In the past, ships had large crews with a fair proportion of them being engineers and technicians whose job it was to keep everything running. They did this by spending much of their time on board ship busily stripping down and reassembling all the various items of the ship’s machinery. Basically, implementing a system of Planned Periodic Maintenance (PPM) in an attempt to avoid costly breakdowns. However, not only is this approach needlessly costly, due to the time wasted stripping down perfectly functioning machinery, it can actually make matters worse by introducing faults during the process of stripping down and rebuilding a perfectly good machine.
Even more of a problem is deciding the correct PPM time intervals. Too short, means more wasted time and cost (and more potential for introducing faults) but not long enough means more unexpected breakdowns. In the case of a ship, breakdowns are not only VERY costly, but they can also be extremely dangerous. Think of a super tanker drifting onto the rocks!
These days, due mainly to increased automation, ships crews have reduced in size and PPM has largely been replaced by a system of Condition Based Maintenance (CBM). This approach relies on the fact that a machine’s condition (degree of wear) can be monitored by measuring things like the temperature and vibration levels of motor bearings. This way, machinery only needs to be maintained (stripped down) when its condition deteriorates beyond an acceptable level. That decision is based on recording and tracking changes in the machinery’s condition over time, i.e., TRENDING.
So how is this achieved in practice? Fortunately, a range of modern low cost, easy to use and highly effective CBM tools are now available. These include vibration analysers like the TPI 9080 Smart Trend Meter that is currently in worldwide use on board several hundreds of ships belonging to many different shipping companies.
In most cases, the ship’s engineers simply download a ‘route’ (a list of machines to be measured) to the 9080 from an onboard computer (PC) running the subscription FREE, trending software. The engineer then simply follows the ‘route’ taking the readings as instructed. After the readings have been taken, they are automatically uploaded (via USB or Bluetooth connection) back to the PC, where the all-important trend of the readings can then be seen in clear and easily understood graphs. The PC software will also flag-up any problems and can even send email alerts, all based on the internationally agreed (ISO) alarm levels for rotating machinery.
In addition, various expert system features are incorporated into the software, such as bearing quality assessment, which is achieved by analysing the frequency components of the vibration data and automatically identifying the classic ‘signatures’ associated with bearing wear. That way, it is very easy to monitor the health of a bearing simply by observing the level of bearing wear displayed on the trend plots.
Many of the shipping companies take things a stage further where, in addition to the ship’s engineers, readings are also monitored by shore-based marine superintendents, who are using the same PC software. Readings can be transferred between ship and shore in a variety of ways including email.
TPI 9080, which uses industry standard accelerometers and offers on-meter analysis for the detection of machine faults such as unbalance, misalignment, looseness and bearing wear. The equivalent intrinsically safe certified (IECEx, ATEX and North American) TPI 9080-Exoffers a complete Zone 1 CBM solution.
