Use of Non-Conventional Sensors for Monitoring a Rotating Machinery Loop: A Road Map
When a machinery structure vibrates laterally or deflect in their coupled rigid body modes, then it deviates from expected modal parameters (basically the structural deflections) during operating conditions. The structural deflections during such events can be defined as strain percentage and then can be processed as electrical analog signal. The proposed article explores how different types of strain gauges and load cells can be employed to detect such deviations in expected modal parameters of machinery structures and enable us to correct the anomaly. FEM software calculates the displacements and reaction forces at the nodes. This is later used to calculate the strains at places away from nodes.
If the finite element model of subject base frame is constructed with idealized condition and if forecasted strain maps or deflections of load bearing structural elements at operating frequency of machine, this can provide a baseline value of expected behavior of machine.
If the strain gauges are attached at various strategic places of load bearing structural element, the same model can be validated or refined without use of any modal analysis (OMA) or an operational deflection shape (ODS) analysis.
The use of strain gage can be put in service to detect superficial / benign / real cracks on concrete foundation of rotating machinery as well.
With known loads applied, the strain gauge can provide FFT spectra and then FRF plot can be generated. If calibrated load cells are attached at strategic positions, then also an FRF spectra can be generated. This can be helpful to validate the FE model. This FFT spectra can even provide a mode shape of structural deflection. This can be helpful to validate the FE model. This approach can revolutionize the experimental and operational modal analysis procedure we normally undertake using number of accelerometers and multichannel data acquisition systems.
With proper use of various types of load cells such as sandwich type compression load cell, it is possible to detect soft foot caused by improper milling at machine test bed itself.
The combination of these two devices along with washer type calibrated load cells if placed on strategic location of a flange connection of equipment nozzle , we can measure machinery casing nozzle strain due change in bolting loads at piping, thermally induced piping strains near struts and position of hanger supports. The paper shall also deal with aspects of signal processing to generate data.
With this road map ,a sensor can be developed by integrating various sensors like piezoelectric, strain gauge and capacitive transducer. This type of combination of sensors if connected to wireless communication network can provide online dynamic data even in a cell phone device.
With advent of biomechanical engineering wearable devices which show actual movement of hand / palms and same can be used to visualize the movement of critical structural elements with wearable strain gages .This technology if incorporated in rotating machinery monitoring , it shall enable the engineer of reliability team to have a global picture of complete unit and its dynamic behavior . Based on mode of rigid body motion as visualized , whether translational or rotational, a corrective action can be planned accordingly.
Use of Non-Conventional Sensors for Monitoring a Rotating Machinery Loop: A Road Map
Category
Poster Presentation
Description
Session: 17-01-01 Research Posters - On Demand
ASME Paper Number: IMECE2020-25194
Session Start Time: ,
Presenting Author: MANTOSH BHATTACHARYA
Presenting Author Bio:
Authors: Mantosh Bhattacharya PETROFAC