54733-10BA2L
1 – 102 02.2017
7 Functional Safety Volume 1
7.9 Periodic Inspections
The periodic performance test is used to check the safety function
in order to detect possible non-recognizable dangerous errors and
thus to test the operational capability of the measuring system at
appropriate intervals. It is the responsibility of the operator to select
the type of inspection.
The intervals depend on the PFD value used (see table in chapter
7.11).
The test has to be carried out so that the correct safety function can
be established in the interaction of all components. The methods
and procedures used in the tests must be stated and their suitability
must be specified. The inspections have to be documented.
If the performance test is negative, the entire measuring system
must be taken out of service and the process must be kept in a safe
state by other measures.
The first test must be performed directly after the initial startup, so
that the reference values and the general conditions are defined,
and these are available in the following periodic inspections for ref-
erence.
During the test, the person performing the test must ensure the
safety-related monitoring of the process by other technical and/or
organizational measures.
7.9.1 Test Options
The options to test (proof-test) the measuring device as a compo-
nent of the measuring system differ depending on the application
the instrument is used for. The test options are listed below. Please
note that this should be done under operating conditions, provided
certain operating conditions have an impact on the measurement.
For example, if there is a stirrer in the beam path, then the stirrer
must be operated as under operating conditions. The same applies
to a container under gas pressure, and to heating and cooling jack-
ets, to name two further examples. It is the responsibility of the
operator to select the type of inspection. The interval depends on
the PFD used (see Table in chapter 7.11).
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