This model of a batching plant is a device for production of ready mixed concrete. Ready mixed

concrete is a mixture which is produced from the stationary plant and brought to sites with special

drum mixers / Truck mixers with built in drum, mainly to sites closed to the mixing plant.

 

Following materials are used for production of ready mixed concrete:

- Aggregates = Sand and gravel in different sizes and compounds,

- Binders = Cement (eventually in various qualities)

- Water = Pure Water from the public net, partly dirty water (residual water)

 

In flow direction of the diagram the aggregates are stored in horizontal in-line silo boxes (No. 1).

 

The aggregates are loaded by a shovel dozer into the regarding box of the in-line silo, depending on

the grain sizes.

 

This in-line silo is a steel construction with a steel frame and support feet and generally consists in 5

silo boxes for various grain sizes and 5 electrically controlled, pneumatic driven double chutes (= 10

chutes) which are situated at the bottom end of the conical silo boxes (No. 2).

 

When the chutes open, the aggregates fall down to the belt weigher (No. 3) which is under the

complete length of the silos. When the required quantity (= weight) of gravel and sand is reached the

dosing chutes (No. 2) are closed again. The metering is a so-called standing metering which means

that the belt is standing still while the aggregates are batched. Only after the additional weighing of all

the aggregates they will be fed from the belt weigher into the bin of the skip hoist. (No. 4).

 

This bin (No. 4) is part of the skip hoist and brings the batched aggregates up. The skip hoist is

controlled in every position by proximity switches. All the functions can be executed only after the

position before was quitted. The operating system is safe in all his functions “Dosing” and “Mixing”

which makes sure that there are no double fillings or incorrect dosing actions by mistake. An electronic

device protects against slack rope and material defects of the rope.

 

When the mixer (No. 5) is ready to take the material, the skip drives from the waiting position into the

discharge position and unloads the aggregates into the mixer.

 

For the production of concrete there are needed also binders (cement) and water:

 

The dosing of the water is made from the water weigh batcher (No. 13). Pure water (No. 11 and 12)

from the public net is fed by a valve combination into the weighing bin. Dirty water can also be used in

a determined percentage in order to save pure water. The required quantity of water will be specified

from the recipe of concrete and from the consistency of the concrete.

 

In the cement silos (No. 8) the cement is stored. The cement is brought from cement tank trucks and

blown pneumatically into the silos (No. 7). At the bottom end of the conical silo outlets there are outlet

flaps (for maintenance work they are equipped by emergency hand flaps) with the cement screw

conveyors. At the silo top there are silo filters (No. 19) which grant a max. air pollution during filling

and operation of < 10 mg per cubic meter air. The cement dust falls back into the silo after filter cleansing.

 

The screw conveyors (No. 9) bring the cement from the cement silos into the cement weigh batcher

(No. 10). After the required weight is reached, the screw conveyors are stopped. Additionally there are

some after-running chutes which are driven pneumatically. They are going to stop immediately the

flow of the cement. Similar to the water weighing device also the cement quantity is determined by the

recipe of the concrete you want to produce.

 

After the weighing is over water and cement are given into the mixer by chutes automatically. The

dosing flaps of the cement and the water weigher are driven pneumatically and controlled electrically.

The material falls down to the mixer by gravity. For improving the outlet action the cement weigher is

equipped with a pneumatically driven beater. Even the cement weigher has an areation device for to

clean the air which is displaced by filling.

 

As an option there can be added admixes (for instance accelerators, retarders) (No. 14-17). They are

batched by dosing cylinders or special steel bins in small quantities into the mixer. The admixes are

used to control the setting time of the concrete depending from the requirements (distance to the final

customer, temperature, consistency. The required amount is determined by from the concrete quality.

 

When all the materials are batched and weighed they are put into the mixer dustfree.

 

The mixer is a so called pan mixer with centered rotor with mixing tools (paddle tips) and cleaning

tools (inner and outer scraper paddles). In the pan bottom there is a segmental discharge opening

door, hydraulically driven, which opens after a certain mixing time; through this door the ready mixed

concrete falls into the discharge cone (No. 6) with rubber trunk and into the truck mixer which waits

underneath the mixing plant.

 

The required compressed air is supplied from a compressor (No. 18). The air is needed for the

operation of the dosing flaps, filters etc.

 

An electric control system with power supply and control panels allows to control the complete

batching plant automatically or by hand operation. All functions can be monitored and surveyed or

executed by hand (No. 21).

 

All weigh batchers are made in accordance to the rules and laws of the “Physikalisch-Technischen

Bundesanstalt in Braunschweig (PTB)” and are ready for verification and calibration.

 

Emission Mixer:

The mixer creates max. 85 dB (A) in operation.

 

Immission Mixer:

During the filling of the mixer there is immission because of the displaced air. This immission is

stopped by a filter system (No. 20) which runs before the mixer is filled and which creates some

underpressure within the mixer. The filter is equipped with a 9,2 m² filter area and cleans the air

which is displaced during the feeding of the mixer. The required quantity of air is set as standard

from the manufacturer and is approx. 5 s. approx. 25 l = 150 l normal air at 6 bar operating

pressure. The cleaning of the filters is made continuously by air shock waves in opposite

direction.

 

Immission Cement Silo:

During the filling action of the cement silos there is immission. The cement is fed pneumatically

with compressed air by the silo trucks. A filter unit (No. 19) on the silo roof guarantees best

immission control. Quantity of remaining dust max. 10 mg per cubic meter air.

 

Another immission source is the cement weigher when it is filled. Also the cement weigher is equipped

with a sufficient working areation unit.

 

The flow diagram for cement is closed from the filling by tank trucks until the mixer. Here all

components are mixed in a non-polluting way with water and so binded in a non-polluting way.