- Buyer's Guide
In the past three columns, my colleague John Schultz has asked you, "How mature is your PdM program?" He explained the five levels of predictive maintenance maturity, from Level 1 (not engaged) all the way through Level 5 (best practices). Carrying forward through the next several issues, I will follow that train of thought, but at the individual technology level.
Let's discuss your infrared (IR) thermography program. Do you have a skeleton program that allows you to check a box on your goals and objectives sheet? If so, you most likely aren't seeing any significant results in terms of identifying the presence of electrical and mechanical (yes, I said mechanical) failure modes. On the other hand, do you have a professional, formal, engineered thermal inspection program that pays dividends on the electrical, mechanical and stationary equipment in your facility? Let's take a look and see which one you actually have.
Some Level 1 programs have an IR program on their high-voltage (greater than 600 volts) switchgear. This normally comes in the form of an annual inspection conducted through an insurance carrier. Most of the time, these programs center around preventing fires in the plant and detecting faults on the large, expensive transformers and switchgear that feed the entire plant. A Level 5 program is inclusive of all electrical components in the facility. Additionally, the Level 5 program has standards that allow for no thermal anomalies. Level 1 programs, on the other hand, only report problems that show drastic temperature differences (e.g. 25 degrees Fahrenheit between phases).
The mechanical and stationary side of the house is where most IR programs fall woefully short of the mark. This always confused me because a comprehensive mechanical inspection program can pay immediate and drastic returns. Another point of confusion is that your failure modes analysis should have alerted you to the possibility of problems that are most easily (and sometimes only) detectable via thermal analysis. However, people still don't have any type of mechanical inspection tasks inside their IR program. Failure modes like V-belts too tight, seals improperly installed and refractory degradation are all problems that are easily detected with infrared thermography, but not enough people use the technology to find these types of faults.
One of the most powerful tools in a reliability effort is a well-trained operator and spot radiometer. Level 5 programs have operators who are task qualified in the proper use of spot radiometers and have a set of points on their machine(s) that they measure several times per shift. They are a powerful defense against impending failures. When an operator is used to seeing 114 degrees F on a given point (a coupling, for instance) and then today measures it at 132 degrees F, a notable change has occurred. Immediately, the operator (if there is a standard workflow procedure in place) knows to call the PdM technician and request a special, more detailed analysis of the situation. Is it a misalignment? Or, is it a dry coupling in need of lubrication? This is hard for the operator to know with such a simple measurement, but it will be easy for the PdM team to figure out. A Level 1 program has no such inspection procedure in place and, therefore, can't enjoy the benefits of this additional level of defense.
Another extremely powerful tool in the reliability effort is to have both electrical and mechanical crafts personnel task-qualified in the proper use of spot radiometers. Electricians can use spot radiometers to troubleshoot electrical apparatus and for post-repair verification. For example, if the PdM thermographer previously had identified a thermal anomaly (i.e. "hot spot") and the electrician made the repair, the electrician could then double-check his work with the spot radiometer and know beyond a doubt that the defect was eliminated. Also, given this new level of knowledge and the new tool, on regular jobs such as replacing breakers and starters, the electrician could use the spot radiometer to double-check all of the connections to make sure none had received an improper amount of torque. Mechanical crafts personnel can use the same tool for similar functions. Thermography is excellent for double-checking seal installations, bearing alignment and coupling repairs.
There are several facets of a comprehensive thermal inspection program. It's not limited to significant problems on the high-voltage electrical switchgear. Take a look at your program. At what level are you? Are there other ways you can take advantage of thermal analysis?