JOHNSON CONTROLS
32
FORM 160.67-O2
ISSUE DATE: 10/9/2020
SECTION 2 - PRE-STARTUP AND SYSTEM OPERATING PROCEDURES
Automatic Start:
The BEGIN SLOW ROLL key
does not appear and the start sequence proceeds
to paragraph 7.
7. The speed controller setpoint is ramped up to 1000
RPM. This causes the output signal to the gover-
nor valve transducer to increase to open the gov-
ernor valve. Open the steam inlet slow roll bypass
valve to start the turbine slow rolling. The valve
should be opened only far enough to achieve 1000
RPM with the governor valve at least 25-35%
open. This will provide optimum speed control
with less hunting.
Chillers manufactured after December 2006
DO
NOT
require the manipulation of a slow roll by-
pass valve. The output signal to the valve control-
ler automatically modulates the ball valve posi-
tion to achieve and maintain the slow roll speed.
Automatic Start
: The output of the Governor
(Slow Roll) PID also controls the slow roll bypass
valve. As the speed setpoint is ramped up to 1000
RPM, both the governor valve and the slow roll
valve open to start the turbine slow rolling. As the
speed approaches set point, both valve outputs are
reduced to control the slow roll at 1000 RPM.
Chillers manufactured after December 2006
DO
NOT
use a separate slow roll bypass valve.
After rotation begins, if 1000 RPM is not achieved
in 100 seconds, the turbine will be tripped by the
under speed logic and the message TURBINE
UNDERSPEED is displayed. If the speed drops
below 900 RPM for more than 60 seconds, the
chiller will also shut down on under speed.
8.
When the panel senses that the speed has increased
above 500 RPM, the message "SLOW ROLL
-
ING" is displayed. If the chiller is not supplied
with a solenoid in the turbine steam ring drain
line, the manual valve in the steam ring drain line
should be closed at this time. The evaporator low-
pressure safety shutdown set point is increased to
30 PSIG. The compressor oil cooler liquid valve
is opened (only if the compressor oil temperature
increases above 150°F) to allow the compressor
oil temperature control valve to maintain the bear-
ing supply oil temperature at approximately 110-
120°F.
If the chiller is supplied with a check valve and
solenoid valve in the turbine steam ring drain line,
the solenoid valve remains energized (open) dur-
ing the initial startup. The check valve in the steam
ring drain line prevents air from being drawn into
the turbine when the turbine steam ring drops be-
low atmospheric pressure during the initial evacu-
ation and while the turbine is slow rolling. When
the inlet steam valves open to begin slow roll and
during the ramp up to minimum speed, the steam
ring will rise above atmospheric pressure and any
condensate will be blown out of the turbine.
9.
If the turbine is equipped with an auxiliary oil
pump, the turbine oil cooler liquid valve is opened
to allow the turbine oil temperature control valve
to maintain the bearing supply oil temperature at
approximately 110-120ºF. For turbines with Ring
Lubrication, the liquid valve is opened to allow
cooling liquid to flow through the bearing oil res
-
ervoir jackets. Adjust the valve in the cooling
liquid outlet line to maintain a minimum oil tem-
perature of 130°F in both bearing oil sumps.
Do Not Allow The Cooling Liquid To Cool
The Bearing Oil Sump Temperature To
Below 130°F (54°C), As This May Inter
-
fere With The Action Of The Oil Rings
Or Cause Atmospheric Moisture To Con-
dense In The Oil Reservoir.
10. A period of slow roll at 1000 RPM is required
before the turbine can be run continuously. After
slow roll, the turbine speed may be increased to
normal operating speed. The amount of time re-
quired to slow roll varies, depending on the inlet
steam temperature and the number of stages in the
turbine. The chiller control logic automatically
calculates the slow roll time required and displays
the time remaining via a countdown timer in the
status bar of the OptiView™ Control Center
screens.
If a chiller start is initiated within 15 minutes of
the last trip after a ramp-to-rated speed was initi-
ated, the calculated slow roll time is reduced to 5
minutes because the turbine rotor is still hot and
the shaft has not been stationary long enough to
bow.
11. During slow roll, when the turbine exhaust pres-
sure has decreased to the PSP5-Vacuum Pump
Shutdown setpoint (9 PSIA) shown on the PRES
-
SURE SETPOINTS SCREEN , the vacuum
pump is stopped. If the turbine exhaust pressure
increases to the PSP6- Ready To Run Turbine Ex
-
haust Pressure setpoint (12 PSIA) shown on the
PRESSURE SETPOINTS SCREEN, the vacuum
pump is restarted.
