A debate over air compressors on a shovel fleet revealed a fundamental difference between maintenance thinking and reliability thinking.
We’ve written previously about the distinction between a maintenance engineer and a reliability engineer. While the two roles work closely together, their focus is fundamentally different.
Very simply:
• Maintenance engineers focus on reducing Mean Time to Repair (MTTR) — restoring equipment to service as quickly as possible.
• Reliability engineers focus on increasing Mean Time Between Failures (MTBF) — preventing the failure from occurring in the first place.
This distinction is more important than many organizations realize. When companies combine both responsibilities into a single role without clear intent, the urgent nature of day-to-day maintenance often dominates. The result is that the “reliability engineer” spends most of their time helping maintenance execute repairs faster rather than eliminating the root causes of failure.
I remember the first time this distinction became clear early in my career.
At the time, I was working as a maintenance engineer alongside a reliability engineer. One of the bad actors he identified in our wire rope shovel fleet was a high frequency of air compressor failures. The machines used reciprocating (piston) compressors, and he proposed replacing them with rotary screw compressors.
From a maintenance perspective, I preferred the reciprocating compressors. Although they failed frequently, they were small and easy to replace. They could fit through the house man door, and with a picker truck our millwrights could complete the replacement in less than a shift.
The rotary screw compressors were significantly larger and could only be removed by lifting the roof off the shovel house with a crane. What had been a same-shift repair became a 2–3 day job. From a maintenance standpoint, that amount of downtime was difficult to accept.
The reliability engineer’s argument was straightforward: the screw compressors were significantly more reliable. If the expected life was long enough, replacements could be planned during the annual shutdown, when cranes were already on site and the house roof was frequently removed.
In my mind, I suspected he was right. But like many maintenance professionals, I couldn’t stop thinking about the consequences if it failed unexpectedly.
In the end, we decided to install the reliable screw compressor. It turned out to be the right call. Compressor failures dropped dramatically; from multiple failures per year to replacements roughly every other year.
The lesson isn’t that every organization must have separate maintenance and reliability engineers. Many companies are fortunate to have even one dedicated engineer supporting operations.
However, if those responsibilities are combined into a single role, it’s important that the engineer consciously balances both perspectives; solving today’s problems quickly while addressing the underlying causes that create tomorrow’s failures.
Maintenance keeps the plant running today.
Reliability ensures it runs tomorrow.
