Skip to main content
Critical Power Logo


Stationary Engine Catalytic Converters

Diesel Fuel Contamination

Generator Engines may be exercised regularly and operate properly and to specification. However inside the fuel tank, out of sight, free and emulsified water is slowly accumulating from condensation and even fuel deliveries with high water absorption. As the evening temperature falls the water begins to condense out of the fuel and build inside of the tank.

If any water is on the storage tank bottom colonies of filter clogging bacteria and fungus will grow at the fuel/water interface. The by product of these colonies is acidic sludge.

When the fuel/water interface grows high enough to reach the engines fuel supply tube which may be inches above the tank bottom; the filter clogging microbes will be drawn into the fuel system and stop the engine.

99% of all fuel contaminates; including water, are heavier than fuels and will be found on the storage tank bottom.Remove the tank bottom water and the micro-organisms will die.

Therefore it is imperative that the fuel polishing systems intake supply tubes be located on the lowest portion of the storage tank bottom. Failure to do so may result in unexpected engine shutdown.

The fuel polishing system must be independent of the engines fuel supply.

A properly installed Fuel Polishing System will prevent
the emergency generators from becoming the Emergency.

Microbes found in diesel fuel

Virtually all diesel fuel contains some moisture. Additional water accumulates in tanks asatmospheric moisture condenses. Moisture accumulates in diesel tanks as condensatedroplets on exposed tank surfaces, as dissolved water in the fuel and as water bottoms beneath the fuel microbes depend on this water for growth. Additionally, microbes depend on the organic and inorganic molecules indiesel fuel for nutrition. Consequently, some species attack the fuel directly, growing at theexpense of hydrocarbons and non-hydrocarbon fuel components. The biodegradation offuel, in support of microbial growth, is a direct impact of contamination. Color, heat ofcombustion, pour point, cloud point, detergent and anti-corrosive properties change asmicrobes selectively attack fuel components. Sulfur-containing molecules are metabolizedby a series of species, leading ultimately to the production of high concentrations ofhydrogen sulfide. In addition to creating new cells, many microbes produce metaboliteswhich promote further attack. Surfactants facilitate the emulsification of fuel, leading to theformation of a cloudy, invert-emulsion layer above the fuel/water interface.Polysaccharide slimes create microenvironments wherein mixed populations (consortia)of bacteria and fungi carry out biodegradation reactions that would be impossible for a singlespecies outside the microenvironment. The slime also serves as a barrier, protecting themicrobes from preservatives. A variety of organic acids (primarily 2 -4 carbon atoms) are also produced as by-products of bacterial and fungal growth.

Fueltec’s Polishing Systems exceed the engine manufacturers recommended ISO 18/16/13 cleanliness target.

ISO Fuel Requirements

The standard established by ISO (International Organization for Standardization) provides a common measurement system that engine and fuel system manufacturers use to designate acceptable particle levels in the fuel system. Determining fuel cleanliness requirements includes the measurement of both particle size and count. ISO 4406 utilizes a series of three numbers (18/16/13) to identify the particle count per milliliter at 4, 6 and 14 micron sizes. Engine manufacturers recommend ISO 18/16/13 or better as the cleanliness target in fuel tanks.

A micron is a metric measure equal to one millionth of a meter, or 1/25,000th of an inch. The smallest particle visible to the naked eye is 40 microns across. A human hair is 80 microns in diameter, and a single grain of talcum powder is 15 microns.

The Fueltec Primary Filter

Fueltec’s Polishing Systems Primary Filter

  • Removes solid and microbialcontamination to one to five microns
  • Is in place before the systems pumpoffering protection from solidparticulates
  • Housing manufactured from stainlesssteel

The Fueltec Fuel Pump

Draws fluid from the storage tank bottom through the primary filter under a vacuum, under pressure through the water separator, then back to the tank.

Pump housings and gears are made of top quality bronze, shafts are 303 stainless steel. Bearings are made of high performance carbon-graphite material selected for wear resistance and long service life. Gear pumps are positive displacement pumps. Each shaft revolution displaces a definite amount of liquid relatively unaffected by the back pressure in the discharge line. Shaft speed and flow are directly proportional.

Bronze Construction with Stainless Steel Shafts
Positive Spring Loaded Lip Seal made from fluoroelastomer
Available with Motor Adapter and Hardware
Easy Field Assembly to Motors
Self-Lubricating Carbon Bearings
Consult Factory for Special Motors
The pump is driven directly from the electric motor shaft by means of a flexible coupling. An aluminum adapter connects the pump to the motor.

The Fueltec Water Separator


The micro-glass coalescer, originally designed for aircraft jet fuel, is an excellent coalescer for diesel fuels. The cartridge is made up with a pleated cellulose inner filter, polyester glass fibers which remove tiny water droplets from the fuel and cause them to grow in size, and an outer cotton sock which further increases the size of the water droplets.

Stainless Steel/Teflon Water Separator

After passing through the micro-glass coalescer the flows through the hydrophobic water separator cartridge which repels the now enlarged water droplets. The clean dry fuel is returned to the storage tank and the separated water falls to the bottom of the separator housing.

The Fueltec HMI/PLC System Controller

  • A) Programmable: date, time, tank selection, run time
  • B) Compatibility: MODBUS, ETHERNET, GSM/GPRS
  • C) Display:
    • (1) Low water in trap
    • (2) Vacuum at primary filter (filter change instructions)
    • (3) Pressure at final filter (filter change instructions)
    • (4) High water in trap (drain separated water)
    • (5) System on
    • (6) Tank selected for filtration
    • (7) Day selected for filtration
    • (8) Run time selected for filtration
    • (9) Time of day
  • D) Alarms:
    • (1) High water in trap
    • (2) High vacuum (service primary filter)
    • (3) High pressure (service final filters)
    • (4) Fluid in system sump
    • (5) No fluid flow

    1052SS-UL Automated Permanent
    Fuel Polishing System


    1025SS-UL Automated
    Fuel Polishing System


    S2415B-50-UL & S2430B-50-UL Automatic Permanent Fuel Polishing Systems


    CF4 0-PLC Literature 2016


    CF4 0-PLC Specifications 2016

    Close Menu