GE Security Industrial



Industrial Plant Operations: Big Cost Savings Lie in Smart Decisions Pertaining to Machine and Equipment Safety Systems Understanding the advantages of non-contact safety switches can mean the difference between continued success and potential financial catastrophe. By Geraldine Williams, GE Security Industrial In virtually every industry today, regardless of the economic climate, plant operators continually wrestle with bottom line issues. They do not need the added burden of unnecessary costs resulting from plant safety incidents. Unfortunately, operators of plant machinery and equipment routinely disable safety switches in an effort to keep production moving or to make their jobs easier. This practice is leading to more injuries and the costly disruption of production lines as well as entire plant operations. The severity of the problem is evident in numerous U.S. government data sources, including the Occupational Safety and Health Administration (OSHA), which cites the plastics products, sheet metal, fabricated structural metal industries and the users of industrial and commercial machinery—to name a few—as having the highest rate of injuries that result in amputation of workers’ limbs.(1) Not widely known is the fact that industrial safety switch technology exists today that will all but eliminate the possibility of over-riding or defeating machine and equipment guarding systems at the point of access. Plants which invest in machinery and equipment that incorporates this technology stand to save not only the considerable dollars that can be lost in halted production, but also the untold costs of medical treatment for injured workers. Then there are the costs of legal actions that can occur—not to mention the impact on productivity and workforce morale due to losing a valued worker. They’ll also avoid the potential of damage to their company’s reputation and the real prospect of the loss of future business.




Understanding Switch Technology Differences There are essentially two types of safety switches available today; these are classified as mechanical and non-contact. They are specified on an ever-growing array of industrial machines and equipment, including food processing blenders and grinders, metal fabricating and machining stations, printing presses, paper-making machines, and packaging equipment. They are also engineered into numerous commercial products, such as dishwashers and ice machines for restaurants and institutions. Typically, they are installed on guards such as enclosure doors, gates, grates and screens. Mechanical switches vary in type, but among the most commonly used are key operated versions (see Figure 1-FR692-D1). With these switches, opening a guard (such as a door or gate) on a running machine, the key is removed from the switch body, which opens the safety switch circuitry and subsequently shuts down the machine, thereby protecting the operator. However, inventive operators find ways to defeat these and other mechanical switches; often inserting an extra key, or removing the bolts from the key head and inserting it into the switch. This allows the guard to be opened for convenience purposes while the machine continues to operate. Unfortunately, it often exposes the person to injury from inadvertent contact with parts that are moving at high speed or operating at high temperature.		Figure 1: FR 692-D1

For these and other reasons, safety switch manufacturers have developed non-contact devices (see Figure 2- 301-BT GuardSwitch). They are smaller, easily hidden from view, and do not operate by mechanical action. A typical non-contact device is a two-part unit: the switch itself and an actuator. They are installed apart from each other—the switch on the machine and the actuator magnet on the guard. For the switch to operate, it must remain in proximity to the coded actuator, which contains a series of magnets. If an operator intentionally opens the guard while the machine is running, the actuator is moved away from the switch, which breaks its circuit and shuts down the machine. With early non-contact switch designs, it was possible to over-ride the switch by simply attaching a common magnet to the switch itself. Sentrol was the first manufacturer to solve this problem. Its patented design includes an “H” Factor, which is an area within the sensing range of the switch and the actuator. If a magnet is placed inside this area—or within 0.25 inches of the switch itself—for the purposes of defeat or over-ride, the switch activates and the machine is shut down. Machines also can be equipped with multiple switches that are wired in sequence along with a safety relay. The relay monitors the circuitry of all switches, and will automatically cause a machine shutdown if it detects tampering or a switch failure.
Figure 2: 301-BT	Major Factors, Cost Implications Despite their widespread availability, and the obvious advantages of non-contact switches, industrial equipment continues to be designed with mechanical switches. Plant managers, maintenance supervisors, risk managers, and employees themselves need to be aware of the implications of operating equipment with this less-than-effective technology. Following are five major factors to consider, along with examples of their specific impacts to a business. First, any machine in use today should be guarded by switches that adhere to the very latest safety directives and standards. The most stringent of these is the CE mark, which certifies that a piece of equipment is safe to operate in any plant in the United States and Europe. While the CE certification and other emerging standards are not yet mandated (except in Europe), plant managers can expect they soon will be, as governments and regulatory agencies worldwide continue to take steps to protect workers and lower the costs of workplace injuries.

A typical piece of capital equipment, (such as a commercial food blending system) has a purchase cost in the six-digit range. Its value to the business is measured in hundreds if not thousands of dollars per hour in finished product. A plant operating such a piece of equipment without CE certification could, in the near future, find itself in violation of local, regional, or national manufacturing regulations and be forced to take the equipment offline. The required re-engineering, recertification or even replacement costs could be as much as double the original purchase price, not to mention the staggering costs of stopped production and potential loss of future customer business.
A second consideration for plant managers is that their machinery be equipped with non-contact switch technology, which is, truly state-of-the-art. Specifically, switches that incorporate an “H” Factor feature, as described earlier, should also be based on a multiple-circuit design. This design requires the internal circuits to change state in the presence of the actuator before the switch output actuates, making it virtually impossible to over-ride (see Figure 3- “H” Factor Diagram). Aside from the effects of a switch over-ride, there are other important implications. Intentional switch defeat attempts or over-rides can, for example, cause a machine’s warranty to become void. As a result, repairs that would normally be covered by the manufacturer of a piece of equipment now become an unrecoverable cost to the plant, potentially in amounts ranging to many thousands of dollars. A third reality is worker injuries that result from switch over-rides must be reported to the Occupational Safety and Health Administration and can, in turn, result in a time-consuming plant inspection. If the plant is subsequently ordered to make changes to prevent the over-ride situations and fails to do so, it faces penalties ranging from $7,000 to $25,000. Employers who repeatedly fail to make OSHA-mandated changes can face penalties of $70,000 for each violation.(2) Fourth is the importance of weighing the physical aspects of safety switches that are specified on the plant’s equipment. Non-contact devices are inherently reliable because they have no moving parts that can break down. But, when comparing the offerings of various non-contact switch manufacturers, it’s particularly important to take environmental factors into consideration as well. As an example, a major soft drink producer’s equipment included switches housed in polycarbonate and/or thermoplastic material that was found to fail when the equipment was washed with alkaline detergents. These switches had to be replaced at considerable cost. Fortunately, switches are available today with stainless steel and Kynar housings that will stand up to the harshest wash down and other environmental conditions. The savings to an individual plant can be substantial; to a multi-plant enterprise, they can be enormous.		Figure 3: The "H" Factor

Fifth and Last, do not overlook the installation and maintenance cost issues of switches to be selected. Non-contact switches—unlike mechanical devices—do not present a hazard themselves since they do not have protruding keys that can catch on clothing or injure an eye. Several manufacturers offer non-contact switches today that measure no more than 1L x 2W x 1H inches. In equipment retrofit situations, this is important because they can quickly be installed and easily concealed in a variety of locations without the need for specialized brackets or mounting assemblies. This, combined with the fact that non-contact switches require no internal terminal connections, and no alignment and/or re-alignment, as most mechanical switches do, promises labor savings that can lower the cost of goods sold in any plant today. (1) Occupation Safety and Health Administration, Directive CPL 2-1.33, National Emphasis Program on Amputations (2) Occupation Safety and Health Administration, Inspection Reference Manual CPL 2.103, Section 8- chapter IV, Post Inspection Procedures About the Author Geraldine Williams is a 15-year employee of GE Security Industrial. She holds a Bachelor of Science degree in Electrical Engineering and an MBA, and is a member of two engineering honor societies. Williams is also affiliated with the Association of High Technology Distribution, the American Management Association and the American Marketing Association.