JPH0442481Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to an airtight structure for a pipe joint through which gas or liquid flows, particularly for sealing a joint of a steam pipe of a steam turbine.

(Prior art) The seals at the joints of pipes through which high-pressure, high-temperature gases, such as high-pressure, high-temperature steam in steam turbines, flow generally use heat-resistant metal ring packings with a U-shaped cross section. , Steam pressure is applied to the inside of the U-shaped portion of the ring packing to ensure sealing performance. Figure 3 is a cross-sectional view of a pipe joint using this type of ring packing.
The prior art will be explained below based on the drawings.

In Fig. 3, reference numeral 1 denotes an annular seal structure having a U-shaped cross section and made of nickel alloy steel with excellent high-temperature strength, such as NIMONIC, and is an annular seal provided on the end face of the flange 2a of the steam pipe 2, surrounding the pipe opening. The U-shaped sealing ring 1 is inserted into the groove 3 to maintain a stable position. Note that the side wall 3a of the seal groove 3 on the inner surface side of the steam pipe 2 is the flange 2.
A gap 4 is provided between the end face of the flange 5a and the opposing end face of the flange 5a. Reference numeral 5 designates a steam pipe that is a partner steam pipe connected to the steam pipe 2 or an inlet pipe of the vehicle compartment, and the flange 5a of the steam pipe 5 and the flange 2a of the steam pipe 2 are fitted into the seal groove 3. The U-shaped seal ring 1 is inserted, and the ring nut 6, which is loosely fitted to the flange 2a, is screwed onto the screw 7 provided on the flange 5a to be connected by tightening. At this time, the flanges 1a and 1b on both sides of the U-shaped seal ring 1 are pressed against the bottom surface of the seal groove 3 and the end surface of the flange 5a, respectively, by the spring force of the U-shaped structure and the pressure of the object flowing in the pipe to ensure sealing performance. That's what I do.

A space 3b defined by the seal groove 3 and the outer wall of the U-shaped seal ring 1 has a pressure lower than the pressure of steam flowing in the steam pipes 2 and 5, for example, slightly lower than atmospheric pressure, by a hole 8 penetrating the pipe flange 5a. The ground capacitor (not shown) is connected to the ground capacitor (not shown). This is because the flanges 2a and 5a are usually tightened in close contact with each other, so that the pressure in the space 3b is low, and if steam leaks, it is collected by flowing into the ground condenser.

With this structure, when high-pressure, high-temperature steam flows through the steam pipes 2 and 5, high steam pressure is applied to the U-shaped seal ring 1 at the pipe joint through the gap 4, while the U-shaped seal ring The space 3b in the outer wall portion of No. 1 is in communication with a low pressure location through a hole 8 and has a low pressure. For this reason, a differential pressure is applied to the U-shaped seal ring 1 and the opening width of the U-shaped seal ring 1 is expanded, so that the flanges 1a and 1b are connected to the grooves 1 and 1, respectively.
The bottom surface of the flange 5a and the end surface of the flange 5a press firmly to ensure sufficient sealing performance.

(Problem to be solved by the invention) As the U-shaped seal ring 1 is exposed to high-temperature steam for a long time under high-pressure conditions during long-term operation of a steam turbine, creep occurs in the U-shaped seal ring 1. , this creep reduces the spring force of the U-shaped structure. Therefore, when the steam pressure is low, for example at startup, the U-shaped seal ring 1
The flanges 1a and 1b are no longer pressed sufficiently against the opposing surfaces, making it impossible to ensure sealing performance. Furthermore, if the spring force continues to decrease and a gap is created between the flanges 1a and 1b and the opposing surfaces, no effective differential pressure will be generated in the U-shaped seal ring 1 even if the steam pressure increases. For this reason, there is a problem in that the ribs 1a and 1b of the U-shaped seal ring 1 are not pressed against the opposing surfaces, resulting in steam leakage.
Note that if the sealing performance deteriorates due to a decrease in spring force, the U-shaped seal ring 1 will need to be replaced, but since the U-shaped seal ring 1 is made of expensive NIMONIC etc., there will be a large amount of manufacturing and maintenance costs. There is also the problem that it takes SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide an airtight structure for a pipe joint part that maintains reliable sealing performance over a long period of time and is made of an inexpensive material.

(Means for Solving the Problems) The present invention, for the joint portion configured as described above, overlaps two flat annular bodies and opens on the inner circumferential side with the mating surface as the center. A packing ring consisting of a seal ring that forms an annular space with an inverted V-shaped cross section, and an inner ring body that is inserted into the annular space and has a chevron-shaped cross section similar to the annular space that has an inverted V-shaped cross section of this seal ring. was fitted, and the two pipes were connected by the ring nut.

(Function) The airtight structure according to the present invention consists of a seal groove which is an annular groove with a square cross section carved into the flange end face of one pipe, a seal ring fitted into the seal groove in an overlapping manner, and this seal. A packing ring consisting of an inner ring body with a chevron-shaped cross section is inserted into an annular space with a V-shaped cross section formed in the ring, and is fitted into the seal groove, and the other flange surface is brought into contact with the seal ring, which is tightly tightened with a ring nut. Since two pipes are connected, the contact surfaces of the flange ends of the two pipes, the contact surfaces of the flat surface of the seal ring and the bottom of the seal groove and the other flange end surface, and the overlapping surfaces of the two seal rings, etc. The tightening force of the ring nut applies pressure to the seal ring, and the pressure of the fluid flowing through the connected pipe applies to the seal ring through the inner ring body. The seal ring acts to further increase the airtightness of the seal ring, and the conduit that communicates with the ground condenser is provided through the other flange, creating a large pressure difference between the inside and outside of the seal ring. The two joints work in series with each other and act on the respective contact surfaces, making the sealing performance of the pipe joint highly reliable.

(Embodiments of the invention) Examples of the invention will be described below based on the drawings. FIG. 1 is a sectional view of a pipe joint portion having an airtight structure according to an embodiment of the present invention, and FIG. 2 is a plan view in the direction of arrow A in FIG. 1. In FIGS. 1 and 2, parts that are the same as those in the conventional example shown in FIG. 3 are designated by the same reference numerals, and their explanations will be omitted.

In FIG. 1, reference numeral 9 denotes a seal ring, which is formed by overlapping two flat annular bodies of equal thickness, and has an inverted V-shaped opening opening on the inner peripheral surface of the annular body with the seam as the center. It is made to form an annular space in cross section. An inner ring body 10, which is an annular body having a chevron-shaped cross section similar to the cross-sectional shape of the space, is fitted into the annular space, thereby forming a packing ring 11 that fits into the seal groove 3. Note that it is desirable that the inner ring 10 be subdivided into several segments in consideration of the difference in thermal expansion with the seal ring 9.

Therefore, the airtight structure of the pipe joint is achieved by inserting the above-mentioned packing ring 1 into the seal groove 3, which is an annular groove with a square cross section, carved in the end face of one flange 2a.
1, and then join the end face of the flange 2a and the end face of the flange 5a of the other pipe, and then the flange 2a
The pipes 2 and 5 are formed by screwing the ring nut 6 loosely fitted into the screw 7 of the flange 5a, and tightly matching the end surfaces of both flanges to connect the pipes 2 and 5.

The seal ring 9 is made of graphite, which has heat resistance and strength, and is molded into the above shape.
The thickness when the two are overlapped is slightly larger, for example, by about 0.2 mm, than the depth of the seal groove 3, so that this serves as a tightening allowance. Also, inner ring body 1
0 is made of carbon steel, the wedge surface has been subjected to surface hardening treatment such as nitriding treatment, and the top is slightly cut out to make it flat.

After fitting the packing ring 11 configured as described above into the seal groove 3, the end faces of the flanges 2a and 5a of the tubes 2 and 5 are joined, and the ring nut 6 is screwed to tightly connect both tubes. As a result, the tightening force acts on the joining surfaces of the end faces of the flanges 2a and 5a, and the outer joints are covered with the ring nut 6, and the seal ring 9 of the packing ring 11 is slightly compressed. In this state, it exists between both flanges 2a and 5a. Therefore, the seal ring 9 elastically contacts the seal groove 3 and the end face of the flange 5a to maintain airtightness, and the pressure of the fluid flowing through the pipes 2 and 5 is applied via the inner ring body 10 to seal the seal. This acts on the ring 9 and acts as a pressing force on the contact surface, thereby further improving the sealing performance. On the other hand, the existence of a conduit 8 passing through the flange 5a and communicating with a ground condenser (not shown) generates a pressure difference between the inside and outside of the packing ring 11, which acts to further enhance the airtightness of the packing ring 11. .

(Effects of the invention) As is clear from the above explanation, according to the invention, a seal ring is formed by overlapping two annular plates having a sloped surface on the inner circumferential side, and A wedge-shaped inner ring is inserted into the inverted V-shaped groove defined by the sloped surface to form a packing ring, which is inserted into the seal groove between both flanges and tightened to tighten the flanges. While keeping the contact surface airtight with the end face, the flat surface of the seal ring and the inverted V-shaped groove are shaped into a sloped surface by the differential pressure applied to the seal ring and the pressure of the fluid in the pipe applied to the wedge-shaped inner ring body. Since it is pressed against the end face of the flange through the pipe fitting, the sealing performance that prevents the leakage of gas inside the pipe from the pipe joint can be made even more reliable. Furthermore, since the seal member can be made of inexpensive and readily available materials such as graphite or carbon steel instead of an expensive heat-resistant alloy, maintenance costs can be reduced.

[Brief explanation of drawings]

1 is a partial cross-sectional view of a fluid pipe joint portion equipped with a seal structure according to an embodiment of the present invention; FIG. 2 is a plan view of the structural portion of the airtight ring in FIG. 1 in the direction of arrow A; The figure is a partial cross-sectional view of a fluid pipe joint portion including a conventional airtight ring structure. 1...U-shaped seal ring, 2, 5...tube, 2
a, 5a...Flange, 3...Annular seal groove, 6
...Ring nut, 8 ... Pipe line, 9 ... Seal ring, 10 ... Inner ring body, 11 ... Packing ring.

Claims (1)

[Claims for Utility Model Registration] 1) Two pipes each having a flange at the end of the pipe are connected by screwing a ring nut loosely fitted into the flange of one pipe into a thread on the flange of the other pipe. In the pipe fitting part, two flat annular bodies are placed one on top of the other in the seal groove, which is an annular groove with a square cross section, provided on the flange end face of one pipe, and the inner peripheral surface side is placed around the mating surface. It consists of a seal ring forming an annular space with an inverted V-shaped cross section opening to the inner ring body, and an inner ring body that has a chevron-shaped cross section similar to the annular space with an inverted V-shaped cross section and is inserted into the annular space. An airtight structure for a pipe joint portion, characterized in that a packing ring is inserted and the two pipes are connected by the ring nut. 2) Utility model registration The airtight structure described in claim 1 is characterized in that the seal ring constituting the packing ring is made of graphite, and the segment ring is made of carbon steel with a surface hardening treatment applied to the chevron-shaped surface. Airtight structure of pipe joint.