An operating envelope is a collection of operating variables on a plant, that when exceeded, put the integrity of equipment at risk. Any business operating a processing plant wants to maximize asset uptime and minimize maintenance costs as well as unplanned outages. In support of this goal is the management of a plants operating envelope.

In the past, typical management of operating envelopes consisted of counting the number of alarm breaches for a given variable. This resulted in many hundreds, and in some cases thousands of operating envelope excursions ("excursions") per month. In the vast majority of these cases, these excursions were not legitimate breeches of the operating envelope. Rather they were a result of the control system or operator performing exactly as intended: moving the process back within the operating envelope quickly.

BP Kwinana realized that it was important to be able to distinguish between these "blips" and genuine excursions. Being able to do so, would have many benefits. It would make retrospective analysis manageable as the number of excursions was reduced. This means it is possible to direct preventative maintenance, and plan shutdown activities at the areas most at risk. It also allows rapid diagnosis of damage that may have resulted from an excursion and mitigating action can be taken rapidly. By accurately determining genuine excursions, both long and short term action can be taken to minimize the risk of process upsets, and in some cases, loss of containment.

The major benefit BP Kwinana has been able to obtain though, is the ability to notify and escalate notifications in real time, to actually prevent excursions. Due to a pre-occupation with determining genuine excursions, there is sufficienct confidence to escalate notification of breeches through the leadership hierarchy right up to the duty manager.

The system developed was built is support of a very deliberate work process that clearly defines ownership of the various aspects of the process. This has resulted in an increased understanding of what the operating envelope is, as well as clear accountabilities for ensuring the operating envelope is adhered to.

Overall this system has reduced the number of excursion by more than two orders of magnitude, simply by using complex algorithms to distinguish between genuine excursions and short breeches. Further, the ability to notify the breech of an envelope real-time has meant that the number of genuine excursions is decreasing. All this translates to increased availability, more effective allocations of maintenance and turn-around labour and safer operations.