Ultrasonic Inspection is very slow and has a “blind” spot between the probe and 3mm into the surface. Ultrasonics can miss cracks. However, it will provide information deep into the gear cast.
An argument can be made on the relevance of finding casting imperfections:
Ultrasonic inspection would detect porosity and inclusions in the cast but it is harder to detect surface cracks unless they propagate to the surface from the inclusion. It’s important to understand that porosity and inclusions found in the cast that have not propagated to the surface cannot be repaired.
ASTM E2905 detects 100% of all gear teeth surface indications larger than .40mm.
The reason why casting imperfections are not as important is because there is no way to repair them.
It’s only when the casting imperfection creates a crack that propagates to the surface that it becomes a problem. These are on cast gears only.
Any casting imperfections should be identified by the manufacturer’s Quality Control Program before the gear leaves the plant.
The advantage of inspecting mill gear drives utilizing ASTM E2905 over Eddy Current, or for that matter, all other methods of NDT for gearing applications, is recorded data is utilized. ASTM E2905 is cleaner, faster, documentable, and covers a larger area in less examination time better than any other traditional Non-Destructive Testing methods today for gearing applications. Drastically reduces inspection time. Covers a large area in one single pass. Provides real-time mapping of the inspected region, facilitating data interpretation. Improves reliability and Probability of Detection (POD). Unlike some other inspection methods, this will size cracks accurately, and all of the data is electronically archived for future reference in C- Scan imagery.
The main advantage of E2905 are the 2 and 3D displays that are produced. With these types of displays, it is possible to characterize the defect.
Eddy Current (Disadvantages)
For example, Eddy-Current gives us only a phase angle and amplitude signal that we must interpret and thus make a judgment call on the type of defect. This judgment call relies solely on the inspector. See Figure 1.
Single Eddy Current Coil Must Be Moved across the addendum, dedendum and root.
Difficult to achieve full coverage of gear flank and root. Discontinuities can be missed. Figure 2
15 to 20 Hour Time Frame.
Non-compliance with ASTM E2905.
Hand Written Reports
ASTM E2905 (Advantages):
With 2 and 3D Dimensional Isometric Displays, we can see the defects as it is in the material.
Knowledge of the defect type helps in determining the root causes and eliminates the potential for errors.
The system will display the actual characteristics of the defects, (see Figure 3), this is a Pit.
Figure 3: E2905 illustrating a Pit on a gear flanks
Using E2905, it is very easy to see a crack or a pit on a gear tooth compared to interpreting the Eddy Current signal in Figure 5.
In other words a pit looks like a pit (see Figure 3) and a crack looks like a crack (see Figure 4).
E2905 is used in this configuration and has consistently shown the ability to discriminate between dents, pits and cracks.
Figure 4: E2905 illustrating a crack on a gear flank
Benefits of ASTM E2905 over Magnetic Particle and Dye Penetrant for Cleaning and Inspections of Mill Gear Drives
ASTM E2905 – Standard Practice for Cleaning and Examination of Mill Girth Gear Teeth – Electromagnetic Methods.
AGMA 919-1-A14, Condition Monitoring and Diagnostics of Gear Units and Open Gears, recognizes E2905 as an acceptable inspection method.
Cleaning times on a 10m girth gear is under 1 hour. No need to wipe gear teeth after cleaning, saving numerous person hours.
Inspection time on a 10m, 406 tooth gear set is 7 hours.
E2905 is cleaner, faster, documentable, and covers a larger area in less examination time and greatly improves Probability of Detection better than any other traditional Non-Destructive Testing methods today for gearing applications.
Covers a large area in one single pass. Provides real-time mapping of the inspected region, facilitating data interpretation. Improves reliability and Probability of Detection.
Complies with Insurance companies requirements and could reduce insurance premiums.
Preparation / Inspection Times
Magnetic Particle / Dye Penetrant
Full Electronic Backup
Total Time for Inspection
25 – 35 hours
Compliance with ASTM E2905
Much faster than traditional methods.
Provides more production revenue than using traditional methods.
All data is recorded electronically; not on paper as in Magnetic Particle or Dye Penetrant.