JPH049951B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to the improvement of a thermal relief valve used as a thermal shock mitigation device such as a drain valve in a thermal power plant. In addition to preventing wear and damage to the valve seat surface, the valve device can be opened and closed by itself, which eliminates the need for external power, making it possible to manufacture a small and inexpensive valve device.

[Conventional technology and its problems]

Generally, the drain valve is branched from the main steam pipe installed in the boiler and turbine for the purpose of setting steam conditions when starting up the plant, discharging condensate generated during operation, and releasing main steam when the plant is stopped. It is installed at one location on the drain pipe that communicates with the drain tank, etc.

However, in recent years, the pressure and temperature of main steam in upper air plants has been, for example, 246 ^kgf /cm ² g・
Because the temperature is extremely high at 560℃ and the pressure is high, the high mass of hot water generated from this water is rapidly discharged from the upper air drain valve under high differential pressure conditions. As thermal power plants are repeatedly started and stopped to adjust the load, the frequency of use of the drain valve increases dramatically.
Wear or damage to the seat surface of the drain valve has become noticeable.

Since wear and damage on the valve seat surface interferes with the normal operation of the entire plant, one countermeasure is to remove condensed water generated during operation, which is one of the original purposes of installing the drain valve. Currently, the valve is opened and used only when the plant is started and stopped, without discharging the water.

Such changes in usage conditions can reduce the chance of damage to valves during plant operation, but on the other hand, condensed water generated as the steam temperature decreases during plant operation may accumulate in the drain pipe and upstream of the drain valve. As a result of this temperature dropping over time and cooling, for example, when the upper air drain valve is opened when the upper air plant is stopped, a high temperature of close to 500℃ will be released from the main steam pipe immediately after the cooled condensed water is discharged. Not only hot water, but even higher-temperature evaporation flows in all at once, giving a large thermal shock not only to the drain valve but also to the entire drain discharge system, including the main valve and piping, and these operations are repeated almost every day. Under recent plant operating conditions, metal fatigue has occurred in the thermal shock portion, causing cracks and damage to the portion.

As a means to deal with these problems, for example, a heater is attached to the drain pipe, and the heater heats and maintains the cooled condensed water at a predetermined temperature. Products have been put into practical use that reduce the temperature difference with the steam to reduce the thermal shock applied to drain valves, etc., but they have the basic disadvantage of requiring the installation of a separate large-scale heating device. I could see it.

On the other hand, as a simple solution to the above problem,
A bypass pipe is installed on the outside of the drain valve to communicate the primary side and the secondary side, and a stop valve and a thermal relief valve for flow rate adjustment are installed between the drain valve and the condensed water generated in the main steam pipe. By constantly flowing a smaller amount of water from the primary side to the secondary side, the upstream side of the drain valve is filled with high-temperature condensed water to prevent the valve seat surface from being cooled. Shock mitigation devices are used in some cases.

However, the thermal relief valve installed in the conventional mitigation device described above not only requires a separate stop valve for water shutoff or flow rate adjustment, but also that the valve body and valve seat are both made of metal. However, various problems were observed, such as severe wear and damage to the valve seat surface due to the effects of heat from hot water and main steam.

[Means for solving problems]

Therefore, the present invention provides a ceramic valve seat fixed to the fluid inlet side of a valve case, a cylindrical valve seat holder that is fitted into the valve case and fixes the valve seat, and a valve seat holder that is fitted inside the valve seat holder. , consists of a valve body holder with a passageway passing through it, and a ceramic valve body loosely inserted into the gap between the valve seat and the valve body holder, and the valve body holder has a coefficient of thermal expansion lower than that of the valve seat holder. The above-mentioned problems are solved at once by being made of a large material and by pushing the valve body and closing the seat surface by the thermal expansion of the valve body presser.

[Effect]

Since the thermal relief valve of the present invention has its valve body and valve seat made of ceramics, even when a minute amount of condensed water is discharged under severe conditions of high differential pressure, the seat surface caused by the fluid While reliably preventing wear or damage to the valve body, it also enables the operation of a self-powered small valve device that automatically opens and closes the valve body by utilizing the difference in thermal expansion of the metal materials used such as the valve body holder. It has a special effect of doing this.

〔Example〕

Hereinafter, the configuration of the present invention will be described in more detail based on the embodiments shown in the drawings. 1 is a valve case of a thermal relief valve, and 2 is a valve made of a metal material with a relatively small coefficient of thermal expansion on one side of the inside thereof. A valve seat made of ceramics is fixed with a retainer 3, 4 is a valve body made of ceramics having a water passage groove 4' on its outer periphery, and 5 is a valve body made of ceramic having a water passage groove 4' in the axial direction and a direction perpendicular thereto. The valve body holder is made of a metal material with a relatively large coefficient of thermal expansion, and is formed by penetrating the communicating water passages 5', 5'', and presses the valve body 4 against the seat surface of the valve seat 2 when it expands. It is supported so that it can be seated.

In the figure, 6 indicates a sealing material, 7 indicates a welded portion, 8 indicates an inlet pipe, and 9 indicates an outlet pipe.

Therefore, the above-mentioned thermal relief valve is prepared in advance by the sum of the length l ₁ of the valve seat 2 and the valve seat holder 3 and the length of the valve seat 2, the valve body 4, and the valve body holder 5 (l ₁ +l ₂ ). In order to obtain a minute lift at room temperature, settings are made in advance according to the difference in thermal expansion of the materials of each part, and at the same time, each of the above (l ₁ ) and (l ₂ + l ₃ ) at a predetermined temperature of each part is set. The configuration is such that a minute lift whose expansion amount is set in advance at room temperature is moved in the closing direction to apply surface pressure necessary to shut off fluid to the contact surface between the valve seat 2 and the valve body 4.

In the thermal relief valve of the present invention configured as described above, when the temperature of the fluid in use changes and the temperature is below a predetermined temperature, the valve body opens due to the fluid pressure and discharge of the low-temperature fluid is performed intermittently. When the fluid temperature rises to a predetermined temperature or higher, the amount of thermal expansion of the valve body holder 5 increases, and the valve body 4
Since the valve is closed by pressing the valve against the valve seat surface, the temperature of the fluid inside the pipe can be maintained within a constant range at all times.

In this way, thermal relief valves are used to prevent temperature drops due to heat radiation in drainage piping systems, etc., but in order to satisfy their function, the pressure and temperature of the fluid must always be higher on the upstream side than on the downstream side. It is necessary.

However, in thermal power plants, there is concern about backflow of low-temperature water from the downstream side due to changes in operating conditions such as the condition of the collecting pipe on the drain discharge side or when the boiler is stopped for a long time. Since the valve seat 2 is not physically connected to the valve seat 2, this is prevented by a check function in which the valve seat 2 is pressed against the valve seat 2 by backflow.

〔Effect of the invention〕

As described above, according to the thermal relief valve of the present invention, it is possible to use ceramics for the valve seat 2 and the valve body 4 that form the seat surface, and this allows the thermal relief valve to be heated by high temperature and high differential pressure fluid. This can significantly reduce the wear and tear on the valve seat surface that is caused by external power, and since the operating principle of the valve body 4 is to utilize the difference in expansion of materials, the valve can be opened and closed by itself, and can be operated by external power or separately. Since there is no need to install a stop valve, etc., the amount of emissions from the valve is minute, and the operating characteristics are accompanied by a slight delay time, the required characteristics as a thermal shock mitigation device without rapid opening and closing are required. This provides a special effect in that it is possible to obtain a so-called slow and gentle valve operation that is suitable for the following conditions.

Furthermore, in the present invention, the fluid is directed toward the valve body from the valve seat side, so after the valve body presser expands due to thermal expansion and becomes fully closed, the high temperature fluid does not flow into the valve body presser. There is no contact, so even if an abnormally high temperature occurs in the fully closed state, buckling due to excessive expansion can now be reliably avoided.

Furthermore, since the valve body is not physically connected to the valve body holder and has a structure that opens with fluid, not only can the device be installed in any direction, but also the valve body can open when fluid flows backward. It was possible to provide an extremely effective thermal relief valve that can also perform the function of a check valve by being pressed against a seat.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of the central portion of the thermal relief valve of the present invention. In the diagram, 1...valve case, 2...valve seat, 3...
Valve seat holder, 4... Valve body, 5... Valve body holder.

Claims (1)

[Claims] 1. A ceramic valve seat 2 fixed to the fluid inlet side of the valve case 1, a cylindrical valve seat holder 3 that is fitted into the valve case and fixes the valve seat, and a cylindrical valve seat holder 3 that is fitted into the valve seat holder, Valve body holder 5 with a water passage running through it
and a ceramic valve body loosely inserted into the gap between the valve seat and the valve body holder, and the valve body holder is made of a material having a higher coefficient of thermal expansion than the valve seat holder. A thermal relief valve characterized in that a valve body is pushed by thermal expansion to close a seat surface.