Overall equipment effectiveness (OEE), the most common metric used to characterize the performance of a plant, is expressed as a percentage of the total planned or scheduled production time. Total effective equipment performance (TEEP), on the other hand, while also used to characterize performance, is expressed as a percentage of the total time available – that is including non-operating time intervals.
OEE is calculated by taking the product of three factors – performance, quality, and availability:
OEE (%) = Performance (%) × Quality (%) × Availability (%)
Performance is calculated by comparing the ideal and actual production times. Alternatively, performance efficiency can be expressed in terms of production rates (e.g. units produced per hour). In formula form:
Performance efficiency (%) =
(Ideal production time / Actual production time) × 100%
Or,
Performance efficiency (%) =
(Actual production rate / Ideal production rate) × 100%
Quality represents the percentage of produced units that are within acceptable standards. The number of defective units is deducted from the total number of units produced, then expressed as a percentage of the total:
Quality (%) =
[(Total # of units produced – # of defective units) / Total # of units produced] × 100%
Availability quantifies the actual amount of time that an equipment is able to perform its function, compared to the planned duration that the same equipment is supposed to run.
Availability (%) =
(Actual operating time / Scheduled operating time) × 100%
Given the total available time, idle time, and total downtime, availability can alternatively be expressed as:
Availability (%) =
[Total available time – (Idle time + Total downtime)] × 100% / (Total available time – Idle time)
TEEP as defined by the Society for Maintenance & Reliability Professionals (SMRP), is calculated by taking the product of four factors, three of which are also used to calculate OEE – performance, quality, availability, and utilization.
TEEP can therefore be expressed in terms of OEE as:
TEEP (%) = OEE (%) × Utilization (%)
Where utilization is calculated by deducting the idle time from the total available time, then expressing the term as a percentage of the total available time:
Utilization (%) =
(Total available time – Idle time) × 100% / Total available time
From the given formulas to compute for OEE and TEEP, it becomes obvious that the main difference between the two metrics lies on the time component that is being considered.
OEE is concerned with the performance of an equipment as a percentage of the scheduled or planned production time – excluding idle time intervals, while TEEP measures the performance of an equipment as a percentage of all time available.
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