Why an IR inspection?
IR inspections of electrical equipment have long been used to reveal problems that show up as elevated temperatures. Abnormally high temperatures are often a precursor of micro arcs, flashovers, and fires. The thermograms collected with IR cameras can reveal high temperatures caused by degradation of electrical connections (due to oxidation and tightening faults), bad components, unbalanced load phases, and a number of other anomalies. In addition to preventing catastrophic equipment failures, just finding and correcting bad connections can save a lot of money by reducing electrical energy consumption.
These benefits were the motivation behind the South Carolina mill's desire to expand its IR inspection program. Still, the first step was to find a solution to the safety issues posed by the inspection of energized equipment with voltages and incident energy calculations that exceed NFPA 70E guidelines. In seeking alternatives for conducting safe, standards-compliant inspections, the corporate reliability engineer investigated how IR inspection windows (also referred to as IR viewports or sight glasses) might be utilized.
An important consideration was finding IR windows made of material that does not impede the transmission of IR energy. For example, conventional glass will not pass the wavelengths associated with IR energy. Viewports without any kind of glass or plastic lenses would be ideal, but this is not possible on many pieces of equipment for safety reasons. It was found that the model VPFR viewing panes from IRISS, Inc. would work.
Benefits or IR windows
It has been determined that the use of IR windows for routine inspections of healthy equipment do not require the elevated levels of PPE required in 70E, since as stated in 70E-100: "Under normal operating conditions, enclosed energized equipment that has been properly installed and maintained is not likely to pose an arc flash hazard." In NFPA terms, an IR window maintains an "enclosed" state for the switchgear, MCC, transformer, etc., and maintains energized components and circuit parts in a "guarded" condition. Therefore, the hazard/risk category is equivalent to reading a panel meter, using a visual inspection pane for lockout/tagout confirmations, or walking past enclosed energized equipment.
First and foremost, the use of IR windows and closed panel inspections eliminates high-risk tasks during inspections, thereby increasing safety for mill thermographers. In addition, IR windows eliminate the need for a supporting cast of electricians to remove and reinstall panel covers. These critical personnel then become available to perform other tasks, many of which were being outsourced by the mill. Since IR windows provide non-intrusive access to electrical applications, surveys can be conducted during peak hours for the best diagnostic data without elevating the risk to plant assets and processes.
Furthermore, IR windows give thermographers an efficient method of performing inspections. This makes more frequent inspections feasible on critical and suspicious equipment, which helps ensure plant uptime.
The focus of the mill's initiative was to facilitate inspection of the primary switchgear in its electrical distribution system that feeds one paper machine and several smaller operations within the plant. IRISS was commissioned to conduct a pre-site inspection to ascertain the optimal position and quantity of windows which would give thermographers thorough visibility of the desired targets. The conclusions from the initial inspection are noted in Table 1.
An impending 10-day shutdown increased the sense of urgency since it was determined that all windows could be fitted for one paper machine during that period. The customer quickly ordered 200 units of assorted VPFR-75 (3-in. diameter) and VPFR-100 (4-in. diameter) IR inspection windows for the installation. As shown in Table 1, a total of 197 windows were ultimately installed.
The parts cost for the 197 VPFR inspection windows totaled $42,050. IRISS was retained to supply a team to perform the installation of these IR windows. Installation costs sited in Table 2 were calculated using the following assumptions:
- Two-man installation team at $625 each per day (total cost $1,300/day) x 10 days = $13,000
- $30 per window installation charge x 197 windows = $5,910.
Thus, the installation cost was $18,910 and the total installed cost was $60,960.
Installation of the infrared inspection panes was conducted during three days and nights during the mill's 10-day shutdown. Some installations were completed on live gear using additional safety measures. However, the vast majority was conducted on de-energized equipment in what NFPA terms an "electrically safe work condition."
Although the installation plan allowed for 12-hour shifts, installers were quickly and safely moving at a rate of approximately six window installations per hour, and were finishing the plant on the night shifts within six hours. Installations during normal business hours allowed much more flexibility; therefore, all "live works" were completed during these periods. When mill electricians assisted with the work, installation rates went up to 7-8 windows per hour. All window installations were completed well within the allotted timeframe.
Table 1 - Study results of ir window requirements for a South Carolina paper mill
|13.8kV Primary Switch||15|
|MCCs (Motor Control Centers)||2|
Inspection cost analysis
Prior to the installation of the IR windows, all IR inspections were completed on open, energized gear. Therefore, PPE was required, along with live works procedures, risk assessments, permits, etc. As noted earlier, several applications had never been surveyed due to safety restrictions. For others, the mill's on-staff thermographer was trained and "qualified" to assist in opening panels on energized gear. Therefore, some efficiencies were already in place when compared with a typical crew of a single thermographer plus two electricians. Consequently, the man-hour calculations for the "traditional inspection" figures in Table 3 are actually conservative.
Table 3 details the man-hour costs for infrared surveys using in-house staff without IR windows or other viewports using the following assumptions:
- Total man-hours per inspection of "inspectable" equipment: 331 hours (23 days)
- Staff electrician internal charge-out rate $125 per hour
- Staff thermographer assists with panel removal, etc (two-man task)
- PPE suit-ups twice per day, per man (30 minutes per man per suit-up)
- One man-hour per compartment panel for safe removal, etc. (times two for 2-man team)
- 147 individual panels to inspect (per Table 1).
After the IR windows were installed and there was no requirement to remove panels or wear increased levels of PPE, so the task became a one-man job. The increased efficiency and economies of motion and manpower that IR windows allow decreased the time required to complete a survey significantly. Surveys now require just two 8-hour days, for a total of 16 man-hours. The costs associated with a survey using IR windows are detailed in Table 4. Compared with the costs of traditional inspections (Table 3), the paper mill now saves $39,375 per inspection cycle because of the efficiencies it gains with IR windows.
Table 2 - IR window parts and installation costs
|IR Window Units & Installation Investment||Cost|
|IR Windows (197 units, assorted 3” & 4” diameter)||$42,050.00|
|Installation Costs for 197 IR Windows||$18,910.00|
Table 3 - Inspection costs using traditional methods
|Cost of Traditional Inspection||Hours||Cost|
|In-House Team with|
|Inspection Time (hourly cost times 2 per team)||294||$36,750.00|
|PPE Suit-up Time (0.5 hour X 2/day X 2 men)||37||$4,625.00|
Table 4 - Inspection costs using IR windows
|Cost of Inspection with IR Windows||Hours||Cost|
|PPE Suit-up time||0||$0|
Return on investment
Table 5 combines the data from the previous tables to calculate the ROI from the mill's IR window expenditures. As shown in the table, a positive cash flow begins as early as mid-way through the second inspection cycle, yielding almost $18,000 in savings. In a little more than three cycles, the initial investment is paid off. From then on, the $39,375 savings per inspection can be used for other maintenance needs. In just five inspection cycles, the mill shows a savings of more than $135,000.
Moreover, because inspections can be completed with greater ease and without increased risk to plant, personnel and processes, the frequency of inspection cycles has been increased to quarterly, reflecting best-practice recommendations, which were previously not feasible and thought to be unattainable. The new inspection cycle probably delivers even greater ROI by reducing the risk of catastrophic failure among the plant's critical power distribution systems. Although this is hard to calculate, it should reduce production losses due to equipment failure.
Additional IR window installations have been planned and scheduled to occur during the facility's next shutdown, and the mill's in-house electricians are now trained to install them. This means that installation costs will be a fraction of the original project, saving even more money and accelerating ROI for additional windows.
Table 5 - ROI from a mill’s IR window expenditures
|197 IR Windows||$42,050.00|
|Installation of Windows||$18,910.00|
|Cost for 1st Inspection Cycle||$2,000.00||$41,375.00|
|Total for 1st Inspection Cycle||$62,960.00||$41,375.00||$(21,585.00)|
|Cost for 2nd Inspection Cycle||$2,000.00||$41,375.00|
|Total for 2 Cycles||$64,960.00||$82,750.00||$17,790.00|
|Cost for 3rd Inspection Cycle||$2,000.00||$41,375.00|
|Total for 3 Cycles||$66,960.00||$124,125.00||$57,165.00|
|Cost for 4th Inspection Cycle||$2,000.00||$41,375.00|
|Total for 4 Cycles||$68,960.00||$165,500.00||$96,540.00|
|Cost for 5th Inspection Cycle||$2,000.00||$41,375.00|
|Total for 5 Cycles||$70,960.00||$206,875.00||$135,915.00|
Infrared windows provide a cost-effective and safer alternative to traditional inspections. This mill realized a return on investment very quickly while benefitting from the other intangibles of infrared windows:
- Increased safety for the thermographer and other maintenance personnel
- The ability to inspect previously un-inspectable equipment
- The ability to inspect critical applications more frequently
- The ability to more aggressively monitor applications that are trending toward failure
- Decreased risk to plant assets and operations due to non-invasive nature of inspections
- Freeing up critical electrical maintenance personnel who can be utilized for other valuable jobs in the plant rather than removing and reinstalling panels.
A portion of the mill's financial savings was used to build and strengthen the predictive/preventative maintenance program through the purchase of a second IR camera and thermographer training. This underscores the mill's commitment to the practical use of technology to ensure higher uptime while enhancing the safety of its workers.
To learn more about the use of IR thermography in predictive/preventative maintenance, visit:http://www.flir.com/thermography/americas/us/content/?id=17908.
Martin Robinsonis a Level III thermographer and CEO of IRISS, Bradenton, FL.firstname.lastname@example.org.