JPS61175371A - Strainer for steam - Google Patents

Abstract

PURPOSE:To obtain a strainer for steam which has a long service life and is free from the leak due to the fatigue in the use for long years, by using an annular packing with is formed by winding a graphite tape in superpositoin, onto the sealing part of the strainer. CONSTITUTION:In the manufacture of an annular packing 4, the double circular braiding 4b consisting of the asbestos threads containing metal fiber is applied onto the outer periphery of a core 4a which is made from mixing-molding of asbestos and heat-resisting antifriction agent, in order to improve the sealing performance, and a braided packing 4ab made of semimetallics obtained through the baking-processing of graphite is formed onto the surface. The outer surface is lap-wound in armor form by a graphite tape 4c, in order to improve thee fittingness to the opponent metal surface in contact.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention has a built-in element that is installed in the middle of a high-temperature, high-pressure superheated steam line and removes 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 of a casing that can be inserted into a strainer incorporating a casing element.

[Prior art and its problems]

This type of strainer is installed in the middle of a pipe and has a built-in element that removes impurities from the steam passing through the pipe.The element can be inserted or removed outside the opening to which the pipe is connected to the casing. There is an opening for access. This opening is sealed with a gasket and closed with a lid, but since the gasket used here must withstand high pressure and high temperature, conventionally a metal gasket formed into a wedge shape has been used. The advantage of this is that the stress is concentrated on the wedge, so it has good sealing performance, but since it is made of metal, it has the following disadvantages. That is, since there is a risk that the gasket may damage the other metal with which it comes in contact, the surface of the gasket must be coated with a soft metal such as silver, which is expensive. In addition, since the packing is used with the metal yielding, it may become fatigued over time and leak, which poses a problem in terms of service life.

[Purpose of the invention]

This invention is a steam strainer sealed with a long-life and inexpensive packing that is sufficiently effective for high-temperature, high-pressure steam sealing without having to yield the packing used in the steam sealing part like metal ones. The purpose is to provide

[Key points of the invention]

In this invention, the outer periphery of a core made by mixing and molding asbestos and a heat-resistant abrasive agent is double-bag-knitted with asbestos yarn containing metal wire, and the outer surface of the braided packing is coated with graphite tape. The above objective was achieved by using an annular packing wrapped in lap winding.

[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. 1
The piping is connected to the piping connection openings la and lb in the casing, and is installed in the middle of the piping 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 an annular packing 4 (described later) is fitted therein for steam sealing in this part. Being pressed. A stud bolt 7 is inserted into the end face of the lid 3, and by passing this stud bolt 7 through a retaining ring 8 attached to the tip of the opening IC and tightening it with a nut 9, an initial axis is set in the annular packing 4. A directional tightening surface pressure is applied and transmitted in the radial direction so that the annular packing 4 conforms to the mating metal. As shown in FIG. 3, this annular packing 4 has a core 4a made of a mixture of asbestos and a heat-resistant abrasive agent.
The outer periphery of the double bag knit 4b is made of asbestos thread containing metal wires, and the surface is baked with graphite.Basically, the outer surface is made of a metallic braided backing 'ab, and the outer surface is covered with graphite tape 4c, as shown in Figure 4. It is lap-wound in the shape of a tower. The above-mentioned braided backing 'ab has a circular knitted surface and thus has a dense surface structure with basically 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 abrasive agent, the axial tightening force is uniformly transmitted in the radial direction, just like air in a rubber tube. Therefore, it is difficult for local areas, voids, and uneven density to occur.
Improves sealing properties. Furthermore, the graphite tape 4C was lap-wound on the outer surface of this braided packing in order to improve its conformity to the mating metal surface with which it comes into contact. This packing has thermal loss at high temperatures and creep. Stud bolt 7 and nut 9 tightening annular packing 4 due to heat loss. A gap is created between the retainer rings 8. When the high-pressure steam power filling the casing l disappears, the annular packing can no longer be tightened with the stud bolts and nuts. Therefore, after the tightening is completed, the change nut is tightened again to bring the tightening surface pressure of the seal to the initial state. If excessive tightening force is applied at this time, when the steam force disappears, the reaction force of the stud bolt tightening force of the seal tightening surface pressure will act on the stud bolt, so when retightening, the initial tightening force should be about 10 inches. You need to take precautions such as:

〔Effect of the invention〕

This invention uses an annular packing in which a braided packing is wrapped overlappingly with graphite tape for the sealing part of a steam strainer, so it can be sealed without yielding like a metal packing, and has a long service life without leakage due to fatigue over time. It is.

In addition, since the braided packing has asbestos as its main element, it has excellent heat resistance and is low cost.Furthermore, the fiber diameter is extremely thin, so it blends well with metal surfaces, and it is made of graphite, which has almost no weight loss at high temperatures. The sealing properties were improved by wrapping the tape in layers.

[Brief explanation of drawings]

Figure #x1 is a longitudinal cross-sectional view of a steam strainer device that is an embodiment of the present invention, Figure 2 is an enlarged view of its main parts, and Figures 3 to 3 show the structure of the packing used in Figure 1. FIG. 3 is a partially cross-sectional perspective view showing the structure of the braided packing, and FIG. 4 is a perspective view showing the state in which graphite tape is overlapped and stretched around the braided packing. 1; Casing, IC: Opening, 4; Annular packing, 4
a; Core, 4ab; Braided packing, 4b; Double bag knitting, 4
c: graphite tape. Figure 2

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 sealed with a packing and closed with a lid;
The outer periphery of a core made by mixing and molding asbestos and a heat-resistant abrasive agent is double-bag knitted with asbestos thread containing metal wire, and the outer periphery of a circular plate-shaped braided packing whose surface is baked with graphite is lap-wound with graphite tape. A steam strainer characterized by using an annular packing formed by