Safety Function Realization: Risk Assessment; Guard Locking And Monitoring Safety Function; Safety Function Requirements - Rockwell Automation Allen-Bradley Compact GuardLogix 5370 Controller Application Technique

Safety Function Realization: Risk Assessment

The Performance Level required (PLr) is the result of a risk assessment and refers to the amount of the risk reduction to
be conducted by the safety-related parts of the control system. Part of the risk reduction process is to determine the safety
functions of the machine. In this application, the Performance Level required by the risk assessment is category 3,
Performance Level d (cat. 3, PLd), for each safety function. A safety system that achieves cat. 3, PLd, or higher, can be
considered control reliable. Each safety product has its own rating and can be combined to create a safety function that
meets or exceeds the PLr.

Guard Locking and Monitoring Safety Function

This application technique includes one safety function: guard locking and monitoring.

Safety Function Requirements

This safety function makes sure that the hazard has stopped, and that safety output power has been removed, before the
gate is unlocked upon request. It also monitors the lock and door, and it drops output power if they unexpectedly change
state. If any fault occurs, such as loss of communications, output power to the safety actuators is dropped. While the door
is open, its status is monitored to prevent unexpected startup while the door is open. When the door is closed and locked,
hazardous motion and power to the motor do not resume until a secondary action (Reset button depressed) occurs.
The safety function in this application technique meets or exceeds the requirements for Category 3, Performance Level d
(Cat. 3, PLd), per ISO 13849-1 and control reliable operation per ANSI B11.19.
Door Locking and Monitoring with a 442G Access Box and an Integrated Safety Controller Safety Function
From: Risk Assessment (ISO 12100)
1. Identification of safety functions
2. Specification of characteristics of each function
3. Determination of required PL (PLr) for each safety function
To: Realization and PL Evaluation
Rockwell Automation Publication SAFETY-AT129B-EN-P - November 2018 5