16
3-Way Check Valve – Provided on Hycomp model
compressors when two unloader valves are used.
This is a three-way check valve, used to prevent
the unloader control that is not currently unloading
the compressor from bleeding unload pressure to
atmosphere. The check valve is marked “inlet” and
“outlet”. Connect the “inlet” ports to the two unloader
valves, and connect the “outlet” port to the unloader
towers.
Three-Way Unloader Control Solenoid Valve
– Provided on air boosters and gas compressors with
suction valve unloading (Figure 11). The three way
unloader control solenoid receives an electrical signal
from a pressure switch to engage or release (load
or unload the compressor). The valve is designed
so that if electrical power is lost or the solenoid fails,
the valve will unload the compressor. There are
three gas ports on the unloader valve, as well as an
electrical connection. Port # 1 is the vent port. Port
# 2 is connected to the Unloader Towers or 3-Way
S
NO
PS
To Unloader
Pressure
Source
Vent (to atmosphere
or Compressor Inlet)
#3
#1
#2
Unloader
Tower
Figure 11: Three Way Unloader
Solenoid Valve Plumbing
Port #3 - to Unloader
Pressure Source
Port #1 - to vent
Port #2 -
to Towers
Check Valve. Port #3 is connected to the unloader
pressure source. If the port confi guration is different
than that listed above, it will be noted on the Piping
and Instrumentation Diagram.
If the unloader gas is air or a non-contaminating gas,
the solenoid can vent (Port #1) the gas to atmosphere.
If the unloading gas is a contaminating gas that cannot
be vented to atmosphere, then the solenoid must vent
this gas to the booster compressor suction line, or a
safe location. If this valve is part of a factory assembled
controls system, this port will be pre-plumbed or
tagged with piping instructions.
Port # 2 must be plumbed to the unloader towers or
three-way Check valve if a hydraulic unloader is also
used. If included as part of a Hycomp controls package,
the unloader valve (Port #2) is already plumbed.
Inlet Shutoff
Solenoid Valve,
wired and plumbed
to compressor,
requiring plumbing
to inlet gas piping
Port #3 must be connected to the gas source that
provides pressure for unloading. Use a minimum 3/8”
line to connect this port to the pressure source. If part
of a Hycomp controls package, this port may already be
plumbed to a ‘Tee’ connected to the discharge pressure
switch, so only one line needs to be brought back to
the unloader valve/pressure switch.
The Three-Way Unloading Solenoid Valve requires
an electrical signal (check the side of the solenoid for
the voltage requirement - usually either 120 VAC or
24 VDC) to operate. When power is applied to the
solenoid, it will cause the compressor to load. When
Figure 12: Inlet Shutoff Solenoid Valve
Unloading
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