7 out of 10 relay preference for simpler safety

London - If you’re one of those engineers who prefers to stick with more basic, tried-and-tested technology for your safety controls, then you’re not alone - at least when it comes to safety relays.

Apparently hard-wired relay-based safety units - those typically featuring simplified safety logic, one or two safety devices and simple on/off safety control – remain the preferred option for 70% of manufacturing plant applications.

The more advanced option of using integrated safety solutions is currently just around a 30% play, despite industry expectations that they would, by now, be far more dominant.

The stats come from Ian Murgatroyd, European product manager at Rockwell Automation, who commented “Take up of integrated relays is still a bit slow, though data indicates it will be the biggest growth area in future.”

At a recent press event in London, Murgatroyd linked the reluctance to the fact that integrated options require end users to have a knowledgable workforce on site to do functional safety management of the machines.

Another issue, the product manager suggested, is the confusion surrounding changes to EU machinery safety standards – for example, whether to use ISO 13849 or EN62061.

Most significantly, perhaps, he pointed out that many safety relay applications involve relatively small and simple machines.

“These often have intelligent gate switches to show what is going on with the machine and so do not need integrated safety,” said Murgatroyd.

In 2010 the European market for discrete machine safety components was estimated to be Euro631 million. Safety relays represented the largest sales area for discrete machine safety components by type within Europe, at Euro151 million.

These sales volumes, plus the preference for keeping things simple, have not been lost on Rockwell, as evidenced by its new Guardmaster Safety Relay (GSR) range, which focuses more on saving cost and effort for end users, than wowing them with new gizmo features.

The GSR is billed as a “drastically simplified” range of safety relays that can replace Rockwell’s portfolio of up to 250 existing safety relays, with a mere six products.

The range is being targeted at a wide range of manufacturing sectors - the bulk of take up, though, is likely to be in the food & beverage and packaging industries, according to Rockwell managers.

GSR products will allow customers to simplify their inventory and usage, said Paul Davies, a business leader at Rockwell. He hastened to add, though, that the company will also continue to supply its existing portfolio in this area.

Features of the new range include a universal input that allows devices, such as safety interlock switches, emergency stop switches, pressure sensitive mats and safety light curtains, to use the same set of terminals.

This, said Davies, removes the requirement for a specific safety relay for each type of input device and allows simplified system design, inventory management and maintenance.

With two separate safety inputs in a 22.5mm housing, the GSR offers twice the functionality of a standard relay, said Rockwell literature. Users, it adds, can increase the number of outputs via a TUV-approved single-wire connection whilst maintaining the safety integrity at SIL3.

A single rotary switch, combined with the single-wire connection allows ’and/or’ functional control, for applications such as zonal control, maintenance functions or global/local emergency stop circuits.

Overall, Rockwell claims its GSR offerings can reduce purchase cost by around 10%, by replacing the need for two devices and reducing associated purchase costs and inventory management.

Consolidating two safety relay functions into a single housing also reduces the footprint on the DIN rail, leading to space savings of 50%.

The ability to connect two safety input devices to one safety relay, meanwhile, can remove the need for complex relay-to-relay wiring. This is claimed to allow a 30-50% reduction in wiring costs.