PRE-STRESSED CONCRETE

TANK

EGG-SHAPED DIGESTERS

Pioneer of the PC Technology

Egg-Shaped Digesters
The Egg-Shaped Digesters (ESDs) are often used as sludge digester because they have effective shape asa mole efficient digestion process. The use of ESDs has proven to be advantageous about the sludge
digestion process and is gradually becoming more common. The sediments flow to the bottom of the coneby the curved surface shape, and can be easily and continuously removed.
Conversely, a crust of light particles forms on the surface of the sludge. Because their surface area issmaller than that of circular tanks, crust removal becomes easier and more efficient.
Post-tensioning tendons are used vertically and horizontally in this type of tank. Vertical tendons are
typically looped, anchored in lower lifts and foundations, and extend through subsequent lifts. Horizontal
tendons are often stressed at blockouts, hence buttresses are not needed.
Construction of digester tanks (ESDs) usually progresses in horizontal rings, where post-tensioning isapplied in the circumferential and vertical directions.
Pioneer of the PC Technology
ABE NIKKO

Pioneer of the PC Technology

ABE NIKKO KOGYO CO., LTD.
Gifu Head Office
Tokyo Head Office
Sri Lanka Office

3-13-3, Rokujyo-Ohmizo, Gifu-shi, Gifu, JapanSK Building-S, 3rd Floor, 2-3-18, Shimo-ochiai, Shinjuku-ku,
Tokyo 161-0033 Japan
12A, Bawa Place, Colombo 08, Sri Lanka

WEB : http://www.abe-nikko.co.jp/
PHONE : +81-58-271-3391 FAX: +81-58-273-3796
PHONE : +81-3-5906-5631 FAX : +81-3-5906-5270
PHONE : +94-77-0721643

E-MAIL：srilanka@abe-nikko.co.jp

CharacteristicsI.

COMPLETE WATER TIGHTNESS(leak-free structure)
The PC tank is reinforced by high-strength steel wires and bars (PC tendons) placed in the verticaldirection, and in the horizontal direction.
That is, a compression stress is introduced beforehand to prevent the induction of tensil stress (arisewith water pressure )which is a weak point of concrete. Therefore, the pre-stressed concrete is free fromcrack and water leakage.

II. LOW CONSTRUCTION COST
Since the cylindrical tank which is rational form can reduce the material to be used, it is economical.
Because the cylindrical PC tank can make a water level more high , it can store mass water in narrow
land.
It is effective in the expensive urban areas of land.
III. RUST-FREE AND CORROSION-FREE
Because the concrete has water resistance in itself, the steel materials which are Reinforcing bars andPC tendons, etc. are completely protected from corrosion caused by the infiltration or leakage of water.
In addition, the PC tank is protected from corrosion caused by the chlorine used for sterilization or bysulfides to be generated in sewage.

IV. EXCELLENT COLD-RESISTANCE AND HEAT-RESISTANCE
Generally, the heat permeability of rich-mix concrete is lower compared with steel. On the other hand,
cold- resistance and heat- resistance is higher.
Furthermore, it is adaptable to local changes in temperature by the excellent elasticity.
V. HIGH EARTHQUAKE RESISTANCE
As mentioned above, pre-stressed concrete is excellent in elasticity.
VI. HIGH RESISTANCE AGAINST GROUND SUBSIDENCE
The above-mentioned means that P.C tanks are highly resistant to the subsidence of ground.