Rotating Machinery Modal Testing

Mechanical Solutions, Inc. uses the latest hardware and software combined with the Time-Averaged Pulse (TAP™) technique to quickly determine possible modal problems. The TAP™ technique allows MSI to test your equipment without shutting down any equipment! Modal visualization and Structural Dynamic Modification (SDM) software are utilized to determine the best corrective action. MSI couples real world modal test data with Finite Element Analysis (FEA) to provide calibrated analytical models which can be used to perform "what if" analyses.

Components Analyzed:

• Aeroderivative Gas Turbines
• Axial Blades
• Centrifugal Impellers
• Gas Turbine
• Industrial Fan
• Machinery Rotor Drivetrains
• Multistage High Pressure Compressors
• Reciprocating Pumps
• Screw Pumps
• Spark and Diesel Engines
• Steam Turbines
• Vertical Turbine Pumps

• Multiple Bruel & Kjaer spectrum analyzers including a 7 channel Pulse system
• Multiple Data Physics ACE spectrum analyzers
• Various modal impact hammers

• ANSYS
• Bruel & Kjaer Pulse Software
• Data Physics ACE Software
• ME'ScopeVES
• NEiNastran

Use of Experimental Modal Analysis (EMA) to Support Pump Retrofits

MSI was contracted through a major OEM to perform their unique experimental modal analysis on three 30 year old, reliable, packed-stuffing box, multistage barrel pumps in critical refinery process (Benzene) service. Upgrades from the packed-stuffing box to mechanical seals were required due to new OSHA requirements for pumpage containing benzene.

The user and OEM had previous bad revamp experience when up-front modeling was not performed. TAP™ was performed on the operating pumps to determine existing rotor and structural critical speeds and damping coefficients. The information was used by the OEM to accurately calibrate their "as-built" Finite Element Analysis (FEA), which was then extrapolated to calibrate the "revamped" models. The resultant upgraded pumps have performed very successfully and additional knowledge was gained which improved typical assumptions made when performing FEA.

The methodical approach described has helped users meet new federal regulation ("Process Safety Management - OSHA 29-1910-116") requirements when performing turbomachinery upgrades.