SAVE OIL & FILTERS, SAVE TIME, SHRINK COSTS, GROW PROFITS!
Soot Can Cause Premature Wear
Professional Skipper Magazine Issue 46 Jul/Aug 2005
How many of you have problems with soot? Does your oil turn black straight away and look like it needs another change almost immediately? What about your oil service intervals? How long are they, and what should they be?
If you're doing used oil analysis, are the results telling you that your oil is not fit for further use, even before it reaches your "manufacturers recommended oil service interval"?
To comply with emission regulations modern high speed diesel engines are forbidden to put any combustion residue out through the exhaust. Engines still produce combustion residue, but now the only place left to deposit the residue is in the oil.
High levels of soot in your oil can cause many problems, not least with the oil itself. Soot is an oil thickening agent and as such can increase the viscosity of the oil to such an extent that it can cause major damage to your engine. Blocked oil galleries, restricted flows, plugged filters and the like can result in a lack of lubrication to your engine, particularly during start-up when the oil is cold.
Soot is also a major factor in component wear. Your typical primary soot particle ranges in size from 20 to 40nm or around 0.04 of a micron (µm). However, when these primary soot particles agglomerate together they can form much larger particles of around 0.05 to 2µm depending on the engine type and oil additive chemistry.
While the carbon in itself is not that abrasive, when the soot particles join with other elements like dirt (silicon), fine wear-metals or even the ash from the burnt off oil, they become very hard and abrasive thus causing premature wear to take place.
One advantage of today's oil is that part of the additive package employed is designed to keep as many of these contaminate/soot particles apart for as long as possible, thus stopping them from agglomerating and causing catastrophic wear problems. Never before has the need for quality sub micron filtration been so necessary to maintain engine life.
The trend by lubricating oil manufactures today is to try and extend oil life by holding higher concentrations of contaminant and soot in suspension (typically up to 10%). It has been reported that contaminant particles, which are of a similar size to that of the oil film thickness, generate the most wear. Since the trend in oil viscosity is downward (for reasons of fuel economy), the oil film thickness is also reduced, therefore reducing the critical contaminant size is a must.
Your main full flow oil filters are normally around 40 µm. Some may also have an internal bi-pass of around 20 µm. What this means is that all particles above 20 µm will be removed from your oil until either the filter plugs or is blocked completely.
So what about those soot and contaminate particles below 20 µm I hear you say? Well there are only a few pieces of equipment or filters on the market today that can remove these very fine contaminate particles efficiently. One of the best that I've come across is the centrifugal oil cleaner by Mann+Hummel. These centrifuge units are mounted beside the engine, set-up in a by-pass loop and best of all they are non-selective in the size of the particles they remove. That means they have the ability to remove all particles down to and including less than one micron in size.
The centrifuge requires only the excess unused pressure from your oil pump to operate and draws no more than 10% of the available oil. The pressure of the oil from the pump opens the cut off valve and allows the oil to pass through the rotor.
It's this action that causes the rotor to spin fast enough to create the g-forces necessary to separate the soot particles from the lubricating oil. The oil is then dropped back into the sump with the aid of gravity, leaving the soot and other contaminate particles tightly packed in the rotor.
From there it's a simple 10 to 15 minute job to dismantle the unit, remove and discard the carbon from the rotor and clean the parts ready for reassembly.
Depending on the pump's output and the size of the unit, the engine sump capacity can be turned over as often as 20 times in an hour. The more the oil passes through the centrifuge the cleaner the oil becomes. If the oil remains clean the additives in the oil have less work to do. This results in the additive package remaining stable for longer in the oil.
It's about here I hear you ask if the additive package remains in the oil longer and there is little or no soot or wear-metal particles floating around in the oil, can you extend your oil service intervals? Absolutely! The whole purpose behind the design of the centrifuge some 50 odd years ago was to offer better protection to the engine while extending the life of the oil.
As an example, one of my used oil analysis customers is using a standard multi-grade mineral 15w 40 oil. In most engines this oil could be expected to do around 250 hours. However, with the use of the oil analysis we have seen that the engines on this vessel, which are equipped with centrifuges, are quite capable of doing around 800 hours plus between oil changes without a problem.
Extended oil service intervals offer a range of advantages which lead to the overall lowering of your operational costs.
For instance, less oil and filters used (including top-up), less waste oil to remove and reduced downtime for servicing. With the use of a centrifuge the whole-of-life engine costs are substantially reduced, as the engine's component life becomes more durable as a direct result of the cleaner oil. This equipment will provide you with one of the best returns on investment that you could ever spend. And that's a promise you can hold me to!
52 engine manufacturers world-wide endorse or support fitting of the Mann+Hummel centrifuges.If you would like more information on the M+H Centrifugal Oil Cleaners don't hesitate to contact me. I will be only too happy to help your business reduce costs.
Written By Kelvin Hieatt
Marine Diagnostics Ltd
