8. Remote control and emergency shut-downs
Remote control
When the blasting operator operates the biased off-switch an electronic signal is sent to the electro-pneumatic control. The remote control valve opens the supply unit of compressed air and closes the safety-valve. The closing cone is pressed upwards and loaded with pressure. If the pressure has formed in the pot the abrasive flows through the dosing valve at the pot bottom into the compressed-air stream. The loading factor can be adjusted very easily and precisely with the dosing valves DV-80 and ADV-80. By using the dosing valve ADV-80 the blasting operator has got the opportunity to interrupt the supply of abrasive via the electro-pneumatic remote control. If the blasting operator releases the biased off-switch the remote control valve closes and the pot will be ventilated. The compressed air in the pot that escapes via the hose supports closing of the remote control valve.
Emergency shot-down
An emergency shut-down unit will be a supplement to the normal remote control completely installed in a case.
This unit consists of a double-effective pinch valve and is coupled as close as possible directly behind the nozzle into the blasting hose. In case of risk the blasting operator releases the emergency show-down. By this the control circuit is getting current-less; the pinch valve closes the blasting hose. At the same time, it opens the closure of the ventilation hose so that the mixture of compressed air /abrasive being in the hose between switching off unit and nozzle can escape suddenly. By this the entire system is immediately without pressure and thus not dangerous.
The switching function of the normal remote control is not impaired; the blasting pot can be handled as usual with the following functions at the nozzle:
- compressed air on/compressed air off
- in addition, the function
abrasive on / abrasive off can be still switched according
to the respective equipment of the blasting pot.
By this it will be possible to perform the filling process or to blow off abrasive from the blasted object.
Flow chart emergency shut-down without operating biased switch-off
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Flow chart emergency shut-down with operating biased switch-off
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