Condition monitoring of Thrusters (Offline vibration measurements) - method to extend intervals of maintenance.

Condition monitoring is a next step from Planned Maintenance System, which mostly uses running hours of machines to plan their maintenance. Unlike the standard Planned Maintenance system, the Condition Monitoring is based on particular measurements which give actual condition of machine.

Many class societies as DNVGL, ABS, RINA etc. have rules that give possibility to postpone maintenance based on implemented Condition Monitoring - if the machinery condition according to measurements give positive results. Since maintenance costs of thrusters are crucial, the Condition Monitoring is very useful tool.

?Condition Monitoring of thruster is based on two methods:

• oil analysis of hydraulic and lubrication system
• vibration measurements (can be offline or online)

Before Info Marine Engineer visits the vessel/rig it is important to send all technical data of thruster including:

• Power of electric motor
• Revolution speed of electric motor
• Gear ratio of gearbox (number of teeth on each pinion is also very useful)                        
• Number of blades on propeller
• Types of bearings
• Cross section of gearbox where place of bearings nodes are seen
• Schematic of lubrication and hydraulic system

This case describes Condition Maintenance based on our portable device Marvib DC750 used for vibration measurements.

Installation

 Our visit starts with installation of metal points, indicating places of vibration measurements.

First, the surface is cleaned and degreased. It is to improve frequency response of accelerometers.

Fig.1 Cleaning surface

Fig.2 Cleaned surfaces

Metals point are glued by special acrylic adhesive.

Fig.3 Gluing stud point

On electric motor there are mounted 2-3 metal points on each bearing.

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 on below picture.

Fig.6 Vibration measurement points on thruster

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

Fig.7 Cabinet during making 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 cabinet and quality of installed sensors are checked by special instrument:

Fig.10 Checking cables, sensors and connections to Cabinet

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 

Crew members were trained with VMLab software, Marvib DC750, reports and feedbacks. The last step for our Engineer on board is to collect photos of sample points for lubricating and hydraulic system of thrusters. It is important to obtain documentation with pictures of real point together with indicated places on 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 send the data to laboratory. Oil analyses with recommendations are provided in response. Reports from oil analysis together with vibration measurements are crucial to make good diagnosis and, in case of any warning, good recommendation for Crew.

CBM implementation done

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

Fig. 15 Diagnostic report

Cooperation

Along with report, IM sends Feedback report.

Inside this file You can find recommendations from the report to the machinery that needs maintenance. Crew comments regarding repairs are welcome. In “Feedback Operation” last step is to send filled file with measurements taken after finished work. It will be used to confirm and improve our diagnosis.

Simple means Easy

We know how hard it is to keep all data in one place, so we’ll do it for you. For our Clients we have special app which in simple way shows condition of your Fleet.

Above, you see general condition of machinery divided into two groups: Critical Machinery (Outer Ring) and Rest of Machinery (Inner Ring). All of the Thrusters are Critical Machinery.

Inside App You can find a lot of information about all Your fleet or particular vessel. Main views prepared specially for You:

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

for individual platform:

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

All data is presented in best – graphical - way. Below are some examples: