Generally using normally closed (NC) switches in series, fail-safe logic exploits a loss of signal or power to de-energize the actuator, therefore stopping a pump or a valve. NO (Normally Open): NO contacts just when the device is turned on. NC (Normally Closed): Only contacts open. Particularly in safety-critical applications including level control, emergency shutdown, and hazardous process interlocking, fail-safe circuit design is a basic concept in industrial automation and instrumentation systems. Whereas today, standard automation (conventional PLCs) and safety automation (electromechanics) are still separate, these two worlds are. In the demanding world of semiconductor manufacturing, SEMI S2 guidelines set the standard for ensuring equipment meets critical environmental, health, and safety requirements. Compliance not only helps keep people, equipment, and facilities safe, it ensures fabs can operate with confidence. The. Suppose that a large laboratory or industrial building is to be equipped with a fire alarm system, activated by any one of several latching switches installed throughout the facility. At first. In order to be able to safely switch of a machine even in an emergency situation, an emergency stop command device is attached and the actuators are controlled via two contactors. What Is a Standard Digital Input.
