Non-destructive testing
Before and after you buff...
Retreaders rely on non-destructive testing equipment By Bob Bissler
S
uccessful truck tire retreaders know that preparing a casing for retreading is an exact science. The visual inspection of a used truck tire is not enough to make sure all the faws and nail holes have been detected. Non-destructive testing (NDT) also is required. With computer-controlled NDT machinery, a retreader can produce a fnal product that ofen provides more miles than a new tire. And at less expense. According to the 2013 Modern Tire Dealer Facts Issue, the average price of a new truck tire is $425; the average price of a retreaded truck tire, including the casing, is $230. “Shearography falls within the NDT category,” says David Stevens, managing director of the Tire Retread & Repair Information Bureau (TRIB). “Some people say, ‘Tat’s an NDT machine,’ and some say, ‘Tat’s a shearography machine,’ but basically you’re talking about looking inside the tire without destroying it.” In many retreading operations, shearography is the NDT method of choice, but it’s not the only one. Here are some of the companies that supply NDT equipment, which helps raise your professional standards and makes you a more viable supplier.
A separation inside a tire creates a space, and over time air migrates into it. To detect the air bubbles and other faws, the casing (without the rim) is put into the Intact’s vacuum chamber for under-pressure loading. One measurement is taken at standard ambient pressure, and then the pressure is reduced by 5%. Tis is a minor change, says Huber, but it increases the diameter of any air bubbles in tread separations. “Te increasing air bubbles deform the tire’s surface by microns,” says Huber (a micron is one-millionth of a meter). “Tat surface deformation can be measured using shearography.”
Michelin Retread Technologies Inc.
According to Mary Ann Kotlarich, commercial public relations director at Michelin North America Inc., Michelin supplies complete retread processes to its franchisees, including shearography, through its Michelin Retread Technologies (MRT) subsidiary. Called the Casing Integrity Analyzer (CIA) system, this proprietary equipment, imaging and analysis system for casing inspection is only available to MRT franchisees. MRT has shearography equipment in 100% of its plants and requires its use on all casings afer initial inspection. One of them is Valley Tire Co. Inc., which has one MRT facility in Charleroi, Pa. “In our system, we have NDTs [grazing light/electronic liner inspection, advanced X-ray] for the initial inspection,” says Jim Stankiewicz, president of Valley Tire Co. Inc. “We buf next and then we put them into the shearography. We have two Michelin shearographs.” Stankiewicz has been an MRT retreader since 2007. He says every operator has to be certifed on each piece of equipment. “Our shearographs will pick up normal separations,” says Stankiewicz. “It’s automated and does everything — rolls the tires in, closes the doors, reads eight diferent segments on a tire and gives you printouts. Te operators know what to look for and it’s all computerized.”
Marangoni Tread North America Inc. The Intact Tire Test System from Steinbichler Vision Systems Inc. horizontally loads truck tires into its vacuum chamber and measures the tires in eight sectors to detect faws. The company says it can detect 95% of faults.
Steinbichler Vision Systems Inc.
“Shearography is a very sensitive, laser-based inspection technology similar to holography,” says Rainer Huber, NDT product manager at Steinbichler Vision Systems, manufacturers of the Intact Tire Test System. “We use the technology to fnd air bubbles and separations in casings for tire retreading. Tires with major air bubbles inside are not valid for retreading, because they would fail during usage.”
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According to Giampaolo Brioschi, product marketing manager for Marangoni Tread North America, a division of Marangoni SpA, the Marangoni IT 3000 SFER is the company’s most technical and sophisticated piece of tire inspection equipment ofered. “Te IT 3000 SFER is an NDT machine based on the technology of vacuum chamber shearography. Te machine has been designed to identify any belt and tread separations before the bufng procedure. Te inspection system is integrated in a complete measuring head with laser diode.” Brioschi says the IT 3000 SFER’s principle of testing is based on a comparison between a frst interference image of the tire surface and a second interference image of the deformed
MTD October 2013
