Description Of Operation – Dryer; Models 40 To 450 W/ Shuttle Valve - Gardner Denver DGH Series Instruction Manual

3. Description
3.3 Description of Operation – Dryer

3.3.1 Models 40 to 450 w/ Shuttle Valve

(Refer to Fig. 3-1a.) Compressed air flows through inlet
switching valve (3A) (normally open) to tower (4A) where the air
is dried. After the air is dried it flows through shuttle valve (5)
and then to the dryer outlet. A portion of the dry air, the purge
stream, branches off from the main air stream prior to the outlet.
The purge stream flow rate is controlled by the adjustable purge
rate valve (6) and the two purge orifices (7).
The purge flow, which has been throttled to near atmospheric
pressure, is directed to tower (4B). As the purge flow passes
over the desiccant in tower (4B), it removes the water vapor,
which was deposited there while the tower was on-line drying.
The purge air then passes through purge and repressurization
valve (9B) (normally closed) and purge muffler (10B) to the
atmosphere.
After regeneration, purge and repressurization valve (9B)
(normally closed) closes allowing tower (4B) to re-pressurize
slowly. Adequate repressurization time is allowed so that tower
(4B) is fully re-pressurized before tower switchover. After a
controlled time period, air inlet switching valve (3B) (normally
open) opens and inlet-switching valve (3A) (normally open)
closes, purge and repressurization valve (9A) (normally closed)
then opens.
(Refer to Fig. 3-1b.) Tower (4B) is now drying the main air
stream while tower (4A) is being regenerated by the purge air
stream. The operation of the inlet switching (normally open) and
purge and repressurization (normally closed) valves is
sequenced by the control system located in the electrical
enclosure.
3. Description
TOWER
4A
TOWER
4A
1. Tower Pressure Gauges
2. Purge Pressure Gauge
3. Inlet Switching Valves
4. Desiccant Drying Towers
5. Shuttle Valve
6. Adjustable Purge Rate Valve
7. Purge Orifices
Process Stream
Purge Stream
- 4 –
OUTLET
11
5
1 1
8
7 7
6 2
TOWER
3A 3B
9A 9B
INLET
10A 10B
FIGURE 3-1a
TOWER 4A DRYING
TOWER 4B REGENERATING
OUTLET
11
5
1 1
8
7 7
2
6
TOWER
4B
3A 3B
9A 9B
INLET
10A 10B
FIGURE 3-1b
TOWER 4A REGENERATING
TOWER 4B DRYING
8. Safety Valve
9. Purge and Repres-
surization Valves
10. Purge Mufflers
11. Moisture Indicator
A Left Tower Suffix
B Right Tower Suffix
4B