Uptime and downtime

EN 13306 splits a machine's time into uptime and downtime. Downtime is only the time lost to preventive maintenance and faults, not every hour the machine stands still.

In maintenance, uptime is the time a machine is able to do its job. A machine that waits for an order, for material, or for power is still in uptime. The times behind MTTR, MTBF, and availability all come from this split.

How does EN 13306 split a machine's time?

The standard sorts every hour by one question: could the machine do its job? If yes, the hour is uptime. If no, because of preventive or corrective maintenance, the hour is downtime. A second question cuts across both: did the plant need the machine in that hour? Those hours are required time. The standard writes "up time" and "down time" as two words.

Time	Clause	The machine is in it when …
Required time	9.4	The plant needs it to be able to run
Uptime	9.1	It is able to do its job, running or not
Operating time	9.3	Part of uptime: it runs as required
Standby time	9.5	Part of uptime: it is ready, has no work, and the plant needs it
Idle time	9.6	Part of uptime: it is ready, has no work, and the plant does not need it
External disabled time	9.20	Part of uptime: it lacks power, staff, or another outside resource, or stops for a planned action other than maintenance
Downtime	9.2	It is unable to do its job because of preventive maintenance or a fault
Preventive maintenance time	9.8	Part of downtime: preventive work and its delays
Corrective maintenance time	9.9	Part of downtime: corrective work and its delays

Maintenance time includes the delays around the work. Waiting for a part, a specialist, or information is logistic delay (9.13). Missing machine knowledge can show up here as waiting for the person who knows. Making the machine safe and preparing test instruments is technical delay (9.14). Delays for internal administrative reasons are the third kind (9.15).

Only diagnosis, hands-on work, and the final function check make up repair time (9.11). The standard defines a fourth delay, external administrative delay (9.16), such as waiting for permission to reach the machine. Annex D does not list it inside maintenance time.

Example

Nordwerk, a fictional plastics plant, requires 6,000 hours a year from each machine: three shifts, Monday to Friday, 50 weeks. Here is injection molding machine IMM-07 in 2025.

Time	Hours	Note
Required time	6,000
Uptime	5,919	All of it operating time
Downtime	81
Preventive maintenance time	36	Twelve monthly stops of 3 hours
Corrective maintenance time	45	Repair 27 hours, waiting 18 hours

The example counts no standby or external disabled hours, so uptime is operating time: 6,000 − 36 − 45 = 5,919 hours.

What counts as downtime, and what does not?

EN 13306 gives downtime two causes: preventive maintenance and faults. Anything else leaves the machine in uptime. A machine without power, staff, or compressed air is in external disabled time. The standard calls these outside things external resources and says their absence does not lower availability (4.7, 10.2). A failure is an event and a fault is a state; failure, fault, and breakdown explains the words.

Shop floors often use downtime for every stop. In our experience, that includes stops for missing material and for changeovers. Gulati's worked OEE example does the same for changeovers: it counts product setups, tooling changes, and operator checks as downtime beside repairs. EN 13306 sees operator changeovers differently. For maintenance purposes, it keeps production lost to a change of product or tools out of production based availability (4.10).

You hear	It means	It is not
Downtime, shop floor	Any stop of the machine, for any reason	Downtime in EN 13306
Downtime, EN 13306	Unable to work because of preventive maintenance or a fault	A stop for missing power, material, or orders
Uptime	Able to work, running or not	Only the hours it runs: that is operating time
Idle time	Ready, but not needed	A stop caused by a fault

How do MTTR, MTBF, and availability use these times?

MTTR in EN 13306 is the mean time to restoration. It averages each stop from the moment a failure happens to the moment the machine works again, so waiting counts. It leaves preventive stops out (9.21, 11.5). Mean repair time averages repair time only, without the delays (9.11, 11.4). Ramp-up after restoration is its own period and does not belong to time to restoration (Annex C).

For availability, the standard offers three time ratios (4.9). One counts preventive and corrective downtime. Another counts only the time to restoration after faults.

What should you record for each stop?

Record three times: when the machine stopped, when work started, and when it ran again. The first and last give time to restoration. The middle one splits the waiting from the repair. Without it, the waiting hides inside one number. Gulati observes that shop-floor records usually hold only the start of the failure and the return to service, so the total gets reported as MTTR.

We recommend you record the start of work too, because waiting that nobody records cannot be reduced. Types of maintenance explains the difference between preventive and corrective work.

Sources

EN 13306:2017, Maintenance: Maintenance terminology, CEN, 2017. Clauses 4.7, 4.9, 4.10, 6.4 to 6.8, 9.1 to 9.16, 9.20, 9.21, 10.2, 11.4, 11.5, Annex B Figure B.1, Annex C Figure C.1, and Annex D Figures D.1 and D.2. This page explains the standard in our own words; the standard is the authority. Buy it as DIN EN 13306:2018-02 from DIN Media.
Ramesh Gulati, Maintenance and Reliability Best Practices, 3rd ed., Industrial Press, 2021, chapter 6 (mean downtime and what a CMMS records) and chapter 7, Example 7.3 (downtime in an OEE calculation).