Thermography: a hot spot for maintenance.
Today, mills can use the next best thing--advanced thermography. Using high-tech cameras that can detect minute variations in the temperatures of various materials, pulp and paper mills are using thermography to detect previously unseen problems--before they result in unscheduled downtime or catastrophic failures. The cameras cost up to about US$ 50,000. Clear photos of individual problems allow these problems to be classified and repaired.
One of the leading advocates of thermography is Smurfit-Stone Container's mill in Panama City, Florida, USA. Mickey Bevis, predictive maintenance superintendent at the Panama City mill, gave a presentation on his mill's extensive use of thermography at the TAPPI Paper Summit, held in May 2004. This article is based on his wide-ranging presentation. The Panama City mill, which was profiled in the October 2004 issue of Solutions!, operates a market pulp machine and one liner-board machine averaging about 1800-1900 tons/day of total production.
The Panama City mill uses an Agema 570 thermographic camera from FLIR Systems, Boston, Massachusetts. The camera has an LCD screen, a voice microphone to record operator comments, and a zoom lens. The camera can identify variations as fine as one tenth of one degree F. The camera is returned to the supplier once a year to be cleaned and calibrated. The Agema camera is regularly scheduled by various departments in the mill and is in use most of the time. For example, the mill checks all of its motor control groups every 60 days.
Camera operators must be certified, and start out as level one thermographers. The mill currently has four predictive maintenance specialists and eight electricians using the camera. The 40-hour training course is typically completed over a four-day-period. The normal range of the camera is 30 to 60 feet, although a long-range lens is available that allows for operation from 200 to 300 yards away.
The Panama City mill combines its thermographic photographs with reports on specific maintenance situations and uses the reports to schedule repairs, according to Bevis. Typically, the photographs show situations where "hot spots" (temperatures above normal) exist.
"The report includes trend information so we can see if the problem is getting worse," said Bevis. "For example, if we identify a problem in the motor control center (MCC) cabinet, we attach the defect report to the cabinet. At the next outage, we go in, fix the problem, and remove the report."
Many of the issues the mill has identified and repaired by using thermography involve electrical equipment problems. They include the following:
* Bad electrical connections. These included a loose connection on breaker line and load phases, and over-tightened connections on breakers, both of which resulted in overheating. Thermography identified the problem connections and the maintenance staff corrected them when the breaker was shut down.
* Partially broken electrical wires. Loose or broken electrical wire strands typically show up as hot spots, and the camera operator can reference an intact wire next to the broken wire to determine the normal temperature.
* Undersized electrical wires that are not broken but are malfunctioning.
* Loose insulator bolts.
* Defective insulator assemblies.
* Bad connections on disconnect switches.
* Loose connections on a buss bar. In one case, the connection was over 300 degrees F.
* Plugged transformer tubes that are unlevel or low on insulating oil.
* Breakdown in winding insulation.
* Broken stator bar. While the motor was in the shop, current was introduced and the damage became evident within several seconds.
IDENTIFYING OTHER ISSUES
In addition to these electrical problems, the Panama City mill has used its thermography program to identify many other maintenance issues, including:
* Defective motor bearings
* Loose belt drive on a pump, which over-heated a pulley.
* Plugged dilution nozzles in a high-density storage tank. "We knew we had a problem with plugging, so we took pictures of the high density storage tank and found three plugged dilution nozzles. This allowed us to repair just the problem nozzles instead of taking all of them apart, saving money and time," said Bevis.
* Plugged green liquor line that nearly shut down the mill. "Instead of breaking down the line, we walked the line with our camera and found the plugged spot so mechanics knew where to fix it. Solving this problem quickly paid for the entire cost of the Agema camera," said Bevis.
* Material levels in the lime silo. "Our level probes had gone out and we needed to know how many lime trucks to order. We were able to determine the lime level and came up with an accurate order," said Bevis.
* Storage tank liquid levels.
* Sludge buildup in mud storage tanks. "We took pictures of four quadrants around the tank to see if the buildup was on one side," said Bevis.
* Identifying a wet edge on the linerboard sheet.
* Waterlogged dryer. "We walked the dryer section with the camera and found one dryer operating at 169 degrees F, while its neighbor was operating at 275 degrees F. The first dryer was water logged and not performing well," said Bevis.
* Defective steam valve in "closed" position, but with its slide open. This was a dangerous situation.
* Defective, "frozen" roller conveyor bearings.
* Missing bricks in the lime kiln. "For planning purposes, we needed to know how many men and materials were needed to fix the lime kiln, so we used the camera to identify all the missing bricks inside the kiln," said Bevis. "We then marked the defective areas."
* Storage tanks that need additional insulation. "Using our pictures, the maintenance planner can, for example, determine that the tank body insulation is in good shape, but that we only need to insulate around the piping elbow, or some other specific area," he said. "This helps you define the job scope and then check to make sure the job was done right afterwards."
* Leaking furnace door in need of a new gasket.
* Deteriorating insulation on recovery boiler precipitators.
Bevis also reported that insurance underwriters are becoming very interested in industrial thermography and he expects that at some point thermography programs may become an integral element of business interruption insurance polices.
"We started the program about 7 years ago, and it has turned out to be a terrific asset for us; it is our favorite and most versatile maintenance tool," concluded Bevis.
WHAT YOU WILL LEARN:
* Why thermography is a valuable reference tool.
* Specific examples of how thermography has been used at Smurfit-Stone Container's Panama City, Florida mill.
* Why insurance adjusters may require thermography in the future.
* FLIR Systems: www.flirthermography.com.
* Infrared Training Center: www.infraredtraining.com
ALAN ROOKS, EDITORIAL DIRECTOR
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|Title Annotation:||SOLUTIONS! CASE STUDY|
|Publication:||Solutions - for People, Processes and Paper|
|Date:||Apr 1, 2005|
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