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By Gregory Hale
With pressure to keep plants running longer and more efficiently between shutdowns, it is becoming much harder to employ a program to effectively update a PLC.

“Our plants are running longer between maintenance shutdowns. We are running 8 to 10 years between shutdowns without the opportunity to interrupt the process,” said Chris Wells, senior staff instrumentation engineer, ExxonMobil Chemical Co. during his talk Tuesday at the 2012 Americas Triconex Technical Conference in Galveston, TX.

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That is why he came up with a plan to better manage their PLCs, which play an important role for any manufacturer. Whether it is an independent safety instrumented system PLC or a machinery control protection PLC for a vendor packaged device, they need a solid plan to keep them running so they remain fully operational.

“We need to be able to source components for longer expected life of 20 to 30 years,” Wells said. They also need support for backward compatibility and to maintain support and expertise over a much longer period of time.

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Wells also mentioned other aspects needed to ensure the PLC lifecycle. “We have to design migration strategies when upgrades are required.” They also have to incorporate online change capabilities and increased flexibility in design.

One of the other areas where users need to keep a sharp eye for their PLC is in the area of cyber security. As mentioned, there are long periods of time between shutdowns, so keeping up with software patching is a challenge.

“We are seeing evidence of increased levels of attacks on systems,” Wells said. “Most current PLC designs are inadequate. We could see some improvement there. You need a good comprehensive security plan.”

In the end, systems have to remain trustworthy.

“PLC reliability is critical to the safety and reliability of the plant,” Wells said. “Longer components and online capabilities are needed.”

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