Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
  • F01K7/00—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating
  • F01K7/16—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating the engines being only of turbine type
  • F01K7/165—Controlling means specially adapted therefor

Definitions

• a steam turbine is preferably used as the drive.
• the steam turbine is controlled by using a steam control valve to regulate the amount of steam supplied to the turbine, so as to guarantee the rotational speed of the turbo-com- pressor necessary for the production process.
• the steam control valves are mostly equipped with a hydraulic control system, in which the steam flow, and thus the rotational speed of the turbo-compressor, are controlled by varying the flow rate of the hydraulic liquid. Oil is often used as the hydraulic liquid.
• the present disclosure provides a method, in which a primary servo valve system is pro- vided as a main control circuit and a secondary servo valve system is provided as a backup control circuit for controlling a steam turbine, and in which the secondary servo valve system is continually kept in motion and flown through.
• a maximum and minimum pressure i.e. the end points of the range, can be measured, for example for each iteration of the cyclical movement of the servo piston. Said meas- ured maximum and minimum pressure may then be compared to the target pressure, which may be preset. If the measured pressure does not reach the target pressure, the alarm signal will be triggered.
• the first position is a discharge position of the secondary servo valve system and the second position is a supply position of the secondary servo valve system.
• the servo piston of the secondary servo valve system is continu- ously moved between the first position and the second position.
• the servo piston is moved from the first position to the second position within a first period t1.
• the servo piston is moved from the second position to the first position within a second period t2.
• tx may be t1+t2. Additionally or alternatively t1 and t2 may be equal.
• a primary control oil flow may be supplied to the primary servo valve system from an oil receptacle and may be supplied from there to an actuator via a magnetic switch valve, which actuator controls the steam supply to the steam turbine.
• a sec- ondary control oil flow may be supplied to the secondary servo valve system from an oil receptacle and is returned into the oil receptacle via the magnetic switch valve, wherein the magnetic switch valve is controlled such that the control oil flow from the secondary servo valve system is supplied to the actuator if the primary servo valve system fails.
• the alarm is triggered if the pressure in the control oil return flow does not reach the minimum and/or the maximum target pressure value within a period tz, wherein tz is equal to the sum of t1 and x and/or tz is equal to t2 and x, with x representing a freely selectable waiting period.
• the steam turbine drives a turbo-compressor in a petrochemical installation, in particular a cracker, or a generator in a power plant.
• a further subject matter of the present disclosure relates to a device for controlling a steam turbine, comprising i) an oil tank containing a control oil; ii) a primary control circuit comprising a primary servo valve system; iii) a secondary control circuit comprising a secondary servo valve system; iv) a magnetic switch valve; v) a control unit for controlling the steam flow to the steam turbine and vi) an alarm system, wherein the primary control circuit and the secondary control circuit are connected to the oil tank, wherein the primary servo valve system and the secondary servo valve system are configured to guide the control oil flow to the magnetic switch valve, wherein the magnetic switch valve is controlled such that it switches from the primary servo valve system to the secondary servo valve system if the primary servo valve system is not operational; wherein the secondary control circuit comprises a limiting orifice, a valve and a measuring unit that are arranged between the oil tank and the secondary servo valve system; wherein the measuring unit is designed to measure a
• the alarm system is triggered if the measured pressure value does not reach a maximum target pressure value and/or a minimum target pressure value.
• the alarm system is configured such that an alarm is triggered if the maximum target pressure value and/or the minimum target pressure value is not reached within a time period tz.
• the device is operated in a petrochemical installation. In particu- lar, the device may be operated in a cracker or in a power plant. [0029] The present disclosure is illustrated with reference to the following Figures which should by no means be understood as limiting the idea of the disclosure.
• FIG. 1 shows an exemplary pressure recording of the control oil return flow within the scope of the method according to the disclosure, wherein the recording shows the pressure build- up and the pressure drop which are generated by the cyclical movement of the servo piston in the secondary servo valve system.
• Figure 2 shows a schematic structure of the system according to the disclosure com- prising 1. oil reservoir 2. limiting orifice and adjusting valve 3. bearing lubrication and sealing oil system of the steam turbine and the crude gas turbo-com- pressor 4. pressure measurement secondary servo valve system 5. primary servo valve system 6. secondary servo valve system 7. switch valve 8. steam supply 9. steam control valve 10.
• a first subject matter of the present disclosure relates to a method for controlling a steam turbine, the method comprising the following steps: i) providing a primary servo valve system as a main control circuit for controlling the steam flow entering the steam turbine; ii) providing a secondary servo valve system as a backup control circuit for controlling the steam flow entering the steam turbine; wherein the servo piston of the secondary servo valve system is freely movable between a first position and a second position; iii) generating a control oil return flow from the secondary servo valve system; iv) cyclically moving the servo piston between the first position and the second position within a period tx and simultaneously sensing the pressure in the control oil return flow; v) recording the sensed pressure values while forming a maximum and a minimum pressure value; vi) triggering an alarm signal, if the measured pressure fails to reach a minimum and/or maximum target pressure.
• the method of the present disclosure keeps the secondary servo valve system, which serves as a backup in case of a failure of the primary servo valve system, is kept in motion und is constantly flown through by the control oil flow, so that a seizure of the servo piston is prevented.
• the secondary servo valve system is always operational and can take over the control of the steam turbine should the primary servo valve system fail. Costly failures of the installation and an associated production stop can be avoided in this manner.
• the maximum and minimum pressure values are measured values formed from the re- cording of the sensed pressure values.
• a primary control oil flow is supplied from an oil receptacle to the primary servo valve system from which the control oil flow is supplied on through a magnetic switch valve to an actuator that controls the steam supply to the steam turbine.
• a secondary control oil flow is supplied from the oil receptacle to the secondary servo valve system and is returned into the oil receptacle.
• the magnetic valve is controlled such that the control oil flow is supplied from the secondary servo valve system to the actuator if the primary servo valve system fails.
• a combined lubrication oil and control oil system is used, whereby obstructions of the control valve can occur, for example due to abraded material accumu- lated in the oil.
• the control oil flow is returned from an oil receptacle back into the oil receptacle through the secondary servo valve system, if the secondary servo valve system is in the backup mode.
• control oil and lubricating oil are taken from the same oil tank.
• the servo piston of the secondary servo valve system is continu- ally moved between the first position and the second position.
• This continuous movement of the servo piston causes a cleaning effect on the running surfaces of the cylinder and the piston, so that an accumulation of an accretion that would cause a blocking of the cylinder is prevented.
• the cyclical and continuous movement of the piston causes a certain heat input that prevents oil in the system from cooling, which would cause flocculation in the oil and would again result in a blocking of the system.
• the continuous movement of the servo piston causes a rising and falling pressure in the control oil return flow, which pressure can be used as a control function of the system.
• the servo piston is moved from the first position to the second position within a first period t1, and thereby a pressure change is caused in the control oil return flow.
• This pressure change may in an exemplary embodiment be monitored based on target values defined in advance.
• the servo piston is moved from the second position to the first position within a second period t2, and thereby a pressure change is caused in the control oil return flow. The pressure change thus caused can be monitored on the basis of target values defined in advance, and thus the correct functioning of the secondary servo valve system can be monitored and maintained.
• the servo piston of the secondary servo valve system may be moved cyclically from the first position to the second position and back within a period tx.
• the method according to the disclosure provides that an alarm is triggered if the pressure in the control oil return flow does not reach the defined target values.
• This alarm can be triggered with a delay in time, so that an embodiment is in which the alarm is triggered if the pressure in the control oil return flow has not reached the minimum and/or the maximum target pressure value within a period t z .
• the control oil flow is therefore returned into the oil receptacle when the servo piston of the secondary servo valve system is in the first position or between the first position and the second position.
• a regular flushing of the secondary servo valve system is achieved by this guiding of the control oil flow, so that a clogging of the valve is prevented.
• the control method according to the disclosure is characterized in particular in that it provides for an instantaneous operational readiness of the backup control circuit if the main control circuit should fail.
• the control oil flow is supplied by the second- ary servo valve system to an actuator, for example a hydraulic main steam valve, which controls the steam flow to the steam turbine.
• the secondary control circuit can assume the control of the steam turbine, without a failure of the installation occurring.
• the control system of a steam turbine generally comprises a number of control and ac- tuation units that control the steam flow supplied to the turbine.
• the servo valve systems supply the control oil flow to an actu- ator via a magnetic switch valve, the actuator operating a valve that controls the supply of the steam flow to the steam turbine. Should the primary servo valve system fail, the control oil flow can be supplied to the actuator from the secondary servo valve system via the magnetic switch valve and the control oil flow can thus be maintained.
• the method according to the disclosure can be used to control any optional steam tur- bine.
• the steam turbine drives a turbo-compressor, particularly one used in a petrochemical plant, such as a cracker.
• the steam turbine drives a generator in a power plant.
• a further subject matter of the present disclosure relates to a device for controlling a steam turbine, comprising i) an oil tank containing a control oil; ii) a primary control circuit comprising a primary servo valve system; iii) a secondary control circuit comprising a secondary servo valve system; iv) a magnetic switch valve; v) an actuator for controlling the steam flow to the steam turbine and vi) an alarm system, [0049] wherein the primary control circuit and the secondary control circuit are connected to the oil tank, wherein the primary servo valve system and the secondary servo valve system are configured to guide the control oil flow to the magnetic switch valve, wherein the magnetic switch valve is controlled such that it switches from the primary servo valve system to the secondary servo valve system if the primary servo valve system is not operational; wherein the secondary control circuit comprises a limiting orifice, a valve and a measuring unit that are arranged between the oil tank and the secondary servo valve system; wherein the measuring unit is designed to measure
• the alarm system is configured such that an alarm is trig- gered if the maximum target pressure value and/or the minimum target pressure value is not reached within a period tz. In this manner, it is provided that false alarms are caused due to non- critical delays during pressure adjustment.
• the actuator is the main steam control valve that controls the steam flow supplied to the steam turbine.
• the device according to the present disclosure is operated in a petrochemical installation, preferably a cracker, or in a power plant.
• a control oil flow is directed from a reservoir (1), from which also the oil for the bearing lubrication and the sealing oil system of the steam turbine and the crude gas turbo-compressor (3) is taken, into the control system comprising a primary servo valve system (5) and a secondary servo valve system (6).
• the control system comprising a primary servo valve system (5) and a secondary servo valve system (6).
• a first part of the control oil flow is returned into the oil reservoir (1) via the switch valve (7), wherein the pressure in this return flow is monitored using a limiting orifice and an adjusting valve (2) as well as a pressure gauge (4). Should the pressure in the secondary servo valve system (6) not reach the predetermined target values within a defined period, an alarm will be triggered.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Control Of Turbines (AREA)

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• 2022
  • 2022-05-31 EP EP22176496.2A patent/EP4286661A1/de not_active Withdrawn
• 2023
  • 2023-05-26 WO PCT/EP2023/064246 patent/WO2023232704A1/en not_active Ceased
  • 2023-05-26 EP EP23730024.9A patent/EP4532902B1/de active Active

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