AEC Continuous Vacuum/Pressure Conveying Systems - Manual (Page 46)

Single- and Dual-Blower Continuous Vacuum/Pressure Systems Page 45
The vacuum/pressure system shuts down if the vacuum switch senses vacuum
greater than 14 in. Hg (406.8 millibars). The vacuum switch is nonadjustable
and therefore needs no adjustment.
The most common cause of high vacuum is plugged filters. When system
vacuum rises above the setting on the switch, the switch closes and begins the
purge cycle. After a preset time, the whole system shuts down.
IMPORTANT!
Do not tamper with the vacuum switch.
Doing so voids your vacuum pump warranty!
Pressure Switch
The pressure switch protects the pressure pump from high amp damage if a
material line blockage occurs during conveying. The pressure pump shuts down
if the pressure switch senses air pressure greater than 6 psig (41.37 kPa/0.414
bars).
The pressure switch is adjusted at the factory and needs no adjustment.
IMPORTANT!
Do not attempt to adjust the pressure switch.
It was pre-set at the factory.
Doing so voids your pressure pump warranty!
Pressure Relief Valve
The adjustment for pressure relief is factory-set at about 1 psig (about 7 kPa/70
millibars) above the maximum allowable pressure set on the pressure switch. It
is located on the pressure unit.
The main cause for high pressure is a blocked material line on the pressure
side. When air pressure overcomes the spring tension on the mechanical
adjustment, the valve opens and relieves the pressure. The pressure relief valve
serves as a mechanical backup for the pressure switch. The pressure switch
should trip and shut down the pressure pump before the pressure relief valve
opens.