System Overview ProSafe-COM 3.00
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2.3 Sequence of events recording
It is essential for safeguarding systems to monitor start-up and shut-down procedures in real system time
and record these events for later analysis. The SER provides just that ‘black box’ function, which makes it
possible to retrieve and analyse the events associated with a particular process situation.
ProSafe-COM
Figure 12: Sequence of events recording
All data is communicated with other members of the ProSafe family or a ‘host’ system. Many interfaces
are available using proprietary protocols as well as industry standards.
ProSafe-COM maintains an event list in memory. All ProSafe safety system events are kept and sorted on
time stamp. This list can be printed or made available to the process engineers for thorough process
investigations or analysis of process shutdown sequences. The event time stamps of the ProSafe safety
system digital field I/O have a resolution of 1 millisecond, sequence of events can be guaranteed with
accuracy in the order of 10 to 20 msec.
The size of the event list is configurable, with a maximum of 10.000 events. The most recent events are
saved on disk and can be inspected after a recovery from a power-down situation. Maximal 10% of the
available events will be stored on disk. For example, if the configured event list in memory is 10.000
events long, then 1000 events will be saved on disk during a power outage.
2.4 Forcing
statuses
A ProSafe safety system works autonomously. However, in start-up and maintenance procedures
overrides may be necessary. By using overrides, situations that are normally faulty can be temporarily
ignored by the ProSafe safety system.
In case of a start-up procedure, an override may be necessary in order to put the ProSafe safety system
to work. When an override is set, the values read via the I/O modules are temporarily ignored in order to
proceed. If no override is used, the start-up procedure probably will be terminated immediately because a
situation occurs that is not normally allowed.
When the process has started up properly, the override procedure can be terminated and the I/O will be
checked again in the normal way.
A maintenance override is necessary to temporarily disable the I/O that can activate a shut down. This
may be necessary when testing or maintaining the ProSafe safety system.
Override procedures always require a double action: a manual enable with a key, and an
override command from e.g. a DCS or matrix panel.
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Copyright Yokogawa Europe Solutions B.V.
TI48J01A00-00E Oct 2010
