Aviation Fuel Cleanliness

Roger Simonson, CTO – Black Powder Solutions – May 2021

All fuels employed in the Aviation industry require the highest possible cleanliness value that allows the cleanest burn resulting in the least amount of solids emissions possible. Clean fuel also reduces premature wear of fuel system components.

Types of contamination:

(1) Black Powder Contamination (2) Free water and dissolved water (3) Microbial growth

Black Powder: consists of iron compounds from corrosion and erosion of metal storage tanks and pipelines and non-ferrous particulate such as silica.
The main source of Black Powder contamination are delivery vehicles: pipelines being the most prolific source and then rail and transport tankers. Other sources are storage tanks, air breathers, hose connections, pump wear, etc. To date the standard method of removing Black Powder solids contamination is with traditional filtration media.

To understand Black Powder contamination a solids analysis is necessary. Typical volumes of Black Powder in refined hydrocarbon liquid pipelines under 4 microns and down to and below 1 micron in size range from 10% to 40% of the Black Powder solids contamination.

Most traditional filters employed on aviation fuel are of high quality and highly efficient in cleaning Black Powder solids from the fuel before entering the plane fuel system and combustion. In most cases these filters will meet ISO standards of 18-16-13 and or NAS 6. Unfortunately, these industry standards are outdated as they focus on contamination particle sizes from 4 microns and higher and do not providing a cleanliness value present day emissions regulation require.

Traditional fuel filters
Black Powder contamination collected on magnetic elements

Another issue with traditional fuel filters is metal contamination provides the opportunity for cutting holes in the filter media referred to as worm holing and channeling allowing the fuel to follow the path of least resistance reducing the efficiency of the filter media. Stainless cloth media filters eliminate this issue. Magnetic separator elements also eliminate this issue.

The next step is understanding why traditional filtration technologies are not efficient in cleaning the Black Powder under 4 microns in particle size. One solution is employing traditional filters with lower micron capability but results in short operating cycles, bypassing and more frequent filter element change outs. Frequent change outs increase the opportunity of injury for travel to and from and contact with the filter system. One time use filter elements create a costly environmental and safety issue. Black Powder contamination under 1 micron flows through traditional filters.

0.8 micron Millipore Patch Test Results from fuel samples taken upstream and downstream of Magnetic Separator.

It is important to ensure your filter supplier identifies the particle size efficiency rating for the element and to clarify the distinction between 1 pass or multi pass rating. The contamination loading rating is also important. Typical loading capability is 4 to 5 ounces of solids contamination per linear ft of a 5” diameter traditional filter element saturates the element causing the bypass to be activated.

To achieve a high cleanliness value the fuel should be filtered at every transfer event. Before entering the plane fuel system, a particle analysis should be conducted to identify the solids contamination in the fuel starting at 0.05 microns, 1 micron, 4-micron, 6 micron, 14 microns and higher and the volume of each size. This will provide the evidence for industry to understand the need for separation/filtration technologies to clean the fuel to a higher standard starting at 0.05 micron particles. A simple Millipore patch test will provide the evidence of contamination values.

As non-bypass traditional filter media become saturated the pressure differential increases and may cause the filter element to disassemble and contaminate the fuel system.

Black Powder Contamination removed from the Magnetic Separator elements after cleaning cycle.

Water & Microbial Growth

Dissolved and free water create corrosion issues for aviation fuel. The suspended water particles volume varies with the temperature of the fuel and the atmosphere. Therefore, temperature and moisture changes result in a continuous accumulation of water. Iron is a main food source for micro-organisms and when the PPM of iron is reduced the bacteria should also be reduced. Iron-oxidizing bacteria are chemotrophic harvesting the energy they need to live and multiply by oxidizing dissolved ferrous iron.

Magnetic Separation an Alternative Solution

The solution is to employ magnetic separation technology that is capable of cleaning the fuel with high efficiency down to and below 1-micron particles sizes. The magnetic element also acts as a predictive sensor tool as it offers a solids sample that can be analyzed providing a clear picture of the contamination type, size, and percentage. A sample of the fuel before and after the magnetic separator will quickly identify contamination values before and after and the efficiency of the magnetic separator technology.

Cleaning the aviation fuel of Black Powder contamination (ferrous and non-ferrous wear contamination) down to and below 1 micron in particle size will:
(1) Protect the integrity of the whole fuel system from premature wear.
(2) Reduce food for microbial growth.
(3) Reduce emissions by a cleaner burn.
(4) Reduce buildup of under 1 micron contamination particles in the plane fuel tank.
(5) Reduce consumption of traditional media filters and desiccant filters.
(6) Reduce ESG Risk and OPEX.

Magnetic Separator Technology Capabilities:

(1) Capable of cleaning ferrous and non-ferrous wear contamination from below 1 micron particle sizes to 500+ micron particles sizes with a 95+% efficiency.
(2) Contamination holding capacity of 12-14 pounds per linear foot.
(3) Cleaning cycles range from 3 to 6 to 12 months depending on the application.
(4) Operational life of 18+ years.
(5) Manual cleaning, semi-auto and fully auto cleaning systems available.
(6) Minimal consumables and minimal services required to operate.
(7) Cleaning System operates by electrical, pneumatic, and or hydraulic power.
(8) Designed and manufactured to all ASME standards as required.

Water Remediation Management:

(1) Recommend employing quality desiccant breathers.
(2) Employ 24/7 vacuum dehydrator kidney loops on main reservoirs
(3) Employ polymer water absorbers in a duplex design on a kidney loop for main reservoirs.
(4) For inline fuel dispensing employ a polymer water absorber in a duplex design for continuous flow. Please note: BPS polymer water absorbent technology is being developed and will be available soon.