Highest new safety standards at heart of relay modules

IDEC Corporation's new HR5S safety relay module is said to give designers and OEMs more options to provide better end user safety, while cutting costs and improving the productivity of machines and equipment. The HR5S is designed specifically to meet ISO 13849 Category 2 requirements, says the company.

Safety relay modules, like the HR5S, are a key component for interlocking equipment and driving it to the safest possible state, in case an emergency-stop pushbutton or other safety input signal is activated. If designers are using a system with Safety Category 3 or 4, then redundant safety inputs, controllers, and outputs must be provided.

Safety Category 2 requirements

When Safety Category 2 is acceptable, then only single input connections, less expensive safety relays and single outputs are needed. Fewer and less specialised components can be used, control panel space is saved and field wiring is decreased. Design, installation, testing, and support efforts are also minimised.

Machinery and OEM builders design safety into their equipment following the ISO 13849 'Safety of machinery', which was updated a few years ago to clarify Category 2 requirements, so interpretation is easier for users. Now, when the machine risk is relatively low, OEM designers can opt for a more streamlined safety implementation by using Category 2, instead of a more rigorous safety implementation using Category 3 or 4.

Designer flexibility increased

“IDEC’s new HR5S safety relay modules specifically comply with Category 2 requirements, increasing designer flexibility when the required performance level (PLr) risk assessment identifies conditions to be PLc or below. While categories 3 or 4 mandate redundancy, Category 2 allows a more straightforward safety implementation where ‘testing occurs immediately upon demand of the safety function’,” adds IDEC.

HR5S safety relays are available in three configurations for a range of applications. The ‘Simple’ type can be used for applications up to PLc, while ‘Standard’ and ‘Off-Delay’ types work for designs up to PLd and add failure detection features. “While most Category 3 and higher relays consume 45mm of installation width, the HR5S is only 22.5mm wide and can be mounted on DIN rails or a backpanel surface,” IDEC further states.

Standards compliance

Push-in terminals are used for ease of installation and vibration resistance, accepting solid wires up to 16 AWG or stranded wires up to 18 AWG with ferrules. Inputs are rated for 24V DC, and outputs are rated up to 250V AC 3A. The HR5S safety relay modules comply with many standards, including EN ISO 13849-1:2015 and UL 508.