When senior management’s eyes turn to the shop floor in search of ways to push through more production and squeeze out further savings, maintenance management should be prepared to respond.
The maintenance department has many tools at its disposal for improving the return on company assets, including Lean Maintenance, better use of computerized maintenance management systems (CMMS), and a host of three-letter acronyms such as total productive maintenance (TPM), reliability-centered maintenance (RCM) and root cause analysis (RCA).
One area of greatest potential for companies with extensive capital assets is to integrate these tools with condition monitoring of critical assets. Efforts to tighten communications of condition-monitoring instrumentation and data analysis software with CMMS and automation infrastructure, combined with the proliferation of wireless sensor systems and the drive to reduce manpower skill and time requirements, are bringing implementation costs down and drawing much attention to this approach.
But the considerable investment necessary to purchase and implement these technologies isn’t always cost-effective. Is it time you started, broadened or automated your foray into condition-based maintenance (CBM)? Here are seven steps to determine whether and how to proceed with a CBM program:
Step 1: Understand your options
Although CBM might seem like the answer to all your problems, unfortunately, it’s not that easy. In many cases, CBM isn’t necessary because the consequences of a run-to-failure approach are so minimal. For example, most people change the light bulbs when they fail because monitoring the filament resistance of every bulb in your plant is a much more costly alternative. Similarly, you wouldn’t send oil samples from your car engine to be analyzed in a lab on a regular basis (i.e., condition based maintenance), because simply changing the oil every 7,500 miles is more economical.
So there are three alternative approaches:
- Failure-based maintenance (FBM): An asset is run until it fails, at which point it’s repaired or replaced. Depending on the asset, this approach can be hugely economical (e.g., light bulbs), or highly expensive or even life-threatening (e.g., large rotating equipment).
- Use-based maintenance (UBM): An asset is maintained on a periodic or metered basis such as every three months or 10,000 gallons of use. In some cases, this is a more economical approach than FBM, i.e., when the consequences or cost of running equipment to failure are higher than the cost of the UBM program.
- Condition-based maintenance (CBM): Triggers are established that correlate to impending equipment degradation or failure. When these conditions are identified through periodic inspections, defensive actions are taken, such as repair or replacement of a part, to pre-empt the failure just in time (Figure 1).
Knowing when to use FBM, UBM and CBM is a matter of understanding the costs, benefits and risks associated with each approach. Every component of each piece of equipment must be examined individually and as an integrated system to determine the consequences of each possible type of failure and the cost/benefit of each maintenance approach to deal with that failure. This can be a lot of work for most companies with hundreds if not thousands of systems, assets and their individual components, which may explain why many if not most companies have defaulted to a firefighting mentality that favors the FBM approach.
Step 2: Maintenance strategy - the big picture
Before diving into the murky waters of establishing a CBM program, it’s important to stand back and develop a proper context, sense of priority and justification for the expense associated with condition-based monitoring. By developing a maintenance strategy, you’ll set longer-term goals, objectives, performance measures and targets, and action items for achieving your targets. The maintenance strategy provides the big picture of everything that needs to be in place to meet your organization’s needs, which ensures that the CBM program has the greatest probability of success.
For example, perhaps certain regulatory pressures or a pressing HR issue such as high maintainer turnover need to be addressed immediately. If these issues aren’t addressed before implementing a CBM program, then there may be a much higher risk of failure. The maintenance strategy ensures that competing and complementary priorities are understood, and action items properly integrated.
Step 3: Focus on your critical assets
Once a maintenance strategy has been developed, and assuming CBM was identified as a priority, the next step is to identify your critical assets. Conducting a criticality analysis of your systems, equipment and components avoids the overwhelming workload of determining the best maintenance approach for each and every asset. A critical asset can be defined as one for which a failure would cause catastrophic consequences, such as:
- A key bottleneck in the process (e.g., if this asset is down the entire line will be down)
- A severe health and safety-related failure (e.g., failure of this component may cause an explosion that would threaten human life)
- A costly customer impact (e.g., if we can’t manufacture a certain product on this asset, we can’t deliver on time, and we stand to lose our largest customer)
- An expensive and time-consuming repair (e.g., a long period of production downtime required to repair, expensive replacement parts difficult to source, highly specialized external skills required)
Sensitivity analysis can determine which assets are more sensitive to failure, for example, asking, “What is one minute of uptime worth in terms of marginal revenue and maintenance cost avoidance?” Many CMMS packages have analysis tools that can help pinpoint critical assets and components, at least in terms of historical maintenance costs for each asset. If technicians have been using problem, cause and action codes accurately and in sufficient detail, then even more useful data is available to determine, say, the top 10 most costly root causes for every asset in the plant.