The thermal-processing industry is much more than asset-intensive. The majority of the equipment is critical in ensuring employee safety, temperature uniformity and final product specifications. Unexpected failures can have extreme regulatory and financial consequences, reducing business competitiveness, productivity and efficiency.

A proper maintenance strategy allows businesses to improve equipment uptime and reduce maintenance costs. However, achieving these goals requires understanding how and when to apply your maintenance efforts.

This article will compare three of the most common maintenance strategies and highlight the advantages and disadvantages of each.

Reactive Maintenance

Reactive maintenance is a strategy of only intervening with equipment when it performs below acceptable levels or ceases to operate altogether. This is some businesses’ de facto mode of maintenance. However, this method has more drawbacks than benefits.

In the heat-treatment industry, it’s unlikely to find equipment on reactive maintenance if it’s central to the process. Too much is at stake from a financial and safety perspective. It’s more common to reactively maintain generic facility equipment due to redundant circuits or highly visible but non-critical failure modes.

Advantages

• Reduced maintenance staff. With reactive maintenance, there are no ongoing planned maintenance interventions, so maintenance staff numbers are minimal.
• Requires little to no planning. In effect, the business has abdicated responsibility, handing the decision making to the asset. It will decide when maintenance will occur by ceasing to operate.
• Few implementation costs. Apart from some basic tooling, capital expenditure is minimal on the front end.

Disadvantages

• Inconvenient stoppages. There are few indications of when the equipment will no longer operate correctly. If a critical component in a heat-treatment process fails, the cost of rework and lost capacity can be considerable.
• Extended downtime. When an asset fails under reactive maintenance, troubleshooting often takes a long time. Additionally, it takes extra time to assemble the people, tools and spare parts necessary for the repairs. This often happens at inconvenient hours.
• Expensive emergency repairs. Breakdowns are unpredictable, and they don’t respect late hours or holidays. Emergency callouts, expedited spares and last-minute equipment hires drive up the costs of emergency repairs.
• Shorter asset life. The point of maintenance is to detect deterioration early and rectify it at a minimal cost. Allowing a component to deteriorate to the point of failure often means the component is beyond economic repair, and it can create secondary damage, shortening the asset life.
• Potential safety hazards. When equipment with high energy or hot liquids fails, it can do so catastrophically, posing a threat to operators or employees.

Reactive maintenance best suits assets whose failure will not impact safety, health or the quality and efficiency of operations. It’s an acceptable approach for no-critical assets or those with very high mean time between failures, low capitalization and short lifespans.

Preventive Maintenance

Preventive maintenance is a process of regular inspections and component replacements based on machine operating time or cycles, calendar time or condition. It aims to identify and rectify deterioration before it impacts production by carrying out corrective maintenance actions.

A vacuum furnace used in heat treatment is a good example of an asset eligible for a preventive-maintenance strategy. Regular leak checks ensure optimal product quality during the heat-treatment process, while inspections for deterioration ensure operator safety.

Advantages

• Greater production capacity. Fewer unplanned breakdowns and stoppages increase equipment availability, optimizing the machine’s productive capacity.
• Improved asset life. Equipment is more likely to achieve its lifespan if small, regular maintenance interventions keep operation at an acceptable level rather than suffer infrequent (but potentially catastrophic) failure.
• Safer operation. Identifying and addressing component wear or weakness before it becomes problematic reduces the potential for failure and promotes a safer workplace.
• Fewer emergency maintenance costs. We’ve seen reactive maintenance cost from three to 10 times more than a preventive approach. A business can avoid the premium applied to last-minute emergency repairs by preventing breakdowns.

Disadvantages

• Requires more maintenance resources. Preventive maintenance emphasizes regular inspections, requiring more technicians on staff or more visits from external contractors, increasing operating costs.
• Increased capital costs. If you have an in-house maintenance program and teams of technicians, you’ll need to purchase tooling and spares to minimize delays during maintenance shut-downs, which ties up capital.
• Possible over-maintenance. If your maintenance program is not optimized, you may be spending money on unwarranted inspections or inspection frequencies for no financial benefit.
• No guarantees. Preventive maintenance is not a panacea. While correctly applied preventive maintenance will reduce equipment failure and deterioration, some failures are unrelated to asset age and may occur regardless.

Preventive maintenance forms the majority of maintenance in most organizations and is ideal for assets where: breakdowns are inconvenient but not financially or safety-critical; operations allow the planning of regular maintenance downtime; failure modes are generally well understood; and engineers can devise suitable inspections or tasks to mitigate deterioration

Predictive Maintenance

Predictive maintenance uses sensors and analytics to monitor the condition of operating equipment in real time and identify when deterioration is likely to occur. This allows for early and planned maintenance intervention – before issues hinder operations.

For example, predictive maintenance can help assess cathode loss in electron-beam welding equipment. The predictive algorithm will monitor wear and guide storage and purchase decisions to optimize welding economics.

Advantages

• An increased planning window for maintenance. You can source and plan resources while ensuring timely and efficient intervention before production output is affected.
• Reduces ongoing maintenance costs. Rather than carry out regular preventive maintenance, the equipment will operate without intervention until the predictive software suggests attention is required.
• Increased asset life. Predictive maintenance reduces unnecessary maintenance interventions and breakdowns, while early targeted maintenance increases asset lifespan.
• Improved safety. Equipment failure and ongoing maintenance actions introduce the potential for safety issues. Predictive maintenance strategies reduce both.
• Improved equipment availability. Stoppages due to failure or planned maintenance shutdowns increase equipment downtime. Predictive maintenance reduces the occurrence of both, improving equipment availability.
• Digitalization opportunities. The hardware and software installations that support predictive maintenance also support other maintenance and operational technologies, equipping connected workers with mobile devices, wearable technology and augmented or virtual reality. Implementing predictive maintenance can be the precursor to wider organizational digitalization.

Disadvantages

• High upfront costs of implementation. Introducing predictive maintenance for your equipment requires investment in sensors, Wi-Fi networks, cloud computing and machine-learning analytics. The costs are not inconsiderable but are rapidly recovered from improved uptime and lower maintenance costs.
• Time to value, expert knowledge and complexity. Installing the hardware and software is costly and often complex. Identifying what to monitor and training the system to recognize when deterioration occurs takes time and expert knowledge.

Because of the upfront cost, time and complexity involved in implementing predictive maintenance, you should reserve it for assets where sudden failure would impose unacceptable consequences. The aerospace industry, for instance, uses predictive maintenance to avoid severe regulatory, environmental and safety events.

Conclusion

An optimal maintenance program is contextual, requiring analysis of the unique characteristics of each business. The usual result is a hybrid system using reactive maintenance for non-core operations while using preventive and predictive maintenance for processes where stability and end-product specification compliance are essential. The result should be an optimal mix of strategies minimizing maintenance costs, maximizing equipment availability and mitigating critical safety and product compliance risks.

With the industrial heating industry facing increased competitive pressures, plant managers must understand the advantages and disadvantages of common maintenance strategies to ensure product quality, improve efficiency and reduce costs.

After an extensive career as a reliability and business improvement consultant, Eric joined L2L, where he currently serves as the Director of Smart Manufacturing. He can be reached at editor@leading2lean.com.