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Aboveground Fuel Storage Tanks
- 1. Term Project Report on ABOVEGROUND FUEL STORAGE TANKS Prepared by: Subkhiddin MUKHIDINOV Submitted to: Prof. Åžafak YILMAZ ISTANBUL TECHNICAL UNIVERSITY School of Mechanical Engineering
- 2. FUEL STORAGE TANKS INTRODUCTION Storage tanks operate under no pressure, distinguishing them from pressure vessels. Storage tanks are often cylindrical in shape, perpendicular to the ground with flat bottoms, and a fixed or floating roof. There are usually many environmental regulations applied to the design and operation of storage tanks, often depending on the nature of the fluid contained within. Above ground storage tanks differ from underground storage tanks in the kinds of regulations that are applied. Storage tanks are available in many shapes: vertical and horizontal cylindrical; open top and closed top; flat bottom, cone bottom, slope bottom and dish bottom. Large tanks tend to be vertical cylindrical, or to have rounded corners transition
- 3. from vertical side wall to bottom profile, to easier withstand hydraulic hydrostatically induced pressure of contained liquid. Most container tanks for handling liquids during transportation are designed to handle varying degrees of pressure. DESCRIPTION A fuel tank (or petrol tank) is a safe container for flammable fluids. Though any storage tank for fuel may be so called, the term is typically applied to part of an engine system in which the fuel is stored and propelled or released into an engine. Fuel tanks range in size and complexity from the small plastic tank of a butanelighter to the multi- chambered cryogenic Space Shuttle external tank.
- 4. USAGE Typically, a fuel tank must allow or provide the following: ï‚· Storage of fuel: the system must contain a given quantity of fuel and must avoid leakage and limit evaporative emissions. ï‚· Filling: the fuel tank must be filled in a secure way, without sparks. ï‚· Provide a method for determining level of fuel in tank, gauging (the remaining quantity of fuel in the tank must be measured or evaluated). ï‚· Venting (if over-pressure is not allowed, the fuel vapors must be managed through valves). ï‚· Feeding of the engine. ï‚· Anticipate potentials for damage and provide safe survival potential. Plastic (high-density polyethylene HDPE) as a fuel tank material of construction, while functionally viable in the short term, has a long term potential to become saturated as fuels such as diesel and gasoline permeate the HDPE material. Considering the inertia and kinetic energy of fuel in a plastic tank being transported by a vehicle, environmental stress cracking is a definite potential. The flammability of fuel makes stress cracking a possible cause of catastrophic failure. Emergencies aside, HDPE plastic is suitable for short term storage of diesel and gasoline. In the U.S.,Underwriters Laboratories approved tanks would be a minimum design consideration.
- 5. DESIGN Important considerations in designing a diesel fuel tank are determining placement, choosing the shape and calculating the required volume. Side mounting is the most common placement of diesel tanks for trucks. This is typically accomplished with the use of brackets, straps or a combination of both for the purpose of attaching the fuel tank to the truck frame. The choice of shape is generally influenced by the need for maximum fuel capacity and the desire for a stylish look. The most common diesel tank designs are cylindrical, rectangular and D-Style tanks. Cylindrical designs are often selected for their visual appeal while the rectangular tank is most often employed to maximize fuel volume for a given space. The D-Tank, as its name implies, is actually a hybrid of the cylindrical and rectangular designs. It offers the curved visual appeal of a cylindrical tank with significantly more fuel volume. Replacing a cylindrical fuel tank with a D-Tank can result in 46% additional fuel capacity. When calculating volume requirements, one would begin by assessing the available space. Once length, width and height restrictions have been ascertained, the easiest method of determining volume is with the use of a truck tank volume calculator. Although basic mathematics can be applied to calculate the volume of a cylinder, calculating that of a rectangular tank is more complex due to the rounded corners. Designers must take into consideration the loss of volume due to the radius of rounded corners.
- 6. MATERIALS Material selection is one of the key considerations in producing fuel tanks. The three most common materials used in the manufacture of fuel tanks are aluminum, steel and stainless steel. Regardless of the choice of material, the quality of the selection must be such as to allow that material to be malleable enough to be bent, rolled and stamped into formation. Aluminum alloy 5052 H32 is a popular choice for fuel tanks as it contains adequate magnesium content to allow the material to be pliable enough to meet the needs of the manufacturing process. The majority of diesel tanks manufactured today are made of steel; however truck operators may elect to choose aluminum fuel tanks when replacing older tanks on their vehicles. Aluminum offers advantages of lighter weight and resistance to corrosion. The selection of steel and stainless steel should be that of prime grade material. An important consideration in manufacturing is choosing material suitable for stamping and bending. The material must be ductile enough to be bent and formed yet thick enough to provide strength and to accept a weld. This is especially true for tanks of a design that require sharp bends.
- 7. MANUFACTURING While most tanks are manufactured, some fuel tanks are still fabricated by metal craftsmen or hand-made in the case of bladder-style tanks. These include custom and restoration tanks for automotive,aircraft, motorcycles, and even tractors. Construction of fuel tanks follows a series of specific steps. The craftsman generally creates a mockup to determine the accurate size and shape of the tank, usually out of foam board. Next, design issues that affect the structure of the tank are addressed - such as where the outlet, drain, fluid level indicator, seams, and baffles go. Then the craftsmen must determine the thickness, temper and alloy of the sheet he will use to make the tank. After the sheet is cut to the shapes needed, various pieces are bent to create the basic shell and/or ends and baffles for the tank. Many fuel tanks' baffles (particularly in aircraft and racecars) contain lightening holes. These flanged holes serve two purposes, they reduce the weight of the tank while adding strength to the baffles. Toward the end of construction, openings are added for the filler neck, fuel pickup, drain, and fuel-level sending unit. Sometimes these holes are created on the flat shell, other times they are added at the end of the fabrication process. Baffles and ends can be riveted into place. The heads of the rivets are frequently brazed or soldered to prevent tank leaks. Ends can then be hemmed in and soldered, or flanged and brazed (and/or sealed with an epoxy-type sealant) or the ends can be flanged and then welded. Once the soldering, brazing or welding is complete, the fuel tank is leak-tested.