For lubricants, water is the second most destructive pollutant, after the particles. It causes problems such as rust and decreased load bearing capacity (film resistance) in the oils and also leads to a permanent degradation of the oils. Similar to oxidation, hydrolysis is the degradation of the molecules of the lubricating base by the effect of water. But not only the lubricant base is prey to this process, the additives are also susceptible to degrade by the effect of hydrolysis.
Translated by Roberto Trujillo Corona,
Critical machinery should definitely be inspected more frequently than non-critical machinery. Based on the definition of «critical», we mean machines with the highest level of importance to you, your company and your process. These assets deserve the attention of their limited time, money and effort.
Of course, it is important to know how to define an asset as critical. There are many approaches to determining the criticality of an asset. Some plants choose to employ a simple 5-degree scale and assign numbers subjectively, while others use long, endless processes and even hire consulting firms to help them determine it. However, the decision can be reduced to a few key attributes:
Impact on production
Impact on safety
Impact on the environment
Availability of spare parts or redundancy
Probability of failure
Historical data about reliability and preventive maintenance
Most plants are very limited in terms of labor force and financial resources. If you have few of those resources in your «bank», you should spend them wisely. In order to make an informed decision on how to spend them, you need to have a good knowledge of the criticality of some assets relative to others.
These criticalities can also be used to help you prioritize work. With limited resources, you always seek to work first on tasks with the highest priority. This classification of work is almost impossible if one does not understand the criticality of the machinery.
Oil sampling is a good example of the use of criticality for decision making. Any asset that has a high impact on production, safety and the environment, which is more costly to replace, has little or no spare or redundancy, together with a high probability of failure and with low reliability and preventive maintenance, Would be an excellent candidate for continuous online monitoring in real time.
As asset attributes become less and less severe, the sampling frequency is relaxed, shifting from continuous monitoring to perhaps hourly, daily, monthly, quarterly, or yearly. You may even get to the point of deciding that the oil analysis simply offers no benefit because the machine has little or no impact on production, safety or the environment. It could be cheaper to replace it, or you could easily dispose of the spare parts.
Criticality is a very important element in making informed decisions about programming, whether it is a simple peephole inspection or as complex as repairing a turbine.