Maintenance policies applied correctly aimed at preventing and/or eliminating the occurrence of failures. Lack of fulfillment of what was previously defined as "proper performance" is defined as failure. According to Kardec (2002), fault is "an abnormal physical state in a system that is a threat to the operation thereof”. “Abnormal” is defined as the deviation of some measurable parameter beyond the limits considered desirable for the normal operation
For Smith (2004), maintenance aims to "preserve the functional capabilities of equipment and systems in operation". According to Moubray (2000), the purpose of maintenance is to "ensure that physical assets continue to do what the users want them to do”.
SAE JA1011 states that maintenance should ensure that "physical assets continue to perform their planned functions”.
The maintenance really only fulfils its role when it comes before and can predict possible events that can paralyze and damage production, with consequent loss of volume, increased of operation expenses and reduction of the business margins.
To achieve what it is called World Class Maintenance (WCM), it is necessary to improve adopted maintenance processes
According to Kardec (2002), plants coexist with certain types of maintenance (or maintenance policies) and progress of organization's management will allow the application of the most convenient such as corrective, preventive, predictive and maintenance engineering
Various tools available today have adopted the word maintenance. It is important to note that these are not new types of maintenance but tools that allow the application of the main types of maintenance mentioned above. Highlighted among them are: Maintenance Engineering; Lean Maintenance; Total Productive Maintenance; Reliability Centered Maintenance; Reliability Based Maintenance and Condition Based Maintenance