JPH0514144B2 - - Google Patents

Description

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of a steam strainer device which is an embodiment of the present invention, Fig. 2 is an enlarged view of its main parts, and Figs. 3 and 4 show the structure of the packing used in Fig. 1. FIG. 3 is a partially sectional perspective view showing the structure of the braided packing, and FIG. 4 is a perspective view showing the graphite tape wrapped around the braided packing. 1... Casing, 1c... Opening, 4... Annular packing, 4a... Core, 4 _ab ... Braided packing, 4b... Double bag knitting, 4c... Graphite tape.

Claims (1)

[Scope of Claims] 1. A strainer that is used in a high-temperature, high-pressure superheated steam line and has a structure in which an opening for inserting an element in a casing is sealed with a gasket and closed with a lid, in which asbestos and a heat-resistant abrasive agent are added to the sealed portion. The entire outer surface of the core is mixed and molded with asbestos yarn containing metal wires, and the outer surface of the circular plate-shaped braided packing is wrapped with graphite tape. A steam strainer characterized by using an annular packing formed by *Theory [Technical field to which the invention pertains] This invention relates to a strainer installed in the middle of piping of a high-temperature, high-pressure superheated steam line and equipped with 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 incorporating an element. [Prior art and its problems] This type of strainer is installed in the middle of piping,
Since the casing contains an element that removes impurities from the steam passing through the pipe, the casing is provided with an opening for inserting and removing the element outside the opening to which the pipe is connected. 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, resulting in problems in terms of lifespan. [Object of the Invention] The present invention provides a gasket used in a steam sealing part that is sufficiently effective for high-temperature, high-pressure steam sealing, has a long life, and is inexpensive, without having to yield like a metal gasket. The purpose is to provide a sealed steam strainer. [Summary of the Invention] This invention is a braided packing in the form of an annular plate, in which 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 wires, and the surface is baked with graphite. The above object was achieved by using an annular packing whose entire outer surface was wrap-wound with graphite tape. [Embodiment of the Invention] FIG. 1 is a longitudinal sectional view of a steam strainer which is an embodiment of the present invention, and details of the seal portion are shown in FIG. 2. Reference numeral 1 denotes a casing, which is installed in the middle of a high-temperature, high-pressure superheated steam line with pipes connected to pipe connection openings 1a and 1b. Casing 1
Built-in is an element 2 for removing impurities from the steam passing through the piping. 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 embedded in 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 1c and tightening it with a nut 9, the annular packing 4 is attached to the annular packing 4 in the initial axial direction. A tightening surface pressure is applied and transmitted in the radial direction so that the annular packing 4 conforms to the mating metal. This circular packing 4
As shown in Fig. 3, a semi-metallic braided packing 4 has a core 4a formed by mixing and molding asbestos and a heat-resistant abrasive agent, a double bag knitting 4b made of asbestos thread containing metal wires, and a surface baked with graphite. _AB is used as a base, and its outer surface is wrap-wound in an armor-like shape with graphite tape 4c, as shown in FIG. The above-mentioned braided packing _4ab has a circular knitted surface, 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 abrasive agent, the axial tightening force is uniformly transmitted in the radial direction, just like air in a rubber tube. Therefore, it is partially empty〓
It is less likely to cause unevenness or density unevenness, and the sealing properties are improved. Generally, this kind of packing material has thermal loss at high temperatures and creep. Due to heat loss, a gap is created between the stud bolt 7, nut 9, and retainer ring 8 that tighten the annular packing 4. When the high-pressure steam power that fills the casing 1 disappears, the stud bolt and nut can no longer tighten the annular packing. 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 However, in the present invention, since the graphite tape 4c is wrap-wound over the entire outer surface of the braided packing mainly made of asbestos or the like, it blends well with the mating metal surface with which it comes into contact, and the braided packing has a graphite tape 4c wrapped around the entire outer surface of the braided packing. Since it is shielded from the atmosphere by the eye tape 4c, the thermal loss of the packing is suppressed even when exposed to high-temperature steam.
Steam strainer maintenance work such as retightening the gaskets is reduced. [Effects 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 leakage due to fatigue over time is prevented. The life of the steam strainer can be extended without causing any damage. In addition, since the main component of the braided packing is asbestos, 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 overlapping tape provides improved sealing properties and reduces maintenance work on the steam strainer.