Does the Maintenance Frequency of Plant and Equipment depend on Equipment Criticality?

Your business exposure to operational risk drives your equipment risk reduction priority, risk reduction strategies, and risk reduction activities. You use Equipment Criticality Analysis to identify how big and how sensitive your operational risk is; should your business let an item of equipment fail.



Hi Mike.

Does the frequency of maintenance of a plant or equipment depend upon the criticality?


Hello Friend,

Equipment criticality indicates the importance, and subsequent priority, of a piece of plant to successfully meeting production requirements. Usually that means efficiently making top quality product in time to meet the delivery schedule. Equipment criticality indicates the risk to the operation should the equipment fail. This means that the highest criticality equipment is those items of plant that will stop production, or will cause a drop in product quality, or adversely impact the environment/safety or will waste serious amounts of money if they do not perform correctly.

In many peoples’ eyes sustaining production is the highest priority. They assume that as long as the plant is operating it must be profitable. To me it is more important to know if you are going to go out of business because equipment failures cost too much money. How much does the wastes and stoppages from equipment failure really cost you in lost money per unit time (minutes, hours)? Then base equipment criticality (its priority) on that rating. It maybe that a severely passing steam trap is of higher priority than a piece of production plant if the wasted steam costs the organisation more money than an equipment stoppage. But you will only know that once you know the true cost of failure for each equipment item in the plant.

The meaning of maintenance is changing. It is no longer only about repairing and sustaining the function of equipment. It now includes stewardship, or guiding the well-being of plant and equipment. If you want maximum reliability, availability and profitability from operating plant you need to steward it from conception through to death.

To answer your question: yes the equipment criticality affects the frequency of maintenance. If the organisation does not want its critical equipment to fail more often than its inherently designed reliability makes possible, then they need to assemble, install, operate and maintain it in correct ways that deliver the maximum reliability. In this case ‘maintenance’ is the stewardship mentioned above. To prevent failure you need to do ‘maintenance’ that keeps the equipment in top condition and reduces the likelihood of failure.

Hence your maintenance must focus on sustaining good condition within the equipment and also preventing risk-increasing problems. Base your critical equipment maintenance type (preventive, predictive, design-out, replacement) frequency not only on criticality, but also on achieving maximum reliability. Keep your critical equipment in their best condition and do whatever maintenance is necessary to do that. Do not skimp on this task. The money saved in failures prevented will pay for any additional risk-reducing maintenance many, many times over.

It is the same philosophy as used by the medical profession. To manage your health it is necessary, amongst other things, to eat a balanced diet and weigh yourself regularly. In this way you identify eating habits and foods that increase the risk to your health and you can act to stop having them before you get sick from being overweight. How often do you do the ‘maintenance’ of weighing yourself? You do it often enough to know what is going on. You do not do it as few times as possible because you have little time or money available, or when you visit the doctor because you are already sick. In your attempts to save time and money you may end up dead.

Your critical equipment ‘maintenance’ should be seen in the same light.


My best regards to you,

Mike Sondalini
Managing Director
Lifetime Reliability Solutions HQ


PS. If you require advice on industrial asset management, industrial equipment maintenance strategy, defect elimination and failure prevention or plant and equipment maintenance and reliability, please feel free to contact me by email at