
Safety Relays

Relays are switches that open and close circuits. They control one electrical circuit by opening or closing contacts in another circuit. When a relay contact is normally open (NO), there is an open contact when the relay is not energized. When a relay contact is normally closed (NC), there is a closed contact when the relay is not energized. Applying electrical current to the contacts will change their state. Many relays use an electromagnet to mechanically operate a switch, but other operating principles such as solid-state relays are also used. Relays are used where it is necessary to control a circuit by a low-power signal or where several circuits must be controlled by one signal. Depending on the structural features and operating principle, relays are of different types such as monitoring, regulating, auxiliary and protective. Classification of the types of relays depend on the function for which they are used.
Safety relays initiate safe and reliable responses in the event of a hazard to protect equipment and operators. Each safety relay monitors a specific function. Typical functions include initiating the controlled interruption of a device or machine in order to stop movements safely. For example, monitoring the position of moveable guards, interrupting their closure during access. They can also be used as an emergency shutdown mechanism by shutting off the power to specific systems or equipment. Multiple safety relays can be interconnected in order to fully monitor a machine or system.
Products
In the event of a hazard, safety relays can help reduce the risk to a more acceptable level. They are commonly designed to be used in conjunction with other safety relays to increase the functionality and safety levels in work environments. The design and functionality of these relays is similar to regular relays, with a few exceptions. Like a common relay, safety relays use contacts that can be opened or closed. However, they also have the ability to evaluate and then control outputs based on those evaluations. If installed correctly, a safety relay will continue to function if a fault in a device occurs or if a fault is caused by a sensor. The redundant design features of safety relays allow for wiring errors, while still providing proper safety function.
It is very common to see safety relays being used around industrial machinery where safety is critical. Areas such as an industrial manufacturing plant environment, where there are a lot of motors, machinery and conveyors all operating simultaneously. Some of the devices that safety relays will be used with are emergency stops, three position devices, safety gates, pressure sensitive mats, contact strips, foot operated switches and time delay scenarios. Safety relays are tested much more vigorously than normal relays and have a much lower failure rate. The contacts are designed so that they can be completely disconnected, breaking both sides of the power connection as opposed to just one, like many normal relays.