IR reduces energy and maintenance costs

By Robin Thon, Albany International

BRUSSELS, Aug. 3, 2009 (RISI) - Paper mills and other processing facilities are under intense pressure to reduce costs. Reducing labor and driving down vendor pricing on goods and services are two common ways of doing this. However, both are short-term solutions with significant limitations, and may have negative long-term effects. One long-term solution, especially with energy prices on the rise, is finding ways to reduce energy consumption and maintenance expense. IR thermography (thermal imaging) is uniquely effective for preventative/predictive maintenance (PPM) and process monitoring in paper mills. In fact, the IR cameras used in thermal imaging have become a strategic tool in identifying energy consumption problems, preventing unplanned downtime, and reducing product losses.

A few examples of successful IR camera usage in paper mills include: examining web moisture profiles; detecting hot roll bearings; finding plugged motor air intakes; and, spotting steam coil leaks.

Each of these problems contributes to excessive energy consumption. Fixing the underlying cause reduces operating expense, and increases profits.

Albany International uses FLIR P-Series IR cameras for its PPM work. (Fig. 1) This type of camera fully automates the process of collecting, reporting, archiving and performing trend analysis on all types of IR images and thermal data. All the images presented were collected with P-Series cameras. Temperatures that are either higher or lower than normal indicate the problems areas.

Figure 1 - Flir P-Series camera allows easy modification of measurement parameters

Web profile issues

Figure 2 is a thermographic image of non-contact temperature measurements made with an IR camera. It reveals wet streaks on the paper, which have lower temperatures (darker colors in the temperature scale on the right). This moisture profile required more energy than necessary to dry the paper web before applying a surface coating. Determining the root cause of this issue provides the papermaker with specific information that can reduce energy costs and increase paper production. The papermaker needs to dry the paper web uniformly to achieve a profile that is easier to coat. Higher uniform web moisture can be used if the wet problem area can be determined and corrected.

Figure 2 - Thermogram of wet streaks on paper during processing, indicated by lower temperatures (blue/purple end of the color scale)

Figure 3 illustrates a problem area caused by a damaged drying fabric. The damage could not be seen visually because it was on the backside of the paper machine, but the IR camera shows it as lines of higher temperature. The fabric was replaced and the machine was able to speed up by 50 ft/min. The web moisture was raised from 1.0% to 2.0%. The steam savings calculated to $100,000 annually.

Figure 3 - Damaged drying fabric, revealed by higher temperatures (lighter purple or magenta colors), which required slower operating speed

Bearing problems

Figure 4 illustrates a bearing that is 40°F hotter than nearby bearings. (Note camera measurement parameters that are automatically displayed.) The paper mill had a vibration test done and did not find any noise in the bearing. During the next maintenance outage following this diagnosis, the bearing was disassembled. It was determined that old grease had caused the temperature rise. A contact pyrometer was used to independently verify that the bearing came back to a normal temperature after the grease replacement. The problem had not only caused higher machine drive load, but failure would have resulted in the loss of a $100,000 forming fabric. Machine downtime costs are normally $6,000-$15,000 per hour. Failure could have easily resulted in 12 hours of unscheduled downtime. At $10,000 per hour the cost would have been another $120,000.

Figure 4 - Thermal image revealing hot bearings caused by old grease, which did not show up in vibration analysis. the temperature was compared with nearby bearings, which were running some 40°f cooler

Plugged motor intakes

Figures 5 and 6 are two high-pressure shower pump motors, both with the same horsepower, developing 200 psi of water pressure for the shower. The hotspots in Fig. 5 (lighter colors) are 52°F hotter than the hottest spot on the motor in Fig. 6. A vibration test the day before had shown no issues with either motor. The culprit ended up being plugged cooling air intakes that caused the motor in Fig. 5 to overheat. After clearing the intakes, motor temperature dropped to the same level as the one in Fig. 6. Premature failure in this case would have cost the mill a replacement motor as well as machine downtime. In addition to running hotter, the motor with plugged intakes was running at a higher amperage level, which relates directly to higher energy consumption.

Figure 5 - Shower pump motor with plugged cooling intakes runs hotter and draws more current (compare with figure 6)

Figure 6 - Thermal image of a shower pump motor with clear cooling air intakes, operating at a normal temperature

Steam coil leaks

Figure 7 illustrates the effects of a steam coil leak (green arrow pointing to cooler temperatures) for a pocket ventilation system. This system introduces warm dry air into the moist dryer section pockets to aid in mass transfer. Leaks like these raise the water grain load in the supply air. Generally, 100 grains of water or less is desirable for supply air at 200°F. This leak raised the grain load to 175 grains of water, which is three times the normal load. That increase relates to a higher absolute humidity and a smaller volume of dry air to absorb excess moisture. The mill repaired the steam leak and grains of water were reduced to 45. Following this corrective action the machine was able to produce 10 more tons per day; that calculates to millions of dollars of extra production annually.

Figure 7 - Thermogram illustrating the lower temperature caused by steam coil leakage in a pocket ventilation system

Figure 8 shows another steam coil leak that caused paper web moisture variations ahead of the coater. A leak such as this causes the machine speed to be reduced and uses more energy to dry the paper web. Repairs to the steam coils were made and the mill realized $125,000 cost reduction due to lower steam usage.

Figure 8 - Paper web moisture variations (lower temperatures) ahead of the coater caused by steam coil leakage

Conclusion

Many plants can reduce manufacturing costs by developing and implementing a predictive/preventative maintenance program. The IR camera is a valuable tool in these efforts. Financial returns from IR technology can be immediate and stretch over many years. With so much uncertainty in energy costs, IR imaging helps control consumption, and may allow a mill to produce high quality products at more competitive prices.

Robin Thon, Albany International, is a level II thermographer and has been using this technology for 14 years. He has been in the paper industry for 30 years. For more information on IR thermography, visit www.goinfrared.com/IRpapermills

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