed to protect the worker from falling, guardrails are usually the least expensive and best solution. But, be careful. With guardrails, since not just the top of the work surface must be covered properly, access to tall vehicles or other walking/working surfaces must also be addressed with fall protection equipment. This ensures the worker ascending the vehicle will be protected any time he reaches an unsafe level above an impact surface. Furthermore, travel atop the vehicle or walking/working surface must be limited to safe access areas, which is seldom possible with a guardrail system.

"Hooking up" to a fall-protection system solves most of these problems. Safety belts, as described in the regulation, have fallen out of favor. OSHA outlawed safety belts several years ago for use on fall-protection systems in areas they control. In lieu of safety belts, the preferred harness is a vest-style, full-body fall protection harness.

Safety belts are considered to be dangerous. Safety belts distribute the full impact of a fall arrest to the waste of the victim. Fall-protection impact forces can reach levels as high as 950 lb. and have been known to cause death during a fall arrest. With a safety belt, which is little more than a large heavy-duty belt with a D-Ring attached to the rear, a fall arrest could easily damage a user's internal organs.

Full-body harnesses are better designed to comfortably and efficiently distribute the impact load suffered by a fall-arrest victim toward a safer, more durable area of the body in the thighs and buttocks. Virtually every test performed by harness manufactures clearly favors these harnesses. In a future article, harness selection will be covered in much greater detail.

In an effort to protect their workers from falls, many quarries have installed so-called "safety cables," made with high-strength braided stainless-steel wire ropes, in their maintenance shops. Safety cable fall-protection systems, on first impression, appear to be a very inexpensive solution to design and install. As you dig a little deeper, you begin to see the costs, as well as the problems.

First of all, the engineering requirements for safety cables add to the cost. Safety cable fall protection systems must be engineered by a licensed professional engineer, which requires drawings and detailed impact loading analysis calculations. The building must be able to withstand a significant load of not less than 3,600 lb.- per covered worker in the horizontal plane. This is a load few maintenance sheds are capable of supporting. Additionally, the safety cable system is not the most effective system available for the application, and you still have to worry about fall-related employee injuries.

The latest development in fall-protection systems, the trolley beam style fall protection systems, provide both a cost-effective and safe solution to all of these issue. Instead of a flexible wire rope, trolley beam systems employ a rigid beam to support the trolley. Advantages of this innovative technology are:

1. Whereas wire rope systems are flexible and typically allow falls of several feet before a fall arrest is accomplished, trolley beams are rigid. With a properly installed trolley beam system, fall arrests are typically accomplished within two feet or less. Falls into, or off the side of a vehicle, can lead to impact of the victim against a lower surface or against the ground level as well as serious scrapes, cuts and other injuries. Costly injuries such as hyperextended muscles and damaged backs are common with poorly arrested falls. To the knowledge of this author, no one has ever been injured during a fall arrest on a trolley beam system, but several workers have been injured during fall arrests on safety cable systems.