What’s needed in process automation?
Using obsolescence for justification isn’t easy. While maintenance costs probably are rising and spare parts may be getting scarce and expensive, true maintenance savings normally aren’t large enough to justify the capital investment. Obsolescence is a viable approach only if you can show an increasing risk of control equipment failure shutting down a critical process. Establishing the risk factor becomes the challenge.
It’s difficult to convince management that a system is about to fail when it has no history of failures. Predicting failure is a tough task. Mean Time Between Failure (MTBF) data for older, especially obsolete, equipment are hard to obtain. Plus, MTBF data normally are component-based, not system-based — making it hard to use these data to estimate control system life because a control system consists of multiple components.
Fortunately, modernization can provide considerable financial benefits and thus significant incentives for a project. Whether these benefits will suffice to justify an upgrade, of course, depends on the company’s capital-spending payback policy. Some firms demand a one-year-or-less payback, others allow two-to-three-year paybacks, while a few factor in reduced risk of system failure in determining an acceptable period.
Past financial failures
Unfortunately, many control-system modernization projects haven’t provided the economic benefits that were initially expected. While engineering is happy to have the newest technology to implement and operations personnel view the process as easier to run, management may see the new system as a financial failure.
Several factors can contribute to an automation upgrade project not bringing the expected economic value:
- The process control system was chosen based on technology instead of how well it allows operations to improve the manufacturing process.
When DCSs first became available, the process control engineering department chose or at least strongly drove the choice of system. Selection was centered on the ability of the control system to meet certain technical standards and the initial sales price.
Operations wasn’t involved much if at all in specification and selection, and real analysis of operational improvements wasn’t done.
Leaving operations out of the selection process usually led to a system that wasn’t friendly to the operator. Related process information was scattered on numerous graphic pages, causing the operator to have to toggle among several graphics. While this may be tolerable during normal operation, it can become time consuming and frustrating when abnormal situations arise and the operator needs to manipulate the process and closely monitor measurement readings.
Modifying the system may be difficult and may need the assistance of a system engineer. So, operations management may resist changes in graphics suggested by the operator. Also, it’s very likely that any complex control strategy will be abandoned if it’s not easy to use and troubleshoot without the presence of a system engineer and the process run in a manual mode.