Risk Assessment; Enabling Switch Safety Function; Safety Function Requirements - Rockwell Automation Allen-Bradley MobileView Terminal Application Technique

Using a MobileView Terminal With Multiple IP20 Junction Boxes

Risk Assessment

The required performance level is the result of a risk assessment and refers to the amount of the risk reduction to be
carried out by the safety-related parts of the control system. Part of the risk reduction process is to determine the safety
functions of the machine.

Enabling Switch Safety Function

This safety function is the removal of power from the hazard when the safety system detects that the operator does not
have the enabling switch on the MobileView terminal in the middle position, or when the door switch is open.

Safety Function Requirements

Functional safety requires the continuous actuation of a three-position enabling switch to enable power to the motor.
The MobileView terminal enables power to the motor when you squeeze its enabling switch to the middle position.
When you release or fully squeeze the switch, power to the motor is removed. Faults at the enabling switch, wiring
terminals, or safety controller are detected before the next safety demand.
Throughout this publication, notes are used wherever necessary to make you aware of safety considerations.
4
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
Three-position
Enabling Switch on
MobileView Terminal
Rockwell Automation Publication 2711T-AT001B-EN-P - February 2017