CN115111009A - Steam turbine emergency shut-off and main valve control system and use method thereof - Google Patents

Abstract

The invention provides a steam turbine emergency shut-off and main throttle control system and a using method thereof, wherein the system comprises a pressure oil path and a safety oil path, the pressure oil path is respectively connected with three electromagnetic valves, one path of the safety oil path is connected with a forward oil outlet of a hydraulic control one-way valve, a forward oil inlet of the hydraulic control one-way valve is connected with a main throttle control seat, the other path of the safety oil path is connected with a two-way electromagnetic valve, and an outlet of the two-way electromagnetic valve is respectively connected with a control port of the hydraulic control one-way valve and the main throttle control seat; an unloading valve is arranged between the safety oil way and the pressure oil way, and two end interfaces of the unloading valve are respectively connected with the safety oil way or the pressure oil way. The invention can more effectively and reliably realize the steam turbine interruption function by adopting three electromagnetic valves, and can actively judge whether the electromagnetic valves are jammed or invalid through an online experiment, thereby prejudging the maintenance or danger. The main valve can be controlled through the two-way electromagnetic valve and the hydraulic control one-way valve, and unnecessary risks during debugging are reduced.

Description

Steam turbine emergency shut-off and main valve control system and use method thereof

Technical Field

The invention relates to the technical field of hydraulic protection and control of a steam turbine, in particular to a system for controlling emergency interruption and a main throttle of the steam turbine and a using method thereof.

Background

In order to prevent the steam turbine from generating serious damage accidents which are often caused by the work of partial equipment in the running process of the steam turbine, a critical interruption system is arranged on a unit, and a steam turbine critical interruption and main steam valve control device is an essential component in a steam turbine hydraulic system. The emergency shutdown can be realized in the emergency state of the steam turbine; the main valve opening and tightness experiment can be realized during normal starting.

The existing emergency cutoff device of the steam turbine is a magnetic open-circuit throttle, an electric signal is sent to an electromagnetic head to generate magnetic force under an emergency state, so that a valve core acts to discharge safety oil, the safety oil falls to stop a unit, and a main throttle control seat is rapidly closed under the action of a spring. When the safe oil pressure is built up, the main valve is opened automatically. When the main valve tightness experiment is carried out, the safety oil pressure needs to be reduced by manually rotating the handle until the main valve operation seat is in a state of being opened, so that the main valve is closed.

Although functions of steam turbine interruption, main valve opening, main valve tightness experiment and the like can be realized in the prior art, the critical interruption device is often jammed and refused in debugging and running, an electromagnetic head coil is easy to burn out, and manual in-situ resetting is needed after live action. The high-pressure oil pump is started in the debugging process to establish safe oil main throttle opening, if the servo mechanism is impacted by oil pressure and shakes to open the throttle, main steam directly drives the rotor to accelerate the turbine, and the condition is extremely dangerous. When the main valve tightness experiment is performed, the safety oil pressure is reduced by manually rotating the handle, the process is difficult to accurately control due to the manufacturing precision and the manual operation reason, and the purpose of performing the main valve tightness experiment cannot be achieved due to slight insufficient or excessive rotation of the handle. The main valve cannot be closed or the safety oil pressure is too greatly reduced to cause the steam engine to be blocked. The technical drawback referred to above is to provide a reliable, highly integrated interruption and control device without excessive human intervention.

Disclosure of Invention

The invention aims to provide a steam turbine emergency shut-off and main valve control system and a using method thereof, which are safe, reliable and highly integrated and can realize emergency shutdown in a steam turbine emergency state; the opening of the main valve can be realized during normal starting.

According to one object of the invention, the invention provides a steam turbine emergency shut-off and main throttle control system which comprises a pressure oil path and a safety oil path, wherein the pressure oil path is respectively connected with three electromagnetic valves, one path of the safety oil path is connected with a forward oil outlet of a hydraulic control one-way valve, a forward oil inlet of the hydraulic control one-way valve is connected with a main throttle control seat, the other path of the safety oil path is connected with a two-way electromagnetic valve, and an outlet of the two-way electromagnetic valve is respectively connected with a control port of the hydraulic control one-way valve and the main throttle control seat; an unloading valve is arranged between the safety oil way and the pressure oil way, and two end interfaces of the unloading valve are respectively connected with the safety oil way or the pressure oil way.

Furthermore, the solenoid valves are two-position two-way solenoid valves, each solenoid valve is provided with an outlet and an inlet, and the outlets and the inlets of the three solenoid valves are connected in series in pairs.

Further, the electromagnetic valve comprises a first electromagnetic valve, a second electromagnetic valve and a third electromagnetic valve, an outlet of the first electromagnetic valve is connected with an inlet of the third electromagnetic valve, an outlet of the second electromagnetic valve is connected with an inlet of the first electromagnetic valve, and an outlet of the third electromagnetic valve is connected with an inlet of the second electromagnetic valve.

Furthermore, the three electromagnetic valves are respectively connected with a pressure measuring device.

Further, outlets of the first electromagnetic valve, the second electromagnetic valve and the third electromagnetic valve are respectively connected with a pressure sensor through pipelines.

Further, an inlet P of the solenoid valve is connected to the pressure oil path, and an outlet T of the solenoid valve is connected to an oil drain port.

Further, the number of the unloading valves is two, and the two unloading valves are arranged between the pressure oil path and the safety oil path in parallel.

Further, an inlet P of the two-way solenoid valve is connected with the safety oil path, and an outlet T of the two-way solenoid valve is connected with the adjustable throttle valve.

Furthermore, the two-way electromagnetic valve is a three-position four-way reversing valve and comprises a two-position four-way reversing valve and a static position.

Further, when the two-way electromagnetic valve is in one working position, safety oil enters a control port of the hydraulic control one-way valve through a working port A; when the two-way electromagnetic valve is at another working position, the safety oil in the main valve operating seat is discharged to the adjustable throttle valve from an outlet T through a working port A.

According to another aspect of the present invention, there is provided a method for using a steam turbine emergency shutdown and main valve control system, comprising the steps of:

s1, emergency shut-off of steam turbine

The three electromagnetic valves receive electric signals, the three electromagnetic valves are connected in series two by two, and any two electromagnetic valves act to unload pressure oil so that the unloading valve unloads system safety oil to realize steam turbine interruption;

s2, main valve control

The two-way electromagnetic valve and the hydraulic control one-way valve are connected in parallel, one end of the two-way electromagnetic valve is electrified, the safety oil reaches the hydraulic control one-way valve after passing through the two-way electromagnetic valve and opens a valve core of the hydraulic control one-way valve, and the other path of safety oil enters the main valve operating seat after passing through the hydraulic control one-way valve to open the main valve;

after the other end of the two-way electromagnetic valve is electrified, the safety oil under the main throttle control seat enters a preset adjustable throttle valve through the other passage of the two-way electromagnetic valve, so that the main throttle is closed when the safety oil pressure falls to an acceptable range;

s3, on-line shutoff solenoid valve experiment

Load cells are added on the paths of the three solenoid valves which are connected in series in pairs, when only one solenoid valve acts, the function of the whole blocking module cannot be influenced, after an online blocking solenoid valve activity experiment instruction is carried out, one solenoid valve is powered off, when the solenoid valve acts normally, the other solenoid valve connected in series with the solenoid valve is electrified and does not act, so that pressure oil from the solenoid valve is kept at the other solenoid valve, the pressure oil of the whole system is pressurized, an unloading valve does not act, safe oil pressure is established, a pipeline boosting load cell has an indication number, and if the load cell does not see the indication number in the process, the solenoid valve is judged to be broken down.

According to the technical scheme, the three electromagnetic valves are adopted, so that the steam turbine interruption function can be effectively and reliably realized, whether the electromagnetic valves are jammed or invalid can be actively judged through an online experiment, and the overhaul or danger can be pre-judged. The main valve can be controlled through the two-way electromagnetic valve and the hydraulic control one-way valve, and unnecessary risks during debugging are reduced.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a schematic structural diagram of an embodiment of the present invention;

FIG. 2 is a schematic structural diagram of an embodiment of the present invention in an interrupting state;

FIG. 3 is a schematic structural diagram of the embodiment of the present invention in a normal operation state;

FIG. 4 is a schematic structural diagram of a main throttle valve according to an embodiment of the present invention;

FIG. 5 is a schematic structural diagram of the main throttle in a closed state according to the embodiment of the present invention;

FIG. 6 is a schematic structural diagram of the line interrupting solenoid valve in an experimental state according to the embodiment of the present invention;

FIG. 7 is a schematic structural diagram of two solenoid valves in an interrupting state according to the embodiment of the present invention;

in the figure, 1, a first electromagnetic valve; 2. a second solenoid valve; 3. a third electromagnetic valve; 4. a first pressure sensor; 5. a second pressure sensor; 6. a third pressure sensor; 7. a first unloading valve; 8. a second unloader valve; 9. a hydraulic control check valve; 10. a main valve operating seat; 11. a two-way solenoid valve; 12. an adjustable throttle valve.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations and positional relationships based on those shown in the drawings, and are used only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be considered as limiting the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", may explicitly or implicitly include one or more of the described features. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise. Furthermore, the terms "mounted," "connected," and "coupled" are to be construed broadly and may include, for example, fixed connections, removable connections, or integral connections; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

Example 1

As shown in figure 1 of the drawings, in which,

the utility model provides a steam turbine emergency shut-off and main valve control system, includes pressure oil circuit and safe oil circuit, and the pressure oil circuit is connected with first solenoid valve 1, second solenoid valve 2 and third solenoid valve 3 respectively, and an entry P and the pressure oil circuit of first solenoid valve 1, second solenoid valve 2 and third solenoid valve 3 are connected, and another export T of first solenoid valve 1, second solenoid valve 2 and third solenoid valve 3 is connected the oil drain port.

The first solenoid valve 1, the second solenoid valve 2 and the third solenoid valve 3 are two-position two-way solenoid valves, and each solenoid valve is provided with an outlet B and an inlet A respectively. The outlets B and the inlets A of the three electromagnetic valves are respectively connected in series two by two, namely, the outlet B of the first electromagnetic valve 1 is connected with the inlet A of the third electromagnetic valve 2, the outlet B of the second electromagnetic valve 2 is connected with the inlet A of the first electromagnetic valve 1, and the outlet B of the third electromagnetic valve 3 is connected with the inlet A of the second electromagnetic valve 2, so that the two-by-two series connection is realized. The first solenoid valve 1, the second solenoid valve 2 and the third solenoid valve 3 are respectively connected with a pressure measuring device, namely, a first pressure sensor 4, a first pressure sensor 5 and a first pressure sensor 6 are respectively and correspondingly connected to serial pipelines of outlets of the first solenoid valve 1, the second solenoid valve 2 and the third solenoid valve 3.

Two first unloading valves 7 and two second unloading valves 8 which are arranged in parallel are arranged between the safety oil path and the pressure oil path, two end interfaces of the first unloading valves 7 and the second unloading valves 8 are respectively connected with the safety oil path or the pressure oil path, and the first unloading valves 7 and the second unloading valves 8 are arranged between the pressure oil path and the safety oil path in parallel.

One path of the safety oil path is connected with a forward oil outlet of the hydraulic control one-way valve 9, a forward oil inlet of the hydraulic control one-way valve 9 is connected with the main valve operating seat 10, the other path of the safety oil path is connected with the two-way electromagnetic valve 11, and an outlet of the two-way electromagnetic valve 11 is respectively connected with a control port of the hydraulic control one-way valve 9 and the main valve operating seat 10;

one inlet P of the two-way solenoid valve 11 is connected to the safety oil path, and the other outlet T of the two-way solenoid valve 11 is connected to the adjustable throttle 12. The two-way solenoid valve 11 is a three-position four-way reversing valve, and comprises a two-position four-way reversing valve and a static position. When the two-way electromagnetic valve 11 is at a working position, safety oil enters a control port of the hydraulic control one-way valve 9 through the working port A; when the two-way solenoid valve 11 is in the other operating position, the relief oil in the main valve operating seat 10 is discharged from the outlet T to the adjustable choke valve 12 through the working port a.

The use method of the steam turbine emergency shut-off and main valve control system comprises the following steps:

s1, emergency shut-off of steam turbine

The first electromagnetic valve 1, the second electromagnetic valve 2 and the third electromagnetic valve 3 receive electric signals, the first electromagnetic valve 1, the second electromagnetic valve 2 and the third electromagnetic valve 3 are connected in series in pairs, and any two electromagnetic valves act to unload pressure oil so that the first unloading valve 7 and the second unloading valve 8 unload system safety oil to realize steam turbine interruption;

s2, main valve control

The two-way electromagnetic valve 11 is connected with the hydraulic control one-way valve 9 in parallel, one end of the two-way electromagnetic valve 11 is electrified, the safety oil reaches the hydraulic control one-way valve 9 after passing through the two-way electromagnetic valve 11, a valve core of the hydraulic control one-way valve 9 is opened, and the other path of safety oil enters the main valve operating seat 10 to open a main valve after passing through the hydraulic control one-way valve 9;

after the other end of the two-way electromagnetic valve 11 is electrified, the oil pressure under the main valve operating seat 10 enters the preset adjustable throttle valve 12 through the other passage of the two-way electromagnetic valve 11, so that the main valve is closed when the safe oil pressure falls to the acceptable range;

s3, on-line shutoff solenoid valve experiment

First solenoid valve 1, increase load cell on the route of two liang of series connections of second solenoid valve 2 and third solenoid valve 3, only when an solenoid valve moves, can not influence whole interdiction module function, carry out on-line interdiction solenoid valve activity experiment instruction after, one of them solenoid valve loses electricity, when this solenoid valve moves normally, another solenoid valve electrification of establishing ties with it does not move and makes the pressure oil that comes from this solenoid valve keep in another solenoid valve department, the pressure oil of entire system this moment has pressure, so the off-load valve does not move, safe oil pressure is established, make the pipeline pressure boost load cell have the registration, if this process load cell does not see the registration, judge that this solenoid valve breaks down.

Example 2

Detailed description of the preferred embodiments

As shown in fig. 2, in the blocking state: under the shutoff state, the first electromagnetic valve 1, the second electromagnetic valve 2 and the third electromagnetic valve 3 are not electrified, the valve core position of the electromagnetic valves is shown in fig. 2, pressure oil enters a system after passing through a throttling hole, the pressure oil is shown in fig. 2, the three electromagnetic valves are in an open-circuit state (uncharged), the pressure oil is directly discharged through outlets T of the electromagnetic valves, and at the moment, the pressure of a pressure oil way behind the throttling orifice plate is 0. Meanwhile, the upstream of the first unloading valve 7 and the upstream of the second unloading valve 8 have no pressure, and the downstream safety oil overcomes the elastic force of a built-in spring of the unloading valve, directly connects the unloading valve after opening and returns oil, so that the system safety oil pressure is 0.

As shown in fig. 3, in the normal operation state: under a normal operation state, the first electromagnetic valve 1, the second electromagnetic valve 2 and the third electromagnetic valve 3 are electrified, the positions of valve cores of the electromagnetic valves are as shown in fig. 3, pressure oil enters a system after passing through a throttling hole, as shown in thick lines in fig. 3, because the valve cores of the first electromagnetic valve 1, the second electromagnetic valve 2 and the third electromagnetic valve 3 block the pressure oil at inlets P of the electromagnetic valves, the whole pressure oil pipeline is in a pressure maintaining state, and at the moment, the pressure of the pressure oil pipeline behind the throttling hole plate is 0. Meanwhile, the pressure is arranged at the upstream of the first unloading valve 7 and the second unloading valve 8, and the safety oil and the plug are blocked at the downstream of the unloading valves under the combined action of the pressure of the upstream pressure oil and the pressure of the built-in spring of the unloading valves, so that the safety oil pressure is established in the whole system.

As shown in fig. 4, the main valve control state: the two-way electromagnetic valve 11 and the hydraulic control one-way valve 9 are connected in parallel, one end of the two-way electromagnetic valve 11 is electrified (the position of a valve core of the two-way electromagnetic valve 11 is shown in figure 4), the safety oil reaches the hydraulic control one-way valve 9 after passing through the two-way electromagnetic valve 11 and opens the valve core of the hydraulic control one-way valve 9, and the other path of safety oil enters the main valve operating seat 10 to open the main valve after passing through the hydraulic control one-way valve 9.

As shown in fig. 5, when the main throttle is closed: after the other end of the two-way electromagnetic valve 11 is electrified (the position of the valve core of the two-way electromagnetic valve 11 is shown in fig. 5), the oil pressure under the main valve operating seat 10 drops the safe oil pressure to an acceptable range through a thick line passage shown in fig. 5 and a preset adjustable throttle valve 12 to realize the closing of the main valve (namely, the tightness experiment function of the main valve can be realized).

As shown in fig. 6, in the experiment of blocking the solenoid valves on line, the corresponding load cells are added to the paths where the three solenoid valves of the first solenoid valve 1, the second solenoid valve 2 and the third solenoid valve 3 are connected in series two by two. The function of the whole interruption module cannot be influenced when only one electromagnetic valve acts due to the special connection mode of the three electromagnetic valves. Taking the first electromagnetic valve 1 as an example, when the first electromagnetic valve 1 is powered off after the online solenoid valve activity interruption experiment instruction is obtained, and the first electromagnetic valve 1 operates normally, the valve core position of the first electromagnetic valve 1 is as shown in fig. 6. At this time, the inlet P of the first solenoid valve 1 is conducted with the outlet B of the third solenoid valve 3, and the third solenoid valve 3 is charged and not operated, so that the pressure oil from the inlet P of the first solenoid valve 1 is kept at the outlet B of the third solenoid valve 3 (at this time, the pressure oil of the whole system is pressurized, so that the unloading valve is not operated, and the safe oil pressure is established), so that the pressure measurement point of the first pressure sensor 4 for boosting the pressure of the thick-line pipeline in fig. 6 will have a display. If the first pressure sensor 4 does not see the indication number in the process, the first electromagnetic valve 1 can be judged to be in fault. The same is true of the online experimental principle of the second solenoid valve 2 and the third solenoid valve 3.

As shown in fig. 7, when two solenoid valves are shut off: the valve core position of the electromagnetic valve is shown in fig. 7, pressure oil enters the system after passing through the throttling hole, the first electromagnetic valve 1 and the third electromagnetic valve 3 are in an open circuit state (without electricity) as shown in a thick line of fig. 7, the pressure oil reaches an outlet B of the third electromagnetic valve 3 through an outlet A of the first electromagnetic valve 1 and is discharged through an outlet T of the third electromagnetic valve 3, and at the moment, the pressure of a pressure oil path behind the throttling hole plate is 0. Meanwhile, the upstream of the first unloading valve 7 and the upstream of the second unloading valve 8 have no pressure, and the downstream safety oil overcomes the elastic force of a built-in spring of the unloading valve, directly connects the unloading valve after opening and returns oil, so that the system safety oil pressure is 0.

The invention can more effectively and reliably realize the steam turbine interruption function by adopting three electromagnetic valves, and can actively judge whether the electromagnetic valves are jammed or invalid through an online experiment, thereby prejudging the maintenance or danger. The main valve can be controlled through the two-way electromagnetic valve and the hydraulic control one-way valve, and unnecessary risks during debugging are reduced.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. The system is characterized by comprising a pressure oil path and a safety oil path, wherein the pressure oil path is respectively connected with three electromagnetic valves, one path of the safety oil path is connected with a forward oil outlet of a hydraulic control one-way valve, a forward oil inlet of the hydraulic control one-way valve is connected with a main throttle control seat, the other path of the safety oil path is connected with a two-way electromagnetic valve, and an outlet of the two-way electromagnetic valve is respectively connected with a control port of the hydraulic control one-way valve and the main throttle control seat; an unloading valve is arranged between the safety oil way and the pressure oil way, and two end interfaces of the unloading valve are respectively connected with the safety oil way or the pressure oil way.

2. The turbine critical trip and main valve control system of claim 1 wherein the solenoid valves are two-position two-way solenoid valves, each solenoid valve having an outlet and an inlet, the three solenoid valves having outlets and inlets connected in series, two-by-two, respectively.

3. The turbine critical trip and main valve control system of claim 1 wherein the solenoid valves comprise a first solenoid valve, a second solenoid valve and a third solenoid valve, the outlet of the first solenoid valve being connected to the inlet of the third solenoid valve, the outlet of the second solenoid valve being connected to the inlet of the first solenoid valve, the outlet of the third solenoid valve being connected to the inlet of the second solenoid valve.

4. The turbine emergency trip and main valve control system according to claim 3 wherein the outlets of the first solenoid valve, the second solenoid valve and the third solenoid valve are each connected to a pressure sensor via a pipeline.

5. The turbine emergency trip and main valve control system according to claim 1 wherein an inlet P of the solenoid valve is connected to the pressure circuit and an outlet T of the solenoid valve is connected to an oil drain.

6. The turbine emergency trip and main valve control system according to claim 1, wherein the number of said unloading valves is two, and two of said unloading valves are disposed in parallel between said pressure oil path and said relief oil path.

7. The turbine emergency shutdown and main valve control system according to claim 1, wherein an inlet P of the two-way solenoid valve is connected to the safety circuit and an outlet T of the two-way solenoid valve is connected to the adjustable throttle valve.

8. The turbine trip and main valve control system according to claim 1 wherein said two-way solenoid valve is a three-position, four-way reversing valve.

9. The turbine emergency trip and main valve control system according to claim 1 wherein when said two-way solenoid valve is in one operating position, safety oil enters a control port of said pilot operated check valve through working port a; when the two-way electromagnetic valve is at another working position, the safety oil in the main valve operating seat is discharged to the adjustable throttle valve from an outlet T through a working port A.

10. A method for using a steam turbine emergency shut-off and main valve control system is characterized by comprising the following steps:

s1, emergency shut-off of steam turbine

The three electromagnetic valves receive electric signals, the three electromagnetic valves are connected in series two by two, and any two electromagnetic valves act to unload pressure oil so that the unloading valve unloads system safety oil to realize steam turbine interruption;

s2, main valve control

The two-way electromagnetic valve and the hydraulic control one-way valve are connected in parallel, one end of the two-way electromagnetic valve is electrified, the safety oil reaches the hydraulic control one-way valve after passing through the two-way electromagnetic valve and opens a valve core of the hydraulic control one-way valve, and the other path of safety oil enters the main valve operating seat after passing through the hydraulic control one-way valve to open the main valve;

after the other end of the two-way electromagnetic valve is electrified, the safety oil under the main throttle control seat enters a preset adjustable throttle valve through the other passage of the two-way electromagnetic valve, so that the main throttle is closed when the safety oil pressure falls to an acceptable range;

s3, on-line shutoff solenoid valve experiment

Load cells are added on the paths of the three solenoid valves which are connected in series in pairs, when only one solenoid valve acts, the function of the whole blocking module cannot be influenced, after an online blocking solenoid valve activity experiment instruction is carried out, one solenoid valve is powered off, when the solenoid valve acts normally, the other solenoid valve connected in series with the solenoid valve is electrified and does not act, so that pressure oil from the solenoid valve is kept at the other solenoid valve, the pressure oil of the whole system is pressurized, an unloading valve does not act, safe oil pressure is established, a pipeline boosting load cell has an indication number, and if the load cell does not see the indication number in the process, the solenoid valve is judged to be broken down.

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