Infrared Inspection Methods and Data Collection Techniques
EP Editorial Staff | October 5, 2000
As infrared cameras get cheaper and easier to use and become more widely used, there is a risk that some people will buy an infrared camera and call themselves thermographers. Owning an infrared camera does not make a person a thermographer any more than owning a stethoscope makes one a doctor. In addition to the infrared camera and digital camera, there are three essential tools needed for the professional thermographer: training, field experience, and standard methods for conducting infrared inspection.
There are several good training companies that can do a good job of explaining why training is essential for a professional thermographer. Therefore, this article will address infrared inspection methods: what to test, when to test (scheduling), equipment prioritization, additional factors, and data collection methods. The last section will show reports and the analysis that can be derived when standard data collection methods are followed.
What to test and when?
The first question, What to test?, is answered by using or creating an equipment inventory as the cornerstone for infrared inspection accountability. The equipment inventory can be recorded on paper during the inspection and then transcribed into a spreadsheet or database. It can be printed from an existing computerized maintenance management system (CMMS), or it can be entered into an infrared database program while the inspection is being performed. Without an inventory, the thermographer cannot account for what was tested and what was not. A piece of equipment can go for years without being tested if no inspection record is kept. A company hiring a thermographer should receive an inventory report of equipment tested and not tested. It costs very little to build the inventory, and the benefits far outweigh the costs in the long run.
By recording the test status of each piece of equipment in the inventory list during the inspection, the thermographer can answer the question, What did you inspect? To provide full accountability, test status information should include the following points:
- Current test status
- Date the equipment was last tested
- Results of the previous test
- Reason equipment was not tested during the last inspection (if it was not)
- When equipment is due to be tested again, if not tested this time.
An example notation currently used in the field for test status of equipment is as follows:
TBT: To be tested. Starting test status for all equipment.
NTNL: Not tested, no load. Commonly seen, because not all equipment can have a load during the inspection
NTTC: Not tested, time constraint. Scheduled to be tested but time ran out
NTNS: Not tested, not specified. Not scheduled to be inspected this time
NTUR: Not tested, under repair.
Once an inventory has been created, it is advisable to assign a criticality to the operations value of each piece of equipment. This procedure helps prioritize equipment for testing schedules and repair priority when a problem is found.
The following list can serve as a basis for developing a site-specific equipment criticality-to-operations list and the corresponding inspection frequency set for each.
- Crucial criticality: Inspect every 3 mo
- Essential criticality: Inspect every 6 mo
- Nonessential criticality: Inspect once a year
- Followup on problems or repair: Inspect every 3 mo
Once an inventory has been set up and inspection test statuses have been integrated, the infrared program has accountability. When the criticality to operation criteria have been added, a prioritized inspection schedule and repair list is ready. Bar-code labels on the equipment can be helpful in streamlining equipment inventory management. Without a basic equipment inventory, there is no accountability, no prioritized inspection scheduling, and no reliable infrared program.
What pertinent data should be recorded?
Once an inventory has been set up and the equipment to test has been determined, the next questions are, Besides recording the temperature of the problem and the reference, what other information is pertinent and should be recorded? Other than the emissivity value that the camera stores, what factors could greatly influence temperature measurements?
One factor is the equipment load; whenever possible it is important to measure and record load data. As Bernard Lyon stated in a paper presented at Thermosense XXII, “Temperature is certainly an important factor in evaluating equipment. However, if you follow the guidelines that are based solely on absolute temperature measurement, or on a temperature rise (DT), you run the risk of incorrectly diagnosing your problems. The consequences of such actions can lead to a false sense of security, equipment failure, fire, and even the possibility of personal injury.”
Another factor that should be recorded is wind speed. As shown in the wind effects experiment done by Robert Madding and Bernard Lyon and stated in their paper presented at Thermosense XXII, “The temperature rise was cut in half with just a little over 3 mph breeze.” The options available include buying a $100 anemometer to try to accurately measure wind speed or picking up grass, dropping it, and estimating wind speed. Either way, in most cases, the wind speed will have to be an estimate because even an anemometer will be some distance from the equipment being inspected. This condition is especially true regarding power lines. The important point is to account for wind speed by the best available means and record it. This information is especially crucial if baseline trending is being done on a problem.
Another notable factor is environment. Was it a hot sunny day, rainy, snowing, or clear but freezing? Environmental factors such as solar loading or a cold rain can affect temperature measurements. Again, this information is especially crucial if baseline trending is being done on a piece of equipment located outdoors. What was the weather like the last time the inspection was done? How does this information correlate to the temperatures measured?
Equipment load, wind speed, and environment are not the only factors that are important to note when a problem is documented. Other information that is less important to the thermographer but may be more important to management is the manufacturer and type of fault for each problem found. This information allows reliability to be analyzed by manufacturer or equipment type. By comparing the cost of repairing observed problems, a maintenance manager can look at the impact by manufacturer on the total operating expense of a facility. This information, in turn, can be used to improve future buying decisions.
Data collection techniques
The infrared camera is just a tool, and the thermogram is just the starting point in the data gathering process. The next step is to establish methods to ensure efficient, accurate data collection. These methods should have built-in procedures to guarantee that data quality is consistent from inspection to inspection and from thermographer to thermographer. These methods must not impair the pace of the inspection but should help in expediting the collection of data and aid the thermographer in his ability to diagnose problem conditions in the field.
For many years, the simplest and cheapest way to record data has been manually on paper. If this method is used, preparing preprinted problem write-up sheets with blank data fields will increase consistency and standardize problem write-ups. When used with an inventory list produced by a spreadsheet program or a CMMS, the write-up sheet is the starting point of a standardized infrared inspection system. This method of manual data collection works if labor costs are relatively inexpensive. Another method that has been used for many years is recording problem write-ups with a voice dictation recorder.
Although these methods are convenient, there are pitfalls to using either method. In both instances, there is the risk of losing data and introducing errors from misinterpreting field notes when typing up the reports at the office. Furthermore, the thermographer in the field does not have in his hand the analysis of past problems and other information when it would be of most value to him.
With the advancement of pen computers and database software, a third method of data collection has evolved. Instead of trying to bring field data back to the office and enter it into a database on the computer, the technician brings the computer into the field to enter the data directly into the database during the inspection. This advancement has proved to be the most reliable method of data collection available today, as well as the most cost-effective solution over time.
One efficiency of the mobile database is the instant turnaround time of report generation. Because all of the necessary information is put into the database at the time of the inspection, the reports can be printed immediately at the end of the inspection. Using a pen computer with an infrared database in the field, a thermographer can double the number of problems written up in a day (from 50 to 100) and completely eliminate report generation time.
The following comparison of paper or voice dictation method to pen computer with IR database method lists typical inspection and report generation times. Report generation includes inventory of equipment and associated test statuses, prioritized list of problems, and documentation.
Paper or voice dictation method
- 50 problems per 8-hr day
- Report generation takes 6 hr
- Total: 50 problems in 14 hr
Pen computer with IR database
- 100 problems per 8-hr day
- Report generation automatic
- Total: 100 problems in 8 hr
Another efficiency of a database on a mobile pen computer is its ability to yield more consistent inspection results because testing procedures can be methodically followed. Key information can be selected from drop-down menus. Past problem conditions on a chronic problem are immediately displayed and can be reviewed in the context of the new problem. Furthermore, the redundancy of data collection can be eliminated because information that was stored in the past, such as location, does not need to be re-entered into the database. Maps, work orders, inspection procedures, and other pertinent documents can be brought into the field because the database also can work as an electronic document management system.
Now that the inspection has been completed and the data have been collected, what analyses can be formed from following these methods? The software to ensure write-up consistency is extremely efficient; it eliminates typing and syntax problems while improving data accuracy. This method has many benefits over conventional methods because data are entered only once.
Management reports and analysis
The analysis outlined in “Problem Profile Report: Key Equipment Failure Ratios,” is from data collected for more than 10 years using the Thermal Trend Infrared PdM Inspection Management Database. Actual client and manufacturer names and specific products have been omitted to protect the clients and manufacturers. Data were collected from all over the world on many manufacturers’ equipment and in all kinds of plant environments. The data included in this analysis come from hundreds of thousands of problems and pieces of equipment.
Tracking problems and categorizing them by their temperature rise reveals trends in facilities’ health over time. Average temperature rise using all of the electrical problems documented in the database for electrical inspections as measured phase to phase is 54 deg F.
Problems in the database can be analyzed and ratios can be established for specific faults on key equipment by recording manufacturer and type of failure. This strategy leads to the ability to study the equipment thoroughly and analyze what factors play an important role in their failure, for example corrosion, overloading, or just a substandard piece of equipment. This analysis provides insight into the correct preventive maintenance measures to be taken so future problems will be minimized.
A cost breakeven report can be generated from materials and labor by recording equipment and labor costs before vs. after using an infrared inspection program. For example, 976 problems were documented at 55 industrial manufacturing sites. A cost-benefit analysis on the 976 problems shows a before vs. after failure savings on materials and labor of $408,040. The average cost saving per problem, if it is fixed before it fails works out to $418.07 for material and labor . This figure is very conservative and does not take into consideration the potential loss to revenue or to production, or the risk of financial loss from a major fire.
Analyzing cost savings reveals measurable results from implementing an infrared inspection program. On average, for every $1 spent on hiring a competent professional consultant to perform an infrared electrical inspection, there is a $4 return on investment for materials and labor to fix the problem equipment identified before it failed. This conservative 1:4 ratio clearly identifies the importance of maximizing the return on investment of implementing a comprehensive in-house or outsourced infrared inspection program. Furthermore, because of reduced losses and increased productivity, which in turn increase revenue, the return on investment ratio in some cases is closer to 1:20, depending on the industry.
Whether a thermographer uses a pad of paper or a pen computer, the data and methods followed are important to creating a standardized infrared inspection management program. Sufficient training and field experience cannot be emphasized enough as a basis to build a solid infrared program. Once components are in place, it is important to implement strong data collecting methods to get standardized results across multiple inspections and multiple thermographers. By recording appropriate supplementary information such as load, wind speed, and environment in addition to the thermographic image, a thermographer can better assess the severity of the situation.
By setting up a standardized infrared inspection program, tracking the pertinent information, and recording it consistently, a plant can manage and see the trends in the overall health of the facility. There is a wealth of information to gain by using these methods in a comprehensive infrared inspection management program. MT
Scott Cawlfield is president of Logos Computer Solutions, Inc., 3801 14th Ave. West, Seattle, WA 98119; (206) 217-0577.