Discover how spiderAI™, your assistive copilot for workflows related to condition monitoring, fault diagnosis, reliability engineering, maintenance, and repairs, can bring groundbreaking improvements in decision-making accuracy, productivity, and efficiency.

We are currently releasing it for vibration analysis, allowing maintenance and condition monitoring engineers to independently generate diagnostic reports with world-class expert-level accuracy in just one-tenth of the time previously needed.

Root Cause Analysis
Field Balancing
Precise Diagnosis
FMEA

Diagnosing High-Frequency Vibration Issues in a VFD-Driven Motor with spiderAI™

At an industrial facility, maintenance personnel observed an abnormal sound emanating from a motor when operated at the minimum speed range during load. Concerned, the team conducted a vibration analysis, revealing a raised noise floor in the spectrum, particularly in the 2000 to 3500 Hz range, with pronounced peaks around 3100 Hz.

This prompted further testing to identify the root cause. The maintenance team engaged spiderAI™ to analyze the vibration data, including the results of run-up and coast-down tests, with a focus on the motor's VFD-driven operation.

This case study demonstrates how spiderAI™ leveraged advanced diagnostic capabilities to quickly pinpoint the root cause of complex machinery issues, providing actionable insights for resolving high-frequency vibrations in VFD-driven motors.

Workflow

Initial Analysis and Testing

Vibration Spectrum Analysis: The spectrum revealed high-frequency vibrations, with the majority of peaks observed above 2000 Hz.
Run-Up Test: As the motor speed was increased from 3150 to 3490 RPM, some noise below 1000 Hz diminished as the current (i_rms) increased.
Coast-Down Test: During the coast-down phase, all peaks above 2000 Hz vanished immediately when the motor was turned off, suggesting the vibrations were electrically induced.

Engaging spiderAI™ for Diagnosis

The engineer engaged spiderAI™ to analyze the vibration data, including the results of the run-up and coast-down tests. With a focus on the motor's VFD-driven operation, spiderAI™ provided an in-depth analysis.

Diagnosis by spiderAI™

spiderAI™ identified the issue as high-frequency vibrations induced by the VFD's operation. The primary cause was linked to the VFD's switching frequency or its harmonics, interacting with the motor's electrical characteristics. This interaction was most noticeable at lower speeds, where the electrical noise generated by the VFD was exacerbated by the motor's mechanical resonances.

Recommended Actions by spiderAI™

Review VFD Manual and Adjust Parameters: Upon the engineer's request, spiderAI™ reviewed the ABB ACS150 VFD manual and identified the key parameters that need to be adjusted to rectify the high-frequency noise issue:

Switching Frequency: Set the frequency to 8 kHz or 12 kHz as a starting point. Note that higher frequencies may reduce noise but could require derating.
Acceleration/Deceleration Time: Ensure smooth transitions by adjusting parameters 2202 and 2203 to prevent abrupt speed changes.
Grounding and Shielding: Proper grounding and shielding are critical to minimize electromagnetic interference, as emphasized in the manual.

Scientific Explanation and Next Steps

The high-frequency vibrations result from the VFD's rapid switching, creating fluctuating electromagnetic forces within the motor. At lower speeds, these forces resonate with the motor's mechanical characteristics. The engineer should implement the recommended VFD adjustments and grounding checks, then conduct another run-up test to verify the effectiveness of these changes.

spiderAI™ Thread

For more updates and information, please contact us at spiderai@minto.ai. We're here to assist you with any inquiries and keep you informed about our latest developments.

Diagnosing and Resolving Critical Vibration Issues in a Fire Station's Water Pump Motor with spiderAI™

At a bustling fire station, the heart of the emergency response system is its fire water pump. This critical piece of equipment ensures a steady supply of water when every second counts in battling a blaze. Recently, the station upgraded its fire water pump with a new motor, expecting improved performance and reliability.

During a routine test run, the maintenance team was alarmed by an unusual rumble coming from the newly installed motor. Vibration readings at the motor's top bearing skyrocketed to 190mm peak-to-peak displacement and 14 mm/sec peak velocity - levels that could spell disaster if left unchecked. The situation was further complicated by an unexpected issue: the new motor's cooling fan was found broken upon installation, forcing the team to retrofit the old motor's fan as a quick fix.

Now, with the station's emergency readiness at stake, the pressure is on to diagnose and resolve the vibration problem swiftly. This conversation with an spiderAI™ vibration analyst demonstrates how advanced diagnostic capabilities can quickly pinpoint the root cause of complex machinery issues. By leveraging expertise in motor mechanics, vibration analysis, and failure modes.

Workflow

Initial Observations and Routine Inspection

During the routine inspection of the newly installed fire water pump motor, maintenance personnel observed alarming vibration levels at the motor's top bearing. Measurements revealed a peak-to-peak displacement of 190mm and a peak velocity of 14 mm/sec, significantly exceeding acceptable limits. An unusual rumble was audible during operation, raising immediate concerns. Upon closer examination, it was discovered that the new motor's cooling fan was broken, necessitating the use of the old motor's fan as a temporary solution.

Starting Conversation with spiderAI™

The engineer initiated a conversation with spiderAI™, providing initial observations, including motor RPM, motor type (inverter-driven, variable speed), machine type (fire water pump), drive train, and bearing information in form of screenshots taken from the reports he got.

Diagnosis by spiderAI™

spiderAI™ diagnosed the fault as unbalance caused by the replacement of the cooling fan with an old fan that may not be perfectly matched and the overall displacement of 190 μm peak-to-peak and velocity of 14 mm/sec peak at the motor top bearing (NDE) are significant.

Recommendations by spiderAI™

Inspect and Balance the Cooling Fan: Conduct a detailed inspection and balancing of the cooling fan. If possible, replace it with a new fan designed specifically for this motor.
In-Situ Balancing: Perform in-situ balancing of the motor rotor assembly, including the fan, to mitigate the effects of unbalance.

Field Balancing through spiderAI™

The engineer decided to conduct the field balancing and provided his field balancing procedure manual to spiderAI™ with the initial vibrational readings and readings upon adding trail weight. In return spiderAI™ calculated results and suggested to add 112.44 grams at Finn 3 (the same fin where the trial weight was added) but at an angle of 17.48° opposite to the phase shift observed after the trial weight was added.

spiderAI™ Thread

For more updates and information, please contact us at spiderai@minto.ai. We're here to assist you with any inquiries and keep you informed about our latest developments.