In the world of reliability, an increasing number of people are realizing the benefits of predictive and proactive maintenance strategies. Condition monitoring, the primary activity of these strategies, identifies either the root causes or the symptoms of adverse machine conditions. An effective proactive/predictive maintenance program requires tools such as vibration, thermography and oil analysis to scan, inspect and determine the condition of machinery. Do not, however, underestimate the value of other high-tech instruments - your own senses. That's right, your eyes, ears and nose can be valuable condition monitoring tools and unlike other instruments, require little training to be utilized effectively.
While some visual or audible observations require interpretation, many are intuitive and only require a system to manage and act on the information. Most operators and technicians are familiar with the machinery they maintain or operate, and consequently are aware of the "normal" sounds of that machine, making them qualified to identify unusual conditions.
Many sensory inspections are visual, and checking oil levels is the most common visual monitoring activity. Numerous potential machine failures are prevented by an attentive individual who notices a low or nonexistent oil level. Other valuable functions can also be performed as part of the visual inspection. Lubricant issues such as oil contaminated with water or other materials, badly degraded or oxidized oil, and excessive foaming, as well as other machine conditions including excessive vibration, loose belts, loose drive chains and loose or missing fasteners are all examples of what should be routinely documented and scheduled procedures. This should serve as the foundation of a condition monitoring program, no matter how sophisticated.
Another category of sensory inspection is auditory inspections. In some instances, sound can be a more sensitive monitoring tool than visual inspections. While visual inspections are fairly straightforward, audible inspections may require some degree of experience or training to interpret. However, it is likely that even the untrained or inexperienced ear will notice a change from the normal sound and can report the condition, even if a problem is not identified.
Another inspection method or sense that may not have been considered is smell. The human sense of smell is powerful and can be used to identify various adverse machine conditions and lubricant problems. Among the common lubricant issues detectible by smell are certain types of contamination such as solvents, fuel, refrigerants and other process chemicals. Additionally, oil that has become significantly oxidized has a distinct odor that once observed, is easily identifiable. Some machine conditions are also detectible by smell. Slipping belts or overheated components will often present an alarming smell that demands investigation.
The Human Senses: A Valuable Condition Monitoring Technique
As a designer of lubrication programs, I am always eager to find efficiencies in every activity, and sensory inspections provide ample opportunity for efficiency. I personally believe one of the best features of this sort of activity is that these tasks can be performed in conjunction with other maintenance tasks. Any activity that brings technicians into close proximity with the machine is a perfect opportunity to perform a routine sensory inspection. I am often surprised when I visit a facility and notice easily observable problems that could lead to a catastrophic failure - problems which would otherwise go unnoticed. What is more common, and more of a concern is the number of these items that are observed and go unreported, or are reported but not acted upon. This is typically not a case of apathy, but rather the lack of a mechanism or process to capture and utilize the data. Therefore, it is important to document and schedule these otherwise simple tasks and create a checklist and reporting mechanism with defined follow-up actions to address the identified problems.
One last benefit of this type of condition monitoring is that most anyone can do it. The effective use of other tools, such as vibration or oil analysis, requires a considerable amount of training. Sensory inspection, on the other hand, can be performed by nonmaintenance personnel such as operators. This can be an advantage when the maintenance staff is occupied with performing reactive maintenance tasks. After all, if time is available in the operator's schedule, why not use him to perform this type of task? Something as simple as detecting an oil leak or a gearbox that sounds weird could and often does lead to the prevention of a catastrophic failure, avoiding tens of thousands of dollars in losses. While most of us perform routine inspection to some extent, the value of utilizing the senses should not be underestimated or overlooked.