Machine & Operator Safety
Designer machines: Five principles of designing a safer, sustainable machine
November 12, 2010 by Steve Ludwig
Manufacturers across many industries are placing increased emphasis on machine designs that support safety and sustainability initiatives, and drive economic prosperity.
Machines that improve safety, minimize waste, consume less energy and deliver maximum return on investment are critical to the success of any sustainable production program. Building such a machine requires a holistic approach to analysing operational efficiency, safety, functionality, productivity, ease of operation and maintenance.
By following these five best-practice design principles, machine builders can deliver safer, more cost-effective and sustainable machines.
1. Perform a safety audit after mechanical design, but before control system design: Performing a safety audit before control system design helps engineers chart the course for an effective safety solution, and evaluate and investigate risks early in the development process. This saves critical time and helps machine builders get their equipment to market faster. In addition, the machine’s end users gain optimized production, thanks to an automation system that helps operate machinery and processes in the most efficient way. A safety audit identifies the required safety control system integrity level and helps guide the selection of the overall control architecture to achieve the optimum level of safety.
2. Guard or control access to moving parts: Where hazards cannot be removed through design, machine builders typically will install a fixed physical barrier that protects users from the hazard. When frequent access to the hazardous area is required, non-fixed guards are used, such as removable, swinging or sliding doors. In areas where non-fixed guards are impractical, guarding solutions that monitor the presence of the operator rather than the status of the gate can be used.
While relays and other devices prove effective, many safety applications require a level of programming or more sophisticated safety logic that is best met through a safety controller. Safety controllers offer significant benefits in multistep shutdown or ramp-down sequences, such as transfer line applications, because they provide the necessary logic through software rather than the hard-wired logic of relays. An integrated safety controller is an ideal solution for any application requiring advanced functionality, such as zone control.
With properly designed safety controls and guarding, designers reduce access
time and help to make machines safer and more efficient.
3. Use integrated safety systems to reduce control system complexity: The more designers integrate the standard and safety control functions of a system, the better the opportunity is to reduce equipment redundancies and improve productivity and economic factors. This integrated control functionality reduces the number of unique components in use on the factory floor, which in turn reduces crib inventory costs, as well as maintenance team training requirements. End users also benefit from less waste with fewer parts to maintain and replace throughout the machine life cycle. In addition, integrated control systems have broader intelligence regarding machine operation and status, and reduce nuisance shutdowns and prolonged restarts, further improving machine efficiency and productivity.
New safe-speed control solutions provide a great example of effective control integration. With safe-speed control, safety input devices, such as guard-locking switches, light curtains and emergency stops, connect directly to the speed-monitoring core of the control solution. This eliminates the need for a separate, dedicated safety controller. Providing use across multiple platforms, safe-speed control solutions help reduce overall system cost and improve flexibility because they allow operators to perform maintenance and other tasks while a machine is in motion. Safe-speed control also helps increase uptime and decrease energy costs because a machine does not need to be completely shut down and restarted.
Networking offers another way to integrate safety and standard controls. The introduction of networks to the plant floor brought many benefits to manufacturers, including increased productivity, reduced wiring and installation, improved diagnostics and easier access to plant-floor data. Using an existing network to include safety information extends those same benefits, allowing seamless communication of the complete automation process on one standard network with one set of hardware and wiring.
4. Make better use of diagnostics: With the ability to embed intelligence-gathering devices into machines without redesign or retooling, machine builders provide customers with self-diagnostic equipment capable of predicting and preventing failures, thereby boosting productivity and reducing repair costs. Moreover, this technology relays the machine condition information back to the machine builder for value-added monitoring and analysis services without compromising existing resources or hindering profitability.
From the end user’s perspective, turning the maintenance function over to the machine builder makes good business sense – it improves machine performance, maximizes capital investments and allows for more cost-efficient use of internal resources.
Machines designed with EtherNet/IP connectivity allow remote troubleshooting and thus provide end users with improved diagnostic benefits. The ability to remotely monitor equipment from a distant location helps reduce fuel usage and related emissions, as well as associated travel time and costs of maintenance personnel who otherwise would go to the machine’s location.
5. Design IT connectivity into the machine: Building information-enabled machines capable of connecting into an end user’s IT infrastructure provides them with critical operational insight, including energy efficiency and overall equipment effectiveness (OEE) calculations. This insight, in turn, helps plant managers reduce waste and optimize productivity.
A machine’s IT connectivity also helps maximize the benefits of a machine’s track-and-trace capabilities. Using advanced information software, manufacturers track and record relevant data at every step of the process to identify when and where resources were used. This visibility offers end users a wealth of data for waste reduction and other improvement programs.
In addition, these systems also help automate track-and-trace procedures of product genealogy through the full chain of custody. In doing so, these systems help companies comply with regulations, document required data, identify potential product quality issues before they reach the market and, if necessary, respond to recalls faster and more efficiently.
Thanks to advancements in technology and best practices, machine builders can play an important role in helping companies implement safer machine designs that support sustainable production practices. By following the above core design principles and leveraging the best of today’s advanced technologies, machine builders can create safer, more cost-effective and reliable equipment.
Steve Ludwig is program manager for Rockwell Automation. For more information, please contact Leanne Hanson at email@example.com.