Operations and Maintenance Manual Universal Vacuum System
Version 1.2—March 2004 Page 23
Detailed Explanation of Purge Mode
As water from the vacuum tank drains (by gravity) into the drain tank, both floats rise.
When the water rises high enough, the upper switch closes, triggering the following events:
1. Solenoid 2 closes, shutting off pilot pressure to the three valves and causing them to
simultaneously changes states:
• Valve 1 (between the two tanks) closes, isolating the drain tank from the
vacuum tank.
• Valve 2 closes the vacuum supply line and opens the purge pressure line.
• Valve 3 (below the drain tank) opens.
2. The drain tank (isolated from the vacuum source) equalizes with atmospheric pressure
via the open drain valve.
3. After a short delay, solenoid 1 opens, supplying purge pressure to the drain tank,
pumping water out the drain.
4. As the water is drained, the lower float drops. When the float switch closes, solenoid 1
shuts off purge pressure to the drain tank.
5. Solenoid 2 opens, causing the pneumatic valves to simultaneously change back to their
normal operating states:
• Valve 1 (between the tanks) opens.
• Valve 2 switches back to vacuum supply.
• Valve 3 (below the drain tank) closes.
MANUAL PURGE
The orange purge indicator on the front panel of the vacuum system lights when the
system is in purge mode.
MANUAL WATER DRAIN
Turn the UVS power disconnect switch to the OFF position. Turn the UVS facilities
compressed air connection valve to the OFF position. It is strongly recommended to lock
out both the disconnect switch and the air valve before performing any maintenance on this
machine. The ¼" brass drain cock valve (part 111969) at the bottom of the drain tank can
be opened to drain any remaining water. Open it carefully at first to bleed off any
remaining air pressure.
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