Emergency-stop switches turn off machinery in case of potential damage or risk to life and limb.
|IDEC safety switch|
|Conventional safety switch|
But such switches can fail due to improper installation, damage during transportation, accidental removal of the contact block, and other reasons. The XA/XW Series of switches from IDEC Corp., Sunnyvale, Calif. (idec.com), surpasses current international standards on E-Stops to preclude such risks. Springs keep conventional E-Stop switches in the normally closed (NC) position, letting a machine run. An operator hitting the switch with too much force can break or dislodge a part, letting the spring-loaded contact stay closed and the machine continue to run. In XW/XA switches, a spring ensures NC contacts pop open if the switch is damaged. IDEC switches also use four contacts. Currently, many companies use E-Stops with three contacts; two contacts trip the power and the third alerts a safety-monitoring relay. The extra contact gives operators the option to add another circuit and qualifies the switches for Level-4 applications. The devices secure from the rear of the control panel, so buttons cannot be removed from the front. The switches use push/pull and push/turn reset methods, eliminating confusion when operators reset the switch.