Means of maintenance for electrical installations

Maintenance of electrical apparatus allows for improvement of reliability, increased lifespan and reduced allotted maintenance time. There are three modes of maintenance: reactive maintenance, preventive maintenance or predictive maintenance.

The difference between the three modes is mainly related to the time allotted to maintenance personnel and the diagnostic equipment available to detect anomalies.

Reactive maintenance consists in not performing maintenance until breakage/failure occurs. This method is very cost-effective in the short term but as soon as the equipment starts to age, its reliability becomes irregular, it requires important stock management, its efficiency is reduced, and its useful life is also reduced. This method is generally used for equipment that functions occasionally and for which the interruption has no effect on production.

Preventive maintenance promotes maintaining equipment following the manufacturer’s instructions to increase reliability, reduce costly breakage, reduce unplanned shutdowns, increase efficiency and prolong the equipment’s useful life. This method requires a lot of time from maintenance personnel. A lot of tasks are considered useless since there are no diagnostic tasks using measuring apparatuses to detect the presence of faults. This method is used for production schedules with planned shutdowns.

Predictive maintenance promotes an approach using signs of imminent failure (excessive vibrations, abnormal temperatures, degradation of lubrification) before performing maintenance. This method allows a reduction of allotted maintenance time, eliminates useless tasks, increases reliability, reduces costly breakages, reduces unplanned shutdowns, reduces required stocks, optimizes the function of apparatuses, increases the efficiency and prolongs the useful life of the equipment. However, this method requires costly diagnostic equipment, training personnel with the diagnostic tools and is not cost-effective in the short term. This method is used for continuous production schedules without the possibility of interruptions.

In the three previous paragraphs, the three types of maintenance were explained. It can happen that a combination of methods is needed to adapt maintenance to the equipment present or to the companies’ values. Conditional maintenance modes therefore exist. Among these, two methods will be explained: maintenance based on reliability and based on risk.

Maintenance based on reliability evaluates the probability that failure will occur and has the objective of improving reliability while maximizing profitability. It uses predictive maintenance but incorporates reactive maintenance for low cost maintenance that doesn’t have significant impacts on overall reliability. It is mainly used for businesses with lesser financial means and limited personnel. They still want to improve reliability while lowering costs but want to do so while targeting critical components in need of maintenance. This method provides a happy medium between reliability and cost-effectiveness. However, the initial cost is high.

Maintenance based on risk allows classification of the probability that failure will occur in order of priority. The method uses reactive, preventive and predictive maintenance. It therefore allows optimization of resources in a cost-effective way, eliminates useless maintenance, prioritizes maintenance by importance and verifies the risks related to using equipment until its end of life. However, this method requires special expertise to quantify risk according to its gravity, probability and consequences.

Source: CSA Z463-13: Guideline on maintenance of electrical systems

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