JPH0365205B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] This invention is installed in the middle of steam piping of a high-temperature, high-pressure superheated steam line, and has a built-in element for removing impurities from steam flowing into a turbine through the piping. The present invention relates to a so-called pressure seal structure such as a steam seal structure for an element insertion opening in a casing of a strainer.

[Prior art and its problems]

A steam strainer is installed in the middle of a steam pipe and has a built-in element that removes impurities from the steam passing through the pipe, so the element can be inserted into the casing in addition to the opening to which the steam pipe is connected. An opening is provided for removal. This opening is sealed using a gasket and closed with a lid, but since the gasket used here must withstand high pressure and high temperatures, conventionally a metal gasket formed into a wedge shape has been used. The advantage is that the stress is concentrated in the wedge-shaped part, so the sealing performance is good, but since it is made of metal, it has the following disadvantages.

Since there is a risk of damaging the other metal with which the packing comes in contact, the surface of the packing must be coated with a soft metal such as silver, which is expensive. Further, in the case of metal packing, since it is used in a yielded state, it becomes fatigued over time and leaks from the sealing portion, resulting in shortcomings in terms of service life.

[Purpose of the invention]

An object of the present invention is to provide a steam strainer sealed with a gasket that is sufficiently effective in sealing high temperature and high pressure steam, has a long life, and is inexpensive, without being used in a yielding manner as with metal gaskets.

[Key points of the invention]

In this invention, the packing for sealing an opening is made of graphite packing in the form of an annular plate.The outer periphery of the core is made of a mixture of asbestos and a heat-resistant lubricant, and the outer periphery is double-bag knitted with asbestos yarn containing 100 million yen cotton, and the surface is covered with graphite. The above object has been achieved by using a configuration in which the device is held in place by an annular plate-shaped semi-metallic packing that has been baked.

[Embodiments of the invention]

FIG. 1 is a longitudinal sectional view of a steam strainer according to an embodiment of the present invention, and details of the seal portion are shown in FIG. 2. In the figure, 1 is a casing, and steam piping is connected to piping connection openings 1a and 1b, and the casing is disposed in the middle of a high-temperature, high-pressure superheated steam line. The casing 1 contains an element 2 for removing impurities from steam passing through the pipes. This element 2 is fixed to the lid 3 and inserted through the element insertion opening 1c of the casing 1, and in order to seal this part with steam, both sides of the annular plate-shaped graphite packing 4, which will be described later, are attached to an annular plate. They are attached by being inserted and assembled using a semi-metallic gasket 5 having a shape of 50 mm, and are pressed by a segment ring 7 via a retaining ring 6. A stud bolt 8 is embedded in the end face of the lid 3, and by passing the stud bolt 8 through a light ring 9 attached to the tip of the opening 1c and tightening it with a nut 10, the semi-metallic packing 5 is set in the initial axial direction. A tightening surface pressure is applied and transmitted in the radial direction so that the semi-metallic packing 5 conforms to the mating metal. As shown in FIG. 3, this semi-metallic packing 5 has a core 5a made of a mixture of asbestos and a heat-resistant lubricant.
Double bag knitting 5a made of asbestos thread with metal cotton on the outer periphery.
The surface has been baked with graphite. The surface of the semi-metallic packing 5 is circular knitted, so it is dense and basically has a surface structure with good surface pressure distribution.
In addition, since there is a core 4a in the center formed by mixing and molding asbestos and a heat-resistant lubricant, the axial tightening force is uniformly transmitted in the radial direction, just like air in a rubber tube. Therefore, voids and non-uniform density are less likely to occur locally, resulting in better sealing properties. The graphite packing 4 sandwiched between the semi-metallic packing 5 is in the shape of an annular plate as shown in FIG.
It has good compatibility with the mating material and does not decrease in volume at high temperatures, so it exhibits stable sealing performance, but since it undergoes plastic flow, the semi-metallic packing 5 is sandwiched between the top and bottom as described above.

The semi-metallic packing described above has thermal loss at high temperatures and creep. Due to heat loss, a gap is created between the stud bolt 8, nut 10, and retainer ring 9 that tighten the packing.
When the high-pressure steam power filling the casing 1 disappears, the tightening force of the stud bolt and nut can no longer be obtained. Therefore, after the first ventilation, the nut is tightened once more to bring the tightening surface pressure of the seal to its initial state. If excessive tightening force is applied at this time, when the steam force disappears, the reaction force of the seal tightening surface pressure + stud bolt tightening force will act on the stud bolt, so when retightening, 10% of the initial tightening force will be applied. It is necessary to pay attention to the extent of

〔Effect of the invention〕

This invention uses semi-metallic packing on both sides of a graphite packing in the sealing part of a steam strainer, so it can be sealed without yielding like metal packing, and leakage due to fatigue over time can be prevented. It has a long lifespan without causing damage. Semi-metallic packing has asbestos as its main element, has excellent heat resistance, is low cost, and has an extremely small fiber diameter, which allows it to blend well with the mating metal surface. Also, the volume loss is large at high temperatures, and this alone has a drawback in sealing effectiveness, so it is used in the middle of semi-metallic packing.
Incorporating graphite packing, which has good airtightness and less volume loss at high temperatures, further improves airtightness.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view of a steam strainer which is an embodiment of the present invention, Fig. 2 is an enlarged view of its main parts, and Fig. 3 is the structure of the semi-metallic packing used in Figs. 1 and 2. FIG. 4 is a perspective view showing the first
FIG. 2 is an external perspective view of the graphite packing used in FIG. 1: Casing, 1c: Opening, 2: Element, 3: Lid, 4: Graphite packing, 5: Semi-metallic packing, 5a: Core, 5b: Double bag knitting.

Claims (1)

[Claims] 1. In a strainer that is used in a high temperature, high pressure superheated steam line and has a structure in which the element insertion opening of the casing is closed with a lid through a packing, the packing is connected to a circular plate-shaped graphite packing and this graphite packing is used. It is composed of a circular plate-shaped semi-metallic packing made of a core made of a mixture of asbestos and a heat-resistant lubricant, which is sandwiched from both sides, and the outer periphery of which is double-bag knitted with asbestos thread containing metal wool, and the surface is baked with graphite. A steam strainer characterized by: