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Fixed Installation Fall Protection Systems: Guardrail Systems, Safety Cables and Trolley Rails
by Bob Babin

There are basically two categories for fall protection applications: temporary tie-offs and fixed installations. Temporary tie-offs typically describe infrequently needed fall protection requirements, such as emergency machinery maintenance and construction applications. This category is so broad that it defies simple description.
Fixed installations, however, typically include regularly scheduled requirements such as loading (or unloading) railroad cars and tractor trailers, as well as applications requiring climbing onto large machinery and equipment. This article will address the most common options chosen for fixed installations.

Guardrail Systems
Guardrail systems, frequently referred to as “passive systems,” are most frequently used for applications in factory environments, but only on a limited basis for applications over vehicles such as hopper rail cars, tanker rail cars and tanker trailer trucks. For vehicle applications, guardrail systems typically do not satisfy OSHA fall protection requirements, since guardrails surrounding the perimeter of a rail car may add some convenience to the worker and a little additional fall prevention. They do not protect a worker from falling into open hatches or gaps between rail cars.
Some manufacturers offer standard fixed installation platforms and portable platforms on wheels that include telescoping drop down handrail cages. These systems are typically designed to increase the height of the enclosure provided by the existing handrails on tanker vehicles. But, unless these guardrail systems prevent falls into open hatches and sliding falls under the vehicle’s built-in handrails, they will not solve the OSHA requirements. Nor will they eliminate the most significant fall hazard on the vehicle.
To comply with existing OSHA regulations, a fall arrest system is required to arrest falls effectively. Several recent accidents involving serious injuries and fatalities have accentuated this issue and OSHA is looking more closely at these systems.
Because of slippery conditions in cold, windy, wet or icy weather and because of the tall working height (13-15 feet) atop these vehicles, many companies now install a combination of fall prevention and fall arrest systems. These include an access system with guardrails, non-slip staircase and platform, a counterweighted drop down gangway to ascend the vehicle, and a horizontal fall arrest system with self-retracting lifeline for use while atop the vehicle. These systems provide both OSHA compliance and maximum worker safety.

Safety Cable Fall Protection Systems
Horizontal lifelines, most commonly referred to as “safety cables,” have been around for more than 40 years. They represented the state-of-the-art in fall arrest systems until the early 1990s. Most safety cable systems use braided wire rope cables, sometimes referred to as aircraft cables, attached to strong anchor supports at both ends of the system. Some use linear polyester cables, a relatively soft and flexible plastic material, with a more durable coating of an orange plastic that serves as an exterior sleeve to help protect the surface from wear.
OSHA and ANSI regulations require horizontally-mounted anchorage points designed to support 5,000 pounds per user. Therefore, a three-man-up system requires anchorage loading capability for the anchor points of 15,000 pounds at each end of the cable. A man-rated trolley is used to support the user’s personal lifeline, and the trolley is designed to traverse the horizontal lifeline across the span of coverage.
When vertical columns are used to support the ends of the safety cable, heavy concrete foundations are generally used to anchor the columns into the earth. These foundations are typically large in diameter and are deeply set into the earth to support the torque load constantly exerted against the sides of the end columns.
The two end columns are built of heavy-gauge steel with large steel base plates for mounting the anchor bolts. They usually include reinforcing gussets to minimize column deflection. The reach of the column’s horizontal extension (gooseneck) is held to a minimal length to reduce torque load on the column. When most engineered safety cable systems exceed approximately 40 feet in coverage length, intermediate attachments are added to support the cable in mid span. If the system is a free-standing version supported by vertical columns, lighter duty columns are added at approximately 40-foot intervals to minimize cable deflection (and reduce total anticipated fall distance) during fall arrests.
At one time, there were several safety cable style fall protection system manufacturers, with several different designs used for the trolleys. Safety cable sales have declined in recent years so most of these manufacturers have diversified into trolley beams.
Earlier safety cable systems suffered a common problem--cable trolleys hung up on the intermediate support connections for the cable. Several documented falls were actually caused by these systems when the trolleys jammed and suddenly stopped behind a walking user, essentially pulling him over backwards as he tried to walk forward. This was particularly hazardous for railroad car applications when the user was stepping from car to car and could fall into the gap between rail cars.
Several different trolley designs are on the market, and virtually all are designed to pass by intermediate connections on the lifeline. However, some are much more efficient than others at this necessary function. Most of the manufacturers have addressed this issue and many have effectively solved the problem with improved trolley designs.
To comply with OSHA regulations, all safety cable systems must be built to a certified professionally engineered design, and all legitimate system manufacturers provide this service with their product.
There are three principle areas of concern with safety cable system designs:

1. To minimize the total allowable fall distance, OSHA has adopted a “310-pound maximum weight allowance” for each user of the system. This shall include not only the person, but also his or her clothing, shoes and anything else being carried.

2. The application requirements must be carefully analyzed, including maximum allowable fall distance (regardless of the height, the system must not allow the fall arrest victim to fall far enough to strike an impact surface) and total fall distance (by law, a fall must be arrested within a maximum fall distance of six feet regardless of the underside clearance).

3. Secondary falls must be considered. Secondary falls are described as the bounce introduced by the elastic properties of the tensioned cable, commonly referred to as “springback.” Since a falling worker usually can react in time to brace himself somewhat for the primary fall, secondary falls (during which the wo rker is wrenched awkwardly by the springback reaction of the tensioned cable) may be more damaging than the primary fall. Virtually all safety cable systems offer some type of optional shock absorbing dampeners to soften the load on a user during a fall arrest. The effectiveness of these devices varies considerably and none are totally efficient at eliminating secondary falls due to safety cable fall arrests. Secondary falls continue to be the most significant design limitation.

4. Number of users is another consideration. Allowing more than one user to be simultaneously attached to a safety cable system subjects more than one person to a potential hazard. If any one of the users falls near someone else who is attached the system, the other user is in danger as the cable deflects while arresting the fall of the first victim. In other words, a second fall can be caused by the first fall arrest.

Due to the increasing fall distance created by cable deflection, the user’s weight is a significant factor in the fall arrest equation. It is technically impossible to manufacture a flexible cable material that will not elongate and spring back under a fall arrest. It also is impossible to produce a cable that will span between two anchor points without deflection. Most manufacturers adjust the tension of their cables to a static (constant tension) load of 1,200 pounds.
Due to the unavoidable physical elongation of the cable over time, virtually all safety cable systems must be inspected and the tension readjusted annually. To maintain their “engineered rating,” manufacturers further require the annual inspection to be performed by a factory-trained, certified technician. Between annual tension adjustments, the maximum fall distance increases as the cable stretches.
Virtually all designers of safety cable systems claim to use computer models to design their systems. However, these designs are only as good as the information fed into the computer, so exercise extreme caution when considering safety cables.
One last important point. After arresting a fall, all safety cable systems should be taken out of service immediately and quarantined until thoroughly inspected by a professional. Virtually all professionally-engineered safety cable systems include replaceable components designed to reduce the impact shock to the fall arrest victim during a fall arrest. Most of those components require those parts to be replaced after a fall arrest before the system can be re-commissioned. That means considerable cost and expensive downtime.

Trolley Rail Fall Protection Systems
Trolley rail style fall arrest systems have been around for years. But, since no practical mechanism had been developed to support trolley beams until the mid 1990s, these systems were mostly limited to indoor applications where the rigid trolley beam could be attached to an existing structure (such as roof rafters). With the development of an integrated trolley beam and truss design, free-standing outdoor trolley rail systems became practical for the first time. Within a few years, trolley beam style fall protection systems became the most popular type of fixed installation rail car and trailer fall protection system in the U.S. Because of the ever-increasing popularity of trolley rail style systems, they have become surprisingly affordable and competitive with safety cables.
The most significant advantages of trolley rail style systems are obvious. Here is a partial checklist:

1. With trolley beams, there are no intermediate connections to get hung up on. A properly manufactured system has a smooth, level and virtually seamless trolley beam. Trolleys run end to end along the beam without hesitation.

2. An engineered trolley beam system can be built in any length and may be easily extended indefinitely (the largest manufacturer has installed several systems spanning over 1,000 feet long).

3. With the added stability of the built-in truss, these engineered systems require fewer vertical support columns so they take up less ground space and require less maintenance. The integrated truss design can span as much as 100 feet between support columns and may cantilever (extend) up to 30 feet beyond each end support. Since columns, and the concrete foundations supporting the columns, are the most expensive components in any fall protection system, longer spans between columns result in significantly reduced total cost. Imagine a 160-foot long trolley beam system with just two vertical support columns.

4. The greatest benefit of a trolley rail fall protection system is the high level of safety performance. Falls are arrested almost immediately, typically resulting in falls of less than two feet. Trolley beam systems, unlike flexible lifeline systems, do not allow bouncing secondary falls. With 12 years of experience and nearly 10,000 trolley beam systems installed, this author has never heard of a single injury to any user protected by these systems.

5. Trolley beam fall protection systems are capable of turning relatively sharp corners to follow irregular paths, such as curved railroad tracks or roads, with curved trolley beams custom made to meet the necessary contours required by an application.

6. Raising the height of a free-standing column supported system is no problem for a trolley beam system. Since the load is not being exerted against the side of a support column, as with cable systems, the system can be built to accommodate tall applications and to clear necessary obstructions. Freestanding safety cable systems are seldom built over 25 feet to minimize the torque load against the side of the columns.

7. The need for an annual cable tension adjustment is eliminated with a trolley beam system, and the stronger system design further eliminates the need for an annual professional inspection. With a well-engineered trolley beam system, you can eliminate $1,000 to $2,000 in inspection expenses. Simple self-inspection guidelines are readily available and maintenance personnel can generally make a thorough inspection in less than an hour.

8. When traversing high, dangerous and unstable surfaces, such as wind-blown trailers or railroad cars (especially those covered with something slippery, such as ice, snow, rainwater, grease, oils, hydraulic fluids, powdered or granular materials, sand, rocks or obstacles such as machine instrumentation), trolley beams provide a tremendous safety improvement over cables. The self-retracting, spring-loaded lifeline may be “locked” by the user with a simple tug and the user can walk while holding onto a firmly supported rolling lifeline to help maintain balance.
This is hardly possible with a cable system since a sharp tug on the lifeline results in little more than a dip of the cable. This feature provides additional work days to many outdoor loading operations where foul weather limits days when workers are allowed up on a protected surface.

Regardless of the type of fall arrest system selected, these systems are highly effective and have contributed significantly to worker safety. Remember--where people are working at heights above four feet, fall protection is required by law.

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