Franklin Fueling Systems EVO Series, Справочное руководство

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Rules Engine
Rules are another method of programming the EVO™ for positive shutdown. Rules are event
based in comparison to conditions that are status based. Using rules for positive shutdown has
limitations. Rules as programmed operate independently from one another and for this reason
can lead to undesired results. Using the rules engine for sensor positive shutdown is not advised
due to the fact that the rules are event based, acting on an individual event versus the status of
the devices associated tied to the particular device shutdown. For example:
• Rule # 1- Event – Sensor #1 Alarm-Action Pump Disable (UNL)
• Rule # 2 Event – Sensor #2 Alarm -Action Pump Disable (UNL)
• Rule # 3 Event – Sensor #1 Alarm(clear)- Action Pump Enable (UNL)
• Rule # 4 Event – Sensor #2 Alarm (clear)- Action Pump Enable (UNL)
Scenario: Rule #1 has an Event (Sensor Alarm), and the UNL Pump disables as the Action.
Rule #2 has an Event (Sensor Alarm), and then clears with Rule #4. The pump will then be
enabled even though Rule #1 (Sensor Alarm) is still active. Once an event happens, the action
is performed, any future event will supersede the initial event and act based on the rule
as programmed. Rules are isolated events and actions will respond according to individual
programming of each rule and will not recognize other rules when activating or deactivating. This
logic set up is why rules should rarely if ever be used for the purpose of positive shutdown using
sensors.
Rules however can be used for other scenarios involving positive shutdown, such as a low
product level. A RULE can be programmed to disable a STP at a Low or Low Low level. The
counter rule can then be created to re-enable at a low-level cleared event. This set of rules works
as there are only two events being monitored, and they are on the same device (tank) with no
other events of the same nature that will conflict.