The most common flammable substance that is typically stored in plastic fuel tanks is gasoline or fuel; however other flammable substances such as butane, motor oil, transformer oil, gas oil and natural gas can also be stored.
Plastic fuel tanks have numerous advantages over metal fuel tanks. These advantages include being lighter weight than most metals, more durable, offer improved compartment space utilization, increased convenience, cost-efficiency and safety due to being non-explosive. Plastic fuel tanks are also flexible, which allows for the expansion of vapors and bending during an accident.
Plastic fuel tanks can be a part of the engine system where the fuel is stored and propelled by a fuel pump in, or released into an engine in cars, trucks, motorcycles, AGVs, boats and more, they can be stationary above ground or they can be manually transported by hand. Plastic fuel tanks are essential in industries such as automotive, aerospace, construction, industrial, commercial, petroleum, marine and military. Typical configurations of plastic fuel tanks include rectangular, cone bottoms, horizontal, cylindrical and vertical.
Poly fuel tanks are molded into a seamless one-piece construction that typically consists of at least six layers of a given material, or several different materials that provide different beneficial characteristics. Typically, plastic fuel tanks are made from these five different materials: high density polyethylene (HDPE), polypropylene (PP), regrind plastic (recycled polyethylene), a plastic adhesive or ethyl vinyl alcohol (EVOH).
These storage tanks can be formed by rational molding or blow molding processes. The rotational molding process begins with a heated mold that causes the plastic within to melt; thus forming a puddle at the bottom of the mold cavity. Next, the mold is slowly rotated, usually around two perpendicular axes, resulting in the melted plastic flowing into the mold and sticking to its walls.
The last part is the cooling phase in which the mold continues to rotate so that an even thickness is maintained throughout the gas tank. The blow molding process begins with melting down the plastic and forming it into a parison, a tube-like piece of plastic with a hole in one end in which compressed air can pass through.
Next, a pressurized gas, usually air, is used to expand the hot parison and press it against a mold cavity. The pressure is held until the plastic is cooled. Once the plastic is cool and hardened the mold opens up and the part is ejected. Rotationally molded plastic fuel tanks will be stronger; whereas blow molded plastic fuel tanks will be more susceptible to weakness in the walls.