JP2008128442A - Valve apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a valve apparatus that can reduce throttle pressure loss by making valve opening large and that can perform rapid closing. <P>SOLUTION: This valve apparatus is provided with a valve main body 11; a valve body 14 accommodated inside the valve main body 11; a valve seat 13 provided inside the valve main body 11 to contact the valve body 14 when a valve is closed; a valve rod 15, which is connected to the valve body 14 and whose sliding portion passes through a valve lid 12 mounted on the valve main body 11; a valve cylinder 17, which stores a piston 16 connected to the valve rod 15 and moves the valve body 14 to the valve seat 13 for opening and closing by the movement of the piston 16 via the valve rod 15; and a closing spring 50, which is arranged inside the cylinder 17 and includes a first spring 21 and a second spring 23. The entire spring constant of the closing spring 50 is configured to become larger when the valve is opened further from predetermined midway opening than when the valve is opened from a totally closed state. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a valve device such as a steam control valve provided at a steam inlet of a steam turbine, for example.

  FIG. 6 is a system diagram of the steam turbine plant.

  The steam from the boiler 700 passes through the main steam stop valve 701 and the steam control valve 702 and works in the high-pressure turbine 710, and then is heated again by the reheater of the boiler 700 through the check valve 707 and reheated. The steam flows into the intermediate pressure turbine 711 and the low pressure turbine 712 through the steam stop valve 703 and the intercept valve 704 to work. After the low-pressure turbine 712, the water is returned to the condenser 713, boosted by the feed water pump 714, and circulated so as to be supplied to the boiler 700 again.

  In order to increase the operation efficiency of the plant, depending on the plant, a bypass provided with a high-pressure turbine bypass valve 705 connected between the steam inlet side of the main steam stop valve 701 and the reheat steam inlet side of the boiler 700, A bypass having a low-pressure turbine bypass valve 706 connected between the reheat steam outlet side of the boiler 700 and the condenser 713 is installed so that the boiler system can be circulated independently of the operation of the turbine. It has become.

  FIG. 7 is an explanatory diagram of a conventional steam valve device used in a steam turbine.

  A main steam stop valve 701 capable of instantaneously stopping steam flowing into the steam turbine in an emergency of the steam turbine, and a steam control valve 702 for controlling the steam flow rate are shown.

  The valve body 101 of the main steam stop valve 701 has a side portion thereof connected to the steam control valve 702 in communication. A valve lid 102 is provided at the upper end portion of the valve main body 101, and a valve seat 104 having a raised shape is provided at an inner portion of the valve main body 101, and a valve body 105 that contacts the valve seat 104 is accommodated. The valve rod 106 of the valve body 105 penetrates the valve body 101 and is incorporated in the oil cylinder 107. A piston 110 and a spring 109 are disposed in the oil cylinder 107, and an oil discharge port 108 that also serves as an oil supply port is provided at a lower portion of the piston 110. A hydraulic device such as a servo valve or a dump valve (not shown) is connected to the oil discharge port 108.

  The valve main body 201 of the steam control valve 702 has a side portion connected to the main steam stop valve 701 and has a valve lid 202 at the upper end of the valve main body 201, and has a raised shape in the inner part of the valve main body 201. A valve seat 203 is provided, and a valve body 204 that contacts the valve seat 203 is accommodated. A valve rod 205 of the valve body 204 is incorporated in the oil cylinder 207 through the valve lid 202. A piston 206 and a spring 209 are disposed in the oil cylinder 207, and an oil discharge port 208 that also serves as an oil supply port is provided in the lower portion of the piston 206. A hydraulic device such as a servo valve or a dump valve (not shown) is connected to the oil discharge port 208.

  A steam flow from a boiler or the like (not shown) causes the valve body 105 to move up and down via the valve rod 106 by the hydraulic pressure acting in the oil cylinder 107 of the main steam stop valve 701, and the main steam stop valve 701 opens and closes. The steam flows from the inlet I during the opening operation. Similarly, when hydraulic pressure acts in the oil cylinder 207, the valve body 204 moves up and down via the valve rod 205, and the steam control valve 702 performs an opening / closing operation, and the steam flow rate is controlled by the opening / closing operation. During the opening operation, steam flows out from the outlet O and flows to a steam turbine (not shown).

  FIG. 4 shows the quick closing time characteristics of the oil cylinder 207 when an emergency such as a load interruption occurs. The vertical axis is the stroke of the piston 206, and the horizontal axis is the fully open to fully closed state of the steam control valve 702. Represents the rapid closure time.

  Curve a in FIG. 4 shows the conventional characteristics. When a valve stroke fully open piston stroke is L1, when a rapid closing operation command is input from a steam turbine control device (not shown), a servo valve and a dump valve (not shown) are operated, and the lower portion of the piston 206 is moved by the restoring force of the spring 209 Oil is discharged from the oil discharge port 208, and the valve is fully closed after time T seconds.

  Note that the operation of the oil cylinder 107 of the steam stop valve 701 is the same as the operation of the steam control valve 702, and a description thereof will be omitted.

Here, the valve fully open means that when the valve seat diameter at which the valve body and the valve seat are in contact is Do and the stroke of the valve body is L, about L / Do = 0.2.
Is set to the upper limit. For this reason, the steam that passes through the steam passage formed between the valve body and the valve seat acts so as to be throttled by the valve body and the valve seat, and there is a throttle pressure loss at the portion.
Japanese Patent Laid-Open No. 9-72430

  Recent steam turbines are strongly required to improve performance (improve efficiency).

  By the way, as a breakdown of the efficiency of this steam turbine, there is also the internal efficiency of the steam turbine itself, but the steam turbine inlet before the steam valve throttle pressure loss installed at the inlet of the steam turbine does effective work in thermodynamics. As a result, the steam pressure of the steam turbine was lowered, and the steam turbine efficiency was greatly affected (decrease in efficiency).

  In order to reduce the throttle pressure loss of the steam valve, the valve opening may be increased. However, when an emergency such as a load interruption occurs in the steam turbine, it is necessary to shut off the steam flowing into the turbine in order to suppress the overspeed of the steam turbine, and the steam valve must be quickly closed in a short time. The valve opening cannot be increased without limit. In the conventional structure, it is necessary to increase the amount of oil supplied to the oil cylinder in order to open the valve widely, but it takes time to return the closing spring when the valve is suddenly closed. It took time and was unable to close quickly.

  An object of the present invention is to obtain a valve device that can reduce the throttle pressure loss by increasing the valve opening and can be quickly closed.

  In order to achieve the above object, a valve device according to the present invention includes a valve main body, a valve body accommodated in the valve main body, a valve provided in the valve main body and in contact with the valve body when the valve is closed. A valve rod connected to the seat, the valve body, and a sliding portion penetrating a valve lid attached to the valve body, and a piston coupled to the valve rod are housed, and the valve rod is moved by the movement of the piston. A cylinder for opening and closing the valve body with respect to the valve seat, and a closing spring disposed in the cylinder and including a first spring and a second spring, from when the valve is fully opened Further, the whole spring constant of the closing spring is increased at a valve opening larger than a predetermined intermediate opening.

  According to the present invention, the cylinder is provided with a closing spring that can close the valve rapidly even if the valve opening is increased, so that the valve opening can be increased and the throttle pressure loss can be reduced.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is an assembled sectional view of the valve device according to the first embodiment of the present invention. A steam control valve will be described as an example.

  The steam control valve 10 is connected to the valve body 11, a valve seat 13 having a raised shape on the inner side of the valve body 11, a valve body 14 in contact with the valve seat 13, and the valve body 14. A valve stem 15 having a moving portion and a valve lid 12 that allows the sliding portion of the valve stem 15 to penetrate the upper end portion of the valve main body 11 are provided.

  The valve body 14 is connected to a piston 16 in an oil cylinder 17 as a cylinder via a valve rod 15. A piston 16 is disposed in the oil cylinder 17, and a spring receiver 22 is disposed on the counter valve rod 15 side of the piston 16 and the end face side of the oil cylinder 17. A first spring 21 is disposed between the opposing surfaces of the spring receiver 22 and the piston 16. A second spring 23 having a spring constant that is, for example, twice that of the first spring 21 is disposed in series with the first spring 21 between the end surfaces of the spring receiver 22 and the oil cylinder 17. A stopper 24 integrated with the piston 16 facing the spring receiver 22 is provided on the side surface of the counter valve rod 15 of the piston 16. That is, in the present embodiment, the first spring 21, the second spring 23, the spring receiver 22, and the stopper 24 are provided on the counter valve rod side of the piston 16 in the oil cylinder 17 to form the closing spring 50. Yes. An oil discharge port 18 that also serves as an oil supply port is provided on the side surface of the oil cylinder 17 on the valve body 14 side, and hydraulic devices such as a servo valve and a dump valve (not shown) are connected to the oil discharge port 18.

  Further, in the valve device in the present embodiment, a part of the valve lid 12 is formed so as to protrude into the valve body 11, and the valve body 11 is accommodated when the valve body 11 is fully opened in the protruding portion. A chamber 30 is formed. The valve body 14 is formed with a recessed portion 142 having an edge 141 on the edge of the surface facing the valve seat 13.

  The steam flow from the boiler or the like flows from a steam stop valve (not shown) and flows out from the outlet O of the steam control valve 10. Since the restoring force of the closing spring 50 acts on the piston 16 in the oil cylinder 17, the hydraulic pressure from the hydraulic device acts on the piston 16 via the oil discharge port 18, or from the oil discharge port 18. When the oil flows out, the valve body 14 moves up and down via the valve rod 15, and the steam control valve 10 opens and closes. By the opening and closing operation, the steam flow rate is controlled and flows to a steam turbine (not shown).

  Here, the steam passage portion constituted by the valve body 14 and the valve seat 13 will be described with reference to FIGS.

The valve seat cross-sectional area (A1) at the valve seat diameter (Do) is A1 = π / 4 x Do ²
And is always a constant eigenvalue regardless of the stroke (L) of the valve body 14.

When the stroke of the valve body 14 is L, the steam passage cross-sectional area (A2) constituted by the valve body 14 and the valve seat 13 can geometrically determine the minimum value, that is, the minimum throttle cross-sectional area.

  That is, in FIGS. 2 and 3, an infinite number of truncated cones are virtually assumed in the steam passage formed by the valve body 14 and the valve seat 13, and a portion having the smallest outer surface area excluding the upper and lower bottom surfaces of the truncated cones. Is the minimum value in the stroke L, that is, the minimum throttle cross-sectional area, which is the steam passage cross-sectional area (A2), and is expressed by the following equation.

  Here, the radius of the bottom surface of the truncated cone is R1, the radius of the top surface is R2, and the height is h.

A2 = π x ((h ² + (R1−R2) ² ) ^1/2 x (R1 + R2)
From the above description, in the steam passage portion constituted by the valve body 14 and the valve seat 13, the minimum throttle portion is always set to the valve seat cross-sectional area (A 1) which is a constant eigenvalue at the fully opened valve opening. It is preferable to set.

In the present embodiment, the concept of full opening means a state in which the valve is opened larger than the full opening in the conventional device, and the stroke L of the valve element 14 is
L / Do ≧ 0.2
The range is set.

  Thereby, since the steam cross-sectional passage A2 constituted by the valve body 14 and the valve seat 13 becomes larger than the valve seat cross-sectional area A1 in the valve seat seat diameter, the throttle pressure loss can be reduced.

  As described above, if the stroke of the valve body 14 is increased, the opening degree of the valve body 14 can be opened larger than the full opening in the conventional device, but an emergency such as a load interruption occurs in the steam turbine. In this case, in order to suppress the overspeed of the steam turbine, it is necessary to shut off the inflowing steam, so it is necessary to close the steam valve quickly, so when the opening is larger than a predetermined halfway opening Moreover, the spring constant of the closing spring 50 installed in the oil cylinder 17 is made larger as a whole than the spring constant of the conventional spring.

  As described above, in the present embodiment, the closing spring 50 is configured by combining the first spring 21 and the second spring 23. When the valve body 14 is fully closed, if hydraulic pressure is applied from the oil discharge port 18 to the oil cylinder 17, the piston 16 starts to open while first compressing the first spring 21 mainly having a small spring constant. The valve is opened until the stopper 24 contacts the spring receiver 22. After the stopper 24 comes into contact with the spring receiver 22, the piston 16, the stopper 24, the spring receiver 22 and the first spring 21 are integrated (rigid body). Further, when hydraulic pressure acts on the piston 16, this time, the second spring 23 having a large spring constant is also operated to be compressed and opened.

  Thereby, the valve body 14 will be in a fully open state, as shown in FIG.

  FIG. 4 shows the quick closing time characteristic of the oil cylinder 17 when an emergency such as load interruption occurs. The vertical axis is the piston stroke, and the horizontal axis is from fully open to fully closed of the steam control valve 10. Represents rapid closure time.

  A curve b in FIG. 4 shows the characteristics in the present embodiment. Since the opening degree of the valve body 14 is larger than before, when the valve stroke of the fully opened piston stroke which increased the piston 16 of the oil cylinder 17 is L2, a rapid closing operation command is input from the control device of the steam turbine. Then, the servo valve and the dump valve communicating with the oil cylinder 17 are operated to open the oil discharge port 18, and the first spring 21 and the second spring 23 of the closing spring 50 are restored from the state shown in FIG. Due to the force, the piston 16 moves in the direction of the valve body, the oil in the oil cylinder 17 is discharged from the oil discharge port 18, and is fully closed after time T seconds.

Here, the quick closing time is set so that the curve a indicating the conventional characteristic and the curve b of the characteristic in the present embodiment are fully closed after the same time T seconds.

The curve b in FIG. 4 showing the characteristics in the present embodiment has a break point in the middle of the characteristics. This break point is a point of the piston stroke L0 until the stopper 24 comes into contact with the spring receiver 22 after the valve opening is started while the first spring 21 is mainly compressed.

That is, in the present embodiment, the second spring 23 having a large spring constant is added so that the rapid closing time is fully closed after the same T seconds as before, and the closing time due to the increase in piston stroke (L2-L1). The closing constant 50 as a whole is configured such that the spring constant becomes small at a valve opening that is less than or equal to a halfway opening. Furthermore, the impact force of the valve body 14 at the time of rapid closing acts on the valve seat 13, but since the closing speed is reduced in the vicinity of the fully closed state, the impact force acting on the valve seat 13 is greatly relieved.

On the other hand, the steam valve requires a large driving force to open the valve body 14 because the maximum differential pressure acts on the valve body 14 in the fully closed position immediately before the valve body 14 starts to open. In response to such a request, when a large restoring force by only the second spring 23 always acts from the fully closed point at which the valve body 14 starts to open, it is necessary to increase the diameter of the piston 16. However, in the present embodiment, the closing spring 50 is constituted by a plurality of combinations, and when the valve opening degree is small, the first spring 21 having a small spring constant is applied to reduce the spring constant as a whole. When the valve opening increases and the amount of steam passing downstream of the valve body 14 increases, the steam pressure makes it easier to move the valve body 14 in the opening direction. Thereafter, the second spring 23 having a large spring constant is obtained. It is comprised so that the restoring force of may act. Therefore, the caliber of the piston 16 does not change greatly and can be made the same as the conventional one.

  Thus, in the present embodiment, the valve can be quickly closed so that the steam turbine does not become overspeed when the load is interrupted. Since the valve can be quickly closed, the valve can be opened more greatly than the fully opened state of the conventional apparatus, and the throttle pressure loss of the steam control valve can be reduced. Thereby, the efficiency of a steam turbine can be improved.

  In the present embodiment, the spring constant of the second spring 23 is twice the spring constant of the first spring 21. However, it may be larger than the spring constant of the first closing spring. It is determined as appropriate according to the quick closing characteristics.

  FIG. 5 is an assembled sectional view showing the valve device according to the second embodiment of the present invention.

  In the first embodiment, the first spring and the second spring of the closing spring 50 are arranged in series, but in the present embodiment, the first spring and the second spring are arranged in parallel. The difference is that the spring 50 is used. The description of the same parts as in the first embodiment is omitted.

  The valve body 14 is connected to the piston 506 in the oil cylinder 507 via the valve rod 15. A piston 506 is disposed in the oil cylinder 507, and a closing spring 50 is provided on the counter valve rod side of the piston 506, as in the first embodiment. An integrated stopper 524 is provided on the counter valve rod 15 side of the piston 506. A first spring 521 is disposed between the stopper 524 and the end face of the oil cylinder 507. A spring receiver 522 is disposed outside the first spring 521 and between the stopper 524 and the end face of the oil cylinder 507. A second spring 523 having, for example, twice the spring constant of the first spring 521 is disposed in parallel with the first closing spring between the spring receiver 522 and the end face of the oil cylinder 507. That is, the closing spring 50 according to the present embodiment includes a first spring 521, a second spring 523, a spring receiver 522, and a stopper 524. An oil discharge port 508 that also serves as an oil supply port is provided on the side surface of the oil cylinder 507 on the valve body 14 side, and hydraulic devices such as a servo valve and a dump valve (not shown) are connected to the oil discharge port 508.

  When the valve body 14 is fully closed and the hydraulic pressure is applied to the oil cylinder 507 from the oil discharge port 508, the piston 506 first compresses the first spring 521 having a small spring constant among the closing springs 50. The valve opening is started, and the valve is opened until the stopper 524 contacts the spring receiver 522. After the stopper 524 comes into contact with the spring receiver 522, the piston 506, the stopper 524, and the spring receiver 522 are integrated. Further, when the hydraulic pressure acts on the piston 506, thereafter, the first spring 521 and the second spring 523 having a large spring constant are operated to be compressed and opened.

  Thereby, the valve body 14 will be in a fully open state, as shown in FIG.

  As a result, when the valve opening is larger than a predetermined halfway opening, the spring constant of the closing spring 50 as a whole is increased, so the same effect as in the first embodiment can be obtained.

  In the present embodiment, the spring constant of the second spring 523 is twice the spring constant of the first spring 521, but the closing spring has a valve opening larger than a predetermined halfway opening. The spring constant of the whole 50 should just become large, and it determines suitably according to the quick closing characteristic of a valve apparatus.

  In these embodiments, the spring in the explanatory diagram is drawn by a compression coil spring, but a more compact disc spring or the like may be used. Further, in each of the above embodiments, the closing spring is configured as two combinations of the first spring and the second spring. However, the closing spring is configured by appropriately combining two or more springs in series or in parallel. The overall spring constant may be changed in multiple stages.

  In these embodiments, a direct-acting structure in which the oil cylinder is directly connected to the valve rod is shown, but a drive mechanism via a lever may be used.

  In these embodiments, a structure is shown in which an edge 141 is formed at the tip of the valve body 14 for the purpose of preventing the occurrence of vibration. However, for example, by taking into account operational patterns, steam conditions to be used, etc. A normal spherical body, that is, a ball valve type may be used.

The assembly sectional view of the valve device concerning a 1st embodiment of the present invention. Explanatory drawing of the vapor | steam channel | path part of the valve apparatus which concerns on the 1st Embodiment of this invention. Explanatory drawing of the vapor | steam channel | path part of the valve apparatus which concerns on the 1st Embodiment of this invention. Explanatory drawing of the quick closing characteristic of the valve apparatus based on the 1st Embodiment of the past and this invention. The assembly sectional drawing of the valve apparatus which concerns on the 2nd Embodiment of this invention. The system diagram of a steam turbine plant. The assembly sectional view of the conventional integrated steam valve.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,702 ... Steam control valve, 11, 101, 201 ... Valve body, 12, 102, 202 ... Valve cover, 13, 104, 203 ... Valve seat, 14, 105, 204 ... Valve body, 15, 106, 205 ... Valve stem, 16, 110, 206, 506 ... Piston, 17, 107, 207, 507 ... Oil cylinder, 18, 108, 208, 508 ... Drain port, 21, 521 ... First spring, 22, 522 ... Spring receiver , 23, 523 ... second spring, 24, 524 ... stopper, 30 ... chamber, 50 ... closing spring, 109, 209 ... spring, 141 ... edge, 142 ... recessed portion, 700 ... boiler, 701 ... main steam stop valve 703 ... Reheat steam stop valve, 704 ... Intercept valve, 706 ... Low pressure turbine bypass valve, 707 ... Check valve, 710 ... High pressure turbine, 711 ... Medium pressure turbine, 712 ... Low pressure turbine , 713 ... condenser, 714 ... water pump, seat diameter of Do ... valve seat, I ... inlet, O ... outlet.

Claims (5)

A valve body;
A valve body housed inside the valve body;
A valve seat provided inside the valve main body and in contact with the valve body when the valve is closed;
A valve stem connected to the valve body, and a sliding portion penetrating a valve lid attached to the valve body;
A cylinder that houses a piston connected to the valve stem, and that moves the piston to open and close the valve body with respect to the valve seat via the valve stem;
A closing spring disposed in the cylinder and including a first spring and a second spring;
A valve device characterized in that an overall spring constant of the closing spring is increased with a valve opening larger than a predetermined halfway opening than when the valve is fully closed. The valve device according to claim 1, wherein the first spring and the second spring are arranged in series. The valve device according to claim 1, wherein the first spring and the second spring are arranged in parallel. When the stroke of the valve body is L and the seat diameter of the valve seat is Do, when the valve is fully open,
L / Do ≧ 0.20
The valve device according to any one of claims 1 to 3, wherein the valve device is set in a range of. The valve body has a stroke where the cross-sectional area of the portion formed between the valve body and the valve seat is a steam passage cross-sectional area, and the steam passage cross-sectional area is larger than the cross-sectional area of the valve seat. The valve device according to any one of claims 1 to 4, wherein the valve device moves.

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