Cylindrical steel tanks



Types of steel tanks

Stiffening of membrane of single deck floating roof

Methods of erection

Typical damages of aboveground steel tanks

Inspection of steel tanks

Realized projects of tanks

Typical drawings of tanks


About the author

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During their exploitation the above ground steel tanks bear unfavorable influence of the environment and stored product. As a result their status becomes worse and many damages are collected into a tank's structure. These damages can cause serious failures of the steel facility.
Referring to this thesis the author visited many oil storage bases, where he saw and evaluated the current damages of the tanks in the exploitation.
The correctness of one design decision could be better evaluated after determined period of exploitation of the facility. Different constructive solutions taken during the years can cause different damages of the above ground steel tanks.

Damages on steel tanks, occuring during etheir xploitation, could ba classified as follow:

1. Deviation of design geometric shape:
- local loss of stability;
- total (of whole tank) loss of stability;
- deviation to inside or outside of shell and / or bottom;
- movement and / or bending of annular bottom plates.

a) plane settlement:
- settlement of the
whole bottom;
- settlement of the perimeter of  tank.

b) irregular settlement:
- inclined tank;
by the whole bottom;
- by the perimeter of the tank;
- key on the floating roof with damages of antirotation device, supports and equipment;
- tearing of supporting roof columns from the bottom.

2. Damage of corrosion
- corrosion of welds;
- corrosion of steel structure.

a) the corrosion has regular distribution;

b) local corrosion.

Pictures below show typical damages that could be met in aboveground steel tanks in service

corrosion of anchors
Corrosion of anchors

Bottom setlement
Settlement of the tank
Settling if the tank in the foundation
Sinking in foundation
Lifting of tank and plants under bottom

Cavity under steel annular bottom plates
Cavity under the steel bottom

Corrosion on tank's shell inside
Corrosion of shell inside the tank
Corrosion of the roof
Corrosion of roof plates

Corrosion under heat insulation
Corrosion under heat insulation
Internal corrosion on bottom plates
Corrosion of bottom plates

Plant to the tank ladder
Plants on spiral stairway

Local deformations of the tank's shell
Local deformations of the shell
Shell distortion
Deviation of shell into inside
Surface damages
Surface damages, lap joints
 and reinforcement of welds
Lap vertical joints
Lap vertical joint in the shell
Water on floating roof
Holding of a water on the floating roof