The cleaning cycle is carried out automatically. The cover of the cleaning chamber is opened and the handling system draws the baskets that contain the dies to be cleaned in order to arrange them within the chamber.
The pickling solution is supplied from the holding tank to the chamber to the set level and the following bath movement, by means of a recycling pump at a temperature of 90-105°C, begins after the closure of the cover.
At the end of the cleaning cycle the bath is sent to the holding tank and the tank is filled with a first rinsing fluid. This fluid is then sent back to the first rinse storage tank and the tank is filled with a second rinsing fluid to finish the cleaning.
Now the tank is filled with a second rinsing water. After this second rinsing the fluid is sent back to the second rinse storage tank.
After the second rinsing and emptying the cover is opened and the baskets with the clean dies are brought to the unloading station.
This tank cover is not hermetic in order to allow the gaseous exhalations (H2) that form during the cleaning process to move away. Suction systems and ducts for the scavenging are foreseen in order to keep away the hydrogen that is formed.
The tank heating is carried out by a direct heating system equipped with a burner installed on the edge of the tank and supplied by methane gas which carries out the combustion within an exchanger with fume revolutions immersed in the tank itself. The system allows to obtain a high exchange efficiency that reduces the pre-heating time of the whole tank volume (approximately two hours). In order to improve the process outcome, two hydrodynamic agitation ramps are housed within the tank. Two ejectors have been installed on its top and their function is to maintain a high agitation within the solution by means of a pump placed on the tank for recycling. The same pump is used when the cleaning process is finished to carry out the emptying of the tank by transferring the solution in a stocking tank. The process tank is also equipped with two pneumatically operated half covers that reduce the pollutant emissions and consequently also the exposition of the operators is reduced. The installation of a densimeter is foreseen. According to the variation of the specific weight of the solution in saturation it warns the operator that the efficiency of the bath is reduced. According to the set point (previously set up by the plant manager in control board) the spent solution will be automatically transferred to the disposal tank or to an holding tank before the imission in the eventual caustic soda recovery system. It is important to emphasize that when the dies are taken away no fumes or hydrogen exhalation will come out since the tank, when open, is empty and the dies have been rinsed with water twice.