9. Storage Tanks
Tanks and Storage Equipment
General
Storage of liquid materials is commonly accomplished in industrial
plants by use of cylindrical, spherical or rectangular tanks. These tanks
may be constructed of wood, concrete, or metal, with metal being the
most common material of construction.
The design of storage vessels involves consideration of details such as
size and number of openings, shape of heads, necessary temperature
and pressure controls and corrosive action of the content.
The necessary wall thickness for metal vessels is a function of:
1.
The ultimate tensile strength or the yield point of the metal at the
operating temperature.
2.
The operating pressure
Tanks and Storage Equipment
General
1.
The ultimate tensile strength or the yield point of the metal at the
operating temperature.
2.
The operating pressure
3.
The diameter of the tank
4.
Joint or welding efficiency
5.
Various codes are available which specify the conditions that must
be met for different vessels.
STORAGE TANKS
Storage tanks can be divided into the following types:
1.
Atmospheric storage
2.
Pressure storage
3.
Refrigerated storage
Storage Tanks
1. Atmospheric storage Tanks
- Applied to tanks operating at or near atmospheric pressure.
- They are used to hold liquids which will not vaporize at ambient
temperature.
Storage Tanks - Atmospheric Tanks
Atmospheric tanks are categorized primarily as follows:
1. Open top (no roof)
- has no roof and may store or process non-volatile liquids such
as water, brine, etc.
2.
Fixed roof
- Fixed roof tanks, such as cone roof or umbrella roof are used to
store low vapor pressure liquids which will not vaporize at
temperature below 120oF.
- Generally used for gas oil, water, chemicals.
3.
Floating roof
- Floating roof such as hard top pan and pontoon roof types
eliminate the vapor space above the liquid, allows storage of
higher vapor pressure materials.
- Generally used for crude oil, gasoline, napthas
Hard Top Fan Floating Roof Tank
Storage Tanks - Pressure Storage Tanks
2.
Pressure storage tanks
– applies to vessels designed to withstand pressures sufficient to
keep liquid stored from vaporizing. Used for high vapor pressure
liquid such as butane, propane etc.
Spheres
- Generally used to store high vapor pressure liquid
Advantage is that it can contain the greatest
amount of liquid for a given amount of steel.
- A sphere can also withstand greater pressures with
a given plate thickness than cylindrical vessels.
Storage Tanks - Refrigerated Storage Tanks
3. Refrigerated storage tanks
- refers to low temperature/cryogenic storage
- This type is used for gases that liquefy under pressure at
atmospheric temperature.
- In cryogenic storage the gas is at, or near to, atmospheric
pressure and remains liquid because of low temperature.
•
Cryogenic refers to temperature below -10oC
Storage of Gas
•
Bulk transport of fluids
1. Pipe lines
2. Tank cars (railroad)
3. Tank trucks
4. Portable tanks, drum, or bottles
5. Sea going tankers
6. Container ship