6.2.2 Functional Description
6.2.2.1 Lubricant Reservoir and Piping
The oil reservoir is a 2600 gallon (9843 liter) tank which is integral with the module. The interior of the tank is coated with an oil resistant protective coating. The top of the tank is the base on which components such as the pumps, and heat exchangers are mounted. Under normal operating conditions oil is provided to the system by one of two main AC motor driven centrifugal pumps (PQ1-1 and PQ1-2). The selection of lead and lag pumps is made by the operator through the turbine control system prior to startup.
By alternating the lead/lag pump selection, the operating hours can be equalized. Each AC motor includes a motor space heater (23QA-1 and -2) to prevent condensation in the motor. All pumps have a check valve on the discharge line so that oil does not flow into the tank through a pump, which is not in service. Two pressure switches (63QA-1A and -1B) are mounted in the common header just downstream of the main pumps to ensure proper pump operation. If either of these senses low pressure, an alarm is sounded and the lag pump is automatically started.
If this occurs, the operator must manually shut off one pump and check that system pressure is stable. The oil is first pumped through one of the two parallel proper bearing header temperatures. The maximum allowable bearing header temperature under normal operating conditions is 160F (71.1̊C). The oil then flows through one of the two full flow parallel filters (LF3-1 and LF3-2). A three-way transfer valve controls selection of which set of heat exchanger/filter is in use. The lubricant oil filters have removable filter elements.
A differential pressure gauge provides visual indication of the dP over the filter. Pressure switches (63QQ-21, -22) provide a high differential pressure alarm signal across each filter. Filter elements should be replaced near or at the alarm set point as shown in Figure (6.4). Taps (OS), (OR-1) and (OLT-1), which are located downstream of the filters, supply lube oil to the generator bearing seals,hydraulic/lift oil system and trip oil system respectively. Pressure regulating valve (VPR2-1) then controls the oil pressure to the turbine and generator bearings and the turning gear.
The system is ventilated through a mist eliminator mounted on top of the lube oil reservoir. A slight negative pressure is maintained in the system by redundant motor driven fans (88QV-1A and 88QV-1B) pulling air through the mist eliminator. This negative pressure draws sealing air through the gas turbine bearing seals.
Each AC motor includes a motor space heater (23QV-2A and 23QV-2B) to prevent condensation in the motor. The motor driven fans have no DC backup motors and are not required to run in the emergency situation, when the DC pumps has taken over. The fans are set up to run in a lead/lag configuration and are designed to run one at a time.
The selection of lead and lag fans is made by the operator through the turbine control system prior to startup. The lag fan takes over whenever the lead fan has failed to run, has been overloaded or if there is insufficient vacuum in the lube oil reservoir. If the lag fan is started automatically by the control system due to insufficient tank vacuum level, the lead fan will be automatically shut off. Pressure switch (63QV-1) provides a low differential pressure alarm signal when there is insufficient vacuum in the lube oil reservoir. A regulating valve is downstream of each fan, and is adjusted to regulate tank vacuum level.
A level alarm device (float operated) is mounted on the top or side of the lube reservoir. The float mechanism operates two level switches (71QH-1 and 71QL-1). The switches are connected into the alarm circuit of the turbine control panel to initiate an alarm if the liquid level rises above, or fall below, the levels shown on the Schematic Piping Diagram. The oil level is visually indicated by a gauge on the side of the tank. An oil drain connection is located on the side of the accessory module to drain the reservoir.
6.2.2.1 Lubricant Reservoir and Piping
The oil reservoir is a 2600 gallon (9843 liter) tank which is integral with the module. The interior of the tank is coated with an oil resistant protective coating. The top of the tank is the base on which components such as the pumps, and heat exchangers are mounted. Under normal operating conditions oil is provided to the system by one of two main AC motor driven centrifugal pumps (PQ1-1 and PQ1-2). The selection of lead and lag pumps is made by the operator through the turbine control system prior to startup.
By alternating the lead/lag pump selection, the operating hours can be equalized. Each AC motor includes a motor space heater (23QA-1 and -2) to prevent condensation in the motor. All pumps have a check valve on the discharge line so that oil does not flow into the tank through a pump, which is not in service. Two pressure switches (63QA-1A and -1B) are mounted in the common header just downstream of the main pumps to ensure proper pump operation. If either of these senses low pressure, an alarm is sounded and the lag pump is automatically started.
If this occurs, the operator must manually shut off one pump and check that system pressure is stable. The oil is first pumped through one of the two parallel proper bearing header temperatures. The maximum allowable bearing header temperature under normal operating conditions is 160F (71.1̊C). The oil then flows through one of the two full flow parallel filters (LF3-1 and LF3-2). A three-way transfer valve controls selection of which set of heat exchanger/filter is in use. The lubricant oil filters have removable filter elements.
A differential pressure gauge provides visual indication of the dP over the filter. Pressure switches (63QQ-21, -22) provide a high differential pressure alarm signal across each filter. Filter elements should be replaced near or at the alarm set point as shown in Figure (6.4). Taps (OS), (OR-1) and (OLT-1), which are located downstream of the filters, supply lube oil to the generator bearing seals,hydraulic/lift oil system and trip oil system respectively. Pressure regulating valve (VPR2-1) then controls the oil pressure to the turbine and generator bearings and the turning gear.
The system is ventilated through a mist eliminator mounted on top of the lube oil reservoir. A slight negative pressure is maintained in the system by redundant motor driven fans (88QV-1A and 88QV-1B) pulling air through the mist eliminator. This negative pressure draws sealing air through the gas turbine bearing seals.
Each AC motor includes a motor space heater (23QV-2A and 23QV-2B) to prevent condensation in the motor. The motor driven fans have no DC backup motors and are not required to run in the emergency situation, when the DC pumps has taken over. The fans are set up to run in a lead/lag configuration and are designed to run one at a time.
The selection of lead and lag fans is made by the operator through the turbine control system prior to startup. The lag fan takes over whenever the lead fan has failed to run, has been overloaded or if there is insufficient vacuum in the lube oil reservoir. If the lag fan is started automatically by the control system due to insufficient tank vacuum level, the lead fan will be automatically shut off. Pressure switch (63QV-1) provides a low differential pressure alarm signal when there is insufficient vacuum in the lube oil reservoir. A regulating valve is downstream of each fan, and is adjusted to regulate tank vacuum level.
A level alarm device (float operated) is mounted on the top or side of the lube reservoir. The float mechanism operates two level switches (71QH-1 and 71QL-1). The switches are connected into the alarm circuit of the turbine control panel to initiate an alarm if the liquid level rises above, or fall below, the levels shown on the Schematic Piping Diagram. The oil level is visually indicated by a gauge on the side of the tank. An oil drain connection is located on the side of the accessory module to drain the reservoir.
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