Safety relay vs Normal relay: What's the difference?

The safety relay is a protective barrier employed in the safety circuit upstream of the devices in the general control system. Safety relays can be used with many protection systems and even safe mode.

A safety relay circuit is a vital component of a large-scale system. The common relay can be employed for general overvoltage, voltage conversion, speed, and coordination.

Safety relay entails safety certification and level; it gives extendable and functional traditional safety assurance, and it’s frequently used in relay expansion. The system’s safety control is more stringent than standard control, both required and widely recognized. A safety relay is typically used to combine switches, whereas a relay is typically used to link contacts. They’re used at various levels. A safety relay is made up of numerous relays and circuits that work together to compensate for unusual flaws in each component and provide a complete relay function that is reliable and low-failure.

The higher the safety factor, the lower the error and failure value. As a result, separate safety relays must be constructed to safeguard different grades of machinery, with the main goal of protecting machinery workers exposed to varying levels of risk. So, what makes a safety relay different from a standard relay?

Table of Contents

What is a safety relay?

Devices that carry out safety duties are known as safety relays. A safety relay will try to lower the risk to a manageable level in the case of a hazard. The safety relay will respond safely and dependably if an error occurs. Each safety relay is responsible for monitoring a different function. A machine or facility can be completely monitored by linking them to other safety relays.

Safety relays are a quick and easy solution to comply with current safety regulations, resulting in safe operation for your staff and equipment as well as long service life. Any organization should make risk minimization a top priority to protect its employees and avoid costly accidents or equipment replacements. In general, if the danger can be reduced, it should be done.

How does a safety relay work?

Safety relays are easy to use and have a well-defined structure. As a result, their use does not necessitate any special training. To properly operate a safety relay, all required is some basic electrical understanding and awareness of the requirements that apply to your specific circumstance. Because of their compact design, outstanding dependability, and most significantly, they meet all of the needed standards, safety relays have become widely used. They’ve become an essential part of any new plant or machine that requires safety features. Nowadays, safety relays are available to meet almost any requirement.

Types

Single-function or multi-function safety relays are available. Single-function safety relays are the most cost-effective alternative for smaller machinery that requires a specialized logic device to accomplish the safety function. Multi-function safety relays can replace multiple single-function safety relays.

They’re less difficult to put together and require less intricate wiring. Multi-function safety relays also allow for more flexibility in design or control panel adjustments. Monitoring safety relays are also recommended for scenarios requiring many safety devices and little zone management.

Use

It’s easy to turn on safety relays. They do not necessitate any special training to utilize. Safety relays have become popular because of their compact structure, high reliability, and ability to meet specified criteria.

They have become an essential component of any new system or machine that requires safety functions. Safety relays are found in various monitoring and control systems, including safety mats, light safety curtains, movable guards, emergency stop buttons, three-position devices, two-hand control devices, magnetic switches, and contactless safety sensors.

Benefits

In an anomaly at two contact sites, safety relays assure switch dependability. Safety relays also have built-in diagnostics and constantly monitor the signal line, which is a significant advantage.

This eliminates the need for additional wires to detect anomalies on the line, whether field-side or controller-side. To avoid causing unexpected line interruptions, safety relays also offer immunity to test pulses from the control panel.

Why Use a Safety Relay?

Machines and automation have the potential to be harmful. Even little engines have a lot of power and can easily cause harm. But power isn’t the only aspect at play. Knives, heavy objects, noise, and vibrations are all potential threats. In reality, anything that has the potential to injure or damage one’s health is a risk.

This means that such risks and risky circumstances must be considered whenever a new machine or automation system is designed. Because only then will you be able to lower the hazards.

Machines can create conditions that are so dangerous and life-threatening that it is a legal requirement.

Even though the law requires it, identifying all hazards and harmful scenarios associated with machine design can be difficult. Allow me to reduce the steps necessary to locate and identify the dangers associated with a machine. Because only after you’ve discovered the hazards can you take steps to mitigate them, such as installing safety relays and devices.

Safety Relays in the Field

Safety Relays are frequently seen in control devices like:

Light Curtains

Light Curtains protect personnel in the proximity of potentially dangerous moving machinery by acting as a tripwire. A stop signal is issued to the necessary equipment when any device’s infrared beams are broken.

Light curtains are usually attached to a safety relay, which is in charge of actually disconnecting the motive power from the hazard. Some safety relays may additionally have a muting feature, which allows the safety function to be temporarily disabled. For example, when employed with light curtains, muting allows items to pass through without tripping the safety relay.

Safety Mats

Safety relays that are pressure-sensitive can be used in conjunction with safety mats to ensure staff safety and supplement other safety equipment. For instance, while the safety mat is enabled, a series of light curtains can be set up to allow things to pass through, providing access to load or unload a machine. Safety mats can also be used as a stand-alone precaution. When triggered, they can send a stop command, just as light curtains.

Three-position Devices

When troubleshooting an application, safety devices like a three-position device can be extremely useful, and this category includes a wide range of options. Three-position devices frequently have a pressure-sensitive joystick that must be kept in a specific position to operate. When the user releases the joystick, it returns to its default stop position.

Two-hand Control Devices

A two-hand control device is required for activities requiring a high level of safety concern. When you don’t want the operator to reach into the dangerous area, such devices are essential. A one-handed control device can be used when the device is out of reach of the operator controls.

Magnetic Switches

A magnetic switch is useful when a door or hatch must be closed, or two items intersect or align. When the machine loses contact with the two sensors, an emergency stop signal can be delivered to the appropriate relay to stop the machine from working safely. Magnetic switches are small and light, making them ideal for gates and switches. A magnetic switch frequently boasts a long operational lifetime because no mechanical contact is required for activation. Magnetic switches are unaffected by water, dirt, or dust, allowing them to be used in a wide range of settings and circumstances.

Emergency Stop Buttons

When a machine breaks down, or someone is in danger, emergency stop buttons (also known as E-stop) are used to bring it to a halt. All E-stop buttons should have a yellow casing and be red. Some emergency stop buttons will include an emergency grab wire that allows users to engage with the stop interface even when they are far away from the button. For easier identification, the grab wire should be red.

Non-contact Safety Sensors

A non-contact safety sensor, like a magnetic switch, is appropriate for use where segments must be aligned, but they do not need to be in direct touch, unlike a magnetic switch. Multiple sensors can be used in conjunction with some of these sensors, allowing for more precise design as needed.

Interlock Safety Switches

When components are locked together, an interlock safety switch recognizes this and can be utilized to maintain them until specific requirements, such as the completion of an operation, are met. This can be performed in various ways, such as by employing a spring lock or by the device locking itself when it reaches a specified position.

Differences between Safety Relay and Normal Relay

The outer dimensions of a safety relay and a common relay are different. The following are the main distinctions between a safety relay and a general relay:

Because it contains guided contacts, the safety relay, unlike other relays, can detect its welding status and allow the control circuit to determine if contacts are welded together. This is a mechanically connected contact. A usually closed (NC) or break contact cannot reclose if a normally open (NO) or make contact remains closed. The NO contacts will not shut if a normally closed (NC) contact fails to open when the relay is turned on. For switching, a standard relay uses simply mechanical connections.

A safety relay has a larger size than a regular relay. A safety relay results from cutting-edge engineering with a lot of sophisticated circuitry built into it. The circuit of a mechanical relay is straightforward. That’s why it’s so small.

Various switching, protection, and alerting functions are available on the safety relay. The safety relay, for example, keeps individuals safe. It monitors a user’s actions to guarantee that nothing he does harms his health, either intentionally or unintentionally. Furthermore, when a machine is potentially hazardous to the user, it continuously monitors all hazardous processes and detects even the tiniest irregularity. In most control circuits, a standard relay is used solely for switching.

A standard relay comes in a variety of colors. (Predominantly white) The yellow hue of a safety relay makes it easy to spot. A safety relay controls the combination of switches. For contact linkage, a standard relay is employed.

Conclusion

The term “safety relay” does not refer to a fault-free relay; rather, it refers to a relay that takes predictable actions when a fault arises. It has a necessary steering contact structure, which is unlike the typical relay and assures safety in contact fusion.

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