Steam Turbine Operation
Lube Oil System
Training Lesson
ALSTOM (Switzerland) Ltd
ABC ABCD
ABC ABCD
Steam Turbine Operation
Lube Oil System
We reserve all rights in this this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden. Copyright© by ALSTOM (Switzerland) Ltd 2007 This is a training lesson. It provides overall information about the specific system only. To understand the operation concept in detail the project specific documents as defined in the document reference section have to be included together with this lesson. All mentioned / attached attached values and settings settings are for information only. Typical values are used to clarify particular subjects. Settings furthermore are subject to change site specifically during commissioning. For actual values please refer to the final plant specific Operation & Maintenance Documentation.
Power Plant Training Center CSXA220220en_
Page 2
ABC ABCD
Steam Turbine Operation
Lube Oil System
We reserve all rights in this this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden. Copyright© by ALSTOM (Switzerland) Ltd 2007 This is a training lesson. It provides overall information about the specific system only. To understand the operation concept in detail the project specific documents as defined in the document reference section have to be included together with this lesson. All mentioned / attached attached values and settings settings are for information only. Typical values are used to clarify particular subjects. Settings furthermore are subject to change site specifically during commissioning. For actual values please refer to the final plant specific Operation & Maintenance Documentation.
Power Plant Training Center CSXA220220en_
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ABC ABCD
Steam Turbine Operation
Lube Oil System
Table of Contents Document Reference ............................ .......................................... ............................ ............................ ............................ ............................ ......................... ......................... .............. 5 Typical Documents ........................... ......................................... ............................ ............................ ............................ ............................ ........................... .......................... ............. 5 O&M Documentation ........................... ......................................... ............................. ............................. ............................ ............................ .......................... ..................... ......... 5 Lesson Objectives.............................. Objectives............................................ ............................ ............................ ............................. ............................. ......................... ........................ ................ ... 6 Overview .......................... ........................................ ............................ ............................ ............................ ............................ ............................ ......................... ......................... ................... ..... 7 System Function ........................... ......................................... ............................ ............................ ............................ ............................ ............................ ......................... ................ ..... 7 Lube Oil Tank ........................... ........................................ ........................... ............................ ........................... ........................... ............................ ......................... ..................... .......... 8 Oil Vapor Extractor ........................... ......................................... ............................ ........................... ........................... ............................ .......................... .......................... .............. 9 Lube Oil Pumps .......................... ....................................... ........................... ............................ ........................... ........................... ............................ .......................... ................... ....... 9 Lube Oil Pressure Control................................... Control................................................. ............................ ............................ ........................... .......................... ..................... ........ 12 Lube Oil Temperature Control ........................... ......................................... ............................ ............................ ............................ ............................ ..................... ....... 13 Lube Oil Filter .......................... ........................................ ............................ ............................ ............................ ............................ ............................ ......................... .................. ....... 14 Lube Oil Supervision ........................... ......................................... ............................ ............................ ............................ ............................ ......................... ..................... .......... 15 Lube Oil around the Bearings ........................... ......................................... ............................ ........................... ........................... ............................ ....................... ......... 16 Lube Oil Purifier .......................... ....................................... ........................... ............................ ........................... ........................... ........................... .......................... .................. ..... 16 Lube Oil Block Diagram ........................... ........................................ ........................... ............................ ............................ ............................ ......................... ................. ...... 18 Operation and Supervision ............................ .......................................... ............................. ............................. ............................ ............................ .......................... .............. 19 General.................................. General................................................ ............................ ............................ ............................ ............................ ............................ ......................... ................... ........ 19 Preparation Prior to Start-up ........................... ......................................... ............................ ............................ ............................ ............................ ........................ .......... 19 Start-up .......................... ........................................ ............................ ............................ ............................ ............................ ............................ ........................ ........................ ................. ... 20 Normal Operation .......................... ........................................ ............................ ............................ ............................ ............................ ............................ ........................ ............ 21 Shut-down .......................... ........................................ ............................ ............................ ............................ ............................ ............................ ......................... ....................... ............ 22 Emergency Operation ........................... ......................................... ............................ ............................ ............................. ............................. ........................ .................. ........ 22 Protection ........................... ......................................... ............................ ............................ ............................ ............................ ............................ ......................... ....................... ............ 23 Trouble Shooting............................ Shooting.......................................... ............................ ........................... ........................... ............................ ............................ ........................... ................ ... 23 Routine Operation Maintenance.................... Maintenance.................................. ............................ ........................... ........................... ............................ ........................... ................ ... 24 Exercises.............. Exercises ............................ ............................ ............................ ............................ ........................... ........................... ............................ ......................... ......................... ................. ... 25 General.................................. General................................................ ............................ ............................ ............................ ............................ ............................ ......................... ................... ........ 25 Overview ............................ .......................................... ............................ ............................ ........................... ........................... ............................ .......................... ........................ ............ 25 Exercises Functionality, System Outline ........................... ......................................... ............................ ............................ ............................ ....................... ......... 26 Exercises Component Name, KKS Designation & Function ............................. ........................................... ............................ ..................... ....... 27 Exercises System Instrumentation, Instrumentation, KKS Designation, Designation, Indication, Indication, Set Point .......................... ........................................ ................. ... 28 Exercises Operation & Routine Maintenance ........................... ......................................... ............................ ............................ ............................ ................ 29 Exercises Trouble Shooting.................... Shooting................................... ............................. ............................ ............................ ............................ ......................... ................... ........ 30 Exercises Routine Maintenance................ Maintenance............................... ............................. ............................. ............................. ............................. ......................... ............... ..... 31 Test Questions for Verification of Learning Progress ........................... ......................................... ............................ ............................ .................. .... 32 Questions:........................................ Questions:.......................... ........................... ........................... ............................ ............................ ............................ .......................... ........................ ............ 32 Lesson Test Questions Solution Key ............................. ........................................... ............................ ............................ ............................ ......................... ............. 36 Summary ........................... ......................................... ............................ ............................ ............................ ........................... ........................... ......................... ......................... ................. ... 37
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ABCD
Steam Turbine Operation
Lube Oil System
Table of Figures Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure
1: Oil Tank for Steam Turbine Lube Oil System (Typical) ............................................................ 8 2: Oil Vapor Extractor, Butterfly Valve and Air Filter (Typical) ...................................................... 9 3: Gear Pump (Typical) .......................................................................................................... 10 4: Auxiliary Pump (View from Inside Lube Oil Tank) (Typical) .................................................... 10 5: Emergency Pump (Typical).................................................................................................. 11 6: Constant Pressure Valve (Typical)........................................................................................ 12 7: Temperature Control Diagram (Typical) .............................................................................. 13 8: Tube and Shell Heat Exchanger, Control Valve (Typical)....................................................... 13 9: Lube Oil Twin Filter with Pressure Gauge (Typical) ............................................................... 14 10: Lube Oil Pressure Gauge (2 out of 3 Logic) (Typical).......................................................... 15 11: Lube Oil Purifier (Typical) ................................................................................................. 17 12: Lube Oil Emergency Lube Oil System Block Diagram (Typical)............................................ 18
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Steam Turbine Operation
ABCD
Lube Oil System
Document Reference Typical Documents
Typical documents are used to clarify aspects described in this lesson. These typical documents may not show project specific contents, deviations are possible. All typical documents are clearly identified.
O&M Documentation
O&M Documents are plant specific and form an important part of each training course. A selection of the most relevant O&M Documents has been made and included in the training course material. These documents provide a basis for exercises and personal notes, markings, etc. The most relevant documents for the operation training are: • P&IDs with legend • System descriptions •
Operating instructions Operating diagrams
•
Instrument lists
•
Set point lists Maintenance instructions
•
•
The O&M Documents are separated into: System specific documents • Overall plant specific documents The system specific documents are attached to each specific lesson, whereas the overall plant specific documents can be found in separate sections at the end of the training manual. •
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Steam Turbine Operation
ABCD
Lube Oil System
Lesson Objectives Upon completion of this lesson, the trainee is able to: •
Explain the function of the system on a block diagram during start up, normal operation and shut down.
•
To summarize the function of all components involved in the lube oil system.
•
Operate the function group according to the "starting & operating instruction of steam turbine" during all operation situations.
•
Is able to trouble shoot the lube oil system according to "lubricating and hydraulic oil system with integral jacking- and turning gear oil system".
•
To carry out a change over of the lube oil filter, from the in service unit to the stand by unit, with the respective maintenance documentation.
•
Describe all maintenance checks to be carried out during regular operation.
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Steam Turbine Operation
ABCD
Lube Oil System
Overview System Function
The turbine lubrication (lube oil) system performs the following function: • Lubricate the bearings of the generator and steam turbine. •
Supply of lube oil to the jacking oil (shaft lifting) and electro hydraulic safety system.
•
Removal of heat generated in the journal bearings by shaft rotation.
This is reached by the following: • • • • • •
Providing a specific lube oil flow to each bearing. Maintaining a constant lube oil temperature to consumers. Cleaning lube oil. Guiding lube oil to consumers.
•
Returning lube oil from consumers. Deaerating lube oil returning from the consumers.
•
Storage of lube oil at sufficient temperature.
•
Components
Maintaining a constant lube oil flow and pressure. Maintaining sufficient lube oil flow during emergency situations.
Therefore the following components are needed as a minimum: • Lube oil tank • • • • • • •
Vapor extractor Pumps (main, auxiliary, emergency) Constant pressure valve Cooler Temperature controller Filter Supply lines and orifices
•
Return lines Oil purifier
•
Instrumentation and controls
•
•
Air filter
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ABCD
Steam Turbine Operation
Lube Oil System
Lube Oil Tank
The tank is mainly used to store the lube oil. Also most system components are mounted on it. It is designed and sized to allow a sufficient deaeration (removing of entrained air bubbles in the returning lube oil flow from the bearings).
Figure 1: Oil Tank for Steam Turbine Lube Oil System (Typical)
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Steam Turbine Operation
ABCD
Lube Oil System
Oil Vapor Extractor
The lube oil vapor extractor maintains a slight vacuum in the lube oil tank, oil drain pipes and bearing pedestals. This not only removes oil vapor from the tank, but also prevents oil from leaking through the oil scrapers of the bearing pedestal. A butterfly valve upstream from the vapor extractor is used to adjust the vacuum in the tank. Ventilation with fresh air is provided via the air f ilter.
Figure 2: Oil Vapor Extractor, Butterfly Valve and Air Filter (Typical)
Lube Oil Pumps
Redundancy
A total loss of lube oil during operation will damage the bearings of the turbo set. Therefore three lube oil pumps are installed. Check valves after each pump ensure that stand-by pumps do not reverse during operation and that the lube oil is not discharged back into the tank. Pressure supervision transducers after each pump indicate a malfunction of the pump and initiate an automatic change over from one pump to the other. (Continued next page)
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Steam Turbine Operation
ABCD
Lube Oil System
Lube Oil Pumps (continued) Main Pump
The main lube oil pump is a gear pump (volumetric pump type), driven by the turbine shaft. It provides oil as soon as the shaft begins to turn, but reaches its design data already at approximately 80 % of nominal shaft speed.
CSXA401764.cdr
Figure 3: Gear Pump (Typical)
Auxiliary Pump
At low turning speeds during start-up, shut-down and turning gear operation, the main oil pump delivers insufficient oil and the required lube oil is then supplied by the auxiliary lube oil pump (centrifugal pump with AC motor). The auxiliary pump is designed for the full pressure and a flow rate of the required maximum (100 %).
Check valve
Auxiliary pump Suction cage CSXA401756.cdr
Figure 4: Auxiliary Pump (View from Inside Lube Oil Tank) (Typical)
(Continued next page)
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Steam Turbine Operation
ABCD
Lube Oil System
Lube Oil Pumps (continued) Emergency Pump
The emergency lube oil pump is a centrifugal, DC motor-driven back-up pump. It is powered by batteries and runs only for test purposes or i f the main and auxiliary lube oil pumps fail. To limit the DC power consumption, the emergency oil pump is designed with pressure and flow parameters below the required maximum at rated speed. The capacity is sufficient to ensure safe rundown of the turboset and cooling of the bearings if an AC power failure occurs. The discharge of the emergency oil pump is located after the coolers and filters for two reasons: •
Oil can be delivered to the system when these components are blocked.
•
Elimination of the pressure loss from these components allows the DC pump to be designed for a lower discharge pressure and less power consumption.
Figure 5: Emergency Pump (Typical)
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Steam Turbine Operation
ABCD
Lube Oil System
Lube Oil Pressure Control
Operation of Main and Auxiliary Oil Pumps
The oil supplied by the pumps during start-up and shut-down varies greatly, because of two reasons: • The main lube oil pump is a volumetric pump type. The volume flow of such a pump is proportional to the rotational speed and not depending on the back pressure. •
Constant Pressure Valve
Initially only the AC pump, then the AC plus the main oil pump, finally only the main oil pump is in operation.
To fit the oil supplied to the oil consumption of the bearings and to avoid an overpressure in the system induced by the gear pump, a constant pressure valve is installed, which guides the excessive oil before the filter back to the tank. To compensate for the variable pressure loss depending on the cleanliness of the filter, the pressure feedback signal for the valve is taken after the filter.
Screw
Spr ing
e l i n u r e s s l s e e r u p p e i m y s t e m r r u e s s e s l l e d m f i l t P r o a r n t r e c o w n s t d o
Piston
CSXA401766.cdr
Figure 6: Constant Pressure Valve (Typical)
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Steam Turbine Operation
ABCD
Lube Oil System
Lube Oil Temperature Control
Lube oil temperature is regulated by the inline lube oil cooler and a thermostatic valve. Downstream from the cooler, the thermostatic valve maintains the oil temperature at a constant value by passing part of the oil around the cooler. •
•
Hot oil from the pump and the cold oil from the cooler are mixed in the internally-sensed thermostatic valve. A cartridge with the expanding (controlling) medium moves the control cylinder to open either the cold or hot oil supply.
Operating temperature to oil system Pump
Or ifice
Thermostatic temperature control valve
Hot oil Oil cooler
Cooled oil
CSXA401765.cdr
Figure 7: Temperature Control Diagram (Typical)
Tube bundle
Heat exchanger
Thermostatic temperature control valve
CSXA401865.cdr
Figure 8: Tube and Shell Heat Exchanger, Control Valve (Typical)
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Steam Turbine Operation
ABCD
Lube Oil System
Lube Oil Filter
The lube oil filter consists of two 100 % filters.Differential pressure over the filter (an indication of the amount of dirt in the cartridge) is supervised continuously by a differential pressure switch, with remote and local indication. The filters, which can be changed over during operation, are equipped with vent valves.
3
7
5
6
4
2 8
1
9
10
Legend: 1 2 3 4 5 6 7 8 9 10
Oil inlet Oil outlet (clean side) Lef t side filter Right side filter Change-over handle Filling handle (cross-over ) Vent handle Vent sight glass Over flow toward tank Drain toward tank
CSXA403260.cdr
Figure 9: Lube Oil Twin Filter with Pressure Gauge (Typical)
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Steam Turbine Operation
ABCD
Lube Oil System
Lube Oil Supervision
Lube oil upstream from the bearings is supervised by three pressure transmitters whose outputs are processed in a 2-out-of-3 logic for turbine safety purposes. If rated lube oil pressure at the shaft level drops to below a minimum value, the turbine is tripped. The lube oil pumps cannot be switched off until the shaft is at standstill.
Figure 10: Lube Oil Pressure Gauge (2 out of 3 Logic) (Typical)
The pressure transmitters are also used to automatically start the auxiliary and emergency lube oil pumps. If the lube oil pressure drops ca. 60 %, a trip signal is actuated, the auxiliary • lube oil pump is started immediately, and the emergency lube oil pump is started after a 30s delay. If the lube oil pressure continues to drop and reaches the 40 % set point, the average value of the 3 pressure transducers is used to start both emergency and auxiliary pumps without delay. The transmitters can be tested one by one during operation by means of test valves. •
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Steam Turbine Operation
ABCD
Lube Oil System
Lube Oil around the Bearings
To adjust the flow rate separately for each bearing, individual supply lines from the lube oil supply header feed the bearings through orifices. Oil enters the bearing shell and drains into the bearing pedestal. To verify oil flow, sight glasses are installed in the individual return lines. Temperature indicators are installed in the return lines to supervise heat development in the bearings. The individual return lines merge into a return header leading to the tank.
Lube Oil Purifier
Purpose
The function of the lube oil purifier is to eliminate: • • • •
Function
Dirt sucked into the bearing pedestal. Water from the gland seals. Particles from erection or overhaul. Sludge from erosion of materials.
When two fluids are being separated, the heavier part collects at the periphery of the bowl and the lighter part near the center. Each fluid leaves the separator through its own outlet. The outlet of the heavier liquid is at a somewhat greater radius than the outlet for the lighter fluid. The more or less cylindrical division between the fluids is known as the interface. Its location is fixed by gravity disks of different diameters in the heavy-liquid outlet. The degree of separation obtained depends on the diameter of the gravity disks. A siphon in the inlet to the oil purifier unit protects the lube oil tank from being emptied by the purifier. (Continued next page)
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Steam Turbine Operation
ABCD
Lube Oil System
Lube Oil Purifier (continued)
Figure 11: Lube Oil Purifier (Typical)
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Steam Turbine Operation
ABCD
Lube Oil System
Lube Oil Block Diagram
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Figure 12: Lube Oil Emergency Lube Oil System Block Diagram (Typical)
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Steam Turbine Operation
ABCD
Lube Oil System
Operation and Supervision General
The operation is fully described in the operation manual, which should be read carefully. Nevertheless, the most important facts are listed in this section.
Preparation Prior to Start-up
Operating Method
The system may be operated using the following methods: • Manual operation from the control room via operator station and function group controller. Automatic operation by automatic start-up and shut-down sequencer. Normally the system will be operated using the automatic sequencer. However, during system checks or maintenance, the system has to be operated manually. •
Proper walk-down procedures and valve selection check lists are mandatory for a safe operation of the system. (See O&M Steam Turbine Mai ntenance Manual, section "Inspection") System Start-up Sequence
Before any operation may take place, the following systems have to be in operation: •
Lube oil cooling system, i.e. closed cooling water system.
For system start-up, the following has to be fulfilled: •
Lube oil level in the tank just below the maximum level (no oil in system yet, oil level is going to drop during start-up and filling of system).
•
Lube oil temperature above minimum temperature (to avoid cavitation of lube oil pumps), normally > 25° C (alarm > 20° C).
Emergency DC pump not in manual operation. There are no interlocks for these conditions, therefore operation has to prepare the system according to the specific operating procedure. •
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Steam Turbine Operation
ABCD
Lube Oil System
Start-up
Procedure
Supervision
When the function group is placed in operation, lube oil pressure is low because no pump is on. Since pressure supervision shows low pressure, the auxiliary oil AC pump will start. Pressure will remain low for a few seconds while the piping fills, but this will not start the DC pump because of a time delay at start-up of the function group. After a few seconds, pressure will rise and pressure supervision will indicate normal pressure. The DC pump will not start when it is released because pressure is now normal (above 40 % and 60 % respectively). The lube oil vapor extractor is started immediately at function group start-up. Pressure and temperature control as well as filtering are automatic and need no attention other than periodic checks. During steam turbine start-up, the main lube oil pump will increase the flow of oil proportionately with speed. At 90 % of rated turbine speed the auxiliary oil pump is automatically switched off as its operation is no longer necessary to maintain system pressure. When the auxiliary oil pump is switched off, the reduced oil supply is compensated by the constant pressure valve. Lube oil is then supplied only by the main oil pump, which is driven directly by the turbine. During start-up check for the following: • • • • •
• •
•
Auxiliary lube oil pump start. Oil vapour extractor start. Lube oil pressure, acknowledge MIN1 and MIN2 alarms. Emergency lube oil pump does not start. Manually switch ON/OFF emergency lube oil pump, supervise discharge pressure. Oil flows in sight-glasses on all automatic cooler and filter vents. Lube oil pressure upstream of bearing feed orifices between 1.5 to 1.7 barg (21.75 to 24.65 psig) at shaft level. Unobstructed lube oil flow through drain sight glasses at each bearing.
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Steam Turbine Operation
ABCD
Lube Oil System
Normal Operation
Procedure
The lube oil function group is in operation and the turbine controller regulates the process. The AC auxiliary and DC emergency pumps are on stand-by and are started-up in case the lube oil pressure drops below 60 % and 40 % respectively for any reason.
Supervision
Once per shift walk down the system, checking for the following: •
Local instrumentation for deviations from normal values.
•
Tank level at local level indicators.
• •
Oil temperature after the cooler. Lube oil system pressure.
•
Differential pressure across the filter.
Oil leaks. • Abnormal sounds or noises as well as vibrations from the pumps and piping. In case of dirty filter elements the lube oil filter has to be changed over to the stand by filter. •
Filter Change-over
Change-over to the stand by filter element is a simple manual action. With one lever or hand wheel both 2-way valves at the inlet- and outlet side can be changed at once. •
The standby filter must be filled and properly vented!
Air can destroy both the jacking- and turning gear pump immediately. Larger air pockets destroy the bearings. • The procedure for changing the lube oil filter during normal operation is described in detail in the maintenance manuals supplied with the unit. The documentation must be consulted when a change-over is required. •
Oil Cooler
Increased pressure drop in the cooler or temperature rise can be caused by contamination of the oil cooler. In normal cases this contamination appears only at the water side while the oil side shows just little changes even after years. To achieve a long lifetime of the cooler the water side should be inspected at least once a year.
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Steam Turbine Operation
ABCD
Lube Oil System
Shut-down
Procedure
Supervision
When the turbine has coasted down to 90 % of rated speed, the AC auxiliary oil pump is automatically started to supply oil during run-down. As a rule the lube oil system is shut down only if the average rotor metal temperature is <150° C / 302 F. In case of an emergency the lube oil system may be switched off for a short time at a metal temperature of max. 200° C / 392 F. However, under no circumstances and white metal temperature in the various bearings exceed 100° C / 212 F. When the lube oil function group is removed from service, the vapor extractor fan remains in operation for another 20 minutes. During this time the oil sticking to the fan's rotating parts is removed, therefore no excessive fan vibration will occur during the next start-up. During shut-down the following has to be supervised: • •
Auxiliary lube oil pump starts at 90 % rated speed. White metal temperatures in each bearing.
Emergency Operation
Automatic Operation Failure
All emergency situations are handled by the control system if the instrumentation and hardware are working properly and function group is “On”. If there is a malfunction in any of these devices, the pumps can be switched on manually at the single drive level. The DC emergency pump can also be switched on at the switch gear level. If no AC or DC power is available, or if the electric pumps fail, the main lube oil pump will continue to provide lubrication at low turbine speed because it is a volumetric type pump. In most cases this oil supply will save the bearings or will at least minimize damage.
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Steam Turbine Operation
ABCD
Lube Oil System
Protection
Emergency Shut-down
In case of an emergency the steam turbine can be tripped immediately by actuating the emergency push button in the control room or at the turbine. The shutdown sequence for the steam turbine systems is the same as during a normal shut-down.
Lube Oil Supply to the Bearings
The lube oil system is one of the most important auxiliary systems for the steam turbine. Without a sufficient supply of lube oil to the bearings, the machine will be seriously damaged and may be out of service for weeks. Therefore the supply pressure (2 out of 3 pressure measurement) in the distribution system is ensured as follows: •
AC auxiliary lube oil pump starts below 90 % nominal rotor speed.
•
AC auxiliary lube oil pump starts below 60 % nominal lube oil pressure without delay.
•
DC emergency lube oil pump starts below 60 % nominal lube oil pressure with a delay of 15 seconds. DC emergency lube oil pump starts below 40 % nominal lube oil pressure without delay.
•
Trouble Shooting General Remark
Troubleshooting has the goal to quickly return the equipment back to normal operation or full availability for operation. For fast and successful troubleshooting the following points are very important: •
Accurate and up-to-date logbooks (see section routine maintenance below). Main machine and system functionality know-how.
•
Abnormal and emergency operating procedures.
•
System
•
Troubleshooting procedures.
•
Good teamwork between operating and maintenance staff.
The system specific troubleshooting procedures are described in the following document: Maintenance description of lube oil system.
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Steam Turbine Operation
ABCD
Lube Oil System
Routine Operation Maintenance General Remark When the automatic control and protection systems are working properly, any particular attendance is not needed. Abnormalities will be alarmed and signalized. However, in order to prevent unprepared shutdowns by any safety device, regular routine maintenance is recommended. Logbook
Documents
A logbook with all readings of measurements as well as any observation regarding operation, starting and shutdown times should be kept. Overhauls and adjustments carried out should be recorded. The variation of values provides a picture of the system performance and allows quick and accurate identification of any abnormality. In detail the following documents describe the necessary actions: •
Starting & operating instruction of the steam turbine.
•
Maintenance description of lube oil system.
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Steam Turbine Operation
ABCD
Lube Oil System
Exercises General
To be able to understand the exercises the relevant chapter of the following project specific documents must be studied carefully: • P&ID incl. legend • Description of Steam Turbine Systems •
Starting and Operating Instructions of Steam Turbine
•
Instrument List
•
Set Point List
Overview
System & Components
This section contains the following exercises: • System Outline • •
Operation & Routine Maintenance
Component Name, KKS Designation & Function System Instrumentation
This section contains the following exercises: •
Operation Trouble Shooting
•
Routine Maintenance
•
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Steam Turbine Operation
ABCD
Lube Oil System
Exercises Functionality, System Outline
Exercise Task
Mark (with color pens) all media lines which belong to the lube oil system in your P&ID as follows: • Lube oil tank and supply to oil pump suction side Lube oil discharge and distribution lines to the bearings • •
Lube oil drain lines
Exercise Aids
•
Plant specific P&ID and legend to P&ID
Group Time Frame Presentation
•
Each trainee for himself
•
10 minutes
•
Discussion in classroom
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Steam Turbine Operation
ABCD
Lube Oil System
Exercises Component Name, KKS Designation & Function
Exercise Task
Fill-in the table below with the following information according to the example given in the first line: • Major components name KKS number • •
Short functional description
Mark all the major components listed on the following drawing:
Exercise Aids
Group Time Frame Presentation
•
Lube oil skid outline drawing
•
Plant specific P&ID and legend to P&ID
•
Lube oil skid outline drawing
•
Each trainee for himself
•
15 minutes
•
Discussion in classroom
Component Name
KKS - Number
Component Function
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Steam Turbine Operation
ABCD
Lube Oil System
Exercises System Instrumentation, KKS Designation, Indication, Set Point
Exercise Task
Fill-in the table below with the following information according to the example given in the first line: •
Instrument type
•
•
KKS number Function code Indication type
•
Set points for switching alarm or trip
•
Plant specific P&ID and legend to P&ID
•
Instrumentation list Set point list steam turbine
•
Exercise Aids
•
Group Time Frame Presentation
•
Group work with max. 4 trainees per group 15 minutes
•
Group presentation in front of class
•
Instrument Type
KKS - Number
F-Code
Incic
Switch
Alarm
Trip
P-Gauge
MAV21 CP001
PI
Local
-
-
-
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Steam Turbine Operation
ABCD
Lube Oil System
Exercises Operation & Routine Maintenance
Exercise Task
List all major operation steps concerning lube oil system with relevant set points, i.e. above 90 % shaft speed switch-off auxiliary oil pump.
Exercise Aids
•
Group Time Frame Presentation
•
Plant specific P&ID and legend to P&ID Set point list steam turbine
•
Starting and operating instructions of steam turbines
• •
Group work with max. 4 trainees per group 20 minutes
•
Group presentation in front of class
Set Point (Speed, Load, etc.)
Operation Step
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Steam Turbine Operation
ABCD
Lube Oil System
Exercises Trouble Shooting
Exercise Task
List all alarms concerning the lube oil systems as well as the possible causes of them.
Exercise Aids
•
Group Time Frame Presentation
•
Plant specific P&ID and legend to P&ID Set point list steam turbine
•
Starting and operating instructions of steam turbines
• •
Group work with max. 4 trainees per group 20 minutes
•
Group presentation in front of class
Alarm
Possible Causes
Action Required
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Steam Turbine Operation
ABCD
Lube Oil System
Exercises Routine Maintenance
Exercise Task
List all major actions required for routine maintenance of the lube oil system.
Exercise Aids
•
Plant specific P&ID and legend to P&ID
• •
Starting and operating instructions of steam turbines Maintenance description of lube oil system
•
Group work with max. 4 trainees per group
•
20 minutes
•
Group presentation in front of class Site visited with hands-on dry-exercise Group presentation in the field
Group Time Frame Presentation
Schedule
Action Required
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Steam Turbine Operation
ABCD
Lube Oil System
Test Questions for Verification of Learning Progress
General
The following points are important and shall be taken into account: The training manual may be used (open book), but first try without looking up in • the manual. Mark the box in front of each correct statement with a diagonal cross. • One or more or all statements may be correct. Use this section to verify your learning progress! Review subjects, which are not clearly understood. •
Questions:
Question 01:
The turbine lubrication system supplies oil to the following consumers: A
Question 02:
Journal and axial bearings of the steam turbine
B
Turning gear system
C
Hydraulic oil system
D
Jacking oil system
E
Sealing oil system of the generator
The temperature of the lube oil is maintained to be not less than 45° C during normal load operation of the steam turbine by the following: A
Lube oil cooler
B
Lube oil temperature control valve
C
Lube oil mass flow control through the lube oil cooler
D
Lube oil tank heater
E
Cooling water mass flow control through the lube oil cooler (Continued next page)
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Steam Turbine Operation
ABCD
Lube Oil System
Questions (continued):
Question 03:
During operation, the shaft driven main lube oil pump supplies the steam turbo set with the lube oil required. What happens if the pump fails? A
Question 04:
B
The emergency lube oil pump is automatically added into service
C
The service is switched over to the auxiliary lube oil pump
D
The steam turbine trips
E
The pressure accumulator supplies oil while the auxiliary pump is running
What happens in case of an AC loss? A
Question 05:
The auxiliary lube oil pump is immediately added into service
The pressure in the lube oil system collapses
B
The steam turbine goes into a trip
C
The emergency lube oil pump is automatically switched on
D
The emergency lube oil pump will carry the supply of the lube oil to prevent damage to the unit from lack of lube oil during shut-down
E
The pressure accumulator supplies oil while the auxiliary pump is running up
What happens when the lube oil temperature downstream of the twin filter exceeds the pre-set maximum level? A
An alarm is issued. The operator has to take the action necessary to return the unit to normal operation
B
An alarm is issued. If the temperature exceeds the pre-set max. level, the steam turbine goes into a trip
C
An alarm is issued. The operator has to investigate until the source of the problem is found
D
An alarm is issued. The operator has to investigate until the source of the problem is found and has to take the action necessary to return the unit to normal operation (Continued next page)
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Steam Turbine Operation
ABCD
Lube Oil System
Questions (continued):
Question 06:
What happens when the bearing metal temperature exceeds the pre-set maximum level? A B
The steam turbine goes into a trip Sequential initiation of an alarm and a trip of the steam turbine
C Automatic change-over to standby oil cooler
Question 07:
How Is operational readiness of the auxiliary and the emergency lube oil pump during normal operation of the steam turbine tested? A
Question 08:
The lube oil supply is switched over to the auxiliary pump
B
The auxiliary and the emergency lube oil pumps are started automatically during each FG start-up. When the pre-set pressure level after each pump is reached, it is switched off
C
The shaft driven main lube oil pump and the auxiliary or the emergency lube oil pump may be operated simultaneously, therefore the pump to be tested shall be switched-on manually for a brief time
D
TURBOTROL features a lube oil pump test program, which can be activated during operation
For how long has the FG lube oil supply to remain in operation after a shut-down of the steam turbine? A
For 72 hours
B
Until the steam turbine metal temperature is <154° C and FG turning gear can be shut-down
C
Until the FG lube oil supply is shut-off
D
Until the FG jacking oil is shut-off (Continued next page)
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Steam Turbine Operation
ABCD
Lube Oil System
Questions (continued):
Question 09:
What has to be checked specially during a "once a shift" walk down on the turbine lubrication system? A
Question 10:
Watch out for leaks because they will lead to fires where hot surfaces are present
B
Proper lube oil forward and return temperature
C
Lube oil level in the tank
D
Pressure drop across twin filter
What is important when switching over from the service to the standby side of the twin filter? A
Proper venting of the stand-by side before switchover
B
Replace the dirty filter elements with new elements
C
Discard the used elements
D Wash dirty filter elements for re-assembly E
Question 11:
Check the system for leaks after re-assembly
Define the following process parameters: A
Lube oil pressure at the inlet to the bearings:
............ barg
B
Lube oil pressure at the discharge of the shaft driven lube oil pump:
............ barg
C
Minimal lube oil temperature for steam turbine run-up:
............
D
Maximal lube oil temperature in the distribution system (alarm):
............
E
Maximal pressure drop across twin filter (alarm):
............ barg
°C °C
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ABCD
Steam Turbine Operation
Lube Oil System
Lesson Test Questions Solution Key
The correct answers for each question are as follows: 01: A, B, D 02: B, C, E 03: A, B 04: B, C, D 05: D 06: B 07: C 08: B 09: A, B, C, D 10: A, B, C, E 11: 1.5barg, 5.5 barg, > 20° C, < 70° C, 0.8 barg
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ABCD
Steam Turbine Operation
Lube Oil System
Summary The purpose of the lube oil system is to lubricate the bearings of the steam turbine and the generator. Additionally, the heat transferred to the rotor by the steam, which is conducted to the journals, is transferred to the lube oil together with the friction heat generated in the bearings. The lube oil system supplies also a variety of other systems, such as the power oil-, the jacking oil- and the turning gear system. The main lube oil pump, driven by the turbine shaft, supplies the lube oil system. The lube oil is partly passed through the lube oil cooler. The temperature is maintained by the temperature controller, which mixes the warm oil from the tank with the required amount of cooled oil. A pressure control valve maintains the system pressure under all operating conditions. The oil passes then through a twin lube oil filter, before it enters the bearings. Each bearing is equipped with an orifice, thus preventing a total pressure loss in the system in case of a system leak. An oil vapor extractor maintains a slight vacuum in the system, thus preventing oil leaks on the bearing pedestals. An auxiliary lube oil pump is required for start up, since the main lube oil pump delivers an insufficient quantity of oil during low speed operation. The auxiliary lube oil pump, together with the emergency lube oil pump, is switched on, when the lube oil pressure drops below a defined minimum. The electronic control system supervises pressure and temperature and provides the necessary alarms or actions. The lube oil system requires only little maintenance during regular operation. The operator should always check for leaks on all components involved in the system. Particular attention is required for the filter, since the filter in operation may clog up over a period of time. Severe damage results when changing-over the oil filter or oil coolers without proper filling venting!
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