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.
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