A low bypass pressure reducing valve

Abstract

The present invention relates to a low bypass pressure reducing valve, comprising a valve body, a valve cover is arranged on the valve body, a valve cage is arranged in the valve body below the valve cover, a gas guide hole is provided on the valve cage, a main valve seat is arranged in the valve body below the valve cage, a main valve disc is arranged in the valve cage, a first groove is arranged at the bottom of the main valve disc, a guide cone is arranged in the first groove, and a first sealing ring gasket is arranged on the top of the main valve seat below the first groove. The technical problem of leakage behind the valve caused by direct impact and cavitation of the valve core and the valve seat sealing surface under the impetus of high-speed steam flow, resulting in internal leakage caused by loose closure, is solved. The present invention is easy to adjust and use, and has broad market prospects.

Description

Technical Field

[0001] The invention relates to the field of pressure reducing valves, and in particular to a low bypass pressure reducing valve. Background Art

[0002] The low bypass pressure reducing valve is an essential and important core equipment in the bypass system of large reheat steam turbine units. Its function is: before the unit is started, the reheat steam is first depressurized and then cooled to lead to the condenser without passing through the medium and low pressure cylinders, thus forming a steam circulation bypass to ensure the combustion of the boiler before the turbine is started, control the steam parameters of the unit, speed up the start-up time of the unit, improve the start-up conditions, and recover the working fluid at the same time. Large reheat steam turbine units are equipped with a bypass system, which is a regulation and protection system set up to adapt to the start-up and shutdown of the unit and accidents. Among them, the low bypass pressure reducing valve, as the core component of the low-pressure bypass, has become an essential and important equipment. Its function is to reduce the pressure of high-temperature and high-pressure steam first and then cool it to lead to the condenser without passing through the medium and low pressure cylinders, to ensure the combustion of the boiler before the turbine is started, to speed up the start-up time of the unit, improve the start-up conditions, recover the working fluid, and reduce noise. After the boiler is ignited and before the turbine is started, or when the turbine trips, the hot reheat steam bypasses the medium and low pressure cylinders of the turbine and is directly led to the condenser to protect the boiler reheater from overpressure and overtemperature. In addition, it can adapt to the unit's constant pressure and sliding pressure operation requirements, balance the boiler's steam production and the turbine's steam consumption, stabilize the operation of the boiler and turbine, and has safety adjustment functions such as startup and overflow.

[0003] After the unit is overhauled, the low bypass pressure reducing valve may not have internal leakage when it is just started, but after running for a period of time, along with the maintenance in the pipeline, welding is usually required during the maintenance process, and welding slag often falls into the pipeline. During the operation, along with the repeated opening and closing of the valve, the high-pressure airflow carries the welding slag and repeatedly impacts the sealing surface of the valve core. After the valve is operated several times, internal leakage occurs. This situation occurs repeatedly. After disassembling the valve with internal leakage, defects such as erosion and scratches on the sealing surface are often found. In order to improve the sealing effect of large-diameter valves in the prior art, large-diameter valves are mostly sealed by line sealing, that is, the valve disc and the valve seat are in contact with an annular sealing line. Such a process is conducive to improving the sealing effect. Since the boiler reheater and its affiliated system will inevitably produce welding slag impurities after maintenance even if the process is paid great attention to, and the low bypass pressure reducing valve is located at the end of the reheat system pipeline, when the unit starts to warm up the pipe, impurities enter the valve chamber. When the valve is closed, the impurities remaining on the inner surface of the pressure reducing cage are brought to the sealing surface by the valve core. The valve core sealing surface is the main flow surface. Since impurities and other particulates are mixed in the steam, they are directly impacted and cavitated by the high-speed steam flow on the valve core and the valve seat sealing surface, which leads to leakage behind the valve and causes the problem of internal leakage due to loose closure. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a low bypass pressure reducing valve capable of solving the problem of leakage behind the valve caused by direct impact and cavitation of the valve core and the valve seat sealing surface under the push of high-speed steam flow, so as to overcome the defects in the prior art.

[0005] The technical solution adopted by the present invention is: a low bypass pressure reducing valve, including a valve body, a valve cover is arranged on the valve body, a valve cage is arranged in the valve body below the valve cover, a gas guide hole is opened on the valve cage, a main valve seat is arranged in the valve body below the valve cage, a main valve disc is arranged in the valve cage, a first groove is opened at the bottom of the main valve disc, a guide cone is arranged in the first groove, and a first sealing ring gasket is arranged on the top of the main valve seat below the first groove.

[0006] Preferably, the first sealing ring gasket adopts a truncated cone annular structure, the first groove adopts a truncated cone groove structure, the slope of the outer side of the first sealing ring gasket is not less than the slope of the side wall of the first groove, the first sealing ring gasket is fixedly connected to the main valve disc, and a second groove is provided on the main valve disc outside the first sealing ring gasket.

[0007] Preferably, a hydraulic cylinder is arranged above the valve cover, a connecting protrusion is arranged below the valve cover, the hydraulic cylinder comprises a cylinder body and a telescopic rod, the connecting protrusion and the valve cover are both mounted on the telescopic rod of the hydraulic cylinder, a connecting device is arranged on the main valve disc, a third groove is opened at the bottom of the connecting protrusion, a second sealing ring gasket is mounted on the telescopic rod of the hydraulic cylinder in the third groove, the second sealing ring gasket and the telescopic rod of the hydraulic cylinder are movably connected, and the second sealing ring gasket and the third groove are threadedly connected.

[0008] Preferably, the guide cone includes a first part and a second part, the first part is located above the bottom surface of the main valve disc and adopts a cylindrical structure, and the second part is located below the bottom surface of the main valve disc and adopts a truncated cone structure.

[0009] Preferably, the first sealing ring gasket adopts an annular structure, an air flow hole is provided on the main valve seat, the air flow hole and the inner hole of the first sealing ring gasket are located on the same axis, the first sealing ring gasket is located on the outside of the guide cone, and the inner diameter of the first sealing ring gasket is not greater than the maximum diameter of the guide cone.

[0010] Preferably, a first connecting groove is opened on the top of the valve cage, the first connecting groove adopts an annular groove structure, a first connecting ring is installed in the first connecting groove, the top surface of the first connecting ring is fixedly connected to the bottom surface of the valve cover, and the first connecting groove and the first connecting ring are threadedly connected.

[0011] Preferably, the second groove adopts an annular groove structure, and the inner diameter of the second groove is not less than the outer diameter of the bottom of the first sealing ring gasket.

[0012] Preferably, the connecting device includes a second connecting groove, the second connecting groove is located at the top of the main valve disc, the free end of the telescopic rod of the hydraulic cylinder is located in the second connecting groove, a limit block is fixedly arranged on the free end of the telescopic rod of the hydraulic cylinder, and a second connecting ring is mounted on the telescopic rod of the hydraulic cylinder above the limit block, and the second connecting ring is threadedly connected to the second connecting groove.

[0013] The beneficial effects of the present invention are as follows: firstly, the present invention provides a first groove at the bottom of the main valve disc, a guide cone is fixedly arranged in the first groove, and a first sealing ring gasket is arranged on the top of the main valve seat below the first groove, thereby ensuring that at least part of the valve core sealing surface of the product will not be directly impacted by the high-speed steam flow, thereby solving the problem of leakage behind the valve caused by direct impact and cavitation of the valve core and the valve seat sealing surface under the push of high-speed steam flow, resulting in internal leakage caused by loose closing.

[0014] Secondly, the guide cone of the present invention includes a first part and a second part. The first part is located above the bottom surface of the main valve disc. The first part adopts a cylindrical structure. The diameter of the first part matches the inner diameter of the first sealing ring gasket. In the closed state, the first part and the first sealing ring gasket are tightly fitted, which is equivalent to adding a second sealing surface and improving the sealing effect. The second part is located below the bottom surface of the main valve disc. The second part adopts a truncated cone structure. Such a structure is conducive to guiding the high-pressure steam to pass through the air flow below to discharge the product through the hole, and the second part adopts a truncated cone structure, which is more conducive to reducing the direct contact between the high-pressure steam and the first part, reducing the loss of the first part and improving the durability of the product.

[0015] Finally, since the valve cage is directly impacted by high-temperature and high-pressure steam for a long time, it often needs to be replaced when starting and stopping. In order to facilitate the replacement of the valve cage, this product has a first connecting groove on the top of the valve cage. The first connecting groove adopts an annular groove structure. A first connecting ring is installed in the first connecting groove. The top surface of the first connecting ring is fixedly connected to the bottom surface of the valve cover, and the first connecting groove and the first connecting ring are threadedly connected.

[0016] The invention has the advantages of simple structure, convenient operation, ingenious design, greatly improved working efficiency, good social and economic benefits, and is a product that is easy to promote and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the present invention.

[0018] Figure 2 for Figure 1 A partial enlarged schematic diagram of detail A.

[0019] Figure 3 for Figure 1A partial enlarged schematic diagram of detail B.

[0020] Figure 4 for Figure 1 A partial enlarged schematic diagram of detail C.

[0021] Figure 5 It is a schematic diagram of the closed state of the present invention. DETAILED DESCRIPTION

[0022] like Figure 1 , 2 As shown in Figures 3 and 4, a low bypass pressure reducing valve comprises a valve body 1, a valve cover 2 is arranged on the valve body 1, the valve cover 2 and the valve body 1 are fixed by bolts, a valve cage 3 is arranged in the valve body 1 below the valve cover 2, the valve cage 3 and the main valve seat 5 are movably connected, a gas guide hole 4 is opened on the valve cage 3, a main valve seat 5 is arranged in the valve body 1 below the valve cage 3, the main valve seat 5 and the valve body 1 are fixedly connected, a main valve disc 6 is arranged in the valve cage 3, a first groove 7 is opened at the bottom of the main valve disc 6, a guide cone 8 is fixedly arranged in the first groove 7, and a first sealing ring gasket 9 is arranged on the top of the main valve seat 5 below the first groove 7.

[0023] A hydraulic cylinder 11 is arranged above the valve cover 2, and a connecting protrusion 12 is fixedly arranged below the valve cover 2. The hydraulic cylinder 11 includes a cylinder body and a telescopic rod. The cylinder body of the hydraulic cylinder 11 is fixed above the valve cover 2, and the connecting protrusion 12 and the valve cover 2 are both mounted on the telescopic rod of the hydraulic cylinder 11. A connecting device is arranged on the main valve disc 6, and a third groove 13 is opened at the bottom of the connecting protrusion 12. A second sealing ring gasket 14 is mounted on the telescopic rod of the hydraulic cylinder 11 in the third groove 13. The connecting protrusion 12 and the second sealing ring gasket 14 are respectively movably connected to the telescopic rod of the hydraulic cylinder 11, and the second sealing ring gasket 14 is threadedly connected to the third groove 13. The connecting device includes a second connecting groove 18, which is located at the top of the main valve disc 6. The free end of the telescopic rod of the hydraulic cylinder 11 is located in the second connecting groove 18. A limit block 19 is fixedly arranged on the free end of the telescopic rod of the hydraulic cylinder 11. A second connecting ring 20 is mounted on the telescopic rod of the hydraulic cylinder 11 above the limit block 19. The second connecting ring 20 is threadedly connected to the second connecting groove 18.

[0024] In order to reduce the impact of solid particles such as welding slag carried in the steam on the main valve disc 6 and the guide cone 8, and to minimize the damage to the sealing surface of the product caused by solid particles due to scratches and erosion when the product is in a closed state, the first sealing ring gasket 9 of the product adopts a truncated cone annular structure, and the first groove 7 adopts a truncated cone groove structure. The slope of the outer side of the first sealing ring gasket 9 is not less than the slope of the side wall of the first groove 7. The first sealing ring gasket 9 is fixedly connected to the main valve disc 6, and a second groove 10 is provided on the main valve disc 6 outside the first sealing ring gasket 9. As the high-pressure airflow passes through, most of the solid particles are discharged from the product along with the high-pressure airflow. A small number of solid particles that fail to pass through the product along with the high-pressure airflow will enter the second groove 10 after multiple rebounds of the contact surfaces of the first sealing ring gasket 9, the guide cone 8, the main valve disc 6 and the main valve seat 5 combined with the airflow dynamics, so as to be cleaned during maintenance. The second groove 10 preferably adopts an annular groove structure, and the inner diameter of the second groove 10 is not less than the outer diameter of the bottom of the first sealing ring gasket 9. Preferably, the inner diameter of the second groove 10 is equal to the outer diameter of the bottom of the first sealing ring gasket 9. This is more conducive to the solid particles contacting the side of the first sealing ring gasket 9 and directly sliding into the second groove 10.

[0025] In order to further improve the sealing effect, the first sealing ring gasket 9 of the product adopts an annular structure, and the main valve seat 5 is provided with an airflow hole 15. The airflow hole 15 and the inner hole of the first sealing ring gasket 9 are located on the same axis. The first sealing ring gasket 9 is located outside the guide cone 8, and the inner diameter of the first sealing ring gasket 9 is not greater than the maximum diameter of the guide cone 8. The guide cone 8 includes a first part and a second part. The first part is located above the bottom surface of the main valve disc 6. The first part adopts a cylindrical structure. The diameter of the first part matches the inner diameter of the first sealing ring gasket 9. In the closed state, the first part and the first sealing ring gasket 9 are tightly fitted, which is equivalent to adding a second sealing surface and improving the sealing effect. The second part is located below the bottom surface of the main valve disc 6. The second part adopts a truncated cone structure. Such a structure is conducive to guiding high-pressure steam to discharge the product through the airflow hole 15 below, and the second part adopts a truncated cone structure, which is more conducive to reducing the direct contact between high-pressure steam and the first part, reducing the loss of the first part, and improving the durability of the product.

[0026] Since the valve cage 3 is directly impacted by high-temperature and high-pressure steam for a long time, it often needs to be replaced when starting and stopping. In order to facilitate the replacement of the valve cage 3, this product has a first connecting groove 16 on the top of the valve cage 3. The first connecting groove 16 adopts an annular groove structure. A first connecting ring 17 is installed in the first connecting groove 16. The top surface of the first connecting ring 17 is fixedly connected to the bottom surface of the valve cover 2, and the first connecting groove 16 and the first connecting ring 17 are threadedly connected.

[0027] The use of this product is as follows: Figure 1 , 2 As shown in Figures 3 and 4, during the closing process, the hydraulic cylinder 11 drives the main valve disc 6 and the guide cone 8 to move downward. During this process, high-pressure steam enters the valve cage 3 through the gas guide hole 4, and the high-pressure steam contacts the second part of the guide cone 8. After being guided by the second part of the guide cone 8, the high-pressure steam passes through the product through the air flow hole 15. When the bottom surface of the main valve disc 6 contacts the top surface of the main valve seat 5, the closed state is reached. At this time, a first closing surface is formed between the bottom surface of the main valve disc 6 and the top surface of the main valve seat 5, and a second closing surface is formed between the first part of the guide cone 8 and the first sealing ring gasket 9.

[0028] Since a number of gas guide holes 4 are provided on the valve cage 3 body, the valve cage 3 itself has the function of screening solid particles. Solid particles that are too large will be filtered on the outside of the valve cage 3. During the opening process, the hydraulic cylinder 11 drives the main valve disc 6 and the guide cone 8 to move upward. In this process, the solid particles remaining in the valve cage 3 will have part of the welding slag enter the inner side of the valve cage 3 along with the high-pressure steam due to the instantaneous excessive airflow. An absolute part of the solid particles entering the inner side of the valve cage 3 will be discharged from this product along with the high-pressure steam. The remaining trace solid particles, under the combined effect of the driving force of the high-pressure steam and the outer wall of the first sealing ring gasket 9, enter the second groove 10 for temporary storage, so as to avoid staying on the top of the top surface of the main valve seat 5 and causing scratches and erosion damage to the bottom surface of the main valve disc 6 or the top surface of the main valve seat 5.

[0029] Through the embodiments, the problem of leakage behind the valve caused by direct impact and cavitation of the valve core and the valve seat sealing surface under the impetus of high-speed steam flow, resulting in loose closure and internal leakage, is solved. It should also be noted that for every 1t / h of steam leakage from the low bypass pressure reducing valve of a 300MW subcritical unit, the heat consumption rate increases by 4.0kJ / kWh and the coal consumption rate increases by about 0.37g / kWh. The amount of standard coal generated is calculated by referring to the annual power generation of the unit and the coal consumption affected by the 1t / h steam leakage of the low bypass pressure reducing valve, and the coal burning cost generated can be obtained by combining the average market unit price of standard coal. However, in actual production, the amount of internal steam leakage of the low bypass pressure reducing valve is not only 1t / h, so the elimination of internal leakage after research and implementation can generate considerable direct economic benefits.

[0030]

[0031] In addition, the leakage amount was counted based on the valves with leakage failures mentioned above.

[0032] name Valve with leakage Average leakage Average heat loss Using traditional structure 95 3t / h 6.0KJ / kWh This product 9 0.2t / h 0.3KJ / kWh

[0033] The present invention is a low bypass pressure reducing valve that meets the needs of workers in the pressure reducing valve field, so the present invention has a broad market prospect.

Claims

1. A low bypass pressure reducing valve, comprising a valve body (1), wherein a valve cover (2) is arranged on the valve body (1), and characterized in that: A valve cage (3) is arranged in the valve body (1) below the valve cover (2), a gas guide hole (4) is provided on the valve cage (3), a main valve seat (5) is arranged in the valve body (1) below the valve cage (3), a main valve flap (6) is arranged in the valve cage (3), a first groove (7) is arranged at the bottom of the main valve flap (6), a guide cone (8) is arranged in the first groove (7), and a first sealing ring gasket (9) is arranged on the top of the main valve seat (5) below the first groove (7); The first sealing ring gasket (9) adopts a truncated cone annular structure, the first groove (7) adopts a truncated cone groove structure, the slope of the outer side surface of the first sealing ring gasket (9) is not less than the slope of the side wall of the first groove (7), the first sealing ring gasket (9) and the main valve flap (6) are fixedly connected, and a second groove (10) is provided on the main valve flap (6) outside the first sealing ring gasket (9); A hydraulic cylinder (11) is arranged above the valve cover (2), a connecting protrusion (12) is arranged below the valve cover (2), the hydraulic cylinder (11) comprises a cylinder body and a telescopic rod, the connecting protrusion (12) and the valve cover (2) are both mounted on the telescopic rod of the hydraulic cylinder (11), a connecting device is arranged on the main valve flap (6), a third groove (13) is provided at the bottom of the connecting protrusion (12), a second sealing ring gasket (14) is mounted on the telescopic rod of the hydraulic cylinder (11) in the third groove (13), the second sealing ring gasket (14) and the telescopic rod of the hydraulic cylinder (11) are movably connected, and the second sealing ring gasket (14) and the third groove (13) are threadedly connected; The guide cone (8) comprises a first part and a second part, wherein the first part is located above the bottom surface of the main valve flap (6) and has a cylindrical structure, and the second part is located below the bottom surface of the main valve flap (6) and has a truncated cone structure; The first sealing ring gasket (9) adopts an annular structure, and an airflow hole (15) is provided on the main valve seat (5). The airflow hole (15) and the inner hole of the first sealing ring gasket (9) are located on the same axis. The first sealing ring gasket (9) is located outside the guide cone (8), and the inner diameter of the first sealing ring gasket (9) is not greater than the maximum diameter of the guide cone (8).

2. The low bypass pressure reducing valve according to claim 1, characterized in that: A first connecting groove (16) is provided on the top of the valve cage (3). The first connecting groove (16) is an annular groove structure. A first connecting ring (17) is mounted inside the first connecting groove (16). The top surface of the first connecting ring (17) is fixedly connected to the bottom surface of the valve cover (2). The first connecting groove (16) and the first connecting ring (17) are threadedly connected.

3. The low bypass pressure reducing valve according to claim 1, characterized in that: The second groove (10) is an annular groove structure, and the inner diameter of the second groove (10) is not less than the outer diameter of the bottom of the first sealing ring gasket (9).

4. The low bypass pressure reducing valve according to claim 1, characterized in that: The connecting device comprises a second connecting groove (18), the second connecting groove (18) is located at the top of the main valve disc (6), the free end of the telescopic rod of the hydraulic cylinder (11) is located in the second connecting groove (18), a limit block (19) is fixedly arranged on the free end of the telescopic rod of the hydraulic cylinder (11), a second connecting ring (20) is sleeved on the telescopic rod of the hydraulic cylinder (11) above the limit block (19), and the second connecting ring (20) is threadedly connected to the second connecting groove (18).

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