Posted on May 4, 2012 - ( views)
Process equipment and system documentation spans multiple databases that are inaccessible to operators, and changes throughout the plant lifecycle can unintentionally make alarm limits obsolete. inBound software addresses these issues, improving situational awareness by consolidating information about safe operating limits for the operator and keeping alarms within safe operating envelopes. The modern control room is a hectic place. Small teams of operators supervise thousands of process variables day and night across multiple screens. As the most safety critical human to plant link, alarm systems make sure that, when something goes wrong, the operator knows exactly what’s happening and the consequences. However, when operating in this data intensive environment, it is their ability to quickly interpret a change in parameters and take action that could mean the difference between unscheduled shutdown and business as usual. Plant safety is often modelled as having layers of protection, and it can be helpful to compare these onion-like layers to alarm thresholds within the alarm system. You might experience a high temperature warning alarm indicating a process has moved away from its optimal conditions; a further alarm indicating the temperature has moved outside the normal operating limits; an alarm above this to indicate the temperature is moving outside of the safe operating limits, after which the Safety Instrumented System (SIS) would typically trip; and a final alarm, should the plant not trip, to indicate temperature has reached the design limits of the system. Providing operators with at-a-glance visibility of the optimal, design and safety limits of safety critical variables is essential to ensure that operators understand the severity of a situation. In most plants, documentation is split between teams with multiple locations and that information is not available at the operator’s fingertips to make crucial decisions when an upset occurs. PAS’ inBound extends their PlantStateSuite © alarm management software to document the pertinent limit information in a single master alarm database. It is then presented to operators so that they can understand the current state of the processes they control within the context of the plant’s “safety onion”. Alarm limits are set by people, and as such are susceptible to human error no matter how meticulous the person. inBound provides a configurable boundary hierarchy to ensure that limits remain within their layer of the proverbial onion. If someone tries to set an alarm limit above the safety instrumented system trip point, for example, inBound’s validation detects and reports the deviation. This capability provides additional assurance that modifications to configuration parameters such as alarm limits and instrument ranges remain within the safe operating envelope of the plant. With the boundary hierarchy and safety limits in place, this information must be presented to the operator in a clear and unambiguous manner that allows at-a-glance interpretation of the safety critical state of the plant. Whereas poorly designed HMI graphics have been shown to degrade safety, quality and process efficiency, a high performance HMI can give an operator a fivefold increase in ability to deal with an abnormal situation before an alarm occurs. PAS provides high performance HMI graphics that use techniques such as pattern recognition and carefully designed analogue indicators to improve operator’s decision making capability under all conditions. Figure 2 is an example of inBound’s safe operating data included in a high-performance graphic display. The light blue color indicates optimal operating ranges with uncolored areas above and below it indicating the full normal range of operability. When the value moves beyond the normal operating range and near an alarm limit boundary, a color change to yellow occurs along with a diamond icon, which indicates a lower priority alarm. If the value continues to stray further from normal and the next alarm limit boundary is crossed, a colour change to red occurs along with a square red icon indicating it is of higher priority. By selecting a specific alarm, the table in the lower right corner of the graphic provides a list of causes and actions for it. inBound ensures that operators are continually aware of operating limits to improve decision-making in all conditions, and validates those limits to prevent the alarm system from failing as a plant’s critical first layer of defence. As we strive for continuous improvement, boundary-aware systems empower operators to make the right decisions and provide another vehicle to ensure a powerful digital ally for operators to maintain a safe and productive process plant.
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PCN Europe’s May issue features an Industry Special concerning the chemical industry; in one of our articles on the subject we look at 100 years of industrial-scale ammonia production, another one shows you how overhead stirring systems helped to improve the efficiency of polymer synthesis. Our Product Focus on Plant Networking includes among others a case study about a SCADA system providing supervision for a confectionary manufacturer. You might also be interested in our technical article highlighting how modern communication technologies change terminal operation. This edition also presents you with many other application stories and product news from all areas of the processing industries, enhanced with datasheets and videos.