Marine Engines are one among the most critical mechanical structures that is put to operation for prolonged hours at Green Sea’s. Often on board the ships it is quite difficult to understand the problems faced. Some of the problems include engines failed to kick start, speed not picking up, abnormal and unusual noise heard so on and so forth.
Challenges faced due to ship maintenance and engine condition have increased manifold times, especially in the midst of many new regulations and deadlines the Seafaring community is facing these days. Sometimes the regulation and mitigation measures such as switching over to Low sulphur etc can consume most of their time, engine health check gets ignored.
One of the two vital lubrications of a marine slow speed engine is the “Liner lubrication”. It enables to assess the Engine internals just by skimming through the test reports. Hence the Liner lubrication becomes very vital in understanding the overall Engine condition.
Challenges come across by Liner Lubrication:
Slow speeding was introduced by Maersk as a solution to conserve fuel as the fuel prices were skyrocketing in the past years. Mega container ships started sailing below 22 knots to conserve fuel and even few ships started with super slow steaming by operating below 18 knots speed. As this new solution was introduced it came packed with new set of problems. The problem of cold corrosion popped up due to the low operating temperature where Liner surface got affected.
There is another incident which affected the “Liner lubrication”, it’s the frequent changeover from High sulphur to Low sulphur fuels in order to comply with the emission regulations. That resulted in additional impact on the Liner lubrication as the changeover from High TBN Cylinder oil to Low TBN is mandatory.
Given that all of the above challenges are a daily reality for ships the ship owners and operators has to frequently evaluate the engine condition and ensure its wellbeing.
How to achieve Engine wellness?
One way to determine the engine health is by periodically testing the samples got from under piston space. This sample can throw some detailed info of the wear and tear of the engine and helps us in understanding the issues prevailing and even the hidden ones that are about to strike.
Scavenge drain samples furnish the following inputs:
In a way the Tip to Toe test can be equated to the cylinder head to sump test that can diagnose and predict all existing issues or expected potential issues that can be predicted. The Liner lubrication analysis helps us to understand all those issues in a single test. In a way the Cylinder Liner Lubrication test report provides a proactive intelligence.
Following are the properties of oil that will enable us to understand the prevailing issues in two strokes slow speed Main Engine:
Reserve BN and Iron (Fe)-The most important parameters that will enable to understand the complete wear of Liner and Piston rings. The Liner surface and Piston rings are subjected to scuffing primarily either due to over Lubrication or Starvation. Eventually the above said two phenomena will result in scuffing between Liner and Piston rings.
The engine wear due to the scuffing will be clearly exemplified in a report by Iron (Fe) values. Not only the wear is notified but also the reason for it such as Fe is inadequate or adequate will be notified with clarity by reserve BN inputs.
Thus based on the above inputs the Engineers can decide whether to increase or Optimize the feed rate.
In most cases, in the recent days, instead of starvation there is a pile up of alkaline deposits due to excess lubrication is witnessed.
As we all know that Cylinder oil is the most expensive oil, excess lubrication is going to increase your OPEX.
Liner lubrication will enable to understand and enhance in optimizing the overall spend.
Appropriate overhaul or replacement of Liners and Rings during a recent overhaul can also be confirmed by elevated iron values during the running in phase. Thus, a holistic view of the overall Liner and Cylinder condition can be found.
Engine parts with defects and other issues ascertained: Overall issues with Liner lubrication and Cylinder oil condition can be identified.
Copper and Chromium:
Copper and Chromium wear reflects the wear due to piston ring coating. Also, again help in confirming the scuffing between Liner surface and Piston rings.
Engine parts with defects and other issues ascertained: Piston Rings.
Phosphorous and Zinc:
High Phosphorous and Zinc values in the drain samples indicate the stuffing box leakage. This gives clarity for the Engineers to check the stuffing box ring clearances that will allow in revealing if any deviation present from the actual. If found to be worn out can be replaced to avoid system oil contamination with Cylinder oil or vice versa.
Engine parts with defects and other issues ascertained: Stuffing Box ring Clearances.
Vanadium and Nickel:
Vanadium and Nickel are the most vital parameters that exemplifies increase in Blow past between the Liners and Piston rings. Either due to the end of service life or due to the influence of other factors such as scuffing that arose because of the wear which leads to the increase in the clearance between liner and piston rings. Eventually Blow past of burnt residues or unburnt Fuel oil resulted.
Blow past of the Fuel has the most serious consequences as it reduces the Flash point of the System Lube oil by contamination. Other major consequences which includes the increase in oxidation, sulfation. This inflation of the later said properties of oil will effectively affect the life line of Lube oil such as Viscosity, Reserve BN. In due course this will affect the load bearing capacity of the Lube oil film and end up leaving an impact by instigating the wear of Bearings and Shaft due to friction between the moving parts.
Not only increase in Liner and Piston rings are ascertained but also the Leakage due to the Fuel injectors and Fuel Pump can be found by Vanadium and Nickel.
Engine parts with defects and other issues ascertained: Wear of Liner, Piston rings, Leaky Fuel injectors, Leaky Fuel pumps, Poor quality fuel.
Water and Sodium:
Water and sodium also come as an integral part as vanadium and nickel. Water presence in the cylinder oil either by contamination or excess condensation in the storage tanks can be confirmed with high water and sodium values. High water presence also indicates the choked water scavenge drain pipes.
Engine parts with defects that can be ascertained: Choking of scavenge drain Tubes
pH is yet another vital property of oil that will enable in identifying the oils acidic or basic nature. It will again help to ascertain the feed rate whether it need to be optimized or it needs to be increased. Ph will also help to reconfirm the reserve BN of the oil. If low Ph is found then wear due to the acid erosion need to be immediately examined.
Engine parts with defects that can be ascertained: Liner Quills.
Aluminium and Silicon:
Fuel presence or leakage can be adjudged again with the help of the high Aluminium and Silicon presence which actually indicates the catfine present in the fuel oil that has found its way in to the Scavenge drain. Fuel oil with High Catfines can also be explored by testing the scavenge drain oil.
Engine parts with defects that can be ascertained: Leaky Fuel injectors, Leaky Fuel pumps.
Particle quantifier is an intense test analysis that will aid us to understand type of wear and quantify wear whether it is substantial or menial.
Wear of Cylinder liners can be segregated into Abrasive and Corrosive wear. As corrosive wear is non-Ferrous in nature since Particle quantifier is a magnet based test analysis, Abrasive wear which is ferrous in nature can be easily found by the analysis. Thus, narrowing more specific to the type of wear can be made available in scavenge drain analysis.
Engine parts with defects that can be ascertained: Liners, Piston rings.
Apart from the above, various other prevailing issues that exist or expected to arise can be proactively disclosed by Liner lubrication. Thus, Liner lubrication is of paramount importance which paves way in understanding the Engine overall health condition.
Viswa Lab offers a comprehensive package of Scavenge drain Analysis.
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