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Failure analysis and treatment of bellows globe valve

Time of issue:2021-07-14

(Summary description)The leakage of bellows globe valve is generally divided into internal leakage and external leakage, and there are many reasons for leakage. In general, the liquid medium contains solid impurities to destroy the sealing surface and cause failure. Combined with the analysis of the field application, the main reasons for the leakage of the valve stem are related to the valve structure, working environment and operation mode. 1 Structure: The valve stem adopts the double sealing structure of bellows and packing. The bellows is welded with the inner ring and outer ring to form the bellows assembly, and then welded with the valve stem and guide body to prevent the medium from leaking out through the valve stem. The valve stem moves up and down from the flat key I until the upper end face of the flat key I contacts the lower end face of the lower packing. As the lower packing is made of PTFE material, if the valve is opened excessively, the flat key I will be embedded in the packing, the valve can no longer be opened and closed, and the bellows assembly will be killed, resulting in medium leakage along the valve stem. The stretching length and compression of the bellows are determined according to the valve stroke. If the stretching or compression exceeds the limit, the bellows may be damaged, resulting in small braided pipe rupture and seal failure. Therefore, it is necessary to increase the opening and closing limit device of the valve, so that the bellows can expand and contract within the design range during the opening and closing process of the valve. 2. Working environment: The bad working environment of bellows globe valve is also one of the reasons for its failure. Because the bellows globe valve installed in the ship has been working in the salt spray environment for a long time, and there is often condensate dripping on the upper part, which causes the corrosion of the upper thrust ball bearing. In serious cases, it leads to the contact corrosion with the valve stem. 3 operation: If the bellows globe valve is opened or closed excessively in use, the valve may not meet the relevant performance requirements. If the valve is excessively closed, the sealing surface may be damaged, resulting in seal failure when the valve is used again. If the valve is opened excessively, the bellows assembly may be operated, causing leakage of the valve. The cause analysis and improvement of bellows stop valve fault are as follows After analyzing the existing problems of the valve, its structure, operation and environment were improved. The first is to increase the limit welfare of flat key I, and add a 3mm thick stainless steel packing pad to the lower packing of PTFE material, so as to prevent the packing from getting dirty and limiting the valve stem. When the valve is closed, if the valve can not be closed, it should not be forced to close, but open the valve, flush it with fluid for a period of time, and then close it again and again. If it still can not be closed, the grinding sealing surface should be checked. When the valve is opened, when the valve is opened to a certain height and the valve stem encounters small resistance, try not to continue to force the valve to open, so as to extend the service life of the valve stem and its sealing components. When installing the stop valve with thrust ball bearing on the upper part of the valve stem, it is necessary to avoid the condensation water dripping directly on the valve stem and causing the stem corrosion.

Failure analysis and treatment of bellows globe valve

(Summary description)The leakage of bellows globe valve is generally divided into internal leakage and external leakage, and there are many reasons for leakage. In general, the liquid medium contains solid impurities to destroy the sealing surface and cause failure. Combined with the analysis of the field application, the main reasons for the leakage of the valve stem are related to the valve structure, working environment and operation mode.
1 Structure:
The valve stem adopts the double sealing structure of bellows and packing. The bellows is welded with the inner ring and outer ring to form the bellows assembly, and then welded with the valve stem and guide body to prevent the medium from leaking out through the valve stem. The valve stem moves up and down from the flat key I until the upper end face of the flat key I contacts the lower end face of the lower packing. As the lower packing is made of PTFE material, if the valve is opened excessively, the flat key I will be embedded in the packing, the valve can no longer be opened and closed, and the bellows assembly will be killed, resulting in medium leakage along the valve stem. The stretching length and compression of the bellows are determined according to the valve stroke. If the stretching or compression exceeds the limit, the bellows may be damaged, resulting in small braided pipe rupture and seal failure. Therefore, it is necessary to increase the opening and closing limit device of the valve, so that the bellows can expand and contract within the design range during the opening and closing process of the valve.
2. Working environment:
The bad working environment of bellows globe valve is also one of the reasons for its failure. Because the bellows globe valve installed in the ship has been working in the salt spray environment for a long time, and there is often condensate dripping on the upper part, which causes the corrosion of the upper thrust ball bearing. In serious cases, it leads to the contact corrosion with the valve stem.
3 operation:
If the bellows globe valve is opened or closed excessively in use, the valve may not meet the relevant performance requirements. If the valve is excessively closed, the sealing surface may be damaged, resulting in seal failure when the valve is used again. If the valve is opened excessively, the bellows assembly may be operated, causing leakage of the valve.
The cause analysis and improvement of bellows stop valve fault are as follows
After analyzing the existing problems of the valve, its structure, operation and environment were improved. The first is to increase the limit welfare of flat key I, and add a 3mm thick stainless steel packing pad to the lower packing of PTFE material, so as to prevent the packing from getting dirty and limiting the valve stem.
When the valve is closed, if the valve can not be closed, it should not be forced to close, but open the valve, flush it with fluid for a period of time, and then close it again and again. If it still can not be closed, the grinding sealing surface should be checked. When the valve is opened, when the valve is opened to a certain height and the valve stem encounters small resistance, try not to continue to force the valve to open, so as to extend the service life of the valve stem and its sealing components.
When installing the stop valve with thrust ball bearing on the upper part of the valve stem, it is necessary to avoid the condensation water dripping directly on the valve stem and causing the stem corrosion.

Categories:Industry news
Author:
Origin:
Time of issue:2021-07-14 14:18
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Information

The leakage of bellows globe valve is generally divided into internal leakage and external leakage, and there are many reasons for leakage. In general, the liquid medium contains solid impurities to destroy the sealing surface and cause failure. Combined with the analysis of the field application, the main reasons for the leakage of the valve stem are related to the valve structure, working environment and operation mode.
1 Structure:
The valve stem adopts the double sealing structure of bellows and packing. The bellows is welded with the inner ring and outer ring to form the bellows assembly, and then welded with the valve stem and guide body to prevent the medium from leaking out through the valve stem. The valve stem moves up and down from the flat key I until the upper end face of the flat key I contacts the lower end face of the lower packing. As the lower packing is made of PTFE material, if the valve is opened excessively, the flat key I will be embedded in the packing, the valve can no longer be opened and closed, and the bellows assembly will be killed, resulting in medium leakage along the valve stem. The stretching length and compression of the bellows are determined according to the valve stroke. If the stretching or compression exceeds the limit, the bellows may be damaged, resulting in small braided pipe rupture and seal failure. Therefore, it is necessary to increase the opening and closing limit device of the valve, so that the bellows can expand and contract within the design range during the opening and closing process of the valve.
2. Working environment:
The bad working environment of bellows globe valve is also one of the reasons for its failure. Because the bellows globe valve installed in the ship has been working in the salt spray environment for a long time, and there is often condensate dripping on the upper part, which causes the corrosion of the upper thrust ball bearing. In serious cases, it leads to the contact corrosion with the valve stem.
3 operation:
If the bellows globe valve is opened or closed excessively in use, the valve may not meet the relevant performance requirements. If the valve is excessively closed, the sealing surface may be damaged, resulting in seal failure when the valve is used again. If the valve is opened excessively, the bellows assembly may be operated, causing leakage of the valve.
The cause analysis and improvement of bellows stop valve fault are as follows
After analyzing the existing problems of the valve, its structure, operation and environment were improved. The first is to increase the limit welfare of flat key I, and add a 3mm thick stainless steel packing pad to the lower packing of PTFE material, so as to prevent the packing from getting dirty and limiting the valve stem.
When the valve is closed, if the valve can not be closed, it should not be forced to close, but open the valve, flush it with fluid for a period of time, and then close it again and again. If it still can not be closed, the grinding sealing surface should be checked. When the valve is opened, when the valve is opened to a certain height and the valve stem encounters small resistance, try not to continue to force the valve to open, so as to extend the service life of the valve stem and its sealing components.
When installing the stop valve with thrust ball bearing on the upper part of the valve stem, it is necessary to avoid the condensation water dripping directly on the valve stem and causing the stem corrosion.

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Next: What should be paid attention to when using and installing the clip check valve

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Failure analysis and treatment of bellows globe valve

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The leakage of bellows globe valve is generally divided into internal leakage and external leakage, and there are many reasons for leakage. In general, the liquid medium contains solid impurities to destroy the sealing surface and cause failure. Combined with the analysis of the field application, the main reasons for the leakage of the valve stem are related to the valve structure, working environment and operation mode. 1 Structure: The valve stem adopts the double sealing structure of bellows and packing. The bellows is welded with the inner ring and outer ring to form the bellows assembly, and then welded with the valve stem and guide body to prevent the medium from leaking out through the valve stem. The valve stem moves up and down from the flat key I until the upper end face of the flat key I contacts the lower end face of the lower packing. As the lower packing is made of PTFE material, if the valve is opened excessively, the flat key I will be embedded in the packing, the valve can no longer be opened and closed, and the bellows assembly will be killed, resulting in medium leakage along the valve stem. The stretching length and compression of the bellows are determined according to the valve stroke. If the stretching or compression exceeds the limit, the bellows may be damaged, resulting in small braided pipe rupture and seal failure. Therefore, it is necessary to increase the opening and closing limit device of the valve, so that the bellows can expand and contract within the design range during the opening and closing process of the valve. 2. Working environment: The bad working environment of bellows globe valve is also one of the reasons for its failure. Because the bellows globe valve installed in the ship has been working in the salt spray environment for a long time, and there is often condensate dripping on the upper part, which causes the corrosion of the upper thrust ball bearing. In serious cases, it leads to the contact corrosion with the valve stem. 3 operation: If the bellows globe valve is opened or closed excessively in use, the valve may not meet the relevant performance requirements. If the valve is excessively closed, the sealing surface may be damaged, resulting in seal failure when the valve is used again. If the valve is opened excessively, the bellows assembly may be operated, causing leakage of the valve. The cause analysis and improvement of bellows stop valve fault are as follows After analyzing the existing problems of the valve, its structure, operation and environment were improved. The first is to increase the limit welfare of flat key I, and add a 3mm thick stainless steel packing pad to the lower packing of PTFE material, so as to prevent the packing from getting dirty and limiting the valve stem. When the valve is closed, if the valve can not be closed, it should not be forced to close, but open the valve, flush it with fluid for a period of time, and then close it again and again. If it still can not be closed, the grinding sealing surface should be checked. When the valve is opened, when the valve is opened to a certain height and the valve stem encounters small resistance, try not to continue to force the valve to open, so as to extend the service life of the valve stem and its sealing components. When installing the stop valve with thrust ball bearing on the upper part of the valve stem, it is necessary to avoid the condensation water dripping directly on the valve stem and causing the stem corrosion.

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