MDI Case Study: Gear Mesh Faults

Case Study Provided By Educational Partner Machinery Diagnostics Institute (MDI)

Introduction
Gear mesh faults are a common problem in mechanical systems that involve gears. A gear is a rotating machine part with teeth that mesh with other gears to transmit torque and power between different parts of a machine. When the teeth of the gears do not mesh properly, it can cause vibrations, noise, and wear, leading to premature failure of the gears and the entire system. Gear mesh faults can be caused by a variety of factors, including design, manufacturing, and operation.

There are several types of gear mesh faults, including:

Wear: Over time, the teeth of the gears can wear down due to repeated contact with each other, which can cause a decrease in performance and increase the risk of further damage.
Pitting: Occurs when small cracks or holes develop on the surface of the gear teeth due to repeated stresses or impacts.
Cracking: Can occur in gears due to excessive stresses or impacts, and can lead to catastrophic failure if not detected or repaired.
Chipping: Occurs when small pieces of the gear teeth break off due to excessive stresses or impacts.
Misalignment: Occurs when the gears are not properly aligned with each other, which can cause uneven wear and damage to the teeth.
Scoring: Occurs when the teeth of the gears become scratched or scored due to foreign objects or debris in the system.

Analysis
MDI was commissioned to perform routine analysis at a Cement Plant. A gear mesh defect was found on a gearbox.

MDI utilized the following hardware for analysis:

CTC's AC246 Side Exit, Mini Size, 100 mV/g Accelerometer
CTC's MH128-1A Multipurpose Magnetic Mounting Base
CTC's CB108-K2C-006-C555-SF Emerson/CSI Compatible Cable and Connector Assembly
CSI 2130 Data Collector

renderings of a A CTC AC246 mini size accelerometer on an MH128-1A magnet base, and a cable and connector assembly

Utilizing a cable with a breakaway safety feature (as shown in the image above) is extremely important for analyst safety while collecting data on large operating machinery.

Conclusion
Through routine data collection, MDI was able to see that there was a clear gear mesh fault, which ended up being a chipped tooth. As a result, the recommendation was to replace the gear, prior to failure.

Selecting the correct accelerometer for gearbox measurements is important. MDI selected the AC246 because of its premium design that allows for an extremely wide frequency response range for a side exit accelerometer. This side exit sensor features an integral stud, which allows the sensing element to be centered within the case to maximize high frequency response (unlike other side exit sensor designs which feature a captive bolt that offsets the sensing element). This design allows the sensor to achieve a broad frequency response range of 0.6 to 15 kHz ±3dB, enabling it to detect a wide range of faults.

Related CTC Products
In addition to the CTC products used by MDI, CTC also offers a variety of vibration analysis hardware solutions that are ideal for use in applications like those explored in this case study. For some gearboxes, utilizing a 500 mV/g accelerometer may be appropriate. Slow-speed gearboxes are typically used in applications where the output speed of the gearbox is relatively low. These gearboxes are designed to provide high torque at low speeds. 500 mV/g accelerometers are specifically designed to detect low speed, low amplitude vibration beginning at 0.1 Hz. For slow-speed gearboxes, CTC recommends:

renders of a top exit and side exit standard size accelerometers mounted on round magnets with 2 rails

Shown above:

AC133 Low-Frequency Accelerometer
Standard Size, Top Exit 2 Pin Connector, 500 mV/g, ±10%

AC134 Low-Frequency Accelerometer
Standard Size, Side Exit 2 Pine Connector, 500 mV/g, ±10%

Both AC133 & AC134 are shown mounted on MH214-3A Magnet Mount Base
Multipurpose 2 Rail Magnet Mounting Base with 1/4-28 Blind Tapped Hole and Integral Rotating Mounting Nut, 50 lbs. Pull Strength, 1.4 in. (35.56 mm) OD, 0.75 in. (19.05 mm) Height, Aluminum Wrench Included

render of a cable assembly with a coiled cable, a safety feature, and a connector on each end

Cable assembly shown above:

CB104 Coiled Cable
2 Conductor Coiled, Shielded Cable, Black Polyurethane Jacket, 0.21 in. (5.3 mm) OD, 250°F (121 °C) Maximum Temperature

K2C Connector
2 Socket MIL-Style Connector with Rubber Bending Strain Relief, Polyurethane Molded, Portable Measurement, 250 °F (121 °C) Maximum Temperature

C555 Data Collector Connector
Emerson 2140 & 2130 Compatible, 5 Pin M12 Connector, Channel "A" Acceleration Input, Pin 2 Acceleration/Power (+), Pin 5 Common (-)

SF Breakaway Safety Connector
Break Away Safety Connector, 250 °F (121 °C) Maximum Temperature

_______________________________________________________________

About MDI
Machinery Diagnostics Institute based in Queensland, Australia, is an official educational partner of CTC. They are recognized globally as some of the most highly-regarded trainers and educators in the vibration analysis industry. MDI offers in-person and virtual technical trainings on topics including vibration analysis, thermal imaging, machinery lubrication, ultrasound testing, turbo machinery, machine balancing, shaft alignment, and asset reliability. The MDI team is proud to partner with other industry leaders including Mobius Institute, ICML, and Infraspection Institute.

Back to Blog Archive