Fuel Filtration for Modern Diesel Fuels

National Biodiesel Board Technician Outreach Program

Today’s Topics

Changes in modern diesel fuel Basics of diesel engine fuel filtration Fuel Filter design Fuel Filter media Fuel quality Filter efficiency Resources

Changes in modern diesel fuel Emissions & air quality driven Ultra Low sulfur Diesel Low Sulfur Diesel fuel, Off-road Biodiesel & Biodiesel Blends Non- Biodiesel fuels

Coal Slurries Raw Vegetable Oils and Fats Non-Esterified Oils Partially Esterified Oils Blends With Diesel Non Ester Renewable Diesel

Diesel fuel and its injection

Common Rail Diesel and Unit injection fuel injectors operate at high pressures

They are electronically controlled for optimum fuel metering and complete combustion

End goal is cleaner diesel emissions

Fuel Filter Variation Capacity is the measurement (in grams) of

the total amount of containment a filter can retain at a rated flow and given end-point (restriction).

Restriction is the pressure drop across the element at a given flow, temperature, and fluid viscosity.

The type of media and general filter construction defines restriction.

Fuel Filter Efficiency Efficiency is the ability of the filter to

remove particulate (% efficient) at a given micron (size)

The type of media being used ultimately defines the filter's efficiency.

Filter Micron Rating What is a micron? The common unit of measurement in the

filtration industry is the micron or micrometer.

One micron equals forty millionths of an inch (.00004).

A single human hair is approximately 70 micrometers.

Fuel Filter Media Silicone Treated

Cellulose Glass and Cellulose

Co-Pleated Cellulose and

Meltblown Combination

The type of media and the amount (square inches) of media defines capacity.

Primary Fuel Filter

Provides low restriction because it is mounted on the suction side of the fuel pump where normally a suction pressure of only 5-6 pounds per square inch is available.

The primary filter protecting the transfer pump and lightening the load of the secondary fuel filter (if installed).

Primary fuel filters typically have a nominal rating of 10 - 30 microns.

Not all vehicles have a primary filter

Secondary Fuel Filter The secondary fuel filter is

designed to offer full protection to the fuel injectors.

It is mounted between the transfer pump and the injectors.

Secondary filters tend to see much higher pressures than primary filters.

Secondary fuel filters typically have a nominal rating of 2 - 10 microns.

Water Separators Water flowing at high velocity between highly

polished valve seats and through fine nozzle orifices causes a wearing action that approaches that of abrasion.

The presence of water, especially with entrained air and various fuel components, causes rust and other chemical corrosion that eats away at the finely mated surfaces.

Use chemically treated paper to repel water which then settles by gravity to the bottom of the filter.

Accumulated water can be drained from the filter if equipped with a drain valve or plug.

Water Separators

Emulsified water is a problem for both ULSD and biodiesel

Traditional media is challenged by both fuels

Interfacial Tension Fuel Surfactancy Fuel/Water emulsion stability

Fuel Quality concerns Out of specification

fuel of any kind can clog filters and damage internal components

Purchase fuel that has been properly filtered to meet your vehicle’s needs

Asphaltenes Asphaltene is a by-product of fuel as it oxidizes. These particles are generally thought to be in

the half micron - 2-micron range Thought to be harmless to the injection system,

as they are soft and deformable. As these tiny particles pass through the filter

media they tend to stick to the individual fibers.

Aphaltenes can be observed in normal fuel filters as a black, tarry substance on the dirty side of the element

Fuel Filter Maintenance

Adhere to manufacturers recommended maintenance

Examine internal filter media

How full is the filter?

Exposure to AirExposure to Air• Enters through vent pipes and

contains large amounts of moisture.

• Generally displaces the fuel as tank is emptied.

• It is not practical to keep air from entering the tank.

• Will increase the oxidation of fuel.

• Do not store fuels for long periods of time in partially empty tanks without stabilizers.

• Consider desiccant dryers.

Microbial Growth• Microbes are bacteria or fungus that live and

propagate in fuel at the fuel/water interface.• Water needed to live—no water, no bugs.• Hydrocarbons in petrodiesel or biodiesel provide

the food and the water provides the oxygen.• This environment is needed for living, growth,

and reproduction.• The filters with microbial contamination often

had an odor different from the normal fuel smell.

Water Contamination• ULSD reaches water saturation at approximately

200-300 ppm. More settles to the bottom.

• NREL B20 survey data: same water saturation level as petrodiesel. More settle to the bottom

• B100 can hold more water, up to 1200 ppm

• Still very small—0.12%, on the same order as gasoline can hold water. Un-dissolved water settles to the bottom like it does in petrodiesel tanks.

• While higher than petrodiesel, biodiesel is not water loving (i.e. hygroscopic) like ethanol is. Most people do not understand this fact.

What could I see in a Diesel Fuel Filter?

Severe water saturation

High Water Concentration

Icing of the filter • When there is excess free water in fuel, it can

form ice on the filter and cause filter plugging in cold temps. A filter which has been plugged but is clean and new at room temperature indicates that icing is the likely cause.

• Since the temperatures of engines are warm, any moisture picked up within the engine can be brought back to the fuel lines. This moisture can freeze overnight in low ambient temperatures.

Free water

What could I see in a Diesel Fuel Filter?

• Some of the filters had solid sediment within the folds and solid particles in the filter casing.

• Sediment present in the fuel or rust particles from within the engine can collect over time and plug the filter even when there are not necessarily problems with the fuel.

• Not always related to biodiesel use

This filter had a rust sediment plugging issue, this substance came back at 99.5% iron

• High level of paraffin material could be from the way ULSD is processed.

• When the temperature of the fuel is at or below its cloud point, paraffin material will precipitate out and collect on the bottom of the tank.

• When warmed to room temperature the paraffin wax will turn back into liquid.

• Paraffin build-up does not come from biodiesel fuel.

What else could I see in a Diesel Fuel Filter?

What could I see in a Diesel Fuel Filter?

Glycerin from off specification biodiesel Other contaminants like

water and sediment

Oxidation • Filters with a black and shiny

surface but no microbial growth odor or gel or sediment indicate they may be plugged by oxidation build-up.

• Because many newer engines run at higher temperatures, there may be a black “asphaltene” petrodiesel type material collecting on the filter.

• This phenomenon has been seen all around the country, often in newer engines.

Oxidation

• Petrodiesel does not have an oxidation specification, while B100 and B6 to B20 specs already do.

• Biodiesel can also oxidize, but oxidized biodiesel manifests itself in acid numbers which are out of spec

• The acid number for biodiesel will go out of spec before filter clogging occurs

Troubleshooting Checklist• Fuel Storage Tank Maintenance – Reduce

exposure to air, water, and microbial growth

• Fuel/Water Separators – Excess water in tank can cause icing in filters

• Oxidation – Hot fuel return to fuel tank, aged diesel fuel

• Paraffin Wax – Temperature at or below cloud point

• Recommend regular fuel filter maintenance

Filtration Resources•www.biodiesel.org

• Technical Library

• Biodiesel Bulletin

• Educational Videos Available

• Informational Resources

• Technical Resources

• On-line Database & Spec Sheets

•Southwest Research International Filtration Conference

•Filter Manufacturers Council http://www.filtercouncil.org/

•Donaldson Filtration

•Society for Automotive Engineers