Generators produce electricity during power outages. This electricity production is achieved by converting the mechanical energy generated by the combustion of fuel into electrical energy. If there is no fuel available in the generator during a power outage, the generator cannot function when needed. Therefore, fuel storage should be done to prevent such a possibility from occurring. Fuel is stored in a specially designed fuel tank. When choosing and installing the appropriate fuel tank, various points should be considered.
Determining Fuel Tank Capacity
When determining the capacity of the fuel tank, the first thing to do is to determine how much fuel will be needed. You can calculate the minimum storage capacity by estimating the following three parameters;
(1) Urgent Stock: How much fuel is needed in case of excessive consumption and delays after a power outage?
(2) Supply Time: How long does it take to supply the fuel from the seller to the generator location?
(3) Lead Time Storage: What is the amount of fuel to run the generator until I supply fuel from the dealer?
Based on the three parameters above, the minimum amount of storage is determined as adjacent:
Minimum storage capacity = Urgent Stock + Lead Time Storage
What is the optimal fuel storage capacity?
In the event of short-term power outages, a smaller storage tank will suffice for the fuel requirement. However, due to the small size of the tank, you need to buy fuel more often and in small quantities. Because of the small tank, your cost will be low when purchasing the generator; but then the amount of fuel consumed per unit becomes higher. Large storage tanks are used in large commercial establishments or in areas where power outages are frequent and prolonged. In this case, you can buy fuel less often, but in larger batches. However, your cost will be high when purchasing the generator. At the same time, maintenance costs will be high in the long run. On the other hand, the amount of fuel consumed per unit decreases. However, you also need to calculate the hidden cost of the hazards associated with storing a larger amount of fuel.
Types of Fuel Tanks
Generator fuel tanks are generally three types:
- Sub-Base Tanks
- Underground Storage Tanks
- Overground storage tanks
If you are storing less than 1,000 gallons of fuel, you can use the base of the generator as a fuel tank. As the name suggests, the sub-base tanks are fixed to the base surface of the generator set. Sub-base tanks are rectangular cross-section and double-walled tanks. This increases the durability of the tank against any leakage. Both tanks are constructed using heavy steel welding. Tank filling system; The inlet valve must be designed to close automatically when the tank is 95% full. After loading is completed, the primary tank is tested at 5 psig and the secondary tank at 3 psig.
Underground Storage Tanks
If they need to store more than 1,000 gallons of fuel, they can choose underground storage tanks or Overground storage tanks. Underground storage tanks are shielded because they last longer but are more costly than sub-base tanks. Underground storage tanks can be constructed from glass fiber reinforced plastic. These tanks are usually multi-grooved to ensure their structural strength. Alternatively, underground storage tanks can be fabricated from steel but with appropriate cathodic protection against corrosion from ground water. Likewise, the pipe from the underground storage tank for the generator can be glass fiber reinforced plastic or steel with cathodic protection.
Leaks and spills in underground storage tank systems can be expensive and difficult to fix. Such systems should be equipped with overflow and spill prevention equipment and procedures. In the worst case scenario, the installation of underground storage tanks should be such that a fuel spill or leak is contained in a confined space. Therefore, the underground area is surrounded by concrete floors and walls. After underground storage tanks are loaded in this area, the outer zone is filled with sand and gravel.
Overground Storage Tanks
As the name suggests, these tanks are mounted above the ground. While the structural features of these tanks are similar to those of underground tanks, the installation procedures vary widely. The reason for this is the different factors that need to be considered in order to minimize the dangers. Aboveground tanks pose a fire hazard with a risk of spreading to other nearby facilities. For this reason, these tanks should be at a distance that will not affect such facilities. Trenches should be built around the tank for possible leaks. The volume of the trenches should generally be 110% of the tank volume. Over ground storage tanks must be protected from the weather by suitable protective structures.
Approvals and Standards
Fuel tanks and accompanying piping systems must be approved prior to diesel generator installation. Only tanks with lower capacities can be exempted from approvals. Product information and forms such as fabrication drawings, piping design and manufacturer’s installation instructions should be supplied alongside the tank.
Various standards must be followed during the fabrication and assembly of generator fuel tanks. The NFPA relevant sections for generator fuel tanks are NFPA30 and NFPA37.