Clearance-Sized Particles ("CSP")What Are Clearance-Sized Particles, CSP?
Particles in the oil film moving within the clearances between the moving parts are Clearance-Sized Particles, CSP. The majority of the clearances between the engines' moving parts are between 1 to 10 microns, hence, CSP are primarily in the 1 to 10 micron range. The CSP causes the majority of engine wear and friction. The reason that CSP are harmful is that that are small enough to enter into the clearances between the moving parts and large enough to be forced into contact with the surfaces of the moving parts, causing wear and friction. CSP have been called "liquid sandpaper" to describe the insoluble abrasive slurry of micro-particles, which is continuously re-circulated between the moving parts, causing additional wear and friction within the engine¡¯s moving parts, such as the piston rings and cylinder wall, rod bearings, and the piston pin bushings.
Illustrated below is a typical engine clearance. The size of the oil film between a cylinder wall and the piston ring is approximately 3 micron ¨C the size of bacteria. If the 3-micron oil film is not carrying any abrasive clearance sized particles, there is minimal wear. If the oil film is dirty, carrying CSP between these parts, significant wear and friction will be created.
As illustrated, the size of the particle is critical. A 20-micron particle will not cause damage because it is too large to enter the 3-micron clearance. A 0.01-micron particle is small enough to enter the 3-micron clearance but it is not large enough to wedge between the moving parts to cause wear. For the ring/cylinder 3-micron clearance, the most harmful CSP are the 2-3 micron particles. (Illustration courtesy of Noria Corporation.)
What are the Sources of Particle Contamination?
The three major sources of particle contamination are:
(1) Engine operation. All engines -- whether fueled by diesel, bio-diesel, LNG, CNG, or gasoline -- create CSP through the movement of engine parts, creating wear metals, which build up in the oil film. Abrasive CSP is continuously re-circulated, producing more wear. The more CSP, the fasters the parts wear.
(2) Fresh oil. Even fresh oil contains particle contamination, especially when the oil is stored in a central tank and pumped through long hoses into the crankcase. To the naked eye, the fresh oil¡¯s yellowish-green or golden-brown appearance looks "clean." Since the lower limit of human vision is approximately 40-50 microns, the harmful bacteria-size 1-10 CSP microgrit is invisible.
(3) The air. There are invisible CSP particles in the air, such as the silicon dioxide particles in ash from smoke stacks where coal is burned. Particle contamination is especially dangerous in high dust environments. Silica particles are extremely harmful because they are harder than engine parts. High levels of CSP silica is a major cause of wear and engine damage.Do Full-flow Filters Remove CSP?
No. Engines have at least one full-flow filter. It operates in-line with a high oil flow rate, typically 12 to 15 gallons per minute at 170-200 degrees with 25 - 65 psi. The full-flow filter is directly between the oil pump and the lubricated parts. All the oil from the oil-pump must pass through the full-flow filter before it enters the engine to lubricate and cool the rapidly moving parts. To avoid starving the engine of lubricating oil, the filter media must be relatively porous and is usually made out of synthetic materials. If the full-flow clogs, the engine¡¯s bypass safety valve opens, which take the full-flow filter "off-line" to allow all the oil to flow to the engine without passing through the full-flow filter. Of course, when the safety valve takes the full-flow filter "off-line," there is no engine oil filtration. Full-flow filters can filter down to approximately 30-45 microns with absolute efficiency (¡Ư 98.7 %) but can not prevent the buildup of 1-10 micron contamination.Do Microfilters Remove CSP?
Yes. The design of the proprietary ECO MicroFilters device is different that the full-flow filters. The microfilter element contains large quantities of very dense, media and a gradient-flow structure. It operates at approximately 0.2 -.4 GPM. The ECO MicroFilters are not in-line, that is, it is not directly in the path between the oil pump and the lubricated parts. ECO MicroFilters operate in by-pass mode, returning the clean oil to the crankcase.Does CSP Shorten Engine Life?
Yes. General Motors published a SAE report on the relationship between small micron particle contamination and engine life. The test evaluated the impact of cleaner oil on engine life. The GM study reported that when the lubrication oil is filtered down to 7 microns, engine wear is minimized and relative engine life is more than five times longer. The following graph illustrates the relationship between particle contamination and engine life:
What can I do?