Automation Canada Machine Safety Issue May 2021 - 11

HOW TO CHOOSE THE RIGHT SAFETY SOFTWARE?
BY MARTIN LALONDE
Soſtware for programmable logic controllers can vary greatly from the
programming language they use to the testing and documentation
tools they offer. There are a lot of them out there, with many
manufacturers having proprietary soſtware that works with their devices
only. Choosing the right one can be tricky. This article looks at the
requirements for safety soſtware from the point of view of the safety
standards, as well as the practical features needed to get the most out of
your safety soſtware.
REQUIREMENTS FROM SAFETY STANDARDS
The two standards that we will consider are ISO 13849, which is for
the safety of machinery. In it, there is a particular section on the V model,
which describes the verification and validation process. The other
standard of relevance is IEC 62061, which deals with the functional
safety of safety-related Control systems. Chapter eight of this standard
talks about soſtware requirements.
ISO 13849
The
V-model
describes
the
necessary
steps
for
designing
safety-related soſtware. The leſt side of the V deals with the design of the
tool, if you will, and the right side of the model deals with the
application of the tool to a specific use.
IEC 62061
The next thing that I want to draw your attention to is the different
levels of soſtware in the regulations. IEC 62061, Table six, describes
three levels of soſtware.
1. Soſtware level A, which is a pre-assessed soſtware platform designed
for safety applications. This is where the Samos® Pro Compact and its
matching soſtware Samos® Plan 6 would fall under.
CANADIAN AUTOMATION
2. Soſtware level B is a soſtware platform for designing applications,
which typically run on a PLC, but are not designed explicitly for safety
applications. For example, a standard PLC programming interface from
Rockwell or Siemens, that is designed for programming but not
explicitly designed for safety. Additional steps would have to be taken
to achieve safety.
3.Soſtware level C uses another language other than the limited
variability of language. An example of that might be embedded
soſtware applications that might be programmed using C or using RISC
microprocessor programming at a very low level. The advantage of this
would be that you probably gain some efficiencies in terms of higher
response time or very defined applications. But, for most people, this is
not the right solution because there is a lot more effort required in
developing suitable safety soſtware at this level.
VOLUME 3, ISSUE 3
11
https://www.wieland-safety.com/
Automation Canada Machine Safety Issue May 2021

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