Differences between primary and secondary filters vary from system to system, but in general, primary filters are used to separate water and larger particles (7-25 μm efficiency). Secondary filters are for final filtration (3-5 μm efficiency). Primary filters usually will have treated media to provide water separation performance. This can be either cellulose or a multi-layered synthetic media called meltblown coupled with cellulose like Donaldson’s SynteqTM media. Secondary filters have untreated, multi-layered cellulose or purely synthetic media. These differences mainly have to do with the water separation requirements placed on primary fuel filters.

Q2: Have micron (μm) ratings become smaller and smaller as injection technology has advanced? When replacing filters, how do you make sure you have the micron rating that’s appropriate for your generation of engine and its injection system?

As injection technology has advanced and injection system pressures have increased the filtration requirements have become more demanding. These systems have required filtration technology to be more and more efficient. When replacing your filters be sure you use an OEM approved replacement or a direct cross from a reputable filter manufacture to ensure you are using a filter that is appropriate for your engine.

Q3: Some truckers used to use a fine primary filter to avoid changing the secondary, while the original equipment concept was to use a coarse primary (on the suction side) and a fine secondary (on the pressure side). This took extra changes, but they liked the idea of avoiding changing the secondary. Is doing this impractical on modern engines?

Primary and secondary filters are usually balanced to provide the required engine protection and the optimum filter life. Placing a fine filter in a primary (suction) filter location is impractical because they can not tolerate as much pressure drop and will need to be changed very often. Generally, fine filters do not contain the require water separation in a primary filter.

Q4: How have new engine designs affected fuel filtration?

In the past, diesel engines had either mechanical fuel injectors or unit injectors. The drive to develop engine that meet emissions regulations has led to the application of common rail fuel injection systems. The higher pressures of common rail systems enables more precise control of fuel delivery and control of the combustion process. The goal of the new technology is to reduce the particulate matter and NOx coming out of an engine system, thereby reducing the burden on after treatment systems. The very high pressures in the common rail systems require tighter tolerances, elevating the requirements for cleanliness and efficiency on new and future fuel systems. This has created the need for increasingly better fuel filtration technology. Donaldson offers a range of products for those demanding conditions and is developing solutions for tomorrow’s requirements.

Q5: Will common rail systems bring any changes in terms of fuel filter requirements? If so, can you say what will they be?

Most fuel injection systems today are already common rail or close derivatives. The technology itself does not drive specific changes, the injection pressures and desired filter service intervals are more influential.

Q6: How important is filtering fuel stored in bulk tanks?

It’s becoming very important and can reduce future vehicle maintenance downtime. If you’re using a bulk fuel tank, filtering the fuel BEFORE putting in your vehicle is another great practice that can reduce contaminant and water from the fuel before refilling your vehicle tank. Over times, tanks can corrode, water condensation can build up, contaminant could enter the tank opening during fills.

Cellulose (traditional media)

Engine fuel filter media is most commonly a pleated cellulose base material. This fuel filter media is tested for compatibility with a variety of diesel fuels, including biodiesels. Larger particulate are trapped on the outer layer of the media, while finer particles are held deeper in the media.

Treated Cellulose (Fuel Filter Water Separator Media)

This fuel filter water separator media is a cellulose base material. Treating a cellulose media with a silicon based treatment allows for effective water separation. Typically, this media is used on the suction side of the fuel system to remove harmful water and coarse particulate contaminant. Water coalesces on media and drains to bottom of can/bowl. Particulate is trapped and held in media.

Synteq™ Fuel Filter Water Separator media (meltblown & cellulose)

Donaldson’s third generation of Synteq fuel filter water separator media uses both cellulose and meltblown synthetic layers to achieve the highest levels of fuel filtration performance. This double-layered media increases particulate holding capacity and is a high performance water separator. It has the ability for high efficiency emulsified water separation and can be used in both suction and pressure sides of fuel systems.

• Drain water from your primary filter daily when refuelling.
• Carry a spare set of fuel filters in case you receive a bad load of fuel.
• Never switch to more open filters to get longer filter life – this will reduce fuel pump and injector life.
• If using biodiesel, make certain your fuel supplier meets current fuel standards.
• Ensure that your engine is compatible with the concentration (or percent) biodiesel you wish to use.
• When using your own fuel tank, remember that removing contaminants before they reach the vehicle is the best. Therefore, it is best to use some type of bulk filtration.

Filter Storage & Handling Tips

• Never store a filter on a shelf without it being in a box or totally sealed from outside contaminant.
• When you see an open box of filters on the shelf close it (you can also seal it with tape) unless the filters inside the box are individually sealed.
• Handle filters with care to prevent filter damage for example, don’t throw filters into the back of a van and/or allow them to roll around.
• Metal storage shelves may cause condensation to form on filters if sitting directly on metal. Over time the filter may get rusty. This is another good reason to store filters in boxes.
• If a product has layers of contaminant, take care that the contaminant doesn’t get on the new filter as you remove it from the box.
• Practise “first in, first out” with your inventory. When possible, always use the oldest products first.
• Make sure any labels with product information and manufacturing dates are visible to personnel pulling from the shelves.

Filter fatigue results from pressure pulses within the system. Pressure is regulated by a pressure regulating valve. This valve is spring operated and intermittently opens and closes to regulate pressure. Once pressure exceeds the setting of the spring in the regulating valve, the valve will open and relief the pressure until the spring can expand and close the valve. This function is continued continuously during operation of the system, creating a pulsing effect. Filter canisters are subjected to the same pulsation. However, unlike the spring in the pressure regulating valve, canister material is susceptible to failure after such fatigue.

Filters are designed with a low carbon steel to resist fatigue and are formed so the stress created by the pulses in the system are equalised over the surface area of the canister. A dent provides an area of stress concentration where pressure pulses can greatly shorten the fatigue life of the canister.

Remember, filters should never be fitted to an engine or hydraulic system if they are dented or damaged in any way.

Fuel is transported from the refinery to bulk storage tanks by truck/train. From there it is loaded into another truck and delivered to your site. Once in storage at your site it can either be transferred to smaller tanks or dispensed directly into equipment, each time the fluids are transferred more contamination can be introduced.

You can protect your fluids by installing a quality Donaldson TRAP breather on the storage tank and remove airbourne contaminants and ambient humidity. You can also polish fluids on the outlet of your tank before dispensing into equipment with Donaldson filtration units. Donaldson filter manifolds are available for the inlet and outlet to allow easy fitting of the filter heads and bowls. Manifolds are available that take 4, 8 and 10 filter units.

Sterling Filtration can offer the entire range of Donaldson bulk fuel storage filtration systems whatever your application. Give us a call on 01902 491118 and we’ll make sure we service your filtration needs.

Sterling Filtration can offer a wide range of filter elements to service your compressor machine needs. We have a wide range of parts available through our extensive supply chain to service machines including, but not limited to, Ingersoll Rand, Zander, Bauer, Hydrovane, Kaeser, Husky and Compair compressors.

We supply 1, 0.1 and 0.01 micron filter elements for inline compressed air use as well as being able to offer the complete assemblies too. We also stock air, oil and fuel filters for large compressor engines as well as air/oil separators for many applications.

Remember it is cost effective to regularly service your filter elements than not service your equipment and have to completely buy new equipment.

The panel filters reduce impressively the amount of maintenance down time, keeping the inside of the train carriage much cleaner reducing scheduled cleaning times.

If you have any rail filter requirements please give us a call on 01902 491118 today.

So from everyone at Sterling Filtration Ltd, “Merry Christmas and a Happy New Year to all of our customers and suppliers.”

Let’s make 2012 a good year.

A full range of Donaldson Top-Spin pre-cleaners are available from Sterling Filtration Ltd.