Detecting Bearing Wear on Steering Gear Motor Using Enveloping Signal during Vibration Measurement on Vessel Board

During a routine inspection of our vessel, we identified several vibration issues in various machines. One of these issues involved significant wear on the DE (drive end) bearings of the steering gear motor, which we discovered through vibration measurements.

Our Service engineer performed vibration measurements on the steering gear motor, which is crucial for steering the ship. Below is the Steering gear hydraulic pump motor (52 KW).

Fig. 1 above shows the electric motor driving the hydraulic oil pump of the steering machine

This motor is an important part of the ship’s steering system and needs regular maintenance to work properly.

Inspection Details and Findings

The vibration overall and bearing envelope numerical values seem normal, values from measurement points marked by arrows didn’t cross limit as is shown in the picture (2).

                                                           Fig. 2 The image above shows the vibration values measured according to ISO standards.

However, a more detailed analysis using the FFT (Fast Fourier Transform) envelope spectrum revealed unusual vibrations The analysis revealed peaks from BSF- Ball Spin picture (3), leading us to the recommendation of change bearing.

                                                   Fig. 3 The image above shows the FFT bearing envelope spectrum of the drive end damaged bearing

After taking the motor apart, we found the drive end bearing was significantly worn, confirming the results of the vibration analysis.

Visual Evidence of Bearing Condition

The fourth image shows the wear on the bearing outer race with visible scoring and discoloration as you can see the race isn’t very wear. That is why the bearing envelope and overall values weren’t high. For sure it would quickly get worse considering what the inspection also revealed.

                                                                                       Fig. 4 The image above shows bearing outer race


Bearing Balls After removing the outer race

The last image shows the disassembled bearing, giving a clear view of the ball bearings. Notice the chipping on the bearing balls (picture 5), which is a clear sign of damage. This detailed look emphasizes the need for regular inspections and the effectiveness of vibration analysis in catching these issues early.

                                                                                       Fig. 5 The image above shows bearing ball damage


The vessel replaced the worn bearings with new ones. Reassembled and tested the steering gear motor again didn’t show signs of wear.

                                                         Fig. 6 The image above shows the FFT bearing envelope spectrum of the new drive end bearing


Inspection of the steering gear motor highlighted the importance of detailed vibration spectrum analysis. Initial vibration readings seemed normal, but a closer look using FFT (Fast Fourier Transform) analysis revealed unusual patterns, leading us to discover significant bearing wear.

This shows that basic vibration meters and checks can miss not developed issues. Detailed spectrum analysis can uncover problems early. This proactive approach helps prevent failures and extends the life of our equipment.

By using advanced tools like FFT analysis, we keep ships and machine parks running safely and efficiently, ensuring the reliability of our fleet and the safety of our crew.