When is "safe" safe? The value of a risk assessment
By Rick Carpenter
In late August, Hurricane Isaac drove water over the top of a levee on the outskirts of New Orleans, triggering life-threatening flooding seven years to the day after Hurricane Katrina.
Emergency management officials in low-lying areas reported the overtopping of this 8- or 9-foot high levee of southeast New Orleans. About 2,000 residents of the area had been ordered to evacuate, but only about half were confirmed to have gotten out before Isaac brought driving winds and rain.
Not only did Isaac deliver more of a punch than people thought possible, it was the first test for multibillion-dollar flood defenses built after levees failed under Katrina's storm surge, leaving large parts of New Orleans swamped, killing 1,800 people, and costing an estimated $81 billion, the costliest natural disaster in U.S. history.
Natural levees serve as barriers by confining rivers during periods of ordinary flow. They may even protect low-lying areas from flooding if the level of a river is not too high. For this reason, artificial levees designed to contain a river during flood stages are often built, but these artificial levees can themselves create problems by confining the river to a narrow channel, or confining sediment, which in turn raises the river bed higher and higher. These same levees can provide a false sense of security as we just witnessed with Hurricane Isaac.
Safety measures do not obviate risk
Functional safety standards exist to ensure the safety of processes and to help prevent accidents from happening on the industrial plant floor. These standards provide a formulized method to determine the risk associated with industrial machinery. Functional safety standards also provide guidelines to prevent unsafe conditions and components. Both OSHA and ANSI are important agencies in North America. They provide guidelines on how machinery can operate safely in order to prevent a dangerous situation. However, neither organization creates standards on how or when a safety component is considered safe. Both OSHA and ANSI rely on standards, such as ISO/EN 13849 and IEC 62061, to define what makes safety devices safe, as well as how the safety devices should be used on machinery in order to achieve a safe state of operation.
Too often, many manufacturing facilities believe that they are safe simply because there is already some sort of safety device or devices in place, and no one has been hurt on the existing equipment. However, the question needs to be asked again, when is "safe" safe?
How can you evaluate existing machinery already in place? Does the machinery already provide proper functional safety? And does the equipment meet with current safety standards so as to comply with adopted OSHA and/or ANSI standards? The wrong approach is to simply ignore these issues and hope nothing will ever happen. The correct approach is to conduct a functional safety risk analysis and see where any safety issues may be.
Assess likelihood and severity
Risk is, by definition, the chance or likelihood that someone or something could be harmed or damaged by the hazard, together with an indication of how serious the harm or damage could be. It is usually a combination of the likelihood of occurrence and the consequences: How likely is this to happen? How serious could it be? Risk is usually expressed as high, moderate, or low (qualitative), or as a number, with the higher number indicating the greater the risk (quantitative).
Risk assessment is the process of identifying hazards related to environment, health, and safety that are intrinsic properties of work-related activities, assessing both the likelihood that the hazard will lead to a loss and the severity of that potential loss. The results of likelihood and severity are combined according to an agreed-upon rule to give a single measure of potential risk.
Simply put, a risk assessment is a careful examination of what, in your workplace, could cause harm or damage to people, property, or the environment. You can then decide if you have taken enough precautions or should do more to prevent any harm or damage from happening.
ABOUT THE AUTHOR
Rick Carpenter (firstname.lastname@example.org) is functional safety and life sciences manager at Loman Control Systems, Inc., a Control System Integrator Association (CSIA) Certified member based in Lititz, Penn. To learn more about CSIA, visit the association's web site at www.controlsys.org.