Ship Machinery Condition Monitoring (Marine Machinery Condition Monitoring)

Reliability, availability, zero incident, etc are words taken for granted in land based industry. Marine machinery systems are no different from those found ashore. Why is it then that land based industries have made such strident progress to a stage where condition based maintenance is the norm rather than the exception? Why is it that maintenance on board ships is still either based on time or running hours and not based on condition?

The most obvious reason that predictive maintenance or in other words condition based maintenance has not been widely adopted on merchant ships is due to the physical separation of the ship from the condition monitoring technology and associated expertise.

VIBRATION
Several ship owners have invested in expensive vibration monitoring systems. However, the consensus seems to be that without an external expert analysing the data, such systems rarely prove useful. Ship’s engineers are not qualified to interpret such data and quite often fail to detect the problem before it is too late. Retrospectively looking at maintenance costs, the ship owner then finds that the same amount of maintenance work is being carried out on the assets and so the benefit of the system is not realised. The ship’s staff, finding that the equipment does not really benefit them, lets it fall into disuse. This is familiar story to many ship operators. The goal of attaining enhanced reliability and availability of the ship is not in any way made easier.

On the other hand, when ship owners employ a reputable external consultant to implement and manage the vibration monitoring system, the benefits are almost immediate.

Vibration monitoring of ship’s machinery systems is again fraught with the danger of misinterpretation. Readings taken while the vessel is under ballast conditions may differ from readings taken during loaded passage. Readings taken in port will most definitely be different from readings taken at sea. Such complexities don’t exist ashore. So it would be unwise to transplant the knowledge from land to sea. One has to be aware of the difficulties and perform intelligent analysis of the data.

Structural flexure is another major problem at sea. It is often observed that weak or deteriorating machinery structure causes the entire machinery with the foundation to go into resonance. Corrosion of the stool plate on sea water pumps is another main cause for concern. Sea water leaking from mechanical seals or glands flow past the bronze alloy casing and on to the steel stool causing accelerated corrosion due to the galvanic action

Thermal imaging
In the past thermal imaging cameras were so expensive that ship owners could not justify the purchase of one camera for each vessel. However, the costs have been dropping considerably and it is now possible to purchase a camera of reasonable quality for under £ 5000

For an informal discussion, contact:
Dr Gopinath Chandroth
Mobile: +44 777 073 8234