Friday, May 25, 2012

Production of RCC

Production of RCC is done according to the Client’s schedule and request. The concrete is produced continuously. However there are at times some breaks during operation. Some of these breaks are planned, like planned stops of concrete placement, regular maintenance of the equipment, meals, interferences with other activities in the Project, etc. Some others are not; for example, bad weather conditions, power cuts, etc.
The production at the RCC plant consists of the production of the following sub-systems:
(a) The water supply system.
Water is pumped from the river and cleaned and treated with a sedimentation and filtration system and is delivered to the main storage tank at a rate of 200 m3 per hour. It is then stored in the main storage tanks at the plant which has a storage capacity of 300,000 gals. The treated water is delivered to the plant accordingly.
(b) The cooling system.
The clear water that is delivered to the plant is chilled by the three Water Chillers and the temperature of water is lowered down to 4 deg C and pumped to the wet belt where the aggregates which are transported by a very slow conveyor are sprayed with chilled water. The dirty water is collected at the sedimentation tank and the sediments are separated and cleaned water is again recycled back to the water tank where the water is chilled and pumped back to the wet belt again for cooling and cleaning the aggregates. Additionally two ice plants are constructed inside the plant with a total capacity of 200 tons per hour and a variable amount if ice is added to the mixing concrete accordingly to get the required temperature of concrete.
(c) The conveying system.
The aggregates are transported by two lines of inclined and horizontal conveyors with a speed of about 1.67 m/s.
Three sizes of coarse aggregates are loaded onto the horizontal conveyor belt each separated by a spacing of 75 secs to deliver 400 tons per hour for each line. For the two lines the quantity that can be delivered is about 800 tons per hour, meeting the expected peak production demand. The aggregates are then transported by inclined conveyors and collected inside the inline silos by means of the distributing belts which deliver the different sizes of aggregates to different compartment inside the silos. The fine aggregate is separately transported by a different line of conveyor to its own compartment inside the silo. The whole system is automatically controlled from a control room.
(d) Storage and conveyance of cementitious materials.
Cementatious materials such as cement and pozzolan which are used in the RCC are produced and obtained from different locations and transported to the plant and are stored in 10 x 1000 ton cement and pozzolan silos.
They are conveyed to the 150 ton working silos from the plant by means of pneumatic blowing system which has a total capacity of 120 tons per hour and then delivered from the working silos to the mixers by means of screw conveyors.
(e) Concrete Mixing.
According to the mix design, the aggregates are automatically weighed on the weighing belts underneath the inline silos. Ice is weighed and added whenever necessary at the end of the weighing belt. Cement, Pozzolan, water and admixture are weighed separately and fed into the mixers. A very uniform concrete with a temperature of not more than 18 deg C and consistency (VeBe time) of 8 to 12 secs is produced to deliver to the placement site by trucks or by the RCC conveyor system.


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