How does a safety relay work? Relays with Forcibly guided contacts

Safety relays ensure operation of equipment can only occur when the safety requirements have been fulfilled. A modern safety relay integrates signal and control inputs, control outputs and outputs that allow correct operation to be monitored. For example, contacts may be welded, and this detection is used to prevent the commencement of operation). Applications that might require the use of a safety relay include:

• Guards
• Light Curtains
• Safety Mats
• 2-Hand Control

When an error occurs, the safety relay will initiate a safe and reliable response. Each safety relay monitors a specific function. They are a simple and efficient way to meet existing safety standards, resulting in safe operation for your workforce and equipment as well as ensuring their long life. Reducing risks should be a number one priority for all organisations, to protect the welfare of their employees and to reduce expensive damages to equipment. With Finder’s range of modular relays with forcibly guided contacts, we can ensure protection.

A modern safety relay described above is a complex assembly of logic elements (possibly even a microcontroller) as well as switching elements. So, it is not in itself a simple relay.

However, at the heart of many safety relays or systems will be a relay with forcibly guided contacts. The forcibly guided contact relay has normally open and normally closed contacts mechanically linked in such a way that they cannot both be closed at the same time. This allows fault conditions such as welded contacts to be determined.

Finder has several safety offerings for different applications, which will be discussed further on in the article.

The main way relays provide safety is by providing isolation. Finder’s industrial relays provide the equivalent of double insulation between the coil and the contacts.

Relays with dedicated safety features (50 Series, 7S Series and the 22 Series with mirror contacts or mechanically linked auxiliary contacts) can be incorporated in ways that allow the correct operation to be monitored and incorrect operation detected. Note the detailed design of a safety system to provide the appropriate level of protection is a complex subject.

What is SIL?

SIL stands for Safety Integrity Level. A SIL is a measure of safety system performance, in terms of probability of failure on demand (PFD). There are four discrete integrity levels associated with SIL: SIL 1, SIL 2, SIL 3, and SIL 4. The higher the SIL level, the higher the associated safety level, and the lower probability that a system will fail to perform properly. As the SIL level increases, typically the installation and maintenance costs and complexity of the system also increase. Specifically for the process industries, SIL 4 systems are so complex and costly that they are not economically beneficial to implement.