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Wyoming Public Utility Shaft Breakage Torque Study

Problem: Shaft Breakage – (2) 1500 HP Reliance Electric Motors

Application: Driving Reciprocating Compressor for Atomizer

Project Actions Completed Motor Design review with RSN Motor Engineering 5/1 Completed Detailed Process Review with Grand Eagle 5/8 – (Fact Finding) Completed Initial Process Assessment 5/21 – (Research) Installed Telemetric Strain Gage on Rebuilt Motor – (Measurement) Compiled Motor Torque Curves – (Analysis of Findings) Concluded Compressor was Introducing Torsion Resonance – 6/3 Compressor Manufacturer Agreed to Install Fly Wheel – 6/12 Customer is Presently Running Compressors at 1170 RPM’s just below 1180

RPM threshold for resonance (1192 Full RPM).

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Public Utility Shaft Breakage Analysis

Shaft Breakage Extends at 45 DegreesIndicative of a twisting moment as opposed to shear

Sleeve Bearing Wear PatternIndicative of a extreme radial forces

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Torque Analysis Using Telemetric Strain Gage

Conclusions: - Torsional ResonanceCorrective Actions:- Operate below critical speed until flywheel is installedResult:- Resolved Customer Application Issue- Mitigated Warranty Exposure

Grand Eagle / Baldor- Torsional resonance issues resolved after installation of flywheel to critically damp system

Chart #1: Shaft displacement at full load and 1192 RPM run speed. Four Modes of displacement are present. (Full Spectrum)

Chart #2: Shaft displacement filtered to 4 times to demonstrate displacement frequency was directly proportional to four stage compressor action.

Chart #3: Shaft displacement filtered to 1 times to demonstrate shaft displacement frequency was directly proportional to any one stage in four stage compressor.

Chart #1:

Chart #2:

Chart #3:

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Coast-to-Coast Coverage