4/15/2003 - The benefits of fieldbus technology are proven effective in automation and distributed control. Fieldbus technology now applies to machine safety with the integration of safety technology into the Beckhoff Bus Terminal system. The new TwinSAFE Bus Terminals are PROFIsafe-compatible and can be operated in stand-alone mode or with an associated fail-safe control.
With the new TwinSAFE Bus Terminals, Beckhoff offers the option of expanding the proven Bus Terminal system very easily with safety Bus Terminals, thereby replacing the complete cabling for safety circuits. “Safe” signals can be mixed with standard signals without restriction. This saves design effort, installation and material. Maintenance is simplified significantly through faster diagnosis and simple replacement of only a few components.
The new TwinSAFE Bus Terminals only include three basic functionalities: digital KL19xx input terminals, digital KL29xx output terminals and a KL6900 link unit. This enables all common safety sensors and actuators to be connected, e.g. emergency off switch, safety lock, position switch, two-hand switch, cable-operated switch, light curtain, light barrier, laser scanner etc., as well as actuators such as contactor, protective door switch with tumbler, signal lamp or servo drive.
PROFIsafe-based safety concept
The TwinSAFE Bus Terminals are based on the new PROFIsafe standard. Together with a PROFIsafe-compatible fail-safe control, applications ranging from simple to complex can be realised. The PNO Profibus user organisation has prepared a "profile" for the secure transfer of data using PROFIsafe. With this PROFIsafe profile, it is possible to operate safety devices within a Profibus network. No changes to the RS485 bus cable or the wiring are required. Only one fieldbus system for safety-related and non-safety-related automation tasks is implemented. PROFIsafe can be used for tasks up to SIL3 IEC 61508, Cat. 4 EN 954 or DIN V 19251 AK 6.
Fail-safe PLC functionalities in Bus Terminals
The TwinSAFE Bus Terminals can also be operated in a "non-safe" control via the KL6900 TwinSAFE Logic Bus Terminal. A higher-level PLC or a CX1000 Embedded PC or a series BC or BX Bus Terminal Controller with directly connected safety terminals can serve as controller. The TwinSAFE Logic Bus Terminal is the link unit between the safety input and output terminals. It enables the configuration of a simple, flexible and cost-effective decentralised fail-safe control with up to 64 channels. To this end, the required logical safety functions for linking the inputs with the outputs are implemented as a function block and are parameterised depending on the application. For small configurations, the tasks of a small fail-safe PLC can thus be handled within the Bus Terminal system. The KL6900 is suitable for applications up to SIL3 (Safety Integrity Level) according to IEC 61508 or EN 954 Cat. 4 and DIN V 19251 AK6.
Standard and safety I/Os in a single system
The KL1904 and KL1908 TwinSAFE input terminals are digital input terminals with four or eight fail-safe channels. With two-channel connection, the terminals meet the requirements of IEC 61508 SIL3 und EN 954 Cat. 4 or DIN V 19251 AK6.
The KL2904 TwinSAFE output terminal is a digital output terminal with four channels. It switches actuators with 24 V DC up to 2 A. With the KL2904 Safety Bus Terminal, the safety standard SIL3 according to IEC 61508 or EN 954 Cat. 4 and DIN V 19251 AK6 is achieved. If the KL2904 Safety Bus Terminal detects a fault, it switches off automatically (fail stop).
The KL2901 TwinSafe Bus Terminal is a potential feed terminal with integrated switch-off of the power supply. These feed terminals can be placed at any location between the input and output terminals of a Bus Terminals station.
With the Beckhoff Bus Terminals and based on PROFIsafe, users can now install and operate comprehensive automation networks, including safety-relevant applications, very cost-efficiently.
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