RU2227212C2 - Steam turbine protection device - Google Patents

Abstract

FIELD: power engineering. SUBSTANCE: device is designed to protect steam turbine with mixing condenser. Proposed device contains stop valve and turbine technological parameters maximum deviation safeguards. Stop valve drive is connected through interpiston spaces along oil line in series with high-pressure oil source. Device is furnished with spring-loaded normally open vacuum popping valve connected through seat with plate to steam space of condenser and ambient atmosphere. Device is furnished with float-type condensate level relay in condenser with control spool valve and impulse spool valve. Interpiston space of control spool valve is connected first in direction of oil flow from high- pressure oil source to stop valve drive. Interpiston space is connected also to drive to vacuum popping valve. Interpiston space of control spool valve is connected through first interpiston space of impulse spool valve to high-pressure oil source and to oil tank. End face chamber is connected through second interpiston space of impulse spool valve and through interpiston space and end face chamber of said spool valve to oil tank. Spool of impulse spool valve is furnished with hydraulic damper. For this purpose bore is made in spool and cylindrical projection is made in housing of impulse spool valve to form ring groove getting into bore with radial clearance. Electromagnet switches off drive from turbine oil tank by electric signal and bypasses high-pressure oil delivery. Hydraulic damper slows movement of spool so that spool can return to its initial position without emergency oil pressure drop in oil line of turbine protection system. EFFECT: improved protection of steam turbine. 3 dwg

Description

The invention relates to the field of protection of a steam turbine, mainly a turbine with a mixing type condenser.

Steam turbine protection devices are known.

It is known [1] a device for protecting a steam turbine, in which the steam turbine is protected by the deviation of the technological parameters of the turbine.

The device contains sensors for technological parameters of the turbine (speed, oil pressure, axial shift of the rotor, etc.), a check valve with quick-locking hydraulic actuator, an automatic shutter and a remote oil switch with control spools.

The stop valve actuator is connected in series through the inter-piston cavities of the control spools to a high pressure oil source. In addition, each of them is connected to drain the oil into the turbine's oil tank. When triggered, the control spools shut off the high pressure oil supply to the check valve actuator and communicate with the oil tank. Under the action of the springs, the stop valve closes and stops the steam supply to the turbine.

On steam turbines with a mixing condenser, in some cases, the device does not provide protection for an emergency increase in the level of condensate in the condenser. This occurs when cooling water enters the condenser by self-priming cooling water from the pool (due to pressure drops in the condenser and atmospheric pressure). In this case, the condensate is removed from the condenser (to the cooling tower) using a pumping electric pump. When the electric pump fails (or de-energizes), a quick overflow of the capacitor occurs. The condenser level in this case reaches the turbine blade apparatus, which leads to a turbine accident.

The disadvantage of this device is that it does not protect the steam turbine in case of an emergency increase in the level of condensate in the mixing condenser with self-priming of cooling water in the event of an emergency failure of the electric pump for pumping water from the condenser.

It is known [2] a steam turbine protection device (prototype), in which a steam turbine with a mixing condenser with self-priming cooling water is protected against the maximum deviation of the technological parameters of the turbine and with an emergency increase in the level of condensate in the condenser.

The turbine protection device contains a stop valve and protection elements according to the maximum deviations of the technological parameters of the turbine. The inter-piston cavities of the spools of the protection elements are connected to a drain in the turbine oil tank. Through them, the hydraulic actuator of the stop valve is connected in series to a source of high pressure oil.

The device is equipped with a spring-loaded normally open high-speed valve for undermining the vacuum with a hydraulic actuator connected to the vapor space of the condenser and to the atmosphere. The device is also equipped with a float hydraulic relay with a control and pulse spools with inter-piston cavities and end chambers.

The control valve is installed first along the high-pressure oil to the stop valve actuator. In this case, the inter-piston cavity of the control valve is also connected to the actuator of the vacuum blow-off valve and to drain the oil into the turbine oil tank through the first inter-piston cavity of the pulsed valve. The end chamber and the inter-piston cavity of the control spool are hydraulically interconnected and connected through the second inter-piston cavity of the pulse spool to the high pressure oil source and through its end chamber to the turbine oil tank.

The control spool protects the turbine in case of an emergency increase in the condensate level in the condenser (as well as the other protection elements according to the technological parameters of the turbine) by stopping the supply of high-pressure oil to the inter-piston cavity and its communication with the drain in the turbine oil tank (through the first inter-piston cavity of the pulse spool). The oil pressure in the actuators of the stop valve and the vacuum detonation valve drops and they work, stopping the supply of fresh steam to the turbine and undermining the vacuum in the condenser. The flow (by self-priming due to the pressure difference in the condenser and the atmosphere) of cooling water to the condenser stops, which protects the turbine by an emergency increase in the level of condensate in the condenser.

The pulse spool is designed to provide a very important function - pacing a float hydraulic relay on a running turbine.

When the electromagnet is turned on, the impulse spool moves to the extreme position and blocks the oil drain from the inter-piston cavity of the control spool through its first inter-piston cavity into the turbine's oil tank and communicates the end chamber of the control spool through the second inter-piston cavity of the pulse spool with a high-pressure oil source. In this case, under the action of the oil pressure force in the end chamber, the control spool (with lever transmission and float) moves to its second extreme position, blocking the high pressure oil supply to the inter-piston cavity of the control spool along the main channel and opening the oil drain window from this cavity, however, the drain oil does not occur, since the first inter-piston cavity of the pulse spool, through which the oil is drained into the oil tank, is cut off. Compensation of oil leaks through the turbine protection elements into the oil tank in this mode is carried out due to the high pressure oil entering through the auxiliary channel from the end chamber into the inter-piston cavity of the control valve. As a result, when the control spool is moved to a position corresponding to an emergency increase in the level of condensate in the condenser, the oil pressure in the actuators of the stop valve and the vacuum detonation valve does not decrease and they do not work.

When the electromagnet is turned off, the impulse spool under the action of the spring moves to its original position, in which the second inter-piston cavity of the spool is disconnected from the high-pressure oil source and simultaneously with the first inter-piston cavity communicates with a drain into the turbine oil tank.

Under the influence of the gravity of the float and the tension force of the spring, the control spool also moves to its original position, displacing oil from the end chamber through the second inter-piston cavity of the impulse spool into the oil tank. Upon reaching the initial position of the control spool, the cycle of walking the relay on a working turbine ends, the device is again ready to perform its functions of protecting the turbine by deviating the technological parameters of the turbine and by emergency raising the level of condensate in the condenser.

The disadvantage of the prototype device is that in some cases, when the condensate level switch is paced on a working turbine, an unauthorized actuation of the stop valve and the vacuum detonation valve can occur with the steam supply to the turbine stopped and the vacuum in the condenser undermining.

The reason for the noted disadvantage of the prototype device is that the end chamber of the pulse spool is connected to the turbine oil tank and is not filled with oil. When the electromagnet is turned off, the pulse spool moves to its original position very quickly. The end chamber of the control valve when pacing is connected to a high pressure oil source, filled with oil and, in addition, is fed with oil from the inter-piston cavity of the valve, so its return to its original position is much slower (due to the need to displace oil from its end chamber), with delay.

In this case, a situation may occur when the inter-piston cavities of the pulsed spool are already connected with the drain to the oil tank, while the inter-piston cavities of the control spool are not yet disconnected from the first inter-piston cavity of the pulsed spool and are not connected to the high pressure oil source. As a result, when the relay is pacing due to a delay in the actuation of the control valve, a drop in oil pressure in the actuators and the actuation of the shut-off valve and the vacuum detonation valve can occur.

The purpose of the invention is to create a protection device for a steam turbine with a mixing type condenser that does not have this drawback.

The purpose of the invention is achieved in that the steam turbine protection device comprises a shut-off valve, a vacuum valve for detonating the vacuum in the condenser, turbine protection elements according to process deviations, a float hydraulic condensate level switch in the condenser with a control valve and a pulse valve.

The inter-piston cavities of the spools of the turbine protection elements are connected to the oil tank. The lock valve actuator is connected in series to the high pressure oil source through the inter-piston cavity of the control valve of the level switch and through the inter-piston cavity of the valve spools of the turbine protection elements. The drive of the vacuum detonating valve in the condenser is connected to the high pressure oil source through the inter-piston cavity of the control spool, which is also connected to the turbine oil tank through the first inter-piston cavity of the pulse spool. The second inter-piston cavity of the pulsed spool is connected to a high-pressure oil source and to the end chamber of the control spool. The end chamber of the control spool is in communication with the oil tank through the end chamber of the pulse spool.

What is new is that the inter-piston cavity of the control spool is also connected to the first inter-piston cavity of the pulse spool, the first and second inter-piston cavities of the pulse spool are hydraulically interconnected. In this case, the impulse spool is equipped with a hydraulic damper, for which a bore is made in its spool and a cylindrical protrusion is made in the impulse spool body, forming an annular groove in the body. The protrusion enters the bore of the spool with a radial clearance.

When cocking the pulse spool, the protrusion comes out of the groove and it is filled with oil. During the reverse stroke of the spool, the protrusion squeezes the oil from the annular groove, which provides damping and slowing down the movement of the spool. During the deceleration of the impulse spool, the control spool takes its initial position. This eliminates the possibility of unauthorized operation of the protection system when pacing the condensate level switch in the capacitor.

The proposed protection device for a steam turbine is shown in the drawings of figure 1, figure 2 and figure 3.

In Fig.1 shows a diagram of the device in the initial (working) position, Fig.2 pulsed spool shown in the middle (intermediate) position that it passes when the electromagnet is turned on, and Fig.3 pulsed and control spools are shown in the extreme positions occupied when pacing the device.

Figure 1: mixing type condenser 1, turbine exhaust pipe 2, rotor 3 with blading of the last stage 4. A vacuum blow-off valve 6 is installed on the body 5 of the condenser 1, a lever gear 7 with a float 8 and a nozzle 9 for supplying cooling water through the pipeline is fixed 10. Condensate 11 is pumped by the electric pump 12 to the cooling tower through the pipe 13. The stop valve 14 with hydraulic actuator 15 is connected at the input 16 to the source of fresh steam and at the exit 17 to the steam inlet of the turbine. The turbine protection device has a condensate level switch in the condenser 1, comprising a control spool 18 connected to the linkage 7, a pulse spool 19, as well as a first element 20 and a second turbine protection element 21 for maximizing the turbine technological parameters. The control valve 18 contains a valve 22 with an inter-piston cavity 23 and an end chamber 24 and has working windows 25, 26 and 27. The pulse valve 19 contains a valve 28 with a first, second, third and fourth inter-piston cavities 29, 30, 31 and 32, an electromagnet 33 connected to the spool 28, spring-loaded 34, and has working windows 35,36, 37, 38, 39 and 40. The channel 41 is made in the spool 28, communicating between the inter-piston cavities 29 and 30, and the bore 42 is made. In the bore 42 with a radial clearance, a cylindrical protrusion 43 with a hole 44 made th inside the housing of the pulse spool 19.

Protection elements 20 and 21 contain spools 45, 46, spring-loaded springs 47, 48 with inter-piston cavities 49, 50 and have working windows 51, 52 and 53, 54. End chambers 55, 56 are connected to turbine protection system pulse oil lines 57, 58 .

The vacuum detonating valve comprises a piston 59, on the stem of which a plate 60 is suspended. The working surface of the plate 60 is rubbed against the working surface of the seat 61. The piston 59 is spring-loaded with a spring 62. In combination with the body 63, it forms chambers 64 and 65. The chamber 66 is connected with atmospheric windows. The device is connected to a high pressure oil source by an oil line 67. The components of the device are interconnected by oil lines 68, 69, 70, 71, 72, 73.

Oil line 74 is connected to the turbine oil tank. Between the housing of the control valve 18 and the end of the valve 22 there is a gap 75 that determines the stroke of the valve 22.

Figure 2: the spool 28 of the pulse spool 19 is shown in the intermediate position, which it occupies (passes) under the action of the electromagnet 33. In this position, the end face of the spool 28 is removed from the annular groove 76 and is at the level of the cylindrical protrusion 43. In this case, the windows 36 and 40 are blocked by piston spools 28, window 39 is aligned with inter-piston cavity 31, windows 37 and 38 are closed. The spool 22 of the control spool 18 is in its original position.

Figure 3: the spool 28 of the pulse spool 19 is under the action of the electromagnet 33 its second extreme position. The end face of the spool 28 is removed from the end of the cylindrical protrusion 43. The annular groove 76 is filled with oil to the level of the end of the cylindrical protrusion 43. The space between the oil level in the groove 76 and the end of the spool 28 is communicated through the opening 44 with the atmosphere of the oil tank.

At this position of the spool 28, the windows 36 and 40 are still closed, the window 37 is communicated with the inter-piston cavity 30 and the window 38 is open and communicated through the inter-piston cavity 31 with the window 39. The spool 22 of the control spool 18 is in its second extreme position, in which window 25 is open and window 27 is closed.

The protection device of a steam turbine operates as follows.

In the drawing of figure 1, the device is depicted in the operating position. High-pressure oil is connected from the oil source through the oil line 67 and the inter-piston cavity 23 into the chamber 64 of the vacuum blow-off valve 6, and also through the inter-piston cavities 49, 50 of the turbine protection elements 20, 21 to the hydraulic (quick-locking) actuator 15 of the shut-off valve 14. the valve 14 is open and fresh steam flows through the steam lines 16 and 17 into the turbine. The exhaust steam from the exhaust pipe 2 of the turbine enters the steam space of the condenser 1, into which, due to the difference in atmospheric pressure and the pressure in the condenser, pipe 10 enters cooling water through the nozzle 9. The electric pump 12 through the pipe 13 pumps the condensate 11 into the cooling tower, from which it is discharged into the pool, closing the circle of cooling water circulation.

The end chamber 24 of the control valve 18 is connected via an oil line 69 through a window 40 and an inter-piston cavity 32 with the air space of the turbine oil tank.

If the technological parameters of the turbine deviate (speed, oil pressure of the lubrication system, etc.), the corresponding sensors generate signals (pressure drop of the pulse oil 57 or 58) to one of the protection elements (47 or 48). Elements 47 and 48 act in the same way: for example, if the sensors sharply reduced the pressure of the pulse oil 57, then the spool 45 moves under the action of the spring so that the pistons of the spool 45 block the window 51 and open the window 52. As a result, the high pressure oil supply will be cut off and the actuator 15 connected through window 52 to drain the oil in the turbine oil tank. The check valve 14 closes and stops the supply of fresh steam to the turbine. The vacuum in the condenser 1 will remain, while the pump 12 will continue to work.

In case of emergency stop of the electric pump 12, the level of condensate 11 in the condenser 1 increases due to self-absorption of cooling water from the pool and could reach the last stage 4. However, as the level of condensate 11 increases, the float 8 pops up and it moves the spool 22 through the lever gear 7 so that its pistons will close window 27 and open window 25. In this case, the supply of high-pressure oil to the drive 15 will be stopped and the inter-piston cavity 29 and the window 36 will drain the oil from the drive 15 and from the chamber 64 to the oil tank through the windows 25, 26, 35turbines. As a result, the stop valve 14 closes and cuts off the supply of fresh steam to the turbine, and the plate 60 of the valve 6 for undermining the vacuum under the action of the spring 62 opens and connects the vapor space of the condenser 1 through the chamber 66 and the seat 61 with the atmosphere. The vacuum in the condenser 1 will be undermined and the cooling water will cease to flow from the pool to the condenser. After reducing the level of condensate, the float 8 will move under the action of gravity and move the spool 22 of the control spool 18 to its original position. In this case, the window 25 for draining the oil into the oil tank will be closed and the window 27 will be opened. The high-pressure oil will enter the chamber 64, compress the spring 62 and firmly press the plate 60 to the seat 61. The vapor space of the condenser 1 will be disconnected from the surrounding atmosphere. From this moment, you can restore the vacuum in the condenser 1. Once again, cooling water through the nozzle 9 will flow into the condenser 1 and, therefore, the electric pump 12 must be included in the work. High pressure oil will also enter the actuator 15, which will allow cocking the check valve 14.

Protection of the turbine in terms of condensate level in the condenser 1 is very responsible. To maintain a high degree of protection reliability, it is necessary to periodically pace its elements. For this purpose, an impulse spool 19 is designed. It works as follows.

To walk the spool 22 and the linkage 7 with the float 8 on an operating turbine, an electrical signal is supplied to the electromagnet 33. The electromagnet 33 compresses the spring 34, moving the spool 28 to its second extreme position.

At the first stage of movement, when the end face of the spool 28 moves within the annular groove 76, a vacuum is created in the latter and it is filled through the radial gap between the hole 42 and the protrusion 43 with air (from the hole 42 in communication with the atmosphere of the turbine oil tank). The difference in air pressure at the ends of the spool 28 reduces the speed of the spool 28. In the intermediate position along the spool 28, shown in the drawing of figure 2, the windows 36, 37, 38 and 40 are blocked by its pistons, the end chamber 24 is cut off from high pressure oil and from discharge into the oil tank of the turbine and therefore the spool 22 takes its previous initial (working) position. The planes of the ends of the spool 28 and the cylindrical protrusion 43 are at the same level. Starting from this intermediate position, the further movement of the spool 28 to the position shown in the drawing of FIG. 3 occurs without an air pressure drop across the ends of the spool 28 with a maximum speed determined by the difference between the forces of the electromagnet 33 and the spring 34. In the position depicted in the drawing of FIG. 3, high pressure oil through the windows 38, 39 enters the chamber 24 and moves the spool 22 with the lever gear 7 and the float 8 to its second extreme position, in which the window 27 is closed and the window 25 is open. In this case, when the slide valve 22 moves, its pistons first close the window 27 and only then open the window 25, thereby eliminating the failure of the oil pressure in the oil pipe 71 and the operation of the turbine protection.

The electromagnet 33 holds the spool 28 in the second extreme position for a certain period of time, determined by the duration of the electrical signal. During this time, high-pressure oil from the oil line 69 flows through the window 40 and the gap between the piston of the spool 28 and the bore of the housing of the pulse spool 19 into the annular groove 76 and fills it with oil. In the future, oil leaks are poured through the protrusion 43 into the turbine oil tank. After removing the electrical signal, the electromagnet 33 is turned off and the spool 28 under the action of the spring 34 starts to move to its original (working) position, and the first part of the path (to the position shown in the drawing of figure 2) it passes with a maximum speed determined by the tension force of the spring 34 Since in this case the pistons of the spool 28 block the windows 37 and 40, cutting off the oil filled chamber 24 from the high pressure oil source and from the drain into the turbine oil tank, the spool 22 is in the position shown in the drawing e 3.

Starting from this moment, to continue the movement of the spool 28 to its initial (working) position, the spring 34 must ensure the extrusion of oil located in the annular groove 76 into the turbine oil tank through the radial clearance between the protrusion 43 and the hole 42. As a result, the movement speed of the spool 28 is significantly slowed down . This opens the window 40, the camera 24 of the control spool 18 communicates with the oil tank of the turbine and the gravity of the float 8 moves the spool 22 to its original (working) position, blocking the window 25 and opening the window 27. At the end of the process of walking around the working turbine, the spool 22 with lever transmission 7 and the float 8 assume the initial (operating) position shown in the drawing of FIG. 1, and the steam turbine protection device is again ready to perform its protective functions in full.

Walking control spool 18 can be carried out in a similar manner also on a stopped turbine.

Literature

[1] Steam turbines of low power KTZ. / Ed. V.I. Kiryukhina. - M.: Energoizdat, 1987, p. 134, Fig. 7.1.

[2] Patent No. 2174180, 09/27/2001, F 01 D 21/02.

Claims (1)

A steam turbine protection device containing a stop valve, a vacuum detonating valve in the condenser, turbine protection elements according to the maximum deviations of the technological parameters, the inter-piston cavities of the spools are connected to the oil tank, and the hydraulic float condensate level switch in the condenser with the control spool, through the inter-piston cavities of which the stop valve is driven the valve is connected in series to a high-pressure oil source, to which through the inter-piston cavity of the control valve The actuator of the vacuum detonating valve is also connected, and an impulse valve, through the first inter-piston cavity of which the inter-piston cavity of the control valve is connected to the oil tank, and its second inter-piston cavity is connected to the high pressure oil source and to the end chamber of the control valve, which is connected to the oil tank through the end chamber of the pulse spool, characterized in that the inter-piston cavity of the control spool is also connected to the first inter-piston cavity of the pulse spool, cat paradise communicates with its second mezhporshenkovoy cavity, wherein the pulse valve is provided with a hydraulic damper, which is formed in the slide valve bore and a spool housing pulsed formed a cylindrical protrusion forming an annular groove in the housing and belongs with radial clearance into the bore of the spool.

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