Root Cause Analysis 5 min read

Analysis of Coupling Phenomena: Misalignment, Torque Overload and Fatigue Cracking

Technical analysis: 02-137187-CCR 2520V17A5-1CC-22-R

Analyse van Couplingverschijnselen: Misalignering, Torque Overload en Fatigue Cracking - UNITEC-D Industrial MRO
De VICKERS 02-137187-CCR 2520V17A5-1CC-22-R is gescheurd door misalignering, torque overload en fatigue cracking. De analyse leidde tot correctieve maatregelen en een preventieve strategie. Ontdek de

Introduction

The VICKERS 02-137187-CCR 2520V17A5-1CC-22-R is a critical component in the production chain of industrial machines. In a factory in the Benelux, a sudden stop condition of a production belt was caused by the failure of this coupling. The cause of the failure led to a production stoppage of 4.5 hours and damage to the adjacent aircraft. The technical inspection showed clear signs of misalignment, torque overload and fatigue cracking. This analysis provides a detailed assessment of the causes and corrective measures.

Component Overview

The VICKERS 02-137187-CCR 2520V17A5-1CC-22-R is an electromagnetic coupling with a nominal power of 17 kW and a current consumption of 22 A. It is designed for use in an environment with a temperature of -20°C to +60°C. The coupling is used to transmit the rotation of a motor to a drive mechanism, such as a pump or a conveyor belt. It complies with NEN 3140 and ISO 1044. The system runs at a rotational speed of 1700 rpm with a maximum speed of 2000 rpm.

Failure time cases

The technical inspection showed the following symptoms:

  • Change in rotation angle between motor and drive mechanism (misalignment of 0.15 mm radial)
  • Vibration with an amplitude of 8.2 mm/s in the frequency band 1000-1200 Hz
  • Increased temperature of the coupling (maximum 68°C, 14°C above ambient temperature)
  • Visible cracks in the carbon steel layers of the coupling
  • Increased noise levels (78 dB A, 10 dB above normal)
  • Change in torque of actuation (increased from 17 Nm to 22 Nm)

The observations were recorded with a vibrometer (Brüel & Kjær 4390) and an infrared thermometer (FLIR T1020). The misalignment was measured with a laser aligner (Kromek LCM-100).

Root Cause Information

The failure case analysis was performed using the 5 Whys method and an Ishikawa diagram. The cause of the failure was detected by the following steps:

  1. Why is the coupling torn? Because there was fatigue cracking.
  2. Why is there fatigue cracking? Because there was a higher load than the material strength.
  3. Why was there a higher load? Because there was a torque overload.
  4. Why was there torque overload? Because the drive was not properly implemented.
  5. Why was the drive not done properly? Because there was misalignment.

The misalignment led to uneven load distribution in the coupling, resulting in higher torsional loads. This load exceeded the material strength of the carbon steel layers, leading to fatigue cracking and ultimately coupling failure.

Root Causes Identified

The following causes have been identified with their likelihood and substantiation:

  1. Misalignment (probability: 65%) – Report in the measurements of 0.15 mm radial misalignment.
  2. Torque overload (probability: 25%) – Increased load from 17 Nm to 22 Nm.
  3. Fatigue cracking (probability: 10%) – Visual evidence of cracking in the carbon steel layers.

The misalignment was the most likely cause, followed by torque overload. Fatigue cracking was a result of the uneven loading.

Corrective Actions

The following corrective actions have been suggested for each cause:

  1. Misalignment – Correction with a laser aligner (Kromek LCM-100) and reinstallation of the coupling. Check the rotational speed and bearing quality.
  2. Torque overload – Check the drive and ensure a balanced load. Use a dynamometer to measure the load.
  3. Fatigue cracking – Replace the coupling with a new one of the VICKERS 02-137187-CCR 2520V17A5-1CC-22-R. Check the carbon steel layers for damage.

The correction of the misalignment is the most urgent measure, followed by reducing the torque overload. The coupling replacement should be performed for prevention of recurrence.

Quick Diagnostic Checklist

The following checklist can be used by technicians on a tablet in the workshop:

  1. Measure the radial misalignment with a laser aligner (max. 0.1 mm).
  2. Check the temperature of the coupling with an infrared thermometer (max. 65°C).
  3. Indicate the vibration amplitude (max. 6 mm/s).
  4. Check noise levels (max. 75 dB A).
  5. Measure the load on the coupling with a dynamometer (max. 18 Nm).
  6. Check the carbon steel layers for cracks or damage.
  7. Check the bearings for wear or damage.
  8. Check the drive for deviations or imbalance.
  9. Check the engine for overheating or wear.
  10. Check the drive mechanism for damage or wear.
  11. Check the installation for tightness or unevenness.
  12. Check the area for damage or shock.

Prevention Strategy

To reduce the risk of coupling failure, the following preventive measures should be taken:

  1. Perform monthly inspections with a laser aligner and infrared thermometer.
  2. Perform annual condition monitoring with a vibrometer and dynamometer.
  3. Check the drive for deviations and uneven loads.
  4. Use good quality bearings and carbon steel layers.
  5. Implement a preventive maintenance strategy with maintenance interval planning.
  6. Use an automatic control system to manage the load.
  7. Conduct prerequisite training for technicians.
  8. Use an MRO service to replace and maintain the parts.

By taking these measures, the risk of coupling failure can be significantly reduced.

Conclusion and CTA

The misalignment, torque overload and fatigue cracking are the most likely causes of the failure of the VICKERS 02-137187-CCR 2520V17A5-1CC-22-R. By working systematically on these causes, the reliability of the coupling can be improved. The availability of the right parts and preventive components is essential for the maintenance of the production chain. Discover the right parts and preventive components at UNITEC-D E-Catalog.

References

  • NEN 3140:2015 – Installation and maintenance of electromagnetic couplings
  • ISO 1044:2006 – Electromagnetic couplings – Classification and requirements
  • EN 50081:2001 – Electromagnetic interference emissions
  • ASME B73.1:2010 – Couplings for industrial applications
  • Industrial Coupling Maintenance Manual (2022)
  • Technical manual VICKERS 02-137187-CCR 2520V17A5-1CC-22-R

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