OEE Time Categorization
The most important factor in tracking OEE is accounting for what equipment is doing 100% of the time that it is scheduled or intended to run. In Plant Applications, you do this by capturing all the time when the equipment is up or down—even the time when it is not scheduled to run. You apply reasons to the downtime, and categorize these reasons according to four main categories:
-
Unavailable Time
-
Outside Area (External Downtime or Line Restraint)
-
Performance Downtime
-
Unplanned Downtime
Using these four categories, Plant Applications places all equipment time and events into meaningful groupings that are used to calculate OEE.
Once configured, Plant Applications will:
-
Subtract the amount of time that is not relevant to the measurement of equipment’s effectiveness while it is scheduled or intended to run (Unavailable Time and Outside Area).
-
Monitor production and rate, and for given products compare the actual production rate to the production rate target specifications
-
Capture events either manually via operator interface (Proficy Client) or automatically via historian tags, which collect appropriate data from the controls system.
-
Translate the output from historian tags into downtime reasons—which you have created in reason tree(s) and which have already been appropriately categorized.
The chart below illustrates the fundamentals of how equipment time is handled in Plant Applications, and the following calculations show how each component of the OEE equation (Availability X Performance X Quality) is derived. For more information, see the OEE Glossary and OEE Calculations topics.
Click on chart sections to quickly link to the legend below.
Availability = Gross Running Time (B) / Loading Time (A)
Performance = Actual Output (D) / Ideal Output (C)
Quality = Good Output (F) / Actual Output (E)
OEE is a score assigned to the unit based on the three preceding parameters.
OEE = Availability X Performance X Quality
Calendar Time
Total amount of time being considered.
Unscheduled Time
Proficy does not differentiate this category from Unavailable Time.
Unavailable Time
A built-in category for downtime that represents known periods of time where production is not expected. Such reasons include: weekend, holiday, vacation, plant is closed, unit is down for maintenance.
Line Restraint (Outside Area)
A built-in category for downtime that occurred and was not due to the equipment in question but is attributed to external reasons. Such reasons include: blocking or starving a unit.
Loading Time
The amount of time that a unit is scheduled to run and is ready to run, whether the unit was running or not running.
Unplanned Downtime
A built-in category to represent downtime that does not fall into the following categories (Unscheduled, Line Restraint/Outside Area, or Performance/Speed Loss).
Gross Running Time
The amount of time that a unit was producing product, whether the product was good or not good.
Gross Running Time = Loading Time – Unplanned Downtime
Ideal Rate
The theoretical rate of production for the unit as stated by the equipment manufacturer. If not stated then it is the highest known observed rate.
Ideal Output (Ideal Production)
The theoretical amount of product (good and bad) that could have been produced if the unit had not been "down".
Ideal Output = Ideal Rate X Gross Running Time
Actual Output (Actual Production)
The amount of product (good and bad) that was actually produced by the unit.
Speed Loss
Downtime that was attributed to a slowdown. Speed Loss + Minor Stops = Performance Downtime.
Minor Stops
Downtime that was brief and is not considered downtime. Speed Loss + Minor Stops = Performance Downtime.
Availability Rate
This is a ratio between the amount of time a unit should have been running and how much was it actually running.
Performance Rate
This is a ratio between Ideal and Actual. This is in terms of production amounts or production rates.
Quality Rate
This is a ratio between the amount of Good Production and Total Production
Performance Downtime
A built-in category to represent downtime that was attributed to a slowdown or a minor stoppage.
Downtime Categories
To calculate the components of OEE (Availability, Performance, Quality), Calendar Time is segmented into the Plant Applications downtime categories.
In order to generate meaningful reports, reason trees must be designed effectively to provide further drill-down groupings for each of these categories. For further information, see Reasons and Categories.