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SAFETY & INTEGRATION Applications and Benefits of Safety Light Barriers

Jan 3, 2019

Safety light barriers were first introduced in 1984 as security devices to protect humans and guard machines in the industrial environment. Due to further developments in robotics, safety light barriers have become increasingly relevant. This article explores one such solution along with its applications.

The current trends in machine and plant engineering include increasing levels of performance density. Machines need to fit into the smallest space possible, and users want increased performance and productivity. One such product is the SLB 240/440, which has been launched by the Schmersal Group. It is regarded as the smallest range of safety light barriers in the world with built-in evaluation. The product has also received the GIT Security Award, 2018.

The development of optoelectronics

Three trends, in particular, have been observed to have given rise to optoelectronics. In assembly and handling technology, close cooperation between humans and machines is a central trend. Human-robot cooperation is well beyond the prototype stage and is now being used in practice. In machine safety, functions, which were originally taken over by hardware components, are shifting to software and traditional disconnecting safety equipment while electromechanical safety switches are increasingly being replaced by contactless optoelectronic safety equipment. Optoelectronics has several benefits, which have also contributed to its development. The operator has a clear view of the working area and no safety doors are required. The safety equipment is significantly more flexible, thanks to functions, such as, muting and blanking due to which it can distinguish between people and materials.

Key features

The SLB 240/440 is a response to each of these trends. The new safety light barriers in this range have built-in evaluation and are characterised by their compact dimensions. They fit well into the systems around them and can be fitted quickly and easily even into confined spaces. The SLB 240/440 models with cable connection require a space of 28 x 32 x 72 mm (W x H x L), while the versions with connector sockets are 28 x 32 x 91 mm in size. The product is not only compact but also has a wider range of 15 metres. The third model, the SLB 440-H (dimensions with cable connection WHL 28 x 33 x 111 mm and with connector socket WHL 28 x 33 x 131 mm) can achieve a range of up to 75 metres.

Wide range of applications

The single beam safety light barriers are useful for securing smaller hazard areas. For example, the safety-oriented optoelectronics system provides reliable protection for the operating personnel, as every interruption to the light beam triggers a signal which switches off the potentially hazardous machine movement. At the same time, the working processes are not ‘behind closed (safety) doors’, but instead are transparent. With these properties, the new safety light barriers have a range of applications, for example, on workstations for assembly and handling, and in the wood, paper and printing industries.

Direct integration into safety circuit

All SLB light barriers have safe semiconductor outputs and can be included into the safety circuit, even without external safety evaluation. The new product range complies with the requirements for all Type 2 or Type 4 applications. The safety light barriers can also be used for process protection.

Simple installation and setup

All versions have a visual set-up guide, which makes commissioning easier. They also have a 4-way coding level, so that if multiple light barriers are used in one application, up to four sensor pairs can be operated in one direction, without influencing one another. Parameterisation does not require tools like, a PC or commissioning system. A simple command device is sufficient. Set-up, automatic and restart modes, parameterisation and a diagnostics mode are also available.

System solution for safety

The new safety light barriers are a system solution, which can be combined with the relevant components of the safety-related control systems. For example, they can be combined with the new safety relay modules in the Protect SRB-E range or the new Protect PSC1 safety controller generation. They can also be integrated into safety-related bus system, such as, AS-i Safety.

Other products in optoelectronics

Depending on the size and complexity of the hazardous area, the user can select between the SLB light barriers, multi-beam SLG light barriers and the light curtains in the SLC product range. Compact models are also available. User-specific special models, for instance, with a special degree of protection (IP69K) or customer-specific variations are available. An example is the safety light curtains, which were developed for a manufacturer of stack cutting machines whose shape matched the outline of the hazard area and the casing.

Shift in safety features

Recent trends in the industry have led to a shift in safety features, with optoelectronics taking a central position. The ease and efficiency of light barriers, along with the wide range and compactness, make them the most suitable option for safety of humans as well as that of machines. Such products can also be customised to suit different specifications and have a wide variety of applications, thus giving it a lot of potential.

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