The advancement in Industry 4.0 technologies can already be noticed in several business segments and is bringing along production gains, cost reductions and improvement in the safety of operational processes.
In industrial maintenance, however, some technological tools have been used for several years, with the aim of improving maintenance processes and increasing equipment availability.
Technologies such as vibration analysis, thermography, ultrasound, videoscopy, analysis of electrical quantities are already reality in industries with well-established maintenance processes. It is not uncommon, however, for maintenance managers to use different techniques for each type of equipment, respecting their level of criticalness and impact in case of failures.
Each type of maintenance is applied based on cost considerations — tool acquisition, deployment, training and maintenance of the equipment itself — and benefits of each option — such as reduction of MTTR (Mean Time To Repair), increase of MTBF (Mean Time Between Failures), increase of availability and OEE (Overall Equipment Effectiveness).
In this assessment, the following types of maintenance are considered:
Corrective maintenance is the most basic type of maintenance, occurring when there is an equipment breakdown or failure and its consequent unavailability. From there, the maintenance of the equipment is carried out and it can return to normal operation.
The costs of corrective maintenance can vary greatly. The cost of implementation can be relatively low, as there is no need to acquire special tools or training, nor are there costs for inspection hours.
However, especially when it comes to critical and higher-powered equipment, the cost of corrective maintenance can be extremely high. In this account, costs for parts and components, tools, man-hours for performing repairs and testing, as well as costs for recommissionings and start-ups and, especially, unavailability of the production line should be considered.
Even more critically, the failure of an equipment can lead to more serious issues, damaging property or the environment and compromising the safety of the operation and its people.
Therefore, corrective maintenance should be used when preventive or predictive maintenance in equipments is unfeasible.
This unfeasibility may be related to the cost of implementation and impact of the failure, considering repair costs, operational and environmental and occupational safety risks already mentioned.
Thus, corrective maintenance is recommended, for example, for equipment with a low degree of criticality, small motors, pumps, compressors, pipelines, computerized systems or equipment that perform auxiliary and low-impact functions when unavailable and yet does not pose risks to safety or the environment.
Preventive maintenance is carried out through periodic actions. It aims to avoid equipment failure, avoiding high maintenance costs and especially unavailability of production lines.
Generally, information from the equipment manufacturers is taken into account, along with the experience of the industrial engineering and maintenance team, to make preventive maintenance plans more accurate for each use case and application.
Predictive maintenance can cover different actions on many types of equipment. The most common are:
- Replacement of components such as seals, bearings, belts, fasteners and gaskets;
- One-time services such as lubrication (replacement or maintenance of lubricant), cleaning of systems etc.;
- Overhaul services such as overhaul of large engines — including windings insulation measurement, changes of all wear parts, winding replacement, lubricants, rotating assembly balancing, starting and load testing and alignment.
Although preventive action plans generally follow manufacturers’ recommendations, many industries conduct annual or biannual stops for general preventive maintenance, in which services for most of the equipment are performed. This is a common scenario in continuous process industries with closely interconnected systems, where stopping a piece equipment can mean stopping the entire process or plant. Some examples are sugar and alcohol, chemical and paper and cellulose industries.
Preventive maintenance costs can also vary greatly. The highest costs in this type of maintenance are associated with labor (man-hours) and equipment parts and components.
Preventive maintenance also requires very assertive planning, since large pieces of equipment can have rare or special parts, items that are usually not kept in stock and are often imported.
Other points to consider are that, sometimes, items are replaced without need, other times, the replacement plan of a certain part may take too long for a certain amount use and the failure occurs between preventive periods. In addition, the same equipment can suffer failures of the same part with different intervals, varying according to operating conditions (load/environment/application).
Carrying out maintenance ahead of time can mean raising the cost of parts and labor unnecessarily. On the other hand, performing maintenance after the right time can lead to equipment failure and stops in the production line, as well as corrective maintenance.
Predictive maintenance consists of using machine condition monitoring to evaluate possible maintenance interventions as assertively as possible. With this, the goal is to anticipate possible problems, plan maintenance actions and perform those actions at the exact moment of need.
Sensor-based technologies are required to perform predictive maintenance. The most common are:
- Vibration sensors — Velocity [mm/s] or acceleration [Gs] with spectral analysis;
- Non-contact radial and axial displacement sensors (proximeters);
- Temperature sensors (bearings and frame);
- Thermal cameras;
- Electric current sensors with spectral analysis;
- Partial discharge sensors in electric motors;
- Pressure sensors for compressors;
- Linear expansion sensors for turbines.
From the reading of these sensors, it is possible to extract valuable data on the operation of the equipment. Techniques such as vibration analysis allow us to understand what is the defect being developed in the equipment — such as bearings, gears, unbalance, misalignments of shafts and pulleys, clearances, lubrication, among others. To know a little more about how this technique works, you can access our article on vibration analysis.
There are different ways to obtain data from equipment for predictive maintenance. One of them is route-based predictive maintenance, in which analysts visit equipment locations and collect data with portable devices, such as vibration analyzers with sensors, thermal imaging cameras, ultrasound equipment, among others. Another technique is online predictive maintenance, in which sensors are permanently installed on equipment and constantly send data to computerized systems.
If you want to learn more about the different predictive maintenance techniques and concepts of predictive 4.0, visit our predictive maintenance article HERE.
In this article we discussed the different techniques of industrial maintenance. As seen, there is no definitive technique for all types of equipment and industrial scenarios, the techniques are complimentary. Several factors should be observed, being the main cost of implementing the techniques, qualification of personnel, risks to labor safety and the environment and criticality for production.
Venturus is an Institute of Science and technology with a robust structure for the development technology projects. We work in the areas of IIoT, custom software development, data Science, artificial intelligence, computer vision, cyber security and cloud architectures.
To learn more, get in contact with us and chat directly with our industrial solutions experts.