The condition of your system should not be judged by a single number. Oil analysis sensors and tools like online particle counters are not completely reliable in verifying the efficiency of your oil filtration system. Most oil companies already know this as they have experienced professionals that use a variety of tools to assess all the information that is carried on oil sample.
This is common knowledge because engineers know that clean oil can reduce operation and maintenance costs which amount to significant cost savings. By the use of efficient oil filters and appropriate tools companies reduce their costs associated with component wear, downtime and oil replacement.
To exemplify this, let’s consider that the online particle counter that remotely monitors particles in your hydraulic oil is showing the ISO code of 16/14/11, which means that the system is working perfectly; but this is not necessarily true. The online particle counter can only detect particles that are 1 to 200 microns in size; hence it cannot detect particles that are very large or very small (submicron particles). It is also unable to detect any installation fault in the counter, if additives have depleted, or if oil viscosity is off. Additionally, the online particle counter cannot distinguish the oil smell, colour, check acidity, oxidation, varnish, demulsibility (water separation efficiency), foam, or problems with air release. Contaminants can also get into the system with improper breathers. It is very important the oil tanks are sealed with correct specification of oil breathers.
The filter efficiency of your lubrication system is best judged through a sample because it holds a lot of information about your system’s condition and your oil’s properties. Following are some on-site methods that can help you process this information and take corrective actions without the use of a laboratory.
Examine the colour of your oil and compare it with new oil. If your oil is oxidized, it will turn from amber to dark brown. If your oil has turned black, it indicates micro-dieseling due to entrained air or soot from combustion byproducts.
Check for any large wear particles (greater than 100 microns) that appear as shiny or black sediment and check the suction side of the system pump for air leaks. Analyze if the water level is above 1,000 parts per million by using the crackle test (oil drop on a hot plate).
Shaking an oil sample will show the air release and foaming properties of the oil. Check the speed of air bubbles rising through the oil and foam on the surface. If the oil contains particles, water or varnish, it will hold the air inside your oil for a longer duration of time and may create foam. If you encounter this issue, do a lab-test on the air-release properties of your oil.
Cold oil doesn’t dissolve varnish and water as easily as warm oil so place your oil sample in refrigeration overnight. Use a white paper with black lines and a powerful light to detect varnish and water dissolved in your oil because it will be hazy and unclear. This varnish and water enters the cold machine areas and gives rise to corrosion and jerky valve movements. It can also lead to damage to valve spools which are very sensitive to fine contamination.
A quick way to detect iron wear particles is to break off a fragment of your used filter element and use a strong neodymium magnet to lift that piece. If you are able to lift that material, you have a machine wear problem. Iron particles are usually magnetic, they can be as shiny as silver, black like soot or brown like rust. If iron is found in your filter or the oil, do a particle quantifier or wear particle concentration test in a lab.
Check your used filter for shiny metal wear particles like iron or brass. Break off a piece of the used filter element which should have a multi-layer buildup on one side and clean on the other side. If the filter is not clean on the other side, it has not performed its intended function. Use a USB microscope that magnifies 200 to 400 times; it can reveal the size, shape and colour of the captured particles.
The blotter spot test is used to reveal glycol, soot and fuel dilution. All you need is a drop of sample on chromatographic paper. Excessive soot contamination depletes the dispersant additives, which forms a black spot on the paper. If you are using good quality additives, you will see a dark grey colour on the paper. If it becomes a black, sticky paste which does not move across the paper due to its sharp edges, it has glycol.
In conclusion, there are numerous tools and techniques to easily get a lot of information about the state of your oil and to utilize this information for taking corrective actions. Most of your operating and maintenance costs can be greatly controlled if you rely on these tools and techniques to assess the efficiency of your oil filtration system.