Middle cavity double-sealing structure for stop valve and stop valve using same

Abstract

The invention belongs to a middle cavity double-sealing structure for a stop valve, and particularly relates to a middle cavity double-sealing structure which is suitable for a nuclear-grade helium stop valve of a high-temperature gas cooled reactor nuclear power station and meets the requirement for the low leakage rate, and a stop valve using the middle cavity double-sealing structure. The invention elaborates the structural characteristics of the double-seal design of the middle cavity for the stop valve in detail. According to the middle cavity sealing structure of the stop valve under the helium working condition, the metal C-shaped rings, the constant stress gaskets and the corrugated pipes are arranged between the valve body and the pressing ring and between the pressing ring and the two leakage channels of the valve cover respectively to form double sealing, so that the middle cavity sealing structure of the stop valve has good sealing performance; the high sealing requirement of a high-temperature gas cooled reactor for the sealing structure of the middle cavity of the nuclear-grade helium stop valve is met. Meanwhile, by means of the double-sealing structure of the middle cavity of the stop valve, the double-sealing structure can be popularized and applied to other similar valves with the low leakage rate requirement for middle cavity sealing.

Description

Technical Field

[0001] The invention belongs to a double sealing structure for the middle cavity of a globe valve, and particularly relates to a double sealing structure for the middle cavity of a nuclear-grade helium globe valve applicable to a high-temperature gas-cooled reactor nuclear power plant that meets the low leakage rate requirement, and a globe valve using this structure. Background Art

[0002] As a pressure-bearing device with a large quantity and wide range in the primary loop of a high-temperature gas-cooled reactor, the nuclear-grade helium globe valve connects numerous process systems and plays an important role in ensuring the normal and stable operation and safety of the high-temperature gas-cooled reactor. It belongs to a key device in the high-temperature gas-cooled reactor. However, as the coolant in the primary loop, the medium helium gas of the nuclear-grade helium globe valve in the high-temperature gas-cooled reactor will carry certain radioactivity. If the medium helium gas leaks externally, it will cause pollution to the surrounding environment and pose certain hazards to on-site operators. Moreover, due to the strong permeability of helium gas, this puts very high requirements on the sealing performance of the middle cavity sealing structure of the helium globe valve. And because the high-temperature gas-cooled reactor belongs to the fourth-generation nuclear power reactor type, relatively high requirements are put forward for the sealing performance of the middle cavity sealing structure of the nuclear-grade helium globe valve. The middle cavity sealing structure of the traditional globe valve can achieve a certain sealing effect, but it cannot meet the sealing leakage rate requirements put forward for the middle cavity sealing structure of the nuclear-grade helium globe valve in the high-temperature gas-cooled reactor. Since there are many nuclear-grade helium globe valves in the primary loop of the high-temperature gas-cooled reactor, if the sealing performance of the middle cavity sealing structure cannot meet the requirements, the leakage rate will far exceed the system requirements, thus affecting the stable operation and safety of the high-temperature gas-cooled reactor. Summary of the Invention

[0003] The purpose of the invention is to provide a double sealing structure for the middle cavity of a globe valve that meets the low leakage rate requirement under high-temperature and high-pressure helium conditions, namely a double sealing structure of a metal C-ring and a constant stress gasket + bellows.

[0004] The structural technology for realizing the purpose of the invention: A double sealing structure for the middle cavity of a globe valve, which includes a pressing ring. The cross-section of the pressing ring is a hollow circular ring-shaped part. There is a convex platform on the bottom surface of the pressing ring. A constant stress gasket is arranged above the convex platform of the pressing ring, and a metal C-ring is arranged below the convex platform of the pressing ring.

[0005] For a double sealing structure for the middle cavity of a globe valve as described above, a groove is arranged on the metal C-ring.

[0006] For a double sealing structure for the middle cavity of a globe valve as described above, the groove on the metal C-ring is such that the width of the annular groove needs to ensure that the metal C-ring can be normally placed, and it is necessary to ensure that there is enough width so that the bottom plane of the groove can obtain a surface roughness of Ra 0.8 or more through grinding means. The depth of the annular groove is determined according to the wire diameter of the metal C-ring, and this depth needs to ensure the compression amount of the metal C-ring so that it has good resilience performance.

[0007] A double-sealing structure for the middle cavity of a globe valve as described above, wherein the surface roughness Ra of the groove on the metal C-ring and the bottom surface of the pressing ring ranges from less than Ra0.8.

[0008] A double-sealing structure for the middle cavity of a globe valve as described above, wherein the constant-stress gasket is of a double-ring structure, with the inner ring made of metal and the outer ring made of graphite.

[0009] A globe valve using the double-sealing structure for the middle cavity as described above, wherein the double-sealing structure for the middle cavity is used, the double-sealing structure for the middle cavity is arranged between the valve body and the valve cover, and the pressing ring is sleeved on the valve stem.

[0010] A globe valve using the double-sealing structure for the middle cavity as described above, wherein a corrugated pipe is sleeved outside the valve stem, and the pressing ring is sleeved on the corrugated pipe.

[0011] The remarkable effect of the present invention is that it improves the sealing performance of the sealing structure of the middle cavity of the valve, reduces the possibility of sealing failure of the middle cavity, so as to meet the relatively high sealing requirements for the middle cavity sealing structure of the nuclear-grade helium globe valve in the high-temperature gas-cooled reactor. Description of the Drawings

[0012] Figure 1 It is an assembly drawing of a double-sealing structure for the middle cavity of a globe valve

[0013] Figure 2 It is a structural drawing of a double-sealing structure for the middle cavity of a globe valve

[0014] Figure 3 It is a structural drawing of the constant-stress gasket

[0015] In the figure: 1. Valve body; 2. Corrugated pipe; 3. Metal C-ring; 4. Pressing ring; 5. Constant-stress gasket; 6. Valve cover; 7. Valve stem; 8. Middle flange nut; 9. Middle flange stud; Detailed Embodiments

[0016] 1. A double-sealing structure for the middle cavity of a globe valve

[0017] The assembly drawing of the double-sealing structure for the middle cavity of the globe valve is shown in Figure 1 .

[0018] The structural drawing of the double-sealing structure for the middle cavity of the globe valve is shown in Figure 2 .

[0019] 2. Structural Features of the Design of the Double-sealing Structure for the Middle Cavity

[0020] The double-sealing structure for the middle cavity of this globe valve adopts a structure combining a metal C-ring, a constant-stress gasket and a corrugated pipe. There are two leakage channels in the middle cavity sealing structure of the helium globe valve, including those between the valve body and the pressing ring and between the pressing ring and the valve cover. The specific working principle is as follows:

[0021] When the valve cavity is filled with helium, the seal between the valve body and the pressure ring is ensured by a metal C-ring. The annular groove on the valve body for placing the metal C-ring is designed in detail. The width of the annular groove should ensure that the metal C-ring can be properly placed and has enough width to enable the bottom plane of the groove to obtain a roughness of Ra above 0.8 through grinding. The depth of the annular groove is determined according to the wire diameter of the metal C-ring. This depth should ensure the compression amount of the metal C-ring so that it has good resilience. By applying the tightening torque of the middle flange stud, the compression amount and resilience of the metal C-ring are effectively ensured. At the same time, ensure that the surface roughness Ra of the bottom of the valve body groove and the bottom of the pressure ring in contact with the metal C-ring to form a seal (the metal C-ring contacts the bottom plane of the valve body annular groove and the bottom plane of the pressure ring respectively to form a sealing surface. In order to make the metal C-ring play a good sealing effect, it is necessary to ensure that the roughness of the bottom plane of the valve body annular groove and the bottom plane of the pressure ring reaches less than Ra0.8), which can make the metal C-ring play a better sealing effect to meet the leakage rate index requirements. The seal between the valve cover and the pressure ring is ensured by a constant stress gasket and a bellows. When the valve cavity is filled with helium, the medium helium is first sealed by the bellows, and the constant stress gasket acts as the second seal. The constant stress gasket adopts a structure of inner ring metal + outer ring graphite (attached Figure 3 ), and the inner ring metal mainly prevents the graphite from overpressure and causing the sealing gasket to fail, and the outer ring graphite can play the role of backup seal. Thus, a double-sealing structure for the middle cavity of the globe valve is formed.

Claims

1. A double sealing structure for a center cavity of a stop valve, characterized in that: The pressure ring (4) comprises a pressure ring (4) having a cross section of a hollow circular ring-shaped part, a boss being arranged on the bottom surface of the pressure ring (4), a constant stress gasket (5) being arranged above the boss of the pressure ring (4), and a metal C-shaped ring (3) being arranged below the boss of the pressure ring (4).

2. A double sealing structure for a stop valve as claimed in claim 1, characterized in that: A groove is arranged on the metal C-shaped ring (3).

3. A double sealing structure for a stop valve as claimed in claim 2, characterized in that: The groove on the metal C-ring (3) is , and the width of the annular groove needs to ensure that the metal C-ring can be normally placed, and to ensure that there is enough width so that the bottom surface of the groove can obtain a roughness of Ra0.8 or above by grinding. The depth of the annular groove is determined according to the wire diameter of the metal C-ring, and the depth needs to ensure the compression amount of the metal C-ring so that it has good rebound performance.

4. A double sealing structure for a stop valve as claimed in claim 3, characterized in that: The surface roughness Ra of the groove on the metal C-shaped ring (3) and the bottom of the pressure ring is less than Ra0.

8.

5. A double sealing structure for a central cavity of a stop valve as claimed in claim 4, characterized in that: The constant stress gasket (5) is a double-ring structure, the inner ring is made of metal, and the outer ring is made of graphite.

6. A stop valve using a central cavity double sealing structure, characterized in that: Using any one of the middle cavity double sealing structures of claims 1-6, the middle cavity double sealing structure is arranged between the valve body (1) and the valve cover (6), and the pressure ring (4) is sleeved on the valve stem (7).

7. A stop valve using a central cavity double sealing structure as claimed in claim 6, characterized in that: The valve stem (7) is externally connected to the bellows (2), and the pressure ring (4) is sleeved on the bellows (2).

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