Specialty chemicals manufacturer Evonik in Marl, Germany, reported July 12 that it increased availability of a propene (propylene) distillation unit by using a Smart Safety Test from HIMA. With the help of partial-stroke tests on safety-relevant butterfly valves, HIMA adds that cycles between plant shutdowns can be extended from one to three years.
To automate its partial-stroke test, Evonik determined the maximum possible test interval on a positioner, using tests that evaluate the torque characteristic curve of the positioner. These results were combined with HIMA’s HIMax safety controller, which activates the HART channel, controls the partial-stroke test, and compares values from the positioner with setpoints. Evonik and HIMA’s add their successful project was acclaimed as groundbreaking because of its economic significance.
Evonik’s challenge was that a 100% check of an open-close valve means the steady state of the column breaks down, and restarting the plant causes at least one day of production downtime with consequences for downstream processes. One solution is applying flexible testing concepts for safety equipment, which have been described in NAMUR Worksheet NA 106 since 2018. Consequently, HIMA sought to digitalize functional safety with added value, and is addressing four core topics: safety and security, enduring compliance, streamline engineering, and effective change management. This strategy also includes automating proof testing.
"The Smart Safety Test from HIMA makes it possible for the first time to use comprehensive diagnostic options from the field level in the application logic," explains Peter Sieber, strategic marketing VP at HIMA.
While automating their partial-stoke tests on the butterfly valves, project participants benefited from HIMA’s preliminary work and coordination between the safety controller and positioner’s manufacturers of the safety controller.
"A big advantage for us was that the Smart Safety Test is already part of the certification of the safety controller," explains Marc Langehegermann, functional safety engineer at Evonik.
"It was important to us not to develop a makeshift or just a prototype, but to create a complete application that can be copied to other use cases, if necessary," adds Ralph Michaely, project manager at Evonik.
Evonik also expects added value from automating these tests. "The positive operating experience shows we’ve mastered systematic faults,” adds Langehegermann. “We can therefore implement a test concept that manages without a full-stroke test for as long as possible."
Evonik adds it wants to use the knowledge and experience it’s gained in other areas to increase plant availability with flexible test cycles because this not only increases productivity but also reduces maintenance costs. "We see potential benefits for digitalization over the lifecycle of a safety device," adds Sieber. "Digitalizing functional safety can create added value beyond safety functions, not only by helping to cut costs, but also by increasing plant availability."
