UGGs Outlet On Sale, The Price Is The Lowest One In Life



SYSTEM DESCRIPTION

|Seal Oil and Hydrogen System |

|HOPKINS REPOWERING PROJECT |

|UNIT HP2A |

TABLE OF CONTENTS

Section Page

1.0 Introduction 2

1.1 Purpose and Scope 2

1.2 System Overview 2

1.2.1 Primary System Flowpaths 2

1.2.2 Secondary System Flowpaths/Components 6

2.0 MAJOR COMPONENTS AND SUBSYSTEMS 7

2.1 Seal Oil System 7

2.1.1 Function 7

2.1.2 Detailed Description 7

2.1.3 Technical Design Data 13

2.1.4 Operation, Control and Safety 14

2.2 Generator Gas System 18

2.2.1 Function 18

2.2.2 Detailed Description 18

2.2.3 Technical Design Data 24

2.2.4 Operation, Control and Safety 24

3.0 List of Instrumentation and Controls 27

4.0 List of Alarms and Setpoints 28

5.0 List of System Constraints 29

6.0 References 30

6.1 P&ID 30

6.2 Electrical One Line Diagrams 30

6.3 Control Diagrams 30

6.4 Instrument Loop Diagrams 31

6.5 Instruction Manuals 31

6.6 Miscellaneous 31

TABLE OF FIGURES

Figure Page

Figure 1.1 Generator Seal Oil System Flow Diagram 3

Figure 1.2 Generator Seal Oil Schematic 4

Figure 1.3 Generator Gas Schematic 6

Figure 2.1 Gland Seal 9

Figure 2.2 Seal Oil Drain Regulator 13

Figure 2.3 Hydrogen Tanks 20

Figure 2.4 Carbon Dioxide Cylinders 22

Figure 2.5 Gas Dryer Assembly 24

1. Introduction

1. PURPOSE AND SCOPE

The purpose of this system description is to provide you with an overview of the Seal Oil and Hydrogen System, describe the system's major components, and explain their operation and control. The Seal Oil and Hydrogen System supports the hydrogen cooled electric generators. The hydrogen cools the generator and the seal oil prevents the hydrogen from mixing with the atmosphere outside of the generator. The system contains the following subsystems and major components:

a. Seal Oil System

b. Generator Gas System

2. System Overview

1. Primary System Flowpaths

The Seal Oil and Hydrogen System is comprised of the following major subsystems

➢ Seal Oil System

➢ Generator Gas System

Seal Oil System

The Seal Oil System, as illustrated in Figures 1.1 and 1.2, supplies seal oil to the generator seals to prevent the escape of hydrogen gas along the shaft. The Generator Seal Oil System consists of the air side seal oil and the hydrogen side seal oil subsystems. Both systems supply oil to the two generator seals. Makeup oil to the Generator Seal Oil System is supplied by the Turbine Lube Oil System. (The Turbine Lube Oil System is discussed in detail in Steam Turbine System Description, 2-ST-SD.)

[pic]

Figure 1.1 Generator Seal Oil System Flow Diagram

[pic]

Figure 1.2 Generator Seal Oil Schematic

The major flowpath for the air side seal oil subsystem begins and ends in the generator bearing oil drain loop seal tank. The loop seal tank is equipped with a vapor extractor which removes air and hydrogen from the oil. The air side seal oil pump takes suction from the loop seal tank or the hydrogen side drain regulator drain valve and discharges to the air side seal oil cooler. The air side seal oil pressure is maintained at 12 psig above the generator hydrogen pressure by a differential regulating valve on the air side seal oil pump discharge. This valve diverts excess seal oil back to the pump suction thereby maintaining the differential pressure at the required setpoint (12 psig). From the cooler, the air side seal oil flows through a filter and then to the air side generator seals or to the hydrogen side drain regulator fill valve. The generator air side seal oil drains are connected to the generator bearing oil drains which return the oil back to the loop seal tank. From the loop seal tank, the oil is returned to the main turbine lube oil reservoir and supply suction to the air side seal oil pump.

The major flowpath for the hydrogen side seal oil system begins and ends in the hydrogen side drain regulator. The hydrogen side seal oil pump takes suction from the drain regulator and discharges to the hydrogen side seal oil cooler. Oil from the cooler flows through a filter, and then flows to the generator hydrogen side seals through pressure equalizing valves. The pressure equalizing valves maintain the hydrogen side seal oil pressure at the same pressure as the air side seal oil pressure. Hydrogen side seal oil drain to the defoaming tanks, one for each seal, and is piped back to the drain regulator. The defoaming tanks allow the hydrogen in the seal oil to vent back into the generator.

Upon failure of the air side seal oil subsystem to meet the supply requirements of the generator seals, backup supplies are available from the following:

➢ Main turbine lube oil pumps

• Main oil pump

• Turbine auxiliary oil pump

• Turning gear oil pump (will only maintain 2 psig hydrogen pressure)

➢ Air side seal oil backup pump

When oil is supplied from the Turbine Lube Oil System via the main lube oil pump, the oil flows through a pressure reducing valve, which reduces the oil pressure to 125 psig. The oil then flows through a check valve and a second pressure control valve. The pressure control valve is equipped with manually operated inlet, outlet and bypass valves so the pressure control valve may be isolated or bypassed as necessary.

The air side seal oil backup pump flowpath is similar to the primary air side seal oil pump. The pump takes suction from the loop seal tank and discharges to the air side seal oil pump discharge header.

Generator Gas System

The Generator Gas System, as illustrated in Figure 1.3, supplies, maintains, and removes pressurized hydrogen (H2) and carbon dioxide (CO2) from the generator. Hydrogen gas is used as the cooling medium in the generator. Carbon dioxide is used during filling and removal of hydrogen from the generator to prevent air (oxygen) and hydrogen gas from mixing and forming an explosive mixture.

[pic]

Figure 1.3 Generator Gas Schematic

Gaseous hydrogen and carbon dioxide are supplied by their respective supply manifolds when a gas is being added. Hydrogen is supplied to the hydrogen gas header from the hydrogen bulk storage location. The hydrogen flows through an isolation valve, a pressure regulator and two additional isolation valves to the hydrogen header. A removable link is installed in the hydrogen manifold only when hydrogen is being added to the generator. This ensures that hydrogen and air cannot be mixed by valve malfunction. The hydrogen distribution tube, located internal to the generator housing, is a perforated pipe that evenly distributes the hydrogen gas.

Carbon dioxide from pressurized cylinders enters the carbon dioxide manifold. The gaseous carbon dioxide passes through two isolation valves before entering the carbon dioxide header located internal to the generator housing. The carbon dioxide header is a perforated pipe that evenly distributes the carbon dioxide gas.

A gas dryer is used to remove moisture from the hydrogen gas in the generator. The gas dryer receives a portion of the hydrogen discharged from the generator blower. The gas circulates through the gas dryer and is returned to the generator housing.

Hydrogen is purged from the generator using carbon dioxide gas. The carbon dioxide is purged from the generator using air. This ensures that the hydrogen and air do not mix to form an explosive mixture. Likewise, to refill the generator with hydrogen after it has been opened for maintenance, the air is removed from the generator with carbon dioxide then the hydrogen is added.

Of the three gases, hydrogen is the lightest, and carbon dioxide is the heaviest gas. When the air in the generator is replaced with carbon dioxide, the carbon dioxide is admitted to the bottom of the generator through the carbon dioxide distribution tube, while the air is vented through the hydrogen distribution tube at the top of the generator. When filling the generator with hydrogen, the hydrogen is admitted through the upper perforated distribution tube, and the carbon dioxide is vented through the lower perforated distribution tube. By using the distribution tubes in this manner, turbulence and mixing of the different gases are minimized, thus ensuring a safe and efficient operation.

Hydrogen is circulated through the generator by a blower mounted on the turbine end of the generator rotor. The blower discharges to the hydrogen coolers to minimize the gas temperature rise caused by the generating field. Cold gas exiting the coolers is routed by means of baffles to the opposite end of the generator where the hydrogen is introduced to the open ends of the vent tubes in the stator coils. The cooling gas passes from one end of the generator to the other through these vent tubes, being discharged at the turbine end where it again supplies suction to the blower. A portion of the gas exiting the coolers does not make the circuit described above, but instead is carried through orifice-type openings into the space immediately behind the stator core. The hydrogen then passes through ventilating slots in the stator core to again supply suction to the blower.

A portion of the cold gas exiting the coolers is also directed by means of baffles and ventilating passages through the rotor. This gas enters the rotor at each end, flowing through the ventilation passages provided in the rotor winding itself, and flows to the gap at the center of the rotor to provide suction to the blower. On two pole rotors, the end turns have a ventilation circuit separate from that of the straight portion of the winding. A special pattern of holes is arranged radially in the end turns and cold gas from the coolers passes directly into these holes at both ends of the rotor, flowing through hollow passages in these end turns similar to the passages in the straight portion of the rotor. The gas is then discharged into a special chamber beneath the end turn winding near the center of the pole. From there it is returned to the blower suction.

2. Secondary System Flowpaths/Components

The Seal Oil and Hydrogen System also contains or interfaces with the following secondary systems and/or components:

a. Condensate Cooling Water - The condensate cooling water system supplies cooling water to the generator hydrogen and seal oil coolers.

b. Electrical Distribution System - The electrical distribution system is used to supply power and energize all of the electrical components. The MCCs located throughout the plant feed the system components and provide the required protection and starter functions. The electric generator supplies the root source of electrical power to the system.

c. Instrument Air System - Instrument air supplied between 3-27 psig is used as the medium to operate the system controls, including local controllers, control valves and instrumentation.

2. MAJOR COMPONENTS AND SUBSYSTEMS

1. SEAL OIL SYSTEM

1. Function

The primary function of the Seal Oil System is to prevent hydrogen from leaking from the generator. Secondly, the system reduces hydrogen contamination by its exposure to air and water vapor, which is dissolved in the oil circulated in the system. Finally, the generator seal oil lubricates the shaft seals thus preventing damage to the babbitt metal.

2. Detailed Description

Nearly all generators for large steam turbines use hydrogen for cooling. Hydrogen is used because it has a better heat removal capacity than air. Hydrogen also has significant disadvantages as compared to air from the perspective of safety and convenience. Mixtures of from 4.1% to 74.2% of hydrogen are explosive. Clearly, it is important to make sure that the hydrogen does not escape from the generator casings and that the purity of the hydrogen inside the generator is maintained at an acceptably high level. The Generator Seal Oil System is designed to accomplish those functions. Seal oil at a pressure higher than the generator gas pressure is admitted to hydrogen seal rings with a very close clearance to the shaft. Since the seal oil pressure is higher than the gas pressure, the seal oil leaks into the generator rather than the gas leaking out.

The Generator Seal Oil System consists of the following components:

➢ Gland Seals

➢ Air Side Seal Oil Pump

➢ Turbine Lube Oil Backup Control Valves

➢ Air Side Seal Oil Backup Pump

➢ Hydrogen Side Seal Oil Pump

➢ Seal Oil Coolers

➢ Hydrogen Side Drain Regulator

➢ Generator Bearing Oil Drain (Loop Seal) Tank

➢ Generator Bearing Oil Drain Line Vapor Extractor

The flow of the Generator Seal Oil System is illustrated on Figure 1.2.

Gland Seals

The function of the gland seals is to seal the hydrogen in the generator and prevent hydrogen from escaping into the turbine hall. The gland seals prevent hydrogen gas in the generator from leaking along the generator shaft to the atmosphere. The generator has two seal assemblies, one at each end, where the shaft penetrates the generator casing. Each gland seal, as illustrated in Figure 2.1, consists of an air side seal and a hydrogen side seal. The hydrogen side seal is located between the generator and the air side seal. Seal oil, arranged in separate air side and hydrogen side loops, is used to seal, lubricate and cool the seals as discussed below.

[pic]

Figure 2.1 Gland Seal

Each gland seal has two annular grooves. The groove closest to the generator is the hydrogen side seal oil groove, referred to as the inner groove. The groove on the generator main bearing side is the air side seal oil groove, referred to as the outer groove. The two grooves are separated by a machined seal to reduce the possibility of seal oil leakage between the inner and outer grooves. The hydrogen seal oil grooves drain to the hydrogen defoaming tanks. The air side seal oil groove drains mix with the generator bearing lube oil drains and flow to the loop seal tank.

The hydrogen side seal oil is pumped to the seal inner face (groove) and flows inward, against the outward force produced by the hydrogen gas in the generator. The air side oil flows to the seal outer face (groove) and flows outward, against the inward force produced by the atmosphere.

The hydrogen side seal oil and air side seal oil pressures are maintained at the same pressure to avoid mixing of the two oils. The mixing of the two oils could cause hydrogen and air to mix which could lead to a potentially dangerous situation.

Air Side Seal Oil Pump

The function of the air side seal oil pump is to supply pressurized seal oil to the gland seal outer faces (air side seals or grooves). The air side seal oil pump takes suction from the loop seal tank through a manual inlet valve and discharges to the air side seal oil coolers through two check valves and a discharge block valve. Air side seal oil flows into the space between the impeller gear teeth as these cavities pass the suction opening. The oil is then forced along the pump casing by the impeller to the discharge opening where it is forced out through the discharge flange.

The air side seal oil pump discharge pressure is maintained by that air side seal oil differential pressure regulator. The differential pressure regulator receives oil from a branch line located between the two check valves. The oil flows through the differential pressure regulator back to the air side seal oil pump suction. The differential pressure regulator modulates as necessary to maintain the air side seal oil pressure 12 psi above the hydrogen pressure in the generator casing. An air side seal oil pressure relief valve is located in parallel with the differential pressure regulator. The relief valve is set at 100 psig and relieves to the air side seal oil pump suction.

The air side seal oil pump is a double helical gear positive displacement type pump manufactured by Worthington. The internals of the pump include two helical gears (impellers) arranged in a rotary pump casing. The clearance between the two impellers is extremely small. One impeller is driven by the pump motor and drives the other impeller (called the idler). The impellers are machined with helical gears to assure that as the pump drive rotates and the impellers revolve, two gear teeth are always in contact with each other. The impeller action results in a steady pump discharge without pulsations. The pump is equipped with self-lubricating, internal shaft bearings.

The pump is driven by a 15 horsepower, 1,170 rpm, 480 VAC drive motor manufactured by Westinghouse. The motor drives the pump through a flexible coupling.

Turbine Lube Oil Backup Control Valves

Backup seal oil is supplied to the Generator Seal Oil System from the Turbine Lube Oil System in the event of an air side seal oil pump malfunction. There is one high pressure backup supply and one low pressure backup supply. High pressure seal oil is supplied from the Turbine Lube Oil System pumps through a pressure reducing valve, a check valve, and a pressure regulator. The pressure regulator is equipped with manually operated inlet, outlet, and bypass valves so the pressure regulator may be isolated and/or bypassed as necessary. Additionally, a separate bearing oil supply header containing a check valve supplies oil to the pressure regulator. This line supplies oil to the Generator Seal Oil System when the Generator Seal Oil System pumps are shut down. This line is supplied by the turbine gear oil pump and the emergency oil pump. These pumps can maintain a maximum hydrogen pressure of 2 psig in the generator.

The pressure reducing valve reduces the turbine lube oil pressure to 125 psig. A pressure indicator is located downstream from the pressure reducing valve so the operation of the valve may be monitored. Additionally, a pressure relief valve is located downstream from the pressure reducing valve. The relief valve is set to open at 150 psig and relieves to the bearing oil header. The downstream pressure from the pressure reducing valve is also monitored by a pressure switch which annunciates a SEAL OIL TURBINE BACKUP PRESSURE LOW alarm if the downstream pressure from the pressure reducing valve decreases to 70 psig.

The pressure regulating valve opens when the differential pressure at the seals between the hydrogen pressure and the air side seal oil pressure decreases to 8 psid.

Air Side Seal Oil Backup Pump

The function of the air side seal oil backup pump is to supply seal oil to the generator air side seals when the air side seal oil pump and backup supply from the Turbine Lube Oil System fail to maintain adequate seal oil pressure. The air side seal oil backup pump starts when the differential pressure between the generator hydrogen pressure and the air side seal oil pressure is less than 5 psi as detected by a pressure switch. The pump also starts on a loss of AC power. When the air side seal oil backup pump is running, hydrogen pressure should be reduced to 2 psig if the turbine auxiliary oil pump is not available.

The air side seal oil backup pump is arranged in parallel with the air side seal oil pump. It takes suction from the loop seal tank through a manual inlet valve and discharges to the air side seal oil cooler through two check valves and a manually-operated discharge valve.

The air side seal oil backup pump is a double helical geared positive displacement type pump manufactured by Worthington of the same design as the air side seal oil pump discussed earlier. The pump is driven by a 10 horsepower, 1,750 rpm, 125 VDC drive motor manufactured by Westinghouse. The pump is driven by the motor through a flexible coupling.

Hydrogen Side Seal Oil Pump

The function of the hydrogen side seal oil pump is to supply seal oil to the generator seal inner faces (hydrogen side seals or grooves). The hydrogen side seal oil pump takes suction from the hydrogen side drain regulator through a manually operated inlet valve and discharges to the seal oil cooler through a manually operated valve.

A pressure relief valve on the hydrogen side seal oil pump discharge header, opens at 100 psig to route seal oil back to the pump suction. A manual recirculation valve is also located in the pump discharge header. This valve is locked in a throttled position to allow for controlled recirculation of the hydrogen seal oil pump discharge.

The hydrogen side seal oil pump is a double helical geared positive displacement type pump manufactured by Worthington of the same design as the air side seal oil pump. The pump is driven by a 3 horsepower, 1,170 rpm, 480 VAC motor manufactured by Westinghouse. The pump is driven by the motor through a flexible coupling.

Seal Oil Coolers

The function of the seal oil coolers is to remove heat from the generator seal oil. The seal oil temperature increases due to friction in the generator seals, the seal oil pumps and the generator bearings. In addition, some of the heat produced within the generator is transferred to the seal oil.

The seal oil coolers are floating head, two tube pass, one shell pass heat exchangers. Cooling water supplied by the Condensate Cooling Water System flows through the tubes while the seal oil flows through the shell. There are two coolers, one for the air side seal oil and one for the hydrogen side seal oil.

The air side seal oil cooler receives seal oil from the air side seal oil pump or air side seal oil backup pump discharge through a manually operated inlet valve. The seal oil flows from the cooler through a manually operated outlet valve, a filter, and to the generator seals. Cooling water enters the end of the cooler corresponding to the seal oil outlet through a manually operated inlet valve. The cooling water flows through one half of the tubes to the other end of the cooler. At this end, the flow is reversed through the other half of the tubes so the water makes two passes and exits the cooler at the same end it entered. The cooling water exits through a manually operated outlet valve. The floating head is used to minimize the problems associated with differential metal expansion in the cooler as the metal temperature changes. The oil temperature is controlled by manually regulating the cooling water flow through the tubes.

Like the air side seal oil cooler, the hydrogen side seal oil cooler is vertically mounted. The hydrogen side seal oil cooler receives oil from the hydrogen side seal oil pump discharge through a manually operated inlet valve. The oil flows from the cooler through a manually operated outlet valve and a filter. The oil then flows to the hydrogen side seal oil supply headers each containing a pressure equalizing valve and a manually operated isolation valve. The cooling water flowpath through the hydrogen side seal oil cooler is identical to that of the air side seal oil cooler.

Hydrogen Side Drain Regulator

The function of the drain regulator, as illustrated in Figure 2.2, is to act as a suction reservoir, providing an adequate supply of seal oil to the hydrogen side seal oil pump. The drain regulator also allows the hydrogen entrained in the hydrogen side seal oil to escape back to the generator. The seal oil flows to the hydrogen side drain regulator from the defoaming tanks which receive the drain oil from the seals. Seal oil collects in the drain regulator. The residence time in the defoaming tanks gives the hydrogen entrained in the oil time to be released and returned to the generator.

[pic]

Figure 2.2 Seal Oil Drain Regulator

The drain regulator also maintains the proper amount of oil in the hydrogen side seal oil system. It receives makeup oil from the air side seal oil pump discharge header through a feed valve, while excess oil is piped from the drain regulator through a drain valve back to the air side seal oil pump suction header. Both the feed valve and drain valve are float-operated. During ideal operating conditions, the feed valve remains closed.

Generator Bearing Oil Drain (Loop Seal) Tank

The generator bearing oil drain (loop seal) tank has three primary functions:

➢ To serve as the Generator Seal Oil System reservoir (makeup and overflow).

➢ To remove any hydrogen which may be entrained in the air side seal oil.

➢ To provide a liquid loop seal between the Generator Seal Oil and Turbine Lube Oil Systems. (The Turbine Lube Oil System is discussed in detail in the Steam Turbine System Description, 2-ST-SD.)

The loop seal tank provides an interface between the Turbine Lube Oil System and the Generator Seal Oil System. Makeup and initial filling of the Generator Seal Oil System is supplied from the Turbine Lube Oil System through the loop seal tank.

The loop seal tank internal structure is designed to pass the oil draining from the generator bearings and air side seals through a "U" shaped path. This, along with the physical location of the tank, provides an effective seal between the generator oil and the main turbine lube oil tank. If the drain oil flow is interrupted and the drain line empties of oil, a sufficient quantity of oil remains in the loop seal to prevent the possibility of hydrogen flow to the main turbine lube oil reservoir.

Generator Bearing Oil Drain Vapor Extractor

The generator bearing oil drains and air side seal oil drains are in close proximity to the hydrogen gas in the generator and absorb some of the gas. In addition, excess hydrogen side seal oil is diverted from the hydrogen side drain regulator to the air side seal oil system. Therefore, the oil returning to the loop seal tank contains small amounts of entrained hydrogen. The loop seal tank allows this hydrogen to escape from the seal oil and be safely discharged. The generator bearing oil drain vapor extractor is started to remove these vapors from the tank and to prevent a dangerous accumulation of air and hydrogen mixture.

The vapor extractor is a single stage, centrifugal blower with an adequate capacity to remove unwanted gases from the loop seal tank. The vapor extractor is equipped with adjustable dampers which are normally adjusted to maintain one to three inches of vacuum in the loop seal tank.

The vapor extractor is driven by a 2 horsepower, 3,460 rpm, 480 VAC drive motor.

3. Technical Design Data

|Generator Air Side Seal Oil Pump |

|Manufacturer |Worthington |

|Type |Double Helical |

|Model |2GRM |

|Motor Manufacturer |Westinghouse |

|Horsepower |15 HP |

|Speed |1,170 rpm |

|Electrical Supply |480 VAC/3 phase/60 Hz |

|Service Factor |1.15 |

|Generator Air Side Seal Oil Backup Pump |

|Manufacturer |Worthington |

|Type |Double Helical |

|Model |2GRM |

|Motor Manufacturer |Westinghouse |

|Horsepower |10 HP |

|Speed |1,750 rpm |

|Electrical Supply |120 VDC |

|Service Factor |1.15 |

|Generator Hydrogen Side Seal Oil Pump |

|Manufacturer |Worthington |

|Type |Double Helical |

|Model |2GRM |

|Motor Manufacturer |Westinghouse |

|Horsepower |3 HP |

|Speed |11,270 rpm |

|Electrical Supply |480 VAC/3 phase/60 Hz |

|Service Factor |1.15 |

|Generator Seal Oil Coolers |

|Manufacturer |Westinghouse |

|Size |Air-Side 430 square feet |

| |Hydrogen-Side 86 square feet |

|Shell Pressure |125 psi |

|Shell Temperature |200°F |

|Instruction Book |1250-C917 |

|Generator Seal Oil Vapor Extractor |

|Manufacturer |Westinghouse |

|Type |Turbo-Blower |

|Size |2512-2 |

|Style |PHY-7044 |

|Motor Manufacturer |Westinghouse |

|Horsepower |2 |

|Speed |3,460 rpm |

|Electrical Supply |480 VAC/3 phase/60 Hz |

|Service Factor |1.0 |

4. Operation, Control and Safety

Integrated Operation

When operating any of the pumps in the Generator Seal Oil System, the discharge valves of the pumps must be opened prior to starting any of the pumps. Since the pumps are positive displacement pumps they have a fixed capacity. If the discharge valves are not properly aligned, the pump and discharge piping can be damaged.

During unit startup, the Generator Seal Oil System is placed in service prior to filling the generator with hydrogen. The Generator Seal Oil System is filled if necessary from the Turbine Lube Oil System. While the unit is being filled, the generator bearing oil drain line vapor extractor should be started. The vapor extractor should operate continuously while the Generator Seal Oil System and/or Turbine Lube Oil System are in service.

Additional starting checks should include the following: (1) defoaming tanks and hydrogen side drain regulator levels are normal, or slightly higher than normal with no pumps running, (2) air side seal oil pressure should be about 2 to 5 psig at the seals, (3) cooling water lined up to the seal oil coolers.

The air side seal oil pump and hydrogen side seal oil pump are then started. It is not unusual for the hydrogen side drain regulator tank to be above the high level alarm point until the hydrogen pressure is increased in the generator. When the system pressures and flows stabilize, the air side seal oil backup pump is placed in the automatic mode. This allows the air side seal oil backup pump to automatically start if the air side seal oil pump trips and the backup supply from the Turbine Lube Oil System is insufficient. If the differential pressure between the air side seal oil and the hydrogen decreases to less than 5 psig, pressure switch PS-8 closes which activates the SEAL OIL PRESSURE - LOW alarm and starts the air side seal oil backup pump.

During normal operation of the Generator Seal Oil System, both the air side and hydrogen side seal oil are supplied to the generator seals at the same pressure. The piston-operated pressure equalizing valves, located on the hydrogen side seal oil supply lines between the cooler outlet strainer and the generator seals, maintain the hydrogen side seal oil pressure equal to the associated air side seal oil pressure. This ensures that the hydrogen side seal oil and air side seal oil flows in the correct directions in the seals, minimizing mixing and keeping most of the hydrogen laden seal oil in the hydrogen seal oil side of the system where it can be safely removed and returned to the generator.

If difficulty is experienced in maintaining the hydrogen purity at 95% or greater during normal operation, one of the following could be occurring:

➢ Incorrect setting of the pressure equalizing valves

➢ Malfunctioning of the hydrogen side drain regulator

The pressure equalizing valves (210 and 217) should maintain the hydrogen side seal oil pressure with ±2 inches of water of the air side seal oil pressure. If one or both of these valves are not operating correctly, air may be introduced into the generator through the air side seal oil.

Float valves maintain the oil level in the hydrogen side drain regulator within certain limits. However, if the air side valve does not seal off tight when the oil level rises, air side seal oil is forced into the tank. The level is maintained since the other valve opens when the oil level is too high and allows the extra oil to be forced into the loop seal.

If the differential pressure between the generator hydrogen pressure and the air side seal oil pressure decreases to 8 psi, the backup turbine oil pressure regulator opens to supply oil to the air side seal oil circuit. If the differential pressure continues to decrease to 5 psi, pressure switch PS-8 annunciates a SEAL OIL PRESSURE-LOW alarm and starts the air side seal oil backup pump. The next available source of emergency oil after the air side seal oil backup pump is the turning gear oil pump via the turbine bearing oil supply header. This supply can only maintain a hydrogen pressure of 2 psig which could require a significant load reduction.

The Generator Seal Oil System must remain in service until the generator has been purged with carbon dioxide and air and is filled with 100% air at atmospheric pressure. The Generator Seal Oil System may then be isolated from the Turbine Lube Oil System by closing the manual isolation valve. The air side seal oil backup pump, air side seal oil pump and hydrogen side seal oil pump are then stopped. Typically, the generator drain line vapor extractor remains in service until the turbine lube oil system is shut down.

Gland Seals

There are no controls associated with the gland seals. However, the air side seal oil pressure at the shaft seal oil pressure may be monitored at each shaft seal using local pressure indicators. A differential pressure indicator is provided for each shaft seal to monitor the differential pressure between the air side seal oil pressure and the hydrogen side seal oil pressure. A governor seal oil pressure indicator is located on the bench board in the control room.

Air Side Seal Oil Pump

The air side seal oil pump is energized by 480 VAC feeder breaker located on MCC 2-1. The breaker includes an ON/OFF switch, a red RUN indicating light and a RESET pushbutton.

The air side seal oil pump is controlled by the local control station. The local control station is equipped with two self-explanatory pushbuttons: START and STOP. The pump is normally running during generator operation. The control station is also equipped with two indicating lights to alert the operator to the status of the pump. There is a GREEN Not Pump Running light and a RED Pump Running light.

The air side seal oil pressure is maintained at 12 psi above the hydrogen pressure in the generator by a differential pressure regulating valve. If the discharge pressure is too high, the valve throttles open and routes some of the discharged air side seal oil back to the suction line to effectively reduce the discharge pressure.

The discharge pressure of the pump can be monitored on a locally mounted pressure indicator. Local pressure gauges on the seal housings provide the air side seal oil pressure at the exciter and turbine ends of the generator. When the discharge pressure drops to less than 5 psi above the suction pressure, a differential pressure switch activates the AIR SIDE SEAL OIL PUMP OFF alarm.

Turbine Lube Oil Backup

There are no controls associated with the turbine oil pressure reducing. The valve modulates automatically to maintain an outlet pressure of 125 psig. The valve is equipped with a manual override so the valve position may be adjusted by an operator if necessary. A pressure gauge is located downstream from the pressure reducing valve so the operation of the valve may be monitored locally. Additionally, pressure switch PS-10 is also located downstream from the pressure reducing valve and annunciates a TURBINE OIL BACKUP PRESSURE-LOW alarm if the pressure decreases to 75 psig.

There are no controls associated with the turbine oil backup pressure regulator. The pressure regulator automatically opens when the differential pressure between the hydrogen pressure in the generator and the air side seal oil pressure decreases to 8 psi. The valve closes when the differential pressure is restored to normal. The pressure regulator is equipped with a manual override so the valve may be adjusted by an operator.

Air Side Seal Oil Backup Pump

The air side seal oil backup pump is energized by a breaker located on the DC power panel, DCB. The pump also includes a local un-fused disconnect switch to electrically isolate the motor.

The air side seal oil backup pump is controlled by the local control station. The local control station is equipped with two pushbuttons: START and STOP. The pump is normally not running during generator operation. The control station is also equipped with two indicating lights to alert the operator to the status of the pump. There is a GREEN pump not running light and a RED pump running light.

The air side seal oil backup pump is also equipped with an automatic start function. If during normal unit operation (or during a unit shutdown), the air side seal oil pressure decreases to less than 5 psi above the hydrogen pressure, pressure switch PS-8 (PDSL-626) actuates a SEAL OIL PRESSURE-LOW alarm and starts the air side seal oil backup pump. The air side seal oil backup pump continues to run and must be manually shut down.

The air side seal oil backup pump discharge pressure is controlled to maintain the air side seal oil pressure (at the seals) above the hydrogen pressure by the differential pressure regulating valve, which is the same valve that controls the air side seal oil pump discharge pressure. If the pump discharge pressure is greater than 12 psi above hydrogen pressure, the valve throttles open and routes excess pump discharge oil back to the suction line to reduce discharge pressure.

Hydrogen Side Seal Oil Pump

The hydrogen side seal oil pump is energized by 480 VAC feeder breaker located on MCC 2-2. The breaker includes an ON/OFF switch, a red RUN indicating light and a RESET pushbutton.

The hydrogen side seal oil pump is controlled by the local control station. The local control station is equipped with two pushbuttons: START and STOP. The pump is normally running during generator operation. The control station is also equipped with two indicating lights to alert the operator to the status of the pump. There is a GREEN not running light and a RED pump running light.

The differential pressure across the hydrogen side seal oil pump is monitored by a differential pressure switch (PS-12). If the differential pressure drops to less than 5 psig above the pump suction pressure, a HYDROGEN SIDE SEAL OIL PUMP OFF alarm is annunciated.

Hydrogen side seal oil pressure (measured on the filter outlet downstream from the hydrogen side seal oil coolers) may be monitored by a local pressure gauge. Hydrogen side seal oil pressure at the generator end seal and turbine end seal is controlled by two valves. If the hydrogen side seal oil pump trips, the generator may still be operated with hydrogen cooling. Under this condition, seal oil from the air side feed groove will flow in both directions along the shaft, providing the necessary lubrication and preventing the hydrogen from escaping the generator. It is necessary, however, to purge a small amount of gas periodically and add fresh hydrogen to maintain the hydrogen purity well above the upper limit of the explosive range of hydrogen-air mixture. It should be noted that some of the hydrogen is lost due to absorption into the seal oil. It should be noted that the opposite configuration with only the hydrogen side seal oil pump running does not work without a backup source of air side seal oil.

Seal Oil Coolers

There are no controls associated with the seal oil coolers. The temperature of the air and hydrogen side seal oil is manually controlled by throttling the condensate cooling water outlet valves on the respective coolers. The oil cooler outlet temperatures may be monitored by local temperature indicators in the oil outlet headers from the coolers. Normally the air and hydrogen side oil temperature is maintained at 100°F.

Control of the seal oil temperature is important in determining not only seal oil flow (due to temperature's effect on viscosity), but also the vibration of the generator shaft. In determining the optimum temperature setting for seal oil to the seals, the temperature should be set to produce the lowest generator shaft vibration at the lowest corresponding oil supply temperature as per Westinghouse.

Hydrogen Side Drain Regulator

The hydrogen side drain regulator seal oil level is automatically controlled by the two float valves installed in the vessel. If the drain regulator oil level drops too low, the feed valve opens. Air side seal oil flows into the drain regulator from the air side seal oil pump discharge header. If the drain regulator oil level becomes too high, the drain valve opens and excess oil flows to the air side seal oil pump suction header.

Hand jacks are provided to manually control the automatic float valves in the event of a valve malfunction. The oil level in the hydrogen side regulator may be monitored with the local oil level gauge. If the oil level decreases to the low level as detected by the hydrogen side drain regulator level switch (LS-9), a HYDROGEN SIDE LEVEL LOW alarm is annunciated.

Generator Bearing Oil Drain Tank

There are no controls associated with the generator bearing oil drain tank. The level is automatically maintained based on the physical location of the inlet and outlet headers.

Generator Seal Oil Vapor Extractor

The generator hydrogen seal oil vapor extractor motor is energized by a 480 VAC breaker located on MCC 2-2. The vapor extractor motor breaker includes an ON/OFF switch, a red RUN indicating light and a RESET pushbutton.

The seal oil vapor extractor is normally started and stopped from the main control room. A pistol grip OFF/ON control switch is located on the BTG board in the control room, typically in the ON position. The control switch is equipped with indicating lights to give the control room operator the extractor status. A GREEN indicating light will indicate the extractor is not running, while a RED light indicates to the operator that the extractor is running.

The generator seal oil reservoir vapor extractor is also equipped with a local REMOTE/OFF/LOCAL switch, located at the extractor on the turbine elevation. During normal operation, the local switch is in the REMOTE position and control of the vapor extractor is from the control room. When in LOCAL the vapor extractor is in operation from the local controller. In the OFF position, the extractor cannot be start from the control room BTG switch. The local control switch is also includes indicating lights to indicate the operating status of the vapor extractor. A GREEN indicating light indicates the extractor is not running, while a RED light indicates that the extractor is running.

2. Generator Gas System

1. Function

The Generator Gas System performs the following functions:

➢ Maintains gas pressure in the machine at the desired value

➢ Indicates the condition of the machine with regard to gas pressure, temperature, and purity

➢ Provides means for safely supplying or removing hydrogen from the machine

➢ Dries the gas and removes any water vapor which might enter the machine from the seal oil

2. Detailed Description

Nearly all generators for large steam turbines use hydrogen for cooling. Hydrogen is used because it has a better heat removal capacity than air. Hydrogen also has significant disadvantages as compared to air from the perspective of safety and convenience. Mixtures of from 4.1% to 74.2% of hydrogen are explosive. This fact implies that the Generator Gas System must be designed to monitor and maintain the purity of hydrogen in normal operation. It also means that there must be a means to safely fill and pressurize the generator casing with hydrogen and purge the casing when maintenance is to be done.

The Generator Gas System includes the following components:

➢ Hydrogen Bulk Storage and Supply Manifold

➢ Carbon Dioxide Storage and Supply Manifold

➢ Hydrogen Distribution Tube (inside the generator)

➢ Carbon Dioxide Distribution Tube (inside the generator)

➢ Hydrogen Monitoring System

➢ Gas Dryer

➢ Liquid Level Detectors

Hydrogen Bulk Storage and Supply Manifold

The generating station has a bulk supply for hydrogen, shown in Figure 2.3. Outside of the main plant building there is a hydrogen building that includes the hydrogen bottles and manifolds that supply hydrogen to both of the generating units.

[pic]

Figure 2.3 Hydrogen Tanks

The Unit 2 hydrogen supply manifold and associated valving functions to isolate the hydrogen bulk storage from the generator and to allow the addition of hydrogen to the generator in a safe, controlled manner. Hydrogen is supplied to the supply manifold through an isolation valve. A pressure regulator is located downstream of the isolation valve. The pressure regulator controls the flow of hydrogen to the generator during filling operations and maintains the hydrogen pressure in the generator during normal operation. The pressure regulator is equipped with inlet and outlet pressure gauges so the operation of the regulator may be monitored. Additionally, a pressure switch is located upstream of the regulator which annunciates a low pressure alarm if the supply pressure to the regulator decreases to 75 psig. A vent valve is located downstream of the regulator which is opened when setting the regulator.

Downstream of the pressure regulator are two isolation valves, which are opened when supplying hydrogen to the generator. A removable link is located between the two isolation valves and is only installed when hydrogen is being added to the generator. A vent line is located between the last isolation valve and the generator hydrogen distribution tube. The vent line is used during initial hydrogen filling (purging the CO2 from the generator) and when purging the hydrogen from the generator (filling with CO2). The line is equipped with an isolation valve and a low point drain valve. The vent line is routed out of the building to an area where there is no danger of ignition.

CO2 Storage and Supply Manifold

Bulk carbon dioxide is stored in 11 individual pressurized cylinders, shown in Figure 2.4. The cylinders are stored just behind the hydrogen control panel, adjacent to the operator room on the pump room floor.

[pic]

Figure 2.4 Carbon Dioxide Cylinders

The carbon dioxide supply manifold and associated valving is located below the turbine generator on the pump room floor. The function of the carbon dioxide manifold is to provide a means of safely removing and replacing hydrogen from the generator casing without allowing for an explosive mixture of hydrogen in air or air in hydrogen to form. Carbon dioxide is supplied to the supply manifold through an isolation valve. A pressure relief valve set at 100 psig is located upstream of the isolation valve to prevent over-pressurization of the carbon dioxide header. The relief valve relieves to the atmosphere. A pressure gauge is also located upstream of the isolation valve so the carbon dioxide supply pressure may be monitored. The carbon dioxide flows through a second isolation valve to the carbon dioxide distribution tube. A vent line is located between the last isolation valve and the generator carbon dioxide distribution tube. The vent line is used when filling the generator with hydrogen (purging the CO2 from the generator). The line is equipped with an isolation valve. This vent line joins with the hydrogen vent line to a point located out of the building.

Hydrogen and CO2 Distribution Tubes

These distribution tubes are simply perforated pipes inside the generator casing connected to piping from the gas control valves. The pipes have many holes along their length so that when gas is admitted it is evenly distributed through the generator casing. The hydrogen distribution tube is installed along the top centerline of the casing while the CO2 distribution tube is installed along the bottom centerline. The reason that the hydrogen tube is on the top and the CO2 tube is on the bottom is the relative densities of hydrogen and CO2. The hydrogen is much less dense, and therefore lighter. Arranging the distribution tubes in this way minimizes the mixing of the gases when the generator is filled with hydrogen or purged with CO2.

Hydrogen Control Panel

The function of the hydrogen control panel is to provide instrumentation which enables the operator to safely operate and monitor the Generator Gas System. The hydrogen control panel uses electronic transmitters to sense the generator hydrogen pressure, the generator fan differential pressure and the purity blower differential pressure. The hydrogen control panel consists of the following:

➢ Purity Blower

➢ Purity Meter

➢ Dual element gauge

• Generator fan differential pressure

• Hydrogen pressure

➢ Hydrogen pressure alarms

➢ Hydrogen purity alarms

➢ Seal oil alarms

The purity blower continuously draws a sample of the gas mixture in the generator housing and discharges the sample back to the generator. Since the purity blower is designed to operate at a constant speed, the differential pressure developed across the blower is directly proportional to the density of the sampled gas. The purity blower differential pressure signal is electronically reconditioned (density of hydrogen, pressure compensated) in a divider module in order to obtain the actual hydrogen purity. This reconditioning is necessary since the gas density is dependent upon the ambient pressure and temperature. The purity blower may be aligned to sample from either the hydrogen or the carbon dioxide distribution tubes.

The purity indicator scale is divided into three sections. Near the center of the scale is a point marked "100% - Air". This point provides a means of calibrating the indicator without removing the hydrogen from the generator. However, the calibration is beyond the scope of this text and is not discussed further. The upper end of this dial consists of a scale showing the percentage of carbon dioxide present in a mixture of carbon dioxide and air. This portion of the scale is used when carbon dioxide is being introduced into the generator. The lower end of the dial consists of a scale to indicate the percentage of hydrogen present in a mixture of hydrogen and air. This portion of the scale is used when filling the generator with hydrogen and during normal unit operations. During normal operation of the generator with both the air side and hydrogen side seal oil pumps in operation, the hydrogen purity should be maintained at 97% or greater. If the unit is being operated with the hydrogen seal oil pump shut down, the hydrogen purity should be maintained at 90% to avoid excessive use of hydrogen. The air side and hydrogen side seal oil pumps are discussed in detail in Section 2.3.

A differential pressure transmitter is connected directly to the generator housing that senses the differential pressure developed by the generator rotor fan. This differential pressure can be used as a check on the purity indicator.

The hydrogen pressure transmitter is connected directly to the generator housing and senses the pressure within the generator. The transmitted pressure signal is used by the hydrogen control panel not only to compensate for the hydrogen density when determining purity, but also to supply signals to the following:

➢ A remote pressure indicator

➢ High and low pressure alarm switches

The high and low pressure switches provide an indication when the gas pressure in the machine exceeds 56 psig or decreases to 18 psig.

Gas Dryer

Moisture is removed from the hydrogen in the generator by the alumina filled gas dryer, as illustrated in Figure 2.5, manufactured by Lectrodryer. The gas dryer is located adjacent to the condenser on the pump room floor. A portion of the hydrogen discharged from the generator multistage blower is directed to the gas dryer. The hydrogen enters the top of the gas dryer through a two-way valve and flows through the gas dryer chamber which is filled with activated alumina. The activated alumina absorbs any moisture in the hydrogen gas. After flowing through the activated alumina bed, the hydrogen exits the bottom of the gas dryer through a second two-way valve and returns to the generator.

[pic]

Figure 2.5 Gas Dryer Assembly

The activated alumina desiccant is regenerated periodically with a blower and heater arrangement. The blower takes suction from the atmosphere and discharges the air to the gas dryer two-way inlet valve. Inside the gas dryer, the air flows over an electric heating coil and downward through the activated alumina desiccant bed. The activated alumina releases the moisture to the regenerating hot air flow. The moisture laden air is discharged to the atmosphere through the two-way outlet valve. (The two-way valves isolate the hydrogen filled side of the air dryer from the air filled regenerating side.)

The gas dryer inlet and outlet two-way valves always operate together by the common control lever and linkage arrangement. This prevents the accidental mixture of hydrogen gas and regenerating air.

3. Technical Design Data

|Gas Dryer |

|Manufacturer |Lectodryer |

|Type |AAC |

|Size |25 |

|MAWP |165 psi |

|Electrical Supply |480 VAC/3 phase/60 Hz |

|Serial Number |203-14 |

4. Operation, Control and Safety

Integrated Operation

The operation of the hydrogen control panel is critical to the overall operation of the Generator Gas System. The hydrogen control panel indications should be monitored closely to ensure that problems are detected early with the Generator Gas System and corrected as necessary.

Following a long term shutdown (after the generator has been opened), the generator must be purged with CO2 before adding hydrogen to the generator casing. Carbon dioxide gas is used as a "buffer" between the hydrogen and air since a mixture of hydrogen and air is explosive when the mixture is between 4.1% and 74.2% hydrogen. Below 4.1% hydrogen the gas is too dilute, and there is no danger of explosion. However, there is danger of fire. If the hydrogen is very pure, above 74.2%, there is also no danger of explosion. Using carbon dioxide when charging and purging the generator prevents air and hydrogen from forming an explosive mixture. Therefore, the hydrogen control panel monitoring equipment should be in service whenever the Generator Gas System is in service.

When purging air from the generator with carbon dioxide, the purity meter is connected to the hydrogen distribution tube by opening valves 2 and 4 and closing valves 1 and 3 in the purity meter sample lines. The hydrogen supply manifold should be inspected to verify it is isolated from the generator. The hydrogen supply valves should be closed and the removable link removed with blanks installed. Carbon dioxide is then admitted to the generator housing by opening the carbon dioxide supply valves and closing the carbon dioxide distributing tube vent valve. The hydrogen distributing tube vent valve is opened to allow the air in the generator to be released. Carbon dioxide supply from the storage cylinders should be throttled as necessary to maintain a carbon dioxide supply pressure of 3-5 psig. The frost line should be monitored on the carbon dioxide piping. It should disappear approximately 10 feet from the point where the supply line enters the generator. When the purity meter indicates the atmosphere in the generator housing is 95% carbon dioxide the carbon dioxide supply valves are closed and the hydrogen distributing tube vent valve is also closed. It should be noted that approximately one and a half times the generator volume of carbon dioxide is required for the purge. The generator is now prepared to have the carbon dioxide replaced with hydrogen.

When replacing the carbon dioxide in the generator with hydrogen, the purity meter is connected to the carbon dioxide distribution tube by opening valves 1 and 3 and closing valves 2 and 4 in the purity meter sample lines. This is necessary because the poorest hydrogen sample will collect at the bottom of the generator since hydrogen is less dense than both carbon dioxide and air. The density meter should be checked to verify adequate carbon dioxide is present in the generator before admitting hydrogen. The density meter should read approximately 145%. The removable link from the hydrogen supply header is inserted. The hydrogen supply header isolation valves are then opened, and the carbon dioxide distributing tube vent valve is also opened. The hydrogen supply pressure regulator is then opened using the local T handle to maintain 3-5 psig in the hydrogen supply header. Once the purity in the generator reaches 95% hydrogen, the carbon dioxide vent valve is closed and the hydrogen pressure is increased to rated pressure by opening the regulator. It should be noted that during initial filling, the hydrogen pressure may be adjusted to slightly less than rated pressure as a slight pressure increase will result when the unit is synchronized and the generator is loaded due to the internal temperature increase. Normal unit operation, generator hydrogen pressure is automatically maintained above 45 psig by the pressure regulator.

The hydrogen gas dryer is placed in service when the generator is filled with hydrogen. The gas dryer chamber is equipped with a glass window which enables the operator to monitor the condition of the activated alumina. When completely dry, the color of the activated alumina is cobalt blue. As it absorbs moisture, it turns grayish white indicating that regeneration is necessary. The activated alumina is regenerated by manually positioning the three-way control lever and starting the blower motor and heating element. When the activated alumina is dry, its color returns to cobalt blue. The gas dryer is equipped with a temperature switch to prevent the activated alumina from overheating. Overheating the desiccant can ruin its moisture removal capabilities.

The liquid detectors operate mechanically through floats. When liquid collects in the float bowl, the float rises and contacts an alarm switch. The switch triggers a WATER DETECTOR LEVEL HIGH alarm. When the alarm sounds, the float bowls should be drained and monitored frequently afterwards to determine if the accumulation is due to natural condensation, or due to a more serious cause such as a hydrogen cooler tube leak or hydrogen seal problem.

When the liquid detectors are drained, the amount of fluid recorded and the type of fluid analyzed. Discolored and oily fluid is indicative of a problem with the Generator Seal Oil System. The liquid detector isolation valves must both be closed before opening the drain valve to ensure that hydrogen does not blow from the generator when the liquid is drained. Hydrogen blowing from the generator could cause an explosive mixture of air and hydrogen to form.

Prior to a long term shutdown or when it is necessary to open the generator, the generator must be purged with CO2 before adding air to the generator casing. Again, the carbon dioxide gas is used as a "buffer" between the hydrogen and air since a mixture of hydrogen and air is explosive when the mixture is between 4.1% and 74.2% hydrogen.

When purging hydrogen from the generator with carbon dioxide, the purity meter is connected to the hydrogen distribution tube by opening valves 2 and 4 and closing valve 1 and 3 in the purity meter sample lines. The hydrogen supply manifold must be isolated from the generator. The hydrogen supply valves are closed, the removable link removed and blanks installed. Carbon dioxide is then admitted to the generator housing by opening the carbon dioxide supply valves and closing the carbon dioxide distributing tube vent valve. The hydrogen distributing tube valve is opened to allow the pressurized hydrogen in the generator to be released. Carbon dioxide supply from storage should be throttled as necessary to maintain a carbon dioxide supply pressure of 3-5 psig. The frost line should be monitored on the carbon dioxide piping. It should disappear approximately 10 feet from the point where the supply line enters the generator. When the purity meter indicates the atmosphere in the generator housing is 95% carbon dioxide the carbon dioxide supply valves are closed and the hydrogen distributing tube vent valve is also closed. It should be noted that approximately one and a half times the generator volume of carbon dioxide is required for the purge. The generator is now prepared to have the carbon dioxide replaced with air.

When purging carbon dioxide from the generator with air, the purity meter is connected to the carbon dioxide distribution tube by opening valves 1 and 3 and closing valves 2 and 4 in the purity meter sample lines. The carbon dioxide supply line is isolated from the closing the carbon dioxide supply valves. The hydrogen distributing tube vent valve is closed and the carbon dioxide distributing tube vent valve is opened. A cap from the pipe below the hydrogen supply valve (from the area where the link was removed) must be removed and a Chicago fitting installed. A hose and a portable air dryer are attached to a station air connection and to the Chicago fitting. Station air is then supplied to the generator through the air dryer and supply valve. The air is added, until the purity meter reads 100%. Once the purity meter reads 100%, the station air supply valve and hydrogen supply valve may be closed. A purity meter reading of 100% indicates that generator is free of concentrated carbon dioxide and is safe to enter for inspection.

Hydrogen Bulk Storage

The hydrogen bulk storage regulators automatically regulate the hydrogen pressure to maintain the hydrogen supply to the generator units. There are no controls associated with these regulators. However, each regulator is equipped with a manual handle to manually open or close the regulator if necessary.

The BULK HYDROGEN LOW PRESSURE alarm is annunciated when the pressure decreases to 400 psig. This alarm alerts the operations department that the hydrogen bottles must be changed.

Hydrogen Supply Header

The Unit 2 hydrogen supply header valves are manually operated to supply hydrogen to the generator or to isolate the supply header from the generator. The hydrogen supply header pressure regulator is adjusted to maintain the desired hydrogen pressure using the T handle on the regulator.

CO2 Supply Header

Similarly, the Unit 2 carbon dioxide supply header valves are manually operated to supply carbon dioxide to the generator or to isolate the supply header from the generator. There is no pressure regulator associated with the carbon dioxide supply and therefore the carbon dioxide pressure must be adjusted by throttling the carbon dioxide supply valve.

Hydrogen Control Panel

The hydrogen control panel monitoring equipment is placed in service whenever power is supplied to the control enclosure. The purity blower is controlled a ON-OFF switch located in the control enclosure. When the control switch is placed in the ON position, the purity blower starts and continues to run until the control switch is placed in the OFF position.

The hydrogen control panel also includes the following alarms:

➢ Hydrogen Purity High/Low

➢ Hydrogen Pressure High

➢ Hydrogen Supply Pressure Low

➢ Water Detector High

➢ Hydrogen Temperature High

➢ Defoaming tank Level High

➢ Air Side Seal Oil Pump Off

➢ Seal Oil Pressure Low

➢ Hydrogen Side Level Low

➢ Seal Oil Turbine Backup Pressure Low

➢ Hydrogen Side Seal Oil Pump Off

➢ Air Side Seal Oil Backup Pump Running

Gas Dryer

The gas dryer is controlled locally from the heater and fan switches. In the ON position the fan or heater will operate continuously. The flow through the dryer is controlled by the manually operated lever that controls the inlet and outlet two-way valves. In the upper position the dryer will dry the generator gas. With the lever in the lower position and the fan and heater ON, the desiccant in the dryer will be reactivated.

Liquid Level Detectors

There are no controls associated with the liquid level detectors. However, a WATER DETECTOR LEVEL HIGH alarm is annunciated if the level in a detector increases to high level.

Control Room Controls

There are no controls located in the control room associated with the Generator Gas System. However, indications are provided for hydrogen pressure and hydrogen purity.

3. List of Instrumentation and Controls

|TABLE 1 – LOCAL INDICATING INSTRUMENTS |

|INSTRUMENT |FUNCTION/DESCRIPTION |NORMAL RANGE |

|SEAL OIL SYSTEM |

|N/A |GLAND SEAL OIL COLLECTOR END PRESSURE |±2 "H2O |

|N/A |AIR SIDE SEAL OIL PRESSURE |60-65 PSIG |

|N/A |GLAND SEAL OIL TURBINE END PRESSURE |±2 "H2O |

|N/A |PRESSURE REGULATOR ACTUATOR PRESSURE |55-65 PSIG |

|N/A |AIR SIDE DISCHARGE PRESSURE |55-65 PSIG |

|N/A |HYDROGEN SIDE DISCHARGE PRESSURE |90-100 PSIG |

|N/A |HYDROGEN SIDE TEMPERATURE |90-100 F |

|N/A |AIR SIDE TEMPERATURE |90-100 F |

|N/A |HYDROGEN DOWNSTREAM PRESSURE |120-130 PSIG |

|GENERATOR GAS SYSTEM |

|HYDROGEN PANEL |PURITY METER |100% HYDROGEN |

|HYDROGEN PANEL |HYDROGEN AND FAN PRESSURE |FAN 50-60 "H2O |

| | |H2 45-55 psig |

|n/a |Hydrogen (Control Regulator) Pressure |45-55 psig |

|n/a |CO2 Pressure |0 |

|Generator |

|n/a |Seal Oil Pressure (Turbine End) |55-65 psig |

|n/a |Seal Oil Pressure |55-65 psig |

|n/a |Bearing No. 5 Temperature |130-140 F |

|n/a |Bearing No. 6 Temperature |130-140 F |

|n/a |WTA Regulator Exciter Field Current |25-35 Amps |

|n/a |WTA Regulator Exciter Field Voltage |65-75 V |

|n/a |WTA Regulator PMG Supply Voltage |120-130 V |

|Table 2 - Control Room Indicating Instruments |

|Instrument |Function/Description |Normal Range |

|Seal Oil System |

|n/a |None | |

|Generator Gas System |

|n/a |Hydrogen Pressure |45-55 psig |

|n/a |Hydrogen Purity |100 % Hydrogen |

|Generator System |

|n/a |Generator Watt Meter |Load MW |

|n/a |Generator VAR Meter |0-50 VAR |

|n/a |Generator Balance |0 V |

|n/a |Generator Ampere |4-6 KA |

|n/a |Generator DC Field Amperes |28-32 |

|n/a |Generator DC Field Volts |60-70 |

|n/a |Generator Volts |20-25 |

|n/a |Generator Frequency |59.99-60.01 |

|n/a |22/115 Transformer No. 1 |2450-2550 Amps |

|n/a |22/115 Transformer No. 2 |2450-2550 Amps |

4. List of Alarms and Setpoints

|ALARM CONDITIONS |

|ALARMS |INITIATING DEVICE(S) |DEVICE SETPOINT(S) |

|CONTROL ROOM (BTG) ALARMS |

|HYDROGEN ANNUNCIATOR PANEL ALARM |HYDROGEN PANEL |N/A |

|EXCITER SWITCHGEAR ALARM |RELAY |N/A |

|FIELD BREAKER TRIP ALARM |RELAY |N/A |

|CONTROL ROOM (GENERATOR PANEL) ALARMS |

|GENERATOR IS MOTORING |RELAY |N/A |

|GENERATOR LOSS OF FIELD |RELAY |N/A |

|GENERATOR GROUND FAULT |RELAY |N/A |

|HP 112/113 (GENERATOR BREAKER) FAILURE |RELAY |N/A |

|86G RELAY TRIP |RELAY |N/A |

|86T RELAY TRIP |RELAY |N/A |

|EXCITER POWER NO. 1 OR 2 FIRING CIRCUIT |RELAY |N/A |

|EXCITER PULSE NO. 1 OR 2 FIRING CIRCUIT |RELAY |N/A |

|EXCITER AUTO TRIP |RELAY |N/A |

|EXCITER REGULATOR TRIP |RELAY |N/A |

|EXCITER FORCING ALARM |RELAY |N/A |

|EXCITER MAXIMUM EXCITATION TIMING |RELAY |N/A |

|EXCITER FIELD GROUND DETECTOR |RELAY |N/A |

|EXCITER VOLTS/HERTZ LIMITING |RELAY |N/A |

|HYDROGEN CONTROL PANEL |

|HYDROGEN PURITY HIGH/LOW |PURITY METER |> 100% |

| | |< 90% |

|Hydrogen Pressure High |Hydrogen Pressure Transmitter|56 High |

| | |18 Low |

|Hydrogen Supply Pressure Low |PS-3 |75 psig |

|Water Detector High |ASH614A/B/C |High |

|Hydrogen Temperature High |n/a |45 C |

|Defoaming Tank Level High |LS-6 |High |

|Air Side Seal Oil Pump Off |PDS-7 |5 psi |

|Seal Oil Pressure Low |PDS-8 |8 psi |

|Hydrogen Side Level Low |LS-9 |Low |

|Seal Oil Turbine Backup Pressure Low |PS-10 |70 psig at seals |

|Hydrogen Side Seal Oil Pump Off |PDS-11 |5 psi |

|Air Side Seal Oil Backup Pump Running |PDS-8 |8 psi |

5. List of System Constraints

THE FOLLOWING CONSTRAINTS LISTED ARE SYSTEM SPECIFIC OPERATIONAL CONSIDERATIONS THAT MUST BE CLOSELY FOLLOWED. FAILURE TO RECOGNIZE THESE CONSTRAINTS MAY RESULT IN PERSONNEL INJURY OR EQUIPMENT DAMAGE:

General

• Follow proper startup procedure for steam turbine in conjunction with generator startup.

• Follow proper startup soak hold, at 12MW, when synchronizing the generator.

• Do not hold turbine speed, during startup, in any of the predetermined critical speed zones.

• Avoid operation at less than 12MW for extended periods of time.

• Avoid off-frequency operation.

• Follow proper synchronizing procedure during generator startup.

• Follow capability curve and starting and loading instructions.

Generator Gas

• During normal operation the hydrogen purity should be maintained above 95%.

• During normal operation the hydrogen pressure should be maintained above 45 psig.

• Gas changing operations may only be performed if the turbine is at standstill or if on turning gear.

• The gas dryer should be reactivated when the dryer crystals turn gray in the observation port.

• After a shutdown, none should be allowed in the generator until the area is deemed safe by the use of a portable gas meter.

Seal Oil System

• Seal oil system must be in service if the generator is charged with hydrogen.

• Seal oil pressure should be maintained at 12 psi above the generator hydrogen pressure.

• The seal oil vapor extractor should be in continuous service.

• The seal oil coolers should maintain the oil temperature outlet between 80 and 120 *F.

• The seal oil knife type filters should be rotated once per (8 hour) shift.

• The generator can be operated for short periods with the hydrogen side seal oil pump off.

6. References

1. P&ID

a. Ebasco Services Incorporated, Flow Diagram Condensate Cooling Water, CTAL-HPK2-M-F-00007, Rev. 0

2. Electrical One Line Diagrams

a. Reynolds, Smith and Hill, Unit No. 2 Addition, Generator, Step-up Transformer Single Line, E-1, Rev. 0

b. Reynolds, Smith and Hill, Unit No. 2 Addition, Station Service Equipment Single Line, E-2, Rev. 0

c. Reynolds, Smith and Hill, Unit No. 2 Addition, 480 V Unit Substations Single Line and Arrangement Diagram, E-4, Rev. 0

3. Control Diagrams

a. Reynolds, Smith and Hills, Seal Oil Pump Hydrogen Side, S-114

b. Reynolds, Smith and Hills, Seal Oil Backup Pump, S-188

c. Reynolds, Smith and Hills, Hydrogen Vapor Extractor, 191

d. Reynolds, Smith and Hills, Seal Oil Pump Air Side, S-188

4. Instrument Loop Diagrams

a. Hydrogen Coolers Temperature Control, Loop 41

b. Hydrogen Purity, Loop 200

c. Hydrogen Pressure, Loop 231

d. Hydrogen Seal Oil Pump Off, Loop 617

e. Hydrogen System DC Power Failure, Loop 619

f. Air Side Seal Oil Pump Off, Loop 625

g. Seal Oil Pressure Low, Loop 626

h. Hydrogen Side Seal Oil Level, Loop 627

i. Seal Oil Backup Pressure Low, Loop 628

j. Hydrogen Side Seal Oil Pressure Low, Loop 629

k. Air Side Seal Oil Backup Pump Running, Loop 630

5. Instruction Manuals

a. Westinghouse, Generator Instruction Book, City of Tallahassee, A.B. Hopkins Station, Unit 2, 21011, December 1975

b. Westinghouse, Steam Turbine-Generator Startup, City of Tallahassee, A.B. Hopkins Station, Unit 2, 1250-C917, October 1976

6. Miscellaneous

a. Reynolds, Smith, and Hills, Connection Diagrams, C-1 through C-198

b. Unit 2 Steam Turbine System Description and Operating Procedure, 2-ST-SD and 2-ST-OP

c. Unit 2 Electrical Distribution System Description and Operating Procedure, 2-ED-SD and 2-ED-OP

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download