Reach for Machine Safety
How do you put a price on life and limb? Faster machinery, if well integrated, has potential to make more money. Downtime or lost time from machine-induced injury represents personal and financial loss for any operation. In the U.S. alone, 800 deaths and 18,000 amputations, lacerations, crushing injuries, and abrasions are attributed to machine-related incidents a year, according to U.
Mark T. Hoske
How do you put a price on life and limb? Faster machinery, if well integrated, has potential to make more money. Downtime or lost time from machine-induced injury represents personal and financial loss for any operation. In the U.S. alone, 800 deaths and 18,000 amputations, lacerations, crushing injuries, and abrasions are attributed to machine-related incidents a year, according to U.S. Department of Labor, Occupational Safety & Health Administration (OSHA) statistics.
Laws, regulations, and guidelines provide protection. Training, procedures, and personal responsibility can reduce risk and financial, civil, and even criminal liability. Good designs help as well. In general, machinery-related hazards can be enclosed, passively or actively locked out, or intrusion can be sensed and the process stopped in time to avoid injury.
World of regulation
Safety standards can be electrical; application or product-related; and include design and operation of safety component devices. Organizations and processes for establishing rules and guidelines vary globally to help avoid a world of hurt. (See map for a sampling.) In addition, more than a dozen governing organizations have created relevant regulations.
Automation suppliers can explain standards, point to how some important parts relate to other standards, and ask customers to read them, says Dave Collins, in the machine safeguarding products area for Schneider Electric, "but in the end, we cannot tell people what they should do."
Collins does lend a hand from time to time, or at least, some fingers. In one instance, "I was looking at a piece of equipment that had one place guarded. I touched another area nearby, knowing I would have torched my fingers had it been operating, and the machine builder said, 'Hey, you're not supposed to touch that .' Obviously they had overlooked something," Collins says.
Before these new standards evolved, every machine had to be considered very dangerous at worst case, recalls Art Pietrzyk, safety program manager, Rockwell Automation. Now risk assessments are performed to determine the safety integrity level (SIL) that must be achieved to reduce that risk. Also, Pietrzyk suggests, customers can now use SIL standards to compare automation vendors' offerings. For example, customers can look at quantitative measures, such as mean time between failure and probability of failure on demand, and qualitative measures, including diagnostic coverage or fail-safe design. Rockwell Automation has IEC 61508 TÜV-certified controllers: ControLogix controllers at SIL 2, and GuardPLC at SIL 3. Safety level and related security requirements impact the type of controls used.
"It is the customers' responsibility to establish the safety need and apply the safety components to satisfy this need," maintains Mike Frey, Omron Electronics safety products manager. A risk-assessment process helps ensure a safety-compliant work environment, he says, to avoid accidents. "To quantify Workman Compensation payments, a finger is 40 weeks, a thumb 70 weeks, a hand 190 weeks, and an arm, 235 weeks of wages. For an $18 per hour salary, at two-thirds pay rate (as required in Illinois, for example), an arm would cost $113,000." Add to that, health-care costs, fines and/or litigation, as well as less quantifiable, but real, costs of human suffering, declines in morale and productivity. "That tends to get peoples' attention," Frey says.
The map shows a sampling of more thatn a dozen groups related to machine safety, including information from Idec.
Hungry for guidance? A four-bullet regulatory sampling follows, summarized from "Safety Product Guidebook," from Omron Electronics.
OSHA requires that employers and OEMs comply with Part 1910 of the 29thCode of Federal Regulations (CFR). OSHA recognizes standards made by voluntary consensus, such as those developed by American National Standards Institute (ANSI). Organizations apply to the ANSI Board of Standards Review. Organizations that have submitted and have had standards approved and registered include American Society of Mechanical Engineers, Robotic Industries Association, National Fire Protection Agency, and Association for Manufacturing Technology.
Even with all those efforts, some technologies, such as light curtains, are not covered directly under U.S. rules, so guidance must be sought from other groups. These include regulations from the European Economic Union (EU), called European Standards (EN Standards), and others based in Europe, such as the International Electrotechnical Commission (IEC), and the International Organization for Standardization (ISO).
EU rules include the "Machinery Directive," which governs new machinery sold in Europe, adopted in 1995, and safety components in 1997. Preventive measures, such as risk analysis, accident prevention training, and priority of protection are covered under the "Use of Work Equipment by Workers at Work Directive," starting in 1997, for new and existing machines. The EU also requires European standards bodies CEN and CENELEC to produce harmonized standards for the EU. Three groups are Type A Basic Safety Standards, Type B Group Safety Standards, and Type C Individual Safety Standards.
Specific countries and other governing bodies also can influence machine safety. These include Canadian provinces, the Canadian Standards Association, and Japan Industrial Standards, which were revised according to terms of the World Trade Organization to align more closely with IEC and ISO standards.
Costs, type, design in safety
Costs of compliance vary by technology, strategy and application. Laws and regulations vary widely depending on application, region, and myriad other factors. Methods and technologies can include enclosures, cages, guards, alarms, light curtains, area scanners, two-hand controls, safety mats, safety relays, interlocks and switches, and e-stop pushbuttons, among other items. Designs themselves can help preserve fingers and other limbs by considering pitch points—areas that could, even in unusual circumstances, put the squeeze on appendages.
In Europe, tendency has been to mandate requirements upfront. U.S. practices tend toward stating regulations, then enforcing through fines and back-end penalties. And rules are never static. For instance, new opportunities confront U.S. original equipment manufacturers because NFPA79 allows safety components to be incorporated into the control network. In an example of what that can mean, Siemens Energy & Automation customer Pearson Packaging Systems spent 368 hours to hardwire one machine, switched to using AS-i network and reduced the time to 96 hours. With the same resources, they're able to produce and sell two more machines a year.
Fortunately for end-users and OEMs, manufacturers of the safety-related technologies offer help with Web sites, experts on staff, and training that incorporates safety.
Good product design starts with safety in mind. Among thousands of possible examples across industries, the Mazak VTC-300C vertical machining center uses a fixed table and traveling column, which helps reduce operator fatigue and allows convenient accessibility for easy (and safer) part exchange. A movable CNC operation panel puts it within easy reach. Interlocks ensure parts are enclosed before machining begins. Engineers and project managers at Mazak USA in Florence, KY, regularly help customers safely design, build, and install machines; nine regional training centers help teach customers about safe operations.
As regulations change, many OEMs remain sensitive to helping customers sort through what's appropriate and what's most economical to change in already-installed equipment to match upgraded standards.
Milacron Inc. Plastics Technologies Group in Batavia, OH, documents how to update its horizontal injection molding machines to meet Clause 6 requirements of ANSI/SPI B151.1 standard. Milacron offers upgrades in several areas to help customers comply, but guarding—while required by the Society of the Plastics Industry—can be done faster and at significantly lower cost by the end-user or a local contractor, advises Milacron.
Another area of safety means guaranteeing that the machine doesn't do harm if a component fails. IEC 61508, for instance, says there should be redundancy in all safety-related electronics to allow safe failure when a wire or component fails. That can depend on system design and not just on reliable components. The four functional safety areas of IEC 61508 are of major interest today, according to Richard Galera, a Rockwell Automation manager for safety controls. But in the end, "It's up to the customer to analyze the application, designate the category, and decide what technology to apply," Galera says.
Products for machine safety vary significantly in type and style and by manufacturer. A sampling of more than a dozen safety-related products appears with this article online.
November Cover Story Online Extra
- Organizations influence machine safety
- Safety-related reading from Control Engineering
- Light curtain types differ in protection
- Cleaning up integration: more on light-curtain use at Ransohoff
- Exclusive:‘I’d like some help with those safety products, please’
- Products help with machine safety
Organizations influence machine safety
The following organizations are among many that influence machine safety in various industries. In the U.S., a number of organizations are safety-interdependent in a number of ways, as the graphic shows
While global standards can be viewed as one more step and expense in product development, others suggest they help with global health, safety, and trade. On Oct. 14, World Standards Day, leaders of IEC, ISO, and ITU issued a joint statement, suggesting, in part, that wider participation in international standards-making efforts helps “lower costs, broaden the choice of partners and suppliers, create products with worldwide market coverage and acceptance, and expand export opportunities by reducing technical barriers to trade.”
AMT Association for Manufacturing Technology
ANSI American National Standards Institute
ASME American Society of Mechanical Engineers
CCC China Compulsory Certification (CCC) Mark
CEN European Committee for Standardization
CENELEC European Committee for Electrotechnical Standardization
CSA Canadian Standards Association; CSA Internationa l
DIN Deutsches Institut fur Normung
EU European Economic Union (EN Standards)
FDA U.S. Food and Drug Administration
IEC International Electrotechnical Commission
IEEE Institute of Electrical and Electronics Engineers
ISA Instrumentation, Systems & Automation Society
ISO International Organization for Standardization
ITU International Telecommunication Union
JIS Japan Industrial Standards
NFPA National Fire Protection Association (National Electrical Code, NEC)
OSHA Occupational Safety & Health Administration (U.S. Department of Labor)
RIA Robotic Industries Association
SPI Society of the Plastics Industry
Regulations change regularly; certification agencies can help with updates. For instance, according to Underwriters Laboratories (UL ), the China Compulsory Certification (CCC) Mark is required before products can be offered for sale in China. In August, China passed a new mandatory safety certification requirement, the Compulsory Product Certification System (CPCS) to unify existing Marks being given for products—Conformity Certification of Electrical Equipment (CCEE) Mark and the China Commodity Inspection Bureau (CCIB) Mark, to conform to the World Trade Organization's Agreement on Technical Barriers to Trade, UL says.
For additional agencies and organizations with information about or helping with various certifications, see the map in the main article and links below.
BG-PRÜFZERT German certification agency
CE Mark for European Union Product Directives, EU
C-tick Australian Communications Authority (ACA) EMC protection
Demko (UL subsidiary; D-Mark)
Denan [Dentori (E)] - The Japan Ministry of Economy, Trade and Industry (METI) administers the Electrical Appliance and Material Safety Law (DENAN)
Lloyd’s Registe r
SGS (Societe Generale de Surveillance) Group
Underwriters Laboratories Inc.
VDE Association for Electrical, Electronic & Information Technologies
An expanded version of “Division or zone” click here
Light curtain types differ in protection
So you’ve read the regulations, done a risk assessment, considered if other safety equipment might be appropriate (safety mats, safety switches, hard guards, or some combination), and think that light curtains are the most appropriate answer.
After reviewing appropriate regulatory documents, such as ANSI B11.TR3, ANSI/RIA R15.06-1999, and/or EN1050, keep in mind that light curtains’ protection level varies between Type 2 or Type 4, advises Sergio Aguilar, product manager, Scientific Technologies Inc. Further, Type 2 devices are not intended for use where ANSI B11.19, OSHA 1910.212 or 217 apply, and should never be used on a mechanical power press, Aguilar warns; Type 2 devices must not be used where regulations require the use of Control Reliable circuitry.
Major differences, Aguilar says, are:
Fault detection circuits. Type 2 light curtains do not meet the OSHA or ANSI standard for Control Reliability. Type 4 safety light curtains do.
Optical angle. Type 4 safety light curtains provide an effective optical angle of
Price. Type 2 devices typically cost 15-30% less than an equivalent Type 4 device. The lower cost results from less sophisticated fault detection circuitry, a less precise optical angle, and significantly fewer features.
Safety strategy, risk assessment, and formal procedure documentation are available by clicking here .
Cleaning up integration: more on light-curtain use at Ransohoff
Ransohoff Inc. Lean-Jet Series of aqueous cleaning systems integrates MiniSafe MS4600 Series safety light curtains from Scientific Technologies Inc. with Lean-Jet’s primary control system.
Incorporating the safety light curtain into the machine’s control system in a “point-of-operation” configuration, the operator places parts in and removes them from the machine, intentionally breaking the sensing beams of the light curtain.
The light curtain has control-reliable circuitry for self-monitoring functionality. It also monitors the Lean-Jet’s primary control elements as part of its automatic diagnostic procedure to ensure safe operation. Integrating the light curtain’s built-in processor, with the Lean-Jet’s closed-loop control system, simplifying operator interaction and increasing operator efficiency. The MS4600 safety light curtain controller is located inside the receiver housing. Not having an external controller saves internal space.
Using a light curtain simplifies logistics. Without the MS4600 safety light curtain from STI integrated into the Lean-Jet’s closed-loop control system, the operator would need to actuate a manual switch to open and close the machine’s power circuit to safely load and remove parts. This approach exposes the operator to risk of potential injury if the machine is still operating. Additional time and motion required to operate the switch also increases cycle time and worker stress, thus reducing throughput and overall productivity.
Knowing how a machine works is part of understanding the safety strategy that should go with it. Lean-Jet Series uses high-impact water sprays for washing and rinsing, and an energy-efficient, high-velocity heated air blower to dry the parts. The caster-mounted 304 stainless-steel clad system is designed for easy installation and features a smaller footprint than previous parts washers (3 ft wide by 5 ft-5 in. deep).
The system configuration uses a common loading and unloading station, enabling operators to handle heavy parts with dimensions of 12-in. high by 12 in. diameter. Up to 120 cycles per hour contributes to improved throughput. Another factor in increasing production throughput is Lean-Jet’s ability to allow fast work cell configuration for small-lot continuous-flow production, as well as off-line cleaning and servicing.
Internal design of the Lean-Jet Series eliminates work passage openings and prevents cross contamination between the washing, rinsing and drying areas. Combined with the enclosed self-ventilating system, these features also make the environment much more worker-friendly by eliminating vapors and mists associated with other parts washing systems.
Continuous operation is automated, using rotary-pocketed wheels, a key design element created and patented by Ransohoff. These wheels rotate parts in a motion independent of the part washer’s rotary transportation table. This allows surrounding sprays to have full access to any part placed in the Lean-Jet system. Combined with highimpact spray jets, the system provides consistent, thorough cleaning on each side of the part.
In addition to its compact design, Lean-Jet can run continuous cycles resulting from use of automated control and safety equipment. A PLC stores up to three user-customized part cleaning batch programs, which include sequence times and temperatures for each step of the operation. Once the program is initiated, it runs automatically without further operator intervention. A touchscreen allows operators to select the stored program for operation, starting or stopping the machine and to query the system for diagnostic messages.
For more info from Ransohoff, click here .
For more info from STI, click here .
Exclusive:‘I’d like some help with those safety products, please’
It’s almost as easy as super-sizing your fries—Automation Value Card for services and training is now available to simplify and enhance how organizations and individuals get help from Siemens Energy & Automation. The point-card system includes assistance with implementing safety initiatives. And, to better address customer needs, Siemens formed a safety-related services group, announced first in the November 2003 edition of Control Engineering.
In part because NFPA79 allows incorporation of safety components into the control network and because of other safety requirements, safety-related automation is considered a growth area—where several automation vendors have bolstered their offerings in recent years. Previously, controls and safety systems were separate, and safety systems were always hardwired. Educating customers about resulting benefits of integration remains a challenge for automation vendors. Formation of a dedicated Siemens safety group and the Automation Value Card initiative improve safety-related help and education.
Members of Siemens E&A team participated in a roundtable interview earlier this year with Control Engineering to discuss the company’s safety initiatives and related trends, including anticipated announcement of the safety center.
Filomena Wardzel, manager of the Siemens automation business, suggests that U.S.-based applications haven’t been as proactive with integrating the latest safety technologies and initiatives as European manufacturers. Ability to unite safety and controls—says Brian Libby, product manager for Siemens AS-Interface, Siguard safety products—increases operator awareness, and simplifies the system by tying in e-stop via a safety bus to the programmable logic controller and human-machine interface.
Safety needs to be considered from the beginning. J.B. Titus, Siemens Safety Integrated manager, says, “Taking safety into consideration during the design stage decreases costs over the equipment’s lifecycle. The size of the control panel can shrink, while wiring, startup, commissioning, and upgrades are easier. For instance, when a system is hardwired and causes intermittent tripping, there’s no record formed. When it’s all networked, every incident has a time stamp, allowing faster resolution of any problem.”
Simplifying communications, Siemens uses ASi-Safe and ProfiSafe for safety applications, an economical, existing solution, says Christian Kurtz, business development, Safety Integrated. “Direct diagnosis is available and only one bus is needed from sensors through safety block I/O devices to PLC to HMI,” he says. Titus adds that the safety networks are certified to work with a mixture of suppliers’ offerings.
Separate or integrated
Wardzel notes, “A separate safety network can be used within the machine or it can be integrated with the control network.” For instance, Pearson Packaging Systems (Spokane, WA www.pearsonpkg.com), as mentioned in the main article, wired one machine in less than one-third of the time. Libby, a NFPA79 committee member, says performance on a safety network, according to NFPA79-02, needs to meet or exceed that of hardwiring. (Another standard in the forefront is IEC 61508, which says there should be redundancy in all safety-related electronics and that it should fail safe, if a wire or component fails. Kurtz notes that failing safely is different from redundancy, which allows continued operation. Redundancy also can be designed into a system, but at higher cost.)
Another option, says Wardzel, is to apply AS-i bus within a machine and Profisafe for connecting the full automation line. Beyond installation savings from using a sensor-level network, operators will realize benefits from uniting two previously separate sets of information. That integration, Wardzel says, allows “immediate display of diagnostic information to aid troubleshooting and get to the root cause faster to stretch mean time between repair and mean time between failure.” Predicting when maintenance is needed reduces downtime, which, depending on industry and application, Libby says, can run from $10,000 to $1 million per hour.
Other costs also can help justify the expense, Titus suggests. “Establishing a plant-safety program, increasing plant safety importance, and safety visibility at all levels in the organization can help reduce payments to state bureaus of worker compensation. Siemens has identified engineering firms and system integrators who can help with risk analysis. “Customers with discrete applications aren’t used to having to do a risk analysis as compared to process applications, but the analysis is similar in many ways,” Titus says.
With rapid growth in safety initiatives expected, Wardzel says, some OEMs will save money by changing equipment designs consistent with the safety needs of multiple industries they serve.
For application engineering services, from January through September 2003, Siemens has piloted and refined the Automation Value Card system for services. “It’s a cost-effective way to offer support after a sale, and helps track customer history, needs, and requirements. Training classes are included as products on the card,” Wardzel adds.
July 1 marked the internal beginning of the safety organization. Siemens safety products are TÜV certified and UL listed. Products include safety PLCs, bus systems, motor starters, drives, motion control, and relays, among others.
— Mark T. Hoske , Control Engineering, editor in chief
Products help with machine safety
A diversity of products help with machine safety. These include emergency-stops, hardguards (such as gates and fences), interlock and enabling switches, non-contact safety interlock switches, perimeter access guarding device, safe power distribution devices, safety interlock switches, safety laser scanners, safety light curtains, safety limit switches, safety monitoring relays, and safety programmable logic controllers (PLCs), among others.
Click here to read a safety product sampler, part of the November 2003 Control Engineering Discrete Control e-mailed newsletter.
To sign up for Control Engineering e-newsletters, click here .
Exclusive: Siemens forms safety integrated technology group
Siemens Energy & Automation formed the center for Safety Integrated Technology to help customers meet changing industry standards and address increased demands for safety. The company is announcing the initiative exclusively in this November 2003 North American edition of Control Engineering . Initial markets include automotive, food and beverage, consumer products, material handling, packaging, and metal forming. The Norcross, GA-based initiative aims to improve safety-integrated technologies and services for U.S. manufacturers.
J.B. Titus, who leads the U.S. effort as Siemens Safety Integrated manager, says this strategic initiative is heavily networked with Siemens divisions and businesses in Germany, Canada, and Mexico. Titus says, "Engineers and decision-makers are taking advantage of savings, enhanced productivity, and greater efficiency and uptime as a result of our new certified safety technologies, which are an integral part of Totally Integrated Automation from Siemens. It is now easier to engineer, implement and maintain safety in any plant." Siemens bus (industrial network) designs, diagnostics and programmability from Europe are now available through Siemens' U.S. sales professionals, business developers, and application engineers, he explains.
"Cost savings come from less downtime and because technicians are no longer required to pull wire and do point-to-point checkouts," Titus explains. "They can install e-stops on a cable and take advantage of built-in diagnostics that come as part of the bus technology." Titus claims that Siemens has the only certified and listed failsafe automation solutions applicable worldwide.
Exclusive: Safety light curtains speed part loading; increase machine throughput 10%
Light curtains often are used to stop operations upon breaking the beams. Ransohoff Inc.—a manufacturer of aqueous parts cleaning systems for more than 85 years—is using light curtains to start things, as well.
Looking to increase user productivity for washing and cleaning fabricated parts, the Cincinnati, OH-based company developed the Lean-Jet Series of aqueous cleaning systems. The new design significantly improves workflow and contributes to reduced work-in-process inventory and associated warehousing material costs.
Part of the benefits were realized by integrating MiniSafe MS4600 Series safety light curtains from Scientific Technologies Inc. with the Lean-Jet's primary control system. The safety light curtain acts as a safety device and presence sensor, reducing the number of sequential steps required by the machine operator. By simplifying operations and signaling the system to begin its cycle based on its sensing state and inputs, the safety light curtain allows up to 10 additional machine cycles per hour (representing a 10% throughput increase over previous systems without safety light curtains).
An operator can safely feed parts into the machine between each operating cycle due to the protection provided by the safety light curtain. This is accomplished by incorporating the light curtain into a Presence Sensing Device Initiation (PSDI) control scheme. In this mode, the control system allows an operator to place a part in the Lean-Jet system and then back away. When the light curtain senses no beams are blocked, the machine automatically cycles after a preset time.
Using PSDI eliminates the time required of the operator to actuate a start/stop operation switch. In some cases, Lean-Jet users have realized parts loading and cycle initiation savings as high as 50%. Additionally, this mode of operation can reduce repetitive motion and stress levels for machine operators.
Russ Wood is application engineering manager with Scientific Technologies Inc., Fremont, CA
Don't lose your head over safety
There's always something to learn on a plant tour, including how not to lose your head over safety.
The tour guide had just finished warning a group not to get too close to a cell of small-part, pick-and-place robotics. As if on cue, someone poked his head into the safety light curtain for a closer look at the process, providing a perfect demonstration of how a cell shuts down to prevent machine-induced mayhem. The operator seemed a little miffed at having to reset the line, and the perpetrator looked embarrassed, but the rest of the group seemed to enjoy seeing how a light curtain helped avoid injury.