This is Part 1 of a two-part series on the use of infrared thermographic surveys in predictive and preventive maintenance programs. Part 2 (http://www.plantservices.com/articles/2009/125.html )explains ways to reduce data errors in IR surveys.
The use of infrared (IR) cameras in preventive and predictive maintenance (PPM) is well established. These cameras produce thermographic images and capture the temperature measurements that provide an early warning of potential equipment failures and unsafe working conditions. In some applications they’re used in stationary installations to record critical equipment images and temperature data automatically. However, most PPM programs involve an operator conducting an equipment survey manually on a standard schedule. Most mechanical, electrical, hydraulic and pneumatic equipment will benefit from their use in a PPM program.
Infrared surveys are particularly important for electrical equipment because it’s usually critical to an enterprise’s mission. Moreover, certain kinds of electrical failures pose life-threatening risks to workers.
Importance of a standard schedule
The IR survey frequency and scheduling often are overlooked as a standard operating procedure. Most infrared thermographers consider a standard schedule to be a generally accepted best practice. Nevertheless, plant thermographers often perform other tasks, dealing with emergency situations and unforeseen breakdowns. This often results in the IR survey schedule being viewed as optional. Such a view is understandable because IR trend data is collected over a relative long period of time, whereas equipment breakdowns and other crises must be handled immediately.
Still, skipping an IR survey can lead to equipment problems that produce their own crises, which further postpones the already-delayed survey. Such a breakdown in the IR survey routine can put the plant back into a reactionary maintenance mode. Failing to recognize this can make the IR program seem ineffective. Having a standard schedule and sticking to it whenever possible avoids this situation, while still allowing some flexibility for emergencies. Consistent IR surveys are the only way to make thermography an effective tool in preventing avoidable equipment failures (Figure 1).
Figure 1 also highlights the importance of timely repair. The thermographic image reveals a significant overheating problem. Failure of this connection would force the associated distribution control center to switch to a backup feed, and possibly force a transfer to backup generators. With all systems functioning properly, such a transfer would be seamless for most of the data and control systems. Conversely, should this component fail catastrophically, the resulting arc flash could destroy the entire feed cabinet circuitry. A catastrophic failure of this sort would cost at least 10 times more to repair than fixing the problem as found.
Figure 1. This 200-ampere terminator connector is in an electrical cabinet feeding a distribution facility. In a visible-light image, it appears normal. A thermographic image reveals abnormally high temperatures, indicating an impending failure. (Lighter colors indicate higher temperatures.)
For many installations, the IR survey schedule should start at the time the equipment is first commissioned to establish baseline data. This promotes safety, ensures proper installation, identifies OEM defects, and ensures service continuity.
Following the initial survey, a good guideline is to conduct another one within one year. However, certain equipment types warrant more frequent surveys. On the other hand, highly reliable electrical components might not require another survey for as long as three years, provided that the one-year survey reveals no problems or disturbing trends.
Establishing an IR survey plan also includes safety considerations, operational reliability, optimization of maintenance costs and communicating the results. By recognizing the importance of, and developing, a standard equipment schedule and IR survey plan, thermographers can contribute real value to their plant’s PPM program.
Safety is of utmost concern in every industry. This is particularly true in electric power distribution. Making IR thermography an effective PPM tool not only prevents equipment failure, it also improves safety for maintenance personnel. In fact, the first step in a thermographer’s survey should be to use the IR camera to sweep the entire survey area, looking for major problems that pose safety hazards. If none are found, the routine survey can begin. If a potential hazard is present, it should be documented and appropriate maintenance personnel notified immediately. In some cases, the thermographer should leave the area immediately.