Asphalt batch plants controls fall into three categories, depending upon the degree of automation used in the operation of the plant:-
• Manual
• Semi-automatic
• Automatic
It is normal in all these systems for the power control of the weighing and mixing process to be automated. Even in the so called manual plants, air or hydraulic cylinders activated by electric switches have replaced hand lever systems. They operate supply bin gates, feeders bitumen valve and the weigh batch and pugmill discharge gates.
In semi-automatic plants, all operations from the weigh batch to pugmill discharge are under automatic cycle control. The entire measuring and mixing phase of the plant is handled automatically.
In a fully automatic system an operator would:-
(a) Select the total weight required to be carried by the truck.
(b) Select the mix required either by pressing a button for say one of the six most common mixes or by inserting the appropriate punch card into the control panel.
(c) Wait for results.
The automatic mechanisms do the rest including monitoring the mix temperature, hot bin levels, weighing materials, controlling mixing times and mixing the correct number of batches and part batches to fill the truck.
(b) Continuous Plant Controls
The inherently automatic operation of the continuous mix plant can be extended by the addition of several additional automatic controls, viz:-
(a) Automatic burner controls
(b) Automatic mix discharge
(c) Automatic mixer and gradation cut-offs in case of hot bin shortage or improper feed
(d) Electric interlocks which shut down the plant in case of failure anywhere in the
system.
This Asphalt Batch plants Controls can be change with technology.