According to Safety and Health Information Bulletin 09-29-2008, the Occupational Safety and Health Administration (OSHA), between 2000 and 2006, investigated a number of rollover accidents involving ride-on compactors.
In 19 accidents, machines were equipped with a ROPS (Roll-Over Protection Structure), but operators were not wearing seat belts. Fourteen fatalities resulted—many of which occurred, says the report, when the operator was ejected or jumped from the machine and was pinned under the ROPS. Seven accidents involved machines without a ROPS and run by operators not wearing a seat belt. Seven fatalities. Five accidents involved machines fitted with a ROPS and operated by workers wearing seatbelts. No fatalities.
The report draws a fundamental conclusion: “If the machines involved in these accidents had been ROPS-equipped, and if the operators had been wearing seat belts, the likelihood of the operator’s survival would have increased significantly.”
The report does not explain the lack of a ROPS on some machines—except to say that in one instance the structure was removed “as a convenience” and not replaced. Although OSHA does not mandate a ROPS and seat belt for ride-on compaction equipment, the industry has long installed these items to satisfy standards established by SAE (Society of Automotive Engineers), ISO (International Standards Organization), and OSHA’s General Duty Clause, which obligates employers to provide a place of employment free from “recognized hazards” likely to cause harm.
BOMAG, for example, says Bert Erdmann, director of engineering/product manager for heavy compaction, has been installing a ROPS and seat belt—and in some instances, a FOPS (Falling Objects Protection Structure)—for more than three decades.
In the interest of safety, perhaps these are the takeaways from the OSHA study: 1) Dig in your heels if ever asked to run a roller that, for whatever reason, does not have a ROPS and seat belt; 2) Wear the seat belt; the ROPS is effective only if the operator remains buckled in; conversely, the ROPS actually can be a liability if you’re not strapped in.
More roller cautions
According to OSHA, rollover accidents involving ride-on compactors are most likely to occur near the edge of a slope, such as a ditch that falls away from the side of a road. A manual for Dynapac single-drum soil compactors advises that a minimum of two-thirds the drum’s width remain on a flat, solid surface when operating near the edge of a slope.
The manual also reminds operators that a roller’s center of gravity moves outward when the machine articulates. If the roller is operating near the edge of a slope on its right side, then steering to the left in order to move away from the slope will momentarily shift the machine’s center of gravity to the right—toward the slope.
Manufacturers agree that compacting slopes is best done operating the machine up and down the face—not across the face. If the roller must traverse across a slope, the manufacturer might stipulate a maximum angle (or slope percentage) that shouldn’t be exceeded. Remember, however, that the angle likely is based on a stationary machine positioned on a solid surface; a moving machine, with its vibratory system active and perhaps being steered across loose material, might tip at a lesser angle.
For single-drum soil compactors with large drive wheels at the rear, maintaining proper air pressure in the tires is critical. Unequally inflated tires serve to destabilize the machine, a condition that might be magnified when the machine is operating at an angle.