What’s the difference between idle time and downtime?

The SMRP distinguishes between idle time and downtime with these definitions:

  • Idle time is the time in which an asset is either waiting to run or isn’t scheduled to run.
  • Downtime is when the asset is incapable of running, either because of planned maintenance or an unplanned outage.

Idle time

Basically, the main factor for defining idle time is when there isn’t any actual demand for the asset. If you don’t have a piece of equipment scheduled to run, then it’s considered to be idle.

Likewise, when an asset is up and available, but not being used, that’s also considered idle time. For example, a discrete manufacturing floor where you make numerous different types of products might have certain assets sit idle while you perform processes that don’t use them.

Another example might be a fast food setting where your latte machine sits idle during evening hours. You don’t need it during that time, but it’s up and available in case you do.

Equipment downtime

As opposed to idle time, equipment downtime is any time when an asset is unavailable to run. Often, this occurs because you have preventive maintenance scheduled (proactive maintenance tends to compose about 70% of all maintenance tasks). In other cases, downtime results from an equipment failure.

In either case, you can’t use it while it’s down, often constituting a drop in productivity.

Why track the two separately?

Now, since both of these metrics represent times when your equipment isn’t running, why track them separately?

One reason is you might be able to take advantage of idle time. The best time to perform preventive maintenance is when your equipment isn’t scheduled to run. This way, idle time is put to good use while downtime is reduced. Just be sure to track that time spent performing those tasks—otherwise, if demand for the asset increases, you’ll have a clearer idea of how much time you’d need the asset offline.

Another reason is because idle time doesn’t really represent lost productivity. Downtime, on the other hand, does. When making decisions about how to improve equipment reliability, you’ll want to look at downtime without lumping it with idle time.