To achieve world-class reliability, it’s not enough to focus on reliability improvements alone. Benchmarking helps operators to identify numerous areas in which they should focus their reliability-improvement initiatives. The best way for process operators to justify their time and effort up front, and to assess the benefit of their investments over time, is be able to assess the ultimate financial impact the initiatives are able to deliver.
While Availability (expressed as a percentage of time the process is running divided by planned production time) is a useful and widely used metric to characterize plant performance, it does not provide a complete picture of overall plant reliability. In recent years, the overarching concept of Overall Equipment Effectiveness (OEE) has emerged as a key performance indicator for monitoring and managing the reliability of critical plant assets and systems, and provides a more direct indication of how improved reliability practices saves money for the operator.
Specifically, OEE reflects how machinery, production lines and processes are performing in terms of availability, performance and quality. As it pertains to reliability-improvement initiatives, “OEE is one of the best measures of performance, because it takes into account not only whether the equipment is available and running when it should be, but whether the facility is making quality product when it should be,” says Baptista.
Equipment effectiveness can be maximized through efforts to control or eliminate reliability or productivity issues that arise from the “six major losses” that can be categorized in the following groups and subgroups:
- Unplanned downtime losses (Availability Factor, A)
Equipment failures (breakdown losses)
Set-up and adjustment losses
- Speed losses (used to calculate the Performance Factor, P)
Idling and minor stoppages
Operation at reduced speed
- Quality losses (used to calculate the Quality Factor, Q)
Defects in process operations and reworking
The OEE value is obtained using the following equation:
OEE = Availability Factor x Performance Factor x Quality Factor or OEE = A * P * Q
During plant operation, each of the three factors A, P and Q is calculated over time as a percentage. Thus, for a given installation, if the value of each were 90%, OEE would be calculated as 90% x 90% x 90% = 0.73%. Depending on the specific industry sector, OEE values >80% are considered to represent world-class operation, while OEE <60 denotes a need for serious improvement.
As noted earlier, for the best sustained results, the ability to make strategic changes to the overall approach to reliability requires standardized protocols and practices related to work-flow management, planning, scheduling and execution of maintenance activities. “If you can carry out all maintenance-related activities using repeatable processes — for instance, standardizing processes related to creating work orders, prioritizing tasks, scoping the job, executing the job, and analyzing the results — you’ll get improved results,” says Ginder. This will eliminate redundant steps, which will drive efficiency, reduce excessive expenditures and improve reliability-related outcomes.
If possible, operators of multiple facilities should also implement their improved reliability procedures across all of their sites. The dissemination of standardized practices across multiple facilities will drive reliability for the company, and will enable comparative analysis to be conducted to support continuous improvement.
Check back next week to learn what makes a great reliability program. We look forward to hearing your thoughts on this topic.