Safety Relays
Safety Relays
I'm familiar with a "Safety Relay" as a specific item required for a product.
A typical "Safety Relay" contains internal circuitry to sense safety circuit inputs and to set as required outputs that control the machine. Safety inputs are typically estops, light curtains, etc. Outputs are typically wired to relays/contactors are used to shut the machine down, such as the control contactor on a small ac motor.
The Safety Relay can be simple, and can also be quite complex with advanced internal setups that are configurable. A number of manufacturers make them, not just AB. The cost is a direct reflection of the number of inputs, number of outputs, and custom configuration capabilities. For a system with a large number of I/O, a configurable Safety Relay often is the most cost effective.
Wiring diagrams are readily available from the OEM. I happen to have used Safety Relays made by Phoenix Contact and Pilz for some applications. Their documentation was more than adequate for my needs.
Modern machine design techniques calls for this kind of approach to handling inputs and outputs that affect safety, as one of the solutions to the results of a risk assessment of the machine.
Is is required for your particular application? I don't know and cannot say, because IMHO it depends on the machine safety risk assessment for that particular piece of equipment.