PPG Reduces Risk in Chemical Plant with New SIS
After adopting LOPA, a chemical producer aimed to reduce risk in one of its process units.
AADvance Safety Instrumented System (SIS) - Scalable and flexible SIS provides the level of safety integrity and availability needed throughout a plant.
Minimized Risk - The AADvance® system provides the protection level required to meet the plant's revised acceptable risk level.
Scalable Safety - The system is easily expandable should the plant need to scale up to meet future needs.
With a production history that dates back to 1899, PPG's industrial production plant in Barberton, Ohio, is no stranger to change.
Its products have evolved from raw materials for glass-making operations to the range of specialty chemicals it makes today. Its operations have also completely transformed from manual processes to today's more automated, distributed control-based operations.
One of the most recent changes in the plant was how workers evaluate and mitigate safety risks. Recent adoption of the layers of protection analysis (LOPA) risk-assessment method gives workers a better understanding of the effectiveness of plant safeguards – and has even proven useful in identifying areas where they can further strengthen those safeguards.
Safety Risks Uncovered
The chloroformate unit is one of the Barberton plant's smallest process units but one of the plant's highest safety risks.
Workers at the plant have performed process hazard assessments (PHAs) on the unit for decades in accordance with OSHA's process safety management standard (29CFR1910.119). With the adoption of LOPA, workers now had to evaluate the safeguards identified in those PHAs to quantify and validate their effectiveness.
"We started by evaluating our current interlocks and looking at the scenarios they might be protecting," said Matt Kinsinger, senior process control engineer, PPG Industries. "Then we re-evaluated anything that we had already ranked as a high risk in the PHAs to make sure it had adequate protection. This helped us identify opportunities where the existing control system, instruments and control devices could be improved to meet our acceptable risk level."
From here, Kinsinger and his team developed requirements for a new safety instrumented system (SIS) in accordance with the ISA-84/IEC-61511 standard. The new SIS would need to not only help reduce risk on the process unit but also address other key plant requirements.
These requirements included:
Usability: The team wanted an easy-to-use operator interface easily integrated with existing distributed control system (DCS) interfaces.
Scalability: The SIS system needed to be able to support new or modified plant equipment.
Expandability: The team wanted to be able to easily add to the SIS or add requirements for higher levels of protection based on future analysis or future PHAs.
A Scalable SIS Solution
The team reviewed SIS offerings from two vendors whose technologies were already used in the plant.
They landed on the AADvance system from Rockwell Automation. The flexible and scalable system can be used in operations ranging from small-quantity I/O to large systems and can meet multiple SIL levels in an application. It also provided easy, standard communication to the plant's existing Allen-Bradley ControlLogix controller.
"The AADvance system hit all our boxes for an SIS," Kinsinger said. "The price was great. It met our initial requirements. And it could easily be expanded or scaled-up, as needed."
Once the order was placed, the team had a short timeline of four months to develop the new system and implement it during a planned outage.
To start, Rockwell Automation assigned a project manager and project engineer to support the upgrade. The project manager coordinated the team's meetings, communication and documentation to keep the project moving and verify milestones were met. The project engineer worked directly with Kinsinger and his team to develop a system that met all of their needs.
For the factory-acceptance test (FAT), Kinsinger traveled to the Rockwell Automation Houston facility with a spare controller that was modified to include the SIS communication. The Rockwell Automation team performed a detailed FAT, including simulating every safety instrumented function (SIF), I/O point, and bypass and reset condition.
The SIS was then shipped to the Barberton plant where PPG personnel duplicated the FAT as a site-acceptance test (SAT) without any outside support. This provided a validation of the system as required in the ISA-84/IEC-61511 standard.
Kinsinger and his team hit their target of installing the AADvance system and going live according to the scheduled timeline.
The new SIS provides the protection required to meet the plant's acceptable risk level for the chloroformates process unit. It also offers flexibility to grow or evolve with the plant. This is important because the process is already at capacity and will likely need to be expanded. Also, continual re-evaluation of process hazards in the plant means changes to the SIS are very likely.
"We performed what we felt was a comprehensive review of the current system," Kinsinger said. "But we also wanted room for any additional items to be added to the SIS or requirements for higher levels of protection based on future PHAs."
The results mentioned above are specific to PPG's use of Rockwell Automation products and services in conjunction with other products. Specific results may vary for other customers.
Trademark Information:
AAdvance, Allen-Bradley and ControlLogix are trademarks of Rockwell Automation Inc.
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