SAFETY EXPANSION RELAYS: THE SOLUTION FOR EXPANDING THE NUMBER OF CONTACTS IN SAFETY APPLICATIONS

The Finder 50 and 7S Series both utilise the electromagnetic motive mechanism of classic electromechanical relays, but differ from the latter in that they employ the technique of positively guided contacts.

In the case of positively guided contacts, the contacts (both open and normally closed) are mechanically and positively  linked to one another, such that you can reliably detect the true status of a power contact by monitoring the status of an associated (linked) contact. Thus, the dangerous status of a power contact can be reliably detected and a safe shut-down procedure instigated.

With the correct wiring, the design features of these products can ensure the safe functioning of a complete system, even in the event external faults caused by sensors or actuators.

The use of these devices can be an optimal solution in numerous fields of application:

• Meeting the relevant safety standards. According to the Machinery Directive 2006/42 / EC, section 1.2.1, the control system must be designed in such a way that “A failure in the hardware or software of the control system does not create dangerous situations”. It is therefore essential that within any industrial system there is a specific and rapid control mechanism to force an Emergency Stop in the event of an emergency.
• It must provide for the supervision of all the other safety devices such as safety interlock switches, emergency stop buttons or safety strips.
• It should provide for safe and reliable restarts such as in the case of a supervised reset, or a timed or automatic reset.

The Finder proposal offers a solution for applications where an expansion of the number of safety contacts is required.

Using products designed for this purpose increases the number of devices that can be operated simultaneously and can control higher power loads (up to 400 V – 2A AC15) while minimising  wear of the safety contacts.

The entire range described below complies with the standards EN 61810-3 Type A and Type B, EN 13849-1 and IEC 61508 up to SIL2 and SIL3 (depending on type).

50 Series – Relays for printed circuit boards compliant with EN 61810-3 Type B, with particularly reduced dimensions thanks to the versions with low profile.

This series includes devices with 2 x 8 A changeover contacts, a power supply voltage from 5 to 125 V DC, cadmium-free contacts and 6 kV insulation between coil and contacts.

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48 Series – Modular relay interfaces with two 8 A changeover contacts, a supply voltage of 12 to 24 V DC (depending on the type)

7S Series – Modular relays for applications up to SIL2 or SIL3 (depending on the type) in accordance with the IEC 61508 standard. Within this series are the new Types 7S.16 and 7S.36 guided contact relays. These devices have been developed to meet the need for multiple actuation of a greater number of loads.

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Applications where you would install Finder guided contact relays:

• Safety applications with type A guided contacts according to EN 61810-3 (7S Series)
• Safety applications up to SIL 2 or SIL 3 according to IEC 61508 (depending on type)
• Machine tools, elevators, safety barriers and expansion modules for PLC or safety modules

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