CoatingsPro Magazine

MAY 2017

CoatingsPro offers an in-depth look at coatings based on case studies, successful business operation, new products, industry news, and the safe and profitable use of coatings and equipment.

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Page 33 of 84

COATINGSPRO MAY 2017 33 WORK IT SAFE Although the proportion of workers who smoke tobacco or who are exposed to secondhand smoke in the workplace has declined over the past several decades, many workers remain susceptible to the harms of tobacco smoking. The percentage of workers who smoke cigarettes varies by industry and occupation. According to the American Medical Association, the highest percentages of workers who smoke are in mining (30 percent), accommodation and food services (30 percent), and construction (29.7 percent) industries. Similarly, smokeless tobacco use is relatively frequent among workers in the mining (18.8 percent), wholesale trade (8.9 percent), and construction (7.9 percent) industries, according to the Morbidity and Mortality Weekly Report. The use of emerging tobacco products, including hookah and electronic nicotine delivery systems (ENDS) or e-cigarettes, has increased in recent years. Despite the increased use of e-cigarettes and the market- ing of these products, little is known about long-term health effects. According to the Morbidity and Mortality Weekly Report, an estimated 5.5 million working adults were current e-cigarette users in 2014. Many states have laws to prohibit smoking and tobacco use in the workplace. Employers can also enact policies that restrict smoking and tobacco use in the workplace. National Institute for Occupational Safety and Health (NIOSH) provides recommendations and resources that protect workers from the hazards of using tobacco, that help employers prevent workplace exposures to secondhand smoke, and that promote the overall well-being of workers. For more information, contact: NIOSH, of its connecting parts. As engineers, we have to design to those safety requirements for the reasons we have just discussed; however, it is not good practice to rely on this buffer, think- ing all is well with a little increased tensioning. Over time, with recycled pieces and parts (particularly cables), materials become compromised and are reduced in capacity. Abrasion, corrosion, wear, fatigue (loading and unloading cycles), shock-loading, and crushing all compromise the cable's integrity, reducing that nice, big OSHA factor of safety down to not-so-big numbers. Combine all of that with cable over-tensioning and debris that can and often does exceed design loads due to less-than-ideal vacuuming efforts, and one has the recipe for a potential catastrophic failure. How It Happens Cable failure is not pretty. Failure is often sudden without much, if any, warning. At failure, all of the built-up tensile force in the cable releases violently, causing the cable to whip around in all directions uncontrollably. Not only will there be failure of the platform surface at the failed cable, but adjacent hangers or nearby workers may be struck by the cable in motion, potentially resulting in a domino effect of adjacent platform failure and wide-spread containment failure. Contamination of the jobsite is likely. Above all that, though, is the potential for severe injury or death. Not only is a cable failure a concern, but there is also a great risk of failure of the cable tie-off. Many states allow cables to be tied off to plates anchored into existing concrete piers or abutments. A lthough the connec- tion plates and drilled anchors are designed for the same factor of safety requirements as that of the cables, neither the condition of the concrete nor the quality of the installation of the anchors is a sure thing. Any variation from design parameters of concrete strength, drilled hole diameter, instal- lation procedures regarding cleaning of the drilled hole prior to placement of the anchor, and anchor embedment lengths alters the capacity of the tie-off plate and, ultimately, the capacity of the cable system. Failure of the cable system, and all its resultant destruction, could just as easily be from excessive forces pulling the tie-off plate anchors out of the concrete as it could be from failure of the cable itself. Ideally, when using anchor plates, the attachment should be to the top of the pier or abutment instead of to the side. is helps to limit the tension or pull-out forces on the anchors. Don't Deflect Let's look deeper at the impact the variables' load, span, and deflection have on cable forces. On occasion, platform systems require strict deflection limitations, such as when installed over a railroad, low clearance roadway, or waterway. e question then becomes, "W hat is the best way to successfully achieve the smaller deflec- tions without overloading the cable system?" With allowable tensions regulated by OSHA, and deflections determined by rail, road, or water clearance require- ments, only two variables remain in the equation: load (W) and span (S). It is logical that reducing load and/or span will decrease cable forces, but we need to look to the equations to see that reducing one is more beneficial Safety Watch

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