ISA 2012 Automation Week
Track: Safety/Environmental
Tuesday, 25 September, 3:15-4:45 pm, Room 205B
Rajeev Limaye
Praxair Inc.
Since the introduction of ISA-84 standard for Safety Instrumented System (SIS) Lifecycle, most leading organizations in process industry have adopted it, and some are still in the process of understanding and applying it in their engineering work practices. ISA-84 is a performance based standard. It specifies the requirements of performance of the Safety Instrumented Functions measured in terms of Safety Integrity Level (SIL). The standard does not prescribe how the system should be designed and implemented. ISA has published technical recommendations to interpret the standard in the form of guidelines and examples of implementation of ISA-84.
Still there is some confusion when it comes to selecting the adequate instrumentation, especially when the same process measurement is required for multiple Independent Protection Layers (IPL) such as safety function, continuous control, and alarm.
The “Operator Response to Alarm as Protection Layer” presentation in the Safety/ Environmental track focuses on the design considerations when alarm is used as an Independent Protection Layer—whether or not the instruments and sensors can be shared between different protection layers and how they could be arranged in fault-tolerant configurations to achieve safety, reliability, and independence. During the plant design and P&ID reviews, such guidelines can be very handy while deciding appropriate and adequate instrumentation. The design reviews become very easy when such prescriptive guidelines exist within the company. Time available for operator to take corrective action in response to an alarm and human ergonomic factors are some other important considerations.
In most organizations, the teams who design safety systems are different from the teams who implement the Alarm Management based on ISA-18.2 standard. If the teams and their efforts are not aligned, they end up creating multiple databases that are impractical to be maintained by the operations. The presentation talks about what type of data is common between process safety and alarm management teams and how to streamline the efforts so operations can continue to maintain it.
