What is Safety Relays: Working, Function, and Their Applications?

Protection at industrial processes is always a concern, and an imperative aspect of the safety of such processes is the safety relay. Hence, these specialized devices form a critical component of each system to help minimize the chances of an accident and more dangerous electrical risks in industrial systems. But the big question is: what is a safety relay? What relationship does it have with a conventional relay? How does this technology work, and where can it be used? 

What is a Safety Relay?

A safety relay is an electromechanical switching device that guarantees the safe status of the machine and equipment. It is important to emphasize that safety relays are developed to monitor the safety circuits and initiate specific protection procedures in the event of a fault. Their purpose is to detect the safety-relevant parts of a machine, including emergency stops, light curtains, or safety doors, and the corresponding reaction of the system in case of failure.

The safety relay can be said to serve a crucial role in improving general safety system reliability through the use of spare and self-checking features. It makes them an inevitable element in so many industrial and automation settings.

Safety Relay Working Principle

The safety relay working principle is critical to understand. These relays contain numerous redundant circuits. The basic concept in a safety relay is that the relay continuously scans input from the safety devices like emergency stop switches or protective covers. In case any such anomaly is sensed, like a wire snap, a malfunction, etc, the relay will once give a command stop so that the machine ceases to operate.

Besides identifying electrical faults, the safety relay working principle also includes checking functions to see whether the relay is capable of performing the required function. In case any internal fault is found, the safety relay will not allow the system to re-initialize until the fault is corrected so as not to cause any unsafe situations.

On the other hand, safety relays are special units that increase the reliability of the protected circuit. What may happen within a normal relay is that it can fail and cause some hazardous conditions, which the safety relay is designed to detect and eliminate any fault brought about by the failure of the normal relay. This is probably why safety relays and normal relays are vital in machineries that are operating in dangerous areas like manufacturing plants or automation systems where if a system fails, it can cause a lot of harm.

Safety Relay Applications

Some common safety relay applications include:

• Emergency Stop Systems: In some industries that require quick stopping of the machines due to the risk of an accident, the safety relays are used to monitor the emergency stop buttons. When the button is pressed, the relay quickly drops the supply voltage to the machine, instantly taking it out of action.
• Access Control to Hazardous Areas: They are used in the locking circuits that operate to control the amount of access allowed to certain highly risky areas of machines. For instance, if a safety door is open, the relay will shut down the machine to protect the operators from being endangered by moving parts.
• Light Curtain Monitoring: In industrial settings where employees deal with mechanical parts such as a robotic arm or other technologies, light curtains are used as barriers to feel the presence of human beings. A safety relay constantly checks the light curtain, and should it detect a person, the relay makes sure the machine halts immediately.
• Motor Overload Protection: These relays operate with safety relays to protect motors against overheating. However, the safety relay cuts off if the motor goes beyond its thermal levels.
• Safety Mats: Safety mats are placed in areas where some workers may have to work around complex moving equipment. A safety relay makes it possible for the machine to turn off if a person steps on the mat to avoid an unfortunate event.

Safety Relay Function

The first application of a safety relay is to control the safety-relevant components of a process in an industrial plant to safely operate the available machines/technologies at a facility. A safety relay receives input from various safety devices such as emergency stop buttons, safety light curtains, or mats. Then, it processes the signals to decide whether the machine is safe to continue or must be stopped in the interest of safety.

Other functions include controlling access doors, speed monitors, and temperature limits. At times, safety relays also cooperate with thermal overload relays to limit the heat generation in the motor or electrical system to avoid overheating the systems, thus ensuring that equipment is within the correct required limits.

Safety Relay vs Normal Relay

Since comparing the safety relay with the normal relay, the only noticeable difference is that of safety and reliability that it offers. A normal-type relay is used for switching purposes in electrical circuits but does not include features such as fault sensing. They are usually used for managing simple electrical circuitry functions such as switching lamps ON or OFF, management motors, or other regular activities.

Conclusion

Schneider Electric’s safety relays provide an essential safeguard in industrial systems by continuously monitoring and controlling safety-related components, such as emergency stops, light curtains, and access doors. These devices offer added layers of security and reliability compared to standard relays, effectively reducing accident risks by instantly halting operations when faults are detected. For industries with heavy machinery and high-risk processes, Schneider Electric’s safety relays are invaluable, promoting safer environments and supporting smooth operations across diverse applications.

Read Also -  A Guide to Choosing the Best Relay for Your Needs

Frequently Asked Questions

Q1. Can a safety relay be used in a home setting?

Ans: Safety relays are designed for industrial applications with a significant risk of injury or machine malfunction. Homes typically use standard circuit breakers and relays.

Q2. How long does a safety relay last?

Ans: The lifespan of a safety relay depends on usage, environmental factors, and the specific model. Generally, they are designed to last for many years with proper maintenance.

Q3. Are safety relays mandatory for all industrial machines?

Ans: While not all machines require safety relays, they are crucial for systems where safety is paramount, such as heavy machinery or automated systems with moving parts.