When UV Needs TLC

It's quick and simple to maintain UV equipment, and the effort may make system problems easier to pinpoint.

By Susan Friedman

"It's the inks."

"No, it's the equipment."

"No, it's the inks."

"No, it's the equipment."

Diagnosing a UV curing problem can create a heated volley of probable causes.

According to Jim Flynn, product manager, UV curing, Hanovia, initial detection of the problem is the easy part. "The usual sign that there is trouble brewing is when the UV system stops curing or you have to slow down to get a proper cure," he states.

Then the going can get dicey, even with the help of radiometers, power pack current meters, and other indicators. "Distinguishing definitively between a lamp and ink problem is difficult. Both can give you the same symptoms," states Pete Kershner, new business development manager, EYE Ultraviolet.

Flynn adds that the root of the malfunction can be clouded by unaccounted-for factors such as heavier coatings, or production errors such as increasing press speeds without boosting lamp power.

Clean Comments

Fortunately, a little foresight, elbow grease and preventive know-how can stop many UV curing equipment problems before they start, or at least rule out a few possible causes. More comprehensive, PLC-controlled service reminders can make maintenance even more of a no-brainer.

"Converters want the car that will go 100,000 miles without an oil change," says Doug Colton, U.S. operations manager, Nordson Spectral Technology Group. "We have to build UV packages with good diagnostics and minimize the maintenance required."

Indeed, the list of UV components requiring periodic attention is short. According to Tom Heffernan, director of marketing, UV Process Supply, the UV lamp and irradiator (lamp housing reflector), are the two most critical elements of the system, requiring regular service and cleaning.

Different types of UV lamps will affect the frequency of cleanings, advises Colton. "Air-cooled, shuttered lamps act like big vacuum cleaners as air is pulled across them, attracting ink fly, dust and contaminants to the reflector and bulb," he says. A thorough cleaning with isopropyl alcohol should be done weekly, or ink will bake on and cannot be removed without scratching the reflector, he cautions. Filtered lamps, which are cooled with water tubes instead of air, can run clean for up to a year, he notes. The ion levels in the water are monitored by a microprocessor.

Converters who are stingy with maintenance will pay for it in system performance. Intense heat will pit aluminum reflectors, and not maintaining this component's reflectivity could result in up to a 20 percent loss of energy at the material surface, which could cause undercuring, warns Heffernan.

Suppliers collectively preach the virtues of quick access for more painless UV upkeep, and imply that some converters are making cleaning more difficult than it has to be.

"Lamps should be the easiest to access for replacement, but I've seen these practically buried behind water cooling pipes and other components," relates Flynn. "Irradiators should be easy to get at, but on small presses in confined areas, only those on rails are getting the thumbs up from maintenance people. Power supplies in either ballast racks or approved cabinets seem to be easiest to maintain and replace."

Life Expectancies

The majority of UV lamps are guaranteed to last 1,000 hours, and many will keep ticking for 1,500 hours. Reflectors should stay functional for two years.

With these average life expectancies in mind, the foremost order of business is establishing a solid replacement inventory, emphasizes David Rose, UV product manager, Ernst W. Dorn Co. And it doesn't have to be expensive. Back-up lamps typically run $200 to $400, he says, and reflector linings, which only run $80, are often the right prescription for irradiator upgrades. An entire reflector can cost up to $1,000.

Certain practices will snuff out lamps prematurely. "Many consecutive hours of lamp usage is not too damaging, but repeatedly turning the lamp off and on is," says Kershner. Adds Rose, "Touching the bulb also reduces lamp life, because the skin leaves oil on the bulb that causes a hot spot, therefore weakening the quartz."

Users won't notice much of a difference in the longevity of 300 watt and 400 watt lamps, but life cycles vary highly between 400 watt lamps, which can last 1,500 hours, and 800 watt lamps, which may burn out in 800 hours, depending on cooling system capabilities, Kershner points out.

UV systems' key electrical component, the ballast, primarily fails due to excess heat, Rose states. Proper ventilation in the main electrical cabinet can help keep replacement at bay, which can cost $3,000. If there is a loud buzzing coming from the ballast, 30 to 60 days of life remain, he notes.

UV Maintenance Hot Spots

Lamps—Inspect and clean with nonresidual glass cleaner that contains no waxes or solvents every 300 hours

Reflector Liners—Inspect and clean when lamps are cleaned

Shutter Mechanism—Inspect, clean and lubricate (with high-temperature, anti-seize lubricant) cam, cam rollers and bushings when lamps are cleaned

Outer Lamp Housing and Base (grills)—Clean with compressed air monthly, wash annually

Press-mounted Light Shielding (grills)—Clean with compressed air monthly, wash annually

Auto-dampers—Clean screens monthly with compressed air

Exhaust Blowers—Inspect belts, lubricate bearings monthly

Power Supply/Control Cabinet—Check lamp voltage and current once a shift; check air filter monthly

Utility Connections—Maintain clean and dry air supply; drain air dryer weekly

Source: Fusion Aetek UV Systems