الفهرس 
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Abstract
Many flammable products are stored in large tanks at atmospheric pressure.
Ignition of a hydrocarbon– air mixture in such tanks can lead to an explosion
and cause lethal casualties or damage the surrounding facilities and buildings.
To apprehend this, safety distances for humans, structures and equipment need
to be defined. Several simple methodologies have been set up to estimate safety
distances in case of an atmospheric storage tank explosion.
In case of liquid storage tank has been designed regardless of international
standards and there is little interest with its operating conditions, it may lead to
fully or partially failure. This thesis presents a study for a failure of Toluene
storage tanks with different capacities. Toluene is a liquid aromatic hydrocarbon
C7H8 which is toxic, flammable, and may cause boiled liquid expanded vapor
explosions (BLEVE). Secondly, a literature review of such cases of storage tanks
failure from different point of views. Thirdly, failure analysis was performed to
determine the root causes of toluene storage tanks failure as well as corrosion
influence. Fourthly, finite Element analysis (FEA) was performed for edge
welding of tank roof and top shell zone. The main objective of the present work
is to develop a relation between weld electrode size and tank diameter at each
type of weld electrode. The results show that weld electrode mean size is
increased by increasing of tank diameter. If weld electrode strength decreases, it
will cause of increasing electrode weld size. High levels of internal vapor
pressures should be cause of high weld electrode strength and size selection. It
also determines the main framework of roof to top shell welding process. One
of the most important goals of this study is to develop a relation between tank
diameter and maximum stresses that resulted at every amount of vapor pressure according to von-Mises stress theory. The optimum roof to top shell welding size
is obtained through the circumference welding path. The results of analysis
allowed engineers to design the tank according to American Petroleum Institute
(API 650) and to attain useful the recommendations for hydrocarbons (toluene)
storage tanks operation. It is found that vapor pressure does not exceed 0.1 MPa and
alarm safety pressure released valves should be installed with nominal value less than
0.1 MPa.