LUBE OIL SYSTEM The lube oil is circulated to the two main bearings of the gas turbine, generator bearings, various turbine accessories, flexible couplings and load equipments. A portion of oil is diverted and filtered for use by the various hydraulic control devices and functions as hydraulic control oil. Lube oil system consists of three numbers of oil pumps: Main oil mump ( +ve displacement, accessory gear drive ) Auxiliary lube oil pump ( AC, centrifugal ) Auxiliary lube oil pump ( AC, centrifugal ) MOP output pressure to the lube oil system is limited by a pressure relief valve (VR-1) to 4.5 Ksc. AOP, when AC power is available for turbine start-up and shut-down sequence, the system lube oil is supplied by the AC auxiliary lube oil pump (AOP) during the time that the speed of MOP is enough to develop sufficient pressure. At gas turbine start-up, this pump starts to run automatically. This pump continues to run until the gas turbine reaches approximately 95% speed signal (14HS), and at this point the pump will shut-down and the system pressure will be maintained by MOP. On gas turbine shut-down, the AC auxiliary lube oil pump starts with the closure of speed signal contact (14HS) when gas turbine sped drops to a value in between 75% and 90%. The pump continues to run throughout the shut-down sequence and cool-down period. AOP will start automatically when header pressure falls below a preset value. EOP, when AC power is not available, the DC emergency pump starts and provides back-up for the auxiliary lube oil pump as follows -> ( i )At turbine start-up, the DC emergency pump starts automatically. The pump will continue to run after 40% gas turbine speed (14HA) if the system pressure has not reached the setting of the pressure switch (63QN). ( ii ) During ratcheting sequence this pump will run every 3 minutes, in parallel with ratchet pump to save the batteries.
PARAMETER Pump type Pump capacity Discharge pressure Speed Drive Power rating
LUBE OIL PUMP DETAILS MOP AOP Gear Centrifugal 1741 LPM 1741 LPM 4.48 Ksc. 4.57 Ksc. 1415 RPM 2900 RPM Accessory gear AC motor Shaft-driven 37.5 KW
EOP Centrifugal 946 LPM 2.11 Ksc. 1750 RPM DC motor 7.5 KW
CONTROL OIL SYSTEM PURPOSE To control fuel gas stop/ speed ratio and control valve. To supply proper oil pressure to machine protection circuit of the gas turbine.
The control oil is supplied from the gas turbine’s lube oil system and hydraulic system. The oil supplied from the lube oil system is connected to the low pressure trip oil circuit through an orifice, and supplies oil to the gas turbine over-speed trip valve, the manual emergency trip valve and fuel oil stop valve. Loss of oil pressure, through operation of any one of these components, reduces trip oil circuit pressure to almost to zero, causing the piston of the fuel shut-off valve to drop shutting-off fuel flow to the gas turbine.
CONTROL PHILOSOPHY LUBE OIL PRESSURE CONTROL a) The diaphragm operated regulating valve (VPR-2) is installed up-stream of the lube oil cooler(s). The valve maintains the bearing header oil pressure at design pressure. The valve receives a pressure signal from header (bearing oil header) and when the header pressure exceeds the control valve setting, the valve opens and dumps the oil to the lube oil tank. b) The spring loaded, diaphragm operated valve (VPR-1) is installed in the lube oil tank. The valve provides the necessary pressure for hydraulic trip circuit. Trip oil circuit pressure is extracted from the MOP discharge between the pump and the pressure regulating valve (VPR-1). This valve throttles the MOP discharge as necessary, to assure that the hydraulic trip circuit is pressurized to the required value during the firing sequence. The valve is closed during start-up, and opens as the trip circuit reaches the design point. The valve is by-passed by an orificed passage to ensure that oil is never completely shut-off from the bearing feed header. During shut-down sequence also this orifice provides minimum flow of oil to assure that oil is never completely shut-off from bearing header. Trip oil from MOP VPR-1 VP to bearing hdr.
VR-1
Orifice diameter = 15.9 mm Bearing oil header
To lube oil cooler From EOP VPR-2 From MOP/AOP
LUBE OIL TEMPERATURE CONTROL This control system has one regulatory valve (VTR-1). This valve regulates cooling water flow through lube oil cooler for temperature control purpose. LUBE OIL TANK HEATING SYSTEM A maximum viscosity of 800 SSU is specified for variable operations of the control system for bearing lubrication. A temperature switch (26QN) prevents turbine start-up if the temperature of the lubricant is lower than the setting value. Immersion heaters (23QT-1,2) are provided to heat the lube oil. The temperature switches [26QN (set = 21oC) and 26QL (set = 13OC)] control the immersion heater operation. AOP will automatically start whenever heaters are ON to circulate the system lube oil.
LUBE OIL CIRCUIT DIAGRAM COUPLING OIL PG
63QL
F 63QA-2
F
TG
26QT
BEARING OIL HEADER
26Q
PG
F
F
MHOP
HYDRAULIC OIL
ACCESSORY GEAR BOX
TRIP OIL LO C
LO C
F
F
PG
MOP
63QA-1
PG
PG
M
M
M
A H OP
EO
A OP
P
S
S
S
TRIP OIL CIRCUIT DIAGRAM
20FG-1 63H G
PG
