How to increase machine reliability with predictive maintenance activities?

Is it possible to increase machine reliability with predictive maintenance activities? Adequate predictive maintenance makes it possible to achieve the correct operation of machines and installations, which translates into a reduction in downtime and, of course, an increase in reliability.

It was in the late 1940s that the quantitative concept of the reliability of a device was introduced, still valid today, as the probability that the device will adequately perform its intended function over time when operating in the environment for which it was designed.

In addition, the established definition of reliability includes other aspects such as:

• Proper functioning. Formally, the operation of a device is considered adequate if the intended function of the device is achieved. Generally, this function will be expressed in units corresponding to certain physical variables that define its operating process (power, speed, pressure, frigories, etc.) or in terms of the units of product to be produced (screws, cars, paper, etc.).
• Time period. Once the criteria for successful performance have been defined, the period of time during which the device is required to function continuously and properly should be established. This period of time is often referred to as mission time.
• Operating environment. The last aspect, operating environment, is also essential to give meaning to the concept of reliability of a device in this context, since equipment is designed to function in a certain way and under certain conditions. These include environmental conditions (temperature, pressure, humidity, radiation, acoustic noise, etc.) and operating conditions (electrical voltage and current, vibration, acceleration, etc.). 

During the operation of the devices, they may operate under conditions different from those envisaged in their design or suffer unforeseen stresses, either one-off or on a more permanent basis, which undermine their intrinsic resistance to failure and may lead to their failure.

The consideration of reliability, as a basic operational characteristic of equipment and systems, is increasingly evident in today's industrial environment, being a fundamental characteristic for non-repairable devices or devices with a continuous operating regime and very important for repairable devices or devices with an intermittent operating regime.

From a purely economic point of view, high reliability of devices reduces the overall costs associated with their operation. It should be borne in mind that the unexpected failure of a component can lead to the loss of the functionality of the system or installation of which it forms part and result in a significant loss of production with the consequent economic damage, which is normally greater the lower the repair capacity of the failed device or the higher the economic value of the unmet demand.

Predictive and preventive maintenance operations ensure machine availability by reducing unexpected breakdowns through the analysis of failure symptoms using various techniques: 

• Machinery inspections.
• Performance measurement.
• Lubricant analysis.
• Vibration analysis.
• Axle alignment.
• Non-destructive testing: X-ray, ultrasound, thermography. 
• Analysis of current in electrical machines. 

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