Condition Monitoring of Thrusters (Offline Vibration Measurements) – method to extend intervals of maintenance.

Condition monitoring is the next step from the Planned Maintenance System, which primarily relies on machine running hours for maintenance scheduling. Unlike the standard system, condition monitoring uses specific measurements to assess the actual condition of the machinery.

Many class societies such as DNVGL, ABS, and RINA allow postponing maintenance based on implemented condition monitoring if the machinery condition, according to measurements, shows positive results. Given the significant maintenance costs of thrusters, condition monitoring is an invaluable tool.

Marine Condition Monitoring

Methods of Condition Monitoring:

Condition monitoring of thrusters is based on two primary methods:

  • Oil Analysis: Assesses the hydraulic and lubrication systems.
  • Vibration Measurements: Can be performed offline or online.

 

Preparations for Condition Monitoring:

Before an Info Marine Engineer visits the vessel or rig, it’s crucial to send all technical data of the thruster, including:

  • Power and revolution speed of the electric motor.
  • Gear ratio of the gearbox (number of teeth on each pinion is also helpful).
  • Number of blades on the propeller.
  • Types of bearings.
  • Cross-section of the gearbox showing bearing nodes.
  • Schematic of lubrication and hydraulic systems.

 

Our portable device, Marvib DC750, is used for vibration measurements.

The process begins with installing metal points for vibration measurements, ensuring the surface is cleaned and degreased for optimal frequency response.

Marine Condition Monitoring
Fig.2 Cleaned surfaces

Metals points are glued by special acrylic adhesive.

Marine Condition Monitoring
Fig.3 Gluing stud point

Install 2-3 metal points on each bearing of the electric motor.

Marine Condition Monitoring
Fig.4 Electric motor

Red covers were applied on each metal point to avoid contamination in threads. On the red covers and next to them there were marked names of points.

 

On gear parts there are installed metal points with accelerometers (it is not safe to take measurements due to rotating shaft), which have been connected to cabinets.

Fig.5 Gear part

All mounted measurement points are presented in the below picture.

Fig.6 Vibration measurement points on thruster

The signals from gear parts are lead to the cabinet installed by Info Marine.

Fig.7 Cabinet during making the connection

Fig.8 Closed cabinet

Fig.9 Cabinet inside

 

Inside cabinet there were installed selector and BNC connector where the Marvib DC750 is connected.

The connection to the cabinet and quality of installed sensors are checked by a special instrument:

Fig.10 Checking Cabinet inside

Crew training was carried out after completed works of vibration system installation.

Crew members were testing electric motors and gear parts of thrusters.

Fig.11 Training Crew

Fig.12 Training Crew (2)

Crew members were trained with VMLab software, Marvib DC750, reports and feedback.

 

The last step for our Engineer on board is to collect photos of sample points for the lubricating and hydraulic system of thrusters. It is important to obtain documentation with pictures of real point together with indicated places on the scheme.

Oil analysis

Diagnostic reports are based on vibration data and oil analysis data collected every month. The oil is taken from below sample points.

Fig. 13 Sample point scheme

Fig. 14 Sample points

Once a month crew collects oil samples and sends the data to the laboratory. Oil analyses with recommendations are provided in response. Reports from oil analysis together with vibration measurements are crucial to make a good diagnosis and, in case of any warning, a good recommendation for Crew.

CBM implementation done

The crew only needs to measure all thrusters once a month. The Crew sends measurements with oil analysis, based on which the IM office prepares the report. As a result, the condition of the machines and the overall condition of the platform are known. The report contains General information about the platform, measurement specifications and standards, information about measurement equipment and conditions. The results are presented in tables with overall velocity RMS and envelope values. Below the tables FFT graph for points with the highest values are presented.

Fig. 15 Diagnostic report

Cooperation

Along with the report, IM sends feedback based on condition monitoring.

 

Inside this file, you will find recommendations from the report for the machinery that needs maintenance. Crew comments regarding repairs are welcome. In the “Feedback Operation,” the last step is to send a filled file with measurements taken after completing the work. This information will be used to confirm and improve our diagnosis through effective condition monitoring.

 

Simple Means Easy with Condition Monitoring:

 

We understand how challenging it is to keep all data in one place, so we’ll do it for you. Our special app simplifies condition monitoring by showing the condition of your fleet in an easy-to-understand format.

You can see the general condition of machinery divided into two groups: Critical Machinery (Outer Ring) and the Rest of Machinery (Inner Ring). All thrusters are categorized as Critical Machinery.

 

Features of the Condition Monitoring App
Inside the app, you will find comprehensive information about your entire fleet or specific vessels. Main views include:

  • Action required
  • List of machinery with alerts
  • Summary of machinery condition
  • Financial statistics

 

Individual Platform Monitoring
For individual platforms, the app provides:

  • Summary reports
  • Detailed reports
  • Machinery trends
  • Feedback reports
  • Surveys done

All data is presented in the best graphical format for easy interpretation. Below are some examples:

Marine Condition Monitoring

Marine Condition Monitoring

Marine Condition Monitoring

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