Vibration Analysis of P - 29 Motor-Pump Assemblies

Transcription

1 Vibration Analysis of P - 29 Motor-Pump Assemblies Insight Project Date Dec 1 st, 2010 Prepared By Reviewed By Liyana (Jay) Jayathilake, P.Eng Lal Perera M.Sc., P.Eng Customer Contact Customer Order

2 SUMMARY Vibrations on P - 29 motor-pump assembly was monitored and analyzed. Casing vibrations on motor bearings are marginally high, but the shaft vibrations are low and acceptable. Continue operation of the motor but monitor the vibrations. If the vibrations increase withdraw and send it for overhaul Note: Only one proximity probe on pump inboard bearing is functioning. Correct at the earliest opportunity. Refer recommendations in the section 3.1.

3 CONTENTS Vibration Analysis Report Page 1. Introduction 1 2. Vibration Guideline Limits 1 3. Findings, Comments and Recommendations 2-3

4 1. INTRODUCTION The pump P-29 tripped due to high vibrations on outboard bearing as indicated on monitor panel installed on the unit. Plant personnel suspected that motor vibrations transmitted through the base and caused the pumped to trip. Insight Engineering Services was requested to analyze machine s vibration and determine the cause. Tests were performed on November 29 th, ZonicBook multi-channel data acquisition unit and CSI advance two channel analyzer were used to acquire the data. 2.0 VIBRATION GUIDELINE LIMITS 2.1 API Vibration Guideline Limits for overhung or in between bearing horizontal mounted pumps. Overall Vibration Levels Vibration Peaks at Discrete Frequencies Pump Bearings 0.17 in/sec Peak in/sec Peak Motor Bearing 0.10 in/sec Peak 0.10 in/sec Peak 2.2 API Vibration Guideline Limits for Vertically suspended pumps. Overall Vibration Levels Vibration Peaks at Discrete Frequencies Pump Bearings 0.28 in/sec Peak in/sec Peak Motor Bearing 0.28 in/sec Peak in/sec Peak 2.3 ISO Group 3 Vibration Guideline Limits for external drive machines Overall Vibration Velocity mm/sec rms in/sec peak mm/sec in/sec mm/sec in/sec mm/sec in/sec Above 7.1 Above 0.39 mm/sec in/sec Criteria Acceptable levels for a new unit that is set into operations. Continuous operation is acceptable. Periodic monitoring to assess the condition is recommended Acceptable for a limited period of operation. Plan for corrective work Danger, damage could occur at any time. Do not operate the unit. Correct the problem without delay

5 3.0 TEST RESULTS AND FINDINGS Casing vibrations on the motor were monitored. Highest vibrations showed in the horizontal direction and dominant peaks excited at 1x rpm order and at 120 Hz. Lubricating oil on motor bearings were changed and tests were performed. No significant change was observed and overall vibrations still remained marginal. Overall vibration levels are shown in table 1 and spectrum are shown in Appendix A. Shaft vibrations on the motor and pump remained low and acceptable. The vibrations on the pump base are low and acceptable. See appendix B. Figure 1:- The upper window shows the overall casing vibration levels and the lower window shows the vibration and the spectrum of the motor outboard bearing. (Red curve is horizontal, Blue is Vertical and Green is Axial)

6 Figure 2:- Upper window shows the overall vibration levels and the lover window shows the vibration spectrum of the motor inboard bearing. ( Red curve is horizontal, Blue curve is vertical and Green curve is axial)

7 Table 1 - Overall vibration levels of pump P-29 Point Point Descriptions Overall Vibration in/sec MOH Motor Outboard Horizontal MOV Motor Outboard Vertical MOA Motor Outboard Axial MIH Motor Inboard Horizontal MIV Motor Inboard Vertical MIA Motor Inboard Axial PIH Pump Inboard Horizontal PIV Pump Inboard Vertical PIA Pump Inboard Axial POH Pomp Outboard Horizontal POV Pump Outboard Vertical POA Pump Outboard Axial PCH Pump Center Horizontal PCV Pump Center Vertical Prox-Probe Vibrations mils MOX Motor Outboard X 0.85 MOY Motor Outboard Y 0.65 MIX Motor Inboard X 0.95 MIY Motor Inboard Y 0.95 PIX Pump Inboard X - PIY Pump Inboard Y 1.75 POX Pomp Outboard X 0.50 POY Pump Outboard Y 0.35

8 3.1 COMMENTS AND RECOMMENDATIONS Casing vibrations on motor bearings are marginal but the shaft vibrations are low. No immediate action required, continue the motor to be in service. If the motor vibrations increase and show an upward trend withdraw the motor from service and send for overhaul. The pump may have tripped due to a sudden spike or faulty signal of the proximity probe. Only one proximity probe is working on the pump outboard bearing. This should be rectified as soon as possible. 4.0 Data Vibration Tables and Spectrum Plots Appendix A Pump Assembly Vibrations and spectrums. Appendix B Pump Base Vibrations and spectrums.