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600MW supercritical condensing turbine

key word:Heat exchange element

Category:


Product description

600MW supercritical, intermediate reheat, three cylinder four exhaust steam turbine and condensing turbine

(product No.: 191, B191, 190, 192, A192)

 

1. main technical specifications (see table 34-1)

Table 34-1 main technical specifications

No. Item Parameters
1 Product number 191 B191 190 192 A192
2 Unit type 600MW supercritical, intermediate reheat, three cylinder four exhaust, condensing steam turbine 600MW supercritical, intermediate reheat, three cylinder four exhaust, condensing steam turbine 600MW supercritical, intermediate reheat, three cylinder four exhaust, condensing steam turbine 600MW supercritical, intermediate reheat, three cylinder four exhaust, condensing steam turbine 600MW supercritical, intermediate reheat, three cylinder four exhaust, condensing steam turbine
3 Turbine model N600-24.2/566/566 N600-24.2/566/566 N600-24.2/538/566 N660-24.2/566/566 N660-24.2/566/566
4 THA Operating powerMW 600 600 600 660 660
5 VWO Operating powerMW 676.6 671 676.4 739.1 694.5
6 T-MCR Operating powerMW 650.5 640.2 648.8 711.4 660
7 Rated main steam pressureMPa 24.2 24.2 24.2 24.2 24.2
8 Rated main steam temperature(℃) 566 566 538 566 566
9 Rated reheat steam inlet temperature(℃) 566 566 566 566 566
10 Rated main steam intaket/h 1661.5 1678.5 1690.5 1874.6 1975.8
11 Maximum main steam intaket/h 1913 1913 1942.3 2101.8 2096.2
12 Rated exhaust pressureKPa 4.9 5.4 4.9 4.9 10.13
13 Design cooling water temperature(℃) 20 21.5 20 20 32
14 Rated feed water temperature(℃) 274.1 275 275 276 280.9
15 Rated speedr/min 3000 3000 3000 3000 3000
16 Rotation direction (from turbine to generator) Clockwise Clockwise Clockwise Clockwise Clockwise
17 Form of regulation and control system DEH DEH DEH DEH DEH
18 Feed water regenerative stage (HP heater + deaerator + LP heater) 83+1+4 83+1+4 83+1+4 83+1+4 83+1+4
19 Flow passage stages (regulating stage + high pressure + medium pressure + low pressure) 481+11+8+4×7 481+11+8+4×7 481+11+8+4×7 481+11+8+4×7 481+11+8+4×7
20 Length of last stage blade of low pressure cylindermm 1050 905 1050 1050 905
21 THA heat consumptionKJ/(KW·h)
22 Unit dimensionsL×W×H 27500×11500×7930 27500×11500×7930 27200×11500×7930 27500×11500×7930 27500×11500×7930
mm×mm×mm
23 Weight of  steam turbine bodyt Appa. 950 Appa. 950 Appa. 950 Appa. 950 Appa. 950
24 Elevation of turbine center running floormm 1067 1067 1067 1067 1067
25 Steam distribution mode Nozzle + throttle Nozzle + throttle Nozzle + throttle Nozzle + throttle Nozzle + throttle
26 Steam distribution mode Constant pressure - sliding pressure - constant pressure Constant pressure - sliding pressure - constant pressure Constant pressure - sliding pressure - constant pressure Constant pressure - sliding pressure - constant pressure Constant pressure - sliding pressure - constant pressure
27 Operation mode Combined start of high and medium pressure Combined start of high and medium pressure Combined start of high and medium pressure Combined start of high and medium pressure Combined start of high and medium pressure

Note: the height in the overall dimension of steam turbine refers to the height from the operating floor to the highest point of the equipment.

 

2. Structural features and main systems

The steam turbine is a new type of supercritical, single shaft, one intermediate reheat, three cylinder four exhaust, condensing steam turbine. The high and medium pressure part adopts the cylinder closing structure. The high-pressure flow passage adopts efficient downstream arrangement, which is opposite to the medium pressure flow passage; the low-pressure flow passage adopts double reverse arrangement. The control system adopts digital electro-hydraulic control system, which is easy to operate, safe and reliable.

The main steam from the boiler reaches the main steam valves and control valves on both sides of the turbine through two main steam pipes, and enters the steam chamber in the high pressure cylinder through four flexible steam pipes. Four steam pipes are symmetrically connected to two steam inlet pipe interfaces of upper and lower half of HP and IP outer cylinder.

The high pressure flow passage is composed of one single regulating stage (impulse type) and 11 pressure stages (reaction type). The high pressure nozzle group is installed in the steam chamber, the 11 stage diaphragms are installed on the high pressure diaphragm sleeve, and the high pressure diaphragm sleeve is supported by the cylinder. The main steam entering the steam chamber first enters the regulating stage, and then flows through each pressure stage of the high pressure cylinder.

The steam is extracted from the steam extraction port of section 1 after the ninth stage of high pressure cylinder to No. 1 high pressure heater. The exhaust steam of HP cylinder is discharged from the lower part of HP and IP outer cylinder and returns to Reheater of boiler after passing through reheat cold section steam pipe. Part of the steam is extracted from the steam extraction port of section 2 to the No. 2 high pressure heater. The reheated steam is connected to the reheating valves on both sides of the intermediate pressure steam cylinder through the reheating valves on both sides of the intermediate pressure steam cylinder, and then goes to the reheating valves on both sides of the main steam cylinder through the reheating pipes.

The middle pressure flow passage adopts reaction pressure stage, which is divided into 8 stages and 2 parts. Among them, the intermediate pressure 1st ~ 5th stage diaphragms are installed on the intermediate pressure 1st diaphragms sleeve, and the intermediate pressure 6th ~ 8th stage diaphragms are installed on the intermediate pressure 2nd diaphragms sleeve; the intermediate pressure 1st diaphragms sleeve is supported by the intermediate pressure inner cylinder, and the intermediate pressure 2nd diaphragms sleeve is supported by the intermediate pressure outer cylinder.

A part of the steam from the fifth stage of the intermediate pressure cylinder is extracted to the No. 3 high pressure heater through the 3-stage extraction port in the lower half of the high and medium pressure outer cylinder. There are two four section steam extraction ports at the lower part of the exhaust end of the intermediate pressure cylinder, through which part of the steam is pumped to the deaerator, feed pump turbine, etc.

The steam from the middle and low pressure cylinders is led to the middle of the two low-pressure cylinders through two medium and low pressure connecting pipes.

The low pressure flow passage adopts double flow reaction pressure stage, which is 2 × 2 × 7. The steam enters from the middle of the low pressure cylinder, then flows to the exhaust port of the two rocks respectively and enters the lower condenser. Because of symmetrical double flow, the low pressure rotor has little axial force. The length of last stage blade is 1050mm or 905mm.

This turbine belongs to the reverse turbine, so the axial thrust at all levels is large. In order to reduce the axial thrust, in addition to the design of the high and medium pressure flow passage part into reverse arrangement and the low-pressure flow passage part as double flow arrangement, the balance piston is adopted in the rotor structure, which greatly reduces the axial thrust, and the remaining axial thrust is borne by the thrust bearing. The thrust bearing is arranged between No. 2 radial bearing and No. 3 radial bearing, and the relative dead point of rotor is formed at the thrust bearing.

Differential expansion indicator is installed in the bearing box at the front bearing box and the electric end of No. 2 low-pressure cylinder to monitor the differential expansion state of the unit. Both the high and medium pressure cylinder and the low pressure cylinder are double-layer cylinders.

The dead point of the stator of the turbine is located in the center of No. 1 low pressure cylinder, which is the intersection of the center line of the fixed plate in axial and transverse position. The support foot of the low pressure cylinder is freely placed on the base plate of the low-pressure cylinder to ensure its free expansion in an anisotropic way.

The front bearing seat is freely placed on the front bearing pedestal foundation plate. Due to the limitation of longitudinal guide key between front bearing pedestal and plate, the front bearing pedestal can only slide along the axial centerline of turbine on the plate. Two pressing plates on both sides of the front bearing pedestal press the front bearing pedestal to prevent it from beating.

The H-shaped fixed center beam is arranged at both ends of the high and medium pressure outer cylinder. It is connected with the front bearing pedestal and the bearing box of No. 1 low-pressure outer cylinder (governor end, referred to as regulating end), which plays a push-pull role when the cylinder expands and contracts, and also ensures that the center of the cylinder and the shaft system is not changed.

Each rotor is supported by two radial bearings.

The thrust bearing adopts the self position type, which can automatically adjust the load of the thrust pad, and has good stability. In addition, the clearance of thrust bearing can be measured and adjusted by the positioning mechanism of the thrust bearing shell.

The rigid coupling is used to connect the rotors. The coupling is equipped with gasket, and the axial position of rotor can be adjusted during installation.

The low-pressure rotor and generator rotor are also connected by rigid coupling. The large gear for turning is installed at the generator end of No. 2 low-voltage rotor (electric terminal). The gear also acts as coupling gasket to adjust the axial position of turbine rotor and generator rotor.

Turning device can be manually or automatically put into continuous turning, and can be automatically disengaged after the impulse.

Figure 34-1, figure 34-2 and figure 34-3 show the longitudinal section, side view and top view of the model respectively.

 

2.1. cylinder

2.1.1. the outer cylinder of high and medium pressure and high pressure outer cylinder adopts molybdenite steel casting, which is separated at the middle split surface to form the upper and lower half. The cylinder is equipped with 4 high-pressure steam inlet, two upper and lower half respectively, which are connected with the outlet of regulating valve through 4 flexible pipes. Steam is supplied to the high-pressure cylinder from flexible pipe welded to the steam inlet. Two high pressure exhaust ports are set at the lower part of the regulating end of the high and medium pressure outer cylinder. The cylinder is equipped with 4 medium pressure steam inlet, two for the upper and lower half, and connected with the outlet of reheat regulating valve through 4 flexible pipes. The reheat steam enters the middle pressure cylinder from the flexible pipe welded to the steam inlet. Two intermediate pressure exhaust ports are located at the upper part of the electric end of the high and medium pressure outer cylinder, and the intermediate pressure exhaust steam is introduced into two low-pressure cylinders respectively through two connecting pipes. The cylinder is equipped with No. 1, 3 and 4 Extraction ports, which are all located in the lower half of the cylinder. The No. 2 extraction is led out by high exhaust. The extraction of these vents is provided for heaters and deaerator at all levels.

The high and medium pressure outer cylinder is equipped with high pressure, medium pressure inner cylinder and high pressure and medium pressure holding ring. The end steam seal is installed at the wall of both ends to prevent leakage of steam. The two ends of the cylinder are also provided with openings for installing balance plugs in the field dynamic balance.

The high and medium pressure outer cylinder is supported by four cat claws which are cast into one with the end of the lower cylinder. At the electric end, these claws are supported on the support keys of the lower half bearing pedestal of the low-pressure outer cylinder regulating end, and can slide freely on the support keys. At the adjusting end, the cylinder cat claw is also supported on the support key of the front bearing seat and can slide freely. At each end, a H-shaped centering beam and bolts and locating pins are used to connect the cylinder and the adjacent bearing pedestal. These beams keep the cylinder in the correct axial and transverse position relative to the bearing housing. Any tendency of the cylinder to leave the bearing pedestal is limited by the studs on each cat's claw. These bolts are assembled with enough clearance around and under the nuts so that the cylinder claws can move freely with the temperature.

The advantage of the structure of the cat claw with the lower half cylinder upside down is to eliminate the influence of the quality of the lower half cylinder, the quality of the insulation layer and the pipe force on the split bolt in the cylinder, thus reducing the bolt stress and ensuring the steam tightness of the middle split surface.

The horizontal and middle split surface of the high and medium pressure outer cylinder is connected with big stud bolts. They must be pre tightened to produce appropriate stress to ensure the steam tightness of the middle split surface. The cylinder surface is finished, which can keep close fit when the surface is dry and in contact with metal, and when carrying out standard hydrostatic test. Flaxseed oil shall be applied to the joint surface for three boiling times during field installation. There are also several thermocouple measuring points on the high and medium pressure outer cylinder to measure the metal and steam temperature of the cylinder to control the start-up and operation monitoring; the thermocouple upper and lower cylinders for monitoring the water inflow of the cylinder are set in pairs. When the cylinder is in water, the temperature difference of the upper and lower cylinders will change (the temperature of the lower cylinder suddenly decreases). If the value exceeds a certain value, the unit will alarm or trip to prevent damage to the rotor and blade.

2.1.2. High pressure inner cylinder. The high pressure inner cylinder is made of molybdenum steel casting, which is separated at the split surface to form the upper half and the lower half. The upper and lower half are connected and fixed with flange bolts, and must be pre tightened to produce appropriate stress, so as to ensure the steam tightness of the split.

The high pressure inner cylinder is supported on the horizontal split of the high and medium pressure outer cylinder by the supporting key fixed on the lower half cylinder, and the upper gasket restricts its upward movement, so as to ensure the horizontal position of the high pressure inner cylinder. The axial positioning is achieved through the shoulder fit, and the lateral positioning is achieved by using the center positioning pin at the top and bottom with the high and medium pressure outer cylinder, which can not only ensure the correct position of the inner cylinder axis, but also allow free expansion.

The steam chamber is installed in the high pressure inner cylinder. The axial direction of the steam chamber and the high pressure inner cylinder is realized by the cooperation of the shoulder. The transverse positioning is realized by the boss of the upper and lower half of the steam chamber stuck on the inner cylinder, and the position can be adjusted by the gasket. There is a sealing ring between the HP inner cylinder and the inlet of the steam chamber to prevent steam leakage.

The steam inlets of the inner and outer cylinders are connected by flexible steam inlet pipes. The steam inlet pipe is welded on the interface of high and medium pressure outer cylinder to absorb differential expansion of inner and outer cylinder and reduce thermal stress; a sealing ring is provided between the steam inlet pipe and the steam inlet of inner cylinder.

A metal temperature measuring point is set on the high pressure inner cylinder. The measured metal temperature of the inner cylinder is used to replace the first stage temperature of the high pressure rotor. The temperature difference between metal and steam is compared with the preset value, so as to control the start-up and load change of the steam turbine, so as to limit the thermal stress of the rotor.

There is a drain hole at the bottom of the lower half of the high-pressure inner cylinder, which is led out through the high and medium pressure outer cylinder through the drain pipe to drain the water in the steam inlet chamber of the high-pressure inner cylinder.

2.1.3. Intermediate pressure inner cylinder. The middle pressure inner cylinder is made of Cr Mo steel, which is separated at the split surface to form the upper half and the lower half. The upper and lower half are connected and fixed with flange bolts, and must be pre tightened to produce appropriate stress, so as to ensure the steam tightness of the split.

The IP inner cylinder is equipped with IP side balance piston steam seal and IP No.1 diaphragm sleeve. The cylinder is supported on the horizontal split of HP and IP outer cylinder by the supporting key fixed on the lower half cylinder, and the upper gasket is used to limit its upward movement, so as to ensure the horizontal position of HP inner cylinder. The axial positioning is achieved through the shoulder fit, and the lateral positioning is achieved by using the center positioning pin at the top and bottom with the high and medium pressure outer cylinder, which can not only ensure the correct position of the inner cylinder axis, but also allow free expansion.

The steam inlets of the inner and outer cylinders are connected by flexible steam inlet pipes. The steam inlet pipe is welded on the interface of high and medium pressure outer cylinder to absorb differential expansion of inner and outer cylinders and reduce thermal stress; a sealing ring is provided between the steam inlet pipe and the steam inlet of inner cylinder.

2.1.4. Low pressure outer cylinder. There are two low-pressure cylinders in this model, i.e. No.1 and No.2 low-pressure cylinders. The low-pressure cylinders are connected by push-pull bolts to ensure concentricity and heat expansion.

The LP outer cylinder provides the passage for the exhaust steam to the condenser and transfers the reaction torque to the foundation. The low-pressure outer cylinder must also bear the structural load of all the components installed on the outer cylinder and bear the vacuum load, so it is designed to have enough rigidity to prevent excessive deformation from affecting the clearance between the dynamic and static parts.

The LP outer casing is a large welded structure of carbon steel plate, which is the largest component in the turbine body. In order to reduce its mass and ensure its stiffness under vacuum conditions, the upper half adopts the thin-walled vault composed of large and small arcs, and the end wall is welded with supporting tubes; the lower half is a rectangular frame structure composed of end wall and side wall, which is strengthened by continuous supporting legs around near the split plane, and at the exhaust interface, reinforcing ribs and supporting tubes are welded along the longitudinal and transverse direction to enhance its rigidity.

Because the temperature of the low pressure outer cylinder is low, the center change caused by differential expansion is small, so the non split support mode is adopted. The bearing seat and the outer cylinder are made into a whole, and the bearing seat and the surrounding continuous feet are supported on the base plate together.

Due to the limitation of processing and transportation conditions, two vertical split planes are added to the large low pressure outer cylinder, which divides the outer cylinder into three upper half and three lower half respectively. After assembly in the manufacturer, the outer cylinder is disassembled and shipped, and then assembled and fastened after arriving at the power plant site.

The sliding pin system of the unit is formed by the matching of the longitudinal notch and transverse square hole on the base plate of the pedestal with the centering element poured into the foundation. An H-shaped centering beam is set between the adjusting end bearing seat of No.1 LP outer cylinder and the HP / IP cylinder, and push rod and pull rod are set on both sides between the two LP cylinders to connect the expansion of each cylinder along the axial direction.

The bearing pedestal of the low pressure part is connected with the low pressure cylinder. This structural feature determines that during the operation of the unit, the bearing elevation in the low pressure bearing pedestal will change with the deformation of the low pressure cylinder caused by the change of straight air. Therefore, in order to ensure stable operation and maintain good vibration quality, the exhaust vacuum should be kept within the specified range.

Lift the upper half of the outer cylinder to repair the inner part of the low pressure cylinder: a ladder is welded on the side wall of the inner cavity in the lower half of the outer cylinder to facilitate personnel to enter for installation and maintenance. The upper half of the outer cylinder has 4 holes, 2 at each end, which can be accessed for internal inspection without opening the cylinder. Two exhaust diaphragm valves are located on the top of the upper half of the outer cylinder. During normal operation, the cover plate of the valve is compressed by atmospheric pressure. When the vacuum of the condenser is damaged and overpressured, the steam can break the cover plate, tear the lead diaphragm and discharge to the atmosphere.

Each LP outer cylinder is equipped with inner cylinder (1), retaining ring (2), heat shield of LP inner cylinder, inlet guide ring, exhaust guide ring, etc. The end steam seal is installed at the end wall of the outer cylinder. The steam supply system of the steam seal delivers the steam with stable pressure to both ends for sealing, and the exhaust steam of the steam seal is sent to the steam seal cooler.

A window is set on the end wall above the flange face of the steam seal of the upper half cylinder for installing the screw plug when the rotor is dynamically balanced on site.

No.3 bearing is installed on the adjusting end bearing box of No.1 low pressure outer cylinder, and No.2 bearing of high and medium pressure is installed at the same time; No.6 bearing and relative expansion measuring device are installed on the electric end bearing box of No.2 low pressure outer cylinder.

2.1.5. Low pressure inner cylinder. The low pressure inner cylinder is of carbon steel welding (cast welding) structure, except that the half rings at both ends are castings, the rest are steel plates. Side plates are used to divide the inner cylinder into different extraction chambers, and struts are welded between the two side plates to ensure the rigidity of the structure.

The upper and lower half of the low pressure inner cylinder are fastened with bolts. Windows are set on both sides of the outer circle of the upper half for tightening the bolts of the inner split. After assembly, they are sealed with cover plates. The low pressure inner cylinder is supported on the boss on the lower half of the outer cylinder by the convex edges on both sides of the flange with the help of the lower half of the split, and the stainless steel gasket is added in the middle, and the transverse position along the steam inlet centerline is the mortise and groove matching positioning; the inner cylinder and the top steam inlet of the outer cylinder are positioned by four mortise and groove matching, and the adjusting gasket is set; The eccentric sleeve locating pin is set at the vertical center of the steam inlet center line at the bottom of the inner cylinder, which is welded after field assembly.

The steam inlet of LP inner cylinder constitutes the high temperature region of LP cylinder. The heat shield of low pressure inner cylinder is fixed with bolts on the outer wall of inner cylinder to reduce the temperature difference and heat loss of cylinder wall and the temperature of outer cylinder. A steam guide ring is installed in the middle of the inner cylinder, which forms the steam inlet channel and protects the rotor from direct steam flow erosion

There is a circular window on the upper half of the LP inner cylinder, which matches the steam inlet of the LP outer cylinder. The rings at both ends of the inner cylinder are equipped with symmetrical stage 6 ~ 7 diaphragms, and two retaining rings are installed in the middle. There are four extraction ports at the bottom of the lower half, which are after stage 2, 5 and 6 of No. 1 low pressure cylinder and after stage 4 ~ 6 of No. 2 low pressure cylinder. The second stage of No.1 LP cylinder is extracted to No.5 LP heater, the fourth stage of No.2 LP cylinder is extracted to No.6 LP heater, the fifth stage is extracted to No.7 LP heater, and the sixth stage is extracted to No.8 LP heater.

Exhaust guide rings are fixed at both ends of the inner cylinder, which are combined with the conical end wall of the outer cylinder to form the exhaust diffuser. With the help of pressure expansion, the exhaust speed of the last stage blade can be fully utilized to convert the speed energy into pressure energy, so as to improve the efficiency of the steam turbine. When the speed reaches 2600r / min, the water spray will be put into operation automatically until the unit is loaded by 15%.

The steam inlet part of the low pressure inner cylinder is connected with the low pressure steam inlet pipe through the connecting pipe joint, and its section gradually changes from waist circle to circle. The steam inlet of the inner cylinder is aligned with the inner cylinder, and the connecting pipe joint is aligned with the outer cylinder. The vertical mortise is used for matching, and the gasket is used for adjustment during installation. The connecting pipe joints passing through the inner cylinder and the outer cylinder are connected by expansion and contraction joints welded by stainless steel sheet to compensate the differential expansion between them.

2.2. Rotor

2.2.1. High and medium pressure rotor. The high and medium pressure rotor is a non center hole rotor made of integral alloy steel forgings. The maximum stress in the center of the rotor without center hole is low, so the life of the rotor can be prolonged and the start-up time can be shortened by canceling the medium speed warm-up.

High speed dynamic balance and overspeed test are carried out after rotor manufacturing. Screw holes are set on both ends of the rotor disk surface and in the middle of the rotor, which are used to add balance plug to compensate the unbalance of the rotor. The high-speed dynamic balancing and overspeed tests are carried out on the high-speed dynamic balancing machine in the vacuum chamber of the manufacturer. In consideration of the need for balancing in the power plant due to the replacement of rotor parts or other reasons, the rotor is also equipped with screw holes for field balancing.

The high and medium pressure of the HP and IP rotors are arranged in reverse flow; the HP and IP rotors are supported on two radial bearings with a span of 6140mm, and the mass of the HP and IP rotors with blades is about 35t. The high pressure consists of a single regulating stage with three Trident pin root and 11 pressure stages. The first four stages of the pressure stage are double T-shaped roots, and the rest are T-shaped roots. There are 8 stages of medium pressure, with high-strength fir tree blade root. There are a series of high and low cogging on the outer circle of the rotor between the discs to install the diaphragm steam seal; radial steam seals are installed at the shroud of the rotor blades at all levels, and there are groups of high and low cogging on both ends of the rotor to install the steam seal, so as to prevent steam leakage and steam leakage between all levels.

The adjusting end of high and medium pressure rotor is rigidly connected with the rotor extension shaft. The rotor extension shaft is equipped with a main oil pump wheel and connected with the emergency governor small shaft. The generator end of high and medium pressure rotor and the regulating end of No.1 low pressure rotor are rigidly connected by a coupling integrated with the rotor with bolts to form a rigid coupling connection. The coupling transmits torque, axial thrust, transverse shear load and bending moment. The two rotors are equipped with gaskets, and the coupling flange is matched with the gasket notch to achieve the function of centering. By changing the thickness of the coupling gasket, the axial relative position of each rotor can be adjusted to ensure the required dynamic and static clearance. In order to remove the gasket, the rotor must move axially to separate the two coupling halves between adjacent rotors until the locating flange is detached. Therefore, the jacking screw holes are set in the two coupling halves.

2.2.2. Low pressure rotor. There are two LP rotors in this model, No.1 and No.2 LP rotors respectively. The intermediate shaft is set between the two rotors, and both ends of the intermediate shaft are respectively connected with the two low-pressure rotors by coupling.

The low pressure rotor is made of whole alloy steel forgings without center hole. Like the high and medium pressure rotors, the low-pressure rotors should also be subject to high-speed dynamic balance and overspeed test after processing and assembly, so as to eliminate the unbalance factors that cause running vibration as far as possible. The LP rotor can also be balanced directly on site.

The low pressure rotor is a double flow symmetrical structure, which ensures the axial thrust balance of the flow passage. Each rotor is supported on two radial bearings with a span of 5740mm.

The low pressure rotor is double flow 7-Stage. The first five stages are drum type, and the last two stages are disc type, which can effectively reduce the rotor mass. A side mounted fir tree shaped blade root groove is machined on the flange, which has a large bearing capacity. Diaphragm steam seal is installed between each stage. A shroud seal is installed at the top of the first four stage rotor blades, and a steam seal is also installed at the top of the fifth and sixth stage free blades of low pressure, which will obviously reduce the leakage at the top of the rotor blades. In addition, LP cylinder end steam seals are installed at the shaft shoulders at both ends of the rotor to prevent air leakage into the exhaust chamber and into the condenser.

The screw plug on the outside of the last stage is used for balancing

There are couplings at both ends of the low pressure rotor, which are integrated with the rotor. The regulating end of No.1 low-pressure rotor is connected with the high and medium pressure rotor, the generator end is connected with the intermediate shaft, the regulating end of No.2 low-pressure rotor is connected with the intermediate shaft, and the electric end is connected with the generator rotor. All connections are rigid. A barring gear is installed between the two couplings of No.2 low-pressure rotor and generator rotor, which is used as coupling gasket to adjust the relative position of low-pressure rotor and generator rotor to ensure the required dynamic and static clearance.

2.3. Valves

2.3.1. Main steam valve. The main steam valve is arranged horizontally, which minimizes the total angle of steam turning.

The main steam valve is opened by hydraulic pressure and closed by spring. At any time, the compression spring has a closing force acting on the valve. The main steam valve has two functions: ① to close the valve in emergency; ② to control the speed of the steam turbine when the steam turbine is started. Because there is a small start-up valve in the main valve of the main steam valve, which can be opened under full pressure, its flow capacity is about 25% of the rated steam flow, and it can accurately control the speed when the control valve is fully opened for full cycle steam admission start-up. The main valve disc of the main steam valve is non-equilibrium type. When the load or speed control is switched to the control of the control valve and the main steam valve needs to be fully opened, the rear control valve needs to be closed to a certain extent, that is, the pressure difference between the front and back of the main valve disc of the main steam valve is reduced to a certain extent before the main valve disc of the main steam valve can be opened. When the main steam valve is in the fully open and fully closed position, the valve stem has a self sealing device to reduce the steam leakage of the valve stem. The valve outline is shown in figure 34-4.

A permanent filter screen is welded on the valve cover of main steam valve. During trial operation, a detailed temporary filter screen shall be added on the permanent filter screen and removed after a certain period of operation.

In order to ensure the reliability of valve action, the main steam valve is required to conduct valve action test once a week.

2.3.2. Control valve. There are four control valves in the unit, and the valve shell is integrated with the main steam valve shell. The four control valves are arranged vertically, each controlled by a hydraulic motor, which is directly installed on the upper part. According to the response of the control signal of the electro-hydraulic control system, the position of the valve is given by the hydraulic servo motor. During operation, the steam pressure of the control valve is close to that of the main steam.

The valve disc is made of two pieces. The valve head is loose on the valve stem, so as to form a flexible connection with the valve stem, which can ensure the correct alignment of the valve disc. The valve disc is a partially balanced type, which requires little lifting force. The regulating valve is opened by hydraulic pressure and closed by spring. When the piston of hydraulic motor moves upward, the regulating valve will be opened, and when it moves downward, it will be closed.

The closing force produced by the compression spring always acts on each regulating valve, and the force of these springs acts downward on the spring seat to overcome the steam imbalance force generated on the valve when the valve is fully opened but the back "sits".

The steam seal of the valve stem is composed of a close fitting sleeve inserted into the valve cover and fixed in a proper position by the regulating valve cover. The sleeve has two steam leakage interfaces: the high-pressure steam leakage interface is connected to a lower pressure area, and the low-pressure steam leakage interface is connected to the steam seal cooler (commonly known as the steam seal heater).

The function of the control valve is to precisely regulate the speed and load of the steam turbine by controlling the steam flow.

In order to ensure the reliability of valve action, the valve action test is required once a week.

2.3.3. Reheat main steam valve. The reheat main steam valve is an unbalanced rocker valve. When it is fully opened, the valve disc is placed on the steam flow channel, so the loss of fluid resistance is very small; when it is fully closed, the steam flow acts on the valve disc with full pressure difference, so as to ensure the tightness of the valve.

The valve consists of a disc suspended from the shaft by a rocker arm. The shaft is connected with the piston rod through the connecting rod. The connecting rod is designed to open the valve to the full open position when the piston of the hydraulic motor moves upward, and to the closed position when the piston moves downward. At any time, the compression spring has a closing force acting on the valve. The contact surface between the rocker arm, disc and nut of the valve is spherical, and there is clearance to allow rotation. The sealing surface of the valve disc is spherical, and the valve seat is annular. When the valve disc closes and contacts with the valve seat, the movable connection between the valve disc and the rocker arm enables the valve to be correctly positioned, so as to ensure the complete coincidence of the sealing surface; when the valve disc is fully opened, the center rod of the valve disc contacts with the valve cover stop, so as to prevent the valve disc from shaking under steam flow.

The disc is an equal thickness ball cover with a center rod. The spherical surface has high bearing capacity. During assembly, the center rod passes through the rocker arm hole and is locked and limited by the nut. The contact surface between the rocker arm, disc and nut is spherical, and there is a gap to allow rotation. The sealing surface of the valve disc is spherical, and the valve seat is annular. When the valve disc is in contact with the valve seat, the movable connection between the valve disc and the rocker arm enables the valve disc to be in place correctly, so as to ensure that the sealing surface is completely consistent; when the valve is fully opened, the center rod of the valve is in contact with the valve cover stop, and the torque of the operating mechanism is used to tighten it, so as to prevent the valve disc from shaking under steam flow.

The rotating shaft is supported on the nitriding sleeve of the bearing cover and the crank case. The pressure seal type bush of the spherical base can limit the axial movement and form a seal to eliminate the steam leakage of the shaft. When opening and closing the reheat main steam valve, use the steam relief valve (unloading valve) to release the steam pressure at the pressure steam seal, so as to reduce the wear and resistance of the spherical base.

There are external bypass orifices in front of and behind the bottom disc of reheat main steam valve, whose flow is lower than the no-load flow of rated speed. Through this external bypass orifice, the pressure in front of and behind the disc (rocker) can be balanced, so as to ensure that the valve can be opened under test. If the valve needs to be opened, the steam pressure on both sides of the disc can be balanced. The hydraulic motor of reheat main steam valve is controlled by high pressure fire-resistant oil. The pressure oil pushes the piston, turns the rocker arm and opens the valve disc. In case of emergency, the pressure oil is discharged, and the valve is closed quickly by means of spring force and steam pressure. When the valve disc closes and approaches the valve seat, the buffer head of the piston of the hydraulic motor enters the oil drain hole, which inhibits the outflow of oil and increases the pressure, thus slowing down the closing speed of the valve. During assembly, measure the clearance between the piston rod and the end of the piston rod, and register the gasket, so as to make the valve disc seat and connect with the lever mechanism

In this case, the piston is in the proper position in the buffer.

One end of the shaft of the reheat main steam valve is equipped with an oil pressure operated oil operated shut-off valve to release the unbalanced steam force acting on the inner end face of the shaft when the reheat main steam valve is closed.

The valve consists of an operating valve and a hydraulic motor. The hydraulic servo motor is connected to the hydraulic system. Under normal operation, the reheat main steam valve will be in the open state, while the trip valve of the hydraulic servo motor will be in the closed state. The shaft is pressed against the thrust washer under steam force to keep its seal and prevent leakage. When the overspeed trip mechanism acts, the oil operated trip valve is opened with the aid of safety oil to connect the shaft end chamber with a low pressure, so as to reduce the steam pressure acting on the shaft end, so that the reheat main steam valve can be quickly closed with minimum force. Figure 34-5 shows the profile of reheat main steam valve.

2.3.4. Reheat control valve. The unit adopts 4 reheat control valves (2 on each reheat main steam valve), which are arranged vertically. The valve shell and reheat main steam valve shell are welded as a whole, and each is controlled by a control hydraulic motor. The reheat control valve is a balanced plunger single seat valve, which is opened by hydraulic pressure and closed by the pressure of spring group. Figure 34-6 shows a sectional view of the reheat control valve.

There are spiral grooves on the valve stem, which are matched with the nitriding sleeve to reduce the leakage of high-pressure steam. In order to avoid leakage, the leakage steam from the valve stem is led into the steam seal heater through the leakage pipe on the valve cover. The sleeve is tightly matched with the valve cover and fixed by punching and riveting.

When the valve is closed, the stem flange contacts the bottom surface of the sleeve to form a self sealing to prevent steam leakage along the stem when fully open.

The round and simple permanent forged steel filter screen surrounds the reheat control valve to prevent foreign matters from entering into the steam turbine and causing accidents. The lower end of the filter screen is embedded in the groove on the valve shell, and the upper end is compressed by the valve cover. When installing the filter screen, the non drilling part must be directly aligned with the baffle on the valve shell, and the baffle is 180 ° away from the steam inlet center. It will be separated from the two sides of the steam, so as to avoid collision vortex. During the initial start-up and operation, an additional fine temporary filter screen is used, and the temporary filter screen is removed after a period of operation.

An auxiliary valve is formed on the valve stem. When the main valve disc is in the fully open position, the auxiliary valve is located on the sleeve (usually referred to as the reverse seat). This arrangement forms a limit in the opening direction and minimizes the steam leakage along the valve stem.

The valve disc moves in the valve cover, and the valve cover is provided with a bushing. A piston ring is installed in the circumferential groove of the valve disc to minimize the steam leakage around the valve disc and maintain the low pressure in the cavity to achieve good balance effect; the steam leakage is discharged into a low pressure area through the steam leakage hole of the valve cover.

2.4. Sliding pin system

The unit is of single shaft and three cylinder structure, with one high and medium pressure cylinder and two double flow low pressure cylinders arranged in axial series. The front end of the high and medium pressure cylinder is the front bearing block, and the front and rear ends of the two low pressure outer cylinders are the bearing blocks connected with the low pressure outer cylinder. There are I notches on the front, rear, left and right center lines of No.1 LP outer cylinder, which are respectively matched with the transverse positioning plate and the radial positioning plate. The lateral positioning plate guides the axial expansion of the low pressure outer cylinder to keep the center unchanged, and the axial positioning plate guides the lateral expansion of the low he outer cylinder. Therefore, a point in the exhaust center of No. 1 LP cylinder constitutes the expansion dead point of the stator. The horizontal and axial positioning plates of LP cylinder are fixed in the foundation. During the field installation, the L-shaped gasket between the notch and the positioning plate can be corrected to ensure the correct positioning and proper expansion clearance of the low pressure outer cylinder. Figure 34-7 shows the thermal expansion trend of the rotor and stator parts in the sliding pin system of the unit.

2.5. lubricating oil system

The turbine lubricating oil system mainly provides lubricating oil to the generator bearing, thrust bearing and turning gear of the turbine, and provides working medium for the action of the mechanical overspeed trip device. For hydrogen cooled generators, the lubricating oil system also supplies two sealing oil sources of the hydrogen seal oil system. The system is equipped with reliable main oil supply equipment and auxiliary oil supply equipment, which can meet all oil consumption of steam turbine generator set under turning, starting, stopping, normal operation and accident conditions

The main components of the lubricating oil system include lubricating oil tank and accessories, main oil pump, oil injector, auxiliary oil pump, jacking oil system, oil cooler, lubricating oil pipeline and accessories. See figure 34-8 for lubricating oil system of the unit.

2.6. control system

The turbine control system is composed of the regulating system and the security system. The regulating system is the main link of turbine control, which controls the start-up and stop, speed rise, load and power plant coordinated control, and collects the operation information of various steam turbines to show the operation status of the turbine; The security system is an important part of the protection of the turbine. It monitors all the parameters of the turbine which are harmful to the safe operation, and protects the safe and reliable operation of the turbine. When the monitored parameters exceed the limit, the steam inlet valve of the turbine is closed urgently to shut down the turbine.

2.6.1 digital electro-hydraulic control system (DEH). Digital electrohydraulic control system (DEH) is the most important part of the regulation system and the brain of the whole regulation system. It collects all the turbine operating parameters, and then sends out control instructions after logic judgment and data calculation. DEH is mainly composed of operator station, engineer station, control processor, I / O input / output module, valve position drive card, power component, communication interface and other electronic hardware.

Because of the large number of electronic products manufacturers, DEH has many hardware types. At present, DEH has been put into use with the ovation of Westinghouse company, I/A's of Foxboro, T3000 of Siemens, Symphony of ABB, MAXDNA of Shanghai autometer Co., Ltd.

2.6.1.1. Briefly, DEH transmits a large amount of steam turbine information to the control processor through data acquisition of primary instruments on site, such as magnetoresistance transmitter collecting turbine speed, pressure switch collecting pressure signal, stroke transmitter collecting hydraulic motor lift, thermal resistance, thermocouple collecting temperature, etc. The proportional integral closed-loop control is applied to adjust the opening of the control valve, so that the speed and load of the steam turbine can be controlled reliably and accurately according to the requirements. The operator can control and monitor the operation of steam turbine through the display of DEH.

The hardware of DEH system can be divided into DPU (control processor) and operator / engineer station. Each DPU can be independent of the data highway. Random access memory (RAM) contains DPU application software. The application software in DPU is written in the form of control algorithm, which is similar to the functional block diagram and is safe and transparent. This program enables control engineers to modify the program easily to meet different requirements. As the main interface between the operator and the system, the operator station is controlled by standard keyboard and mouse, and can obtain operation data and information on CRT. When the system gives an alarm, the alarm data and information can be printed and recorded, as shown in figure 34-9.

The operator / engineer station is loaded with various database files supporting the system and charts of each station on the expressway. The power plant staff can obtain the application program to operate and control the steam turbine, copy it and store it on the hard disk and software, and modify or delete the program if necessary. Similarly, user graphics can also be modified, deleted or created on demand.

2.6.1.2. Main circuit of DEH control system. DEH control system is mainly composed of steam turbine state control circuit, speed control circuit, power control circuit, main steam pressure limit circuit, etc., as shown in figure 34-10.

① Turbine state control loop. The state control circuit of steam turbine is to control and monitor the state of steam turbine, so as to complete the preparation work before the impulse start of steam turbine and the operation of unit shutdown, and monitor various operation parameters of steam turbine at the same time.

② Speed control circuit. The operator sets the target speed through the operation keyboard and CRT of the operator station to carry out impulse and speed up. The speed control loop detects the speed signal of the steam turbine by the reluctance transmitter and feeds it back to the DEH. The speed of the steam turbine is controlled by PID no difference adjustment. When the unit reaches the critical speed area, the DEH makes the unit pass quickly and refuses all stop signals. When the speed rises to the synchronous speed area, the electrical synchronous signal can be accepted to complete the grid connection and load of the unit

③ Power control circuit. After the unit is connected to the grid, it will automatically carry the initial load of 3% ~ 5% rated power to prevent reverse power operation. The operator can set the target value through the operation keyboard and CRT, feed back the actual power by the power transmitter, and control the load of the steam turbine through PID adjustment in the power control circuit until the target load is reached. CCS signal can also be accepted to control the load of the steam turbine and realize the coordinated control of the turbine and boiler.

④ Main steam pressure limiting circuit. Once the main steam pressure is lower than the limit value, DEH control system can switch to the main steam pressure limit circuit to reduce the current load and maintain the minimum main steam pressure

2.6.1.3. Main functions of DEH. The DEH control system of steam turbine can be operated by the operator through the keyboard of the operator station and CRT to control the functions of the steam turbine, such as impulse starting, speed up, grid connection, load and so on.

① State control. The operator sends out command signal through DEH operation screen to operate and monitor the state of the steam turbine before impulse starting, control reset solenoid valve, reset the steam turbine by remote control, establish safety oil, and detect the important parameters of the steam turbine before impulse starting.

② Speed control. Complete the whole closed-loop control from turning speed to synchronous speed or overspeed test speed. In the process of speed up, the turbine speed increases from turning speed to synchronous speed according to the preset target speed and speed up, which has a wide range of speed control function.

③ Start speed up. According to the start-up mode selected by the operator, the target speed and speed-up rate can be changed in turn, and the predetermined speed-up curve can also be selected. Only one operation is needed to complete the process from turning speed to impulse starting, warm up the engine at low speed, quickly pass through the critical speed zone, warm up the engine at medium speed, and maintain the speed of 3000r / min.

④ The same period. After the speed of the unit is set at 3000r / min, the operator switches to the automatic synchronous control through the DEH operation screen, receives the increase / decrease signal of the electrical "automatic quasi synchronous" device, and controls the speed of the steam turbine, so as to complete the grid connection and load of the unit.

⑤ Overspeed test. The overspeed test is to set the target speed under DEH control, so as to control the speed of steam turbine and carry out electric overspeed protection test and mechanical protection test.

⑥ Overspeed protection function. DEH has OPC overspeed protection control function. When the speed reaches 103% of the rated speed, OPC acts to quickly close all control valves to prevent turbine overspeed; DEH system will automatically re open the control valves after the speed is reduced to maintain turbine idling at synchronous speed, and then re grid. When the speed exceeds the shutdown value (110% rated speed), a trip signal will be sent out to quickly close all main steam valves and control valves.

⑦ Automatic start control (ATC). According to the relevant temperature state of the steam turbine, according to the cold and hot state of the steam turbine, ATC control can be realized, so that the steam turbine can automatically complete the control from the turning speed to the synchronous speed according to the predetermined start-up procedure; or according to the calculation of the rotor thermal stress, the target speed and speed-up can be determined to complete the start-up control of the steam turbine.

⑧ Load control. DEH can realize the constant speed of 3000r / min. after the same period of grid connection, the target load and load increase rate of the unit can be set in advance, so as to carry out closed-loop control of the unit load.

⑨ Automatic with initial load and load limit. After the unit is connected to the grid, DEH will automatically carry the initial load to prevent reverse power operation, and has the load limiting function. When the grid requires increasing or decreasing the load, DEH load control can open or close the regulating valve; in addition, there is power limiting to prevent the generator from overload.

⑩ Automatic adjustment of electric load. DEH can automatically adjust the electric load of the unit to full load according to the target value and load change rate given by the operator, and adjust the load of the unit at any time to meet the load requirements of the power grid and improve the peak load regulation performance of the unit.

⑪ Primary frequency modulation function. Receiving network control frequency difference signal, adjusting turbine load, participating in primary frequency regulation,

⑫ Remote control DEH load control can receive CCS4 ~ 20mA command signal in remote control mode to control turbine load and realize coordinated control of turbine and boiler.

⑬ Valve management. In the start-up stage, the system operates in a single valve mode, that is, four control valves are opened synchronously and two reheat control valves are opened synchronously, which can make the rotor and cylinder heat evenly and facilitate uniform thermal expansion. After a certain load, it can be switched to the sequence valve operation. In this way, according to the load, two or three of the four regulating steam can be fully opened, and only one is throttling. Therefore, the throttling loss of the valve is reduced, and the efficiency is improved. At the same time, the impact of steam flow on the fully opened valve is also reduced, so as to improve the service life of the valve.

⑭ Valve test. In order to ensure the safe operation of the unit, monitor the flexibility of each actuator and valve, and prevent jamming, the operators can regularly conduct on-line activity test of each inlet valve.

⑮ Manual / automatic control. DEH control system is designed with manual and automatic control modes. The operation of steam turbine is based on automatic control mode, manual control mode is used as standby, and manual control mode and automatic control mode track each other. Once the automatic control mode fails, such as redundant DPU or more than two speed channels, DEH will automatically switch to manual control mode without disturbance, and the operator will directly control the regulating valve manually. After the automatic control returns to normal, DEH can switch from manual control to automatic control without disturbance,

⑯ Data display and alarm printing. The operation parameters of the steam turbine can be displayed as required to reflect the operation status of the steam turbine in time. Once the alarm signal appears, the accident status can be recorded through the printer,

⑰ Simulation. According to the operation characteristics of the unit, the speed and power of the steam turbine are simulated to form a closed-loop control of the electric control system. The static test of the control principle, logic, configuration and screen operation of the control system is carried out to check the integrity of the whole control system. At the same time, the static joint adjustment of electro-hydraulic and hydraulic system is realized,

2.6.1.4. Hardware configuration of DEH. DEH system is composed of operator / engineer station, control processor (DPU), I / O card, power supply, power amplifier card, system communication interface and so on,

① Operator / engineer station. The operator / engineer station enables the operators to control and monitor the steam turbine through keyboard or mouse and CRT operation. The operation is simple and easy to master. The operator / engineer station can use the configured graphic software to control and monitor the steam turbine, modify the application software, and also complete the system configuration, network application software download, system initialization, system status monitoring, online modification and other functions. For example, the hardware used in the electric dispatching control system is the same as that of the DCS control system, and the operator / engineer station can be the same as dxcs share,

② Control processor (DPU). The control processor (DPU) is a redundant configuration, and two DPUs are standby for each other, which is the center of the whole control system. The processor has the functions of fast processing speed, fast response to various events, accurate completion of PID operation, network communication, BITBUS communication, logic operation, data processing, etc,

It has two kinds of memory. The other is the static memory, which is used to store data and program data after power failure.

③ Input output device (I / O card). Input and output equipment (I / O card) includes analog input / output card, thermocouple / thermal resistance input card, switch input / output card, power amplifier card / servo card.

④ Redundant system power supply,

⑤ Redundant system communication interface.

2.6.1.5. Index performance of DEH Control System

① Speed control range: 0 ~ 3400r / min

② Load control range: 0% ~ 115%

③ The speed difference rate is adjustable from 3% to 6%

④ The system delay rate is less than 0.06%

⑤ Speed control accuracy: ± 1 R / min

⑥ Load control accuracy: 1MW

⑦ Speed protection loop time is less than or equal to 20ms, speed control loop time is 50ms, DEH device operating environment is 0-50 ℃, the device is installed in the machine room

2.6.2. Hydraulic actuator (EH), which is the actuator controlled by steam turbine, adopts high-pressure fire-resistant oil. The actuator consists of electro-hydraulic servo valve, hydraulic servo motor, quick unloading valve, filter screen, isolation valve, one-way valve and position feedback linear differential displacement transmitter. The electro-hydraulic servo valve controls the flow into the hydraulic servo motor, thereby controlling the movement speed of the piston of the hydraulic servo motor; the hydraulic servo motor is the power output; the quick unloading valve is used to quickly close the hydraulic servo motor, and the one-way valve serves as the isolation function between the electro-hydraulic actuator and the low-pressure oil return circuit and OPC or AST oil circuit, so as to maintain and replace the electro-hydraulic actuator components online during the operation of the unit.

2.6.2.1. Electro hydraulic servo valve. The electro-hydraulic servo valve is an important part to convert electrical signal into hydraulic signal. It receives control signal from DEH and outputs control oil pressure through signal conversion

2.6.2.2. EH oil supply system. EH oil supply system provides power oil source for high-pressure fire-resistant oil engine. The oil supply pressure is 14MPa and the working oil is triarylphosphate (commonly known as fire-resistant oil). In order to ensure the reliability of oil supply, the oil supply system adopts two channels, which are standby for each other, and has its own independent oil pump, motor, filter assembly, flowmeter, etc. Electrical and oil pressure interlock is also set between the working pump and the standby pump.

EH oil supply system is a combined structure, which is composed of oil tank, oil pump, filter, accumulator, oil cooler, regeneration device, stainless steel oil pipeline, various valves and terminal boxes, as well as local instruments and control equipment used to monitor the operation condition of oil supply system.

In order to ensure the cleanliness of high pressure fire-resistant oil, the oil tank is made of stainless steel.

Accumulator is provided as buffer device in EH oil system to improve the dynamic characteristics of actuator and provide pressure oil for emergency operation in case of failure of feed pump.

2.6.2.3. oil motive. The oil motive is to change the stroke continuously according to the change of control oil pressure to control the opening of the regulating valve, so that the turbine can operate according to DEH instructions. Figure 34-11 shows the EH control oil system.

According to the function of the steam inlet valve controlled by the oil engine, the type of the oil motive is decided, namely, the regulating type and the switch type. The regulating oil function controls the steam valve at any position, and adjusts the steam intake in proportion to meet the load demand; the switch type oil motive can only control the steam valve in the fully open or fully closed position. The main steam valve (TV), high pressure regulating valve (GV) and medium pressure regulating valve (IV) of this unit are of regulating type oil motive; RSV is of switch type.

2.6.3. turbine monitoring instrument (TSI)

2.6.3.1. general. The parameters to be monitored during turbine operation, except for the conventional thermal measurement parameters (temperature, pressure and vacuum), the larger part is mechanical quantity, such as axial displacement of rotor, relative expansion between rotor and cylinder, absolute expansion of cylinder, bearing vibration, rotor bending, turbine speed, etc. The measurement and monitoring of these mechanical quantities must be carried out with special equipment, namely turbine supervision instrument system TSI (turbine supervision instrument)

The turbine monitoring instrument system is a kind of multi-channel monitoring instrument, which can continuously measure the mechanical parameters of the rotor and cylinder of the steam turbine generator set, and display the mechanical operation status of the monitored object. Provide standard analog output signal of 4-20mA to relevant controller or recorder, and send out alarm and stop signal when exceeding the set operation limit. Measurement can also be used for fault diagnosis.

2.6.3.2. main monitoring objects:

① The peak peak (absolute vibration) of absolute vibration of the rotor

② Peak peak value of bearing pedestal vibration (bearing pedestal vibration or pad vibration)

③ Peak peak value of rotor vibration relative to bearing pedestal (shaft vibration)

④ The phase angle (key phase) between the peak point and the reference point of rotor vibration

⑤ Peak peak value (eccentricity) of rotor eccentricity

⑥ Axial displacement value of rotor thrust disk relative to thrust bearing seat (axial displacement)

⑦ The difference in expansion between rotor and cylinder (relative expansion).

⑧ Cylinder expansion value relative to base (absolute expansion)

2.6.3.3. hardware configuration. TSL mainly produces Bentley company, Philips company and vebmet company in Switzerland. The system includes the instrument frame and the sensor with wire and signal amplifier (proximitor). The sensors include linear displacement converter (LVDT), eddy current sensor and speed sensor.

2.6.3.4. Function Description:

① Axial displacement. The 4-channel axial displacement monitoring system continuously monitors the axial displacement of the rotor. Each system consists of one monitor and two sets of proximitors and probes with cables. Monitor ant is on the frame

The signal generated by the prox and the probe is proportional to the position of the rotor relative to the thrust disc. The monitor converts the output of the proximitor into a proportional signal to drive the monitor's indication and provide the output signal for the external recorder.

Each monitor can send warning (alarm) and hazard (shutdown) signals from each channel to the relay assembly. Relay assembly contains selection logic, which can identify alarm signal on any one of the two channels, but only danger signals from two channels can be identified at the same time. Therefore, if one of them fails, false hazard alarm will not occur. Two two channel axial displacement monitoring system are double system, so that the work is reliable

② Eccentric. The eccentric monitor and its corresponding sensors can measure the bending of the shaft at low speed, which may be the original mechanical bending, thermal bending, gravity induced bending or both of these bends.

It is very important to measure the eccentricity of large steam turbine before starting. This kind of measurement is helpful to control the excessive vibration, friction, bearing damage and so on

The eccentricity monitor receives the input from the approaching probe to measure the deviation of the axis. The Keyphasor monitoring module receives the Keyphasor probe signal and uses a peak to peak signal conditioning circuit for synchronous reference. The Keyphasor sensor works once in each rotor eccentricity measurement cycle

This technique means that the rotor rotates one full revolution and the shaft bending is measured once. The monitor receives this once per revolution signal but provides two different measurements.

Direct eccentricity - when the approaching probe measures the deviation of the shaft at low speed, the direct eccentricity signal also changes with the DC voltage signal output by the approaching probe.

Peak to peak eccentricity the peak to peak value of the changing signal is also measured after the rotor is rotated one revolution and its deviation is measured. At the same time, a new signal is generated, which is proportional to the actual peak to peak eccentricity.

③ Differential expansion and cylinder expansion. Differential expansion and cylinder expansion monitors are designed to monitor the thermal expansion or contraction of rotors and cylinders. Differential expansion is used to measure the axial thermal expansion of the rotor relative to the cylinder, while cylinder expansion is used to measure the axial expansion of the cylinder relative to the foundation.

④ Vibration monitor. It can provide high quality on-line monitoring, and is suitable for various forms of rotating machinery. It can continuously measure the radial vibration and the average position (clearance) of the shaft, receive the signal from the non-contact sensor system, and install two mutually perpendicular probes on the section of the same shaft.

Figure 34-12 shows a typical configuration diagram of monitoring instruments.

2.6.4. Emergency trip control system (ETS).

2.6.4.1. general. Emergency trip control system (ETS) is a protection equipment to protect the normal operation of steam turbine. It selects reliable hardware equipment, designs its control principle according to the operation specification of steam turbine. In case of emergency, the turbine will be shut down quickly to protect the safety of the equipment. ETS functions include: overspeed protection, axial displacement protection, low lubricating oil pressure protection, shaft vibration protection, vacuum low protection function, etc. In order to adapt the operation of the turbine to the normal operation of the whole plant system, a remote control protection interface is designed in practice, which accepts the signal of emergency shutdown of the turbine caused by factors other than the turbine.

2.6.4.2. system composition. The ETS device consists of a control cabinet (there are 2 rows of PLC components in the control cabinet), one operator test panel, one overspeed control box (including 3 speed relays with processing and display function), one AC power box, one DC power box and two row input and output terminals (u1-u4) located on the back of the control cabinet. The PLC components currently used are mainly produced by Siemens, Omron and Modicon.

PLC component is composed of two sets of independent PLC components, namely, the main PLC (MPLC) and the auxiliary PLC (BPLC). These PLC components adopt intelligent block logic to provide accurate turbine trip signal. Both the main and secondary PLC can provide all the functions of block, alarm and test. If the MPLC fails, BPLC will continue to run and still have the blocking function.

All three speed relays can digital process the input signals of independent reluctance transmitters, and when the speed exceeds the relay set point, the contacts of the relay are closed or disconnected. In each speed relay, two speed setting points trigger two independent relays and provide speed indication. S1 is the normal overspeed setting point, which is usually set as 110% (3300r/min) of rated speed; S2 is the raised overspeed setting point, which is usually defined as 114% (3420r/min) of rated speed.

Three magnetoresistance sensor probes detect the speed. When the PLC logic indicates that 2 of the three speed relays exceed the speed, the PLC sends an overspeed signal to block the turbine, which can prevent improper turbine interruption or prevent normal turbine interruption due to the fault of one sensor or speed relay.

Two terminals provide the user with the field input and output signal interface.

The AC power box requires 2 independent AC power supplies. If one power supply fails, the unit will continue to operate. Two independent AC power supply is fed by the AC power box at the lower part of the control cabinet.

2.6.4.3. user interface. The operator test panel is installed on the door in front of the control cabinet for monitoring and operation. The field interface of ETS cabinet has 2 rows of 80 core terminal strips, which provide the contact connected with the following equipment:

① Signal from three independent speed probes.

② To cut off the power supply of the solenoid valve.

③ Pressure switch to monitor the trip condition.

④ The pressure switch is used to monitor the important monitoring parameters of steam turbine, such as bearing oil pressure, EH oil pressure and condenser vacuum.

⑤ Axial displacement output contact from TSI

⑥ Test solenoid valve,

⑦ When ETS detects a fault, it will send out the output signal of external sound and light alarm.

⑧ Remote cut-off input signal: provide 6 external inputs, such as manual cut-off, vibration, differential expansion, etc. when the signal comes, automatically cut off the unit.

2.6.4.4. Use of operator test panel during normal operation. If an alarm occurs, the indicator light on the corresponding function key or part of the indicator light on the upper part of the panel will be lit on the operation test panel, as shown in figure 34-13. When the indicator light of the sensor is in the "non normal" state, press the button once. The light on indicates the alarm state, and the light off indicates the normal state. When the sensors of the two channels are in the following alarm states, such as low EH oil pressure, low lubricating oil pressure and low vacuum; when two sensors in the three overspeed channels indicate overspeed, or the remote trip signal acts, the turbine will trip.

2.6.4.5. Use the operator test panel to test the online blocking function:

① Press the "enter test" function key on the keyboard to enter the test mode.

② Press the function key to be tested (such as EH oil pressure, lubricating oil pressure, low vacuum, etc.)

③ Pressing the "1 channel" or "2 channel" key corresponds to the channel to be tested.

④ Press the "test confirmation" button to test.

⑤ Verify that the channel tested by the lighted indicator is in action.

⑥ Press the "test reset" key to reset the corresponding action channel.

⑦ It is confirmed that the test channel is no longer blocked.

⑧ If the test is completed, press the "exit test" key to exit the test mode.

2.6.4.6. ETS related equipment. The ETS equipment and the following equipment constitute the ETS system:

① Block: including solenoid valve 20-1 / AST, 20-2 / AST, 20-3 / AST, 20-4 / AST and pressure switch 63-1 / AST, 63-2 / AST and 63-3 / AST.

② Low bearing oil pressure test block: including pressure switch 63-1 / LBO, 63-2 / LBO, 63-3 / LBO, 63-4 / LBO and test solenoid valve 20-1 / LBOT, 20-2 /LBOT.

③ Low eh pressure test block: including pressure switch 63-1 / LP, 63-2 / LP, 63-3 / LP, 63-4 / LP and test solenoid valve 20-1 / LPT, 20-2 / LPT.

④ Low vacuum test block: including pressure switch 63-1 / LV1, 63-2 / LV1, 63-3 / LV1, 63-4 / LV1, 63-1 / LV2, 63-2 / LV2, 63-3 / LV2, 63-4 / LV2 and test solenoid valve 20-1 /LV1t, 20-2 / LV1TT, 20-1 /LV2T, 20-2 / LV2T.

Figure 34-14 shows the ETS operator test panel interface. The axial displacement monitoring equipment includes axial displacement position sensor, contact RP1 and RP2 (in TSI).

2.7. Auxiliary system

2.7.1. Steam seal system. The function of the steam seal system of the steam turbine is to prevent the steam in the steam turbine from leaking out along the axis, to prevent the steam from entering the bearing pedestal, causing water in the oil to affect the oil quality, to leak into the machine room to affect the environment, and to prevent the air from entering the cylinder. At the same time, from the economic point of view, it is to recover the leakage heat and reduce the loss. The main components of steam seal system include steam seal regulating valve and isolation valve, desuperheater, desuperheating water regulating valve and isolation valve, steam seal cooler and exhaust fan, safety valve, steam filter screen, steam seal pipeline and accessories.

2.7.2. Drainage system. The function of the steam turbine drainage system is to remove the condensate in the important parts of the steam turbine, such as the condensate in the main steam pipe, the condensate in the cylinder, etc. Reduce the accumulation of water in these parts, prevent the thermal impact caused by water inflow of steam turbine, avoid blade damage, component deformation and collision between dynamic and static components. The main components of the drainage system include the drain valve (including cylinder drain, main steam and reheat steam pipe drain, steam extraction pipeline drain in front of the steam extraction check valve, etc.) and the drainage pipeline and accessories.

Figure 34-15 and figure 34-16 show the steam seal system and drainage system of this series of models respectively.

2.7.3. Low pressure cylinder water spray system. The water spray system of low pressure cylinder provides condensate to the nozzles of water spray rings at both ends of double flow low pressure cylinder, so as to avoid the rapid rise of exhaust temperature caused by the negative work of the last several stages of long blades of low pressure cylinder under the condition of small flow. The main components of the low pressure cylinder spray system include the control valve, isolation valve, nozzle and spray ring. Figure 34-17 shows the low pressure cylinder water spray system of this series of models.

 

3. Scope of supply

3.1. the turbine body includes all equipment and accessories from the main steam valve to the regulating valve to the high-pressure cylinder, the medium pressure combined steam valve to the medium and low pressure cylinder, the steam connecting pipe of the middle and low pressure cylinder, the expansion joint and the low-pressure cylinder.

3.2. body drain refers to the drain of main steam valve, before check valve, including the drain of cylinder.

3.3. check valves for extraction at all levels and high exhaust check valves.

3.4. all equipment and pipelines of lubricating oil system and jacking oil system (excluding support and hanger and generator oil inlet and return pipe).

3.5. all equipment (including electronic equipment) and pipelines (excluding supports and hangers) of digital electro-hydraulic regulation system.

3.6. all equipment and pipelines in shaft seal system (excluding supports and hangers).

3.7. all equipment and pipelines (excluding supports and hangers) in the drainage and exhaust system of the body.

3.8. all equipment of safety monitoring system (TSI).

3.9. all equipment of emergency trip system (ETS).

3.10. thermal instrument and equipment of the body.