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Advanced Engineering 2021

NEC Birmingham(B40 1NT)

03/11/2021 - 04/11/2021

Join us in our 12th and most important edition to date, as we invite engineers and management from all (more)

Certifying optical safety outdoors – keeping an eye on a new standard

Certifying optical safety outdoors – keeping an eye on a new standard

Dr Martin Kidman of Sick examines the challenge of maintaining functional safety when moving systems outdoors.

The unpredictability of the great outdoors has always precluded manufacturers, machine-builders and systems integrators from providing their customers with a safety solution that can be certified and internationally-recognised for the use of sensors and sensor systems for the detection of person in the open air.

Despite the obvious, and almost, countless challenges of validating the performance of outdoor optical sensors intended to protect people from machinery, the relentless development of autonomous, or semi-autonomous systems has generated a growing demand from industry for an internationally-recognised Technical Standard. Such a standard should also complement and correlate with those used to certify safety systems indoors and provide a presumption of conformance with the European Machinery Directive.

The functional safety standard IEC 61496 contains the design and performance requirements for Electro-Sensitive Protective Equipment (ESPE) for the detection of people. It gives clear, but limited, guidelines for a variety of subjects including typical conditions representing indoor use in an industrial environment and the design, functional requirements and test to determine the ESPE’s “Type” (2, 3 or 4).

However, there is an increasing demand in applications that may not necessarily be in an indoor industrial environment. In such cases generic functional standards like IEC 61508, IEC 62061 or ISO 13849 can be used, but applying these standards requires an in-depth analysis of systematic capabilities of the sensor or sensor system. Furthermore, there is not enough guidance in these standards to prevent design failures, or insufficient capability to detect in certain environmental conditions such as outdoors, which could result in an intolerable risk to the safety of people.

Of course, there are many excellent outdoor optical technologies in use all over the world. From laser distance sensors, to LiDAR scanners and vision cameras, there is a wide range of options with sufficiently robust solutions for applications such as building security, anti-collision in cranes and ports and many more. However, none of these systems come with a safety rating that can be used to provide presumption of conformance with the Machinery Directive.

The technological sophistication and refinement of outdoor optical technologies to be able to cancel out the false signals caused by challenging conditions, such bright light, moisture, visibility and temperature, have made them extremely capable and reliable.  Nevertheless, agreeing a certifiable technical safety standard that defines what such devices can achieve, and sets out their limitations, in an almost infinitely-variable outside environment, has remained a big challenge.

Undaunted, since 2016 a working committee – initiated by industry leaders including Sick – has been working on developing a Technical Standard, IEC 62998, which is forecast for publication some time in 2019. It is intended that IEC 62998 will complement the existing functional safety standards to provide a safety classification system for electro-protective devices used in certain environments such as outdoors.

While it is still early days, the development has been greeted with interest and excitement by the industry as a much-needed door-opener to the development of new technologies, particularly in automated and mobile applications. It’s expected there may be a real need for safety-certified systems not only in industry and factory automation, but in mobile automated vehicle technologies in logistics, ports, agriculture and mining for example. In the longer term, technological developments made now will pave the way for future refinements and understanding of the operation of semi-autonomous driving systems in future.

It’s likely that the requirement for safety certification will be realised where mobile vehicles need to operate safely both within a factory or warehouse, as well as outdoors. We’ve already seen some early interest and development in this application, for example, in heavy industries where large AGVs may need to travel between nearby buildings to transport tooling or parts, perhaps needed to cross roads or yards without endangering the safety of people nearby. Another area is likely to be in industries where providing a validation of safety compliance is important, for example, for outdoor automated systems such as passenger boarding bridges in airports.

The conundrum for safety laser scanners is that their ultimate strengths, their utmost sensitivity to changes in conditions, are at the same time a potential weakness in outdoor environments. The system, by nature, is designed to stop working when the environment cannot be guaranteed to be safe, so the availability of the system could potentially be limited in extreme weather conditions or dusty or sandy environments. More than anything, the development of outdoor applications using safety laser scanners will, therefore, depend upon the assessment of each individual case in close discussion with the sensor manufacturer to balance the need for detection sensitivity with availability of the overall system. Delivering a flexible and productive material flow will be a key requirement of the automation concepts of the future, as well as real-time condition monitoring.

IEC 62998 only applies if product-specific standards do not contain all of necessary provisions, or product specific sensor standards are not developed. It classifies outdoor safety devices as Class A to F, to distinguish them from interior safety device classifications. Performance classes of sensors and sensor systems are defined in accordance with existing safety standards but there is no definition, of or interconnection to, the “types” as defined in IEC 61496. For example, IEC 62998 Class D would correspond to PLd (ISO 13849), SILCL2 (IEC 62061) and SIL 2 (IEC 61508) but has no link to Type 3.

As a result, a class D device was the focus of product development and, at the SPS IPC DRIVES show in Nuremberg at the end of November, Sick previewed the industry’s first safety laser scanner to be certified to IEC 62998 for use in outdoor applications.

The Sick outdoorScan3 allows automated guided vehicle systems to navigate safely through outdoor industrial environments. Using Sick’s innovative outdoor-safeHDDM scanning technology, a development of the technology already used successfully in our indoor MicroScan3 safety laser scanner, it promises exceptional reliability in outdoor conditions such as bright sunlight, rain, snow and fog. As well as being Type 3, PLd and SIL2, the Sick outdoorScan3 will be IEC 62998 Performance Class D, certified for use outdoors.

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