Combating Dirty Fuel

Debasish Mukherjee

Combating Dirty Fuel



The fuel system is one of the most crucial and expensive systems in mobile equipment. Essentially, it is the lifeblood of all construction and mining machines. Fuel costs today are about 80% of operating costs, as against 35% in the 1970s. This cost is the largest expense over the life cycle of any engine.


Fuel injection system pressure in the 1970s and 1980s was 8700 psi. Today, fuel systems operate at 29000 psi. Even a single foreign particle inside such a high-pressure system can have a devastating effect on various parts and components. That's precisely why present fuel systems demand consistently clean, dry fuel.


The performance and durability of an engine are highly dependent on the fuel's cleanliness. In this article, I highlight a few salient points on how to consistently provide clean and dry fuel.


Clean, Dry Fuel

There are multiple potential sources of contaminants in any fuel system. Following is the extensive list:

  • Supply
  • Storage
  • Handling
  • Transfer or dispensing
  • Service
  • Operation
  • Maintenance

Now, it's relatively easy to understand the necessity of providing clean, dry fuel.


Before proceeding further, let's clearly define what it means. The fuel that complies with particle & size distribution according to ISO 4406 is ISO 18/16/13 or less at storage and is considered clean & dry. The cleanliness level is more stringent at the high-pressure pump inlet, ISO15/13/10. This also includes water contamination because water is detected as a contaminant by a particle counter. However, the Karl-Fischer method may be used separately to quantify water content in fuel. The maximum water content recommended is 500 ppm.


Unfortunately, every facility in India cannot afford to procure such expensive instruments. Moreover, skilled technical personnel are required to operate, maintain and upkeep these assets. Here, we will discuss a cheaper and easier process for regularly monitoring fuel cleanliness.


Study and Observations


Two types of processes of fuel storage, handling and dispensing are usually followed in India:

  • The fuel-filled bowser (tanker) reaches the sites and fills the vehicles' tanks.
  • The bowser from the nearby fuel station fills its tank and dispenses the fuel to the tank in the workshop adjacent to the site. The vehicles are refueled from this storage tank. This process is also followed in component repair shops.

The most common fuel contaminants experts have noticed over the years are:

  • Water
  • Fine abrasives
  • Sediments
  • Fibres & sludge
  • Microorganisms

The genesis of all these contaminants is ignorance, poor work practices, or both. The entire chain of activities is performed in an open atmosphere, allowing free access to contaminants. We had been to a few of these mine operators' sites to check some random fuel samples. Another portion of the same samples was collected to do the particle count test. At the site, we were dependent solely on the patch test in the absence of any particle counter.


Patches were studied using a 50X manual microscope. Photographs were taken with a simple digital camera using the optical zoom. Pictures of the patches are shown in Fig 1 A, B, C, D & E. Expensive microscopes are not required for this purpose. These fuel samples were pulled from the final filter before proceeding for combustion.





Figure 1A








Figure 1B - Dirty fuel patch








Figure 1C - Clean fuel patch with few particles








Figure 1D - Dirty fuel patch








Figure 1E - Dirty fuel patch





The lighter the patch, the cleaner the fuel and the darker the patch, the dirtier the fuel. This is the thumb rule, with no exception. Contaminant particles in the patches are predominantly road dust. Please note that particles with red color in the patches may be noticed. The soil in this region is red with abundant laterite deposits where red iron oxide is dominant. Occasionally, a few white particles are also observed in these patches. These are aluminum oxide from the soil. Laterite deposit contains both aluminum and iron oxide. These contaminants are abrasive. They are also ranked higher in the "mho" hardness scale. A long fiber-like particle is also present in Fig 1B. These are cloth fibers probably originating from repair activities. Instead of lint-free cloth, these facilities use torn clothes, which are cheap and widely available in local markets.


The particle count data of all these fuel samples were found to be ISO 23/22/20, compared to the recommended cleanliness level of ISO 18/16/13 or less. The particle counter was thoroughly flushed with clean solvent before each measurement until ISO 11/9/7 was achieved.


So, essentially, it boils down to the fact that these hard, finely abrasive particles act like sandpaper and freely invade sophisticated, crucial fuel injection components at such high pressure. Frequent two-body and three-body abrasions quickly damage the components. The reliability of the fuel system will be drastically reduced, and even mid-injector life would be impossible to achieve.


Deep Dive and Delve


Every step in the entire operation chain during storage, handling and dispensing of fuel must be conducted in a closed system.





Figure 2A – Consistent supply of clean dry fuel





It's an overhead storage tank. All the best practices are incorporated – sampling points at various locations, drain valve at the tank's lowest point, proper size and type of breathers, filters and water separators. The last two items are installed both at the incoming and outgoing fuel. A pump must be used to fill the storage tank. Filter clogging indicators are not shown in Fig 2A. Also, sampling from any storage tank zone (particularly the bottom & middle region) may be pulled, as shown in Fig 2B. This applies to mobile bowser systems also.





Figure 2B – Fuel sampling from a storage tank





Initially, three NOS fuel filters may be used if the fuel is too dirty. One no filter may be removed later when the particle count data consistently reads ISO 18/16/13 or less or the patch shows fewer particles when compared with the control patch. Next comes maintenance activities, which appear more challenging. The following actions are strongly recommended. These are repeatedly tested and established in one of our facilities:

  1. All lines are closed using the proper size of caps & plugs when not in use.
  2. Water draining from fuel storage tank - frequency daily
  3. Checking of breathers, filters & water separators for proper functioning & replacement
  4. Oil sampling from all locations initially thrice a week
  5. Oil sampling from final delivery once a week when the process is standardized
  6. Fuel storage tank cleaning – frequency once a year.
  7. Fuel sampling from the fuel tank is shown in the picture below (Fig 2B)
  8. Quarterly frequency
  9. All consumable items must be in stock.
  10. All maintenance records, documents, and data must be kept neatly in separate files. We must remember talking without data is meaningless.

Figs. 3A and 3 B show a water separator, followed by a series of water separators, high-efficiency fuel filters and the overhead fuel storage tank.





Figure 3A








Figure 3B





The author did not get any scope to implement the same system in fuel bowsers primarily because the clients showed no interest.


The processes and procedures described above are quite simple and commercially cheap. Many are consumables, and CAPEX components are low-value items. Maintenance activities, too, are relatively simple.


Lately, OEMs have developed their own fuel filtration systems that can handle high-volume flows — 50 gpm to 200 gpm. However, these units are quite expensive and a dedicated maintenance team is required to operate and maintain them. That's not a hopeful picture in a country like India.


Eliminate Innocence and Elevate Excellence


From the above discussion, we have primarily emphasized two basic work practices.


Patch test – its importance, technique and correct interpretation. It is qualitative yet cheap, and no formal, extensive training is required. Moreover, the process is beneficial when regularly, properly implemented and compared with a control sample. Patch test is applicable for all fluids involved in the activity.


Another one is the change in work practice. Any fluid under use must be handled in a closed system. This will prevent contaminants from invading the critical components. That's a revelation.


Here in India, the road to excellence is rocky and slippery. That's implacable, brutal ground reality. We are still not aware of the consequences of dirty fuel. A high concentration of hard, abrasive solid contaminant particles at such high pressure has a terrific destructive effect. Not only is the fuel system seriously damaged, but engine components like piston, ring, and liner are also likely to be adversely affected in case of profuse fuel dilution.


When this happens, the end-user typically blames the OEMs, trying to justify the failures as manufacturing defects and claims warranty replacement. OEMs, too, are becoming cleverer with experience. They ask for data, evidence etc. This on-going struggle, more popularly known as the arms race, persists today. However, this terrible, nasty war between the end-user and the OEM should not be confused with an elegant evolutionary arms race between cheetah and antelope (say).


In most cases, machines do not fail independently; they fail due to human error. That's precisely why some eminent personality has made the sensational statement, "Machines Don't Just Die . . . They're Murdered."




Caterpillar Inc & Gainwell Commosales India Pvt Ltd are wonderfully supportive of collecting data and evidence for this subject.



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