Hydraulic Oils – Care for its Cleanliness


One common problem which the shipboard staff experience with the hydraulic oil systems, especially the mooring winches and anchor/windlass hydraulic systems is – “Contamination and High Particle counts”.

Viswa Lab reports that almost 60% of the hydraulic oil samples received for routine lubricant condition monitoring suffers very high particle counts (or) contamination.  Though internal system wear and tear of running parts are one reason, another major contributing factor is contamination through the breathers and sounding pipes (if any).


Breathers on the storage or the expansion tanks may allow water to wick its way down the threads, contaminating the lubricant.  Other forms of contamination such as rust and wear particles can also develop around the threads of the sounding pipe or the breather pipe. Overtightening with a wrench may stop water ingression but can cause pieces of thread to spall off and fall into the lubricant.  Placing a small amount of thread sealant on all breathers using pipe threads will greatly reduce this risk.  Thread sealant will fill the air gaps, lubricate the threads and seal out the water.  Over tightening of the drain plugs, screws, filter material and rubber or other joints may also contaminate and give false indication and interpretation of the lubricant analysis.  It is for this reason, a trend analysis of the lubricants are done and a fresh/new oil is tested to compare the results.  High water % can also cause corrosion of internal tank parts and thus leading to increase in contamination levels.

One of the vessels experienced hydraulic pump failure as the system had almost 25% of condensate water.  The ship staff did not drain on a regular basis and this resulted in failure of the hydraulic pump.  The vessel had an arrangement to prime the emergency fire pump with a hydraulic driven priming pump.  Unfortunately the vessel did not had spares for the hydraulic pump to replace and make it operational.  Two important points to consider:

  • Water – to be drained regularly, at least before trying out the emergency systems every saturday (saturday safety routine)
  • Spares for critical equipment have to be carefully analyzed and such spares must be ordered and kept handy on board

There are many other factors which can lead to hydraulic oil contamination which is outside the scope of this write-up.  Below is an example of how Lubricating oils are stored on board a ship.  Though the drum may contain new oil, this does not mean that the oil will be low in contaminants.  Get your new fresh oil tested for contaminants.  Viswa Lab tests new/fresh oil at no extra cost when tested with other used oil samples.


Did you notice High Particle counts in your hydraulic systems?

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