Can OEE lead to better valve health and reliability?

My office is located just outside Hartford, CT. That puts me midway between Boston and New York City. As a result, Hartford has a pretty even mix of Red Sox and Yankees fans. With baseball season in full swing, it’s common to hear fans around town debating which team is better. In my opinion, it isn't one team or the other being better that matters – it’s the rivalry between these two powerhouses that makes them great.

In my role as an engineer, I’m on the road half of the time visiting customer sites or participating in industry conferences. Both activities routinely put me in direct contact with staff from both maintenance and operations. When the topic of key performance indices (KPIs) comes up, the two groups take sides without fail as though they’re battling in a big-leagues playoff. While maintenance staff members favor overall equipment effectiveness (OEE) as a key metric for measuring performance, people from operations routinely jump on the bandwagon for process-specific KPIs. In my opinion, they’re both winners – putting eyes on any metric usually helps improve a plant’s performance.

In the name of full disclosure, my background is squarely on the process side of things, and equally important, I’m not a huge baseball fan – I tend to follow college football more than the MLB. Even so, I see a clear relationship between OEE and key process KPIs – especially those metrics that focus on valve health. Consider the three elements of the OEE calculation:

  • Availability - Uptime really does matter. This is a foundational aspect of OEE, and it’s mirrored in various process-related KPIs. Chief among those metrics is output travel. This process metric assesses the average amount of movement produced by a given valve as it modulates control of a process. More specifically, it’s a measure of full strokes performed by a valve per hour. The higher the output travel, the faster the valve will reach its mean time before failure (MTBF) limit. If the valve fails, then the process will be down and availability will be crippled – a concern for both maintenance and operations staff.
  • Performance - OEE also addresses efficiency as a serious performance factor. With its focus on production cycle time, OEE captures performance information similar to process KPIs such as stiction. Specifically, stiction – also referred to as sticky friction – indicates when a final control element is unable to respond efficiently to a process’s changing dynamics. The friction limits a valve’s ability to make the subtle adjustments that are needed to maintain efficient control, and it can introduce cycling and instability into the process, unnecessarily extending cycle time.
  • Quality - As with uptime and efficiency, OEE also takes quality into consideration. More to the point, it’s a measure of time lost as a result of poor quality. From a process perspective, KPIs such as output distribution similarly specify when a final control element is operating at a physical constraint and is putting quality at risk. Think of a valve that’s pegged in either the fully open or fully closed position. In that position, it is unable to meet the process’s needs. Such a limitation hampers the valve’s ability to get to temperature, produce adequate flow, maintain level, or achieve another control objective. That directly undermines quality.

Whether you’re in maintenance or operations, it’s essential to measure performance in some concrete, repeatable, and unbiased fashion. OEE is widely used by maintenance professionals as their benchmark of success, and without a doubt it’s a winner in performance and reliability circles. Process KPIs are similarly equipping Operations staff with essential performance measurements. They’re both winners – each is helping to improve plant performance and asset reliability which is the unifying goal. My only parting comment is this: Go Hokies!