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

first page


 This is another method to removing the deformations of the membrane of single deck floating roof. This method can be used together with stiffening girders in order to assure complementary stability of the roof. When the additional pontoon in the center of the roof is mounted it is necessary to take into consideration the increased sink of the floating roof.
This method can be applied only when the roof is able to carry the complementary weight of the pontoons.
The new steel bodies are empty. Then they are formed as pontoons, which assure the additive possibility for floating of the roof. In order to assure the necessary weight these additive constructions can be made with thick plates.
It must be noticed that setting of complementary pontoons upon the membrane has the following priority comparing the stiffening girders:
- lower expenses for metal;
- the complementary pontoons enable the roof to float in case of punctured membrane or when the drain does not functions properly.

Setting of one pontoon in center of the membrane

Single deck floating roof with central pontoon
Single deck floating roof with pontoon in the center

- because
pending of the membrane is increased it is stretched;
- because
slope of the roof from loading is increased in the center the drain of the poured above water is better;
- the movements and vibrations caused by the wind are considerable decreased;
- the number of the welding joints is smaller in comparison with  the stiffening girders.

- the pontoon in the center of the roof coincides or is close to the drain system. It is necessary to have more complicated and labor consumption detail for assuring of properly drain of the water:
- the level of sink of the floating roof is increased;
- the efforts in the roof membrane, pontoons and supports are increased:
- it is possible that the membrane swells  between the periphery and the supports as a balloon, if it is not complementary stiffened with ribs;

 Setting of many pontoons evenly upon the membrane

Many pontoons above the membrane of single deck floating roof
Many pontoons upon the membrane  (The Hendrix Group)

- membrane is stretched because of the increased loading respectively pending  of the membrane;
- the drain of the water fallen there is improved;
- the vibrations and movements caused by wind are decreased;
- the loading of the pontoons is even upon the whole membrane which does not allow the swelling of the liquid steam as a balloon.

- the level of sink of the roof is increased;
- the efforts in membrane of the roof, in the pontoons and in supports are increased;
- the number of the weld joints is increased;
- the consumption of the metal is increased compared to one pontoon in the center of the membrane.

On the point of view of the exploitation this solution is good, and the deviation of the membrane from its project shape are decreased.

main EN page