CN110848412A

CN110848412A - Application of negative expansion material in low-temperature valve

Info

Publication number: CN110848412A
Application number: CN201911206980.XA
Authority: CN
Inventors: 曹强; 贺邑虎
Original assignee: Tongji University
Current assignee: Tongji University
Priority date: 2019-11-29
Filing date: 2019-11-29
Publication date: 2020-02-28

Abstract

The invention relates to an application of negative expansion material in a low-temperature valve, which comprises a valve body, wherein a cavity is arranged in the valve body, a ball body is arranged in the cavity, the negative expansion material and the material for manufacturing the low-temperature valve are compounded and applied to the valve body which is in contact with the ball body, and the integral zero change or the approximate zero change of the valve body is realized when the temperature is changed. Compared with the prior art, the invention can realize or approximately realize zero change of the valve, so that the possibility of the fluid contacting with the outside is reduced, and unnecessary loss and danger caused by temperature change are reduced.

Description

Application of negative expansion material in low-temperature valve

Technical Field

The invention relates to the technical field of low-temperature valves, in particular to application of a negative expansion material in a low-temperature valve.

Background

With the continuous development and progress of society, people pay more attention to the reduction of loss and waste, and the loss in the transportation and transmission of the cryogenic fluid is also paid attention to. Due to the special nature of cryogenic fluids, the cryogenic medium is usually flammable, explosive and very permeable, and therefore the corresponding corrosion resistance of the cryogenic valve is required to ensure its safety. .

The low-temperature valve refers to a valve which can be used under a low-temperature working condition, and the valve with the working temperature lower than-40 ℃ is generally called as the low-temperature valve. The low-temperature valve is an indispensable important device in the industries of petroleum industry, air separation, natural gas and the like, and the quality and the action effect of the low-temperature valve directly determine whether the work can be efficiently, safely and economically produced. With the continuous development of modern industry, the application field of the low-temperature valve is wider and wider, and the demand is larger and larger. In recent years, the valve industry in China is greatly improved, but the nationalization of all materials cannot be realized, parts such as valve covers and the like can be produced, qualified stuffing boxes, sealing elements and the like cannot be produced, and key parts of China must be imported from abroad.

The filler, the sealing element and the like which are independently manufactured in China cannot meet the requirements of the low-temperature valve, and one important reason is that the standard sealing cannot be met, so that low-temperature media easily overflow from a gap with incomplete sealing, and a large amount of loss is caused.

The valve can cause the valve body and the valve rod valve clack to generate large gaps to cause leakage of fluid and entering of external heat when the temperature changes due to the influence of thermal expansion and cold contraction, so that internal abnormal boosting or fluid vaporization and dissipation are caused to the outside.

The approximate temperature range of the valve application is generally known when the valve is manufactured, so that the approximate stress generated by the temperature difference change can be calculated in advance, and a pre-tightening force can be given in advance, so that the strain can be relatively small, but the valve is easy to be under the pressure given by the pre-tightening force during the closing period, and the valve is easy to damage more quickly.

Disclosure of Invention

The present invention is directed to overcoming the above-mentioned deficiencies of the prior art and providing a negative expansion material for use in cryogenic valves.

The purpose of the invention can be realized by the following technical scheme:

the invention provides an application of a negative expansion material in a low-temperature valve, wherein the low-temperature valve is provided with a valve body, a cavity is arranged in the valve body, a ball body is arranged in the cavity, the negative expansion material and a material for manufacturing the low-temperature valve are compounded and applied to the valve body contacted with the ball body, and the integral zero change or the approximate zero change of the valve body is realized when the temperature changes.

Preferably, the negative expansion material is compounded with the material for manufacturing the low-temperature valve and applied to the valve body, the lower end of the cavity of which is contacted with the ball.

Preferably, the material for manufacturing the low-temperature valve is a material with a positive expansion coefficient.

Further preferably, the material for manufacturing the low-temperature valve comprises low-temperature steel or austenitic stainless steel.

Preferably, the negative expansion material is a material with a negative expansion coefficient.

Further preferably, the negative expansion material is an iron-based laves phase compound.

Further preferably, the iron-based laves phase compound is selected from hafnium-tantalum-iron alloy Hf_0.87Ta_0.13Fe₂Negative expansion is achieved at temperatures of 222k-327k, corresponding to a linear expansion coefficient of-16.3 ppm/k.

Preferably, the compounding of the negative expansion material with the material of which the cryogenic valve is made is obtained by mixing the negative expansion material with the valve body in contact with the ball at the time of manufacture.

The invention uses negative expansion material and low temperature steel to make low temperature valve material to make composite manufacturing. The thermal shrinkage and cold expansion characteristics of the negative expansion materials enable the expansion coefficients of the negative expansion materials to be negative values, the expansion coefficients of materials for manufacturing the valve, such as low-temperature steel, are positive values, and when the temperature changes, the negative expansion materials and the main materials change oppositely, so that the efficiency of the low-temperature valve is ensured, and zero change of the valve is realized or approximately realized.

According to the invention, all materials do not need to be combined with the negative expansion material, and only a certain amount of powder of the negative expansion material needs to be added to the part, which is close to the cavity and is in contact with the ball, of the valve body, so that the main material is synchronously changed when the temperature is changed, and the influence of the temperature change on the whole valve is reduced.

Compared with the prior art, the invention can realize or approximately realize zero change of the valve, so that the possibility of the fluid contacting with the outside is reduced, and unnecessary loss and danger caused by temperature change are reduced.

Drawings

FIG. 1 is a sectional view of a ball valve in embodiment 1;

FIG. 2 is a temperature field distribution of the fluent simulated ball valve of example 1.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.

Example 1

The low-temperature valve in the embodiment is a DN100 ball valve, the structure of which is shown in figure 1, the low-temperature valve mainly comprises a valve body 1, a cavity is arranged in the valve body 1, a ball body 2 is arranged in the cavity, and the ball valve is also provided with a valve rod 3, an upper bearing 4, a lower bearing 5, a valve seat 6, a spring 7 and other parts.

In the embodiment, the part of the lower end of the cavity, which is in contact with the ball body, is mixed with the negative expansion material during manufacturing, so that the negative expansion material has zero change or approximate zero change on the whole when the temperature changes. In the embodiment, the ball valve of DN100 has a thickness of 24mm, an ambient temperature of 22 ℃, a medium temperature of-162 ℃ and a pressure of 4 MPa. Such as 2 for the temperature field distribution of the fluent simulated ball valve. The maximum deformation at the bottom of the cavity was 0.056 mm without pre-tightening. The negative expansion material and the valve body in contact with the bottom of the sphere are compounded, the valve material and the negative expansion material powder can be mixed to form a novel composite material, and the new material is replaced at the bottom of the right valve body when the right valve body is manufactured.

In the embodiment, the negative expansion material is an iron-based laves phase compound, namely hafnium-tantalum-iron alloy Hf obtained by the problem group of Tongcpeng researchers_0.87Ta_0.13Fe₂. The alloy realizes negative expansion at the temperature of 222k-327k, and the corresponding linear expansion coefficient reaches-16.3 ppm/k. Such materials may be used in combination with ferrous cryogenic steels and the like to reduce shrinkage or expansion caused by changes in temperature.

For the cast steel of the valve body material in this embodiment, the change of 56 microns under the temperature difference of 184K indicates that the change of 30 microns is about 100K between 222K and 322K. This example compares 40% Hf_0.87Ta_0.13Fe₂Mix with the material at the lower end of the ball valve cavity to form a new bottom end. The deformation of the bottom was 30 μm 0.6 to 100K 16.3 ppm/K24 mm/1000 2.352 μm. I.e. maximum deformation at that timeThe amount is only 2.352 microns. In the above calculation formula: 30 μm is the deformation of the valve body material cast steel under the above temperature difference condition, 0.6 is the proportion of the valve body material cast steel in the new bottom end, 100K is the temperature difference, 16.3ppm/K is the absolute value of the linear expansion coefficient of the negative expansion material, and 24mm is the thickness of the ball valve (the unit is changed into micron by dividing 1000).

The embodiments described above are intended to facilitate the understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims

1. The application of the negative expansion material in the low-temperature valve is characterized in that the negative expansion material and the material for manufacturing the low-temperature valve are compounded and applied to the valve body in contact with the ball body, so that the integral zero change or the approximate zero change of the valve body is realized when the temperature is changed.

2. The use of a negative expansion material in a cryogenic valve according to claim 1 wherein the negative expansion material is compounded with the material used to form the cryogenic valve and applied to the valve body where the lower end of the cavity contacts the ball.

3. Use of a negative expansion material in a cryogenic valve according to claim 1 or 2, wherein the cryogenic valve is made of a material having a positive coefficient of expansion.

4. Use of a negative expansion material in a cryogenic valve according to claim 3, wherein the material from which the cryogenic valve is made comprises cryogenic steel or austenitic stainless steel.

5. Use of a negative expansion material in a cryogenic valve according to claim 1 or 2, wherein the negative expansion material has a negative coefficient of expansion.

6. The use of a negative expansion material in a cryogenic valve according to claim 5, wherein the negative expansion material is an iron-based laves phase compound.

7. The use of a negative expansion material in cryogenic valves as claimed in claim 6 wherein the iron based laves phase compound is selected from the group consisting of hafnium tantalum iron alloy, Hf_0.87Ta_0.13Fe₂Negative expansion is achieved at temperatures of 222k-327k, corresponding to a linear expansion coefficient of-16.3 ppm/k.

8. The use of a negative expansion material in a cryogenic valve according to claim 1, wherein the negative expansion material is compounded with the material of which the cryogenic valve is made by mixing the negative expansion material with the valve body which is in contact with the ball during manufacture.