Machine Safety in Factory Automation
Tom Moore, Lead Analyst, Discrete Machine Safety, IHS | March 05, 2015Machine safety has evolved in recent years. The idea that safety components and systems are only installed to appease the minimum requirements set out by law has eased. Today, companies have realized that safety is also linked to performance and to the image of a company. Unsafe environments can be damaging to a company’s reputation, particularly in Europe and the Americas. This, and the potential performance gains, has put safety at the forefront of end user and OEM considerations; more are considering safety as a core component of a modern factory.
This article discusses some of the key factors affecting machine-safety and its adoption in factory automation. Overcoming some of the hurdles and utilizing some of the drivers is a key to the success of machine-safety across industrial automation.
Safety for Performance
Minimum levels of safety to meet the guidelines set out by law and regulation often do little to improve a machine’s performance. However, additional safety can lead to gains in performance, which is a key focus for modern factories working in an incredibly competitive environment. Modern factories have the capability for high-speed throughput, which means any downtime can be very costly. Safety overrides production; a simple safety stop can bring a production line to a halt for a considerable length of time while the problem is identified and the line reset.
Modern safety systems enable much more capable production lines, which may be able to continue production at a reduced rate even if a machine is being adjusted or materials loaded. Systems that go beyond a simple E-stop can now reduce motor speed and, in the future, torque, stopping or slowing production lines which are monitored by safety controllers or PLCs in place of simpler safety relays.
Safety system functionality is crucial for a facility because it means a problem can be quickly and easily identified. Using modern controllers with fast, reliable and safe networks means specific events can be pinpointed to exact components, buttons and doors, and the reason identified through on-board diagnostics. Visual aids can also be used, with light beacons and strips showing physical location of the stop. Potentially, there is also the opportunity to make more use of mobile devices, for example, smartphones. These devices can help customers reduce the downtime by using positioning in relation to the stop to minimize travel time, as well as propose solutions to the stop. This can be hugely beneficial because it means that if a shutdown has occurred unnecessarily, a line can be restarted quickly.
There is also the potential for a line to continue running, depending on the machine, even if a door or gate is opened and an interlock switch triggered. The motor and its drive can switch to an advanced safety level and continue running at reduced speed until the door is reset, while monitoring the situation in case an immediate stop is required. This ability to monitor and control a situation means that considerable downtime can be avoided.
Performance metrics can add up to considerable gains for a factory. If there is less downtime, then there is greater production time and more product throughput. Many factories are using performance metrics to not only measure production, but also stoppages; this can be greatly beneficial as a way to outperform the competition. The onset of solutions, rather than components, means this is becoming common.
Solutions, Components and Integration
Safety components (for example, E-stops, relays and interlock switches) are an integral part of safety and are often implemented separate from the machinery rather than as an embedded solution. Today, this approach is by far the most common and is often viewed as the best way to implement safety because of its non-software approach, reducing the potential for errors. It also reduces the fear that the system may restrict the machine’s performance and damage the machinery. In developing regions such as India, safety is not valued as highly. It is often the case that safety networks are separate for fear that the control network may be slowed by a safety stop.
Although using safety components separately often works in very small/basic applications with 1–3 functions, it does have limited functionality and often makes recovering from stops more difficult and time consuming because of limited diagnostics. It can increase downtime while the safety system or device that has caused the stop is identified. Embedded safety solutions mean that the level of information that can be gathered is increased. They also offer greater capabilities, including higher intelligence and more functionality. Safety components can often be embedded into machinery during the build to maximize the efficiency of the design and to improve effectiveness. This has many benefits, the most important are related to performance. When safety is integrated into the machine it is possible to track stops more quickly; utilizing the latest networks means that a machine can be restarted quickly.
The market for individual components was still very large in 2014. A large number of users prefer a separate architecture for their safety systems as they believe that it will be less complex to install and less likely to affect machine performance. Indeed, latest IHS figures suggest the market for both basic and advanced components is growing well; the trend to higher-performance components is particularly prominent in developed regions.
The safety relay market is considerable and remains larger than the controller market. The market for controllers is growing at a faster rate than relays. There is an ongoing trend to adopt higher-performance safety devices, which is partially driven by reduced cost and by the need for diagnostics and reduced safety distances, which increases performance. A single safety controller can easily do the tasks of 10 or more relays, which is beneficial in cost and space, as well as direct sensor input.
For those looking for more complex safety devices than relays, without the need of a safety PLC, there is now the option of configurable safety modules, which offer a solid middle ground. Although devices and their implementation are becoming more complex, users are still keen to simply monitor and adjust/control safety. Safety drives now make up a considerable portion of the safety component market; many are simple devices implementing safe torque off (STO) only. Drives incorporating higher levels of safety can continue operating while monitoring safety.
Convergence of Safety and Control
In addition to factors contributing to performance and the implementation of solutions there is also a convergence of safety and control.
As well as the possibility to embed safety, it is now possible to replace traditional relays or modules with embedded safety controllers that provide advanced diagnostics for the safety systems to manage control of the entire machine. This is not surprising because of the dawn of high-end safety-based controllers, more complex applications and increased technological capability.
Embedded safety provides a level of integration, while it also provides adequate separation between the safety and automation lines. This reduces the reluctance of users, who have for many years rejected the idea of integrating the safety and non-safety automation systems. This reluctance was due to a fear that their machines will be affected by the safety automation system. Vendors of safety equipment are working hard to change this viewpoint because embedded safety can offer great benefits in performance.
It is likely that as safety relays are replaced with controllers, this will become a more apparent trend and users will become more accepting of the technology and integration into machinery.
Safe Networking
Networking is an important topic and is becoming more prevalent in the minds of end users and OEMs. There are a number of networking technologies available that carry safety branding. Most are based on existing industrial Ethernet and fieldbus protocols.
Initially, there was concern that some standard Ethernet variants were not intrinsically safe. Most of these concerns have now been dealt with and Ethernet variants are now equally, if not more, capable than older fieldbus equivalents.
Of major concern to a number of end users is whether newer, safety-based networking technologies will easily integrate with existing networks. Often the case is yes, but still users are often cautious and decide not to integrate the network. This can mean that efficiencies of the network and safety devices cannot be realized because communication is handled separately.
Standards
The EU and American standards covering today’s machine builders, end users and OEMs are perhaps the most daunting part of implementing safety. Legislation has existed in one form or another for many years, but has become more complex with time.
It is often the case that local standards will refer to each other, so to have a piece of machinery fully covered by the different directives can be a difficult task. It often falls to the industrial automation vendors to provide the information that a user needs to pass safety standards. Vendors now dedicate much resource to ensuring that customers’ equipment is up-to-date. This is especially arduous when standards are so frequently updated, regionally specific and complex.
An update of the EU safety standard is being produced which should simplify the process. This standard will be ISO/IEC 17305. The intention of this is to combine and streamline existing standards. It is projected that the new standard will be in place before 2020.
Standards elsewhere in the world are much more fluid and in some areas don’t exist at all. The ideal situation would be a single worldwide standard, but this is unlikely to happen soon, if at all. This means that machine builders often have to comply with multiple safety standards. An advantage to European machine builders is that the EU standards are some of the strictest so it is often easier to adapt machinery to other regional requirements. Upcoming Chinese legislation (when it is finalized) will be very similar to EU standards, which again, will be a major advantage for European machine builders selling to China.
The Future
The machine-safety market is still a relatively young and fast-moving market when compared with factory automation in general. Implementing the latest safety solutions can help to boost not only a machine’s performance (from reduced downtime), but also a company’s image by avoiding damaging press. Only in recent years have end users and OEMs begun to understand this and utilize safety not just to be safe, but to improve performance.
The latest in high-end networked equipment, including on-board diagnostics and remote HMI capabilities to find and quickly resolve machine stops, means that so much more can be done than previously. There is a knowledge gap with users in some cases, so industrial automation component vendors are contributing much resource to help users understand all the options, including the standards, and many users now rely on this to implement the latest standards and technologies. If vendors can work to simplify these standards (particularly in the European Union), as well as develop more intelligent technology, this will benefit them and safety users; they can implement safety more widely, based on sound knowledge.