What Is a Safety Relay?
A safety relay is a safety device that protects both the operator & machine by avoiding costly replacement of equipment. These devices are simple & offer multiple shutdown paths.
They also have self-monitoring features that ensure correct opening & closing of the internal circuit contact – this prevents jamming.
They can monitor for wire breaks & welded contact sets through timing as well.
Safety relays work to monitor & execute safety functions that reduce risk. These include stopping a movement in a safe & controlled manner, monitoring the position of movable guards & interrupting closing movements during access. They are very efficient & simple in operation, requiring no specific training. They also meet many of the functional safety standards required in machines & industries.
Generally, a safety relay is designed with two output & two input terminals. The output contacts are welded together, whereas the input contacts are mechanically separated. When the relay is activated, it will look for continuity between these two contacts. If there is no continuity – whether through a failure or by pressing the E-stop pushbutton – the relay will close its internal contacts.
It should be noted that the relay will not energize if any of its input channels are open (for example, a faulty contactor or actuator). This is because the output contact in this situation will not close properly, preventing the input channel from being contacted. Similarly, the reset chain of a safety relay will not energize if any of the reset push buttons are opened or depressed. This is because the reset push button opens the connection between EF & GH terminals, which in turn causes K1 & K2 to de-energize. This will prevent the FG & GH terminals from making point B live & triggering a GF signal to the reset circuit.
Safety relays use fixed components and principles to decrease the chance of a fault. Unlike normal relays they don’t require programming to work. They are very easy to install and can help reduce risk by stopping a movement in a controlled way, monitoring the position of movable guards, interfering with their closure during access or executing an emergency shutdown.
Safety Relays are composed of mechanical parts, including a coil, contacts and an iron core. Problems most often occur with the contacts and the coil. In order to avoid contact welding and high and low side driver to ensure that the coil withstands the specified voltage value, it is recommended to use contacts made of stainless steel.
Another way to prevent problems is to protect the coil with a surge protector (not included in the scope of delivery). This will reduce the risk of overvoltages which would otherwise cause line and insulation deterioration.
It is also important to check the wiring and soldering on a Relay before using it, especially after a long period of storage. Unsuccessful soldering or faulty wiring can lead to heating and contact instability, causing the Relay to function incorrectly or even fail completely. It is important to use a flux that does not penetrate the Relay and to use sufficient space between each PCB when soldering. In case of a G7SA or G7SB Relay, a sponge soaked with non-corrosive rosin flux is recommended.
A safety relay is a device that checks for faults in machinery and systems to mitigate risks. They are used to reduce hazards and prevent injuries by detecting problems such as wire breaks, welded contact sets, or error conditions. A safety relay can also detect the timing of a problem and determine whether it is due to a circuit malfunction or a system failure.
To ensure the proper operation of a safety relay, inspect the relay case for physical damage and check all mounting hardware, paddles, and connection paddles to make sure they are secure. Also, examine the case for proper gasket seal and to make sure that it is clean. Verify that target reset functionality is functional and that the disk clearance, spring bias, and spiral spring convolutions are in good condition.
Do not install or store Relays in an environment where they are exposed to water, chemicals, solvents, oil, rusting, and resin deterioration. These can cause corrosion, oxidation, arc discharge between contacts during switching, tracking, and insulation failure.
Whenever you are replacing a safety relay, disconnect the power before removing any terminals to prevent electrical shock. Afterward, you should check the coil resistance to see if it is good. This is done by connecting a resistor between the coil terminals and measuring the resistance. If the coil resistance is infinite, it is bad and should be replaced immediately.
Safety relays help to reduce risk in machinery and equipment to a level where human damage or costly maintenance can be avoided. They do this by initiating a safe response and monitoring the integrity of the safety function. Typical functions include stopping a movement in a controlled way, monitoring the position of movable guards and interrupting their closure during access.
A key feature of safety relays is the use of redundant monitor channels. These are usually a pair of output voltage terminals and a constant current led driver pair of input terminals for the coils. This allows a technician to monitor the operation of the device by running one output and one input channel in a daisy chain from any E-stop push buttons, palm switches or other safety devices and then back to the relay’s output contact connections. This ensures that any input faults such as contact welding on an emergency stop button will be detected and the output contacts will not be welded shut.
Another feature of safety relays is the fact that they are slim, compact components that take up very little space in a panel. This allows them to monitor many different devices from a single point, saving both money and panel space. Finally, most safety relays have status lights to show power to the relay and both channel 1 and channel 2 activity.