The typical answer is that a maintenance engineer works on the short term while a reliability engineer works on the long term. But what do we mean by long and short term?
A better answer is that the maintenance engineer's job is to quickly return the equipment to an operational state, while the reliability engineer's job is to prevent failure, as per Reliabilityweb.com. This definition is far from ideal, as restoring the equipment to an operational state is typically the role of the technician. The maintenance engineer is involved, but they do much more than that.
Furthermore, reliability is not just about preventing failures. It is about anticipating and mitigating the consequences of future failures. Nowlan and Heap define failure as when equipment no longer does what its users want it to do. Reliability is also about looking at trends and changes in the operational context of the equipment and resolving potential problems before they reach a failed state.
I define the two roles as follows: the maintenance engineer focuses on solving the problem, while the reliability engineer focuses on solving the cause of the problem or potential problem so that in the future its consequences will be mitigated or eliminated.
Even this definition can leave much room for interpretation. In addition, some of the responsibilities are shared. A maintenance engineer will be involved in reliability activities, while a reliability engineer will perform activities that could be considered maintenance-related. Nevertheless, it is important to separate these roles and clearly define the responsibilities of each. To that end, I stand by my definition.
Let’s look at a few examples:
Example 1:
A pump often breaks down. Each time the problem occurs, the maintenance team identifies the problem as a failed pump and the technician repairs or replaces it. The maintenance engineer, based on a request from production, evaluates and selects a larger pump. They make the necessary calculations to ensure that the pump will not cavitate and that the motor drive is strong enough to meet the new demand. The larger pump fails less often than the previous pump, solving the problem or at least reducing its impact.
But why was the pump failing? When originally designed and installed, this system was reliable. What changed? That's where the reliability engineer comes in. Has the process changed? What about the fluid being pumped? Has our operating context changed? Have we changed the way we use the equipment? Are there any changes upstream or downstream of the pump?
The maintenance engineer is focused on the discipline (i.e., mechanical), while the reliability engineer is focused on the asset (i.e., the machine or production line). This is a fundamental distinction between the two roles.
Let me start by saying that BOTH are important, and one is not more important than the other. In this case, the larger pump solved the problem (frequent failures), and we may not need the reliability engineer's intervention. But maybe, we do. The pump problem may be just the tip of the iceberg. Other problems may appear on other assets because of the cause of this failure.
When considering the cause of the failure the reliability engineer looks at technical causes (process changes, component issues, etc.), human causes (new operator, etc.), and latent causes (training, standard operating procedures, etc.). The maintenance engineer is mostly focused on the technical causes.
Example 2:
There are excessive motor failures. Again, the technican changes the failed motor. The maintenance engineer may be involved in stocking strategies to ensure that we stock enough replacement motors to meet demand and may even be involved in selecting alternative motors, better suited to the application. This last part can be done by the reliability engineer and may involve the process engineer. The reliability engineer will review the failure history, interview the technicians and, if possible, have a few motors analyzed to understand the cause or causes of the failure. Based on the results, the reliability engineer may adjust the preventive maintenance program, develop work instructions, recommend changes to rewinding practices, recommend changes in the equipment setup, recommend changes in the training program, and even recommend changes in the way the equipment is operated.
In Conclusion:
A maintenance engineer provides technical assistance to the maintenance team and is often the single point of responsibility (SPA) for specialized knowledge areas such as high voltage, cranes, and regulatory requirements. He or she is usually involved in BOMs, especially when alternative parts are needed to solve problems with obsolete or hard-to-get parts. The maintenance engineer also approves changes that may impact equipment performance.
The goal of reliability is to reduce risk. Risk is the consequence X the probability. MTBF (mean time between failures) is the measure of frequency (probability).
A reliability engineer analyzes risk projections and spends much of their time developing strategies to mitigate these risks. They also participate in maximizing the effectiveness of the maintenance function by optimizing PMs, developing work instructions, and identifying changes to the equipment and/or the way it is operated and maintained to reduce that risk. The reliability engineer approves physical changes and helps identify or find replacements for problematic components that impact reliability. This latter task is typically performed in conjunction with the maintenance engineer.
Publisher's note: This work updates and builds on the foundational work created by one of my mentors, H. Paul Barringer here: https://reliabilityweb.com/articles/entry/re-vs-me
