Tier IV emission standards are being heavily pushed in all industries, including on- and off-highway engines. With the regulations taking effect to meet these emission standards, engines have had to add new technologies to manage and reduce these emissions.
By Aaron Keck and Rob Sabo
Today’s government mandated Tier IV requirements have been implemented since 2011 for on-highway vehicles in North America and Europe. In 2018, the government mandated that all diesel engines 175-750 hp need to be Tier IV compliant for off-road engines in the construction, agriculture and power generation industries. With the regulations taking effect to meet these emission standards, engines have had to add new technologies to manage and reduce these emissions to meet the new standards. These new technologies include exhaust after-treatment systems, electronic engine controls and new sensors to only name a few. This has caused an increase in cost, performance and associated expenses to maintain these systems to control emissions effectively. The fuel systems in these new engines are faced with significant design constraints. Three key changes in the industry include: HPCR (High Pressure Common Rail) injection systems, the conversion to ULSD15 (Ultra Low Sulfur Diesel – 15 PPM Sulfur) and the addition of BioDiesel Fuel blends to the stock Diesel Fuel, which varies from state-to-state.
The fuel injection systems of diesel engines have dramatically changed in order to provide a cleaner combustion process to meet the Tier IV emissions requirements. Today, fuel systems can be found with injection rail pressures of up to 43,500 psi and fuel system component tolerances as small as 1 micron (1/40th of what the eye can see). These extreme conditions are in stark contrast to the 1,000 to 3,000 psi systems developed in mechanical fuel injectors from the 1990s. As the technology of the fuel systems has advanced, the need for cleaner fuel has become increasingly apparent. Equipment owners, operators and fleet managers are becoming increasingly aware of the cost of repairs and downtime due to poor fuel quality in today’s Tier IV engines. Many of these types of failures are the result of inadequate fuel filtration leading up to point of injection. Many Tier IV engines require a fuel cleanliness level of 11/8/6 at injection and a level of 15/13/10 in the fuel tank. The Worldwide Fuel Charter standard at storage according to the ISO 4406 Cleanliness Standard is 18/16/13 with no free or emulsified water, dissolved <200 ppm (see Figure 1).
and the addition of Biodiesels blends of B2 to B20 have also added two new challenges to achieving the cleanliness levels needed by today’s new engines and also in fuel storage. With the removal of sulfur in the refining process, some of the natural lubricity compounds are removed and anti-wear additives must now be blended with the fuel to increase lubricity. Typically, ULSD15 is hydrophilic with saturation levels between 25-100 ppm at room temperature. With the addition of biodiesel, these saturation points can rise dramatically—B2 (up to 250ppm), B5 (500ppm) and B20 (1600ppm). What the end-user must understand is that under these circumstances, and as temperatures decrease, there will be more free water found in storage tanks. This then causes more problems at the storage tanks and engines from free and emulsified water, bacterial growth, premature degradation of the fuel systems and the storage mechanisms.
This is where filtration technology has not kept up in the industry, as a whole, to address these problems. Absorption technology can easily be overwhelmed by all the water, thus causing many more element changeouts than in the past. This, in turn, drives up cost, labor to replace elements and, in some cases, lost business to the retail outlets when clogging occurs and customers leave to use another fuel retailer. Coalescing technology for the most part has also not improved, with cellulose medium still being commonly used. Under today’s conditions there are three major problems with this technology. First is the reduction of overall water removal efficiencies as compared to the past. Second is the sheer volume of water that can overwhelm the filters and, if not drained when needed, can saturate the cellulose and destroy the media (think of wet cardboard). The third issue is the formation of ice crystals on the media in low temperatures. This can cause additional cold start issues and can let the water enter into the injector systems. It should also be noted that microbial growth will continue to occur while there is a presence of water in the diesel fuel (see Figure 2). What does this look like in a real world environment?
Today’s “Outdated” Filtration Strategies for Contamination Control
Today and in the past, the key strategies that have been used for contamination control are absorptive filters and coalescing filters applied at the point of dispensing. These are typically spin-on style filters with filtration down to 25 to 30 microns. Other alternatives for dirty or contaminated tanks include tank cleaning, polishing services, kidney loop systems and microbial “spiking” agents to kill the bacteria. These systems can clean and polish the fuel, but many times, does so without actually measuring particle counts, water tests and/or ASTM 975 fuel testing. A visual sample is taken before and after to validate the systems cleanliness. In most cases the benchmark for success was based on how clean the fuel “looks” afterwards.
In our opinion, there are several key problems with these strategies. The first, in most cases, is that one cannot get to the required ISO levels needed in today’s fuel systems through a single-pass particulate and water removal media at the point of dispensing. This is especially true if the bulk fuel is contaminated or dirty. Many times bulk fuel from delivery trucks, trains or barges is between: 25/23/21 to 21/19/17 at best. Since the ISO 4406 scale used to measure particulate levels is logarithmic, each decrease or increase in range is doubled or halved respectively. One pass through a filter will not get the user to where they need to be. Another strategy is to use cleanout services, polishing systems and/or kidney loops to get to the specified levels needed. With permanently installed systems this can work; however, it can become very costly over a short period of time and can also consume large amounts of energy if they have to run continuously. On the other hand, cleaning and polishing services are only good for the fuel in the tank at the time of the service. As soon as this fuel is used and new fuel is delivered into the tank, the user is right back to the delivered fuel quality levels which is usually contaminated with both particulate and water. Also, when using chemicals to treat and kill bacteria in a bulk system, the user is left with the dead organisms and the chemical by-products of the reagents. Both of these can have a detrimental effect on the fuel quality and fuel injection system if allowed to get into the combustion chamber of the engine. The residual effects have been hypothesized to create varnishes that can cause injectors to function erratically when subjected to the extreme high pressures and temperatures in modern HPCR systems; however, it should be noted that this is still a matter of debate.
When HPCR pumps and injectors do fail, the majority of these failures are directly attributed to solid particulate failures and water ingression. Figure 3, page 42, is an example of an HPCR system components that failed. One can see on the injector poppet that pitting that has occurred from water. The injector seat is scored from ingressed particulate and the upstream pump failure.
*It should be noted that one catastrophic failure from a HPCR system can cost upwards of $5000.00+ for a 4-6L system. This does not include the downtime costs and/or the inconvenience of the loss of equipment. Many times a failure can have a negative impact on construction schedules, loss of backup power generation, agricultural, municipalities, mines and/or personal loss of one’s vehicle. These examples can be given wherever diesel engines have failed. When this does happen, it usually never occurs as a planned event.
Another consideration in cost control is an effective overall comprehensive filtration strategy. All of the above solutions do have their own place and can be effective if used in conjunction with a good proactive maintenance plan. If the water can be eliminated before it enters into the system and kept out effectively, most of the other problems can be mitigated with little effort. This does however, demand a true investment into the infrastructure that is not currently instituted today as a whole throughout the industries effected by the implementation of the Tier IV requirements. It should also be noted that a small capital upfront investment can be cost justified by the prevention of just 1-2 HPCR failures in equipment. The ROI (Return-On-Investment) is justified and the payback is obtained by just one or two failures, if implemented properly.
Fuel Filtration Center of Excellence Based Solutions and the Impacts on Modern Systems
In order to create a system that will provide the lowest cost of ownership and meet the requirements of today’s fuels systems, it is imperative to protect a system at every point of transfer. With this being said, one must start with a clean tank, free of water and other contaminates. Once this is accomplished, highly efficient single-pass filtration can be used at the points of transfer to protect the systems from both water and solids. This will also allow the complete delivery system to meet the mandated specifications at all points throughout the system. When accomplished properly, this will provide the least expensive overall cost of ownership and prevent costly catastrophic fuel systems failures.
The required fuel single-pass filtration technology does exist, and the movement towards a better level of filtration is still a learning process for most end-users today. As the new Tier IV engines infiltrate the market, the need for better filtration is becoming more apparent as fuel filtration is addressed from the point of fuel production to the fuel injector.
From the time diesel fuel is produced, particulate filtration and water removal technologies are needed to provide conditioned fuel to the many levels of distribution. High flow filter vessels are examples of high performance, fully synthetic particulate and coalescing filtration. These are capable of particulate filtration down to 3 microns with individual vessel flow rates of up to 951 gpm. It provides the first level of needed filtration, but the need does not stop at this point.
At the point of bulk fuel delivery, the downstream fuel in storage should be held to an ISO cleanliness code of 18/16/13 and a water content of under 200 ppm according to the Worldwide Fuel Charter. In order to achieve this, one of several solutions needs to be applied. A Bulk Diesel Skid or BDS is an example of a range of bulk diesel filtration products capable of flow rates ranging from 70 gpm up to 280 gpm using fully synthetic particulate filtration and a water removal efficiency of greater than 99.5 percent in a single pass. A filter skid can be applied as fuel delivery filter or used as part of a high flow filtration system, ensuring the bulk fuel is held to cleaner standards. A Bulk Diesel Fuel Filtration Cart, BDFC, at 14 GPM or a Bulk Diesel Cart, BDC, at 25 and 70 GPM can also be used to clean contaminated fuel tanks in order to meet bulk fuel cleanliness recommendations.
Even with the levels of filtration previously mentioned, the fuel in bulk tanks requires additional filtration in order to meet the level of cleanliness required by most equipment OEMs and injection system manufacturers. For dispensing applications, a fine filtration solution will ensure that clean fuel is being dispensed into the equipment. The Bulk Diesel Fuel Filter, or BDF, at 16 or 32 GPM provides particulate filtration down to 1 micron and water removal efficiencies of greater than 99.5 percent single pass efficiency.
In order to keep out new ingression of both water and solids as a tank exchanges air during the filling and dispensing process, it is critical to protect the ingression of air into a bulk tank system. Desiccant air breathers can be used to achieve this. In addition to dispensing filtration, each piece of Tier IV equipment requires adequate pre-filtration to prevent fuel quality related failures and/or premature engine filter replacements. A Heavy Duty Pre-Filter uses fully synthetic media for high particulate capacity and high efficiency water removal in both automatic and manual water drain options.
Conclusion
In short, Tier IV emission standards are being heavily pushed in all industries, including on- and off-highway engines. With the regulations taking effect to meet these emission standards, engines have had to add new technologies to manage and reduce these emissions. Equipment owners, operators and fleet managers are becoming increasingly aware of the cost of repairs and downtime due to poor fuel quality in these new Tier IV engines. From the time diesel fuel is produced, particulate filtration and water removal technologies are needed to provide conditioned fuel to the many levels of distribution. These products provide the first level of needed filtration, but the need does not stop at this point.
Aaron Keck is Product Manager – Fuel Products and Systems, for Schroeder Industries (Leetsdale, PA). He can be reached at [email protected].
Rob Sabo is Group Product Manager – Fuel Products and Systems, for Schroeder Industries. He can be reached at [email protected].
For more information on Schroeder Industries or an in-depth evaluation of your systems, call (724) 318-1100 or visit www.schroederindustries.com.
References
• Standard Specification for Diesel Fuel Oils, ASTM D 975-09b
• Diesel Fuel Technical Review, Chevron, 2007
• Emission Regulation for Non road Engines, EPA document EPA-420-F-12-054, August 2012
• World Wide Fuel Charter, 5th Addition, September 2013
• Caterpillar, Specification: SEBU 6251-13
• Cummins, Specification: Bulletin LT 36163
• Google, World Wide Web, Image Gallery
*These examples are based on the authors own personal experiences and feedback from customers and clients over the years.