About Concurrent Safe State Hazards

When you create an Instrumented Function, you will define the safe state of the instrumented function, which is responsible for modifying the process in the event that the condition of the process is in an unsafe state. In other words, if a given process is approaching an unsafe condition, the instrumented function that monitors that process will change the process to a condition that is specified as the safe state for that process.

In some cases, if a given process is in its associated safe state at the same time as a different Instrumented Function, while the individual processes are in a safe state, the combination of these conditions could trigger a hazardous event. For example, assume that to reach a safe state in a Flare system, the process valve needs to vent. Now assume that two process valves need to vent at the same time. In this case, the Flare system can become overloaded due to both processes reaching their safe states concurrently.

In GE Digital APM, the combinations of safe states that can lead to hazardous events are referred to as concurrent safe state hazards. You can document the concurrent safe state hazards that exist for instrumented functions via the Instrumented Function record. In other words, for each instrumented function that participates in a potentially hazardous relationship, you will need to define the concurrent safe state hazard(s) for that instrumented function.

The Concurrent Safe States section of the Instrumented Function allows you to manage all the concurrent safe state hazards that exist for an instrumented function. To define concurrent safe state hazards for an instrumented function, you will need to:

Link the Instrumented Function to the other Instrumented Function whose concurrent safe state can cause a hazard. Instrumented Functions can be linked to one or more other Instrumented Functions through the Has Hazardous Event relationship.
Describe the hazardous event that can occur when the safe state conditions occur concurrently. Since some instrumented functions can participate in multiple concurrent safe state scenarios, in each Instrumented Function, you will need to describe the hazardous events that are associated with that instrumented function. In other words, describing the hazardous event in one Instrumented Function will not automatically populate the linked Instrumented Function with the same description. You will need to access the linked Instrumented Function and enter the description of the concurrent safe state hazard.