Analysis of the hard sealing principle of the stop valve for ammonia
Time: September 24, 2020 23:00:02 Source: Yonglong Valve Reading: zero second
Analysis of the hard sealing principle of the stop valve for ammonia
Ammonia stop valve, also known as liquid ammonia stop valve and ammonia stop valve, is applied to the manual switch stop valve of liquid ammonia, ammonia, refrigerant storage tank and fluid equipment pipeline, and the application of gas and liquid of ammonia stop valve. The principle of hard sealing performance is analyzed as follows:
1、 Sealing of ammonia stop valve in ammonia gas
Ammonia/According to Poisson's formula, the tightness of gas is related to gas molecules and gas viscosity.
According to Poisson's formula, gas sealing is related to gas molecules and gas viscosity. The leakage is inversely proportional to the length of the capillary tube and the viscosity of the gas, and directly proportional to the diameter of the capillary tube and the driving force. When the diameter of the capillary is the same as the average degree of freedom of the gas molecule, the gas molecule will flow into the capillary with free thermal motion. Therefore, when we are doing the valve sealing test, the medium must use water to play the role of sealing, and air, that is, gas, cannot play the role of sealing.
Even if we reduce the capillary diameter below the gas molecule by plastic deformation, the flow of gas cannot be stopped. The reason is that the gas can still diffuse through the metal wall. So when we do gas test, we must be more strict than liquid test.
Long neck corrugated pipe ammonia stop valve
2、 Sealing of ammonia stop valve in liquid ammonia
The sealing of liquid ammonia/liquid is carried out through the viscosity and surface tension of the liquid.
The sealing of liquid is carried out through the viscosity and surface tension of liquid. When the leaking capillary tube of the valve is filled with gas, the surface tension may repel the liquid or introduce the liquid into the capillary tube. This creates a tangent angle. When the tangent angle is less than 90 °, the liquid will be injected into the capillary, which will lead to leakage. The reason for leakage lies in the different properties of the medium. Different results will be obtained when the test is conducted with different media under the same conditions.
Water, air or kerosene can be used. When the tangent angle is greater than 90 °, leakage will also occur. Because it is related to the grease or wax film on the metal surface. Once the film on these surfaces is dissolved, the characteristics of the metal surface will change. The originally rejected liquid will wet the surface and leak. In view of the above situation, according to Poisson's formula, the purpose of preventing leakage or reducing leakage can be achieved under the condition of reducing capillary diameter and medium viscosity.
3、 Sealing principle of leakage channel of stop valve for ammonia
The ammonia stop valve/seal is composed of two parts, namely, the roughness formed by the unevenness scattered on the wavy surface and the waviness of the distance between wave peaks.
The valve seal consists of two parts, namely, the roughness formed by the unevenness scattered on the wavy surface and the waviness of the distance between wave peaks. Under the condition that the elastic strain force of most metal materials in our country is low, if we want to reach the sealed state, we need to raise higher requirements on the compression force of metal materials, that is, the compression force of materials should exceed their elasticity. Therefore, when designing the valve, the sealing pair will match with a certain hardness difference, which will produce a certain degree of plastic deformation sealing effect under the effect of pressure.
If the sealing surface is made of metal materials, the uneven protruding points on the surface will appear first. At the beginning, only a small load is required to make these uneven protruding points produce plastic deformation. When the contact surface increases, the surface irregularity will become plastic elastic deformation. At this time, the roughness of both sides in the concave will exist. When it is necessary to apply a load that can cause severe plastic deformation of the underlying material, and make the two surfaces contact closely, these remaining diameters can be closed along the continuous line and circumferential direction.
300LB American Standard Class Ammonia Stop Valve
4、 Valve sealing pair of ammonia stop valve
Ammonia stop valve /The valve sealing pair is the part of the valve seat that closes when the valve seat and the closing member contact each other.
The valve sealing pair is the part of the valve seat that closes when the valve seat and the closing member contact each other. The metal sealing surface is liable to be damaged by the entrapped medium, medium corrosion, wear particles, cavitation and erosion during use. Such as wear particles. If the roughness of the wear particles is smaller than that of the surface, the surface accuracy will be improved when the sealing surface is run in, without deterioration. On the contrary, the surface accuracy will deteriorate. Therefore, when selecting wear particles, factors such as their materials, working conditions, lubricity and corrosion to the sealing surface should be comprehensively considered.
Like wear particles, when selecting seals, we should comprehensively consider various factors affecting their performance to prevent leakage. Therefore, materials resistant to corrosion, abrasion and erosion must be selected. Otherwise, the lack of any requirement will greatly reduce its sealing performance.
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