MAY-JUN 2019

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34 INTECH MAY/JUNE 2019 WWW.ISA.ORG Digitize and optimize preventive maintenance for process instrumentation Defining scope, optimizing tasks, and using digitalization By Fawaz AlSahan, CAP, SCE M aintenance can be made more effi- cient, helping make operations more efficient and profitable, by leveraging new digital technologies. Conventional time- based preventive maintenance (PM) is widely used throughout industry but has shortcom - ings that can be overcome with smart sensors and analytics (digital transformation). This enables process facilities to move into perfor - mance-based and shutdown-based preventive maintenance. The common categories for preventive main- tenance are: ● Time-based preventive maintenance: Conducted as a defined procedure during a preset interval. ● Performance-based preventive maintenance: Conducted when the instrument perfor- mance goes below a certain limit. Perfor- mance monitoring is done either online (via an online instrument) or off-line (via a por- table instrument). ● Shutdown-based preventive maintenance: Conducted during plant shutdown. The diagram shows the ISO categorization for maintenance in general and preventive mainte- nance in particular. It is worth highlighting that conventional time-based preventive maintenance is widely used and has the following shortcomings: ● Forty to 60 percent of PM tasks add no value to operations. ● Some PM tasks are similar. ● Many tasks require removing the instruments or valve to the shop, while condition monitor- ing is enough to determine reliability. ● New technologies and digital instrument features are not used to optimize tasks. ● Some PM tasks have a high probability of causing unnecessary shutdowns and opera- tion interruptions. Using smart sensors and analytics (digital transformation) resolves these shortcomings and enables process facilities to move into performance-based and shutdown-based preventive maintenance. Defining PM scope, tools, and frequency To have the right preventive maintenance for instrumentation, first clearly define the type and scope of PM. Proper tools need to be se- lected, and the right frequency defined. The scope of PM can include a certain task to be performed. This can be a time-based visual check, time-based functionality check, remov- al and overhauling, or a condition-based task. Second, address who will perform the PM task, such as a field operator or maintenance techni- cian. Determining this point requires agreement

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