Standard Practice for Examination of Mill and Kiln Girth Gear Teeth—Electromagnetic Methods
5.1 Visual interpretation of gear teeth condition is different from examining for cracks or early signs of macro-pitting. Visual interpretation is referred to ASNI/AGMA 1010-F14.
5.1.1 The purpose of using an eddy current array for mill girth gear tooth examination is it drastically reduces the examination time; covers a large area in one single pass; provides real-time cartography of the examined region, facilitating data interpretation; and improves reliability and probability of detection (POD). One tooth can be examined in less than 30 seconds.
Note 3: In this practice, ECA is used as a discontinuity finding tool (see Fig. 4) and a presentation aid as support once problems are discovered and photographed. Colors and three-dimensional (3D) images (see Fig. 5) that help with visualization are invaluable in such circumstances.
5.1.2 The purpose of using alternating current field measurement is to size surface-breaking cracks electronically.
5.1.3 This practice is a useful tool for a condition-based monitoring program.
5.2 The examination results may then be used by qualified personnel or organizations to assess the severity and potential consequences of the failure modes identified. This practice is not intended for the examination of non-surface-breaking discontinuities. Other methods should be considered to address examination for non-surface-breaking discontinuities.
Note 1: Throughout the standard, “gear” means gear or pinion unless the gear is specifically identified.
1.1 This practice describes a two-part procedure for electromagnetic evaluation on gear teeth on mill and kiln gear drives and pinions. The first part of this practice details the ability to detect 100 % of surface-breaking discontinuities in the flank and root area on both the drive side and non-drive (coast) side of the gear tooth using an eddy current array. The second part of the examination is to size or measure accurately the length and depth of any cracks found in these areas using electromagnetic methods. No other practice addresses the use of electromagnetic methods for the detection and sizing of surface-breaking discontinuities on mill and kiln ring gear teeth. For reference, Fig. 1 contains a schematic diagram labeling the areas of the gear teeth.
FIG. 1 Schematic Image Labeling the Regions of the Gear Teeth and the Area (Shown in Green Shading) That is Scanned in One Pass With the Eddy Current Array Probe
1.2 This practice is used only for the detection of surface breaking discontinuities including cracking, macropitting, and certain scuffing and wear patterns. It will not provide a full gear tooth analysis. Visual examination by an experienced gear specialist is the best way to characterize fully the failure modes present. It is imperative that the analysis of the gear teeth is completed at the time of examination. Sending data offsite for analysis later is not recommended, as potential failure modes could be missed from lack of in-situ visual examination.
1.3 Two technicians, one lead technician, and a gear technician, are typically required for this practice. One technician guides the probe and the other technician operates the computer/software and analyzes the gear teeth condition.
1.4 It is important that the appropriate method standards, such as Practice E3024 and Practice E2261, accompany the technician when performing the examination. If crack sizing is performed, then it shall be performed using an electromagnetic testing method such as the alternating current field measurement approach of Practice E2261.
1.5 It is recommended that the technician review the appendixes in this practice in advance of starting the job.
1.6 A clean gear is recommended for a complete gear analysis. Depending on the lubrication used, the technician, in discussion with the client, shall determine the appropriate cleaning procedure. If an oil bath lubrication system is used, ensure the gear teeth surfaces are clean. If an asphaltic-based or synthetic-based lubricant is used, refer to the annexes and appendices in this practice.
1.7 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.
1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.9 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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