E-stop recall prompts a safety warning

A safety expert at Siemens Automation and Drives is warning that the failure of some emergency-stop manufacturers to comply with the BS EN418 safety standard is putting lives at risk. The warning follows a recent recall of a push-pull E-stop by a well-known supplier, following the failure of a latching function that could allow machinery to restart with personnel in a dangerous area.

Siemens says it has received reports of malfunctions in a variety of emergency stop buttons.

"It is obvious that the companies supplying E-stop devices should be doing more to ensure that machine-builders are fitting equipment which complies categorically with BS EN418," says Paul Easton, Siemens` product manager for command devices. "The severity of this issue cannot be ignored - incorrect E-stops can cause accident, injury or even fatality."

BS EN418 requires E-stops to be "tease-proof" - a latching function must operate when initial pressure is applied to the E-stop to create a signal. The machine cannot be restarted until the emergency has been cleared and the safety circuit has been closed by hand. Non-tease-proof devices can send a signal without any guarantee that a latching function has taken place, allowing a machine to be re-started before safety checks have been completed.

Siemens alleges that some suppliers has been providing misleading descriptions of their E-stops, encouraging customers put price ahead of technical performance.

"The importance of tease-proof functionality is often hidden within the small print of certain brochures," Easton explains. "It is clear that some manufacturers are still not complying with the regulations by providing and listing non-tease-proofs mushrooms as E-stops. It is essential that these products are listed correctly. In the absence of clear advice, buyers often choose a non-tease-proof device, even though the cost advantage is seldom more than a few pence."