Automation Canada - Machine Safety - 11

HOW TO DETERMINE THE REQUIRED
PERFORMANCE LEVEL
For example, at a food machine
manufacturer, a worm screw feeding a
machine must be accessible for cleaning and
removing a jam in operation. During both
procedures, jog must be allowed, making
padlocking impossible since power needs to
be applied to the motor to perform jogging of
the motor. Working at normal speed with an
open guard isn't an option, as the power of
the motor and the screw could crush the hand
of the operator. In addition, this procedure is
required to be performed several times per
shiſt. However, the screw works at low speed
in inching mode and a horn and a light beacon
warns the operator before their departure.
According to ISO 13849-1, this situation has
an S2 severity with an F1 frequency and a P1
possibility of avoidance. Therefore, the
required performance level is D, meaning a
security system must meet
this
level of
performance.
To build a system with a performance level
D, it's critical to design a safety function that
considers all components. If not, the result will
be no better than the weakest link in the chain.
According to ISO, the five fundamentals of
performance level are: Structure, Reliability,
Diagnostic, Resistance and Process.
CANADIAN AUTOMATION
To build a system with a performance level D, it's critical to design a safety function that considers
all components. If not, the result will be no better than the weakest link in the chain.
According to ISO, the five fundamentals of performance level are: Structure, Reliability,
Diagnostic, Resistance and Process.
VOLUME 4, ISSUE 2
11
Automation Canada - Machine Safety

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