If you need any convincing that the high-pressure / common-rail (HP/CR) fuel systems used in today’s Tier 4-Final engines are intolerant of even the smallest particulate contamination, take a look at the Donaldson Filtration Solutions’ white paper that summarizes a study at the Southwest Research Institute on “The Effect of Hard Particle Wear on Diesel Injectors.”
The study found that particulates in the range of 2-3 microns produced mechanical damage in an HP/CR system operating at 24,650 psi. (For size perspective, about 50 of those 2-micron particles would fit across the width of a typical grain of table salt.)
These minuscule particles, says the study, “[initially cause] impact wear, or indentation, on the [injector] seal face, and as that damage accumulates, severe erosive wear occurs due to high-pressure leakage…” Some HP/CR systems, of course, operate at pressures well above that of the test system.
The study concludes: “Filter integrity and consistent, high-efficiency performance is essential to protect modern HP/CR injection systems.”
Fortunately, reputable suppliers of on-engine fuel filters have developed the technology that provides the level of fuel cleanliness required by engine/equipment manufacturers to prevent this damage. If you’re not using the specified OEM-branded or OEM-recommended on-engine filter for a particular application, then due diligence is required to evaluate the specifications of the filters you’re buying against the OEM’s specifications.
Experts say that a filter’s Beta Ratio for specific particle sizes and the filter’s efficiency rating, which is based on the Beta Ratio, typically are the most objective measures when comparing filters—more objective than relying on a “nominal” or “absolute” micron rating.
If you need help understanding the Beta Ratio and filter efficiency, pull up the Machinery Lubrication website.
Also, if you’re not familiar with the ISO (International Standards Organization) cleanliness code, ISO-4406, we’ve appended a tutorial. It’s important to be conversant with this standard and its implications to understand much of the industry’s discussion today about filters and fuel cleanliness.
In this regard, the World Wide Fuel Charter (WWFC), an organization formed in 1998 by vehicle and engine manufacturers to elevate fuel quality, recommends that diesel fuel meet an ISO-4406 cleanliness code of 18/16/13 at the dispensing nozzle.
But according to Scott Grossbauer, director for Donaldson’s Clean Solutions Group, no manufacturer of HP/CR fuel systems considers this level of diesel-fuel cleanliness sufficient for today’s machines. Ratings on the order of 12/9/6 are presently being required—which means fuel 64 times cleaner than recommended by the WWFC.
So, again, if you’re not using OEM-branded/recommended filters, ask filter suppliers about Beta Ratios, filter efficiencies, and ISO ratings for their products; reputable suppliers have this information.
Also, you might have to get used to shorter fuel-filter life with Tier 4-Final engines, compared to that of lower-Tier engines. The higher filtration efficiency of today’s filters makes them more sensitive to incoming dirt, and substantially shorter filter life can result.
According to Grossbauer, shorter filter life can be compounded by the presence of organic substances in today’s fuel, which are not dirt, he says, but are related, perhaps, to such sources as glycerin in bio-fuel blends or performance additives that can be picked up by highly efficient filters if the additives are not placed in the fuel under the right conditions and fail to dissolve.
Some machine owners, striving for increased engine protection and possibly extended life from the OEM’s on-engine primary and secondary fuel filters, have added supplemental filtration systems, which are available from a number of reputable suppliers.
The real issue with fuel filtration
On-engine filtration is critically important, but focusing attention on that aspect of fuel cleanliness alone might be to overlook the obvious. According to Howard Chesneau, president of Fuel Quality Services, Inc., fuel cleanliness really begins by “getting control of fuel before it’s pumped into equipment.”
Chesneau asks the obvious question: “Why would you put dirty fuel into your equipment and require your on-board filters to do the heavy lifting?”
So, is most diesel fuel dirty when delivered by a fuel vendor to a fleet owner’s bulk tank or dispensed directly (wet-hosed) into a machine from the vendor’s deliver truck?
Depends who you ask.
People who manufacture HP/CR fuel systems and Tier 4-Final engines say it’s filthy, perhaps arriving at an off-road-fuel-user’s site at an ISO rating of 22/20/17. If the engine manufacturer wants a fuel meeting ISO 12/9/6, then going from a 22 code to a 12 code means reducing the count of particulates 4 microns and larger—in each milliliter of fuel—from an average of 30,000 to just 30.
On the other hand, fuel retailers say that as long as their product meets the American Society for Testing and Materials (ASTM) D975 standard, the official specification for diesel fuel in the United States, then they have fulfilled their obligation to their fuel-using clients. (D975 simply calls for sediment and water to be limited to 500 ppm, a level that falls far short of today’s required cleanliness standards.)
If fuel picks up contaminants after it leaves the refinery—in pipelines, barges, terminal storage tanks, and the like—but still complies to the ASTM specification, say fuel retailers, then how can they be held responsible? If cleaner fuel is required, then ASTM should change the specification.
The counter argument, though, is that D975 is not intended to control fuel cleanliness at the dispensing nozzle, but is intended to ensure that fuel is manufactured with the chemical and physical properties that render it fit-for-use. Diesel fuel, for the most part, is manufactured with a high level of cleanliness; it’s contaminated as it travels through the various means of transport to reach the end user.
Somewhat of a fistfight is developing in the diesel-fuel community about who or what entity is responsible for fuel cleanliness. At present, by default, it has become the machine owner.
Given that reality, machine owners are being advised to radically improve housekeeping practices for the bulk storage of fuel, beginning with tank evaluation and cleaning if required, filtering fuel from the vendor’s tanker into the storage tank, filtering again when dispensed into the machine to catch any debris or chemical issues from the tank, and properly maintaining the tank in between.
That’s a tall order for most machine owners, and a few have begun to ask their fuel vendors to partner in a solution.
Seems to us, though, that all this leaves the potentially troublesome challenge of wet-hosing unaddressed.
From what we’ve heard, the fuel vendor’s wet-hosing delivery truck typically has little or no filtration. So, would fuel suppliers be open to installing the capability required to deliver ISO-4406 12/9/6 fuel, assuming that fuel users would be willing to pay the substantial per-gallon premium that would surely result? And an even more basic question: Are wet-hosing trucks physically able to accommodate such elaborate filtration systems?
If you’re a fuel vendor who has given this some thought, or a machine owner who is talking to your vendor about fuel cleanliness, let us know.