5 – 3
VSG/VSSG • Installation, Operation and Maintenance Manual •Vilter/Emerson • 35391STG
Section 5 • Maintenance/Service
2. If equipped with equalizing solenoid to control suc-
tion by-pass, allow solenoid to remain open until
pressures equalize, see Figure 5-1 (2 of 2).
3. Turn motor and oil pump starter disconnect switch-
es into the OFF position. Lockout/tagout discon-
nect switches.
4. If equipped with manual suction by-pass valve and
it is not open, open suction by-pass valve to allow
oil separator pressure to vent to low-side system
pressure, see Figure 5-1 (1 of 2). Close suction by-
pass valve when complete.
5. Isolate the compressor unit by closing all valves to
the house system. Lockout/tagout valves.
NOTE
If drain valves are installed on suction and discharge
headers, open these valves too to remove build up
of liquid during shut-down periods.
6.
Open any other valves that may trap liquid. Lockout/
tagout valves.
7. Recover or transfer all gas vapors.
8. Open discharge pressure bleed valve at block and
bleed assembly and allow remaining pressure in oil
separator to equalize to atmospheric pressure.
9. Servicing the compressor unit can proceed at this
point. After servicing, ensure to perform a leak
check, see Compressor Unit Leak Check procedure.
Compressor Unit Leak Check
The compressor unit must be checked for leaks after
servicing to ensure a tight system. For additional leak
testing information, refer to Chapter VI of ASME B31.3
Process Piping Code.
CAUTION
Do not hydro test compressur unit. Failure to comply
may result in damage to equipment.
1. If servicing the compressor unit was completed,
proceed to step 2. Otherwise, isolate the compres-
sor unit from the house system, see Compressor
Unit Isolation procedure.
2.
Open all shut-off valves, check valves, control valves
and solenoid valves in the system to be tested.
3. Slowly pressurize compressor unit through suction
oil charging port with dry nitrogen.
4. Using appropriate soap solution, check for leaks on
joints and connections of the serviced component.
5. If leaks are found, depressurize system and
fi
x leaks.
Repeat steps 3 and 4 until all leaks are
fi
xed.
6. Typically, no evacuation is required for open loop
systems. If evacuation is required, evacuate from
suction oil charging port. Otherwise, bleed nitro-
gen to atmosphere.
7. Close all valves previously opened in the sys-
tem. Open suction and discharge shut-off valves.
Remove tags as per local lockout/tagout procedure.
8. Turn motor and oil pump disconnect switches to
the ON position.
9. The compressor unit can now be started, refer to
Start-Up procedure in Section 4.
Solenoid
Shut-off
Valve
Needle
Valve
Line to
Suction
Line
from Oil
Separator
Line from Needle
Valve to Suction
Line from Oil Separator
to Shut-off Valve
Figure 5-1. Suction By-Pass Valve Location (Equalizing Solenoid) (2 of 2)
