Filtration: The pill for cleanliness
External contamination of diesel fuel reduces filter life, diminishes fuel life and can cause premature fuel component failures.
Failure to maintain good housekeeping practices on fuel products will eventually result in diesel engines encountering problems caused by contamination that occurs in the fuel distribution system.
The main factors associated with poor quality fuel are often related to particulate and water contamination.
The Caterpillar Diesel Fuel System Care stated that, “Ninety percent of diesel troubles are due to dirt or water in the fuel. For successful operation it is necessary that these impurities be kept out of fuel”.
This statement was chronicled in 1931 and remains as applicable today (if not more so) for technologically advanced engines.
High Pressure Common Rail (HPCR) fuel systems require even more stringent fuel cleanliness levels.
This is due to the increased sensitivity of these systems to small particulate contaminants especially under very high pressures of up to 2500 bar.
The World Fuel Charter (WFC) 2019 and most OEMs suggest a fuel cleanliness level of 18/16/13 as per ISO 4406 from the fuel station nozzle into the equipment’s fuel tank.
Thereafter the on-board fuel filtration system has a chance of filtering the fuel to the desired cleanliness level at the injectors.
Cummins suggests in its service bulletin 3379001 that if the fuel does not meet the ISO cleanliness code of 18/16/13 then additional filtration must be applied before the fuel is delivered to the equipment’s fuel tank.
In addition to ISO 4406 fuel cleanliness code requirement, it may come to pass that OEMs stipulate a minimum mass (milligram) of particulates per litre of fuel.
Engine and injector designs are changing to meet more stringent emission standards. The progression to engines requiring higher fuel pressures achieved through tighter tolerances has further highlighted the need for filtration to remove small particulate contaminants so as to prevent injector and pump wear.
The unwanted particulates in diesel fuel can serve to increase fuel pump wear.
In addition, due to the high fuel pressures, these particulates can act as a projectile within the fuel system leading to increased injector nozzle wear resulting in reduced combustion efficiency.
Failure to support and maintain good housekeeping practices on fuel products will ultimately result in diesel engines encountering fuel distribution system problems.
Frequently, improvements in fuel cleanliness can result in the following benefits:
- Extended component life
- Improvements in fuel economy
- Increase in engine power
- Reduction in emissions
As fuel contamination levels decrease, the planned “runtime to end of pump and injector life” increases dramatically.
Filtration of diesel fuels will require careful balancing between the cost of removing contaminants during the fuel distribution process and the cost of achieving the required cleanliness levels at dispensing as stipulated by OEMs, as well as the costs involved with servicing and lost production as a result of injector and pump failures from particulate contamination.
Simple house-keeping practices such as use of effective and efficient breathers and daily water drain off procedures of bulk fuel tanks will also assist.
Other options may include:
- Infrastructure changes on bulk tanks to include floating suctions to avoid sucking diesel fuel at or near the bottom of the bulk fuel tank
- Use of receiving vessels to allow adequate settling time
- Kidney loop filtration
Similarly, for oil lubricated compartments, component life can also be increased as a result of improving lubricant cleanliness.
Contamination is often overlooked when considering why premature failure occurred or why lubricant life has been diminished.
The two primary external contaminants of oil are dirt (environmental dust) and moisture.
If the atmosphere within which equipment is working is contaminated, then there is every chance that the oil within the equipment is also contaminated.
Particulate contamination inside an operating system will speed up wear generation which only exacerbates or compounds the situation, that is, wear generates wear.
These contaminants and wear metals only serve to damage or prematurely wear working parts within a component and act as catalysts in degrading the lubricant through oxidative processes.
These contaminants that prematurely wear and reduce equipment reliability can, in fact, be successfully controlled and managed with improved storage and dispensing of lubricants including improved preventative maintenance techniques.
The best way to reduce contaminants from the equipment system is to lessen, or even better, avoid the practices that introduce these contaminants into the system in the first instance.
The processes of cleanliness and cleanliness control may initiate with the OEM referenced cleanliness levels for lubricants to be delivered by the lubricant provider either in bulk or in delivered packaged drum, pail or intermediate bulk containers (IBC).
Even so, there is often one key criterion overlooked when stipulating a desired delivered cleanliness level and that is, the technique for determining the cleanliness code.
Cleanliness tests can be performed using several techniques such as light blockage automatic particle counter (APC), pore blockage technique and cleanliness determination from filter patch tests, each testing method coming with its pros and cons.
Regardless of the testing technique or method utilised, the test results all refer back to the ISO 4406 cleanliness table for cleanliness code determination.
Most oil analysis service providers would “default” to the APC. Unfortunately, this method can have limitations, the main one being that the instrument (generally) cannot determine the type of particle be it water droplets, additives, air or particulates.
This can “falsely inflate” the cleanliness ratings of the tested lubricant especially in the four- and six-micron range, sometimes by as much as five cleanliness code ratings, meaning that often incorrect conclusions are made that the lubricant is “dirty” based on the high ISO cleanliness code determined.
A study by Thomas S. Wanke, Paul W. Michael and Michael A. Mccambridge of the Milwaukee School of Engineering identified factors affecting accuracy pertaining to particle counting and concluded that automatic particle counters produced phantom counts when a polydimethylsiloxane antifoam additive was blended into the base oil.
It is for this reason that many asset and hydrocarbon management professionals may suggest following ISO 4407, that is cleanliness determination by the counting method using an optical microscope.
The assumption that the more one filters the lubricant, the more savings one will achieve can be falsely guided.
High beta ratings at very low absolute micron value levels may have the reverse affect and result in some vital additive(s) being removed from the lubricant, thereby affecting lubricant performance.
The benefits of sound contamination control in lubricants will extend the life of lubricated equipment and reduce maintenance costs through unplanned and premature failures.
Establishing cleanliness targets and measuring performance against these benchmark targets is often a first step and may assist maintenance professionals to quantify potential savings.
However, there needs to be a balance between setting realistic and manageable cleanliness targets that deliver real value to the business as opposed to increased filtration costs for the sole purpose of achieving idealistic and unjustified cleanliness levels with improperly devised value determination.
For more information, please contact your nearest Total Affiliate or visit http://www.miningsolutions.total.com/.
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