Most machines give some indication that a potential component failure is about to occur that will lead to a functional failure. Our goal should be to identify, monitor and correct components that are failing before they create a functional failure that will prevent the machine from performing as intended. Condition monitoring (CM) is the primary tool used for this process. For example, a bearing defect is an example of a potential failure. The bearing would be monitored for degradation and replaced before it completely fails, preventing the machine from performing its intended function (functional failure).
It could be argued that God created the first condition monitoring instrument when he created man. Our main senses are touch, sound, sight, taste and smell. Additionally, humans have other senses that can detect balance, heat, pain, etc. All of these senses can provide very valuable data about the environment around us and the equipment we work with each day. Therefore, the human being is the first CM instrument to be used—versatile in application and proven to be a very beneficial tool.
Every employee is a condition monitoring tool that can provide tremendous value to your reliability efforts. Operators and maintenance employees should be trained and encouraged to use their natural senses to look for potential failures on the equipment placed in their care. CM analysts also should conduct visual inspections of the equipment they monitor during their routine data collection activities. A means to document these findings should be provided to each employee so corrective action can be taken in a timely manner. This can provide a very cost-effective method for identifying potential failures before they occur, thereby avoiding the costly consequences.
Some facilities do not use their employees’ natural senses at all. Other facilities seem to rely too much on human senses as their primary or only means of condition monitoring. The human senses have very specific limitations in their use. We can only “see” certain wavelengths of light, “hear” a certain range of sound (frequencies), “smell” certain odors, “feel” certain sensations, etc. Each of these senses tends to deteriorate over time as we grow older. If we do not sense something, it does not mean that nothing is there or that something hasn’t changed in condition. The human senses can be influenced by our surroundings, state of mind and time allowed to complete the inspection. Moreover, the perception of a condition can vary from individual to individual. Severity of the detected problem can be difficult to determine as well. Standards are difficult to incorporate due to inconsistencies between individuals. Reporting any problems found can be problematic as well. Therefore, it is essential to use these tools within their natural confines.
Figure 1: Monitoring interval. Figure courtesy of Ludeca, Inc.
The P-F curve is a function for identifying when a potential failure starts, progresses to a point of detection (P) and finally reaches a point of functional failure (F). The earlier a problem is detected, the fewer the inspection intervals required and more time is available to take corrective action. The goal of a reliability effort should be to detect the failure as early as possible so corrective action can be planned, scheduled and executed before a functional failure occurs in the machine. This is where one of the main disadvantages of using the human senses as a condition monitoring tool is realized. Our human senses are only capable of detecting a problem (P) when it is rather close to the point of functional failure (F). This requires more frequent inspection intervals to detect the problem and provides less time to respond to a detected problem to prevent the unwanted consequences. A lot of failures are undetectable by the human senses. This results in defects that will unavoidably lead to functional failures if not detected by other means. Equipment downtime, reduced production capacity, safety issues, environmental concerns and additional costs are often experienced as a result of these failures from undetected defects.
Again, the goal should be to identify problems as close to their inception point as possible. Doing this requires detecting smaller conditional changes in the components of concern. This requires detection capabilities that go beyond what the human senses are able to sense. Technologies, such as vibration analysis, electrical testing, temperature and thermography, ultrasonic monitoring, lubrication analysis and other non-destructive testing (NDT) methodologies, have been developed and refined to provide the necessary detection sensitivity required to monitor the conditional changes of equipment.
This collection of technology, methods and procedures is known collectively as condition monitoring. CM itself is at the core of a reliability centered maintenance (RCM) approach. Most CM technologies are an extension of our human senses. However, if applied correctly, they allow us to detect point P (a deleterious change in condition) very close to the point of initial change. This is very important because it allows additional time to identify, mitigate and avoid the unwanted consequences.
On-condition maintenance activities (human senses or technology) should not be deployed in an arbitrary way. Careful consideration must be given to their limitations, selection, application, management, reporting, etc. If done correctly, the results can lead to better equipment reliability, improved quality, increased capacity, reduced costs, reduced risks and improved profits. Some companies decide not to employ the modern technologies described above and are subject to the negative financial risks that result. Other companies utilize these technologies in an ineffective way and do not realize the reliability gains and resulting positive financial results they seek. Some of the common mistakes made when implementing a CM program are:
- Improper technology selection;
- Improper technology application;
- Not applying the technology to the proper equipment;
- Having unrealistic expectations;
- Providing insufficient training to employees;
- Not utilizing available “technology experts” (vendors, consultants, etc.) to gain implementation and deployment support;
- Inadequate support from management;
- Not creating a sufficient level of awareness of the value these technologies can provide;
- Missing or inadequate standards (reporting, analysis, etc.);
- Not having a continual improvement plan;
- Improper monitoring frequency (based upon haphazard intervals or not on the P-F interval);
- Not implementing the recommendations that result from the CM activity;
- Not selecting the right individuals to utilize the CM technology;
- Only applying CM efforts part time.
Each of these common mistakes have individual aspects that should be known and avoided for a successful condition monitoring program.
Most companies are constantly seeking increased capacity, lower product costs, less risk (financial, safety, environmental), improved profits, etc. These goals are not of much value unless they are achieved reliably and sustainably. In many companies, management does not view maintenance reliability efforts as value-added functions. Instead, maintenance reliability efforts are viewed as a cost! These efforts should be viewed as value-added investments that are critical to the success of the company. On-condition maintenance activities, such as visual inspections, vibration monitoring, ultrasonics, thermography, electrical testing, etc., can help achieve reliability and sustainability in these goals.
Unfortunately, statistics show that most condition monitoring and reliability efforts fail. The reasons for failure are many and a few are outlined in this article. The question within your organization should not be, “Do we apply or not apply condition monitoring?,” but rather, “Are we applying the correct mixture (visual inspections and technology based)?” Other questions that should be asked are: Is proper support being provided to ensure success? Are these efforts being focused on the correct equipment? Are the results of our CM efforts being reported correctly? Are the recommendations of these activities being implemented before functional failures occur? and Are these activities being used to eliminate root causes of equipment failures? If the answer to these questions is “yes,” you will find that your business goals become much more attainable and less costly.
Trent Phillips is the Condition Monitoring Manager of LUDECA Inc., a leading provider of shaft alignment, vibration analysis and balancing equipment. He has worked for many years creating and managing reliability programs and in the development of condition monitoring technologies. Trent has several certifications in condition monitoring technologies. www.ludeca.com