Mill and Kiln Gear Teeth

Methods of examining large girth gear teeth to detect surface breaking flaws have often been time-consuming and limited in terms of data collected. However, a new ASTM International standard provides a more effective method for gear examination using eddy current array, a technology that has been widely used but, until now, not standardized.

ASTM E2905/E2905M, Practice for Examination of Mill and Kiln Girth Gear Teeth - Electromagnetic Methods, was developed by Subcommittee E07.07 on Electromagnetic Method, part of ASTM International Committee E07 on Nondestructive Testing.

Tom Shumka, president, Global Inspections–NDT Inc., and an E07 member, confirms that ASTM E2905/E2905M addresses the need to detect surface breaking flaws electronically and to accurately size any surface breaking cracks found on cast and forged mill girth gear and pinion teeth faster and more effectively than other methods.

ASTM E2905/E2905M describes a two-part eddy current array procedure. The first part, using eddy current array technology, covers the ability to detect 100 percent of surface-breaking discontinuities in the addendum, dedendum and root area of a gear tooth. The second part, using alternating current field measurement, is concerned with accurate measurement of the length and depth of any cracks found in the areas specified in the first part.

"The applications for this standard include detection and sizing of surface breaking flaws in any conducting material," says Shumka. "The principal advantage of eddy current array over other examination methods is the faster scanning speed and the fact that no coupling fluid is required."

According to Shumka, the new standard will provide a quick reference to improve understanding of eddy current array testing on mill and kiln girth gear teeth across every applicable level of contractual parties. Shumka says that ECA technology, which has been used in the nuclear industry for years, is clean, fast and easily documented. In addition, the probes used in ECA can be shaped to fit complex geometries of gear teeth.

"In today's world, production and uptime on industrial equipment is of utmost importance," says Shumka. "Although most gear engineers have known about using ECA for years, most wanted a standard developed before they would consider using the method."

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CONTACT Technical Information: Thomas Shumka, Global Inspections-NDT Inc. • Kelowna, British Columbia, Canada • Phone: 250-762-5525 | O ASTM Staff: Kathleen McClung • Phone: 610-832-9717 | Upcoming Meeting: January 25-30, 2014 • Ft. Lauderdale, Fla.

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