The controls are:
Two pinch valves
Two pressure regulating valves
Two solenoid valves, normally closed (N/C)
One solenoid valve, normally open (N/O), for venting
One check valve
The supply pressure controls the pinch valve. The operating pressure controls the vessel.
A safety valve opens at 7 bar (102 psi) and limits the maximum pressure in the vessel.
Pinch valve PV1 is operated by compressed air. It is controlled by SOL351.
There must be a minimum of 2 bar (30 psi) difference between the supply pressure PR1
and the operating pressure PR2 to ensure closure of the pinch valve. For best
performance, set PR1 to 5.5 bar (80 psi) and PR2 to 2.8 bar (40 psi). If the minimum
difference is maintained, you can adjust PR1 and PR2 to control the abrasive flow.
Proximity switch PS219 sends a signal to the PLC to indicate presence of abrasive. If
there is no abrasive, the PLC sends a signal to release the pressure from the vessel, and
then sends a signal to open the pinch valve. When the proximity switch senses abrasive
during refilling, a delay timer starts. When the delay timer ends, the pinch valve closes,
and the vessel pressurizes.
When SOL319 opens pinch valve PV2, pressure is released from the vessel to the silo.
© 2016–2017 Flow International Corporation
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