Diesel fuel supply systems must ensure continuous and clean supply of fuel to the engine’s…
Fuel Tank Design Considerations
Fuel Tank Sizing
The fuel tank is typically one of the least expensive items in an installation, and it is wise to provide too much, rather than too little, storage capacity.
However, while the minimum required capacities of fuel tanks can be estimated, as outlined in the previous discussion of fuel tanks, some applications may need to meet the requirements of outside organizations, such as the U.S. National Electrical Code (NEC) or National Fire Protection Association (NFPA).
Fuel Tank Material
Fuel tanks made from low carbon rolled steel are best.
CAUTION: Zinc, either in the form of plating or as a major alloying component, should not be used with
diesel fuels. Zinc is unstable in the presence of sulfur, particularly if moisture is present in the fuel. The sludge formed by chemical action is extremely harmful to the engine’s internal components.
Fuel Tank Installation
Large capacity storage tanks allow bulk purchases and minimize dirt contamination. Maintaining full tanks reduces condensation, particularly if fuel is seldom used.
Tanks may be above or below ground level, but high fuel level generally should not exceed the engine injector’s height. This prevents possible fuel leakage into cylinders.
Above ground tanks provide accessibility, allowing for easy draining of impurities and reducing the danger of ground water contamination.
Underground tanks allow the earth to work as an insulator, limiting radical temperature changes which can cause flow restrictions, condensation, and possible power loss. Seasonal settlings are also avoided when burying the tank below frost line. In underground tanks, the water must be removed by pumping through a tube placed down the fill pipe.
Regulations governing the installation and maintenance of both above and below ground fuel tanks may apply.
Locate storage tank fill tubes for convenience and safety of filling operations. Vents are necessary to relieve air pressure created by filling and prevent vacuum as fuel is consumed.
Fuel Tank Drains
All fuel tanks should have easily accessible drain connections. Water and sediment that collects in the bottom of the tank must be eliminated regularly. Provide clean out openings for periodical removal of sediment and trash that settles out of fuel tanks.
Well-designed tanks have large enough clean-out openings so the lowest part of the fuel tank can be accessed with cleaning equipment.
Fuel Tank Grounding
Fuel tanks, both bulk and auxiliary, need to be grounded. This is to improve personal safety and reduce the fire hazard of sparks discharged from static electricity build-up during refueling operations.
If the auxiliary tank is mounted to the base of the engine, it will be grounded at the same time as the engine. If the fuel tank is placed away from the engine, the tank must be grounded separately.
Fuel Tank Maintenance
Fuel has a storage life of approximately one year. This period may vary widely depending upon initial fuel quality, contaminant levels and storage conditions.
To remove water, scale and bacteria growth, periodic exchange of fuel and filtering/treating is recommended to extend fuel life.
Water contamination of fuel during long-term storage provides a medium for bacterial growth, forming a dark slime which:
- Plugs filters
- Deposits on tank walls and pipes
- Swells rubber products that it contacts
Sulfur compounds are natural antioxidants, so low sulfur fuels (0.05 percent by weight) degrade quicker in storage.
Diesel fuels oxidize and form gums and varnishes which can plug fuel filters and injectors.
Because microorganism growth occurs in the fuel/water layer, the tank should be designed to minimize this interface, and water bottoms should be drained regularly.
Microbiocide additives, either water or fuel soluble, can be added to fresh fuel to inhibit microorganism growth. Consult your local fuel supplier for recommended additives.
In warm climates, large bulk storage diesel fuel requires full filtering every six months to one year.
Every two years the fuel should be completely changed to remove water, scale, bacteria growth, oxidized gums/resins, and minimize filter clogging due to fuel separation into components such as asphaltenes.