1. Term Project Report
on
ABOVEGROUND FUEL STORAGE TANKS
Prepared by:
Subkhiddin MUKHIDINOV
Submitted to:
Prof. Şafak 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:
Storage of fuel: the system must contain a given quantity of fuel and
must avoid leakage and limit evaporative emissions.
Filling: the fuel tank must be filled in a secure way, without sparks.
Provide a method for determining level of fuel in tank, gauging (the
remaining quantity of fuel in the tank must be measured or evaluated).
Venting (if over-pressure is not allowed, the fuel vapors must be
managed through valves).
Feeding of the engine.
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.
