JP2006046331A - Steam valve, and steam turbine with steam valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase a flow rate of steam by the same opening/closing stroke and improve flow characteristics, in a multi-hole bypass valve and a steam valve incorporating a valve element of the multi-hole bypass valve in a valve element of a main steam stop valve. <P>SOLUTION: Multi-hole steam guide holes 8A formed in an annular wall part 7 of the valve element 3 of the bypass valve 3 are radially formed in a multi-stage around the center part of a channel 9 of the valve element 3, and the steam guide holes 8A are arranged in a staggered manner. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a steam turbine having a steam valve and a steam valve installed in a power plant, and more particularly to a main steam stop valve having a bypass valve.

  Conventionally, for example, in a thermal power plant or a nuclear power plant, when ultra-high temperature and ultra-high pressure steam generated by a steam generator at the start-up is partially supplied to a high-pressure turbine, an abnormally high thermal stress is generated in the metal of the paragraph However, the thermal deformation accompanying it occurs, causing cracks or breakage.

Therefore, in the operation of the steam turbine, in order to suppress the generation of this severe thermal stress, the steam control valve is fully opened from the start to the initial load, and the steam flow is controlled by the main steam stop valve, so-called all-round injection. Operation is performed and warm-up operation is performed.
For this reason, the main steam stop valve employs a structure for controlling the steam flow rate.

  FIG. 9 is a diagram showing a conventional main steam stop valve. A valve body 3 of a bypass valve is built in the valve body 2 of the main steam stop valve 1, and a steam control valve (not shown) is fully opened when the steam turbine is started. At the same time, the valve body 2 of the main steam stop valve 1 is brought into contact with the valve seat 4 to be fully closed, and only the valve body 3 of the bypass valve is operated to control the steam flow rate.

  Since this bypass valve is built in the valve body 2 of the main steam stop valve 1, the valve body 3 is pushed up against the steam flow 5 by the valve rod 6 arranged on the downstream side of the steam flow 5 indicated by the arrow ( In this way, the opening degree of the valve is adjusted.

  Further, since this bypass valve controls the flow rate of the high-pressure steam by the minute lift of the valve body 3, the flow velocity of the steam passing through the bypass valve is considerably large.

  When high-speed steam passes through the bypass valve, a small amount of heavy material such as drain or oxide contained in the steam may collide with the valve, and the valve body 3 and the valve stem 6 may be eroded.

  If the valve body 3 or the valve stem 6 is damaged by this erosion action, the damaged valve body 3 or the stem of the valve stem 6 may collide with the nozzles or blades of the turbine on the downstream side to cause damage. (For example, refer to Patent Document 1).

  In order to solve this problem, an improved main steam stop valve as shown in FIGS. 10 and 11 has been conventionally considered.

  As shown in FIGS. 10 and 11, the valve body 2 of the main steam stop valve has a substantially cylindrical shape, and the same substantially cylindrical bypass valve is integrally connected to the valve stem 6 in the valve body 2. The valve body 3 is incorporated so that it can slide freely and its upper end protrudes from the upper end of the valve body 2.

  An annular wall portion 7 is formed in a portion of the bypass valve body 3 protruding from the upper end of the valve body 2, and the upper end thereof is closed. A plurality of steam introduction holes 8 parallel to the flow direction of the steam flow 5 are formed in the annular wall portion 7 in multiple stages.

FIG. 10 shows a state in which the valve body 2 of the main steam stop valve is in contact with the valve seat 4 and is closed, and the valve body 3 of the bypass valve is pushed up to the top in the valve body 2 by the valve rod 6. The steam introduction hole 8 part formed in the annular wall part 7 of this is completely protruding from the upper end of the valve body 2, and the bypass valve is fully opened.
Such a bypass valve is called a porous MSV bypass valve because a plurality of steam introduction holes 8 are formed.

  In the main steam stop valve configured in this way, as indicated by an arrow, the steam flow 5 flows into a large number of steam introduction holes 8 of the valve body 3 at a considerable flow rate, and the steam that has passed through the steam introduction holes 8. And collide with each other in the space inside the annular wall 7 with the steam flowing in through the steam introduction hole formed on the opposite side, where the velocity energy of the steam is relaxed and the flow velocity becomes low.

  The steam flow 5 having a low flow velocity passes through the flow path 9 in the valve body 3 of the bypass valve, temporarily recovers the pressure, passes through the plurality of steam holes 10 formed on the downstream side of the valve body 3, Furthermore, it flows toward the nozzles and blades of the turbine on the downstream side.

  In this way, the steam flow 5 flowing into the valve body 3 through the steam introduction hole 8 relaxes the velocity energy and becomes a low flow rate here, so that a very small amount of drain or oxide contained in the steam is valved. Even if it collides, the valve body 3 and the valve stem 6 will not be eroded.

  When adjusting the flow rate of steam by opening and closing the valve during the all-round injection operation of the steam turbine, if the valve rod 6 is lowered downward in the direction of the arrow X from the state shown in the drawing, the integrally connected valve body 3 is also It moves downward while sliding in the valve body 2.

  Along with this, the steam introduction hole 8 formed in the annular wall portion 7 of the valve body 3 is sequentially drawn into the valve body 2 from below, and the opening area of the entire steam introduction hole 8 through which the steam flow 5 passes is reduced. The steam flow can be reduced.

  Conversely, if the valve rod 6 is pushed upward along the opposite arrow X direction, the steam introduction holes 8 are sequentially pushed out from the valve body 2 and the opening area of the entire steam introduction hole 8 through which the steam flow 5 passes is expanded. As a result, the flow rate of the steam can be increased.

Reference numeral 11 denotes, for example, a rectangular groove formed at two locations on the outer peripheral surface of the valve body 3, and the projections 12 formed at two locations on the inner peripheral surface of the valve body 2 are engaged with each other so as to stop the two Plays.
Japanese Patent Publication No. 61-57442

  The bypass valve in the conventional main steam stop valve shown in FIG. 9 has problems such as erosion due to the collision of drain and oxide, but when viewed from the flow characteristics as a steam valve, the relationship between the bypass valve lift and the steam flow is The characteristic curve A is as shown in FIG.

  On the other hand, in the bypass valve in the improved conventional main steam stop valve shown in FIG. 10 and FIG. 11, the steam flow rate is controlled by moving the valve body 3 up and down via the valve rod 6. The opening area of the steam introduction holes 8 formed in multiple stages is changed.

  The steam introduction holes 8 formed in parallel to the steam flow 5 are inevitably formed in multiple stages over a long range in the vertical direction in order to obtain a sufficient steam circulation area necessary for the steam flow. However, the opening area must be increased.

  Along with this, the opening area of the steam introduction hole 8 is adjusted to control the flow rate of the steam. Therefore, it becomes necessary to take a large opening / closing stroke of the valve body 3 of the bypass valve, and the stroke operation becomes unstable. The valve becomes larger.

  The relationship between the bypass valve lift and the steam flow rate is as shown in the characteristic curve B of FIG. 8. In terms of the flow rate characteristic of the steam valve, the steam flow rate is even at twice the opening / closing stroke of the main steam stop valve shown in FIG. There are few flow characteristics.

  On the other hand, when the throttle control is performed at the start of the turbine generator with the main steam stop valve having the above-described configuration, measures may be taken by replacing the existing one with an improved one. In that case, the improved type has a problem that the flow rate of the all-round injection operation cannot be secured sufficiently as described above.

  Further, since the steam flow velocity at the inlet portion of the steam introduction hole 8 is rapidly increased as compared with other portions, this inlet portion is most easily eroded.

  In addition, the conventional main steam stop valve has a structure in which the entire valve is supported by the valve body 3 of the bypass valve built in the valve body 2 and the rotation is supported by the two grooves for preventing rotation. When the valve body 2 is fully opened and the valve body 2 is fully opened, the valve body 2 is swung by the flow of steam, and the sliding portion is worn by vibration.

  Furthermore, since the sliding part of the valve body 2 and the valve body 3 is a contact between large cylinders, the contact area is inevitably increased, foreign matters are easily caught in the gaps between the contact surfaces, and a stick phenomenon due to the foreign matter biting also occurs. easy.

  The present invention was made to solve the above problems, and shortened the opening / closing stroke of the valve body by shortening the length in the vertical direction of the steam introduction hole portion formed in the valve body of the bypass valve, It is another object of the present invention to provide a steam turbine having a steam valve and a steam valve which increases the stability of the valve body support structure of the entire main steam stop valve and prevents foreign matter from entering between the valve bodies. .

  In order to achieve the above object, the steam valve of the present invention is slidably incorporated in a valve seat, a valve body of a main steam stop valve capable of contacting the valve seat, and a valve body of the main steam stop valve. The annular wall portion protruding from the valve body of the main steam stop valve at a fully open position of the valve, and a plurality of steam introduction holes through which the steam flows are formed in the annular wall portion, and the steam that has passed through the steam introduction hole In the steam valve comprising a bypass valve body having a flow path for guiding the steam, the steam introduction holes are formed in multiple stages radially around the center of the flow path, and the arrangement of the steam introduction holes is staggered It is characterized by that.

  According to the steam valve and the steam turbine provided with the steam valve of the present invention, the length in the vertical direction of the steam introduction hole portion formed in the valve body of the bypass valve is shortened, and the opening / closing stroke of the valve body can be shortened.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description of the embodiment, the same parts as those of the conventional steam valve shown in FIGS. 10 and 11 are denoted by the same reference numerals, and detailed description thereof is omitted.

  1 and 2 are sectional views showing a steam valve according to a first embodiment of the present invention. In particular, FIG. 1 is a longitudinal front view, and FIG. 2 is a sectional view taken along line II-II in FIG. In FIG. 1, reference numeral 8A denotes a plurality of steam introduction holes formed so that the steam flow 5 passes through the annular wall portion 7 of the valve body 3 of the bypass valve. The steam introduction holes 8A are an enlarged side view of FIG. As shown in the enlarged cross-sectional view of FIG. 4, it is formed radially and in multiple stages around the center of the flow path 9 in the valve body 3.

  Further, the steam introduction holes 8A in each stage or each row are formed in a staggered arrangement.

  Of the outer peripheral surface of the annular wall 7 of the valve body 3, the outer peripheral surface 13 excluding the steam introduction hole 8 </ b> A portion is called a stellite (registered trademark) alloy and is a cobalt-based alloy having high wear resistance and oxidation resistance. (First example of component composition; Ni-3% or less, Cr-28%, W-4%, Fe-3% or less, C-1%, Co-balance, second example of component composition; Ni-2.5% , Cr-27%, Mo-5%, Fe-2% or less, C-0.25%, Co-remaining) and other surface treatments such as overlay welding, and sliding contact with the valve body 3 of the bypass valve Similarly, the inner peripheral surface 14 of the valve body 2 of the steam stop valve is subjected to a surface treatment such as overlay welding with a cobalt-based alloy. As overlay welding methods for cobalt-based alloys, oxygen acetylene method, TIG (Tungsten Inert Gas) method, coated arc method, PTA (Plasma Transferred Arc) method, laser method and cobalt-based hard alloy using cobalt-based hard alloy welding wire There are means for forming a hard alloy layer by thermal spraying or applying powder, and the like, which is appropriately selected according to the respective characteristics depending on the structure, shape, dimensions, and material of the workpiece.

For example, rectangular grooves 11 are formed at four locations on the outer peripheral surface of the valve body 3 that are spaced apart at equal intervals, and projections 12 formed at four locations on the inner peripheral surface of the valve body 2 are engaged with the grooves 11. , Has played a stop around both.
Furthermore, a plurality of escape grooves 15 are formed on the outer peripheral surface of the valve body 3.

  According to the steam valve according to the present embodiment configured as described above, the steam introduction holes 8A are arranged in a staggered arrangement and are formed radially, so that the total number of the steam introduction holes 8A in the same opening / closing stroke of the valve body 3 is increased. The area can be increased by about 30% compared to the conventional ratio.

  As a result, 30% more steam flows in terms of the flow rate characteristic of the steam, so that the characteristic curve C is improved with respect to the conventional characteristic curve B shown in FIG.

  Thereby, the steam flow of substantially the same amount can be flowed only by doubling the opening / closing stroke of the bypass valve with respect to the conventional steam valve shown in FIG.

  This is within an allowable range when replacing existing components. Therefore, by providing a steam introduction hole 8A in a staggered or radial arrangement, the stroke can be doubled even if it is replaced with a valve that can prevent erosion. It is possible to flow almost the same amount of steam.

  In addition, since the outer periphery of the annular wall portion 7 of the valve body 3 is surface-treated with stellite metal, it is possible to prevent erosion at the portion of the steam introduction hole 8A where the flow velocity of the steam is increased.

  Furthermore, the four protrusions 12 provided on the valve body 2 and the four grooves provided on the valve body 3 of the bypass valve mesh with each other so that the valve body 2 is supported by the valve body 3 of the bypass valve when the valve body 2 is fully opened. Although there is a body 2, the support structure is very stable.

  In addition, the sterite metal surface-treated inside the valve body 2 can increase the oxidation resistance of this portion, thereby reducing the clearance of the portion, which also contributes to improving the stability, As a result, wear at the sliding portion can be avoided.

  Further, by providing a plurality of relief grooves 15 in the valve body 3 of the bypass valve, foreign matter that has entered the sliding portion from the upper part flows into the escape groove 15 and flows downstream therethrough. It is possible to avoid mixing foreign objects between them, and stick phenomenon can be avoided.

  Furthermore, in the steam valve according to the present embodiment, the arrangement of the plurality of steam introduction holes 8A formed in the annular wall portion 7 of the valve body 3 of the bypass valve may be a modified example as shown in FIG. . FIG. 5 is an enlarged side view of the annular wall portion 7 of the bypass valve according to the modification of the present embodiment, in which the steam introduction holes 8A are arranged more densely.

  In this modification, not only the arrangement of the steam introduction holes 8A is a staggered arrangement, but the intervals between the rows of the steam introduction holes 8A arranged in the circumferential direction are reduced. Accordingly, the row of steam introduction holes 8A arranged in the horizontal direction is configured to overlap with the row of adjacent steam introduction holes 8A in the vertical direction.

  The steam flow rate from the bypass valve is adjusted by moving the valve body 3 of the bypass valve up and down. As shown in FIG. 3, the row of steam introduction holes 8 </ b> A arranged in the circumferential direction on the annular wall portion 7 and this When there is a vertical width between the steam introduction holes 8A adjacent to the row, the flow rate does not change even when the valve body 3 of the bypass valve is moved up and down in this portion. There is a possibility that the relationship becomes a fine step and affects the controllability.

  The modified example of FIG. 5 is for preventing this, and the arrangement of the steam introduction holes 8A formed in the annular wall portion 7 is the same as the steam introduction holes adjacent to the row of the steam introduction holes 8A arranged in the horizontal direction. Since it overlaps with the 8A row in the vertical direction, the relationship between the bypass valve lift, the bypass valve and the flow rate of the steam passing therethrough can be made closer to a straight line to improve the controllability.

  In the modification of FIG. 5, the shape of the steam introduction hole 8A is circular, but a more linear flow rate characteristic can be obtained by appropriately modifying the shape and the width of the overlap.

Next, a second embodiment of the present invention will be described with reference to FIGS.
As shown in FIGS. 6 and 7, the annular wall portion 7 of the valve body 3 is formed by a combination of a plurality of laminated annular thin plates 16 and a plurality of spacing plates 17 interposed between the annular thin plates 16. The gap formed by the spacing plate 17 and the annular thin plate 16 functions as the steam introduction hole 8.

  Each plate is fixed integrally by welding or the like, and if the plate thickness, assembly dimensions, etc. are designed so that the strength as a steam valve can be maintained, the area of the steam passage can be further increased.

  Thereby, the relationship between the opening / closing stroke of the valve body 3 and the flow rate characteristic is improved as shown by the characteristic curve D in FIG. 8, and the opening / closing stroke can be further shortened.

  Further, as shown in FIG. 7, if a projection plate 18 is provided in the middle of the spacing plate 17 interposed between the annular thin plates 16, the steam flow here relaxes the velocity energy. Thus, the speed becomes low, and coupled with the relaxation action due to the collision of the steam described above, the steam flow can be moderated to further prevent the erosion action.

  Further, since the velocity energy of the steam is gradually relaxed, noise at the time of starting the steam turbine can be reduced.

1 is a longitudinal front view showing a steam valve according to a first embodiment of the present invention. Fig. 2 is a cross-sectional plan view of Fig. 1 cut along the line II-II and viewed in the direction of the arrows. FIG. 3 is an enlarged side view of a steam introduction hole portion when FIG. 1 is viewed in the direction of arrow III. FIG. 4 is an enlarged cross-sectional plan view of FIG. 1 cut along line IV-IV and viewed in the direction of the arrow. The expanded side view which shows the modification of the steam introduction hole part shown in FIG. The expanded side view of the steam introduction hole part of the steam valve by the 2nd Embodiment of this invention. The top view which shows the modification of the 2nd Embodiment of this invention. The characteristic view which shows the relationship between a steam valve stroke and a steam flow rate. The longitudinal cross-sectional front view which shows an example of the conventional steam valve. The longitudinal cross-sectional front view which shows an example of the conventional further improved steam valve. FIG. 11 is a cross-sectional plan view of FIG. 10 cut along the line XX and viewed in the direction of the arrow.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Main steam stop valve, 2 ... Valve body of main steam stop valve, 3 ... Valve body of bypass valve, 4 ... Valve seat, 5 ... Steam flow, 6 ... Valve rod, 7 ... Annular wall part, 8, 8A ... Steam introduction hole, 9 ... flow path, 10 ... steam hole, 11 ... groove, 12 ... projection, 13 ... outer peripheral surface excluding steam introduction hole, 14 ... peripheral surface of valve body, 15 ... escape groove, 16 ... annular thin plate, 17 ... interval plate, 18 ... projection plate.

Claims (8)

  A valve body, a valve body of a main steam stop valve that can come into contact with the valve seat, and a valve body of the main steam stop valve that is slidably incorporated in the valve body of the main steam stop valve. A bypass valve body having an annular wall portion protruding from the inner wall, a plurality of steam introduction holes through which the steam flows are formed in the annular wall portion, and a passage for guiding the steam that has passed through the steam introduction hole. A steam valve comprising: the steam inlet holes formed radially in multiple stages around the center of the flow path, and the steam inlet holes arranged in a staggered arrangement.   The steam valve according to claim 1, wherein the surface of the annular wall portion of the valve body of the bypass valve is surface-treated with a cobalt-based alloy.   2. The steam valve according to claim 1, wherein the annular wall portion is constituted by a combination of an annular thin plate and a spacing plate, and the steam introduction hole is formed by a gap formed by the spacing plate and the annular thin plate.   The sliding portion between the valve body of the bypass valve and the valve body of the main steam stop valve has at least four anti-rotation portions formed of a combination of grooves and protrusions along the outer periphery thereof. The steam valve according to claim 1.   The steam valve according to claim 1, wherein the inner peripheral surface of the valve body of the main steam stop valve is surface-treated with a cobalt-based alloy.   2. The steam valve according to claim 1, wherein an escape groove into which foreign matter flows is formed on an outer peripheral surface of a valve body of a bypass valve that slides with an inner peripheral surface of the valve body of the main steam stop valve.   The steam introduction hole is formed by arranging a plurality of rows of steam introduction holes arranged in the circumferential direction in the vertical direction, and the row of the steam introduction holes overlaps with the row of adjacent steam introduction holes in the vertical direction. The steam valve according to claim 1, wherein the steam valve is arranged.   A steam turbine comprising the steam valve according to claim 1.

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